FDA places hold on Rapt Therapeutics trials

Feb. 21, 2024

Rapt Therapeutics, a San Francisco-based biotech specializing in immunology-based therapeutics, received FDA notification of a clinical hold on two mid-stage trials of the company's lead asset in atopic dermatitis and asthma.

The hold follows a serious adverse event of liver failure in a participant in the phase 2 atopic dermatitis trial, with a potential link to the company's CC4R inhibitor, zelnecirnon. Consequently, dosing of zelnecirnon in both trials has been suspended, along with enrollment of new participants. 

Approximately 350 patients have been enrolled across the zelnecirnon trials, with no observed liver toxicity in any other participants or in nonclinical studies. The company is conducting a thorough investigation into the specific case, which involves a patient with a complex medical history, including prior drug allergy, autoimmune disease and reported COVID-19 infection.

Rapt, formerly known as Flexus and majority-owned by Bristol-Myers Squibb, focuses on developing oral small molecule therapies for inflammatory diseases and oncology. The biotech's research centers on modulating immune drivers underlying these conditions, with zelnecirnon and tivumecirnon targeting C-C motif chemokine receptor 4 (CCR4) for treating inflammation and cancer, respectively.