To investigate bioequivalence, safety, and tolerability of efgartigimod administered subcutaneously (SC, coformulated with recombinant human hyaluronidase) via prefilled syringe (PFS) vs a vial administered via a separate syringe (V+S) in healthy participants.

Efgartigimod is a human immunoglobulin G1 (IgG1) antibody Fc-fragment that reduces IgG levels, including pathogenic IgG autoantibodies, through neonatal Fc receptor blockade. Efgartigimod PH20 SC was well tolerated and efficacious in phase 3 trials in participants with generalized myasthenia gravis (gMG) and chronic inflammatory demyelinating polyneuropathy (CIDP). The 1000-mg fixed-dose formulation of efgartigimod PH20 SC is provided in a V+S. To increase patient convenience, a PFS has been developed to ease the injection procedure.

Bioequivalence of efgartigimod PH20 SC administered via PFS vs V+S was assessed in a phase 1, open-label, randomized, 2-period cross-over study. Healthy participants (n=72) were randomized to receive a single injection of efgartigimod PH20 SC via PFS or V+S, and then switched to receive the alternate administration. Bioequivalence was determined based on predefined criteria. Separate studies were conducted to determine the feasibility of different injection speeds and the usability of efgartigimod.

Pharmacokinetic bioequivalence between efgartigimod PH20 SC administered via PFS or via V+S was established, as the 90% CI around the GMR of C_max and AUC_0-inf was within the predefined criteria of 80.00% to 125.00%. The majority of adverse events were mild to moderate, and there were no observed differences in incidence of reported injection site reactions. No serious adverse events and no deaths were seen in the study. Rapid (20-second) administration was feasible, and human factor validation studies determined that the PFS could be safely prepared and administered by participants/caregivers. 

This study demonstrated that efgartigimod PH20 SC administered via PFS is bioequivalent to efgartigimod PH20 SC administered via V+S, which may provide an additional convenient treatment option for patients with gMG and CIDP.