Passage Bio (PASG) investor relations material

Transaction overview and structure

• Remix Therapeutics and Passage Bio plan to merge, creating a well-capitalized clinical-stage biotech focused on RNA processing therapies targeting disease drivers at their origin.

• The merger is supported by both boards, subject to stockholder approval, and expected to close in H2 2026.

• Pro forma ownership will be 92.6% Remix and 7.4% Passage, with $100M in concurrent financing and additional cash from Passage.

• Combined company will be funded into H1 2028, past key clinical milestones for lead asset REM-422.

• Remix management will lead the new entity, with a nine-member board designated by Remix.

Lead asset REM-422: clinical and commercial highlights

• REM-422 is a first-in-class MYB inhibitor for adenoid cystic carcinoma (ACC), showing a 43% ORR and 100% disease control rate in biomarker-positive patients.

• Phase 2 potentially registrational study in recurrent/metastatic ACC is ongoing, with >60% enrolled and full enrollment expected H2 2026.

• FDA authorized Phase 2 design includes recommended dose, biomarker-positive population, and single-arm study for potential registration.

• REM-422 is also in Phase 1 for AML/HR-MDS, with multiple responses observed and dose-dependent MYB mRNA reduction.

• U.S. commercial opportunity for REM-422 in ACC estimated at $600M+, with launch readiness targeted for 2028.

Clinical data and safety profile

• REM-422 demonstrated robust anti-tumor activity and durable responses in biomarker-positive ACC patients, with some on therapy for up to two years.

• Safety profile is favorable, with minimal Grade 3-4 treatment-related adverse events at the recommended Phase 2 dose (24mg).

• Target engagement confirmed by PK/PD data and biomarker-driven patient selection.

• Responses observed across ACC subtypes and after multiple prior therapies.

• No dose-limiting toxicities observed at any dose level.