Safety and tolerability of selumetinib as a monotherapy, or in combination with docetaxel as second-line therapy, in Japanese patients with advanced solid malignancies or non-small cell lung cancer.

Objective: This Phase I study (NCT01605916) investigated the safety, tolerability and pharmacokinetic profile of selumetinib plus docetaxel as second-line therapy in Japanese patients with locally advanced or metastatic non-small cell lung cancer (NSCLC), or selumetinib monotherapy in Japanese patients with advanced solid malignancies.

Methods: All enrolled patients received single-dose selumetinib 25, 50 or 75 mg, followed by a 3-day washout. Combination therapy cohorts then started a 21-day cycle of docetaxel 60 mg/m2 plus selumetinib 25 or 75 mg twice-daily (BID) on Day 1. Thereafter, selumetinib BID continued for 20 days; patients received ≤6 cycles. Following single-dosing, monotherapy cohorts underwent a 21-day cycle of selumetinib 25, 50 or 75 mg BID.

Results: Thirty-three patients were enrolled and 25 assigned to treatment (combination, n = 8; monotherapy, n = 17). Most frequent adverse events (AEs) included: vomiting, decreased appetite, diarrhea, nausea and stomatitis (combination cohorts); gastrointestinal disorders, skin and subcutaneous tissue disorders (monotherapy cohorts). Grade 3 dose-limiting toxicities: febrile neutropenia, causally related to combination therapy (n = 3); pneumonitis, selumetinib 50 mg monotherapy (n = 1). Selumetinib 75 mg monotherapy and selumetinib 25 mg plus docetaxel 60 mg/m2 were tolerated; selumetinib 75 mg plus docetaxel 60 mg/m2 was not tolerated. Selumetinib pharmacokinetic profile was similar when administered as a monotherapy or in combination with docetaxel.

Conclusions: Selumetinib 75 mg monotherapy was tolerated in Japanese patients with NSCLC. Due to the overall selumetinib AE profile, the maximum tolerated dose was not determined for combination therapy or monotherapy. Selumetinib 75 mg BID plus docetaxel 60 mg/m2 was not tolerated in this patient population.