Shares of Dianthus Therapeutics surged to an 18-month high Monday after the company's autoimmune disease treatment succeeded in a midstage study.
Now, Dianthus is planning to send its drug, claseprubart, into Phase 3 testing. The company is testing claseprubart in patients with generalized myasthenia gravis, an autoimmune condition that affects the connection between the nerves and muscles.
In Dianthus' study, dubbed MaGic, patients received under-the-skin injections of claseprubart every two weeks. After 13 weeks, claseprubart recipients given a lower 300-milligram dose showed a 1.8-point improvement, compared with the placebo group, on a 24-point scale measuring symptoms of generalized myasthenia gravis. The 600-milligram dose led to a 2.6-point improvement vs. the placebo.
Wedbush analyst Laura Chico called it a "MaGic moment" for Dianthus Therapeutics.
"Preliminary Phase 2 data validates claseprubart can effectively reduce MG symptoms in a rapid time frame, which is a good thing," she said in a note. "Heading into the readout, this is exactly what we hoped to learn. Longer-term data from the open-label extension portion of the study will offer further insight into the durability of response."
On the stock market today, Dianthus stock jumped 20% to 31.80. Shares had run up almost 47% from a recent low at 18.08 on Aug. 11 to Friday's close.
Rivaling Argenx, AstraZeneca
The news carries implications for Argenx and AstraZeneca.
Argenx sells Vyvgart and Vyvgart Hytrulo, two versions of the same drug that can treat generalized myasthenia gravis. AstraZeneca, which bought Alexion Pharmaceuticals, sells Ultomiris. While Vyvgart uses a different mechanism, Ultomiris blocks the complement 5 protein. Claseprubart blocks the complement 1 protein.
On all measures of the study, claseprubart outperformed Ultomiris, Wedbush's Chico said.
Anti-nuclear antibodies remain a concern for investors, however. None of the placebo recipients developed anti-nuclear antibodies, or ANA. These mistakenly attack the body's own tissues. But 6% of the 300-milligram dose recipients and 36% in the 600-milligram group developed ANAs.
As such, Dianthus is sending the lower dose into final-phase testing. Oppenheimer analyst Trevor Allred notes that just a 75% reduction in the problematic protein is necessary to improve symptoms.
Another Wedbush analyst, David Nierengarten, says the results are promising but unlikely to unseat Vyvgart.
"We continue to see several years of unobstructed growth ahead for Vyvgart in MG and given its strong clinical profile and ease of administration with the availability of a prefilled syringe, we believe that use of other approved agents will largely be relegated to patients who do not respond well to Vyvgart," he said in a client note.
Pipeline-In-A-Product
Still, the results bode well for Dianthus Therapeutics' efforts to expand claseprubart to other diseases. The company is testing its drug in patients with chronic inflammatory demyelinating polyneuropathy, or CIDP, and multifocal motor neuropathy, or MMN. Both are autoimmune conditions that affect the muscles.
Oppenheimer's Allred notes Sanofi is also working on a complement 1 protein blocker called riliprubart.
"We still hold some concern over potential riliprubart label advantages despite claseprubart's likely superior profile, but believe claseprubart is well-positioned for superiority in MMN," he said.
William Blair analyst Myles Minter says Dianthus is trying to develop claseprubart as a pipeline-in-a-product, similar to Argenx's Vyvgart.
"We believe the MaGic data continues to robustly support claseprubart's potential as the best-in-class asset across the complement inhibitor landscape," he said in a client report. "With readouts in CIDP and MMN expected in the second half of 2026, for which we now have increased confidence on the claseprubart doses being evaluated, we continue to see a catalyst-rich period ahead for Dianthus."
Follow Allison Gatlin on X/Twitter at @AGatlin_IBD.
