Patent Application
20080146500
The present invention relates to selective VPAC2 receptor peptide agonists.
In particular, the present invention relates to selective VPAC2 receptor peptide agonists which are covalently attached to one or more molecules of polyethylene glycol or a derivative thereof.
Type 2 diabetes, or non-insulin dependent diabetes mellitus (NIDDM), is the most common form of diabetes, affecting 90% of people with diabetes. With NIDDM, patients have impaired β-cell function resulting in insufficient insulin production and/or decreased insulin sensitivity. If NIDDM is not controlled, excess glucose accumulates in the blood, resulting in hyperglycemia. Over time, more serious complications may arise including renal dysfunction, cardiovascular problems, visual loss, lower limb ulceration, neuropathy, and ischemia. Treatments for NIDDM include improving diet, exercise, and weight control as well as using a variety of oral medications. Individuals with NIDDM can initially control their blood glucose levels by taking such oral medications. These medications, however, do not slow the progressive loss of β-cell function that occurs in type 2 diabetes patients and, thus, are not sufficient to control blood glucose levels in the later stages of the disease. Also, treatment with currently available medications exposes NIDDM patients to potential side effects such as hypoglycemia, gastrointestinal problems, fluid retention, oedebia, and/or weight gain.
Compounds, such as peptides that are selective for a particular G-protein coupled receptor known as the VPAC2 receptor, were initially identified by modifying vasoactive intestinal peptide (VIP) and/or pituitary adenylate cyclase-activating polypeptide (PACAP). (See, for example, Xia et al., J Pharmacol Exp Ther., 281:629-633 (1997); Tsutsumi et al., Diabetes, 51:1453-1460 (2002), WO 01/23420, WO 2004/006839.)
PACAP belongs to the secretin/glucagon/vasoactive intestinal peptide (VIP) family of peptides and works through three G-protein-coupled receptors that exert their action through the cAMP-mediated and other Ca2+-mediated signal transduction pathways. These receptors are known as the PACAP-preferring type 1 (PAC1) receptor (Isobe, et al., Regul. Pept., 110:213-217 (2003); Ogi, et al., Biochem. Biophys. Res. Commun., 196:1511-1521 (1993)) and the two VIP-shared type 2 receptors (VPAC1 and VPAC2) (Sherwood et al., Endocr. Rev., 21:619-670 (2000); Hammar et al., Pharmacol Rev, 50:265-270 (1998); Couvineau, et al., J. Biol. Chem., 278:24759-24766 (2003); Sreedharan, et al., Biochem. Biophys. Res. Commun., 193:546-553 (1993); Lutz, et al., FEBS Lett., 458: 197-203 (1999); Adamou, et al., Biochem. Biophys. Res. Commun., 209: 385-392 (1995)).
PACAP has comparable activities towards all three receptors, whilst VIP selectively activates the two VPAC receptors (Tsutsumi et al., Diabetes, 51:1453-1460 (2002)). Both VIP (Eriksson et al., Peptides, 10: 481-484 (1989)) and PACAP (Filipsson et al., JCEM, 82:3093-3098 (1997)) have been shown to not only stimulate insulin secretion in man when given intravenously but also increase glucagon secretion and hepatic glucose output. As a consequence, PACAP or VIP stimulation generally does not result in a net improvement of glycemia. Activation of multiple receptors by PACAP or VIP also has broad physiological effects on nervous, endocrine, cardiovascular, reproductive, muscular, and immune systems (Gozes et al., Curr. Med. Chem., 6:1019-1034 (1999)). Furthermore, it appears that VIP-induced watery diarrhoea in rats is mediated by only one of the VPAC receptors, VPAC1 (Ito et al., Peptides, 22:1139-1151 (2001); Tsutsumi et al., Diabetes, 51:1453-1460 (2002)). In addition, the VPAC1 and PAC1 receptors are expressed on α-cells and hepatocytes and, thus, are most likely involved in the effects on hepatic glucose output.
Exendin-4 is found in the salivary excretions from the Gila Monster, Heloderma Suspectum, (Eng et al., J Biol. Chem., 267 (11): 7402-7405 (1992)). It is a 39 amino acid peptide, which has glucose dependent insulin secretagogue activity. Particular PEGylated exendin and exendin agonist peptides are described in WO 2000/66629.
Recent studies have shown that peptides selective for the VPAC2 receptor are able to stimulate insulin secretion from the pancreas without gastrointestinal (GI) side effects and without enhancing glucagon release and hepatic glucose output (Tsutsumi et al., Diabetes, 51:1453-1460 (2002)).
Many of the VPAC2 receptor peptide agonists reported to date have, however, less than desirable potency, selectivity, and stability profiles, which could impede their clinical viability. In addition, many of these peptides are not suitable for commercial candidates as a result of stability issues associated with the polypeptides in formulation, as well as issues with the short half-life of these polypeptides in vivo. It has, furthermore, been identified that some VPAC2 receptor peptide agonists are inactivated by dipeptidyl-peptidase (DPP-IV). A short serum half-life could hinder the use of these agonists as therapeutic agents. There is, therefore, a need for new therapies, which overcome the problems associated with current medications for NIDDM.
The present invention seeks to provide improved compounds that are selective for the VPAC2 receptor and which induce insulin secretion from the pancreas only in the presence of high blood glucose levels. The compounds of the present invention are peptides, which are believed to also improve beta cell function. These peptides can have the physiological effect of inducing insulin secretion without GI side effects or a corresponding increase in hepatic glucose output and also generally have enhanced selectivity, potency, and/or in vivo stability of the peptide compared to known VPAC2 receptor peptide agonists.
The present invention also seeks to provide selective VPAC2 receptor peptide agonists, which have reduced clearance and improved in vivo stability. It is desirable that the agonists of the present invention be administered a minimum number of times during a prolonged period of time.
According to a first aspect of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37, Xaa38, or Xaa39 is absent, the next amino acid present downstream is the next amino acid in the peptide agonist sequence,
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the peptide of Formula 10 and wherein the C-terminal extension comprises an amino acid sequence of the formula:
wherein:
provided that at least five of Xaa1 to Xaa13 of the C-terminal extension are present and provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated,
and wherein;
at least one of the Cys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the Lys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the K(W) in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the K(CO(CH2)2SH) in the peptide agonist is covalently attached to a PEG molecule, or the carboxy-terminal amino acid of the peptide agonist is covalently attached to a PEG molecule, or a combination thereof.
Preferably, at least six of Xaa1 to Xaa13 of the C-terminal extension are present. More preferably at least seven, eight, nine, ten, eleven, twelve or all of Xaa1 to Xaa13 of the C-terminal extension are present.
It is preferable that the C-terminal extension has no more than three of any one of the following; Cys, Lys, K(W) or K(CO(CH2)2SH). It is more preferable that the C-terminal extension has no more than two of any of these residues. It is even more preferable that the C-terminal extension has no more than one of any of these residues. If there is only one Cys residue in the C-terminal extension, it is preferred that the Cys residue is at the C-terminus.
Preferably, the VPAC2 receptor peptide agonist comprises a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, or Xaa31 is absent, the next amino acid present downstream is the next amino acid in the peptide agonist sequence,
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the peptide of Formula 12 and wherein the C-terminal extension comprises an amino acid sequence of the formula:
wherein:
provided that at least five of Xaa1 to Xaa13 of the C-terminal extension are present and provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the Lys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the K(CO(CH2)2SH) in the peptide agonist is covalently attached to a PEG molecule, or
the K(W) in the peptide agonist is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid of the peptide agonist is covalently attached to a PEG molecule, or a combination thereof.
Preferably, at least six of Xaa1 to Xaa13 of the C-terminal extension are present. More preferably at least seven, eight, nine, ten, eleven, twelve or all of Xaa1 to Xaa13 of the C-terminal extension are present.
The VPAC2 receptor peptide agonist preferably comprises a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, or Xaa31 is absent, the next amino acid present downstream is the next amino acid in the peptide agonist sequence,
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the peptide of Formula 13 and wherein the C-terminal extension comprises an amino acid sequence of the formula:
wherein:
provided that at least five of Xaa1 to Xaa13 of the C-terminal extension are present and provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the Lys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the K(CO(CH2)2SH) in the peptide agonist is covalently attached to a PEG molecule, or
the K(W) in the peptide agonist is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid of the peptide agonist is covalently attached to a PEG molecule, or a combination thereof.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13(SEQ ID NO: 21) wherein Xaa1 is Asp or Glu, Xaa8 is Asp or Glu, Xaa12 is Arg, hR, Lys, or Orn, Xaa14 is Arg, Gln, Aib, hR, Orn, Cit, Lys, Ala, or Leu, Xaa15 is Lys, Aib, Orn, or Arg, Xaa16 is Gln or Lys, Xaa17 is Val, Leu, Ala, Ile, Lys, or Nle, Xaa20 is Lys, Val, Leu, Aib, Ala, Gln, or Arg, Xaa21 is Lys, Aib, Orn, Ala, Gln, or Arg, Xaa27 is Lys, Orn, hR, or Arg, Xaa28 is Asn, Gln, Lys, hR, Aib, Orn, or Pro and Xaa29 is Lys, Orn, hR, or is absent.
More preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa12 is Arg, hR, or Orn, Xaa14 is Arg, Aib, Gln, Ala, Leu, Lys, or Orn, Xaa15 is Lys or Aib, Xaa17 is Val or Leu, Xaa20 is Lys or Aib, Xaa21 is Lys, Aib, or Gln and Xaa28 is Asn or Gln.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa30 and/or Xaa31 are absent. Alternatively, Xaa29, Xaa30 and Xaa31 are all absent.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO:18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib.
Also preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa20 or Xaa21 is Aib.
More preferably, either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib. It is especially preferred that Xaa15 is Aib and Xaa20 is Aib.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa28 is Gln and Xaa29 is Lys or is absent.
More preferably, Xaa28 is Gln and Xaa29 is Lys or is absent, and either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa12 is hR or Orn, Xaa27 is hR or Orn and Xaa29 is hR or Orn. Alternatively, any one of Xaa12, Xaa27 and Xaa29 may be a PEGylated Lys, Cys, K(CO(CH2)2SH or K(W), whilst all the other two positions have the preferred amino acid substitutions as described.
More preferably, Xaa12 is hR or Orn, Xaa27 is hR or Orn and Xaa29 is hR or Orn, and either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib.
Preferably, the VPAC2 receptor peptide agonist of the present invention comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa15 is Aib, Xaa20 is Aib, and Xaa12, Xaa21, Xaa27 and Xaa28 are all Orn. More preferably, Xaa15 is Aib, Xaa20 is Aib, Xaa12, Xaa21, Xaa27 and Xaa28 are all Orn, Xaa8 is Glu, Xaa9 is Gln and Xaa10 is Tyr(OMe). Alternatively, any one or more of Xaa8, Xaa9, Xaa10, Xaa12, Xaa15, Xaa20, Xaa21, Xaa27 and Xaa28 may be a PEGylated Lys, Cys, K(CO(CH2)2SH) or K(W), whilst all the other positions have the preferred amino acid substitutions as described.
The PEGylated VPAC2 receptor peptide agonist of the invention more preferably comprises a sequence of the formula:
provided that if Xaa29, Xaa30, or Xaa31 is absent, the next amino acid present downstream is the next amino acid in the peptide agonist sequence,
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the peptide of Formula 16 and wherein the C-terminal extension comprises an amino acid sequence of the formula:
wherein:
provided that at least five of Xaa1 to Xaa13 of the C-terminal extension are present and provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the Lys residues in the peptide agonist is covalently attached to a PEG molecule, or
at least one of the K(CO(CH2)2SH) in the peptide agonist is covalently attached to a PEG molecule, or
the K(W) in the peptide agonist is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid of the peptide agonist is covalently attached to a PEG molecule, or a combination thereof.
Preferably, the C-terminal extension of the VPAC2 receptor peptide agonist comprises an amino acid sequence of the formula:
wherein:
provided that at least five of Xaa1 to Xaa11 of the C-terminal extension are present and provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated.
Preferably, at least six of Xaa1 to Xaa11 of the C-terminal extension are present. More preferably at least seven, eight, nine, ten, or all of Xaa1 to Xaa11 of the C-terminal extension are present.
More preferably, the C-terminal extension of the VPAC2 receptor peptide agonist is selected from:
It is especially preferred that the C-terminal extension is GGPSSGAPPPS (SEQ ID NO: 10) or GGPSSGAPPPS-NH2 (SEQ ID NO: 11).
The PEG molecule(s) may be covalently attached to any Lys, Cys, K(W), or K(CO(CH2)2SH) residues at any position in the peptide agonist. In particular, the PEG molecule(s) may be covalently attached to any Lys, Cys, K(W), or K(CO(CH2)2SH) residue at positions 9, 13, 15, 16, 17, 18, 19, 20, 21, 24, 25, 26 and/or 28 of Formula 10, 12, 13, or 16. Alternatively, the PEG molecule(s) may be covalently attached to a residue in the C-terminal extension.
Preferably, there is at least one PEG molecule covalently attached to Xaa25 or any subsequent residue in Formula 10, 12, 13, or 16.
Preferably, there is at least one PEG molecule covalently attached to a residue in the C-terminal extension of the VPAC2 receptor peptide agonist.
Any Lys residue in the VPAC2 receptor peptide agonist may be substituted for a K(W) or a K(CO(CH2)2SH), which may be PEGylated. In addition, any Cys residue in the peptide agonist may be substituted for a modified cysteine residue, for example, hC. The modified Cys residue may be covalently attached to a PEG molecule.
It is preferred that two of the Cys residues are each covalently attached to a PEG molecule or two of the Lys residues are each covalently attached to a PEG molecule. Alternatively, one of the Cys residues may be covalently attached to a PEG molecule or one of the Lys residues may be covalently attached to a PEG molecule.
It is preferred that there is a K(CO(CH2)2SH) is the VPAC2 receptor peptide agonist and that this is PEGylated.
Where there is more than one PEG molecule, there may be a combination of Lys, Cys, K(CO(CH2)2SH), K(W) and carboxy-terminal amino acid PEGylation. For example, if there are two PEG molecules, one may be attached to a Lys residue and one may be attached to a Cys residue.
Preferably, the PEG molecule is branched. Alternatively, the PEG molecule may be linear.
Preferably, the PEG molecule is between 1,000 daltons and 100,000 daltons in molecular weight. More preferably the PEG molecule is selected from 10,000, 20,000, 30,000, 40,000, 50,000 and 60,000 daltons. Even more preferably, it is selected from 20,000, 40,000, or 60,000. Where there are two PEG molecules covalently attached to the peptide agonist of the present invention, each is 1,000 to 40,000 daltons and preferably, they have molecular weights of 20,000 and 20,000 daltons, 10,000 and 30,000 daltons, 30,000 and 30,000 daltons, or 20,000 and 40,000 daltons.
Preferably, the VPAC2 receptor peptide agonist sequence further comprises a histidine residue at the N-terminal extension region of the peptide sequence before Xaa1.
Preferably, the VPAC2 receptor peptide agonist of the present invention further comprises a N-terminal modification at the N-terminus of the peptide agonist wherein the N-terminal modification is selected from:
Preferably, the N-terminal modification is the addition of a group selected from: acetyl, propionyl, butyryl, pentanoyl, hexanoyl, methionine, methionine sulfoxide, 3-phenylpropionyl, phenylacetyl, benzoyl, norleucine, D-histidine, isoleucine, -3-mercaptopropionyl, biotinyl-6-aminohexanoic acid, and —C(═NH)—NH2, and more preferably is the addition of acetyl or hexanoyl. It is especially preferred that the N-terminal modification is the addition of hexanoyl.
It will be appreciated by the person skilled in the art that PEGylated VPAC2 receptor peptide agonists comprising various combinations of peptide sequence according to Formula 10, 12, 13 or 16, C-terminal extensions and N-terminal modifications as described herein, may be made based on the above disclosure.
The following VPAC2 receptor peptide agonists may be PEGylated:
Preferably, the following VPAC2 receptor peptide agonists may be PEGylated:
According to a second aspect of the present invention, the preferred PEGylated VPAC2 receptor peptide agonists comprise an amino acid sequence selected from:
More preferred PEGylated VPAC2 receptor peptide agonists according to the second aspect of the present invention comprise an amino acid sequence selected from:
Even more preferred PEGylated VPAC2 receptor peptide agonists according to the second aspect of the present invention comprise an amino acid sequence selected from:
According to a third aspect of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37,
Preferably, the PEGylated VPAC2 receptor peptide agonist according to the third aspect of the present invention comprises a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37,
and that the peptide agonist comprises at least one amino acid substitution selected from:
According to a fourth aspect of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist of the present invention for use as a medicament.
According to a further aspect of the present invention, there is provided the use of a PEGylated VPAC2 receptor peptide agonist of the present invention for the manufacture of a medicament for the treatment non-insulin-dependent diabetes.
According to yet a further aspect of the present invention, there is provided the use of a PEGylated VPAC2 receptor peptide agonist of the present invention for the manufacture of a medicament for the treatment of insulin-dependent diabetes.
Alternative embodiments of the present invention are described below.
A first alternative embodiment of the present invention is a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37, Xaa38, or Xaa39 is absent, the next amino acid present downstream is the next amino acid in the sequence;
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the sequence and wherein the C-terminal extension comprises an amino acid sequence selected from the group consisting of:
wherein:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated;
wherein:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated; and
wherein:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues is covalently attached to a PEG molecule, or
at least one of the Lys residues is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid is covalently attached to a PEG molecule, or any combination thereof.
Preferably, an alternative selective VPAC2 receptor peptide agonist of the present invention has the amino acid sequence of Formula 4 (SEQ ID NO: 7), modified so that from one, two, three, four, five, six, seven, eight, nine, or ten amino acids differ from the amino acid in the corresponding position of SEQ ID NO: 1.
Another alternative embodiment of the present invention is a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that if Xaa29 is absent then Xaa30 and Xaa31 are also absent and if Xaa30 is absent then Xaa31 is absent;
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the sequence and wherein the C-terminal extension comprises an amino acid sequence of the Formula 7 (SEQ ID NO: 15);
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 7 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues is covalently attached to a PEG molecule, or
at least one of the Lys residues is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid is covalently attached to a PEG molecule, or any combination thereof.
Preferably, an alternative selective VPAC2 receptor peptide agonist of the present invention has the amino acid sequence of Formula 2 (SEQ ID NO: 5), modified so that from one, two, three, four, five, six, seven, eight, nine, or ten amino acids differ from the amino acid in the corresponding position of SEQ ID NO: 1.
Yet another alternative embodiment of the present invention is a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37, Xaa38, or Xaa39 is absent, the next amino acid present downstream is the next amino acid in the sequence;
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the sequence and wherein the C-terminal extension comprises an amino acid sequence selected from the group consisting of:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9 or Xaa10 of Formula 7 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated;
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 of Formula 5 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated; and
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 6 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues is covalently attached to a PEG molecule, or
at least one of the Lys residues is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid is covalently attached to a PEG molecule, or any combination thereof.
For example, if Xaa29 of the peptide sequence is Gly and Xaa30 is absent, the next amino acid bonded to Gly at position 29 is an amino acid listed for position 31 or, if position 31 is also absent, an amino acid listed for position 32 is bonded to Gly at position 29, and so forth. Additionally, for example, if Xaa29 is Gly and Xaa30 through Xaa40 are absent, Gly may be the C-terminal amino acid and may be amidated.
Preferably, an alternative selective VPAC2 receptor peptide agonist of the present invention has the amino acid sequence of Formula 3 (SEQ ID NO: 6), modified so that from one, two, three, four, five, six, seven, eight, nine, or ten amino acids differ from the amino acid in the corresponding position of SEQ ID NO: 1.
Another alternative embodiment of the present invention is a PEGylated VPAC2 receptor peptide agonist comprising a sequence of the formula:
wherein:
provided that at least one Xaa selected from the group consisting of: Xaa2, Xaa14, Xaa15, Xaa16, Xaa17, Xaa20, Xaa25, Xaa26, Xaa27, and Xaa31 is an amino acid that differs from the amino acid at the corresponding position in SEQ ID NO: 1,
provided that if Xaa29 is absent then Xaa30 and Xaa31 are also absent, and if Xaa30 is absent then Xaa31 is also absent;
and a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the sequence and wherein the C-terminal extension comprises an amino acid sequence selected from the group consisting of:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, Xaa12, or Xaa13 of Formula 5 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated; and
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 6 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated,
and wherein:
at least one of the Cys residues is covalently attached to a PEG molecule, or
at least one of the Lys residues is covalently attached to a PEG molecule, or
the carboxy-terminal amino acid is covalently attached to a PEG molecule, or any combination thereof.
Preferably, an alternative selective VPAC2 receptor peptide agonist of the present invention has the amino acid sequence of Formula 1 (SEQ ID NO: 4), modified so that from one, two, three, four, five, six, seven, eight, nine, or ten amino acids differ from the amino acid in the corresponding position of SEQ ID NO: 1.
A further alternative embodiment of the present invention is a VPAC2 receptor peptide agonist comprising a sequence of the Formula 1 (SEQ ID NO: 4), wherein the sequence has at least one amino acid substitution selected from the group consisting of:
Xaa2 is: Val or dA;
Xaa14 is: Leu;
Xaa15 is: Ala;
Xaa16 is: Lys;
Xaa17 is: Ala;
Xaa20 is: Gln;
Xaa25 is: Phe, Ile, Leu, Val, Trp, or Tyr;
Xaa26 is: Thr, Trp, or Tyr;
Xaa27 is: hR; and
Xaa31 is: Phe,
and provided that if Xaa29 is absent then Xaa30 and Xaa31 are also absent and if Xaa30 is absent then Xaa31 is absent.
The peptide of Formula 1 (SEQ ID NO: 4) can further comprise a C-terminal extension wherein the N-terminus of the C-terminal extension is linked to the C-terminus of the peptide of Formula 1 (SEQ ID NO: 4) and wherein the C-terminal extension comprises an amino acid sequence selected from the group consisting of:
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 of Formula 5 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated; and
provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 6 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated.
Additional alternative embodiments of the present invention include a VPAC2 receptor peptide agonist further comprising a N-terminal modification linked to the N-terminus of the peptide sequence wherein the N-terminal modification involves acylation, alkylation, acetylation, a carbobenzoyl group, a succinimide group, a sulfonamide group, a carbamate group, or a urea group. N-terminal modification includes, but is not limited to eighteen carbons (C-18), ten carbons (C-10), and six carbons (C-6). N-terminal modification also includes HS(CH2)2CO.
Other alternative embodiments of the present invention include a VPAC2 receptor peptide agonist further comprising a N-terminal modification linked to the N-terminus of the peptide sequence wherein the N-terminal modification is selected from the group consisting of D-histidine and isoleucine.
Alternative embodiments of the present invention also include a VPAC2 receptor peptide agonist further comprising a N-terminal modification linked to the N-terminus of the peptide sequence wherein the N-terminal modification is selected from the group consisting of acetyl, propionyl, butyryl, pentanoyl, hexanoyl, Met, 3-phenylpropionyl, phenylacetyl, benzoyl, and norleucine.
The VPAC2 receptor peptide agonists of the present invention, therefore, have the advantage that they have enhanced selectivity, potency and/or stability over known VPAC2 receptor peptide agonists. In particular, the addition of the extension sequence of exendin-4 as the c-capping sequence surprisingly increased the VPAC2 receptor selectivity as well as increasing proteolytic stability. The covalent attachment of one or more molecules of PEG to particular residues of a VPAC2 receptor peptide agonist results in a biologically active, PEGylated VPAC2 receptor peptide agonist with an extended half-life and reduced clearance when compared to that of non-PEGylated VPAC2 receptor peptide agonists.
A “selective VPAC2 receptor peptide agonist” of the present invention is a peptide that selectively activates the VPAC2 receptor to induce insulin secretion. Preferably, the sequence for a selective VPAC2 receptor peptide agonist of the present invention has from about twenty-eight to about thirty-five naturally occurring and/or non-naturally occurring amino acids and may or may not additionally comprise a C-terminal extension. More preferably, the selective VPAC2 receptor peptide agonist has from twenty-eight to thirty-one naturally occurring and/or non-naturally occurring amino acids and may or may not additionally comprise a C-terminal extension.
A “selective PEGylated VPAC2 receptor peptide agonist” is a selective VPAC2 receptor peptide agonist covalently attached to one or more molecules of polyethylene glycol (PEG), or a derivative thereof, wherein each PEG is attached to a cysteine or lysine amino acid, to a K(W) or K(CO(CH2)2SH), or to the carboxy terminus of a peptide.
Selective PEGylated VPAC2 receptor peptide agonists may have a C-terminal extension. The “C-terminal extension” of the present invention comprises a sequence having from one to thirteen naturally occurring or non-naturally occurring amino acids linked to the C-terminus of the sequence of Formula 10, 12, 13 or 16 at the N-terminus of the C-terminal extension via a peptide bond. Any one of the Cys, Lys, K(W), or K(CO(CH2)2SH) residues in the C-terminal extension can be covalently attached to a PEG molecule, or the carboxy-terminal amino acid of the C-terminal extension can be covalently attached to a PEG molecule.
As used herein, the term “linked to” with reference to the term C-terminal extension, includes the addition or attachment of amino acids or chemical groups directly to the C-terminus of the peptide of the Formula 10, 12, 13, or 16.
Optionally, the selective PEGylated VPAC2 receptor peptide agonist may also have an N-terminus modification. The term “N-terminal modification” as used herein includes the addition or attachment of amino acids or chemical groups directly to the N-terminal of a peptide and the formation of chemical groups, which incorporate the nitrogen at the N-terminus of a peptide.
The N-terminal modification may comprise the addition of one or more naturally occurring or non-naturally occurring amino acids to the VPAC2 receptor peptide agonist sequence, preferably there are not more than ten amino acids, with one amino acid being more preferred. Naturally occurring amino acids which may be added to the N-terminus include methionine and isoleucine. A modified amino acid added to the N-terminus may be D-histidine. Alternatively, the following amino acids may be added to the N-terminus: (SEQ ID NO: 14) Ser-Trp-Cys-Glu-Pro-Gly-Trp-Cys-Arg, wherein the Arg is linked to the N-terminus of the peptide agonist. Preferably, any amino acids added to the N-terminus are linked to the N-terminus by a peptide bond.
The term “linked to” as used herein, with reference to the term N-terminal modification, includes the addition or attachment of amino acids or chemical groups directly to the N-terminus of the PEGylated VPAC2 receptor agonist. The addition of the above N-terminal modifications may be achieved under normal coupling conditions for peptide bond formation.
The N-terminus of the peptide agonist may also be modified by the addition of an alkyl group (R), preferably a C1-C16 alkyl group, to form (R)NH—.
Alternatively, the N-terminus of the peptide agonist may be modified by the addition of a group of the formula —C(O)R1 to form an amide of the formula R1C(O)NH—. The addition of a group of the formula —C(O)R1 may be achieved by reaction with an organic acid of the formula R1COOH. Modification of the N-terminus of an amino acid sequence using acylation is demonstrated in the art (e.g. Gozes et al., J. Pharmacol Exp Ther, 273:161-167 (1995)). Addition of a group of the formula —C(O)R1 may result in the formation of a urea group (see WO 01/23240, WO 2004/006839) or a carbamate group at the N-terminus. Also, the N-terminus may be modified by the addition of pyroglutamic acid or 6-aminohexanoic acid.
The N-terminus of the peptide agonist may be modified by the addition of a group of the formula —SO2R5, to form a sulfonamide group at the N-terminus.
The N-terminus of the peptide agonist may also be modified by reacting with succinic anhydride to form a succinimide group at the N-terminus. The succinimide group incorporates the nitrogen at the N-terminus of the peptide.
The N-terminus may alternatively be modified by the addition of methionine sulfoxide, biotinyl-6-aminohexanoic acid, or —C(═NH)—NH2. The addition of —C(═ONNH)—NH2 is a guanidation modification, where the terminal NH2 of the N-terminal amino acid becomes —NH—C(═NH)—NH2.
Most of the sequences of the present invention, including the N-terminal modifications and the C-terminal extensions contain the standard single letter or three letter codes for the twenty naturally occurring amino acids. The other codes used are defined as follows:
The term “VPAC2” is used to refer to and in conjunction with the particular receptor (Lutz, et al., FEBS Lett., 458: 197-203 (1999); Adamou, et al., Biochem. Biophys. Res. Commun., 209: 385-392 (1995)) that the agonists of the present invention activate. This term also is used to refer to and in conjunction with the agonists of the present invention.
VIP naturally occurs as a single sequence having 28 amino acids. However, PACAP exists as either a 38 amino acid peptide (PACAP-38) or as a 27 amino acid peptide (PACAP-27) with an amidated carboxyl (Miyata, et al., Biochein Biophys Res Commun, 170:643-648 (1990)). The sequences for VIP, PACAP-27, and PACAP-38 are as follows
The term “naturally occurring amino acid” as used herein means the twenty amino acids coded for by the human genetic code (i.e. the twenty standard amino acids). These twenty amino acids are: Alanine, Arginine, Asparagine, Aspartic Acid, Cysteine, Glutamine, Glutamic Acid, Glycine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Proline, Serine, Threonine, Tryptophan, Tyrosine and Valine.
Examples of “non-naturally occurring amino acids” include both synthetic amino acids and those modified by the body. These include D-amino acids, arginine-like amino acids (e.g., homoarginine), and other amino acids having an extra methylene in the side chain (“homo” amino acids), and modified amino acids (e.g norleucine, lysine (isopropyl)—wherein the side chain amine of lysine is modified by an isopropyl group). Also included are amino acids such as ornithine and amino isobutyric acid.
“Selective” as used herein refers to a VPAC2 receptor peptide agonist with increased selectivity for the VPAC2 receptor compared to other known receptors. The degree of selectivity is determined by a ratio of VPAC2 receptor binding affinity to VPAC1 receptor binding affinity and by a ratio of VPAC2 receptor binding affinity to PAC1 receptor binding affinity. Preferably, the agonists of the present invention have a selectivity ratio where the affinity for the VPAC2 receptor is at least 50 times greater than for the VPAC1 and/or for PAC1 receptors. More preferably, the affinity is at least 100 times greater for VPAC2 than for VPAC1 and/or for PAC1. Even more preferably, the affinity is at least 200 times greater for VPAC2 than for VPAC1 and/or for PAC1. Still more preferably, the affinity is at least 500 times greater for VPAC2 than for VPAC1 and/or for PAC1. Yet more preferably, the affinity is at least 1000 times greater for VPAC2 than for VPAC1 and/or for PAC1. Binding affinity is determined as described below in Example 4.
“Percent (%) sequence identity” as used herein is used to denote sequences which when aligned have similar (identical or conservatively replaced) amino acids in like positions or regions, where identical or conservatively replaced amino acids are those which do not alter the activity or function of the protein as compared to the starting protein. For example, two amino acid sequences with at least 85% identity to each other have at least 85% similar (identical or conservatively replaced residues) in a like position when aligned optimally allowing for up to 3 gaps, with the proviso that in respect of the gaps a total of not more than 15 amino acid residues is affected. Percent sequence identity may be calculated by determining the number of residues that differ between a peptide encompassed by the present invention and a reference peptide such as P83 (SEQ ID NO: 83), taking that number and dividing it by the number of amino acids in the reference peptide (e.g. 39 amino acids for P83), multiplying the result by 100, and subtracting that resulting number from 100. For example, a sequence having 39 amino acids with four amino acids that are different from P83 would have a percent (%) sequence identity of 90% (e.g. 100˜((4/39)×100)). For a sequence that is longer than 39 amino acids, the number of residues that differ from the P83 sequence will include the additional amino acids over 39 for purposes of the aforementioned calculation. For example, a sequence having 41 amino acids, with four amino acids different from the 39 amino acids in the P83 sequence and with two additional amino acids at the carboxy terminus which are not present in the P83 sequence, would have a total of six amino acids that differ from P83. Thus, this sequence would have a percent (%) sequence identity of 84% (e.g. 100−((6/39)×100)). The degree of sequence identity may be determined using methods well known in the art (see, for example, Wilbur, W. J. and Lipman, D. J., Proc. Natl. Acad. Sci. USA 80:726-730 (1983) and Myers E. and Miller W., Comput. Appl. Biosci. 4:11-17 (1988)). One program which may be used in determining the degree of similarity is the MegAlign Lipman-Pearson one pair method (using default parameters) which can be obtained from DNAstar Inc, 1128, Selfpark Street, Madison, Wis., 53715, USA as part of the Lasergene system. Another program, which may be used, is Clustal W. This is a multiple sequence alignment package developed by Thompson et al (Nucleic Acids Research, 22(22):4673-4680 (1994)) for DNA or protein sequences. This tool is useful for performing cross-species comparisons of related sequences and viewing sequence conservation. Clustal W is a general purpose multiple sequence alignment program for DNA or proteins. It produces biologically meaningful multiple sequence alignments of divergent sequences. It calculates the best match for the selected sequences, and lines them up so that the identities, similarities and differences can be seen. Evolutionary relationships can be seen via viewing Cladograms or Phylograms.
The sequence for a selective PEGylated VPAC2 receptor peptide agonist of the present invention is selective for the VPAC2 receptor and preferably has a sequence identity in the range of 60% to 70%, 60% to 65%, 65% to 70%, 70% to 80%, 70% to 75%, 75% to 80%, 80% to 90%, 80% to 85%, 85% to 90%, 90% to 97%, 90% to 95%, or 95% to 97%, with P83 (SEQ ID NO: 83). Preferably, the sequence has a sequence identity of greater than 71% with P83 (SEQ ID NO: 83). More preferably, the sequence has greater than 74% sequence identity with P83 (SEQ ID NO: 83). Even more preferably, the sequence has greater than 76% sequence identity with P83 (SEQ ID NO: 83). Yet more preferably, the sequence has greater than 79% sequence identity or 84% sequence identity with P83 (SEQ ID NO: 83).
The term “C1-C16 alkyl” as used herein means a monovalent saturated straight, branched or cyclic chain hydrocarbon radical having from 1 to 16 carbon atoms. Thus the term “C1-C16 alkyl” includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-heptyl, n-octyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The C1-C16 alkyl group may be optionally substituted with one or more substituents.
The term “C1-C6 alkyl” as used herein means a monovalent saturated straight, branched or cyclic chain hydrocarbon radical having from 1 to 6 carbon atoms. Thus the term “C1-C6 alkyl” includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. The C1-C6 alkyl group may be optionally substituted with one or more substituents.
The term “C2-C6 alkenyl” as used herein means a monovalent straight, branched or cyclic chain hydrocarbon radical having at least one double bond and having from 2 to 6 carbon atoms. Thus the term “C2-C6 alkenyl” includes vinyl, prop-2-enyl, but-3-enyl, pent-4-enyl and isopropenyl. The C2-C6 alkenyl group may be optionally substituted with one or more substituents.
The term “C2-C6 alkynyl” as used herein means a monovalent straight or branched chain hydrocarbon radical having at least one triple bond and having from 2 to 6 carbon atoms. Thus the term “C2-C6 alkynyl” includes prop-2-ynyl, but-3-ynyl and pent-4-ynyl. The C2-C6 alkynyl may be optionally substituted with one or more substituents.
The term “halo” or “halogen” means fluorine, chlorine, bromine or iodine.
The term “aryl” when used alone or as part of a group is a 5 to 10 membered aromatic or heteroaromatic group including a phenyl group, a 5 or 6-membered monocyclic heteroaromatic group, each member of which may be optionally substituted with 1, 2, 3, 4 or 5 substituents (depending upon the number of available substitution positions), a naphthyl group or an 8-, 9- or 10-membered bicyclic heteroaromatic group, each member of which may be optionally substituted with 1, 2, 3, 4, 5 or 6 substituents (depending on the number of available substitution positions). Within this definition of aryl, suitable substitutions include C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, amino, hydroxy, halogen, —SH and CF3.
The term “aryl C1-C4 alkyl” as used herein means a C1-C4 alkyl group substituted with an aryl. Thus the term “aryl C1-C4 alkyl” includes benzyl, 1-phenylethyl (α-methylbenzyl), 2-phenylethyl, 1-naphthalenemethyl or 2-naphthalenemethyl.
The term “naphthyl” includes 1-naphthyl, and 2-naphthyl. 1-naphthyl is preferred.
The term “benzyl” as used herein means a monovalent unsubstituted phenyl radical linked to the point of substitution by a —CH2— group.
The term “5- or 6-membered monocyclic heteroaromatic group” as used herein means a monocyclic aromatic group with a total of 5 or 6 atoms in the ring wherein from 1 to 4 of those atoms are each independently selected from N, O and S. Preferred groups have 1 or 2 atoms in the ring which are each independently selected from N, O and S. Examples of 5-membered monocyclic heteroaromatic groups include pyrrolyl (also called azolyl), furanyl, thienyl, pyrazolyl (also called 1H-pyrazolyl and 1,2-diazolyl), imidazolyl, oxazolyl (also called 1,3-oxazolyl), isoxazolyl (also called 1,2-oxazolyl), thiazolyl (also called 1,3-thiazolyl), isothiazolyl (also called 1,2-thiazolyl), triazolyl, oxadiazolyl, thiadiazolyl, tetrazolyl, oxatriazolyl and thiatriazolyl. Examples of 6-membered monocyclic heteroaromatic groups include pyridinyl, pyrimidyl, pyrazinyl, pyridinyl and triazinyl.
The term “8-, 9- or 10-membered bicyclic heteroaromatic group” as used herein means a fused bicyclic aromatic group with a total of 8, 9 or 10 atoms in the ring system wherein from 1 to 4 of those atoms are each independently selected from N, O and S. Preferred groups have from 1 to 3 atoms in the ring system which are each independently selected from N, O and S. Suitable 8-membered bicyclic heteroaromatic groups include imidazo[2,1-b][1,3]thiazolyl, thieno[3,2-b]thienyl, thieno[2,3-d][1,3]thiazolyl and thieno[2,3-d]imidazolyl. Suitable 9-membered bicyclic heteroaromatic groups include indolyl, isoindolyl, benzofuranyl (also called benzo[b]furanyl), isobenzofuranyl (also called benzo[c]furanyl), benzothienyl (also called benzo[b]thienyl), isobenzothienyl (also called benzo[c]thienyl), indazolyl, benzimidazolyl, 1,3-benzoxazolyl, 1,2-benzisoxazolyl, 2,1-benzisoxazolyl, 1,3-benzothiazolyl, 1,2-benzoisothiazolyl, 2,1-benzoisothiazolyl, benzotriazolyl, 1,2,3-benzoxadiazolyl, 2,1,3-benzoxadiazolyl, 1,2,3-benzothiadiazolyl, 2,1,3-benzothiadiazolyl, thienopyridinyl, purinyl and imidazo[1,2-a]pyridine. Suitable 10-membered bicyclic heteroaromatic groups include quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, quinoxalinyl, 1,5-naphthyridyl, 1,6-naphthyridyl, 1,7-naphthyridyl and 1,8-naphthyridyl.
The term “C1-C6 alkoxy” as used herein means a monovalent unsubstituted saturated straight-chain or branched-chain hydrocarbon radical having from 1 to 6 carbon atoms linked to the point of substitution by a divalent O radical. Thus the term “C1-C6 alkoxy” includes, for example, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy and tert-butoxy. The C1-C6 alkoxy group may be optionally substituted with one or more substituents.
The term “PEG” as used herein means a polyethylene glycol molecule. In its typical form, PEG is a linear polymer with terminal hydroxyl groups and has the formula HO—CH2CH2—(CH2CH2O)n—CH2CH2—OH, where it is from about 8 to about 4000. The terminal hydrogen may be substituted with a protective group such as an alkyl or alkanol group. Preferably, PEG has at least one hydroxy group, more preferably it is a terminal hydroxy group. It is this hydroxy group which is preferably activated to react with the peptide. There are many forms of PEG useful for the present invention. Numerous derivatives of PEG exist in the art and are suitable for use in the invention. (See, e.g., U.S. Pat. Nos. 5,445,090; 5,900,461; 5,932,462; 6,436,386; 6,448,369; 6,437,025; 6,448,369; 6,495,659; 6,515,100 and 6,514,497 and Zalipsky, S. Bioconjugate Chem. 6:150-165, 1995). The PEG molecule covalently attached to VPAC2 receptor peptide agonists in the present invention is not intended to be limited to a particular type. The molecular weight of the PEG molecule is preferably from 500-100,000 daltons and more preferably 10,000, 20,000, 30,000, 40,000, 50,000, or 60,000 daltons and most preferably 20,000 or 40,000 daltons. PEG may be linear or branched and PEGylated VPAC2 receptor peptide agonists of the invention may have one, two or three PEG molecules attached to the peptide. It is more preferable that there be one or two PEG molecules per PEGylated VPAC2 receptor peptide agonist, however, when there is more than one PEG molecule per peptide molecule, it is preferred that there be no more than three. It is further contemplated that both ends of the PEG molecule may be homo- or hetero-functionalized for crosslinking two or more VPAC2 receptor peptide agonists together. Where there are two PEG molecules present, the PEG molecules will preferably be 20,000 dalton PEG molecules. However, PEG molecules having a different molecular weight may be used, for example, one 10,000 dalton PEG molecule and one 30,000 PEG molecule.
In the present invention, a PEG molecule may be covalently attached to a Cys or Lys residue or to the C-terminal residue. The PEG molecule may also be covalently attached to a Trp residue which is coupled to the side chain of a Lys residue (K(W)). Alternatively, a K(CO(CH2)2SH) group may be PEGylated to form K(CO(CH2)2S-PEG). Any Lys residue in the peptide agonist may be substituted for a K(W) or K(CO(CH2)2SH), which may then be PEGylated. In addition, any Cys residue in the peptide agonist may be substituted for a modified cysteine residue, for example, hC. The modified Cys residue may be covalently attached to a PEG molecule.
The term “PEGylation” as used herein means the covalent attachment of one or more PEG molecules as described above to the VPAC2 receptor peptide agonists of the present invention.
“Insulinotropic activity” refers to the ability to stimulate insulin secretion in response to elevated glucose levels, thereby causing glucose uptake by cells and decreased plasma glucose levels. Insulinotropic activity can be assessed by methods known in the art, including using experiments that measure VPAC2 receptor binding activity or receptor activation (e.g. insulin secretion by insulinoma cell lines or islets, intravenous glucose tolerance test (IVGTT)). Intraperitoneal glucose tolerance test (IPGTT), and oral glucose tolerance test (OGTT)). Insulinotropic activity is routinely measured in humans by measuring insulin levels or C-peptide levels. Selective VPAC2 receptor peptide agonists of the present invention have insulinotropic activity.
“In vitro potency” as used herein is the measure of the ability of a peptide to activate the VPAC2 receptor in a cell-based assay. In vitro potency is expressed as the “EC50” which is the effective concentration of compound that results in a 50% of maximum increase in activity in a single dose-response experiment. For the purposes of the present invention, in vitro potency is determined using the Alpha Screen assay. See Example 3 for further details of this assay.
The term “plasma half-life” refers to the time in which half of the relevant molecules circulate in the plasma prior to being cleared. An alternatively used term is “elimination half-life.” The term “extended” or “longer” used in the context of plasma half-life or elimination half-life indicates there is a statistically significant increase in the half-life of a PEGylated VPAC2 receptor peptide agonist relative to that of the reference molecule (e.g., the non-PEGylated form of the peptide or the native peptide) as determined under comparable conditions. Preferably a PEGylated VPAC2 receptor peptide agonist of the present invention has an elimination half-life of at least one hour, more preferably at least 3, 5, 7, 10, 15, 20 or 24 hours and most preferably at least 48 hours. The half-life reported herein is the elimination half-life; it is that which corresponds to the terminal log-linear rate of elimination. The person skilled in the art appreciates that half-life is a derived parameter that changes as a function of both clearance and volume of distribution.
Clearance is the measure of the body's ability to eliminate a drug. As clearance decreases due, for example, to modifications to a drug, half-life would be expected to increase. However, this reciprocal relationship is exact only when there is no change in the volume of distribution. A useful approximate relationship between the terminal log-linear half-life (t1/2), clearance (C), and volume of distribution (V) is given by the equation: t1/2≈0.693 (V/C). Clearance does not indicate how much drug is being removed but, rather, the volume of biological fluid such as blood or plasma that would have to be completely freed of drug to account for the elimination. Clearance is expressed as a volume per unit of time. The PEGylated VPAC2 receptor peptide agonists of the present invention preferably have a clearance value of 200 ml/h/kg or less, more preferably 180, 150, 120, 100, 80, 60 ml/h/kg or less and most preferably 50, 40 or 20 ml/h/kg or less.
According to a preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa3 is Asp or Glu, Xaa8 is Asp or Glu, Xaa12 is Arg, hR, Lys, or Orn, Xaa14 is Arg, Gln, Aib, hR, Orn, Cit, Lys, Ala, or Leu, Xaa15 is Lys, Aib, Orn, or Arg, Xaa16 is Gln or Lys, Xaa17 is Val, Leu, Ala, Ile, Lys, or Nle, Xaa20 is Lys, Val, Leu, Aib, Ala, Gln, or Arg, Xaa21 is Lys, Aib, Orn, Ala, Gln, or Arg, Xaa27 is Lys, Orn, hR, or Arg, Xaa28 is Asn, Gln, Lys, hR, Aib, Pro, or Orn and Xaa29 is Lys, Orn, hR, or absent, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
It is more preferred that the C-terminal extension in this embodiment is selected from: GGPSSGAPPPS (SEQ ID NO: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS-NH2 (SEQ ID NO: 17).
According to another embodiment of the present invention, the PEGylated VPAC2 receptor peptide agonist comprises a sequence of the Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa14 is Leu, Xaa15 is Ala, Xaa16 is Lys, Xaa17 is Leu, and Xaa20 is Gln.
According to another preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa30 and Xaa31 are absent, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
Alternatively, in yet another preferred embodiment of the present invention, the PEGylated VPAC2 receptor peptide agonist comprises an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa29, Xaa30 and Xaa31 are absent, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
It is more preferred that the C-terminal extension in the above embodiments is selected from: GGPSSGAPPPS (SEQ ID: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS—NH2 (SEQ ID NO: 17).
According to another preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib, more preferably Xaa15 is Aib and Xaa20 is Aib, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
According to yet another preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib and Xaa28 is Gln and Xaa29 is Lys or absent, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
In a further preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib and Xaa12 of the peptide sequence is hR or Orn, Xaa27 is hR or Orn and Xaa29 is hR or Orn and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
According to yet another preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa15 is Aib, Xaa20 is Aib, and Xaa12, Xaa21, Xaa27, and Xaa28 are all Orn, and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15). In this embodiment, it is especially preferred that Xaa8 is Glu, Xaa9 is Gln, and Xaa10 is Tyr(OMe).
In another preferred embodiment of the present invention, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 16 (SEQ ID NO: 28) and a C-terminal extension comprising an amino acid sequence of Formula 7 (SEQ ID NO: 15).
In the above preferred embodiments of the present invention, it is especially preferred that the VPAC2 receptor peptide agonist further comprises a N-terminal modification, wherein the N-terminal modification is the addition of a group selected from: acetyl, propionyl, butyryl, pentanoyl, hexanoyl, methionine, methionine sulfoxide, 3-phenylpropionyl, phenylacetyl, benzoyl, norleucine, D-histidine, isoleucine, 3-mercaptopropionyl, biotinyl-6-aminohexanoic acid and —C(═NH)—NH2, and more preferably is the addition of acetyl or hexanoyl.
In a preferred embodiment, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib, more preferably Xaa15 is Aib and Xaa20 is Aib, and a C-terminal extension selected from: GGPSSGAPPPS (SEQ ID NO: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), and GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS-NH2 (SEQ ID NO: 17) and wherein the PEGylated VPAC2 receptor peptide agonist further comprises a N-terminal modification which modification is the addition of hexanoyl or acetyl.
In another preferred embodiment, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib, Xaa28 is Gln and Xaa29 is Lys or absent, and a C-terminal extension selected from: GGPSSGAPPPS (SEQ ID NO: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), and GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS-NH2 (SEQ ID NO: 17), and wherein the PEGylated VPAC2 receptor peptide agonist further comprises a N-terminal modification which modification is the addition of hexanoyl or acetyl.
In yet another preferred embodiment, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein either Xaa14 or Xaa15 is Aib and either Xaa20 or Xaa21 is Aib, Xaa12 is hR or Orn, Xaa27 is hR or Orn and Xaa29 is hR or Orn, and a C-terminal extension selected from: GGPSSGAPPPS (SEQ ID NO: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), and GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS-NH2 (SEQ ID NO: 17) and wherein the VPAC2 receptor peptide agonist further comprises a N-terminal modification which modification is the addition of hexanoyl or acetyl.
In yet further preferred embodiment, there is provided a PEGylated VPAC2 receptor peptide agonist comprising an amino acid sequence of Formula 10 (SEQ ID NO: 18), Formula 12 (SEQ ID NO: 20) or Formula 13 (SEQ ID NO: 21) wherein Xaa15 is Aib, Xaa20 is Aib, Xaa12, Xaa21, Xaa27, and Xaa28 are all Orn, Xaa8 is Glu, Xaa9 is Gln, and Xaa10 is Tyr(OMe), and a C-terminal extension selected from: GGPSSGAPPPS (SEQ ID NO: 10), GGPSSGAPPPS-NH2 (SEQ ID NO: 11), GGPSSGAPPPC (SEQ ID NO: 22), and GGPSSGAPPPC-NH2 (SEQ ID NO: 23), GRPSSGAPPPS (SEQ ID NO: 16) and GRPSSGAPPPS-NH2 (SEQ ID NO: 17) and wherein the VPAC2 receptor peptide agonist further comprises a N-terminal modification which modification is the addition of hexanoyl or acetyl.
In combination with any one of the preferred embodiments described above, it is preferred that there is at least one PEG molecule covalently attached to Xaa25 or any subsequent residue in Formula 10, 12, 13 or 16 and/or there is at least one PEG molecule covalently attached to a residue in the C-terminal extension of the peptide agonist. It is also preferred that one or two of the Cys residues in the peptide agonist are covalently attached to a PEG molecule, or one or two of the Lys residues in the peptide agonist are covalently attached to a PEG molecule.
A preferred alternative sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 1 (SEQ ID NO: 4), provided that if Xaa29 or Xaa30 of Formula 1 is absent each amino acid downstream is absent and wherein the C-terminal amino acid may be amidated.
Throughout this specification, with respect to when an Xaa is absent, the next amino acid present downstream is the next amino acid in the sequence or is also absent. For example, if Xaa29 is Lys and Xaa30 is absent, the next amino acid bonded to Lys at position 29 is an amino acid listed for position 31 or absent, and so forth.
Another alternative preferred sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 1 (SEQ ID NO: 4), wherein: Xaa2 is: Ser, -Val, or dA; Xaa12 is: Arg or Lys; Xaa14 is: Arg, Leu, or Lys; Xaa15 is: Lys, Ala, or Arg; Xaa16 is: Gln, Lys, or Ala; Xaa17 is: Met, Val, Ala, or Leu; Xaa19 is: Val, Ala or Leu; Xaa20 is: Lys, Gln, or Arg; Xaa21 is: Lys or Arg; Xaa24 is: Asn or Gln; Xaa25 is: Ser, Phe, Ile, Leu, Thr, Val, Trp, Gln, Asn, or Tyr; Xaa26 is: Ile, Leu, Thr, Val, Trp, or Tyr; Xaa27 is: Leu, hR, Arg, or Lys; Xaa29 is: Lys, Ser, Arg, or absent; Xaa30 is: Arg, Lys, or absent; and Xaa31 is: Tyr, Phe, or absent.
Another alternative preferred sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 1 (SEQ ID NO: 4), wherein: Xaa2 is: Val or dA; Xaa14 is: Leu; Xaa15 is: Ala; Xaa16 is: Lys; Xaa17 is: Ala; Xaa20 is: Gln; Xaa25 is: Phe, Ile, Leu, Val, Trp, or Tyr; Xaa26 is: Thr, Trp, or Tyr; Xaa27 is: hR; and Xaa31 is: Phe.
Another alternative preferred sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 1 (SEQ ID NO: 4), wherein: Xaa2 is: Ser, Val, or dA; Xaa12 is: Arg, Lys, hR, Orn, or Lys (isopropyl); Xaa14 is: Arg, Leu, or Lys; Xaa15 is: Lys, Ala, or Arg; Xaa16 is:
Gln, Lys, or Ala; Xaa17 is: Met, Val, Ala, or Leu; Xaa18 is: Val, Ala, or Leu; Xaa20 is: Lys, Gln, or Arg; Xaa21 is: Lys or Arg; Xaa24 is: Asn or Gln, Xaa25 is: Ser, Phe, Ile, Leu, Val, Trp, Tyr, Thr, Gln, or Asn; Xaa26 is: Ile, Thr, Trp, Tyr, Leu, or Val; Xaa27 is: Leu, Lys, hR, or Arg; Xaa29 is: Lys, Ser, Arg, hR, or absent; Xaa30 is: Arg, Lys, or absent; and Xaa31 is: Tyr, Phe, or absent.
Yet another alternative preferred sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 1 (SEQ ID NO: 4), wherein: Xaa14 is Leu when Xaa15 is Ala and Xaa16 is Lys. Even more preferably, Xaa14 is Leu when Xaa15 is Ala, Xaa16 is Lys, Xaa17 is Leu, and Xaa20 is Gln.
Another alternative preferred peptide sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 2 (SEQ ID NO: 5), provided that if Xaa29 or Xaa30 of Formula 2 is absent each amino acid downstream is absent and wherein the C-terminal amino acid may be amidated.
Another preferred alternative peptide sequence for selective PEGylated VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 3, (SEQ ID NO: 6), provided that if Xaa29, Xaa30, Xaa31, Xaa32; Xaa33, Xaa34, Xaa35, Xaa36, Xaa37, Xaa38, or Xaa39 of Formula 3 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated.
Preferred alternative peptide sequences for selective PEGylated VPAC2 receptor peptide agonists include:
Another preferred alternative sequence for selective VPAC2 receptor peptide agonists of the present invention comprises an amino acid sequence of the Formula 4 (SEQ ID NO: 7), provided that if Xaa29, Xaa30, Xaa31, Xaa32, Xaa33, Xaa34, Xaa35, Xaa36, Xaa37, Xaa38, or Xaa39 of Formula 4 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated.
Preferably, the C-terminal extension for an alternative embodiment of the present invention comprises an amino acid sequence of the Formula 5 (SEQ ID NO: 8), provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, Xaa10, Xaa11, or Xaa12 of Formula 5 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated. For example, if Xaa1 is Gly and Xaa2 is absent, the next amino acid bonded to Gly at position 1 is an amino acid listed for position 3 or, if position 3 is also absent, an amino acid listed for position 4 is bonded to Gly at position 1, and so forth. Additionally, for example, if Xaa1 is Gly and Xaa2 through Xaa13 are absent, Gly may be the C-terminal amino acid and may be amidated.
Also, the C-terminal extension for an alternative embodiment of the present invention preferably comprises an amino acid sequence of the Formula 6 (SEQ ID NO: 9), provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 6 is absent, the next amino acid present downstream is the next amino acid in the sequence and wherein the C-terminal amino acid may be amidated. For example, if Xaa1 is Gly and Xaa2 is absent, the next amino acid bonded to Gly at position 1 is an amino acid listed for position 3 or, if position 3 is also absent, an amino acid listed for position 4 is bonded to Gly at position 1, and so forth. Additionally, for example, if Xaa1 is Gly and Xaa2 through Xaa11 are absent, Gly may be the C-terminal amino acid and may be amidated.
More preferably, the C-terminal extension of an alternative embodiment of the present invention includes the following sequences:
Preferably, the C-terminal extension differs from SEQ ID NO: 10 or SEQ ID NO: 11 by no more than eight amino acids, still preferably by no more than seven amino acids, yet still preferably by no more than six amino acids, more preferably by no more than five amino acids, even more preferably by no more than four amino acids, still more preferably by no more than three amino acids, yet more preferably by no more than two amino acids, and most preferably by no more than one amino acid.
Another alternative more preferable C-terminal extension of the present invention can also include variants of these sequences, including:
These sequences contain the standard single letter codes for the twenty naturally occurring amino acids. SEQ ID NO: 11 and SEQ ID NO: 12 contain sequences that are amidated at the C-terminus of the sequence.
Preferably, the C-terminal extension differs from SEQ ID NO: 12, or SEQ ID NO: 13 by no more than eight amino acids, still preferably by no more than seven amino acids, yet still preferably by no more than six amino acids, more preferably by no more than five amino acids, even more preferably by no more than four amino acids, still more preferably by no more than three amino acids, yet more preferably by no more than two amino acids, and most preferably by no more than one amino acid.
Another alternative preferred C-terminal extension of the present invention comprises as amino acid sequence of the Formula 7 (SEQ ID NO: 15), provided that if Xaa1, Xaa2, Xaa3, Xaa4, Xaa5, Xaa6, Xaa7, Xaa8, Xaa9, or Xaa10 of Formula 7 is absent, the next amino acid present downstream is the next amino acid in the C-terminal extension and wherein the C-terminal amino acid may be amidated.
Another alternative preferred C-terminal extension of the present invention includes (Lys), or (Glu), wherein n is the number of lysine or glutamic acid residues added to the C-terminus and wherein n can be anywhere from one to eight residues.
The following alternative selective PEGylated VPAC2 receptor peptide agonists are preferred:
PEGylation of proteins may overcome many of the pharmacological and toxicological/immunological problems associated with using peptides or proteins as therapeutics. However, for any individual peptide it is uncertain whether the PEGylated form of the peptide will have significant loss in bioactivity as compared to the unPEGylated form of the peptide.
The bioactivity of PEGylated proteins can be affected by factors such as: i) the size of the PEG molecule; ii) the particular sites of attachment; iii) the degree of modification; iv) adverse coupling conditions; v) whether a linker is used for attachment or whether the polymer is directly attached; vi) generation of harmful co-products; vii) damage inflicted by the activated polymer; or viii) retention of charge. Work performed on the PEGylation of cytokines, for example, shows the effect PEGylation may have. Depending on the coupling reaction used, polymer modification of cytokines has resulted in dramatic reductions in bioactivity. [Francis, G. E., et al., (1998) PEGylation of cytokines and other therapeutic proteins and peptides: the importance of biological optimization of coupling techniques, Intl. J. Hem. 68:1-18]. Maintaining the bioactivity of PEGylated peptides is even more problematic than for proteins. As peptides are smaller than proteins, modification by PEGylation may potentially have a greater effect on bioactivity.
The VPAC2 receptor peptide agonists of the present invention are modified by the covalent attachment of one or more molecules of a polyethylene glycol (PEG) and generally have improved pharmacokinetic profiles due to slower proteolytic degradation and renal clearance. Attachment of PEG molecule(s) (PEGylation) will increase the apparent size of the VPAC2 receptor peptide agonists, thus reducing renal filtration and altering biodistribution. PEGylation can shield antigenic epitopes of the VPAC2 receptor peptide agonists, thus reducing reticuloendothelial clearance and recognition by the immune system and also reducing degradation by proteolytic enzymes, such as DPP-IV.
Covalent attachment of one or more molecules of polyethylene glycol to a small, biologically active VPAC2 receptor peptide agonist poses the risk of adversely affecting the agonist, for example, by destabilising the inherent secondary structure and bioactive conformation and reducing bioactivity, so as to make the agonist unsuitable for use as a therapeutic. The present invention, however, is based on the finding that covalent attachment of one or more molecules of PEG to particular residues of a VPAC2 receptor peptide agonist surprisingly results in a biologically active, PEGylated VPAC2 receptor peptide agonist with an extended half-life and reduced clearance when compared to that of non PEGylated VPAC2 receptor peptide agonists. The compounds of the present invention include selective PEGylated VPAC2 receptor peptide agonists.
In order to determine the potential PEGylation sites in a VPAC2 receptor peptide agonist, serine scanning may be conducted. A Ser residue is substituted at a particular position in the peptide and the Ser-modified peptide is tested for potency and selectivity. If the Ser substitution has minimal impact on potency and the Ser-modified peptide is selective for the VPAC2 receptor, the Ser residue is then substituted for a Cys or Lys residue, which serves as a direct or indirect PEGylation site. Indirect PEGylation of a residue is the PEGylation of a chemical group or residue which is bonded to the PEGylation site residue. Indirect PEGylation of Lys includes PEGylation of K(W) and K(CO(CH2)2SH).
The invention described herein provides VPAC2 receptor peptide agonists covalently attached to one or more molecules of polyethylene glycol (PEG), or a derivative thereof wherein each PEG is attached to a Cys or Lys amino acid, to a K(W) or a K(CO(CH2)2SH), or to the carboxy terminal amino acid of the peptide agonist. PEGylation can enhance the half-life of the selective VPAC2 receptor peptide agonists, resulting in PEGylated VPAC2 receptor peptide agonists with an elimination half-life of at least one hour, preferably at least 3, 5, 7, 10, 15, 20, or 24 hours and most preferably at least 48 hours. The PEGylated VPAC2 receptor peptide agonists of the present invention preferably have a clearance value of 200 ml/h/kg or less, more preferably 180, 150, 130, 100, 80, 60 ml/h/kg or less and most preferably less than 50, 40 or 20 ml/h/kg.
The present invention encompasses the discovery that specific amino acids added to the C-terminus of a peptide sequence for a PEGylated VPAC2 receptor peptide agonist provide features that may protect the peptide as well as may enhance activity, selectivity, and/or potency. For example, these C-terminal extensions may stabilize the helical structure of the peptide and sites within the peptide prone to enzymatic cleavage that are located near the C-terminus. Furthermore, many of the C-terminally extended peptides disclosed herein may be more selective for the VPAC2 receptor and can be more potent than VIP, PACAP, and other known VPAC2 receptor peptide agonists. An example of a preferred C-terminal extension is the extension peptide of exendin-4 as the C-capping sequence. Exendin-4 is found in the salivary excretions from the Gila Monster, Heloderma Suspectum, (Eng et al., J. Biol. Chem., 267(11):7402-7405 (1992)).
It has furthermore been discovered that modification of the N-terminus of the VPAC2 receptor peptide agonist may enhance potency and/or provide stability against DPP-IV cleavage.
VIP and some known VPAC2 receptor peptide agonists are susceptible to cleavage by various enzymes and, thus, have a short in vivo half-life. Various enzymatic cleavage sites in the VPAC2 receptor peptide agonists are discussed below. The cleavage sites are discussed relative to the amino acid positions in VIP (SEQ ID NO: 1), and are applicable to the sequences noted herein.
Cleavage of the peptide agonist by the enzyme dipeptidyl-peptidase-IV (DPP-IV) occurs between position 2 (serine in VIP) and position 3 (aspaitic acid in VIP). The addition of a N-terminal modification and/or various substitutions at position 2 may improve stability against DPP-IV cleavage. Examples of amino acids at position 2 that may improve stability against DPP-IV inactivation preferably include valine, D-alanine, or D-serine. More preferably, position 2 is valine or D-alanine. Examples of N-terminal modifications that may improve stability against DPP-IV inactivation include the addition of acetyl, propionyl, butyryl, pentanoyl, hexanoyl, methionine, methionine sulfoxide, 3-phenylpropionyl, phenylacetyl, benzoyl, norleucine, D-histidine, isoleucine, 3-mercaptopropionyl, biotinyl-6-aminohexanoic acid and —C(═NH)—NH2. Preferably, the N-terminal modification is the addition of acetyl or hexanoyl. There are chymosrypsin cleavage sites in wild-type VIP between the amino acids 10 and 11 (tyrosine and threonine) and those at 22 and 23 (tyrosine and leucine). Making substitutions at position 10 and/or 11 and position 22 and/or 23 may increase the stability of the peptide at these sites.
There is also a trypsin cleavage site between arginine at position 12 and leucine at position 13 of wild-type VIP. Examples of substitutions which render the peptide resistant to cleavage by trypsin at this site include substitution of the arginine at position 12 with ornithine and substitution of leucine at position 13 with amino isobutyric acid.
In wild-type VIP, and in numerous VPAC2 receptor peptide agonists known in the art, there are cleavage sites between the basic amino acids at positions 14 and 15 and between those at positions 20 and 21. The selective VPAC2 receptor agonists of the present invention generally have improved proteolytic stability in vivo due to substitutions in these sites. These substitutions can render the peptide resistant to cleavage by trypsin-like enzymes, including trypsin. Examples of amino acids at position 14 that confer some resistance to cleavage by trypsin-like enzymes alone or in combination with the amino acids specified for position 15 below include glutamine, amino isobutyric acid, homoarginine, ornithine, citrulline, lysine, alanine and leucine. Also, position 14 may be arginine when position 15 is an amino acid other than lysine. Also, position 14 can be arginine when position 15 is lysine, but this specific combination does not address enzymatic cleavage. Examples of amino acids at position 15 that confer some resistance to cleavage by trypsin-like enzymes alone or in combination with amino acids specified above for position 14 include amino isobutyric acid, ornithine and arginine. Also, position 15 may be lysine when position 14 is an amino acid other than arginine. Also, position 15 can be lysine when position 14 is arginine, but this specific combination does not address enzymatic cleavage. Examples of amino acids at position 20 that confer some resistance to cleavage by trypsin-like enzymes alone or in combination with amino acids specified for position 21 include valine, leucine, amino isobutyric acid, alanine, glutamine, and arginine. Also, position 20 may be lysine when position 21 is an amino acid other than lysine. Also, position 20 can be lysine when position 21 is lysine, but this specific combination does not address enzymatic cleavage. An example of an amino acid at position 21 that confers some resistance to cleavage by trypsin-like peptides alone or in combination with amino acids specified for position 20 include amino isobutyric acid, ornithine, alanine, glutamino, or arginine. Also position 21 may be lysine when position 20 is an amino acid other than lysine. Also, position 21 can be lysine when position 20 is lysine, but this specific combination does not address enzymatic cleavage. The improved stability of a representative number of selective PEGylated VPAC2 receptor peptide agonists with resistance to peptidase cleavage and encompassed by the present invention is demonstrated in Example 6.
The bond between the amino acids at positions 25 and 26 of wild-type VIP is susceptible to enzymatic cleavage. This cleavage site can be completely or partially eliminated through substitution of the amino acid at position 25 and/or the amino acid at position 26. Examples of amino acids at position 25 that confer at least some resistance to enzymatic cleavage include phenylalanine, isoleucine, leucine, threonine, valine, tryptophan, glutamine, asparagine, tyrosine, or amino isobutyric acid. Also, position 25 may be serine when position 26 is an amino acid other than isoleucine. Also, position 25 can be serine when position 26 is isoleucine, but this specific combination does not address enzymatic cleavage. Examples of amino acids at position 26 that confer at least some resistance to enzymatic cleavage alone or in combination with the amino acids specified above for position 25 include leucine, threonine, valine, tryptophan, tyrosine, phenylalanine, or amino isobutyric acid. Also, position 26 may be isoleucine when position 25 is an amino acid other than serine. Also, position 26 can be isoleucine when position 25 is serine, but this specific combination does not address enzymatic cleavage.
The region of the VPAC2 receptor peptide agonist encompassing the amino acids at positions 27, 28, 29, 30 and 31 is also susceptible to enzyme cleavage. The addition of a C-terminal extension peptide may render the peptide agonist more stable against neutroendopeptidase (NEP). The addition of the extension peptide may also increase selectivity for the VPAC2 receptor. Trypsin-like enzymes may also attack these positions. If that occurs, the peptide agonist may lose its C-terminal extension with the additional carboxypeptidase activity leading to an inactive form of the peptide.
In addition to selective VPAC2 receptor peptide agonists with resistance to cleavage by various peptidases, the selective PEGylated VPAC2 peptide receptor agonists of the present invention may also encompass peptides with enhanced selectivity for the VPAC2 receptor, increased potency, and/or increased stability compared with some peptides known in the art. Examples of amino acid positions that may affect such properties include positions: 3, 8, 12, 14, 15, 16, 17, 20, 21, 27, 28, and 29 of Formula 10, 12, or 13. For example, the amino acid at position 3 is preferably aspartic acid or glutamic acid; the amino acid at position 8 is preferably aspartic acid or glutamic acid; the amino acid at position 12 is preferably arginine, homoarginine, ornithine, or lysine; the amino acid at position 14 is preferably arginine, glutamine, amino isobutyric acid, homoarginine, ornithine, citrulline, lysine, alanine, or leucine; the amino acid at position 15 is preferably lysine, amino isobutyric acid, ornithine, or arginine; the amino acid at position 16 is preferably glutamine or lysine; the amino acid at position 17 is preferably valine, alanine, leucine, isoleucine, lysine, or norleucine; the amino acid at position 20 is preferably lysine, valine, leucine, amino isobutyric acid, alanine, glutamine, or arginine; the amino acid at position 21 is preferably lysine, amino isobutyric acid, ornithine, alanine, glutamine, or arginine; the amino acid at position 27 is preferably lysine, ornithine, homoarginine, or arginine; the amino acid at position 28 is preferably asparagine, glutamine, lysine, homoarginine, amino isobutyric acid, proline, or ornithine; and, if present, the amino acid at position 29 is preferably lysine, ornithine, or homoarginine. Preferably, these amino acid substitutions may be combined with substitutions at positions that affect the five aforementioned regions susceptible to cleavage by various enzymes.
The increased potency and selectivity for various VPAC2 receptor peptide agonists of the present invention is demonstrated in Examples 3 and 4. For example, Table 1 in Example 3 provides a list of selective PEGylated VPAC2 receptor peptide agonists and their corresponding in vitro potency results. Preferably, the selective PEGylated VPAC2 receptor peptide agonists of the present invention have an EC50 value less than 200 nM. More preferably, the EC50 value is less than 50 nM. Even more preferably, the EC50 value is less than 30 nM. Still more preferably, the EC50 value is less than 10 nM.
Table 2 in Example 4 provides a list of VPAC2 receptor peptide agonists and their corresponding selectivity results for human VPAC2, VPAC1, and PAC1. See Example 4 for further details of these assays. These results are provided as a ratio of VPAC2 binding affinity to VPAC1 binding affinity and as a ratio of VPAC2 binding affinity to PAC1 binding affinity. Preferably, the agonists of the present invention have a selectivity ratio where the affinity for VPAC2 is at least 50 times greater than for VPAC1 and/or for PAC1. More preferably, the affinity is at least 100 times greater than for VPAC1 and/or for PAC1. Even more preferably, the affinity is at least 200 times greater than for VPAC1 and/or for PAC1. Still more preferably, the affinity is at least 500 times greater than for VPAC1 and/or for PAC1. Yet more preferably, the affinity is at least 1000 times greater than for VPAC1 and/or for PAC1.
As used herein, “selective VPAC2 receptor peptide agonists” also include pharmaceutically acceptable salts of the compounds described herein. A selective VPAC2 receptor peptide agonist of this invention can possess a sufficiently acidic, a sufficiently basic, or both functional groups, and accordingly react with any of a number of inorganic bases, and inorganic and organic acids, to form a salt. Acids commonly employed to form acid addition salts are inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, phosphoric acid, and the like, and organic acids such as p-toluenesulfonic acid, methanesulfonic acid, oxalic acid, p-bromophenyl-sulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid, acetic acid, trifluoroacetic acid, and the like. Examples of such salts include the sulfate, pyrosulfate, bisulfate, sulfite, bisulfite, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, chloride, bromide, iodide, acetate, propionate, decanoate, caprylate, acrylate, formate, isobutyrate, caproate, heptanoate, propiolate, oxalate, malonate, succinate, suberate, sebacate, fumarate, maleate, butyne-1,4-dioate, hexyne-1,6-dioate, benzoate, chlorobenzoate, methylbenzoate, dinitrobenzoate, hydroxybenzoate, methoxybenzoate, phthalate, sulfonate, xylenesulfonate, phenylacetate, phenylpropionate, phenylbutyrate, citrate, lactate, gamma-hydroxybutyrate, glycolate, tartrate, methanesulfonate, propanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, mandelate, and the like.
Base addition salts include those derived from inorganic bases, such as ammonium or alkali or alkaline earth metal hydroxides, carbonates, bicarbonates, and the like. Such bases useful in preparing the salts of this invention thus include sodium hydroxide, potassium hydroxide, ammonium hydroxide, potassium carbonate, and the like.
The selective PEGylated VPAC2 receptor peptide agonists of the present invention can be administered parenterally. Parenteral administration can include, for example, systemic administration, such as by intramuscular, intravenous, subcutaneous, intradermal, or intraperitoneal injection. These agonists can be administered to the subject in conjunction with an acceptable pharmaceutical carrier, diluent, or excipient as part of a pharmaceutical composition for treating NIDDM, or the disorders discussed below. The pharmaceutical composition can be a solution or, if administered parenterally, a suspension of the VPAC2 receptor peptide agonist or a suspension of the VPAC2 receptor peptide agonist complexed with a divalent metal cation such as zinc. Suitable pharmaceutical carriers may contain inert ingredients which do not interact with the peptide or peptide derivative. Suitable pharmaceutical carriers for parenteral administration include, for example, sterile water, physiological saline, bacteriostatic saline (saline containing about 0.9% mg/ml benzyl alcohol), phosphate-buffered saline, Hank's solution, Ringer's-lactate and the like. Some examples of suitable excipients include lactose, dextrose, sucrose, trehalose, sorbitol, and mannitol.
Standard pharmaceutical formulation techniques may be employed such as those described in Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa. The selective PEGylated VPAC2 receptor peptide agonists of the present invention may be formulated for administration through the buccal, topical, oral, transdermal, nasal, or pulmonary route.
The PEGylated VPAC2 receptor peptide agonists of the invention may be formulated for administration such that blood plasma levels are maintained in the efficacious range for extended time periods. The main barrier to effective oral peptide drug delivery is poor bioavailability due to degradation of peptides by acids and enzymes, poor absorption through epithelial membranes, and transition of peptides to an insoluble form after exposure to the acidic pH environment in the digestive tract. Oral delivery systems for peptides such as those encompassed by the present invention are known in the art. For example, PEGylated VPAC2 receptor peptide agonists can be encapsulated using microspheres and then delivered orally. For example, PEGylated VPAC2 receptor peptide agonists can be encapsulated into microspheres composed of a commercially available, biocompatible, biodegradable polymer, poly(lactide-co-glycolide)-COOH and olive oil as a filler (see Joseph, et al. Diabetologia 43:1319-1328 (2000)). Other types of microsphere technology is also available commercially such as Medisorb® and Prolease® biodegradable polymers from Alkermas. Medisorb® polymers can be produced with any of the lactide isomers. Lactide:glycolide ratios can be varied between 0:100 and 100:0 allowing for a broad range of polymer properties. This allows for the design of delivery systems and implantable devices with resorption times ranging from weeks to months. Emisphere has also published numerous articles discussing oral delivery technology for peptides and proteins. For example, see WO 95/28838 by Leone-bay et al. which discloses specific carriers comprised of modified amino acids to facilitate absorption.
The selective PEGylated VPAC2 receptor peptide agonists described herein can be used to treat subjects with a wide variety of diseases and conditions. Agonists encompassed by the present invention exert their biological effects by acting at a receptor referred to as the VPAC2 receptor. Subjects with diseases and/or conditions that respond favourably to VPAC2 receptor stimulation or to the administration of VPAC2 receptor peptide agonists can therefore be treated with the VPAC2 agonists of the present invention. These subjects are said to “be in need of treatment with VPAC2 agonists” or “in need of VPAC2 receptor stimulation”.
The selective PEGylated VPAC2 receptor peptide agonists of the present invention may be employed to treat diabetes, including both type 1 and type 2 diabetes (non-insulin dependent diabetes mellitus or NIDDM). Also included are subjects requiring prophylactic treatment with a VPAC2 receptor agonist, e.g., subjects at risk for developing NIDDM. Such treatment may also delay the onset of diabetes and diabetic complications. Additional subjects include those with impaired glucose tolerance or impaired fasting glucose, subjects whose body weight is about 25% above normal body weight for the subject's height and body build, subjects having one or more parents with NIDDM, subjects who have had gestational diabetes, and subjects with metabolic disorders such as those resulting from decreased endogenous insulin secretion. The selective VPAC2 receptor peptide agonists may be used to prevent subjects with impaired glucose tolerance from proceeding to develop type 2 diabetes, prevent pancreatic β-cell deterioration, induce β-cell proliferation, improve β-cell function, activate dormant β-cells, differentiate cells into β-cells, stimulate P-cell replication, and inhibit β-cell apoptosis. Other diseases and conditions that may be treated or prevented using compounds of the invention in methods of the invention include: Maturity-Onset Diabetes of the Young (MODY) (Herman, et al., Diabetes 43:40, 1994); Latent Autoimmune Diabetes Adult (LADA)(Zimmet, et al., Diabetes Med. 11:299, 1994); impaired glucose tolerance (IGT) (Expert Committee on Classification of Diabetes Mellitus, Diabetes Care 22 (Supp. 1):S5, 1999); impaired fasting glucose (IFG) (Charles, et al., Diabetes 40:796, 1991); gestational diabetes (Metzger, Diabetes, 40:197, 1991); metabolic syndrome X, dyslipidemia, hyperglycemia, hyperinsulinemia, hypertriglyceridemia, and insulin resistance.
The selective PEGylated VPAC2 receptor peptide agonists of the invention may also be used in methods of the invention to treat secondary causes of diabetes (Expert Committee on Classification of Diabetes Mellitus, Diabetes Care 22 (Supp. 1):S5, 1999). Such secondary causes include glucocorticoid excess, growth hormone excess, pheochromocytoma, and drug-induced diabetes. Drugs that may induce diabetes include, but are not limited to, pyriminil, nicotinic acid, glucocorticoids, phenyloin, thyroid hormone, β-adrenergic agents, α-interferon and drugs used to treat HIV infection.
The selective PEGylated VPAC2 receptor peptide agonists of the present invention may be effective in the suppression of food intake and the treatment of obesity.
The selective PEGylated VPAC2 receptor peptide agonists of the present invention may also be effective in the prevention or treatment of such disorders as atherosclerotic disease, hyperlipidemia, hypercholesteremia, low HDL levels, hypertension, primary pulmonary hypertension, cardiovascular disease (including atherosclerosis, coronary heart disease, coronary artery disease, and hypertension), cerebrovascular disease and peripheral vessel disease; and for the treatment of lupus, polycystic ovary syndrome, carcinogenesis, and hyperplasia, asthma, male and female reproduction problems, sexual disorders, ulcers, sleep disorders, disorders of lipid and carbohydrate metabolism, circadian dysfunction, growth disorders, disorders of energy homeostasis, immune diseases including autoimmune diseases (e.g., systemic lupus erythematosus), as well as acute and chronic inflammatory diseases, rheumatoid arthritis, and septic shock.
The selective PEGylated VPAC2 receptor peptide agonists of the present invention may also be useful for treating physiological disorders related to, for example, cell differentiation to produce lipid accumulating cells, regulation of insulin sensitivity and blood glucose levels, which are involved in, for example, abnormal pancreatic β-cell function, insulin secreting tumors and/or autoimmune hypoglycemia due to autoantibodies to insulin, autoantibodies to the insulin receptor, or autoantibodies that are stimulatory to pancreatic β-cells, macrophage differentiation which leads to the formation of atherosclerotic plaques, inflammatory response, carcinogenesis, hyperplasia, adipocyte gene expression, adipocyte differentiation, reduction in the pancreatic β-cell mass, insulin secretion, tissue sensitivity to insulin, liposarcoma cell growth, polycystic ovarian disease, chronic anovulation, hyperandrogenism, progesterone production, steroidogenesis, redox potential and oxidative stress in cells, nitric oxide synthase (NOS) production, increased gamma glutamyl transpeptidase, catalase, plasma triglycerides, HDL, and LDL cholesterol levels, and the like.
In addition, the selective VPAC2 receptor peptide agonists of the invention may be used for treatment of asthma (Bolin, et al., Biopolymer 37:57-66 (1995); U.S. Pat. No. 5,677,419; showing that polypeptide R3PO is active in relaxing guinea pig tracheal smooth muscle); hypotension induction (VIP induces hypotension, tachycardia, and facial flushing in asthmatic patients (Morice, et al., Peptides 7:279-280 (1986); Morice, et al., Lancet 2:1225-1227 (1983)); male reproduction problems (Siow, et al., Arch. Androl. 43(1):67-71 (1999)); as an anti-apoptosis/neuroprotective agent (Brenneman, et al., Ann. N.Y. Acad. Sci. 865:207-12 (1998)); cardioprotection during ischemic events (Kalfin, et al., J. Pharmacol. Exp. Ther. 1268(2):952-8 (1994); Das, et al., Ann. N.Y. Acad. Sci. 865:297-308 (1998)), manipulation of the circadian clock and its associated disorders (Hamar, et al., Cell 109:497-508 (2002); Shen, et al., Proc. Natl. Acad. Sci. 97:11575-80, (2000)), and as an anti-ulcer agent (Tuncel, et al., Ann. N.Y. Acad. Sci. 865:309-22, (1998)).
An “effective amount” of a selective PEGylated VPAC2 receptor peptide agonist is the quantity that results in a desired therapeutic and/or prophylactic effect without causing unacceptable side effects when administered to a subject in need of VPAC2 receptor stimulation. A “desired therapeutic effect” includes one or more of the following: 1) an amelioration of the symptom(s) associated with the disease or condition; 2) a delay in the onset of symptoms associated with the disease or condition; 3) increased longevity compared with the absence of the treatment; and 4) greater quality of life compared with the absence of the treatment. For example, an “effective amount” of a VPAC2 agonist for the treatment of NIDDM is the quantity that would result in greater control of blood glucose concentration than in the absence of treatment, thereby resulting in a delay in the onset of diabetic complications such as retinopathy, neuropathy, or kidney disease. An “effective amount” of a selective VPAC2 receptor peptide agonist for the prevention of NIDDM is the quantity that would delay, compared with the absence of treatment, the onset of elevated blood glucose levels that require treatment with anti-hypoglycemic drugs such as sulfonylureas, thiazolidinediones, insulin, and/or bisguanidines.
An “effective amount” of the selective PEGylated VPAC2 receptor peptide agonist administered to a subject will also depend on the type and severity of the disease and on the characteristics of the subject, such as general health, age, sex, body weight and tolerance to drugs. The dose of selective VPAC2 peptide receptor agonist effective to normalize a patient's blood glucose will depend on a number of factors, among which are included, without limitation, the subject's sex, weight and age, the severity of inability to regulate blood glucose, the route of administration and bioavailability, the pharmacokinetic profile of the peptide, the potency, and the formulation.
A typical dose range for the selective PEGylated VPAC2 receptor peptide agonists of the present invention will range from about 1 μg per day to about 5000 μg per day. Preferably, the dose ranges from about 1 μg per day to about 2500 μg per day, more preferably from about 1 μg per day to about 1000 μg per day. Even more preferably, the dose ranges from about 5 μg per day to about 100 μg per day. A further preferred dose range is from about 10 μg per day to about 50 μg per day. Most preferably, the dose is about 20 μg per day.
A “subject” is a mammal, preferably a human, but can also be an animal, e.g., companion animals (e.g., dogs, cats, and the like), farm animals (e.g., cows, sheep, pigs, horses, and the like) and laboratory animals (e.g., rats, mice, guinea pigs, and the like).
The selective VPAC2 receptor peptide agonists of the present invention can be prepared by using standard methods of solid-phase peptide synthesis techniques. Peptide synthesizers are commercially available from, for example, Rainin-PTI Symphony Peptide Synthesizer (Tucson, Ariz.). Reagents for solid phase synthesis are commercially available, for example, from Glycopep (Chicago, Ill.). Solid phase peptide synthesizers can be used according to manufacturers instructions for blocking interfering groups, protecting the amino acid to be reacted, coupling, decoupling, and capping of unreacted amino acids.
Typically, an ic-N-protected amino acid and the N-terminal amino acid on the growing peptide chain on a resin is coupled at room temperature in an inert solvent such as dimethylformamide, N-methylpyrrolidone or methylene chloride in the presence of coupling agents such as dicyclohexylcarbodiimide and 1-hydroxybenzotriazole and a base such as diisopropylethylamine. The α-N-protecting group is removed from the resulting peptide resin using a reagent such as trifluoroacetic acid or piperidine, and the coupling reaction repeated with the next desired N-protected amino acid to be added to the peptide chain. Suitable amine protecting groups are well known in the art and are described, for example, in Green and Wuts, “Protecting Groups in Organic Synthesis”, John Wiley and Sons, 1991. Examples include t-butyloxycarbonyl (tBoc) and fluorenylmethoxycarbonyl (Fmoc).
The selective VPAC2 receptor peptide agonists are also synthesized using standard automated solid-phase synthesis protocols using t-butoxycarbonyl- or fluorenylmethoxycarbonyl-alpha-amino acids with appropriate side-chain protection. After completion of synthesis, peptides are cleaved from the solid-phase support with simultaneous side-chain deprotection using standard hydrogen fluoride methods or trifluoroacetic acid (TFA). Crude peptides are then further purified using Reversed-Phase Chromatography on Vydac C18 columns using acetonitrile gradients in 0.1% trifluoroacetic acid (TFA). To remove acetonitrile, peptides are lyophilized from a solution containing 0.1% TFA, acetonitrile and water. Purity can be verified by analytical reversed phase chromatography. Identity of peptides can be verified by mass spectrometry. Peptides can be solubilized in aqueous buffers at neutral pH.
The peptide agonists of the present invention may also be made by recombinant methods known in the art using both eukaryotic and prokaryotic cellular hosts.
Once a peptide for use in the present invention is prepared and purified, it is modified by covalently linking at least one PEG molecule to Cys or Lys residues, to K(W) or K(CO(CH2)2SH), or to the carboxy-terminal amino acid. A wide variety of methods have been described in the art to produce peptides covalently conjugated to PEG and the specific method used for the present invention is not intended to be limiting (for review article see, Roberts, M. et al. Advanced Drug Delivery Reviews, 54:459-476, 2002).
An example of a PEG molecule which may be used is methoxy-PEG2-MAL-40K, a bifurcated PEG maleimide (Nektar, Huntsville, Ala.). Other examples include, but are not limited to bulk mPEG-SBA-20K (Nelctar) and mPEG2-ALD-40K (Nektar).
Carboxy-terminal attachment of PEG may be attached via enzymatic coupling using recombinant VPAC2 receptor peptide agonist as a precursor or alternative methods known in the art and described, for example, in U.S. Pat. No. 4,343,898 or Intl. J. Pept. & Prot. Res. 43:127-38 (1994).
One method for preparing the PEGylated VPAC2 receptor peptide agonists of the present invention involves the use of PEG-maleimide to directly attach PEG to a thiol group of the peptide. The introduction of a thiol functionality can be achieved by adding or inserting a Cys or hC residue onto or into the peptide at positions described above. A thiol functionality can also be introduced onto the side-chain of the peptide (e.g. acylation of lysine ε-amino group by a thiol-containing acid, such as mercaptopropionic acid). A PEGylation process of the present invention utilizes Michael addition to form a stable thioether linker. The reaction is highly specific and takes place under mild conditions in the presence of other functional groups. PEG maleimide has been used as a reactive polymer for preparing well-defined, bioactive PEG-protein conjugates. It is preferable that the procedure uses a molar excess, preferably from 1 to 10 molar excess, of a thiol-containing VPAC2 receptor peptide agonist relative to PEG maleimide to drive the reaction to completion. The reactions are preferably performed between pH 4.0 and 9.0 at room temperature for 10 minutes to 40 hours. The excess of unPEGylated thiol-containing peptide is readily separated from the PEGylated product by conventional separation methods. The PEGylated VPAC2 receptor peptide agonist is preferably isolated using reverse-phase HPLC or size exclusion chromatography. Specific conditions required for PEGylation of VPAC2 receptor peptide agonists are set forth in Example 7. Cysteine PEGylation may be performed using PEG maleimide or bifurcated PEG maleimide.
An alternative method for preparing the PEGylated VPAC2 receptor peptide agonists of the invention, involves PEGylating a lysine residue using a PEG-succinimidyl derivative. In order to achieve site specific PEGylation, the Lys residues which are not used for PEGylation are substituted for Arg residues.
Another approach for PEGylation is via Pictet Spengler reaction. A Trp residue with its free amine is needed to incorporate the PEG molecule onto a VPAC2 receptor selective peptide. One approach to achieve this is to site specifically introduce a Trp residue onto the amine of a Lys sidechain via an amide bond during the solid phase synthesis (see Example 9).
Various preferred features and embodiments of the present invention will now be described with reference to the following non-limiting examples.
Selective VPAC2 receptor peptide agonists may be prepared using the following method and then PEGylating using one of the methods described in Examples 7, 8 and 9.
Approximately 0.5-0.6 grams (0.38-0.45 mmole) Boc Ser(Bzl)-PAM resin is placed in a standard 60 mL reaction vessel. Double couplings are run on an Applied Biosystems ABI430A peptide synthesizer. The following side-chain protected amino acids (2 mmole cartridges of Boc amino acids) are obtained from Midwest Biotech (Fishers, Ind.) and are used in the synthesis:
Arg-Tosyl (TOS), Asp-δ-cyclohexyl ester (OcHx), Glu-δ-cyclohexyl ester (OcHx), His-benzyloxymethyl(BOM), Lys-2-chlorobenzyloxycarbonyl (2Cl-Z), Ser-O-benzyl ether (OBzl), Thr-O-benzyl ether (OBzl), Trp-formyl (CHO) and Tyr-2-bromobenzyloxycarbonyl (2Br-Z) and Boc Gly PAM resin. Trifluoroacetic acid (TFA), di-isopropylethylamine (DIEA), 0.5 M hydroxybenzotriazole (HOBt) in DMF and 0.5 M dicyclohexylcarbodiimide (DCC) in dichloromethane are purchased from PE-Applied Biosystems (Foster City, Calif.). Dimethylformamide (DMF-Burdick and Jackson) and dichloromethane (DCM-Mallinkrodt) is purchased from Mays Chemical Co. (Indianapolis, Ind.).
Standard double couplings are run using either symmetric anhydride or HOBt esters, both formed using DCC. At the completion of the syntheses, the N-terminal Boc group is removed and the peptidyl resins are treated with 20% piperidine in DMF to deformylate the Trp side chain if Trp is present in the sequence. For the N-terminal acylation, four-fold excess of symmetric anhydride of the corresponding acid is added onto the peptide resin. The symmetric anhydride is prepared by diisopropyicarbodiimde (DIC) activation in DCM. The reaction is allowed to proceed for 4 hours and monitored by ninhydrin test. After washing with DCM, the resins are transferred to a TEFLON reaction vessel and are dried in vacuo.
Cleavages are done by attaching the reaction vessels to a HF (hydrofluoric acid) apparatus (Penninsula Laboratories). 1 mL m-cresol per gram/resin is added and 10 mL HF (purchased from AGA, Indianapolis, Ind.) is condensed into the pre-cooled vessel. 1 mL DMS per gram resin is added when methionine is present. The reactions are stirred one hour in an ice bath. The HF is removed in vacuo. The residues are suspended in ethyl ether. The solids are filtered and are washed with ether. Each peptide is extracted into aqueous acetic acid and either is freeze dried or is loaded directly onto a reverse-phase column.
Purifications are run on a 2.2×25 cm VYDAC C18 column in buffer A (0.1% Trifluoroacteic acid in water, B: 0.1% TFA in acetonitrile). A gradient of 20% to 90% B is run on an HPLC (Waters) over 120 minutes at 10 mL/minute while monitoring the UV at 280 nm (4.0 A) and collecting one minute fractions. Appropriate fractions are combined, frozen and lyophilized. Dried products are analyzed by HPLC (0.46×15 cm METASIL AQ C18) and MALDI mass spectrometry.
Selective VPAC2 receptor peptide agonists may be prepared using the following method and then PEGylating using one of the methods described in Examples 7, 8 and 9.
Approximately 114 mg (50 mMole) FMOC Ser(tBu) WANG resin (purchased from GlycoPep, Chicago, Ill.) is placed in each reaction vessel. The synthesis is conducted on a Rainin Symphony Peptide Synthesizer. Analogs with a C-terminal amide are prepared using 75 mg (50 μmole) Rink Amide AM resin (Rapp Polymere. Tuebingen, Germany).
The following FMOC amino acids are purchased from GlycoPep (Chicago, Ill.), and NovaBiochem (La Jolla, Calif.): Arg-2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf). Asn-trityl (Trt), Asp-B-t-Butyl ester (tBu), Glu-ε-t-butyl ester (tBu), Glu trityl (Trt), His-trityl (Trt), Lys-t-butyloxycarbonyl (Boc), Ser-t-butyl ether (OtBu), Thr-t-butyl ether (OtBu), Trp-t-butyloxycarbonyl (Boc), Tyr-t-butyl ether (OtBu).
Solvents dimethylformamide (DMF-Burdick and Jackson), N-methylpyrrolidone (NMP-Burdick and Jackson), dichloromethane (DCM-Mallinkrodt) are purchased from Mays Chemical Co. (Indianapolis, Ind.).
Hydroxybenzotrizole (HOBt), di-isopropylcarbodiimde (DIC), di-isopropylethylamine (DIEA), and piperidine (Pip) are purchased from Aldrich Chemical Co (Milwaukee, Wis.).
All amino acids are dissolved in 0.3 M in DMF. Three hour DIC/HOBt activated couplings are run after 20 minutes deprotection using 20% Piperidine/DMF. Each resin is washed with DMF after deprotections and couplings. After the last coupling and deprotection, the peptidyl resins are washed with DCM and are dried in vacuo in the reaction vessel. For the N-terminal acylation, four-fold excess of symmetric anhydride of the corresponding acid is added onto the peptide resin. The symmetric anhydride is prepared by diisopropylcarbodiimde (DIC) activation in DCM. The reaction is allowed to proceed for 4 hours and monitored by ninhydrin test. The peptide resin is then washed with DCM and dried in vacuo.
The cleavage reaction is mixed for 2 hours with a cleavage cocktail consisting of 0.2 mL thioanisole, 0.2 mL methanol, 0.4 mL triisopropylsilane, per 10 mL trifluoroacetic acid (TFA), all purchased from Aldrich Chemical Co., Milwaukee, Wis. If Cys is present in the sequence, 2% of ethanedithiol is added. The TFA filtrates are added to 40 mL ethyl ether. The precipitants are centrifuged 2 minutes at 2000 rpm. The supernatants are decanted. The pellets are resuspended in 40 mL ether, re-centrifuged, re-decanted, dried under nitrogen and then in vacuo.
0.3-0.6 mg of each product is dissolved in 1 mL 0.1% TFA/acetonitrile(ACN), with 20 μL being analyzed on HPLC [0.46×15 cm METASIL AQ C18, 1 mL/min, 45 C.°, 214 nM (0.2 A), A=0.1% TFA, B=0.1% TFA/50% ACN. Gradient=50% B to 90% B over 30 minutes].
Purifications are run on a 2.2×25 cm VYDAC C18 column in buffer A (0.1% trifluoroacteic acid in water, B: 0.1% TFA in acetonitrile). A gradient of 20% to 90% B is on an HPLC (Waters) over 120 minutes at 10 mL/minute while monitoring the UV at 280 nm (4.0 A) and collecting 1 minute fractions. Appropriate fractions are combined, frozen and lyophilized. Dried products are analyzed by HPLC (0.46×15 cm METASIL AQ C18) and MALDI mass spectrometry.
Alpha screen: Cells are washed in the culture flask once with PBS. The cells are then rinsed with enzyme free dissociation buffer. The dissociated cells are removed. The cells are then spun down and washed in stimulation buffer. For each data point, 50,000 cells suspended in stimulation buffer are used. To this buffer, Alpha screen acceptor beads are added along with the stimuli. This mixture is incubated for 60 minutes. Lysis buffer and Alpha screen donor beads are added and are incubated for 60 to 120 minutes. The Alpha screen signal (indicative of intracellular cAMP levels) is read in a suitable instrument (e.g. AlphaQuest from Perkin-Elmer). Steps including Alpha screen donor and acceptor beads are performed in reduced light. The EC50 for cAMP generation is calculated from the raw signal or is based on absolute cAMP levels as determined by a standard curve performed on each plate.
Results for each agonist are, at minimum, from two analyses performed in a single run. For some agonists, the results are the mean of more than one run. The tested peptide concentrations are: 10000, 1000, 100, 10, 3, 1, 0.1, 0.01, 0.003, 0.001, 0.0001 and 0.00001 nM.
The activity (EC50 (nM)) for the human VPAC2 receptor is reported in Table 1.
Binding assays: Membrane prepared from a stable VPAC2 cell line (see Example 3) or from cells transiently transfected with human VPAC1 or PAC1 are used. A filter binding assay is performed using 125I-labeled VIP for VPAC1 and VPAC2 and 125I-labeled PACAP-27 for PAC1 as the tracers.
For this assay, the solutions and equipment include:
Presoak solution: 0.5% Polyethyleneamine in Aqua dest.
Buffer for flushing filter plates: 25 mM HEPES pH 7.4
Blocking buffer: 25 mM HEPES pH 7.4; 0.2% protease free BSA
Assay buffer: 25 mM HEPES pH 7.4; 0.5% protease free BSA
Dilution and assay plate: PS-Microplate, U form
Filtration Plate Multiscreen FB Opaque Plate; 1.0 μM Type B Glasfiber filter
In order to prepare the filter plates, the presoak solution is aspirated by vacuum filtration. The plates are flushed twice with 200 μL flush buffer. 200 μL blocking buffer is added to the filter plate. The filter plate is then incubated with 200 μL presoak solution for 1 hour at room temperature.
The assay plate is filled with 25 mL assay buffer, 25 mL membranes (2.5 μg) suspended in assay buffer, 25 μL compound (agonist) in assay buffer, and 25 μL tracer (about 40000 cpm) in assay buffer. The filled plate is incubated for 1 hour with shaking.
The transfer from assay plate to filter plate is conducted. The blocking buffer is aspirated by vacuum filtration and washed two times with flush buffer. 90 μL is transferred from the assay plate to the filter plate. The 90 μL transferred from assay plate is aspirated and washed three times with 200 μL flush buffer. The plastic support is removed. It is dried for 1 hour at 60° C. 30 μL Microscint is added. The count is performed.
The selectivity (IC50) for human VPAC2, VPAC1, and PAC1 is reported in Table 2. Values reported are single results or the mean of two or more independent runs.
Rat receptor selectivity is estimated by comparing functional potency (cAMP generation) in CHO-PO cells transiently expressing rat VPAC1 or rat VPAC2 receptors. CHO-PO cells transiently expressing rat VPAC1 or VPAC2, are seeded with 10,000 cells/well three days before the assay. The cells are kept in 200 μL culture medium. On the day of the experiment, the medium is removed and the cells are washed twice. The cells are incubated in assay buffer plus IBMX for 15 minutes at room temperature. Afterwards, the stimuli are added and are dissolved in assay buffer. The stimuli are present for 30 minutes. The assay buffer is then gently removed. The cell lysis reagent of the DiscoveRx cAMP kit is added. Thereafter, the standard protocol for developing the cAMP signal as described by the manufacturer is used (DiscoveRx Inc., USA). EC50 values for cAMP generation are calculated from the raw signal or are based on absolute cAMP levels as determined by a standard curve performed on each plate.
Results for each agonist are the mean of two independent runs. The typically tested concentrations of peptide are: 1000, 300, 100, 10, 1, 0.3, 0.1, 0.01, 0.001, 0.0001 and 0 nM.
Intravenous glucose tolerance test (IVGTT): Normal Wistar rats are fasted overnight and are anesthetized prior to the experiment. A blood sampling catheter is inserted into the rats. The compound is given in the jugular vein. Blood samples are taken from the carotid artery. A blood sample is drawn immediately prior to the injection of glucose along with the compound. After the initial blood sample, glucose mixed with compound is injected intravenously (i.v.). Compound may also be injected intravenously or subcutaneously prior to the glucose challenge. A glucose challenge of 0.5 g/kg body weight is given, injecting a total of 1.5 mL vehicle with glucose and agonist per kg body weight. The peptide concentrations are varied to produce the desired dose in μg/kg. Blood samples are drawn at 2, 4, 6 and 10 minutes after giving glucose. The control group of animals receives the same vehicle along with glucose, but with no compound added. In some instances, a 30 minute post-glucose blood sample is drawn. Aprotinin is added to the blood sample (250-500 kIU/ml blood). The serum is then analyzed for glucose and insulin using standard methodologies.
The assay uses a formulated and calibrated peptide stock in PBS. Normally, this stock is a prediluted 100 μM stock. However, a more concentrated stock with approximately 1 mg agonist per 1 mL is used. The specific concentration is always known. Variability in the maximal response is mostly due to variability in the vehicle dose. Protocol details are as follows:
Glucose lowering in diabetic ZDF rats. ZDF rats, 8-9 weeks old with fed glucose levels of approximately 300 mg/dl are used for this experiment. The animals are randomised into control (vehicle) and treatment group(s) on the day of the experiment and are conscious throughout the experiment. The compound is injected intravenously at the start of the experiment and blood samples are drawn from the tail vein immediately prior to compound injection and then 0.5, 1, 2, 3, 4 and 24 h after compound injection. The animals are deprived of food during the first 2 or 4 h of the experiment. The blood samples are collected in EDTA tubes, aprotinin added and immediately put on ice pending insulin and glucose analysis using standard methods.
.6
indicates data missing or illegible when filed
Pharmacokinetic profiles of PEGylated peptides. Healthy Fisher 344 rats (3 animals per group) are injected with 100 μg compound/kg (compound amount based on peptide content and dissolved in PBS buffer). Blood samples are drawn 3, 12, 24, 48, 72, 96 and 168 hour post dosing and the peptide content in plasma is analysed by a radio-immunoassay (RIA) directed against the N-terminus of the peptide. PK parameters are then calculated using a model-independent method (WinNonlin Pro, Pharsight Corp., Mountain View, Calif., USA).
In order to determine the stability of VPAC2 receptor peptide agonists in rat serum, obtain CHO-VPAC2 cells clone #6 (96 well plates/50,000 cells/well and 1 day culture), PBS 1× (Gibco), the peptides for the analysis in a 100 μM stock solution, rat serum from a sacrificed normal Wistar rat, aprotinin, and a DiscoveRx assay kit. The rat serum is stored at 4° C. until use and is used within two weeks.
On Day 0, two 100 μL aliquots of 10 μM peptide in rat serum are prepared by adding 10 μL peptide stock to 90 μL rat serum for each aliquot. 250 kIU aprotinin/mL is added to one of these aliquots. The aliquot is stored with aprotinin at 4° C. The aliquot is stored without aprotinin at 37° C. The aliquots are incubated for 18 hours.
On Day 1, after incubation of the aliquots prepared on day 0 for 24 hours, an incubation buffer containing PBS+1.3 mM CaCl2, 1.2 mM MgCl2, 2 mM glucose, and 0.25 mM IBMX is prepared. A plate with 11 serial 5× dilutions of peptide for the 4° C. and 37° C. aliquot is prepared for each peptide studied. 2000 nM is used as the maximal concentration if the peptide has an EC50 above 1 nM and 1000 nM as maximal concentration if the peptide has an EC50 below 1 nM from the primary screen (see Example 3). The plate(s) are washed with cells twice in incubation buffer. The plates are allowed to hold 50 μL incubation media per well for 15 minutes. 50 μL solution per well is transferred to the cells from the plate prepared with 11 serial 5× dilutions of peptide for the 4° C. and 37° C. aliquot for each peptide studied, using the maximal concentrations that are indicated by the primary screen, in duplicate. This step dilutes the peptide concentration by a factor of two. The cells are incubated at room temperature for 30 minutes. The supernatant is removed. 40 μL/well of the DiscoveRx antibody/extraction buffer is added. The cells are incubated on the shaker (300 rpm) for 1 hour. Normal procedure with the DiscoveRx kit is followed. cAMP standards are included in column 12. EC50 values are determined from the cAMP assay data. The remaining amount of active peptide is estimated by the formula EC50, 4C/EC50, 37C for each condition.
1Values >100% may represent release of intact peptide from the PEG conjugate
1Values >100% may represent release of intact peptide from the PEG conjugate
PEGylation reactions are run under conditions that permit the formation of a thioether bond. Specifically, the pH of the solution ranges from about 4 to 9 and the thiol-containing peptide concentrations range from 1 to 10 molar excess of methoxy-PEG2-MAL concentration. The PEGylation reactions are normally run at room temperature. The PEGylated VPAC2 receptor peptide agonist is then isolated using reverse-phase HPLC or size exclusion chromatography (SEC). PEGylated peptide analogues are characterized using analytical RP-HPLC, HPLC-SEC, SDS-PAGE, and/or MALDI Mass Spectrometry.
Usually a thiol function is introduced into or onto a selective VPAC2 receptor peptide agonist by adding a cysteine or a homocysteine or a thiol-containing moiety at either or both termini or by inserting a cysteine or a homocysteine or a thiol-containing moiety into the sequence. Thiol-containing VPAC2 receptor peptide agonists are reacted with 40 kDa polyethylene glycol-maleimide (PEG-maleimide) to produce derivatives with PEG covalently attached via a thioether bond. For example, P164, [CH3—(CH2)4—CO-HSDAVFTDNYTRLLAKLALQKYLQSIKNKRYGGPSSGAPPPC, 42 AA, 23 mg, 4.8 umol], is dissolved in 4 mL of 200 mM phosphate buffer containing 20 mM EDTA, pH 7.5. The solution is then purged with argon. To this solution is added 230 mg of methoxy-PEG2-MAL-40K, a bifurcated PEG maleimide (Lot# PT-06D-01, Nektar, Huntsville, Ala.) (1:1 ratio of PEG to peptide). The reaction is performed for 2 hours. Then 86 mg of the PEGylated peptide (P190) is obtained after preparative RP-HPLC. The peptide conjugate is characterized by size-exclusion HPLC, and tested for in vitro activity.
Starting from P120, [CH3—(CH2)4—CO-HSDAVFTDNYTRLRKQVAAKKYLQSIKNKRYGGPSSGAPPPC, 42 AA, 22 mg, 4.6 umol] and 200 mg of methoxy-PEG2-MAL-40K, 131.4 mg of PEGylated material (P137) is obtained according to the procedure described above.
Using the same method, 65 mg of PEGylated conjugate (P201) is obtained by reacting 11.3 mg of P200, [CH3—(CH2)4—CO—HSDAVFTENY(OMe)TKLRKQNleAAKKYLNDLKKGGPSSGAPPPC,
2.6 umol] with 98 mg of methoxy-PEG2-MAL-40K).
20 mg of P327, [CH3—(CH2)4—CO—HSDAVFTDNYTOrnLRAibQVAAAibKYLQSIOmNOrnGGPSSGAPPPC-NH2] is dissolved in 3 ml of 100 mM NH4Ac buffer containing 10 mM EDTA, pH 6.8. The solution is purged with argon. 175 mg of methoxy-PEG2-MAL-40K is added to the solution. The reaction is performed for 1 hour. 106 mg of the PEGylated peptide (P138) is isolated by preparative RP-HPLC, characterised by SE-HPLC, and tested for in-vitro activity.
In order to achieve site-specific PEGylation of selective VPAC2 receptor peptide agonists, all the Lys residues are changed into Arg residues except for these Lys residues where PEGylation is intended. For example, the following peptides are used for single or dual site PEGylation: CH3—(CH2)4—CO-HSDAVFTDNYTRLRKQVAAKRYLQSIRNGGPSSGAPPPS (P213), CH3—(CH2)4—CO-HSDAVFTDNYTRLRKQVAARRYLQSIRNGGPSSGAPPPS (P214), CH3—(CH2)4—CO-HSDAVFTDNYTRLRRQVAAKRYLQSIRNGGPSSGAPPPS (P215), CH3—(CH2)4—CO—HSDAVFTDNYTRLRRQVAARKYLQSIRNGGPSSGAPPPS (P216).
For the PEGylation of P213, the peptide is dissolved in 200 mM sodium borate buffer at pH 8.5 and a 1.5-fold molar excess of bulk mPEG-SBA-20K (Nektar, Lot#: PT-04E-11) is added (see scheme below). The reaction is allowed to stir at room temperature for 2-3 hours and then purified by preparative HPLC.
For PEGylation via Pictet-Spengler reaction to occur, a Trp residue with its free amine is needed to incorporate the PEG molecule onto the selective VPAC2 receptor peptide agonist. One approach to achieve this is to add a Lys residue onto the C-terminus of the peptide and then to couple a Trp residue onto the sidechain of Lys. The extensive SAR indicates that this modification does not change the properties of the parent peptide in terms of its in vitro potency and selectivity.
PEG with a functional aldehyde, for example mPEG2-ALD-40K (Nektar, Lot #: PT-6C-05), is used for the reaction. The site specific PEGylation involves the formation a tetracarboline ring between PEG and the peptide. PEGylation is conducted in glacial acetic acid at room temperature for 1 to 48 hours. A 1 to 10 molar excess of the PEG aldehyde is used in the reaction. After the removal of acetic acid, the PEGylation VPAC2 receptor peptide agonist is isolated by preparative RP-HPLC.
Other modifications of the present invention will be apparent to those skilled in the art without departing from the scope of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US05/28520 | 8/11/2005 | WO | 00 | 2/16/2007 |
| Number | Date | Country | |
|---|---|---|---|
| 60602461 | Aug 2004 | US | |
| 60602350 | Aug 2004 | US |
