FDA puts hold on Rapt trials of drug for eczema, asthma

Dive Brief:

• Shares of Rapt Therapeutics fell sharply Tuesday after the company disclosed U.S. regulators ordered a halt of two studies testing a drug the biotechnology company is developing for eczema and asthma.

• The clinical hold is due to a serious adverse event of liver failure in one of the trial participants. While the cause is unknown, investigators considered the case possibly related to Rapt’s treatment. The company has halted dosing and patient enrollment in both trials.

• The participant had a “complex medical history,” Rapt said, including a COVID-19 infection and concomitant use of a herbal supplement associated with liver toxicity. The person was also allergic to Dupixent, a widely prescribed medicine for both eczema and asthma.

Dive Insight:

Analysts have followed Rapt as they view its drug, an oral pill dubbed zelnecirnon, as a possible competitor to Dupixent in conditions like eczema.

Dupixent, which was developed by Sanofi and Regeneron, is a multibillion-dollar product approved for a range of inflammatory diseases. Sales are expected to increase further still; Sanofi recently forecast the eczema market as likely to grow as fast as that of psoriasis.

As an oral medicine, Rapt’s treatment could represent a more convenient option than injectable medicines like Dupixent for moderate-to-severe cases of eczema.

However, the safety setback could potentially derail those plans, or at least delay them. Shares plummeted by two-thirds in Tuesday morning trading.

“This is an unfortunate and unexpected event, and we are working diligently to get more information on this case,” said Brian Wong, Rapt’s CEO, in a statement. “Patient safety is our top priority and we will work with the FDA to resolve this as quickly as possible.”

So far, the company has only received verbal notice of the hold from the FDA, but it expects to receive a formal letter with more details.

In the meantime, Rapt said it’s undertaking a “thorough investigation” of the case. The company noted that, across the roughly 350 participants in three trials of zelnecirnon, no other evidence of liver toxicity has been reported.

Last November, Rapt said it expected to report out results from the Phase 2b trial of its drug in asthma by the middle of this year.

Other companies are also working to develop oral alternatives for conditions like eczema. Sanofi is one of them, working with Kymera Therapeutics on a drug that’s now in a Phase 2 trial. The French pharmaceutical firm estimates peak annual sales of between 2 billion and 5 billion euros, or between $2.16 billion and $5.41 billion.

The drug is also being tested for chronic skin condition known as hidradenitis suppurativa.

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