Atezolizumab (A) + cobimetinib (C) + vemurafenib (V) in BRAFV600-mutant metastatic melanoma (mel): Updated safety and clinical activity.

Abstract

3063 Background: Targeted inhibition of MEK with C and BRAF with V in BRAFV600-mutant mel can lead to both anticancer immune activation and direct tumor cell death. A, an anti–PD-L1 monoclonal antibody, inhibits PD-L1/PD-1 signaling. Combining C + V with A may enhance antitumor activity, potentially leading to improved clinical responses and durability. Preliminary data from this phase Ib study (NCT01656642) showed that A + C + V had a manageable safety profile and promising antitumor activity in patients (pts) with untreated BRAFV600-mutant unresectable/metastatic mel, with increases in CD8-positive T-cell infiltration observed after C + V (Sullivan et al SMR 2016). We present updated safety and efficacy data. Methods: Pts received A + C + V after a 28-day run-in with C + V. A was given at 800 mg q2w, C at 60 mg qd for the first 21 days of each 28-day cycle, and V at 960 mg bid during day 1–21 of run-in and 720 mg thereafter. Safety was evaluated in pts who had ≥1 dose of A; efficacy, in pts who had ≥1 dose of A by the data cutoff date and received ≥1 dose of A, C, or V by the dosed-by date. Results: Thirty-four patients were treated and evaluated for both safety and efficacy. Median survival follow-up was 7.1 months (range 2.5–19.9). Elevated AST/ALT, diarrhea, arthralgia, fatigue, photosensitivity, pyrexia, nausea, flu-like symptoms, maculopapular rash, and pruritus were reported as A- and/or C- and/or V-related in > 20% of pts at any grade (G). A/C/V-related G3–4 adverse events (AEs) were seen in 15 pts (44.1%) with the triple combination (none G5). Three serious AEs were A-related. All AEs were manageable and reversible. Elevated ALT/AST (three pts each) and rash (one pt) led to discontinuation of any drug. Unconfirmed RECIST V1.1 responses were observed in 29 pts (85.3%; six complete, 23 partial). Three pts with confirmed partial responses had resolution of target lesions. Twenty of the 29 responding patients continue to respond at the time of the data cutoff. Conclusions: Updated results confirm preliminary findings that A + C + V has a manageable safety profile and promising antitumor activity in pts with BRAFV600-mutant metastatic mel. Continued exploration of A + C + V is warranted. Clinical trial information: NCT01656642.