Phase I Trial of Rituximab, Cladribine and Temsirolimus (RCT) for Initial Therapy of Mantle Cell Lymphoma

We conducted this trial to determine the maximum tolerated dose (MTD) and schedule of temsirolimus added to an established regimen comprised of rituximab and cladribine for the initial treatment of mantle cell lymphoma and to generate preliminary information on the toxicity and efficacy of this combination.

A standard phase I cohort of 3 study design was utilized. MTD was defined as the dose level below the lowest dose that induces dose-limiting toxicity (DLT) in at least one-third of patients (at least 2 of a maximum of 6 new patients). DLT was defined as grade 4 ANC (<500) for ≥5 days, grade 4 ANC (<500) associated with fever (>100.5 F) and/or active infection, PLT <25,000, grade 4 infection, or ≥grade 3 non-hematologic toxicity during the first cycle of therapy as per NCI Common Terminology Criteria for Adverse Events v3.0. The fixed doses of rituximab and cladribine were 375 mg/m² IV day 1 and 5 mg/m²/d IV days 1–5 of a 28 day cycle, respectively, as previously published. There were 5 planned temsirolimus IV 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. The fifth dose level is as previously published in combination with rituximab.

A total of 17 patients were treated: 3 each at dose levels 1–4 and 5 at dose level 5 (25 mg temsirolimus days 1,8,15, and 22). The median age was 75 years (52–86). There were 11 males and 6 females. At presentation 88% had stage IV disease, and 94% had extranodal disease. MIPI scores were low in 6% (1 patient), intermediate in 59% (10 patients), and high in 35% (6 patients). There was a single DLT recorded at dose level 3 based on the initial DLT criteria, though this cytokine release syndrome was clearly rituximab related, and occurred prior to the first dose of temsirolimus. Five patients were treated at the highest planned temsirolimus dose level (25 mg days 1,8,15, and 22) with no DLT observed. No further dose escalation was planned, and this level was determined to be tolerated, though higher levels may be tolerable. All patients were evaluable for adverse events. Hematologic toxicity was frequent, with grade 3 anemia in 12% of patients, grade 3 thrombocytopenia in 35%, grade 4 thrombocytopenia in 30%, grade 4 lymphopenia in 47%, grade 3 neutropenia in 24%, and grade 4 neutropenia in 18% of patients. There were 3 thrombotic episodes, 2 of which were attributed to therapy, and 3 episodes of pneumonitis. The overall response rate was 94% with 53% CR and 41% PR. The median progression free survival was 18.7 months.

Temsirolimus 25 mg IV weekly may be safely added to rituximab and cladribine at 375 mg/m² IV day 1 and 5 mg/m²/d IV 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.

Off Label Use: Temsirolimus for mantle cell lymphoma.