Market reactionShares fell 15% on Nov 5.
OS Therapies develops OST-HER2 (Herlystic), a Listeria-based immunotherapy to prevent relapse in osteosarcoma after lung metastases are removed; it is not approved for people anywhere.
OST-HER2 is an immunotherapy for young patients whose osteosarcoma spread to the lungs and was removed. In a Phase 2b of 41 patients, 12-month event-free survival was 35% versus 20% for historical controls. That is single-arm evidence. The company plans a U.S. accelerated-approval filing and conditional applications in the U.K., EU and Australia in the fourth quarter of 2026. Cash was about $0.2 million at June 30, with going-concern doubt; an October warrant deal raised $7.2 million.
Thesis checklist
1 risk needs attention
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Next decision point
Tests: BLA is submitted
Does OS Therapies file a complete BLA this quarter, and does FDA accept it?
Strong, inconclusive and weak outcomes
What to look for in the result and how each would move the checklist
Price and material events
Select an event marker to read the update below. Marker colors show Thesis status.
OS Therapies plans four osteosarcoma filings this quarter on very little cash
Herlystic holds EMA rolling review and RMAT resubmission with $205K cash — survival financing determines whether approvals convert to a launch
OST-HER2 pursues accelerated approval in pediatric osteosarcoma; BLA acceptance and regulatory conversion will determine whether Phase 2b data translates to a first approval
OST-HER2's BLA submission and FDA Accelerated Approval decision will determine whether Phase 2b EFS data translates into the first approved therapy for resected recurrent osteosarcoma
About this history: every entry shows when the Thesis moved and what it said. The reasoning behind each move (the evidence, the analysis and the source filing) and the earnings write-ups are part of a subscription.
Dates, trials and completed outcomes are open to everyone. What each upcoming milestone hinges on is part of a subscription.
Disease areas: Lung cancer, Breast and gynecologic cancers, Gastrointestinal cancers, Other cancers
Catalyst calendar · Upcoming FDA decisions · Thesis changes
Competitive landscape
1 peers tracked
Cash: Market-data provider estimate; measurement period unavailable.
Debt: Market-data provider estimate; a complete comparable filing balance is unavailable.
Quarterly burn: Estimated from trailing free cash flow; measurement period unavailable.
Net cash and estimated runway require verified matching measurement periods. Missing debt components are not assumed to be zero.
Runway: No underlying guidance available.