(292) Real-World patterns of intravenous immunoglobulin (IVIG) and antimicrobial use in members with multiple myeloma treated with chimeric antigen receptor T-cell (CAR T) or bispecific antibody (BsAbs) therapies

Background: : Multiple myeloma (MM), a plasma cell disease accounting for ~1-2% of cancers, primarily affects older adults. Although 5-year survival exceeds 60%, MM remains incurable. CAR T and BsAbs improve outcomes but B-cell depletion and hypogammaglobulinemia increase infection risk. Guideline bodies recommend IVIG in CAR T or BsAb recipients, yet real-world use and benefit remain unclear.

Objective: : To characterize IVIG use and infection rates post BsAbs and CAR T administration.

Methods: : This retrospective cohort study used commercial and Medicare claims (Mar 2021 to Nov 2024). Members with MM received idecabtagene vicleucel, ciltacabtagene autoleucel, autologous CAR T, teclistamab, elranatamab, or talquetamab. The index date was the first therapy claim. Members required at least 6 months of continuous enrollment pre- and post-index. IVIG use was assessed by timing (pre-index, post-index, or both), frequency (days between claims), and site of care. Systemic antimicrobials, excluding prophylactic agents, were a proxy for infection. Annualized IVIG drug average allowed amounts (AIDAAA) were calculated by line of business.

Results: : Among 271 members, 65.3% received IVIG. Use was more frequent with BsAbs (70.1%) than CAR T (60.6%). Post-index use occurred in 40.1% of CAR T and 38.8% of BsAb members. Use in both periods was observed in 19.0% of CAR T and 31.3% of BsAb members. In a subgroup of 101 members with at least two IVIG claims (post-index or both), the time between IVIG doses decreased from 49.9 to 38.2 days post-index among CAR T recipients. BsAb users showed consistent time between IVIG doses at 35.4 days pre-index and 35.2 days post-index. IVIG was administered in hospital outpatient (66.5%), physician office (28%), home infusion (2.5%), or inpatient (2.5%). AIDAAA per member was higher for BsAb than CAR T in both commercial ($44,971 vs $25,871) and Medicare plans ($16,782 vs $15,064). Systemic antimicrobials were used in 91.1% of members. Among those who never received IVIG, 92.6% had at least one antimicrobial claim, while 2.6% had no antimicrobial claims.

Conclusions: : IVIG and antimicrobial use varied by therapy. For BsAb-treated members IVIG use frequency did not change, while CAR T members had shorter intervals post-treatment. Antimicrobial use in no-IVIG resembled IVIG post-index members. Most IVIG infusions occurred in hospital outpatient settings highlighting the need for lower-cost, home-based care. Prospective studies are needed to elucidate IVIG benefit in infection treatment and prevention.

Sponsorship:: External funding is not required