Kymera Advances KT-621 Into Phase 2b Asthma Study, Targeting STAT6 in Type 2 Inflammation

Kymera Therapeutics has crossed a pivotal milestone by enrolling the first patient in its BREADTH Phase 2b clinical trial evaluating KT-621, an innovative oral degrader targeting STAT6 in patients with moderate to severe eosinophilic asthma. This advancement represents an important step in the development of the first STAT6-directed therapy to reach human evaluation, offering a new mechanistic approach to diseases driven by Type 2 immune responses.

Eosinophilic asthma remains a chronic inflammatory airway condition characterized by abnormal swelling and narrowing of the bronchial passages, often inadequately controlled by standard inhalers or injectable biologic therapies. The emergence of therapies targeting the IL-4/IL-13 signaling axis—the core driver of Type 2 inflammation—marks a significant expansion in treatment options for patients with insufficient response to existing modalities.

BREADTH Phase 2b Study: Design and Patient Selection Criteria

The BREADTH Phase 2b trial constitutes a large-scale, international, randomized, double-blind, placebo-controlled evaluation designed to enroll approximately 264 adult patients over a 12-week dosing period. The study’s patient population will be selected based on stringent biological criteria: an absolute blood eosinophil count of at least 300 cells/µL, a fractional exhaled nitric oxide (FeNO) measurement of 25 ppb or higher, and baseline lung function (FEV1) between 40% and 80% of predicted normal values.

The primary efficacy endpoint focuses on changes in forced expiratory volume in one second (FEV1) from baseline, while secondary assessments will evaluate safety tolerability, additional respiratory function measures, and patient-reported quality-of-life outcomes. The study is designed to identify the optimal dose for subsequent Phase 3 pivotal trials. Data readout from the BREADTH Phase 2b investigation is anticipated in 2027.

Parallel Phase 2b Strategy: Coordinating Asthma and Dermatitis Development

Kymera is executing a coordinated development approach through its BROADEN2 Phase 2b trial in moderate to severe atopic dermatitis patients, with results similarly expected by mid-2027. This parallel Phase 2b execution strategy across two Type 2-mediated indications aims to accelerate the drug development timeline and enable informed dose selection for Phase 3 registrational programs across the broader Type 2 disease portfolio. The synchronized approach reflects the shared pathophysiology of IL-4/IL-13-driven inflammation across multiple indications.

STAT6 Mechanism: First-in-Class Target Engagement

KT-621 represents a therapeutic innovation as the inaugural molecule designed to degrade STAT6—a transcription factor central to Type 2 immune signaling. Earlier Phase 1 data in atopic dermatitis patients demonstrated deep degradation of the STAT6 protein, robust suppression of disease-relevant biomarkers, clinically meaningful improvements in skin lesions and pruritus, and an encouraging safety profile. The once-daily oral administration route offers convenience advantages over injectable alternatives currently available for severe disease.

The targeting of IL-4/IL-13 signaling—the upstream driver of Type 2 inflammatory cascades—positions KT-621 to address the root biological mechanism underlying multiple disease manifestations including asthma, atopic dermatitis, and potentially additional Type 2-associated conditions.

Development Timeline and Financial Resources

Kymera ended 2025 with $1.6 billion in cash reserves, positioning the company with sufficient capital runway into 2029 to support ongoing Phase 2b trials and anticipated Phase 3 initiation. At the time of the last reported data, KYMR stock had traded between $19.44 and $103.00 over the preceding 12-month period, with the stock closing at $71.16, representing a decline of 1.37%, and subsequently rising in pre-market trading to $73.57, up 3.39%.

The parallel Phase 2b advancement in both asthma and dermatitis, combined with robust Phase 1 clinical signals, positions KT-621 as a potentially transformative approach to Type 2 inflammatory diseases currently dependent on older therapeutic modalities.