Insilico Medicine Earns FDA Fast Track for AI Pan-TEAD Inhibitor ISM6331 in Mesothelioma

Insilico Medicine has announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation to ISM6331, an investigational pan-TEAD inhibitor being developed for adult patients with unresectable malignant pleural mesothelioma following progression on or after anti–PD-1 therapy. The designation also covers patients treated with or without anti–CTLA-4 therapy, and with platinum-based chemotherapy. For a disease with limited therapeutic options, the move signals regulatory momentum for a new targeted approach.

Fast Track is intended to expedite the development and review of therapies aimed at serious conditions with unmet medical needs. According to FDA policy, ISM6331’s designation reflects the agency’s recognition of potential clinical value, potentially enabling more intensive engagement during trial planning and biomarker strategy development.

The company positions ISM6331 as a candidate with “best-in-class” potential, engineered to rebalance the Hippo signaling pathway by targeting TEAD transcription factors. By restoring pathway balance, the program aims to suppress tumor growth and survival mechanisms associated with Hippo pathway dysregulation. The rationale is designed to support both monotherapy activity and combination strategies where resistance often limits efficacy.

ISM6331 was nominated in June 2023, with the molecular scaffold generated through Insilico’s Chemistry42 platform. Chemistry42 applies structure-based drug design and uses advanced scoring and reward pipelines to prioritize novel molecules, integrating generative chemistry techniques into the discovery workflow. This AI-driven design-to-prioritization framework underpins the candidate’s development pathway.

Insilico reports that ISM6331’s non-covalent structure is guided by Chemistry42, and preclinical studies suggest broad anti-tumor activity, potent effects at low doses, and a favorable safety profile with acceptable ADMET characteristics. The company also emphasizes synergistic anti-tumor effects and the potential to overcome drug resistance when used in combination therapy.

Previously, ISM6331 received FDA Orphan Drug Designation for mesothelioma in June 2024. Earlier designations related to other Insilico programs—such as Rentosertib (ISM001-055)—highlight the company’s growing regulatory footprint across oncology and beyond.

The Phase I first-in-human program for ISM6331 has advanced to the point where initial clinical data have been accepted for presentation in a brief oral format at the upcoming ESMO 2026 congress. In January 2025, Insilico states that the first patient was dosed in a global multicenter Phase I trial.

With Fast Track Designation, ISM6331 may be eligible—if criteria are met—for Rolling Review, Accelerated Approval, and Priority Review. Rolling Review could allow the submission of completed portions of an NDA or BLA to the FDA as they become available, potentially shortening time to regulatory consideration.

Overall, the company frames the FDA decision as validation of ISM6331’s clinical promise and as a pathway to accelerate development toward patients who need new treatment options in advanced mesothelioma.