Preventive Effects of Non-sedating and Sedating Histamine H<sub>1</sub> Receptor Antagonists Premedication for Subcutaneous Daratumumab-Associated Infusion-Related Reactions: A Prospective Observational Study

The optimal choice between sedating histamine H1 antagonists (sAHs) and non-sedating histamine H1 antagonists (nsAHs) for preventing infusion-related reactions (IRRs) during daratumumab subcutaneous (DARA-SC) therapy remains unclear. Here, we aimed to compare the efficacy and safety of nsAH and sAH as premedication for DARA-SC therapy. Patients with multiple myeloma or light-chain amyloidosis who received DARA-SC therapy at eight hospitals were enrolled in this prospective, multicenter, observational study. Patients were categorized into nsAH and sAH groups based on their premedication. IRRs and drowsiness were assessed using patient-reported questionnaires, including the Stanford Sleepiness Scale (SSS) and the Japanese Epworth Sleepiness Scale (JESS), at baseline, post-administration (Q2), and before bedtime (Q3). Overall, 104 patients (nsAH, n = 49; sAH, n = 55) were analyzed. No significant differences were observed in the IRR incidence between the nsAH and sAH groups at Q2 (8.2 vs. 9.1%) or Q3 (13 vs. 17%). Conversely, the incidence of new-onset drowsiness at Q2 was significantly lower in the nsAH group (13%) than in the sAH group (32%, p < 0.05). Additionally, the increase in SSS from baseline to Q2 was significantly lower in the nsAH group than in the sAH group (p < 0.05). No significant differences were observed in JESS scores. Thus, nsAH was associated with reduced early post-administration drowsiness and there were no statistically significant differences in IRR preventive effects compared to that for sAH, suggesting that nsAH may reduce sedation without a significant increase in the incidence of IRRs; however, these hypothesis-generating findings warrant verification through future prospective comparative trials.