Real-World Observations and Practical Considerations of Subcutaneous Daratumumab Administration in Multiple Myeloma

Background: Subcutaneous daratumumab (dara-SC) has several advantages over intravenous daratumumab (dara-IV). It has significantly shorter administration time, lower rates of systemic reactions, and smaller administration volume, while maintaining comparable efficacy and safety. Its fixed dosing allows for easier preparation. At our institution, standard approach is to monitor for 4h following the initial dara-SC dose for those at high risk for systemic reactions, defined as no prior dara use, treatment break ≥90d, or any prior history of reactions. We also administer montelukast and fexofenadine for the first 2 doses of dara-SC in addition to the usual standard pre-medications. Herein, we share our experience with dara-SC use in both dara-naïve and dara-exposed patients in order to gain practical insight, such as optimal monitoring duration, considerations for transitioning between dara-IV and dara-SC, and the place of therapy for dara-IV based on adverse events (AEs).

Methods: Between June 2020 and June 2021, patients who received at least one dose of dara-SC were identified and their record was reviewed for any systemic reactions, hypersensitivity medication use, and patient reported AEs.

Results: Since June 2020, our dara-SC drug use increased from 38% to 91% of all doses. There were 208 patients who received at least 1 dose of dara-SC. Of 208 patients, 99 (47.6%) were dara-naïve and 109 (52.4%) had prior dara exposure - either transitioning from dara-IV on schedule or had dara-IV as a past line of therapy. We identified 124 patients who met the criteria for 4h post dara-SC injection monitoring: dara-naïve (79.8%), treatment break ≥90d (18.5%), or prior history of reactions (1.6%). Only 5 experienced systemic reactions, representing 4% among those at high risk. All reactions were mild requiring minimal intervention and occurred following the first dara-SC dose. Onset of reactions and type of intervention during the 4h monitoring window were: hypotension (2h; fluid), nausea/vomiting (2.5h; hypersensitivity medications), and sinus tachycardia (4h), while 2 patients had transient chest pressure/tightness at home (1 within 24h, 1 between 1-6d following the dose). Eleven patients (5%) receiving dara-SC converted back to dara-IV, with AEs being the most common reason. Diarrhea, fatigue, and injection site reactions were among the most frequent patient-reported AEs. When transitioning back to dara-IV, a 90min rapid infusion rate was used if >4 prior dara doses were given. No infusion-related reactions were observed.

Conclusion: The introduction of dara-SC has significantly improved patient experience. We observed a lower rate of systemic reactions compared to previous reports of 10% with first dose of dara-SC. This may be partly due to our strengthened pre-medication strategy. Opportunities exist to further improve and apply practical considerations when administering dara-SC. Based on our results, shortening on-site monitoring time may be feasible.