Development of Tissue-Agnostic Treatments for Patients with Cancer

In 2017 the FDA (US Food and Drug Administration) approved pembrolizumab, a programmed death 1 (PD-1) inhibitor, for the treatment of unresectable or metastatic, microsatellite instability–high (MSI-H) or mismatch repair–deficient (dMMR) solid tumors, regardless of tumor site or histology. This represented the first approval based on the identification of a biomarker and independent of tumor site. Although this approach may intuitively appear rational, tissue-agnostic drug development can be complicated by tumor-specific resistance mechanisms or other factors that can alter a drug's effect. Inherent with the tissue-agnostic approach is the fact that there may be residual uncertainty concerning a drug's effect in unstudied tumor types (e.g., at the time of approval). However, this approach may be the only available mechanism to support approval and provide access to a drug that is indicated for the treatment of patients with certain rare biomarker-positive cancers.