Phase I trial of rituximab, cladribine, and temsirolimus (RCT) for initial therapy of mantle cell lymphoma

Background: We conducted this trial to determine the maximum tolerated dose (MTD) of temsirolimus added to an established regimen comprised of rituximab and cladribine for the initial treatment of mantle cell lymphoma. Patients and methods: A standard phase I cohort of three study design was utilized. The fixed doses of rituximab and cladribine were 375 mg/m² i.v. day 1 and 5 mg/m²/day i.v. days 1-5 of a 28-day cycle, respectively. There were five planned temsirolimus i.v. dose levels: 15 mg day 1; 25 mg day 1; 25 mg days 1 and 15; 25 mg days 1, 8 and 15; and 25 mg days 1, 8, 15, and 22. Results: Seventeen patients were treated: three each at levels 1-4 and five at dose level 5. The median age was 75 years (52-86 years). Mantle Cell International Prognostic Index (MIPI) scores were low in 6% (1), intermediate in 59% (10), and high in 35% (6) of patients. Five patients were treated at level 5 without dose limiting toxicity. Hematologic toxicity was frequent: grade 3 anemia in 12%, grade 3 thrombocytopenia in 41%, grade 4 thrombocytopenia in 24%, grade 3 neutropenia in 6%, and grade 4 neutropenia in 18% of patients. The overall response rate (ORR) was 94% with 53% complete response and 41% partial response. The median progression-free survival was 18.7 months. Conclusions: Temsirolimus 25 mg i.v. weekly may be safely added to rituximab and cladribine at 375 mg/m² i.v. day 1 and 5 mg/m²/day i.v. days 1-5 of a 28-day cycle, respectively. This regimen had promising preliminary activity in an elderly cohort of patients with mantle cell lymphoma.