Phase II-I-II Study of Two Different Doses and Schedules of Pralatrexate, a High-Affinity Substrate for the Reduced Folate Carrier, in Patients With Relapsed or Refractory Lymphoma Reveals Marked Activity in T-Cell Malignancies

Abstract

Purpose: To determine the maximum-tolerated dose (MTD) and efficacy of pralatrexate in patients with lymphoma. Patients and Methods: Pralatrexate, initially given at a dose of 135 mg/m 2 on an every-other-week basis, was associated with stomatitis. A redesigned, weekly phase I/II study established an MTD of 30 mg/m 2 weekly for six weeks every 7 weeks. Patients were required to have relapsed/refractory disease, an absolute neutrophil greater than 1,000/μL, and a platelet count greater than 50,000/μL for the first dose of any cycle. Results: The every-other-week, phase II experience was associated with an increased risk of stomatitis and hematologic toxicity. On a weekly schedule, the MTD was 30 mg/m 2 weekly for 6 weeks every 7 weeks. This schedule modification resulted in a 50% reduction in the major hematologic toxicities and abrogation of the grades 3 to 4 stomatitis. Stomatitis was associated with elevated homocysteine and methylmalonic acid, which were reduced by folate and vitamin B12 supplementation. Of 48 assessable patients, the overall response rate was 31% (26% by intention to treat), including 17% who experienced complete remission (CR). When analyzed by lineage, the overall response rates were 10% and 54% in patients with B- and T-cell lymphomas, respectively. All eight patients who experienced CR had T-cell lymphoma, and four of the six patients with a partial remission were positron emission tomography negative. The duration of responses ranged from 3 to 26 months. Conclusion: Pralatrexate has significant single-agent activity in patients with relapsed/refractory T-cell lymphoma.