Cobimetinib combined with vemurafenib in advanced BRAFV600-mutant melanoma (coBRIM): updated efficacy results from a randomised, double-blind, phase 3 trial

Background The combination of cobimetinib with vemurafenib improves progression-free survival compared with placebo and vemurafenib in previously untreated patients with BRAFV600-mutant advanced melanoma, as previously reported in the coBRIM study. In this Article, we report updated efficacy results, including overall survival and safety after longer follow-up, and selected biomarker correlative studies. Methods In this double-blind, randomised, placebo-controlled, multicentre study, adult patients (aged >= 18 years) with histologically confirmed BRAFV600 mutation-positive unresectable stage IIIC or stage IV melanoma were randomly assigned (1: 1) using an interactive response system to receive cobimetinib (60 mg once daily for 21 days followed by a 7-day rest period in each 28-day cycle) or placebo, in combination with oral vemurafenib (960 mg twice daily). Progression-free and overall survival were primary and secondary endpoints, respectively; all analyses were done on the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT01689519, and is ongoing but no longer recruiting participants. Findings Between Jan 8, 2013, and Jan 31, 2014, 495 eligible adult patients were enrolled and randomly assigned to the cobimetinib plus vemurafenib group (n=247) or placebo plus vemurafenib group (n=248). At a median follow-up of 14.2 months (IQR 8.5-17.3), the updated investigator-assessed median progression-free survival was 12.3 months (95% CI 9.5-13.4) for cobimetinib and vemurafenib versus 7.2 months (5.6-7.5) for placebo and vemurafenib (HR 0.58 [95% CI 0.46-0.72], p<0.0001). The final analysis for overall survival occurred when 255 (52%) patients had died (Aug 28, 2015). Median overall survival was 22.3 months (95% CI 20.3-not estimable) for cobimetinib and vemurafenib versus 17.4 months (95% CI 15.0-19.8) for placebo and vemurafenib (HR 0.70, 95% CI 0.55-0.90; p=0.005). The safety profile for cobimetinib and vemurafenib was tolerable and manageable, and no new safety signals were observed with longer follow-up. The most common grade 3-4 adverse events occurring at a higher frequency in patients in the cobimetinib and vemurafenib group compared with the vemurafenib group were.-glutamyl transferase increase (36 [15%] in the cobimetinib and vemurafenib group vs 25 [10%] in the placebo and vemurafenib group), blood creatine phosphokinase increase (30 [12%] vs one [<1%]), and alanine transaminase increase (28 [11%] vs 15 [6%]). Serious adverse events occurred in 92 patients (37%) in the cobimetinib and vemurafenib group and 69 patients (28%) in the vemurafenib group. Pyrexia (six patients [2%]) and dehydration (five patients [2%]) were the most common serious adverse events reported in the cobimetinib and vemurafenib group. A total of 259 patients have died: 117 (47%) in the cobimetinib and vemurafenib group and 142 (58%) in the vemurafenib group. The primary cause of death was disease progression in most patients: 109 (93%) of 117 in the cobimetinib and vemurafenib group and 133 (94%) of 142 in the vemurafenib group. Interpretation These data confirm the clinical benefit of cobimetinib combined with vemurafenib and support the use of the combination as a standard first-line approach to improve survival in patients with advanced BRAFV600-mutant melanoma.