Comparison of 2 Doses of Intravenous (IV) Temsirolimus (Temsr) in Patients with Relapsed/Refractory Mantle Cell Lymphoma (MCL)

Introduction: Temsr (Torisel^®) administered at 175 mg IV once weekly for first 3 weeks, followed by 75mg IV once weekly (Temsr 175/75 mg) is approved in the European Union for the treatment of adult patients with relapsed and/or refractory MCL based on an overall positive benefit-risk relationship demonstrated for this treatment regimen in the pivotal phase III study (Hess et al. J Clin Oncol. 2009;27:3822-9). This ongoing phase 4, multicenter, randomized, open-label study was conducted to explore whether similar efficacy can be achieved for the treatment of patients with relapsed/refractory MCL with a Temsr regimen that is expected to yield fewer side effects than the Temsr 175/75 mg dose regimen, by skipping the first 3 doses of Temsr 175 (Clinicatrials.gov: NCT01180049).

Methods: In this study, previously treated (2-7 lines of prior therapy) patients with relapsed/refractory mantle cell lymphoma were stratified by the histologic subtype (blastoid vs. non blastoid vs unknown histology) and randomized (1:1) to receive Temsr 175/75 mg, or 75mg IV once weekly (Temsr 75 mg). Treatment continued until disease progression, provided that patients were tolerating treatment and achieving clinical benefit. The primary endpoint was progression-free survival (PFS) based on independent assessment. Secondary endpoints included objective response rate (ORR), overall survival (OS) and safety with a particular focus on bleeding- and infection-related adverse events (AEs).

Results: Of the 90 patients (77.8% males; 93.3% white, mean age 66.6 years) randomized, 47 were treated with Temsr 175/75 mg, 42 were treated with Temsr 75 mg, and 1 patient was randomized but not treated. At the cutoff date for analysis (November 12, 2015), 39 (83.0%) patients in Temsr 175/75 mg arm and 41 (95.3%) patients in Temsr 75 mg arm discontinued treatment with the primary reason being objective disease progression (53.8% in Temsr 175/75 mg and 56.1% in Temsr 75 mg). Median duration of treatment was comparable in the Temsr 175/75 mg arm and Temsr 75 mg arm (3.2 vs. 3.1 months). Median PFS (80% CI) was 4.3 (3.3-6.4) months in Temsr 175/75 mg arm versus 4.5 (2.7-4.9) months in Temsr 75 mg arm (hazard ratio [HR] 0.731; 80% CI 0.520-1.027). ORR (80% CI) was 27.7% (19.1%-37.7%) in Temsr 175/75 mg arm versus 20.9% (13.0%-31.0%) in Temsr 75 mg arm. Median OS (80% CI) was 18.7 (7.5-48.2) months in Temsr 175/75 mg arm versus 11.0 (6.3-16.2) months in Temsr 75 mg arm (HR 0.681, 80% CI 0.472-0.982). Median duration of response was comparable in both treatment arms (9.0 vs. 8.7 months in Temsr 175/75 mg and Temsr 75 mg arms, respectively). Overall, the safety profile was comparable in both treatment arms, although the number of patients with serious AEs, dose reduction and deaths was lower in the 175/75mg arm compared with 75 mg arm (57.4%, 48.9% and 48.9% vs. 73.8%, 64.3% and 65.1%, respectively), and the number of treatment discontinuations due to AEs was higher in the Temsr 175/75mg arm compared with 75mg arm (19.1% vs. 14.3%). Common (>10%) grade ≥3, all-causality, treatment-emergent AEs in the Temsr 175/75 mg arm and Temsr 75 mg arm, respectively, were thrombocytopenia (46.8% vs. 38.1%), neutropenia (25.5% vs. 21.4%), and pneumonia (10.6% vs. 19.0%). Treatment-emergent bleeding-related grade ≥2 AEs in the Temsr 175/75 mg arm and Temsr 75 mg arm, respectively, included epistaxis (10.6% vs. 2.4%) and ecchymosis (2.1% vs. 0). Only 1 grade 3 AE of epistaxis which was not related to Temsr was reported in the Temsr 175/75 arm, and no grade 3 events were reported in Temsr 75 arm. Pneumonia was the most commonly occurring treatment-emergent infection-related grade ≥2 AEs 12.8% in Temsr 175/75 mg arm and 19.0% in Temsr 75 mg arm. Of the 51 deaths reported during the study, none were treatment-related and most were due to disease progression.

Conclusions: Overall, PFS, ORR and OS favored the Temsr 175/75 arm, although no formal statistical conclusions were made as the study was not powered for differences. The safety profile in both study arms was comparable, but there was a lower incidence of serious AEs, dose reductions and deaths in the 175/75 mg arm. Temsr 175/75 mg remains the preferred dose regimen for patients with relapsed/refractory MCL.