argenx posts positive ALKIVIA Phase 3 data

argenx announced positive topline data from ALKIVIA, a global seamless Phase 2/3 study evaluating subcutaneous efgartigimod (VYVGART Hytrulo) in adults with autoimmune myositis. The Phase 3 portion of the trial met its primary endpoint in the combined population of immune‑mediated necrotizing myopathy (IMNM) and dermatomyositis (DM) patients.

At Week 52, patients treated with efgartigimod achieved a 15.4‑point greater mean Total Improvement Score (TIS) compared with placebo, with scores of 47.95 versus 32.56, respectively. The difference was statistically significant with a p‑value of 0.0011, indicating a robust overall clinical effect in this pooled myositis group.

Prespecified subtype analyses showed that the IMNM cohort met the primary endpoint. IMNM patients treated with efgartigimod had a 14.8‑point greater mean TIS improvement at Week 52 compared with placebo, with scores of 45.05 versus 30.24 and a p‑value of 0.0048, demonstrating statistical significance.

In the DM subgroup, efgartigimod‑treated patients recorded a 14.5‑point higher mean TIS at Week 52 versus placebo, with scores of 51.51 versus 36.96. While the magnitude of improvement was comparable to IMNM, the result did not reach statistical significance in this smaller cohort, with a p‑value of 0.1093.

ALKIVIA enrolled 264 patients across its seamless Phase 2/3 design. The Phase 3 portion included 175 patients randomized 1:1 to receive weekly subcutaneous injections of efgartigimod PH20 SC (VYVGART Hytrulo, comprising efgartigimod alfa plus hyaluronidase PH20) or matched placebo, alongside a protocol‑mandated corticosteroid taper.

argenx reported that improvements with efgartigimod emerged early and were sustained through one year despite corticosteroid reduction. All six core set measures that contribute to the TIS favored efgartigimod, with clinical effects observed on muscle outcomes and, in DM patients, on skin measures.

Efgartigimod was described as well tolerated in ALKIVIA, with a safety profile consistent with prior VYVGART studies. No new safety signals were highlighted in the topline readout, supporting the overall tolerability of subcutaneous efgartigimod in this patient population.

argenx plans to present detailed ALKIVIA results at an upcoming medical meeting to provide a fuller view of efficacy and safety data. The company also scheduled an investor conference call and webcast for August 17 at 2:30 PM CET / 8:30 AM ET to discuss the topline findings with analysts and investors.

Market reaction to the announcement was positive. Multiple reports indicated that argenx shares rose following the news, with one account citing an early trading gain of roughly 7.9% and another noting the stock trading up nearly 9% overnight, reflecting investor optimism about efgartigimod’s performance in autoimmune myositis.