Peptide Abbreviated New Drug Application (PANDA)
Current FDA guidelines on synthetic peptide drugs mandate that pharmaceutical manufacturers of generic drugs provide information that mentions potential impurities in the drug formulation. As their recently issued draft states, for each new specified peptide-related impurity that is no more than 0.5 percent of the drug substance, the Abbreviated New Drug Application (ANDA) applicant must characterize the impurity and provide a justification for why such impurity does not affect the safety or effectiveness of the generic synthetic peptide. This justification must include data that supports the claim that any differences in impurities between the proposed generic synthetic peptide and the Reference Listed Drugs (RLDs) do not modify the immunogenicity risk of the product.
PANDA, EpiVax’s proprietary Peptide Abbreviated New Drug Application screening, is a multi-step approach to assessing the immunogenicity of RLDs, corresponding synthetically-produced generic peptide products and their process-related peptide impurities to evaluate bioequivalence. These steps include an initial assessment with EpiVax’s proprietary in silico toolkit followed by validation of the resulting predictions with an in vitro laboratory assay and lastly, a full literature review. The PANDA approach is used by many clients for immunogenicity screening in the context of seeking FDA approval for generic peptide products.
Phase 1: In Silico PreDeFT Immunogenicity Analysis
The Pre-Deimmunization of a Functional Therapeutic (PreDeFT) report is a concise description of each input sequence’s immunogenic potential. Immunoinformatics experts at EpiVax will use the applicable ISPRI (Interactive Screening and Protein Reengineering Interface) tools to analyze the sequences of the synthetically-produced generic peptide product, along with any process-related peptide impurities. Briefly, EpiVax will parse the input sequences into overlapping 9 amino acid frames and evaluate each frame for its binding potential to a panel of Class II HLA allele “supertypes”, which represent 95% of the global human population. Using the EpiMatrix algorithm, EpiVax will produce overall and regional assessments of T cell-dependent immunogenic potential, and screen putative T cell epitopes for cross-conservation with the human proteome using JanusMatrix. EpiVax will then compile the results into a report describing our findings with respect to the predicted immunogenicity of the input sequences.
Phase 2: In Vitro Methods – HLA Binding and Naïve Donor T Cell Assay
EpiVax’s competitive HLA Binding Assay provides an indirect measure of potential immunogenicity. Class II HLA binding assays may be used to measure affinity of putative epitopes for multiple HLA alleles. EpiVax employs a competition-based HLA binding assay originally described by Steere et al.  and adapted for commercial use by EpiVax. Our assay employs highly-purified Class II molecules. This assay format is far superior in sensitivity and specificity compared to cell-based assay formats. Based on a 7 concentration peptide titration, a non-linear regression analysis is performed and an IC50 value is calculated. Peptides are evaluated for 8 common Class II alleles.
EpiVax has adapted an In Vitro Immunization Protocol (IVIP) to test the immunogenicity of therapeutics in human lymphocyte cultures. This approach utilizes blood from healthy, HLA-typed donors to closely mimic a natural, naïve human immune response to a potential antigen. Briefly, peripheral blood mononuclear cells (PBMCs) are isolated from HLA-typed donors and are cultured for 14 days. On Day 1, naïve PBMCs from HLA-typed donors are stimulated with the test article or relevant control. Test articles may be the RLD, the generic peptide or individual process-related impurity peptides depending on the project needs and goals. PBMC cultures are routinely replenished with media and supportive cytokines then PBMCs are restimulated (challenged) with the corresponding test article or control. Cultures are then tested by FluoroSpot assay for immunoinflammatory and/or immunosuppressive cytokines to quantify cytokine-producing cells. The most common format is interferon-gamma (IFN-g).
Phase 3: FDA-Ready Immunogenicity Report
EpiVax is well-respected as a leading immunogenicity screening provider and enjoys a positive reputation with the US Food and Drug Administration (FDA). To produce an FDA-Ready Immunogenicity Report, the experienced immunology team at EpiVax compiles the results of the previous project phases into one comprehensive report. This report includes a detailed description of the predicted immunogenic potential and observed immunogenicity ex vivo of multiple RLD and the synthetically-produced generic peptide product lots, in addition to the opinions and recommendations of EpiVax experts regarding the contribution of the process-related peptide impurities to overall immunogenicity. EpiVax’s FDA-Ready Immunogenicity Reports can be used to support regulatory filings, increasing the likelihood of a favorable review.