Patent Application
20080096811
Approximately 0.5-0.6 grams (0.38-0.45 mmole) Boc Pro-MBHA 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-8-cyclohexyl ester(CHXL), Glu-δ-cyclohexyl ester (CHXL), 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 diisopropylcarbodiimde (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 BF (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.
Approximately 114 mg (50 mMole) FMOC-Rink amide 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-β-t-Butyl ester (tBu), Glu-δ-t-butyl ester (tBu), Gln-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% Pip/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 run 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.
DiscoveRx: A CHO—S cell line stably expressing human VPAC2 receptor in a 96-well microtiter plate is seeded with 50,000 cells/well the day before the assay. The cells are allowed to attach for 24 hours in 200 μL culture medium. On the day of the experiment, the medium is removed. Also, 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. Then, the assay buffer is 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. In the case of VPAC1 and PAC1 receptors, CHO—PO cells are transiently transfected with human VPAC1 or PAC1 receptor DNA using commercially available transfection reagents (Lipofectamine from Invitrogen). The cells are seeded at a density of 10,000/well in a 96-well plate and are allowed to grow for 3 days in 200 mL culture medium. At day 3, the assay described above for the VPAC2 receptor cell line is performed.
Results for each agonist are the mean of two independent runs. VPAC1 and PAC1 results are only generated using the DiscoveRx assay. 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.
Alpha screen: Cells are washed in the culture flask once with PBS. Then, the cells are 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 Perlin-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, VPAC1, and PAC1 receptors is reported in Table 1.
1EC50 (nM); Mean of two independent runs
2EC50 (nM); Single result from two analyses performed in a single run
3Mean of separate results for the given assay
4NA = Not assayed (for all NA entries)
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 BEPES 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, aspirate the presoak solution by vacuum filtration. Flush the plates twice with 200 μL flush buffer. Add 200 μL blocking buffer to the filter plate. The filter plate is then incubated with 200 μL presoak solution for 1 hour at room temperature.
Fill the assay plate with 25 μL assay buffer, 25 μL 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. Incubate the filled plate for 1 hour with shaking.
Conduct the transfer from assay plate to filter plate. Aspirate the blocking buffer by vacuum filtration and wash two times with flush buffer. Transfer 90 μL from the assay plate to the filter plate. Aspirate the 90 μL transferred from assay plate and wash three times with 200 μL flush buffer. Remove the plastic support. Dry for 1 hour at 60° C. Add 30 μL Microscint. Perform the count. The selectivity (IC50) for human VPAC2, VPAC1, and PAC1 is reported in Table 2.
1NA = Not assayed (for all NA entries)
2Mean of separate results for the given assay
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.). 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 concentration vary 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 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 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:
1NA = Not assayed
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, prepare two 100 μL aliquots of 10 μM peptide in rat serum by adding 10 μL peptide stock to 90 μL rat serum for each aliquot. Add 250 kIU aprotinin/mL to one of these aliquots. Store the aliquot with aprotinin at 4° C. Store the aliquot without aprotinin at 37° C. Allow the aliquots to incubate for 18 hours.
On Day 1, after incubation of the aliquots prepared on day 0 for 18 hours, prepare an incubation buffer containing PBS+1.3 mM CaCl2, 1.2 mM MgCl2, 2 mM glucose, and 0.25 mM IBMX. Prepare a plate with 11 serial 5× dilutions of peptide for the 4° C. and 37° C. aliquot for each peptide studied. Use 2000 nM 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). Wash the plate(s) with cells twice in incubation buffer. Allow the plates to hold 50 μL incubation media per well for 15 minutes. Transfer 50 μL solution per well to the cells from the plate prepared with 11 serial 3× 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. Incubate in room temperature for 30 minutes. Remove the supernatant. Add 40 μL/well of the DiscoveRx antibody/extraction buffer. Incubate on the shaker (300 rpm) for 1 hour. Proceed as normal with the DiscoveRx kit. Include cAMP standards in column 12. Determine EC50 values from the cAMP assay data. The remaining amount of active peptide is estimated by the formula EC50,4C/EC50,37C for each condition.
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/US05/17434 | 5/19/2005 | WO | 00 | 11/20/2006 |
| Number | Date | Country | |
|---|---|---|---|
| 60573080 | May 2004 | US |
