Unveiling the Promising Long-Term Potential of Subcutaneous Efgartigimod PH20 in Managing gMG

• Efgartigimod PH20 is a combination subcutaneous (SC) infusion that contains efgartigimod alfa and hyaluronidase which may be used to improve muscle weakness in adults with generalized myasthenia gravis (gMG) who are anti-AChR antibody positive.
• The interim results presented by Argenx highlighted notable efficacy and tolerability of SC efgartigimod PH20. With manageable adverse events and consistent clinical improvements, it underscores the treatment’s promising potential for gMG.

In the realm of treating gMG, the quest for safer and more effective therapeutic options is a perpetual endeavor. Amidst this pursuit, the interim results of the ADAPT-SC+ study shed light on the long-term safety, tolerability, and efficacy of SC efgartigimod PH20.

The ADAPT-SC+ study (NCT04818671), building upon the findings of its predecessor, ADAPT-SC, and the ADAPT+ open-label extension (OLE) study, delved into the realm of SC administration of efgartigimod PH20. Participants received efgartigimod PH20 SC in cycles of four once-weekly injections, with subsequent cycles initiated at least 28 days apart based on clinical evaluation. The Myasthenia Gravis Activities of Daily Living (MG-ADL) score served as the benchmark for assessing clinical efficacy. The study identified predominantly mild to moderate adverse events (AEs), with the most frequent being injection site erythema (29.1%), COVID-19 (22.3%), and headache (20.1%). Notably, injection site reactions remained manageable, did not necessitate treatment cessation, and showed a decline in occurrence with successive cycles, dropping from 34.6% (n=62/179) in Cycle 1 to 11.5% (n=14/122) in Cycle 6. Analysis revealed significant enhancements from baseline throughout the treatment course, exemplified by notable improvements in the MG-ADL total score (−4.1 [0.27%]), Myasthenia Gravis Quality of Life 15-Item Questionnaire, Revised (MG-QoL15r) (−5.1 [0.44%]), and EuroQoL 5-Dimension, 5-Level (EQ-5D-5L) (13.8 [1.54%]) as early as Cycle 1. These improvements persisted consistently and reproducibly up to Cycle 9. Remarkably, the observed enhancements paralleled those documented with efgartigimod IV during the ADAPT/ADAPT+ trials, suggesting robust and comparable therapeutic efficacy.

Conclusion: The interim analysis of the ADAPT-SC+ trial illuminates the considerable promise of subcutaneous efgartigimod PH20 as a well-tolerated and effective therapeutic avenue for gMG. With its favorable long-term safety profile and notable clinical advancements echoing those observed with efgartigimod IV, subcutaneous efgartigimod PH20 emerges as a beacon of optimism in the realm of gMG treatment. It offers patients a pathway to enhanced quality of life and symptom management. As research unfolds, the journey towards expanding the therapeutic arsenal for gMG enters a new phase, heralding brighter prospects for patients and caregivers alike.