Category: Formulation and Quality
Purpose: The patents for many peptide drugs are expiring within 5-10 years, setting the stage for a wave of generic applications seeking approval based on their sameness to the reference product. Assessing sameness requires a quantitative and qualitative comparison of the impurity profile of the generic and the reference listed products (RLD). Minor differences in the impurity profiles may be justified provided that these differences would not affect the safety and efficacy of the proposed product. In this study, we developed and validated an UPLC LC-MS method to identify and quantify differences in the impurity profiles of teriparatide, a 34 amino-acid therapeutic peptide, derived from different origins (recombinant-derived teriparatide drug product and synthetic teriparatide purchased commercially). To comply with the FDA guidance “ANDAs for Certain Highly Purified Synthetic Peptide Drug Products that Refer to Listed Drugs of rDNA Origin” (1), the UPLC-MS method would need to be both sensitive (LOQ should be NMT 0.05%) and robust enough for routine analysis.
Methods: Teriparatide drug product and synthetic teriparatide purchased from Bachem were analyzed by LC-MS for relative quantification, and LC-MS/MS for impurity identification, on a Thermo Q-Exactive HF-X mass spectrometer. LC separation was performed on a Waters Acquity UPLC BEH C18 1.7µm 2.1 x 150 mm column, with an Agilent 1260/1290 HPLC connected online to the mass spectrometer. Peptide identification and relative quantification was performed using PEAKS X, Thermo Xcalibur integration, and manual verification.
Results: Twenty-five impurities were identified and quantified across the samples (Figs. 1 and 2). The impurities were classified as originating from either a degradation- or production process-related mechanism based on their change in abundance in drug product of varying age and between the two manufacturers (Figs. 2 and 3). The same degradation-dependent impurities were generally found in both the drug product and synthetic teriparatide. However, these impurities were found at higher levels in the drug product (2.0-130.0-fold average increase depending on the impurity). We theorized that this is due to differences in sample storage. The drug product degraded more as it was stored as a solution at 4°C, while the synthetic teriparatide was stored as a lyophilized powder at -80° C.
Eight additional impurities were found in the drug product and nine in the synthetic teriparatide. The level of these impurities was relatively constant with increasing drug product age and did not change in a time-dependent manner (Figs. 2 and 3). These impurities are thought to arise from the peptide manufacturing process. The manufacturing process-related impurities in the synthetic teriparatide included seven sequence variants, such as single and double amino acid insertion and deletion, at up to 0.22% abundance (for S1 deletion). Such variants are unavoidable by-products of the peptide synthesis process, and depending on the post-synthesis purification steps, can remain present in the final drug substance.
The UPLC-MS method developed here can detect all impurities at a reporting threshold of ≥0.05% in both the drug product and synthetic peptide.
Conclusion: This study shows that the same degradation-dependent impurities are likely to form in peptide drug products of biological or synthetic origin, while certain production process-dependent impurities can reach the reporting threshold and differ between peptides derived from different manufacturing processes. When developing generic peptide drugs, firms should consider developing sensitive and robust methods (i.e., LC-MS based) to identify differences in impurity profile between the generic and RLD. The peptide-related impurities would need to be tightly controlled during the manufacturing process. If these impurities were found in the final generic drug product at levels exceeding the recommended levels in the FDA Guidance (1), justifications and supporting data would need to be provided to demonstrate that they do not impact the safety and efficacy of the proposed generic product.