Background: Trametinib is an inhibitor of MEK1/MEK2 activation and kinase activity. In order to evaluate the safety, tolerability, pharmacokinetics, and preliminary efficacy of single-agent trametinib (part 1) and trametinib in combination with gemcitabine (part 2), we undertook the first clinical study of this combination in Japanese patients with cancer and herein report our results.
Methods: In part 1, 13 patients with advanced solid tumors were enrolled into 3 dose cohorts, receiving trametinib once daily at a dose of 1.0, 2.0, or 3.0 mg. In part 2, 5 patients with pancreatic cancer received trametinib (2.0 mg once daily) in combination with gemcitabine (1000 mg/m(2)).
Results: In part 1, a dose-limiting toxicity was observed in a patient in the 2.0-mg dose cohort, but the maximum tolerated dose was not reached at doses up to 3.0 mg daily. The best overall response was a PR in 1 patient, and 6 patients had SD. In part 2, the combination of trametinib and gemcitabine was tolerated for a short period of time. However, serious interstitial lung disease (ILD) was observed in 3 of 5 patients 4 weeks or more after the start of the treatment, including 1 fatal case. Three patients achieved a PR, and 2 patients had SD. The most common adverse event was rash (85 % in part 1 and 100 % in part 2).
Conclusions: Trametinib monotherapy was tolerable in Japanese patients with cancer. However, the combination of trametinib plus gemcitabine carried a higher risk as compared with monotherapy, during which no ILD was observed. (ClinicalTrials.gov number, NCT01324258.).
Keywords: Gemcitabine; Japanese; MEK inhibitor; Pancreatic cancer; Solid tumors; Trametinib.