OST-HER2 pursues accelerated approval in pediatric osteosarcoma; BLA acceptance and regulatory conversion will determine whether Phase 2b data translates to a first approval

Bull

A successful BLA submission followed by FDA acceptance triggers the accelerated approval pathway, with seroconversion as a surrogate endpoint already aligned with regulators. A positive outcome would establish OST-HER2 as the first approved therapy specifically for recurrent, fully resected, lung metastatic osteosarcoma, generate Priority Review Voucher eligibility (with recent PRV sales near $160M providing meaningful non-dilutive value), and validate the parallel EMA rolling review and MHRA ATMP pathway as a multi-market commercial story.

Bear

The BLA has already slipped once from a January 2026 target to H2 2026, signaling execution risk in dossier assembly. The most likely failure modes are a Refuse-to-File decision from FDA citing insufficient clinical data from a single-arm Phase 2b trial, questions about the durability or clinical meaningfulness of the seroconversion surrogate endpoint, or a Complete Response Letter requesting additional evidence before acceptance — any of which would reset the timeline materially and pressure a balance sheet dependent on small dilutive financings.