Efgartigimod Efficacy in Idiopathic Inflammatory Myopathy Save
Today Argenx announced the results of their Phase 3 "ALKIVIA" study; demonstrating efficacy and safety of subcutaneous efgartigimod for Idiopathic Inflammatory Myopathy (IIM, AKA inflammatory myositis).
Efgartigimod (EFG) is a human IgG1 antibody fragment that binds to the neonatal Fc receptor (FcRn), resulting in downregulation of circulating IgG autoantibodies. This drug was previously effective and approved for use in generalized myasthenia gravis (gMG), chronic inflammatory demyelinating polyneuropathy (CIDP) and in Japan for immune thrombocytopenia. The drug has the trade name of VYVGART Hytrulo and is a subcutaneous combination of efgartigimod-alfa and recombinant human hyaluronidase.
The ALKIVIA study was a global, randomized, double-blind, placebo-controlled, multicenter, Phase 2/3 study of EFG SC vs. placebo (1:1) and enrolled 264 active patients with dermatomyositis (DM), polymyositis (PM) and immune-mediated necrotizing myositis (IMNM). The phase 2 study enrolled the first 89 patients; and was followed by Phase 3 study that enrolled 175 patients. The 52 week primary endpoint of Phase 3 was the mean Total Improvement Score (TIS).
Top line, week 52 results showed showed significant improvement in the mean Total Improvement Score (TIS) at Week 52 for the combined IMNM and DM patients (p=0.0011) - the TIS differential favored EFG by 15.4 points at Week 52 versus placebo (47.95 vs 32.56). In the combined population, patients treated with EFG consistently showed improvements over placebo starting at Week 4 that were sustained through the full year of treatment, even with steroid tapering.
In prespecified subtype analyses, meaningful TIS improvement was seen in IMNM patients vs. placebo (TIS difference of 14.8 points; 45.05 vs 30.24; p=0.0048). A similar TIS difference was seen for EFG vs. placebo responses in DM patients (TIS difference 14.5 points, 51.51 vs 36.96; p=0.1093) but was not statistically significant.
The efficacy results of EFG in the PM subset of patients was not released.
While it was mentioned that improvement in both muscle and skin measures were seen (especially in the DM subset), it should be noted that the Total Improvement Score (TIS) does not include a specific measure for skin outcomes. It is heavily weighted toward muscle function and overall disease activity (global assessment, muscle enzymes, etc.).
Efgartigimod was well-tolerated by patients in the ALKIVIA study. The observed safety profile was consistent with prior studies and the known safety profile of efgartigimod (similar to most current biologics - injection reactions, infections, etc).
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