Efgartigimod/Hyaluronidase

Shares of Dianthus Therapeutics surged 22% Monday after the biotech reported positive results from its Phase II MaGic trial testing claseprubart (DNTH103) in generalised myasthenia gravis (gMG). The company now plans to move the antibody into Phase III studies in 2026, evaluating 300 mg doses given every two and four weeks.Claseprubart is designed to block only the active form of C1s, a protein that drives the classical complement pathway implicated in gMG, while sparing other immune functions to reduce infection risk. Administered subcutaneously, the drug incorporates half-life extension technology intended to support less frequent dosing and self-administration.The MaGic trial enrolled 65 patients with acetylcholine receptor antibody-positive (AChR+) gMG. After an initial loading dose, they received subcutaneous injections of claseprubart via autoinjector every two weeks at either 300 mg/2 mL or 600 mg/4 mL.At week 13, the 300-mg dose arm improved by 4.6 points on the Myasthenia Gravis - Activities of Daily Living (MG-ADL) scale versus baseline, with a placebo-adjusted benefit of 1.8 points. The higher 600-mg dose showed a 5.4-point absolute gain and 2.6-point advantage over placebo. Improvements were also observed on the Quantitative Myasthenia Gravis (QMG) assessment, where patients showed improvements of 4.4 and 4.5 points, on the low and high doses, respectively, compared with a 2-point gain in the placebo group.Dianthus said that benefits appeared quickly; on both the MG-ADL and QMG measures, claseprubart achieved significant improvements starting in the first week.Rethinking complement thresholdsCEO Marino Garcia contrasted Monday's results with Regeneron Pharmaceuticals' "eye-opening" late-stage readout last month for its C5-targeting siRNA cemdisiran. "The fact that they had a significant improvement on the MG-ADL… and they disclosed that they only achieved 75% inhibition of the complement system – that's, in a way, a groundbreaking bit of information that tells us that getting above IC90 was always really an artificial goal," Garcia during a call with analysts."So, if achieving something like 75% or 80% inhibition of the classical pathway is enough to give you similar results, we're very confident that's what [every-four-week dosing] would be doing. And remember, we have a 60-day half-life, so for every four weeks… is very much well within our half-life timeline," he added.As for safety, claseprubart was well tolerated in the study, with no treatment-related serious infections, signs of autoimmune disease, or drug-related adverse events leading to discontinuation, findings that support its potential to avoid a boxed warning or REMS requirement for meningococcal infections.Beating rivals, but…Wedbush analyst Laura Chico suggested that on all measures of the study, claseprubart appeared to outperform Ultomiris (ravulizumab), AstraZeneca's C5 complement inhibitor for gMG.However, Wedbush's David Nierengarten says that despite the positive MaGic readout, argenx's FcRn blocker Vyvgart (efgartigimod alfa), also available subcutaneously as Vyvgart Hytrulo, is expected to remain a dominant treatment. "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.Meanwhile, Garcia described 2026 as a "catalyst-rich year" for Dianthus, with the planned Phase III gMG trial, followed by a second-half interim responder analysis of claseprubart from the Phase III CAPTIVATE study in chronic inflammatory demyelinating polyneuropathy, and top-line results from the Phase II MoMeNtum trial testing the drug in multifocal motor neuropathy.

iStock, Deagreez Based on new data, argenx expects to the expansion of Vyvgart’s label into patients with generalized myasthenia gravis who are negative for antibodies against the AChR marker—an indication William Blair analysts called the broadest option in this disease space. Argenx’s Vyvgart significantly improved disease activity and daily life in certain patients with generalized myasthenia gravis in a Phase III study, setting the FcRn inhibitor up for a potential label expansion. Writing to investors on Monday, William Blair analysts said that with these new data, Vyvgart “represents the first FcRN inhibitor to demonstrate statistically significant clinical efficacy in AChR seronegative gMG [generalized myasthenia gravis] patients”—the specific population that the Phase III ADAPT SERON trial focused on. If cleared for this specific indication, Vyvgart would have “the broadest label of all FcRn antagonists approved in gMG,” they added. Argenx did not reveal specific data in its news release on Monday , noting only that Vyvgart elicited a “statistically significant and clinically meaningful improvement” in disease activity in patients with gMG who are seronegative for antibodies against the AChR marker. According to the biotech, this particular subpopulation represents about 20% of all gMG patients, a group that often experiences a heavier disease burden. With these findings, argenx is gearing up for a supplemental application to expand Vyvgart into patients negative for antibodies against AChR, covering all three subtypes: MuSK-positive, LRP4-positive and triple seronegative patients, as per its Monday release. The company expects to make its submission by the end of the year. If approved, Vyvgart would gain access to roughly 11,000 additional gMG patients beyond its current market, according to William Blair. Breaking into this patient population would also give Vyvgart an edge over its current competitors, including Johnson & Johnson’s Imaavy and UCB’s Rystiggo, both of which “are approved only in gMG patients with AChR-positive or MuSK-positive” disease, according to the analysts. Infused intravenously, Vyvgart is a human IgG1 antibody fragment that treats gMG by lowering the circulating levels of IgG. The therapy was first approved in 2021 but is currently only indicated for patients who are positive for antibodies against AChR. In June 2023, argenx secured an approval for a subcutaneous formulation of Vyvgart, called Vyvgart Hytrulo, for gMG. The under-the-skin injection has also been approved for chronic inflammatory demyelinating polyneuropathy . Last year, argenx reached more than 10,000 patients and brought in nearly $2.2 billion in sales from its Vygart line alone.