Argenx’s stock opened 8.9% up after a Phase III trial of Vyvgart Hytrulo (efgartigimod alfa and hyaluronidase-qvfc) in adults with autoimmune myositis met its primary endpoint.
In the Phase III ALKIVIA trial (NCT05523167), patients from the combined immune-mediated necrotising myopathy (IMNM) and dermatomyositis (DM) population treated with Vyvgart Hytrulo demonstrated a statistically significant 15.4-point greater improvement in mean Total Improvement Score (TIS) compared to placebo after 52 weeks. Statistically significant improvements were seen as early as four weeks and were sustained through the full year of treatment, even with steroid tapering.
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In both IMNM and DM, all six core set measures of TIS contributed to the treatment effect, each favouring efgartigimod over placebo, spanning muscle strength, everyday physical function, and disease activity beyond the muscle. In DM, improvement in skin disease activity was also observed.
In the separate subtype analyses, the primary endpoint was met in IMNM, and while clinically meaningful benefit was seen in the DM cohort, statistical significance was not reached.
The observed safety profile of Vyvgart Hytrulo was consistent with previous studies. Detailed results from the ALKIVIA study will be presented at an upcoming medical meeting.
Autoimmune myositis is a group of rare conditions where the immune system attacks healthy muscle fibres.
Dr Rohit Aggarwal, professor of medicine and co-director of the Myositis Center at the University of Pittsburgh, and an ALKIVIA investigator, said: “IMNM is the most refractory form of this disease and many of these patients carry irreversible muscle damage, which makes meaningful improvement genuinely difficult to achieve. That is what makes these results so compelling and groundbreaking. In DM, the magnitude of improvement was comparable – and for a community where treatment options remain limited, and the burden of chronic steroids is just as heavy, that matters. Together, these results tell us that reducing pathogenic autoantibodies is clinically meaningful and a major step forward for patients who are in need of a targeted treatment.”
As the markets opened on 17 August, argenx’s stock rose 8.9%, from a 14 August close of $851.29 to a 17 August open of $927.33. The company, listed on the Nasdaq exchange, has a market cap of $61.25bn.
The drug is also being investigated in other autoimmune rheumatologic diseases, including Sjögren’s disease and systemic sclerosis.
It first gained approval from the US Food and Drug Administration (FDA) in generalised myasthenia gravis (gMG) in June 2023 and has since been given the green light for use in patients with chronic inflammatory demyelinating polyneuropathy (CIDP).
The drug is developed as part of a partnership between argenx and Zai Lab Limited. Zai Lab has the rights to both intravenous and subcutaneous Vyvgart in China and nearby markets under the terms of the 2021 deal.
