Pharmacokinetic Analysis and Phase 1 Study of MRX-1024 in Patients Treated with Radiation Therapy with or without Cisplatinum for Head and Neck Cancer

Purpose: A previous study reported radiation protection from mucosal injury with D-methionine (D-met) in preclinical evaluation; therefore, the pharmacokinetics, safety, and utility of D-met were evaluated clinically. Experimental Design: The pharmacokinetics of D-met following oral administration of a bioavailable formulation (MRX-1024) was evaluated in normal volunteers. Subsequently, 25 patients were enrolled on a phase 1 study of MRX-1024 concurrent with radiation therapy (RT) with or without weekly cisplatinum. Toxicity and mucosal events were evaluated weekly. Results: Oral MRX-1024 resulted in rapid and dose-dependent increases in plasma D-met concentrations with a half-life of 3 hours. When administered concurrent with RT without chemotherapy, it was associated with a modest increase in grade 2 (two of six patients) and grade 3 (one of six patients) emesis. In those treated with MRX-1024 along with RT and weekly cisplatinum, there was no appreciable increase in emesis. Overall, five patients withdrew from the study due to emesis (four grade 2 and one grade 3). Only one incidence of dose-limiting toxicity (grade 3 emesis) was identified in 25 patients (4%). Finally, in 18 evaluable patients treated with MRX-1024 at 100 mg/kg twice daily (BID), the incidence of severe (grade 3) oral mucositis was 6% (1 of 18) with no grade 4 mucositis. Conclusions: There is a dose-dependent increase in D-met exposure following MRX-1024 administration at 50 and 100 mg/kg, and MRX-1024 is safe for use concurrent with combined radiation and chemotherapy. The observed rate of mucositis seems less than that for similar treatment regimens within the published literature. Clin Cancer Res; 16(9); 2666-76. (C) 2010 AACR.