Dr. Graff on Results of the KEYNOTE-199 Trial in mCRPC

Julie N. Graff, MD, associate professor of medicine, Oregon Health & Science University Knight Cancer Institute, discusses the results of the phase II KEYNOTE-199 trial in metastatic castration-resistant prostate cancer (mCRPC).

At the 2020 Genitourinary Cancers Symposium, findings from cohort 4 (n = 81) and cohort 5 (n = 45) of the KEYNOTE-199 trial were presented. In both cohorts, patients with enzalutamide (Xtandi)-resistant mCRPC received the combination of pembrolizumab (Keytruda) and enzalutamide (Xtandi). Notably, cohort 4 consisted of patients with measurable RECIST mCRPC, whereas cohort 5 enrolled patients with nonmeasurable RECIST bone-only/bone-predominant mCRPC.

A 12% overall response rate defined as ≥30% reduction in tumor size was reported in cohort 4. The disease-control rate (DCR) was 51%, and the duration of response was 6.3 months. The DCR in cohort 5 was 51%.

Radiographic progression-free survival was 4.2 months in cohort 4 and 4.4 months in cohort 5. Overall survival was not reached in cohort 4 and was 18.8 months in cohort 5.

Overall, 40% of patients had a prostate-specific antigen (PSA) decline from baseline. Notably, 14% of patients experienced a PSA decline ≥50%.

The combination is currently being evaluated in the phase III KEYNOTE-641 trial.