A Phase I Single-Agent Study of Twice-Weekly Consecutive-Day Dosing of the Proteasome Inhibitor Carfilzomib in Patients with Relapsed or Refractory Multiple Myeloma or Lymphoma

Carfilzomib is a next-generation, selective, proteasome inhibitor with clinical activity in relapsed and/or refractory multiple myeloma. The objectives of this phase I study were to establish the safety, tolerability, pharmacokinetic, and pharmacodynamic profiles of escalating doses of carfilzomib in patients with relapsed or refractory hematologic malignancies. Carfilzomib (doses ranging from 1.2-27 mg/m(2)) was administered i.v. on 2 consecutive days for 3 weeks of a 4-week cycle. Single-agent dose escalation (n = 37) was followed by a dose-expansion phase (n = 11) that comprised 2 cohorts (carfilzomib or carfilzomib + dexamethasone). During dose expansion, carfilzomib was administered starting with 20 mg/m(2) during the first week (days 1, 2) and then escalated to 27 mg/m(2) thereafter. A maximum tolerated dose (MTD) was not reached during dose escalation. Dosing in the expansion cohort was well tolerated. Adverse events were manageable and primarily of grade I or II. The main hematologic adverse events of ≥ grade III were anemia and thrombocytopenia. Notably, there were no observations of grade III or more peripheral neuropathy. Carfilzomib was cleared rapidly with an elimination half-life of less than 30 minutes but still induced dose-dependent inhibition of the 20S chymotrypsin-like proteasome activity. At doses of 15 to 27 mg/m(2), there was evidence of activity among patients with multiple myeloma and with non-Hodgkin lymphoma. Escalated dosing of carfilzomib on a schedule of 2 consecutive days for 3 weeks of a 4-week cycle was tolerable and showed promising activity. This dose regimen has been selected for ongoing and future clinical studies, including PX-171-003A1 and the pivotal trial ASPIRE.