Statnews
Belgian drugmaker Argenx said Tuesday that its antibody medicine failed to achieve the goals of a late-stage study for a platelet-destroying autoimmune disorder — a setback in the company’s efforts to expand the drug’s use.
Argenx shares were down 12% in early trading.
The negative study, called ADVANCE-SC, was the second of two clinical trials involving the Argenx drug, called efgartigimod, in patients with primary immune thrombocytopenia (ITP), a debilitating condition that destroys blood-clotting platelets. When severe and uncontrolled, ITP can force patients to have their spleen removed.
The first study in ITP, completed last year using efgartigimod delivered via an intravenous infusion, was a success. This second study used a newer version of the drug delivered by a simpler skin injection, but its failure is now likely to delay or derail Argenx’s plan to seek approvals in the U.S. and Europe.
An Argenx spokesperson said the company is still evaluating the data from the ADVANCE-SC study, and has not made any decisions on next steps for its ITP clinical program.
Argenx secured an initial approval for efgartigimod in December 2021 to treat patients with myasthenia gravis, a chronic autoimmune, neuromuscular disease that causes progressive weakness in the skeletal muscles. The drug is sold under the brand name Vyvgart. Sales totaled $441 million in 2022 and $851 million in the first nine months of this year.
“Based on today’s data, we expect ITP [sales] forecasts to be removed for the US/EU,” said J.P. Morgan analyst James Gordon, in a research note. But Gordon also noted that investor expectations for the commercial potential of efgartigimod in ITP were relatively muted, and that the drug’s potential to expand into other autoimmune diseases was more compelling.
Argenx is conducting a late-stage clinical trial of efgartigimod in pemphigus vulgaris, another type of autoimmune disease that causes blisters on the skin and mucous membranes. A readout from the study is expected by the end of the year.
In the ADVANCE-SC study announced Tuesday, 14% of the ITP patients treated with efgartigimod demonstrated a sustained platelet count response compared to 16% of placebo patients.
Argenx’s spokesperson said the company has not determined why the placebo in the study performed better than its drug, noting that the placebo response was much higher than what was reported in the first ITP study. Based on measurements of drug levels in the blood, the company does not believe that switching to a skin-injection formulation of efgartigimod from an intravenous infusion contributed to the study’s failure.
In the first study, presented last December, 22% of patients administered infusions of efgartigimod achieved a sustained platelet response compared to 5% of patients given a placebo.
The commercial success of Vygart has helped Argenx become one of the most valuable biotech companies in Europe. Prior to Tuesday’s setback, the stock was up 31% for the year, giving the company a market value of just under $30 billion. Argenx continues to study efgartigimod in 13 different autoimmune diseases.