Safety and pharmacokinetics of panitumumab in Japanese patients with advanced solid tumors

Panitumumab is a fully human, monoclonal antibody against the epidermal growth factor receptor. Previous studies in non-Japanese patients with solid tumors showed that panitumumab exhibited nonlinear pharmacokinetics, was well tolerated (skin toxicities were the most common treatment-related adverse events), and had antitumor activity in some patients. This open-label, phase 1 study investigated panitumumab safety and pharmacokinetics in Japanese patients.

Japanese patients with advanced solid tumors were enrolled into one of three sequential panitumumab dose cohorts (cohort 1, 2.5 mg/kg weekly; cohort 2, 6.0 mg/kg every 2 weeks; and cohort 3, 9.0 mg/kg every 3 weeks) and received panitumumab until disease progression or drug intolerability. Safety endpoints included the incidence of adverse events, changes in laboratory values, and the appearance of anti-panitumumab antibodies. Serial pharmacokinetic samples were collected after the first and third doses of panitumumab. Tumors were assessed at week 8 and every 8 weeks thereafter.

Eighteen patients (6 per cohort) were enrolled. No dose-limiting toxicities, investigator-reported infusion reactions, or deaths occurred. Seven patients had grade-3/4 adverse events; fatigue and anorexia were most common. The most common skin toxicities were rash and acneiform dermatitis. No neutralizing anti-panitumumab antibodies were detected. Panitumumab exhibited nonlinear pharmacokinetics, and antitumor activity was observed in 31% (4/13) of the patients with colorectal cancer.

In Japanese patients with solid tumors, panitumumab was well tolerated, demonstrated pharmacokinetic and safety profiles similar to those observed previously in non-Japanese patients, and exhibited encouraging antitumor activity in patients with colorectal cancer.