Argenx Just Landed Another Phase 3 Win -- and Wall Street May Be Missing the Bigger Story

Argenx (NASDAQ: ARGX) already markets Vyvgart Hytrulo for treating generalized myasthenia gravis (gMG) and chronic inflammatory demyelinating polyneuropathy (CIDP), two rare chronic autoimmune diseases. It appears to be on track to add another approved indication for the drug.

On Aug. 17, 2026, Argenx announced positive results from a Phase 3 clinical study evaluating Vyvgart Hytrulo for adults with autoimmune myositis. Like gMG and CIDP, autoimmune myositis is a rare autoimmune disease. Around 100,000 people in the U.S. are affected by it. No targeted treatments are currently available.

Wall Street celebrated the news, with the biotech stock jumping more than 20% in the days following Argenx's announcement. But there's a bigger story for the company than one late-stage win.

Image source: Getty Images.

Drilling into Argenx's late-stage results

There were two patient populations in Argenx's Alkivia Phase 3 study of Vyvgart Hytrulo. Some patients had immune-mediated necrotizing myopathy (IMNM), while others had dermatomyositis (DM). Both IMNM and DM are types of autoimmune myositis. Around 20,000 people in the U.S. are diagnosed with IMNM, compared to roughly 40,000 patients in the U.S. who are diagnosed with DM.

The overall results from the late-stage study were highly encouraging. In the combined population, patients treated with Vyvgart Hytrulo achieved a 15.4-point improvement in mean Total Improvement Score at week 52 compared to placebo, easily meeting the clinical trial's primary endpoint. Furthermore, patients began showing consistent and statistically significant improvements versus placebo at week four, with these improvements sustained through the full year of treatment.

Argenx's results for IMNM patients were an unqualified success. IMNM patients receiving Vyvgart Hytrulo experienced a 14.8 point improvement over placebo at 52 weeks, meeting the primary endpoint. This improvement especially excited investors because Alkivia is the first Phase 3 study to demonstrate statistically significant reductions in disease activity for patients with IMNM -- a subtype of autoimmune myositis without an approved therapy.

There was one fly in the ointment with the Alkivia study, though. The primary endpoint wasn't achieved for the patient population with DM. However, Argenx said that "clinically meaningful improvement" over placebo was observed. Also, there were fewer patients with DM in the study than with IMNM. This miss seems more related to sample size than to efficacy.

The bigger story

It's easy to merely view Argenx as a one-trick pony. The company officially has two approved therapies (Vyvgart and Vyvgart Hytrulo), but they both use the same antibody under the hood -- efgartigimod alfa.

While efgartigimod alfa may be only one pony, though, it could be able to perform many tricks. The drug's mechanism of action targets the FcRn receptor to reduce the levels of pathogenic IgC antibodies. This approach could -- and, arguably, should -- be applicable for dozens of autoimmune diseases.

Alkivia is just the latest of Argenx's Phase 3 successes. The company has reported positive late-stage results for efgartigimod in treating gMG, primary immune thrombocytopenia, and ocular myasthenia gravis as well. Argenx's pipeline includes other clinical trials targeting Graves' disease, Sjogren's disease, system sclerosis, and antibody-mediated rejection.

There are also other "horses" in Argenx's stable. It's evaluating empasiprubart in two late-stage studies and adimanebart in earlier-stage studies. In addition, Argenx is acquiring Forte Biosciences. This deal will enable Argenx to add FB102, Forte's promising "pipeline-in-a-product," to its lineup.

Is Argenx stock a buy?

Of the 22 analysts surveyed by S&P Global (NYSE: SPGI) in July who cover Argenx, 19 recommended the stock as a "buy" or "strong buy." However, the average 12-month price target for Argenx reflects an upside potential of less than 10%.

Why do analysts like the stock but have only modest expectations for it? Price has a lot to do with it. Argenx isn't a value stock by any means, with shares trading at roughly 36 times forward earnings.

However, part of the issue could also be that some on Wall Street view Argenx as a one-drug story rather than as a company with a platform. That could prove to be a mistake.

Keith Speights has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Argenx Se and S&P Global. The Motley Fool has a disclosure policy.