This two-part study evaluated trametinib, a MEK1/2 inhibitor, in combination with anticancer agents. Inhibition of MEK, a downstream effector of KRAS, demonstrated preclinical synergy with chemotherapy in KRAS-mutant NSCLC cell lines. Part 1 of this study identified recommended phase 2 doses of trametinib combinations. Part 2, reported herein, evaluated the safety, tolerability, pharmacokinetics, and efficacy of trametinib combinations in patients with NSCLC with and without KRAS mutations.Methods:
Phase 1b evaluated trametinib plus docetaxel with growth factor support (trametinib, 2.0 mg once daily, and docetaxel, 75 mg/m2 every 3 weeks) or pemetrexed (trametinib, 1.5 mg once daily, and pemetrexed, 500 mg/m2 every 3 weeks). Eligibility criteria for the expansion cohorts included metastatic NSCLC with measurable disease, known KRAS mutation status, Eastern Cooperative Oncology Group performance status of 1 or lower, and no more than two prior regimens.Results:
The primary end point of overall response rate (ORR) was met for both combinations. A confirmed partial response (PR) was observed in 10 of the 47 patients with NSCLC who received trametinib plus docetaxel (21%). The ORR was 18% (four PRs in 22 patients) in those with KRAS wild-type NSCLC versus 24% (six PRs in 25 patients) in those with KRAS-mutant NSCLC. Of the 42 patients with NSCLC treated with trametinib plus pemetrexed, six (14%) had a PR; the ORR was 17% (four of 23) in patients with KRAS-mutated NSCLC versus 11% (two of 19) in KRAS wild-type NSCLC. Adverse events—most commonly diarrhea, nausea, and fatigue—were manageable.Conclusions:
Trametinib-plus-chemotherapy combinations were tolerable. Clinical activity exceeding the ORRs previously reported with docetaxel or pemetrexed alone in KRAS-mutated NSCLC and meeting prespecified criteria was observed.