Cobimetinib Plus Vemurafenib in Patients With Colorectal Cancer With <i>BRAF</i> Mutations: Results From the Targeted Agent and Profiling Utilization Registry (TAPUR) Study.

Abstract

TAPUR is a phase II basket trial evaluating the antitumor activity of commercially available targeted agents in patients with advanced cancer and genomic alterations known to be drug targets. The results of a cohort of patients with colorectal cancer (CRC) with <i>BRAF</i> mutations treated with cobimetinib (C) plus vemurafenib (V) are reported. Eligible patients had advanced CRC, no standard treatment options, measurable disease (RECIST), Eastern Cooperative Oncology Group performance status 0-2, adequate organ function, tumors with <i>BRAF</i> V600E/D/K/R mutations, and no <i>MAP2K1/2</i>, <i>MEK1/2</i>, or <i>NRAS</i> mutations. C was taken 60 mg orally once daily for 21 days followed by seven days off, and V was taken 960 mg orally twice daily. Simon's two-stage design was used with a primary study end point of objective response or stable disease of at least 16 weeks duration. Secondary end points were progression-free survival, overall survival, and safety. Thirty patients were enrolled from August 2016 to August 2018; all had CRC with a <i>BRAF</i> V600E mutation except one patient with a <i>BRAF</i> K601E mutation. Three patients were not evaluable for efficacy. Eight patients with partial responses and six patients with stable disease of at least 16 weeks duration were observed for disease control and objective response rates of 52% (95% CI, 35 to 65) and 30% (95% CI, 14 to 50), respectively. The null hypothesis of 15% disease control rate was rejected (<i>P</i> < .0001). Thirteen patients had at least one grade 3 adverse event or serious adverse event at least possibly related to C + V: anemia, decreased lymphocytes, dyspnea, diarrhea, elevated liver enzymes, fatigue, hypercalcemia, hypophosphatemia, rash, photosensitivity, and upper gastrointestinal hemorrhage. The combination of C + V has antitumor activity in heavily pretreated patients with CRC with <i>BRAF</i> mutations.