A Study of Vemurafenib and GDC-0973 (Cobimetinib) in Participants With BRAFV600E Mutation-Positive Metastatic Melanoma

DLT is defined as 1 of the following toxicities considered by the investigator to be related to study treatment: a) Grade 3 nausea, vomiting or diarrhea that resolved to Grade less than or equal to (≤) 1 within 7 days, b) Grade 3 rash or photosensitivity that resolved to Grade ≤2 within 7 days, c) Grade 3 cutaneous squamous cell carcinoma (cuSCC) that was subsequently resected, d) Grade greater than or equal to (≥) 3 fatigue or hyperuricemia that resolved to Grade ≤2 within 7 days, e) Grade 3 fever, f) Grade 3 or 4 elevation of serum creatine phosphokinase (CPK) levels, which is asymptomatic, deemed by the investigator to be clinically insignificant and that returned to Grade ≤2 during the 14-day cobimetinib treatment holiday, g) Grade ≥3 febrile neutropenia, h) Grade ≥4 neutropenia (absolute neutrophil count [ANC] less than <500/microliter [μL]), i) Grade ≥4 thrombocytopenia, j) Grade ≥4 anemia, k) Grade ≥3 elevation of total bilirubin, hepatic transaminase or alkaline phosphatase.

The highest dose level(s) at which fewer than one-third of participants experienced a DLT was declared the MTD. DLT is defined as 1 of the following toxicities considered by the investigator to be related to study treatment: a) Grade 3 nausea, vomiting or diarrhea that resolved to Grade ≤1 within 7 days, b) Grade 3 rash/photosensitivity that resolved to Grade ≤2 within 7 days, c) Grade 3 cuSCC that was subsequently resected, d) Grade ≥3 fatigue/hyperuricemia that resolved to Grade ≤2 within 7 days, e) Grade 3 fever, f) Grade 3 or 4 elevation of serum CPK levels, which is asymptomatic, deemed to be clinically insignificant and returns to Grade ≤2 during the 14-day cobimetinib treatment holiday, g) Grade ≥3 febrile neutropenia, h) Grade ≥4 neutropenia (ANC <500/ μL), i) Grade ≥4 thrombocytopenia, j) Grade ≥4 anemia, k) Grade ≥3 elevation of total bilirubin, hepatic transaminase or alkaline phosphatase.

Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes.

Tumor response of CR or PR is considered as objective response. CR: disappearance of all target lesions, reduction in short axis <10 millimeters in pathological lymph nodes (target and non-target lesions); PR: at least a 30 percent (%) decrease in the sum of the longest diameter of target lesions, taking as reference the baseline sum longest diameter. Responses were confirmed by repeat assessments ≥4 weeks after initial documentation.

Progressive disease (PD) according to RECIST V 1.1: at least a 20% increase in the sum of the longest diameter of target lesions, taking as reference the smallest sum on study (nadir), including baseline; in addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of at least 5 mm; appearance of 1 or more lesions is also considered as progression.

Duration of response, defined as the time from first occurrence of a documented objective response until the time of disease progression, as determined by investigator review of tumor assessments using RECIST v 1.1, or death from any cause during the study (that is within 30 days after the last dose of study treatment).

OS was defined as the time from the date of randomization to the date of death due to any cause. Participants were censored at the last date of tumor measurement, the last date in the study drug log, or the date of last follow-up. OS analyzed using Kaplan-Meier estimate.

The pharmacodynamic effect of cobimetinib in combination with vemurafenib was assessed by measuring changes in FDG uptake as characterized by the lean body mass corrected (LBM) maximum standardized uptake value (SUV max) measurement using FDG-PET. Post-baseline timepoint Cycle 1 was averaged between Days 10 to 14 and Cycle 2 for Days 14+7.

Changes in effector molecules of the MAPK pathway that are directly or indirectly affected by BRAF and MEK inhibition (including but not limited to ERK and phosphorylated ERK and MEK) by IHC using biopsies at baseline, between Days 10-14 of Cycle 1, and at disease progression. IHC is a staining process performed on fresh/frozen tumor tissue samples.