Vemurafenib in metastatic melanoma patients with brain metastases: an open-label, single-arm, phase 2, multicentre study

Background: Vemurafenib has shown activity in patients with BRAF^V600 mutated melanoma with brain metastases (BM). This phase 2 study evaluated vemurafenib in patients with/without prior treatment for BM. Methods: Patients with BRAF^V600 mutated melanoma with BM were enrolled into cohort 1 (previously untreated BM) and cohort 2 (previously treated BM) and received vemurafenib (960mg BID) until disease progression (PD) or intolerance. Primary endpoint was best overall response rate (BORR) in the brain in cohort 1 that was evaluated using modified RECIST 1.1 criteria using lesions≥ 0.5 cm to assess response. Results: 146 patients were treated (cohort 1 n=90; cohort 2 n=56), 62% of whom were male. Median (range) time since diagnosis of BM: 1.0 (0-9) month in cohort 1 and 4.2 (1-68) months in cohort 2. Median duration of treatment was 4.1 months (range 0.3-34.5) in cohort 1 and 4.1 months (range 0.2-27.6) in cohort 2. Intracranial BORR in cohort 1 by an independent review committee (IRC) was 18% (2 CRs, 14 PRs). Extracranial BORR by IRC was 33% in cohort 1 and 23% in cohort 2. Median PFS (brain only, investigator-assessed) was 3.7 months (range 0.03-33.4; IQR 1.9-5.6) in cohort 1 and 4.0 months (range 0.3-27.4; IQR 2.2- 7.4) in cohort 2. Median OS was 8.9 months (range 0.6-34.5; IQR 4.9-17.0) in cohort 1 and 9.6 months (range 0.7-34.3; IQR 4.5- 18.4) in cohort 2. Adverse events (AEs) were similar in type, grade and frequency to other studies of single-agent vemurafenib. Grade 3/4 AEs occurred in 59 (66%) patients in cohort 1 and 36 (64%) in cohort 2. Overall, 84% of patients died during the study (86% in cohort 1 and 80% in cohort 2), mainly due to disease progression. Conclusions: The study demonstrates clinically meaningful response rates of melanoma BM to vemurafenib, which was well tolerated and without significant CNS toxicity.