OBJECTIVES: Mosunetuzumab (Mosun), a CD20xCD3 T-cell engaging bispecific antibody, has received US Food and Drug Administration accelerated approval. We conducted a budget impact analysis to assess the impact of introducing Mosun as a 3L+ R/R FL treatment option and to estimate the total cumulative costs per patient in the US.

METHODS: A 3-year budget impact model was developed for a hypothetical 1-million-member cohort enrolled in a mixed commercial/Medicare health plan. Comparators were: axicabtagene ciloleucel (axi-cel), tisagenlecleucel (tisa-cel), tazemetostat (taz), rituximab + lenalidomide (R-Len), copanlisib (copan), and older therapies (rituximab or obinutuzumab ± chemotherapy). Costs per patient comprised treatment-associated costs including the drug, its administration, adverse events, and routine care. Drug costs were estimated based on the average wholesale acquisition cost reported in AnalySource®. All other costs were based on published sources. Market shares were obtained from Genentech internal projections and expert opinion. All costs were inflated to 2022 US dollars. Budget impact outcomes were presented on a per-member per-month (PMPM) basis.

RESULTS: Compared with a scenario without Mosun, its introduction over 3 years resulted in a budget increase of $106,685 and an average PMPM net budget impact of $0.003. Mosun had the second-lowest cumulative per patient cost (Mosun = $202,039; axi-cel = $506,255; tisa-cel = $448,507; R-Len = $263,520; taz = $236,209; copan=$127,293) and drug costs among the newer therapies, and its introduction only increased total drug costs by 0.7%. By Year 3, the cumulative difference in per patient cost with Mosun was -$304,216 vs. axi-cel, -$246,468 vs. tisa-cel, -$61,481 vs. R-Len, -$34,170 vs. taz, and $74,746 vs. copan.

CONCLUSIONS: Over 3 years, the estimated cumulative per patient cost of Mosun is lower than most available newer therapies, resulting in a small increase in budget after its formulary adoption for the treatment of 3L+ R/R FL.