Matching-Adjusted Indirect Comparison (MAIC) of Efficacy and Safety of Lisocabtagene Maraleucel (liso-cel) and Mosunetuzumab for the Treatment (Tx) of Third Line or Later (3L+) Relapsed or Refractory (R/R) Follicular Lymphoma (FL)

Background:The tx landscape of R/R FL is evolving with the availability of anti-CD19 chimeric antigen receptor (CAR) T cell therapies and CD20xCD3 bispecific T-cell-engaging monoclonal antibodies (mAb). Liso-cel is an autologous, CD19-directed, 4-1BB CAR T cell therapy which recently reported a positive benefit-risk tx profile for the 3L+ tx of patients with R/R FL (Morschhauser F, et al. ICML 2023; LBA4). Mosunetuzumab, a CD20xCD3 bispecific T-cell-engaging mAb, is approved for the tx of R/R FL after 2 or more lines of therapy (LOT). In the absence of head-to-head data, we conducted an unanchored MAIC to compare the efficacy and safety of liso-cel and mosunetuzumab for the 3L+ tx of patients with R/R FL. Methods: Unanchored MAICs were used to estimate population-adjusted relative tx effects between individual patient-level data from TRANSCEND FL (NCT04245839; data as of January 27, 2023; median follow-up of 19.3 months) and aggregate data from GO29781 (NCT02500407; data as of August 27, 2021; median follow-up of 18.3 months; N = 90). For TRANSCEND FL, the leukapheresed (intention to treat [ITT]) set (N = 114) was used for primary comparisons of efficacy endpoints: Progression-free survival (PFS), objective response rate, and complete response rate (all per independent review committee assessment). Overall survival was not analyzed due to the low rate of events. The treated efficacy set (n = 101) was used for a sensitivity analysis of efficacy comparisons. The treated set (n = 107) was used for comparisons of safety endpoints: cytokine release syndrome (CRS), neurological events (NEs), serious infections, and use of corticosteroids or tocilizumab for CRS. Baseline characteristics and outcome measures in TRANSCEND FL were redefined to align with those reported in GO29781. Data from TRANSCEND FL were weighted using a method-of-moments propensity score model to match the marginal distribution (ie, mean, variance) of clinical factors among patients from GO29781. A panel of expert clinicians selected and ranked tx effect modifiers separately for efficacy and safety endpoints. For efficacy, factors adjusted for included number of prior systemic LOTs, progression of disease ≤ 24 months from initiation of immunochemotherapy, bulky disease at screening, FL International Prognostic Index risk factor, refractory to last therapy, double refractory to an anti-CD20 antibody and alkylating agent, ECOG PS at screening, sex, and prior autologous HSCT. For safety, factors a