Abstract
Mosunetuzumab is a novel bispecific antibody targeting epitopes on CD3 on T cells and CD20 on B cells with the goal of inducing T-cell mediated elimination of malignant B cells. A recent pivotal phase I/II clinical trial (GO29781) demonstrated that mosunetuzumab induced an overall response rate of 80%, complete response rate of 60%, and a median progression-free survival of 17.9 months in patients with relapsed/refractory (r/r) follicular lymphoma (FL) following at least two prior lines of systemic therapy, including alkylator and anti-CD20 antibody-based therapy. Historical data from cohorts receiving therapy for r/r FL can provide some context for interpretation of single-arm trials. We compared the results from the mosunetuzumab trial to outcomes from a cohort of patients with r/r FL from the LEO Consortium for Real World Evidence (LEO CReWE). We applied clinical trial eligibility criteria to the LEO CReWE cohort and utilized matching-adjusted indirect comparison weighting to balance the clinical characteristics of the LEO CReWE cohort with those from the mosunetuzumab trial. Overall response rates (73%, 95% CI:65-80%) and complete response rates (53%, 95% CI:45-61%) observed in the weighted LEO CReWE cohort were lower than those reported on the mosunetuzumab trial (ORR=80%, 95% CI:70-88%; CR=60%, 95% CI:49-70% respectively). Progression-free survival at 12 months was similar in the weighted LEO CReWE (60%, 95% CI:51-69%) and the mosunetuzumab trial (PFS 58%, 95% CI:47-68%). Sensitivity analyses examining the impact of matching variables, selection of line of therapy, and application of eligibility criteria, provide context for best practices in this setting.