In vitro studies in mantle cell lymphoma (MCL) cell lines and patient‐derived cells have demonstrated synergistic apoptosis with combined rituximab and bortezomib (R‐bortezomib) compared with single‐agent bortezomib. Therefore, the authors of this report evaluated R‐bortezomib in a preclinical model and in a phase 2 clinical trial.

A Hu‐MCL‐severe combined immunodeficiency (SCID) model engrafted with the Jeko cell line was treated with R‐bortezomib, bortezomib, or rituximab. Twenty‐five patients with relapsed follicular lymphoma (n = 11) and MCL (n = 14) received 375 mg/m² rituximab on Days 1 and 8 and 1.3 to 1.5 mg/m² bortezomib on Days 1, 4, 8, and 11 every 21 days for a median of 3 cycles (range, 1‐5 cycles).

R‐bortezomib resulted in a statistically significant improvement in overall survival in Hu‐MCL‐SCID mice. In the clinical trial, the overall response rate was 40% in all 25 patients, 55% in patients with follicular lymphoma, and 29% in patients with MCL. The estimated 2‐year progression‐free survival (PFS) rate was 24% (95% confidence interval [CI], 10%‐53%) in all patients and 60% (95% CI, 20%‐85%) in responding patients. Thirteen patients (52%) developed grade 3 neurotoxicity, which consisted of constipation/ileus, sensory or motor neuropathy, or orthostatic hypotension. Patients who were heterozygous for the CD32a (Fcγ receptor IIa) 131 histidine (H) to arginine (R) polymorphism had a significantly decreased PFS (P = .009) after R‐bortezomib compared with HH and RR homozygotes.

R‐bortezomib had significant activity in patients with relapsed or refractory follicular lymphoma and MCL, although an unexpectedly high incidence of grade 3 neurologic toxicity was a potential limiting factor with this combination. Cancer 2011. © 2010 American Cancer Society.