UCSF

Previous estimates of the likelihood of a drug tested in phase I trials obtaining FDA clearance are out of date. In the intervening years, newer pharmaceuticals have been developed, resulting in new delivery systems and lines of therapies. We sought to explore and update these estimates by comprehensively searching drugs tested in phase I trials and to determine the factors associated with later receiving FDA approval. In a cross-sectional analysis, we searched for anti-tumor drugs tested in phase I trials and published in scientific journals or presented at hematology/oncology conferences. For each drug, we searched PubMed for phase II and phase III studies testing the drug for the same indication tested in phase I studies. We found 51 drug approvals; four were withdrawn. The probability of a drug tested in 2015 being approved by 2021 was 6.2%. Drugs tested as monotherapy were more likely to receive approval than drugs tested in combination, and monoclonal antibodies were more likely to receive approval than drugs of other mechanisms. In adjusted models, response rates higher than 40% in phase I studies, demonstrating an improvement in overall survival (OS) in phase III studies, and drugs tested as monotherapy were associated with receiving FDA approval. When looking at all drugs tested during a single year, most drugs were not approved, and among those that are approved, almost 8% are withdrawn. Response rates higher than 40%, testing a drug as monotherapy, and demonstrating an improvement in OS were associated with receiving FDA approval.