Exploration of a Novel Intermediate Response Endpoint in Immunotherapy Clinical Studies

Purpose: Both objective response rate (ORR) and progression-free survival as defined by RECIST are weakly associated with overall survival (OS) in trials evaluating immunotherapy drug products. We proposed a novel intermediate response endpoint (IME) for evaluating immunotherapies.Experimental Design: We defined IME response as having no nontarget lesion progression, no new lesion appearance, and reaching a target lesion response determined by baseline tumor burden, tumor reduction depth, and tumor change dynamics within one year after randomization. Database used consisted of data from randomized active-controlled immunotherapy trials. Criterion for IME was developed on the basis of patient-level data from a training dataset, and further evaluated using an independent testing dataset. A patient-level responder analysis comparing OS between patients with and without an IME response was conducted using combined data. Association between trial-level OS hazard ratio (HR) and IME odds ratio (OR) was analyzed using a weighted linear regression model.Results: A total of 5,806 patients from 9 randomized studies were included in the database. At patient level, patients with IME response had improved OS compared with nonresponders (HR = 0.09). At trial level, association between OS and IME was moderate (R² = 0.68).Conclusions: The IME was moderately associated with OS, and the association appeared to be stronger than the association observed between RECIST-defined ORR and OS. However, the analyses conducted in this research are exploratory and further evaluation is needed before using this endpoint in future studies. Clin Cancer Res; 24(10); 2262-7. ©2017 AACR.