Analysis of Drug Development Paradigms for Immune Checkpoint inhibitors

Immune checkpoint inhibitors have unique toxicities and response kinetics compared to cytotoxics and gene-targeted anti-cancer agents. We investigated the impact of innovative/accelerated immunotherapy drug development/approval models on the accuracy of safety and efficacy assessments by searching the US Food and Drug Administration (FDA) website. Initial phase I trials for each agent were reviewed and safety and efficacy data compared to that found in later trials leading to regulatory approvals of the same agents. As of June 2017, the FDA approved six checkpoint inhibitors for a variety of cancer types. All checkpoint inhibitors received a priority review status and access to at least two additional FDA special access programs, more often breakthrough designation and accelerated approval. Median clinical development time (investigational new drug application to approval) was 60.77 months (avelumab had the shortest timeline (52.33 months)). Response rates during early phase I trials (median =16%) are higher than for phase I trials of other agents (with the exception of gene-targeted agents tested with a biomarker). Doses approved were usually not identical to doses recommended on phase I trials. Approximately 50% of types of immune-related and 43% of types of clinically relevant toxicities from later trials were identified in early phase trials. Even so, treatment-related mortality remains exceedingly low in later studies (0.33% of patients). In conclusion, efficacy and safety of immune checkpoint inhibitors appear to be reasonably predicted from the dose-finding portion of phase I trials, indicating that the fast-track development of these agents is safe and justified.

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