FDA Grants Fast Track Designation to KT-621 for Moderate to Severe Eosinophilic Asthma and Atopic Dermatitis

The U.S. Food and Drug Administration (FDA) has granted Fast Track designation to KT-621, an investigational oral therapy developed by Kymera Therapeutics, for the treatment of moderate to severe eosinophilic asthma, the company announced on April 13, 2026.

KT-621 is a first-in-class, once-daily oral small molecule degrader that targets STAT6, a central transcription factor involved in the signaling pathways of interleukin-4 (IL-4) and interleukin-13 (IL-13), which drive type II inflammation underlying eosinophilic asthma and atopic dermatitis.

The designation follows ongoing global Phase 2b clinical trials evaluating KT-621 in patients with moderate to severe eosinophilic asthma. One of these studies, the BREADTH trial, initiated in January 2026, is assessing the efficacy, safety, and tolerability of three dose levels of KT-621 over a 12-week treatment period in adult patients.

The primary endpoint of the BREADTH study is the percent change from baseline in pre-bronchodilator forced expiratory volume in one second (FEV1), a key measure of lung function. Secondary endpoints include a broad range of safety, efficacy, and quality-of-life assessments.

In addition to the asthma indication, KT-621 has previously received Fast Track designation from the FDA for the treatment of moderate to severe atopic dermatitis. The BROADEN2 Phase 2b trial for atopic dermatitis is ongoing, with data expected by mid-2027.

Fast Track designation is granted by the FDA to facilitate the development and expedite the review of drugs intended to treat serious conditions with unmet medical needs. The agency cited the potential of KT-621 to address gaps in current asthma therapies, particularly the need for effective, safe, and convenient oral treatment options.

While several therapies are approved for asthma, including inhaled corticosteroids and injectable biologics, many patients with moderate to severe disease remain inadequately controlled despite available treatments. Kymera Therapeutics highlighted that an oral therapy like KT-621 could reduce treatment burden and improve access for patients who may face challenges with inhaler technique or biologic administration.

Jared Gollob, MD, Chief Medical Officer of Kymera Therapeutics, emphasized the clinical need for novel approaches, stating that asthma is a chronic lung condition that can significantly disrupt daily life and, in severe cases, be life-threatening. He noted that KT-621 has the potential to reach more patients and improve disease control as a once-daily oral regimen.

KT-621 works intracellularly to degrade STAT6, distinguishing it from biologic therapies that act extracellularly. It is the first STAT6-directed therapy to enter clinical development, positioning it as a potentially paradigm-shifting agent across a range of inflammatory diseases driven by type II immunity.

Data from the BREADTH asthma trial are expected to be reported in late 2027. Kymera Therapeutics continues to advance KT-621 through clinical development for both eosinophilic asthma and atopic dermatitis under the Fast Track pathway.