Mosaic Therapeutics to Present Poster Highlighting Preclinical Data for Lead Program MOS101 at the American Association for Cancer Research (AACR) Annual Meeting 2026

Key Takeaways

• MOS101 combines ASTX295 with FDA-approved olaparib.
• Preclinical data targets BRCA2‑mutant, TP53‑wild‑type tumors.
• ASTX295 completed Phase I in over 100 patients.
• Mosaic plans Phase 1b/2a trial by early 2027.
• Poster showcases Mosaic’s PRIME platform for combo discovery.

Summary

Mosaic Therapeutics will present preclinical data on its lead program MOS101—a combination of the next‑generation MDM2 antagonist ASTX295 and the FDA‑approved PARP inhibitor olaparib—at the AACR 2026 Annual Meeting. The poster focuses on BRCA2‑mutant, TP53‑wild‑type solid tumours and highlights the company’s PRIME discovery platform. ASTX295 has completed a Phase I trial in over 100 patients with a strong safety profile. Mosaic is finalising a Phase 1b/2a trial for MOS101, expected to start in early 2027.

Pulse Analysis

Mosaic Therapeutics, a clinical‑stage oncology company spun out of the Wellcome Sanger Institute, is leveraging its two‑decade‑old PRIME platform to design rational drug combinations. The centerpiece of its pipeline, ASTX295, is a next‑generation MDM2 antagonist that completed a Phase I trial in more than 100 patients with advanced solid tumours, demonstrating a short half‑life and minimal hematologic toxicity. By inhibiting MDM2, ASTX295 reactivates p53, a strategy validated across multiple cancer types and increasingly attractive for combination regimens.

The upcoming poster at the AACR 2026 meeting introduces MOS101, the preclinical pairing of ASTX295 with olaparib, an FDA‑approved PARP inhibitor. The data focus on tumours harbouring BRCA2 mutations while retaining wild‑type TP53, a biomarker profile that may amplify synthetic lethality when p53 is restored and DNA repair is blocked. Mosaic is finalising a Phase 1b/2a protocol slated for early 2027, positioning the combo as one of the first precision‑oncology regimens that couples a targeted MDM2 blocker with a PARP inhibitor in a defined genetic context.

If the clinical read‑out confirms the preclinical synergy, MOS101 could address a sizable unmet need in BRCA2‑mutant solid cancers, a market currently dominated by PARP monotherapies. The combination also differentiates Mosaic from competitors pursuing MDM2 inhibition, many of which remain single‑agent programs. Investors are likely to view the AACR presentation as a catalyst, potentially boosting Mosaic’s valuation ahead of the trial launch. Moreover, successful execution would validate the PRIME platform’s ability to generate high‑value, biomarker‑driven combos, encouraging further licensing and partnership opportunities.