FDA approves injectable form of argenx’s myasthenia gravis drug Vyvgart

The Dutch biotech company argenx won FDA approval on Tuesday for an easier-to-administer version of its autoimmune disease drug efgartigimod. The new version, marketed at Vyvgart Hytrulo, will be available in July.

Vyvgart was previously approved in late 2021 as an intravenous infusion for people with generalized myasthenia gravis, a condition in which a person’s own immune system errantly makes antibodies that attack their muscles. The disease can make moving, speaking, and swallowing difficult and becomes life-threatening when it impedes breathing.

Sales of the Vyvgart, which was the company’s first product, have increased steadily each quarter since its launch nearly 18 months ago. Argenx recorded sales of $401 million from the drug last year and $218 million in the first quarter of 2023.

“I was holding my breath because the odds are against you as a biotech company when you’re launching your own products, but the commercial team did a phenomenal job,” argenx CEO Tim Van Hauwermeiren told Endpoints News. “We are on track to become a blockbuster drug pretty fast.”

Injected in seconds versus infusion over an hour

The new version can be injected under the skin by healthcare professionals, which takes between 30 to 90 seconds, compared with an hour-long infusion. As of the end of last year, about 3,000 of the estimated 17,000 eligible myasthenia gravis patients in the US were getting Vyvgart infusions, and argenx hopes the new, easier-to-use injections will encourage more neurologists to prescribe the drug.

James Howard

“It doesn’t offer any more or any less efficacy, but allows patients now to have freedom of choice,” said James Howard Jr, a neurologist at the University of North Carolina School of Medicine, who led both clinical studies.

Van Hauwermeiren said both formulations would cost the same, at roughly $225,000 a year for the typical patient, although that varies depending on how frequently the drug is needed. Vyvgart is initially administered once a week for 4 weeks. He said that some patients need to start a new cycle within a couple of weeks, while others can go a few months or even longer before requiring another round.

The subcutaneous injection is made with technology from the San Diego biotech Halozyme, which has helped breathe new life into the sales of old drugs by reformulating them into injectables. But Van Hauwermeiren said he didn’t want to wait to make both forms of Vyvgart available. “We want to have the broadest offering as early as possible here,” he said.

Infusions and injections of Vyvgart are both approved for people who test positive for antibodies that target their acetylcholine receptors at the junction of nerves and muscles. The drug lowers the levels of immunoglobulin G antibodies, which includes the autoimmune disease-causing autoantibodies, thus reducing muscle weakness but possibly increasing the risks of infection.

More specifically, Vyvgart targets the so-called neonatal Fc receptor, or FcRn, responsible for rescuing antibodies from cellular recycling centers that break down old proteins for parts. By blocking the receptor, Vyvgart helps cells remove antibodies, good and bad alike, more quickly. It’s the first, and so far only, approved FcRn inhibitor.

‘Just scratching the surface’

In the company’s previous clinical trial, 68% of myasthenia gravis patients who got Vyvgart infusions had a statistically significant improvement in activities of daily living score compared with 30% for those who got a placebo. For the injectable version, argenx submitted data to the FDA showing that the drug reduced antibody levels similar to the infused product.

“The idea is to reach more patients,” Van Hauwermeiren said. “We are just scratching the surface.”

Howard noted that when Vyvgart works, the results often seem rapid compared with traditionally prescribed immunosuppressants, which can take 6 to 12 months to start working and a couple of years or longer for the full benefits to kick in.

“With Vyvgart, I’m seeing an effect with a single injection and maximum improvement within four to five weeks, which is just unheard of in our space,” Howard said. “But not everybody responds, and we’re trying to work out why.”

Argenx isn’t sharing sales projections yet, in part because it’s awaiting results later this year from advanced studies testing the drug in other conditions, Van Hauwermeiren said. “We expect so many launches that it’s very difficult to come up with a credible guidance.”

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