Patent Application
20190298681
Incorporated by reference in its entirety is a computer-readable sequence listing submitted concurrently herewith and identified as follows: One 48.0 KB ASCII (Text) file named “1107sequence_ST25.txt.”
This disclosure relates to nano-liposomes targeted to the Ephrin receptor A2, useful in the treatment of EphA2 positive cancer, and related diagnostic methods.
Ephrin receptor A2 (EphA2) is part of the Ephrin family of cell-cell junction proteins highly overexpressed in several solid tumors, and is associated with poor prognosis. The Eph receptors are comprised of a large family of tyrosine kinase receptors divided into two groups (A and B) based upon homology of the N-terminal ligand binding domain. The Eph receptors are involved several key signaling pathways that control cell growth, migration and differentiation. These receptors are unique in that their ligands bind to the surface of neighboring cells. The Eph receptors and their ligands display specific patterns of expression during development. For example the EphA2 receptor is expressed in the nervous system during embryonic development and also on the surface of proliferating epithelial cells in adults. EphA2 also plays an important role in angiogenesis and tumor vascularization, mediated through the ligand ephrin A1. In addition, EphA2 is overexpressed in a variety of human epithelial tumors including breast, colon, ovarian, prostate and pancreatic carcinomas. Expression of EphA2 can also be detected in tumor blood vessels and stromal cells as well.
We developed a diagnostic framework for prospective selection of EphA2+ patients for treatment with an EphA-2 targeted nanoliposome encapsulating a docetaxel prodrug, based on a mechanistic single cell cut-off, and a clinical-grade IHC assay. The invention is based in part on the discovery that incubating cells expressing EphA2 with an EphA2-targeted liposome (Example 3) demonstrated specific binding to cells with greater than about 3,000 EphA2 receptors per cell, as determined by the assay methods described herein. For example,
As described in Example 1, we used qFACS and an in vitro assay for liposome (Ls)-cell interaction to identify the minimum number of EphA2 receptors to enable antibody-mediated binding and internalization of Ls. As described in Example 2, we developed an IHC assay able to differentiate EphA2− vs + cell lines. We characterized EphA2 staining pattern in tumor samples of various indications and developed a scoring algorithm that allows selection of patients in early clinical trials.
EphA2-targeted nanoliposomes can be used to deliver docetaxel (e.g., as an encapsulated docetaxel prodrug) to a cancer cell and/or tumor, leveraging organ specificity through a combination of the enhanced permeability and retention (EPR) effect and cellular specificity through EphA2 targeting. The diagnostic framework disclosed herein can be used, for example, in the clinical implementation of EphA2-based exclusion criteria to select cancer patients to receive an EphA2-targeted nanoliposome containing a docetaxel prodrug, or any other stably associated (T1/2 of drug retention greater than 24 h) drug payload.
We developed a novel EphA2-targeted docetaxel nanoliposome, leveraging organ specificity through enhanced permeability effect and cellular specificity through EphA2 targeting. The goal of the study was to develop the diagnostic framework enabling the clinical implementation of EphA2-based exclusion criteria in future trials.
In EphA2 positive tumors (e.g., expressed by either cancer cells or cancer-associate stroma), the EphA2-targeted nanoliposome can bind to EphA2 which can reduce or minimize the washout of liposomes from the tumor, leading to endocytosis of liposomes and the accelerated release of a docetaxel prodrug encapsulated in the EphA2-targeted nanoliposome. Both of these mechanisms are believed to contribute to increased levels of docetaxel delivered to the tumors, both intracellularly and extracellularly, leading to cancer cell death and tumor shrinkage. A key step mediating these mechanisms is the binding of the EphA2-targeted nanoliposome to cells overexpressing EphA2.
“EphA2” refers to Ephrin type-A receptor 2, also referred to as “epithelial cell kinase (ECK),” a receptor tyrosine kinase that can bind and be activated by Ephrin-A ligands. The term “EphA2” can refer to any naturally occurring isoforms of EphA2. The amino acid sequence of human EphA2 is recorded as GenBank Accession No. NP_004422.2.
As used herein, “EphA2 positive” refers to a cancer cell having at least about 3000 EphA2 receptors per cell (or patient with a tumor comprising such a cancer cell). EphA2 positive cells can specifically bind Eph-A2 targeted liposomes per cell. In particular, EphA2 targeted liposomes can specifically bind to EphA2 positive cancer cells having at least about 3000 or more EphA2 receptors per cell.
As used herein, non-targeted liposomes can be designated as “Ls” or “NT-Ls.” Ls (or NT-Ls) can refer to non-targeted liposomes with or without a docetaxel prodrug. “Ls-DTX′” refers to liposomes containing any suitable docetaxel prodrug, including equivalent or alternative embodiments to those docetaxel prodrugs disclosed herein. “NT-Ls-DTX” refers to liposomes without a targeting moiety that encapsulate any suitable docetaxel prodrug, including equivalent or alternative embodiments to those docetaxel prodrugs disclosed herein. Examples of non-targeted liposomes including a particular docetaxel prodrug can be specified in the format “Ls-DTXp[y]” or “NT-DTXp[y]” where [y] refers to a particular compound number specified herein. For example, unless otherwise indicated, Ls-DTXp1 is a liposome containing the docetaxel prodrug of compound 1 herein, without an antibody targeting moiety.
As used herein, targeted immunoliposomes can be designated as “ILs.” Recitation of “ILs-DTXp” refers to any embodiments or variations of the targeted docetaxel-generating immunoliposomes comprising a targeting moiety, such as a scFv. The ILs disclosed herein refer to immunoliposomes comprising a moiety for binding a biological epitope, such as an epitope-binding scFv portion of the immunoliposome. Unless otherwise indicated, ILs recited herein refer to EphA2 binding immunoliposomes (alternatively referred to as “EphA2-ILs”). The term “EphA2-ILs” refers herein to immunoliposomes enabled by the present disclosure with a moiety targeted to bind to EphA2. ILs include EphA2-ILs having a moiety that binds to EphA2 (e.g., using any scFv sequences that bind EphA2). Preferred targeted docetaxel-generating immunoliposomes include ILs-DTXp3, ILs-DTXp4, and ILs-DTXp6. Absent indication to the contrary, these include immunoliposomes with an EphA2 binding moiety and encapsulating docetaxel prodrugs of compound 3, compound 4 or compound 6 (respectively). EphA2-ILs can refer to and include immunoliposomes with or without a docetaxel prodrug (e.g., immunoliposomes encapsulating a trapping agent such as sucrose octasulfate without a docetaxel prodrug).
The abbreviation format “[x]scFv-ILs-DTXp[y]” is used herein to describe examples of immune-liposomes (“ILs”) that include a scFv “targeting” moiety having the amino acid sequence specified in a particular SEQ ID NO:[x], attached to a liposome encapsulating or otherwise containing a docetaxel prodrug (“DTXp”) having a particular Compound number ([y]) specified herein. Unless otherwise indicated, the scFv sequences for targeted ILs can bind to the EphA2 target.
The term “NT-Ls” refers to non-targeted liposomes enabled by this disclosure without a targeting moiety. The term “NT-Ls-DTX′” refers to a non-targeted liposomes enabled by this disclosure encapsulating a docetaxel prodrug (“DTX′”).
The minimum EphA2 expression required for sufficient binding of the liposome was analyzed (Example 1) to determine the relationship between EphA2 expression (measured by qFACs) and target-mediated liposome-cell association in vitro using a panel of cell lines.
As described in Example 1, EphA2 targeted liposome/cell interaction directly correlated with expression target, while non-targeted liposome interaction with cells was minimal and not affected by target expression. The cutoff that can stratify cell lines based on EphA2-ILs/cell interaction was determined by assessing non targeted liposome/cell association and established as the value for the highest non targeted liposome/cell association (343 liposomes/cell). We next used a statistical partition method to determine the optimal EphA2 expression cutoff (≈3,000 receptors/cell) with minimal misclassification
While non targeted Ls do not associate with cells in vitro, there is a strong correlation between EphA2 expression and EphA2-ILs cell association independent of the cell line origin. We used the non-targeted Ls to determine the extent of non-specific binding that can be achieved (˜340 Ls/cell) and used partitioning to determine the minimum number of EphA2 receptors necessary to mediate targeting (˜3,000 receptors/cell). We have developed and validated a qIHC assay for EphA2 (precision ˜90%, linearity 0.8 and reproducibility ˜5%). We stained a set of ˜200 tumor samples from various indications. EphA2 was found to be expressed in tumor cells, tumor-associated myofibroblasts, and tumor-associated blood vessels. Using an inclusive cutoff of 10%, EphA2 prevalence was found to range from 50% to 100% in the tumor types evaluated. No significant difference in staining was seen between metastasis and primary tumors in matched samples.
Results are summarized in Table 1 below.
Example 1 details the characterization of an exemplary Eph-A2 targeted Liposome of Example 3 (herein “EphA2-ILs”), with respect to its ability to bind to tumor cells and establishes a cutoff value of EphA2 expression that is sufficient for EphA2-ILs binding. By comparing results from a screening assay assessing the binding affinity of immunoliposomes incorporating two EphA2 targeting clones 40scFv and 46scFv with a non-targeted liposome (NT-Ls), we have established that there is a high correlation in binding capacity between clones (R2=0.97). Furthermore, immunoliposomes with both EphA2 clones exhibited a statistically significant increase in binding (P<0.0001) compared to an untargeted liposomal control. Subsequent analysis determined that, of the two clones tested, 46scFv-ILs exhibited a higher 49% increase in liposome/cell association than clone 40scFv. In addition, qFACS analysis used to quantify EphA2 expression showed high level of specificity of EphA2 targeted liposomes to EphA2 positive cells. There was a strong correlation (pearson correlation>0.8) between EphA2 targeted liposome association with cells and EphA2 expression.
Materials
Quantibrite beads from BD were used to create a standard curve for number of PE (phycoerythrin) molecules per beads. Following Becton Dickinson's instructions, for each experiment 500 ul of FACs buffer was added to the supplied tube and subsequently read on a BD FACs Calibur flow cytometer previously calibrated with Right Reference beads.
Cells were cultured in the appropriate media (see cell line char) until ˜70-80% confluent then trypsinized, counted, and washed in FACs buffer to obtain a final concentration of 4×10{circumflex over ( )}6 cells/well in each well a 96 well round bottom plate. Cells were then incubated with 200 nM of R&D system's EphA2 PE antibody for 20 minutes on ice, washed and resuspended in 100 ul of FACs buffer. The cells were read on the BD FACs Calibur flow cytometer and data was expressed as described with respect to the qFACs method validation herein.
Liposome-Cell Association Assay: Cell Uptake of Covalently scFv-Conjugated Liposomes
Liposomes are prepared by ethanol injection-extrusion method. For sphingomyelin (SM) liposomes, lipids are comprised of sphingomyelin, cholesterol and PEG-DSG (3:2:0.24 molar parts), with either DiIC18(3)-DS (DiI3-Ls), or DiIC18(5)-DS (DiI5-Ls) fluorescent lipid labels added at a ratio of 0.3 mol % of the total phospholipid. Briefly, for a 30 ml liposome preparation, lipids are dissolved in 3 ml ethanol in a 50-ml round bottom flask at 70 Celsius. HEPES-buffered saline (5 mM HEPES, 144 mM NaCl, pH 6.5) is warmed at 70 Celsius water bath to above 65 Celsius and mixed with the lipid solution under vigorous stirring to give a suspension having 50-100 mM phopsholipid. The obtained milky mixture is then repeatedly extruded, e.g., using thermobarrel Lipex extruder (Northern Lipids, Canada) through 0.2 μm and 0.1 μm polycarbonate membranes at 65-70° C. Phospholipid concentration is measured by phosphate assay. Particle diameter is analyzed by dynamic light scattering. Liposomes prepared by this method have sizes about 95˜115 nm. Anti-EphA2 scFv proteins were expressed in mammalian cell culture, purified by protein A affinity chromatography, and conjugated through C-terminal cysteine residue to maleimide-terminated lipopolymer, mal-PEG-DSPE, in aqueous solution at 1:4 protein/mal-PEG-DSPE molar ratio. The resulting micellar scFv-PEG-DSPE conjugates were purified by gel chromatography on Ultrogel AcA34 or AcA44 (Sigma, USA). Anti-EphA2 scFv proteins were expressed in mammalian cell culture, purified by protein A affinity chromatography, and conjugated through C-terminal cysteine residue to maleimide-terminated lipopolymer, mal-PEG-DSPE, in aqueous solution at 1:4 protein/mal-PEG-DSPE molar ratio. The resulting micellar scFv-PEG-DSPE conjugates were purified by gel chromatography on Ultrogel AcA34 (Sigma, USA). Targeted DiI3-Ls or DiI5-Ls were prepared by incubation with micellar anti-EphA2 scFv-PEG-DSPE conjugate at 60° C. for 30 min at the scFv/liposome ratio of 10-12 g/mol phospholipid for 40scFv-ILs, and 5 g/mol phospholipid for 46scFv-ILs. The ligand inserted liposomes are purified on Sepharose CL-4B column and analyzed by phosphate assay for lipid concentration and SDS-PAGE for antibody quantification.
Cells used in this study should be at 70-90% confluence. 24 hours prior to the study, media was replaced with a fresh aliquot of RPMI (containing 10% FBS, 2 mM glutamine and pep/strep) and harvested by trypsinization. The cells were then resuspended in growth medium, plated out at 100,000 cells per well, washed and incubated with 100 ul of media containing 50 μM phospholipid liposomes. Subsequently, the cells were incubated in the dark at 37° C. for 4 hours with constant shaking. After that time the cells were washed 2-3 times with PBS and resuspended in 100 ul/well PBS for the FACS analysis. The mean cell fluorescence (MCF) of the DiI5 labeled liposomes was determined using FACScalibur (BD bioscience). The observed fluorescence signal is representative of both surface-bound and internalized nanoparticles while the MCF of the cells incubated with blank liposomes (no conjugated scFv) was used to determine non-specific bindings.
Assay Validation
This assay aims to assess target-mediated liposome-cell association in order to quantify the uptake of covalently scFv-conjugated liposomes vs non targeted liposome. We have tested two clones of the EphA2 antibody 46scFv-ILs and 40scFv-ILs. Briefly, cells are incubated with either targeted or non-targeted liposomes fluorescently labeled with a lipophilic fluorophore for 4 hours then washed and measured for single cell fluorescence using flow cytometry. Fluorescent beads with a known number of fluorophores were used as standard curve to determine the number of liposomes from mean fluorescence values. Overall, the assay demonstrated high linearity (mean R2=0.98), reproducibility (intercept and slope for the standard curve within 10%) and low intra-assay variability (average CV between technical replicates=2.1% [0.03%-19%]). A subset of cell lines (20%=13/65) was run twice and data shows reproducible Liposomal uptake between runs: RUN#1 labeled as POC10 and RUN#2 labeled as RUN#74. For assay reproducibility 40scFv-ILs was used. In order to back calculate number of liposomes and an estimated docetaxel load, we use the following equations.
Phospholipids in nmoles/million cells
ncys: number of fluorophores calculated from beads standard curve
fDil5: molar percentage of Dil5 per liposome (=0.216)
L: Avogadro number in nmoles (6.02×1014)
a: Quantum yield correction between the beads Cy5 and the liposomal Dil5(=3.76±0.25 measured)
nLs: number of Liposomes associated to a cell due to EphA2 targeting
PhLEphA2: amount of EphA2 targeted liposomes
PhLnT: amount of non-targeted liposomes
LSPHL: number of phospholipid molecules per liposome (=80 104)
L: Avogadro number in nmoles (6.02×1014)
nDocetaxel: Predicted amount of Docetaxel delivered due to EphA2 targeting in ngram/million cells
PhLEPhA2: amount of EphA2 targeted liposomes
PhLnT: amount of non-targeted liposomes
Docetaxelload: amount of docetaxel loaded per liposome in gram of docetaxel/mole of PhL
CDweiaxel: Predicted concentration of Docetaxel compatible with in vitro IC50experiments in ng/ml
V: volume of incubation media in 384 well plate (50 ul)
To validate the liposome-cell association assay, we tested the reproducibility in two biological replicates. POC10 and Run#74 represent two runs of the assay performed one month apart and done over 4 days for each run. No significant difference between the two runs for EphA2-Liposome (40scFv-ILs) and NT-Liposome levels. B. Standard curves from Run#74 performed with every flow cytometric run and shows linearity and stability of the assay.
EphA2-Targeted Vs. Non Targeted Liposome-Cell Association
To determine the correlation between clones, a set of 34 cell lines were assessed side by side. Both clones showed a high correlation to each other as indicated by an R2 value of 0.97. However, 46scFv-ILs led to a statistically significant higher liposome-cell association than clone 40scFv-ILs (p<0.0001), with on average 49% increase in the number of liposomes per cell and a standard deviation of 21%.
EphA2 qFACs Assay Validation
The EphA2 qFACS assay aims to quantify EphA2 molecules per cell using quantitative flow cytometry (qFACs). To summarize, cells are incubated with EphA2 antibody (R&D Clone 3035 mouse monoclonal) conjugated to PE for 1 hour. The cells of interest are then washed and assessed for fluorescence intensity using flow cytometry. PE labeled beads (Quantibtrite™ PE-quantitation kit, BD bioscience) are concomitantly analyzed using flow cytometry and subjected to linear regression analysis to back calculate the number of antibodies bound to each cell. We assume that one antibody can only bind to one antigen, thus the number of antibodies is equal to the number of receptors per cell. In terms of assay performance, the assay is highly linear (mean R2=0.99) and reproducible (intercept and slope for the standard curve within 10%) and theintra-assay variability was low (average CV between technical replicates=5.6% [0.6%-37%]). A subset of cell lines was run twice and data shows reproducible EphA2 levels. Referring to theEphA2 qFACs assay validation, two runs of the assay were performed one month apart and done over 4 days for each run. No significant difference between the two runs for EphA2 levels. In addition, standard curves were performed with every qFACs run and shows linearity and stability of the assay.
Characterization of EphA2 Expression in Cancer Cell Lines
We performed qFACs and liposome-cell association studies on the same day and using the same batch of cells. qFACs data shows that EphA2 ranged from 422 to 143,888 receptors per cell (
EphA2 Expression Vs. Target-Mediated Liposome-Cell Association
The goal of this analysis is to assess the correlation between EphA2 expression and target mediated liposome-cell association. We found a significant correlation between EphA2 expression and EphA2-ILs-cell association (Pearson correlation coefficient=0.81 for 46scFv-ILs and 0.88 for F5-10A7) which was independent of the EphA2 antibody clone.
Referring to
Given the relationship between EphA2 expression and target-mediated liposome-cell association, we have identified a cutoff that can classify the cell lines. The cutoff was determined by assessing non-targeted liposome-cell association and established by taking the 99 percentile of NT-Ls-cell association which is about 340 liposomes/cell. We used a statistical partition method to determine the optimal EphA2 expression cutoff (about 3000 receptors/cell) with minimal misclassification (=1% error). This cutoff separates targeting-negative from targeting-positive cell lines.
While the first cutoff is derived from non-targeted liposome-cell association, the second cutoff (separates EphA2+ from EphA2++
This example describes the EphA2 IHC CDx assay. The assay was tuned to allow visual detection of EphA2 expression matching the identified cutoff of 3000 receptors/cell. The assay demonstrated acceptable levels of sensitivity, specificity and precision. All the planned tasks were completed and the EphA2 IHC CDx demonstrated specificity and sensitivity for EphA2 staining and had solid precision as defined by using quantitative image analysis.
The EphA2 IHC CDx showed high level of specificity and sensitivity when tested in a set of cancer cell lines with a range of EphA2 expression. Intra-assay and inter-assay variability was very low in cell lines and tissue samples.
Materials & Methods
Cell array and TMA maps are found in Appendix A, and described in Table 5. All tissue samples were selected to include all the relevant tumor types that will be included in the Phase 1 trial. For all the cell lines we focused on the three tumor types from which we included a large set of cell panel.
EphA2 IHC CDx Sectioning and Staining Protocol Performed on Dako Autostainer Instrument
Tissue sections were cut at 5 micron thickness and mounted on positively charged slides for immunohistochemistry analysis. Primary antibody used: Rabbit mAb EphA2 (D4A2) (Cell Signaling Technology-22050BF) used at 1:1000 dilution to a working concentration of 2 μg/ml. A range of concentrations were tested and acceptable concentration was identified as low as 1 μg/ml and up to 10 μg/ml (
Labelled Polymer Used: En Vision+ System-HRP Labelled Polymer Anti-Rabbit (DAKO K400311)
1. General procedure
2. + Deparaffinization
3. + Antigen Retrieval: 25 minutes @ 102° C.
4. + Endogenous Enzyme Block (Peroxidased): 10 minutes
5. + Buffer Rinse: 4 minutes
6. + Protein Block: 10 minutes
7. + Buffer Rinse: 4 minutes
8. + Primary Antibody at a dose of 2 μg/nnl for 60 minutes
9. + Buffer Rinse: 4 minutes
10. + Labelled Polymer: 30 minutes
11. + Buffer Rinse: 4 minutes
12. + Flex DAB+ Substrate-Chromogen: 10 minutes
13. + Buffer Rinse: 4 minutes
14. + Auto Hematoxylin: 6 minutes
15. + Buffer Rinse: 4 minutes
16. + Coverslip
Quantitative Flow Cytometry
Cell lines characterized in previous example (example 1) were used to evaluate the performance of the assay. In summary, qFACs was used to quantify EphA2 receptor per cell in 65 cell lines (13 of which were done in duplicates). EphA2 expression ranges from 422 to 143,888 receptors per cell.
Formalin Fixed Paraffin Embedded (FFPE) Cell Pellets
Each cell line was processed to expanded and processed to mimic clinical samples leading to the generation of formalin fixed paraffin embedded cell pellets. In summary, cells were expanded to 50-200 million cells, washed with PBS, tripsinzed using 0.05% trypsine, centrifuged and washed in PBS, fixed in 10% formalin for 2-4 hours prior to switching them to 70% ethanol. Cells were stored at 4° C. in 70% ethanol for up to one week. Cells embedded in histogel at a density of 1×105/μl of histogel. Histogel embedded cell pellets are stored in 70% ethanol prior to standard processing in paraffin embedding processor. From FFPE blocks, cell arrays were generated by extracting 2 mm cores from each block and transferring them to a cell array block.
Cell Line Transfection
In order to generate EphA2 overexpressing cell lines we used ready to go particle (GeneCopoeia, Rockville, Md.). The construct is based on pReceiver-Lv105, a Puromycin selectable lentiviral vector.
EphA2 Gene Info:
NM_004431.1. Virus cat#: LP-A0125-LV105-0205. The info and protocol can be downloaded at www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Signna/General_Infornnation/lentiviraltransdprotocol.pdf.
However, we adjusted and modified the protocol of infection as needed. Our protocol for the IGROV-1 cell lines was performed as following: Day1, count and seed cells into a 96-well (4,000 cells per well in 100 ul media) plate; Day2, 1) remove media and add 100 μl infection solution containing Polybrene [e.c. 8 μg/ml] and 5 μl [low MOI] or 30 ul [high MOI] EphA2 expressing virus. 2a) spin at room temperature for 90 min at 2300 rpm and leave overnight in incubator at 37° C. 2b) if cells show Polybrene sensitivity, add the same day 150 μl/well fresh growth media after 6 h of incubation. 2c) alternatively, reduce Polybrene final concentration down to 4 μg/ml. 2d) if cells show sensitivity towards the long spin, reduce time to 30 min and increase temperature to 30° C.; day 3, remove all media and replace with 200 μl fresh growth media, day 4 rest, day 5 start 5 days Puromycin selection by replacing the media with 2 μg/ml Puro containing growth media, and day 6 test EphA2 expression levels by FACS or similar methods.
Validation Approach
To assess intra-assay and inter-assay precision slides were stained together in triplicates three times generating stained slides (Run1.1, Run1.2, Run1.3, Run2.1, Run2.2, Run2.3, Run3.1, Run3.2, Run3.3). Staining runs were performed on different days (Day 1, Day 3, Day 5) with two different operators. 1) Day 1—Note: The assay run for the intra-assay precision represents the samples on Day 1 of the inter-assay precision as well. 2) Day 3—The assays will be repeated on a second replicate set of 3 unstained slides from the same TMA blocks used on Day 1. 3) Day 5—The assays were repeated on a third replicate set of 3 unstained slides from the same TMA blocks used on Day 1 and Day3
Microscopy and Image Analysis
Images were collected with an AperioBF Scanscope (Leica Biosystems, Buffalo Grove Ill.) at 20× magnification. Quantitation of EphA2 brown signal was done using an in-house algorithm and user interface developed using Matlab (Mathworks, Natick, Mass.). In summary, cells or tissue areas were segmented using a semi-automated threshold based algorithm in which the user can change the threshold or manually include or exclude areas. A core annotation tool is used to match the cores to the sample ID, which is QCed by the user for every image. Snapshot images are stored for further QC. A higher resolution tissue segmentation algorithm is used to tighten the mask around the tissue or cells. From each core, an average brown stain intensity is computed by converting the RGB image to the color space CYMK and using the yellow channel as the best representative for the brown color. Mean brown signal intensity will be captured for each cell line or tumor within the TMA and used for sensitivity, specificity, and precision calculations.
Statistical Analysis
All statistical analyses were performed using JMP (SAS, NC). For analysis of the cell lines, CA022515, linear regression was performed to assess the linearity of EphA2 IHC brown intensity vs EphA2 receptors/cell and R2 were used as a metric for linearity. Partition analysis was performed to evaluate the ability of the assay to classify EphA2+ vs. EphA2− cell lines (using our pre-established mechanistic cutoff of about 3,000 receptors/cell). Partition analysis was also performed to evaluate the ability of the assay to classify EphA2− vs EphA2+ vs EphA2++ cell lines based on the second cutoff of about 17,500 receptors/cell. Intra-assay and inter-assay variability were assessed by computing CV for each cell line, for the slope of the linear regression and for the cutoff of the partition analysis. For analysis of HTMA060915, intra-assay and inter-assay variability were assessed by computing coefficient of variance (CV) for each tumor sample of the TMA. For analysis of cell lines CA111014, qualitative assessed of the staining pattern of EphA2 in the EphA2 overexpressing cell line as it compares to the parental cell line.
Sensitivity and Specificity and Precision Using IHC Staining Quantitative Image Analysis Correlation to Quantitative Flow Cytometry
IHC assay was optimized to enable classification of cell lines into EphA2−, EphA2+, EphA2++. We used our cell line panel and tested several concentrations of primary antibodies keeping all the other parameters of the protocol the same. We tested 0, 1, 2, 6, 10 and 20 μg/ml of primary antibody. We found that the assay was highly tunable and that the error as computed by AUC of ROC was <10% for 1, 2 and 5 μg/ml and was 11 and 14% for 10 and 20 μg/ml. At 20 μg/ml, the upper ranges of the cell lines were saturated. To enable pathologist based detection of the signal we evaluated the strength of the brown staining by eye and found that intensities between 10 and 14 were not visible, and thus we choose a concentration of 2 μg/ml which enables by eye scoring of the staining.
To assess the sensitivity and specificity and precision of the EphA2 IHC assay, the blocks containing 78 cell lines contained 65 unique cell lines with known varying levels of EphA2 expression were sectioned and stained. Correlation and linearity were assessed by analyzing the EPhA2 brown staining vs. receptor per cell (
IHC assay was able to reproducibly classify the EphA2− and the EphA2+ cell lines with an error<10%. Intra and inter run variability was minimal.
IHC assay was also able to reproducibly classify the EphA2− cell lines with an error ranging from 2 to 3%, EphA2+ cell lines with an error ranging from 22% to 10% and the EphA2++ cell lines with an error ranging from 10% to 7%. Intra and inter precision of the cutoffs show very low variability between runs and within a run.
Intra and inter precision of the quantitative image analysis was also assessed by computing CV at the cell line level. CVs computed in all cell lines showed intra-assay average CV ranging from 1.28%-1.55% with a maximum CV of 6.2%. For inter-assay the average CV was 2.24% and the maximum CV was 23.8% with >95% of the cells lines having CV<20%.
Precision Using Tissue Microarrays
The precision runs using TMA samples consisted of three staining days for three replicate slides and performed by two operators. Below is the description of the run:
Intra- and inter-assay precision will be assessed for reproducibility of staining within the same immunohistochemical staining batch (intra-assay), over separate immunohistochemical staining batches (inter-assay), performed by different operators (inter-operator), and stained on different instruments (inter-instrument). Average brown intensity (units) was extracted from each core including both stroma and tumor tissue. CVs were computed for every core within the run (intra-assay) and between the cores using the average of the three slides within the run (inter-assay) (Table 3). Overall no core reached the % CV maximum permitted level of 20%, and most were below 10%. The median intra-assay CV was 2.9% with 25% percentile 2% and 75% percentile 4.76%. The median inter-assay CV was 2.6% with 25% percentile 1.5% and 75% percentile 3.9%. Intra-assay and inter-assay variability was independent of mean brown intensity (Table 8).
Specificity of EphA2 IHC CDx Tested Using EphA2 Transfected Cell Line.
The IGROV-1 cell line was found to have the lowest levels of EphA2 expression by qFACs which was also seen in cell pellets using the EphA2 IHC CDx. We overexpressed EphA2 using a lentiviral construct and confirmed expression by qFACS. Parental IGROV-1 cells have about 1,000 EphA2 receptors/cell while IGROV-1-EPhA2 has about 10000 receptors/cell. Since our mechanistic cutoff is 3,000 receptors/cell, the transfection was able to generate an EphA2+ IGROV cell line. The moderate expression also allows us to qualitatively assess the sensitivity of the assay. Since the analysis is limited to comparing two paired cell lines, we performed qualitative assessment of the staining pattern and have included a snapshot of the cell lines in the report (
EphA2 IHC Scoring Guidance
Control Slide
Cancer Cell Scoring (IHC)
Goal is to estimate percentage of positive cancer cells independently of staining intensity. Staining intensity is only referenced to facilitate scoring guidelines.
Criteria
If the staining is intense but includes a mixture of cell membrane and cytoplasmic staining patterns or If the staining is very dim confirm the presence of cell membrane location using 20× and 40×.
Tumor Associated Blood Vessels (TAV) Scoring Guidance
Goal is to estimate percentage of high power fields containing at least one positive TAV independently of staining intensity.
Evaluate the EphA2 sections for estimation of the percentage of positive high power field with at least one EphA2+ TAV at low power first, 10× magnification.
Method
Report the number of positive and total high power fields
Criteria
Assessment of EphA2+ TAV should be restricted to tissue fragments that include cancer cells. Benign fragments should be excluded from the analysis.
TAV are defined as blood vessels within 2 mm from tumor areas. Blood vessels>2 mm from tumor areas should be excluded from the analysis.
Staining that seems stromal but that is not clearly vascular should be excluded. This applies to non specific staining and myofibroblasts.
Serum staining can be seen and can potentially interfere with endothelial staining assessment. Vessels with weak endothelial staining and serum staining should not be excluded.
EphA2 positive TAV seen at 10× confirmed at higher magnification
Exclude when serum staining artifact hinders endothelial assessment
Exclude when staining not clearly endothelial
The EphA2 targeted nano-liposome is preferably a unilamellar lipid bilayer vesicle, approximately 110 nm in diameter, which encapsulates an aqueous space which contains a docetaxel prodrug that converts to docetaxel at a pH present a treatment site.
Preferably, the docetaxel prodrug comprises a weak base such as tertiary amine introduced to the 2′ hydroxyl group of docetaxel through ester bond to form a docetaxel prodrug. Preferred 2′-docetaxel prodrugs suitable for loading into a liposome are characterized by comparatively high stability at acidic pH but convert to docetaxel at physiological pH through simple hydrolysis.
The docetaxel prodrug can be stabilized in the liposomal interior during storage and while the intact liposome is in the general circulation, but is hydrolyzed rapidly (e.g., t½=˜10 h) to the active docetaxel upon release from the liposome and entering the environment of the circulating blood.
A docetaxel prodrug can be loaded at mildly acidic pH and entrapped in the acidic interior of liposomes, using an electrochemical gradient where it is stabilized in a non-soluble form.
The docetaxel-generating liposome can comprises a EphA2 targeting moiety. As used herein, unless otherwise indicated, the term “anti-EphA2 scFv” refers to an scFv that immunospecifically binds to EphA2, preferably the ECD of EphA2. An EphA2-specific scFv preferably does not bind to antigens not present in the EphA2 protein. The targeting moiety can be a single chain Fv (“scFv”), a protein that can be covalently bound to a liposome to target the docetaxel-producing liposomes disclosed herein. The scFv can be comprised of a single polypeptide chain in which a VH and a VL are covalently linked to each other, typically via a linker peptide that allows the formation of a functional antigen binding site comprised of VH and VL CDRs. An Ig light or heavy chain variable region is composed of a plurality of “framework” regions (FR) alternating with three hypervariable regions, also called “complementarity determining regions” or “CDRs”.
In certain embodiments, an scFv disclosed herein includes one or any combination of VH FR1, VH FR2, VH FR3, VL FR1, VL FR2, and VL FR3 set forth in Table 10. In one embodiment, the scFv contains the frameworks of the sequences of Table 10 below.
In certain aspects, an scFv disclosed herein is thermostable, e.g., such that the scFv is well-suited for robust and scalable manufacturing. As used herein, a “thermostable” scFv is an scFv having a melting temperature (Tm) of greater than 67° C. or at least about 70° C., e.g., as measured using differential scanning fluorimetry (DSF).
A preferred anti-EphA2 scFv binds to the extracellular domain of EphA2 polypeptide, i.e., the part of the EphA2 protein spanning at least amino acid residues 25 to 534 of the sequence set forth in GenBank Accession No. NP_004422.2 or UniProt Accession No. P29317.
In certain embodiments, an anti-EphA2 scFv disclosed herein includes a VH CDR1, VH CDR2, VH CDR3, VL CDR1, VL CDR2, and VL CDR3 each with a sequence as set forth in Table 11. Note that the VH CDR2 sequence (also referred to as CDRH2) will be any one selected from the 18 different VH CDR2 sequences set forth in Table 11.
In one particular example of a PEGylated EphA2 targeted liposome encapsulating a docetaxel prodrug, the lipid membrane can be composed of N-(hexadecanoyl)-sphing-4-enine-1-phosphocholine (egg sphingomyelin), cholesterol, and 1,2-distearoyl-sn-glycerol, methoxypolyethylene glycol (PEG-DSG). The nanoliposomes can be dispersed in an aqueous buffered solution, such as a sterile pharmaceutical composition formulated for parenteral administration to a human. The PEGylated EphA2 targeted liposome can include the targeting moiety of TS1 (SEQ ID NO:40), D2-1A7 (SEQ ID NO:41) or scFv3 below (SEQ ID NO:46):
An exemplary EphA2 targeted docetaxel-generating nanoliposome composition designated “46scFv-ILs-DTXp3,” a targeted liposome comprising a compound of Formula (I) designated Compound 3 encapsulated in a lipid vesicle formed from egg sphingomyelin, cholesterol and PEG-DSG in a weight ratio of about 4.4:1.6:1, with scFv of SEQ ID NO:46 attached to the lipid vesicle (to provide targeting to EphA2) in a weight ratio of about 1:142 of the total amount of sphingomyelin in the lipid vesicle.
Two specific examples of preferred EphA2 targeted docetaxel-generating nanoliposome compositions are 46scFv-ILs-DTXp3 (i.e., the EphA2 targeted docetaxel-generating nanoliposome composition comprising the scFv of SEQ ID NO:46 attached to an immunoliposome encapsulating docetaxel prodrug Compound 3 herein) and 46scFv-ILs-DTXp4. Alternative preferred embodiments can include EphA2 targeted docetaxel-generating immunoliposomes with:
Ephrin receptor A2 (EphA2) is part of the Ephrin family of cell-cell junction proteins highly overexpressed in several solid tumors, and is associated with poor prognosis. We developed a novel EphA2-targeted docetaxel nanoliposome, leveraging organ specificity through the enhanced permeability and retention effect and cellular specificity through EphA2 targeting. The goal of the study was to develop the diagnostic framework enabling the clinical implementation of EphA2-based exclusion criteria in future MM-310 trials.
We used qFACS and an in vitro assay for liposome (Ls)-cell interaction to identify the minimum number of EphA2 receptors to enable antibody-mediated internalization of Ls. We developed an IHC assay able to differentiate EphA2− vs + cell lines. We characterized EphA2 staining pattern in tumor samples of various indications and developed a scoring algorithm that allows selection of patients in early clinical trials.
While non-targeted Ls do not associate with cells in vitro, there is a strong correlation between EphA2 expression and EphA2-Ls cell association independent of the cell line origin. We used the non-targeted Ls to determine the extent of non-specific binding that can be achieved (˜340 Ls/cell) and used partitioning to determine the minimum number of EphA2 receptors necessary to mediate targeting (˜3000 receptors/cell). We have developed and validated a qIHC assay for EphA2 (precision ˜90%, linearity 0.8 and reproducibility CV<5%). We stained a set of ˜200 tumor samples from various indications. EphA2 was found to be expressed in tumor cells, tumor-associated myofibroblasts, and tumor-associated blood vessels. Using an inclusive cutoff of 10%, EphA2 prevalence was found to range from 50% to 100% in the tumor types evaluated. No significant difference in staining was seen between metastasis and primary tumors in matched samples.
In summary, we developed a diagnostic framework for prospective selection of EphA2+ patients for MM-310 trials based on a mechanistic single cell cut-off and a clinical-grade IHC assay.
To assess EphA2 expression evolution during disease progression, we evaluated the expression of EphA2 in matched primary/metastasis samples of the same patients. We acquired two sets of samples (1) all indication set of 12 patients (2) a bladder cancer set of 10 patients. EphA2 expression was consistent between primary and metastasis in both sets with a concordance of 91% and 90% in the all indication set and the bladder cancer set respectively.
In vitro cell binding data was used to identify minimum number of EphA2/cell to allow targeted liposome uptake. Immunohistochemistry assay for EphA2 in formalin-fixed, paraffin embedded tissues was analytically validated and used to survey human tumors from several indications. EphA2 was observed in tumor cells, stroma, and in tumor-associated blood vessels, and was consistently expressed in matched primary tumors and metastases. EphA2 negative patients will be excluded from clinical trials based upon prospective screening results. Retrospective analysis of EphA2 compartment contributions when patient outcome data is available will be used to refine inclusion criteria to best serve patients who would benefit from MM-310.
This patent application claims priority to PCT International National Application No. PCT/US2017/022627, filed Mar. 16, 2017, which claims the benefit under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/322,971 filed on Apr. 15, 2016, and U.S. Provisional Application No. 62/309,215 filed on Mar. 16, 2016. The entire contents of these applications are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/022627 | 3/16/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62309215 | Mar 2016 | US | |
| 62322971 | Apr 2016 | US |
