Retrospective study of infusion-related reactions in subcutaneous daratumumab administration in Japan.

The subcutaneous formulation of daratumumab (DARA-SC), an improved version of the intravenous formulation, has reduced administration time compared to the latter. However, real-world data regarding its infusion-related reactions (IRRs) remain limited. The present study evaluated the incidence rate, timing and risk factors for IRRs associated with the first dose of DARA-SC. This retrospective analysis included 65 patients who received their first DARA-SC dose at Gifu Municipal Hospital, Japan between May 2021 and June 2024. IRRs occurred in 10 patients (15.4%), and all cases were mild, categorized as grade 1 or 2. The median time to IRR onset was 10 h (range, 0.5-46 h), and delayed-onset IRRs (occurring after 24 h) accounted for 30% of cases. Univariate analysis identified a history of allergies as a potential factor associated with IRR occurrence (P=0.04). Older patients (≥70 years) tended to experience delayed-onset IRRs. Although these findings should be interpreted cautiously because of the limited cohort size, careful monitoring during initial DARA-SC administration might be important, particularly in patients with a history of allergies and in older patients, considering the possibility of delayed-onset IRRs.