Patients with relapsed or refractory mantle cell lymphoma (MCL) who were previously treated with Bruton’s tyrosine kinase (BTK) inhibitor therapy achieved high rates of complete response (CR) when treated with a doublet regimen of fixed-duration subcutaneous (SC) mosunetuzumab plus polatuzumab vedotin (M-Pola), according to an ongoing phase Ib/II trial.
“CRs were observed early and persisted during the follow up period,” wrote the authors, led by Michael Wang, MD, of the University of Texas MD Anderson Cancer Center in Houston.
By the preliminary data cutoff of October 27, 2022, a total of 20 patients had been treated with M-Pola, of which one completed treatment, nine discontinued mosunetuzumab, and 10 were still undergoing treatment.
The cohort had a median age of 68 years (range, 44-82), was 75% male, 95% had Ann Arbor stage III/IV disease, and 40% had a MCL International Prognostic Index score of six or more at baseline. The median number of prior lines of therapy was three (range, 2-9), including BTK inhibitors in all patients and chimeric antigen receptor (CAR) T-cell therapy in seven (35%).
Treatment response was assessed based on Lugano 2014 criteria. Researchers reported the overall response rate (ORR) was 75% with a CR rate of 70%, and that ORR and CR rates were “generally consistent” in high-risk subgroups. The median duration of CR was not evaluable (NE; 95% CI, 3.8-NE)
The most common treatment-related adverse events (AEs) occurring in at least 25% of all patients were cytokine release syndrome (CRS) in 50%, injection site reaction in 50%, fatigue in 40%, dyspnea in 35%, paresthesia in 30%, diarrhea in 30%, myalgia in 30%, infusion-related reactions in 25%, and nausea in 25%. Of the ten CRS events, nine were grade 1 and one was grade 2. The authors noted all events had been resolved by the data cutoff date.
Overall, Dr. Wang and colleagues suggested that the doublet therapy “induced high CR rates” and had “had a manageable safety profile” in patients with relapsed or refractory MCL with prior BTK inhibitor therapy and those who had also received prior CAR T-cell therapy.
Reference
Wang M, Assouline S, Kamdar M, et al. Fixed duration mosunetuzumab plus polatuzumab vedotin has promising efficacy and a manageable safety profile in patients with BTKi relapsed/refractory mantle cell lymphoma: initial results from a phase Ib/II study. Abstract #734. Presented at the 65th ASH Annual Meeting and Exposition; December 9-12, 2023; San Diego, California.