- OS Therapies is a clinical-stage immuno-oncology company addressing a major unmet need in osteosarcoma and solid tumors. The Company is developing and commercializing novel treatments for osteosarcoma and other HER2-expressing solid tumors across pediatric and adult populations, targeting a market with no new approved osteosarcoma therapies in over 40 years and significant unmet need.
- The Company has built a diversified pipeline around two novel technology platforms: OST-Lm, a bioengineered form of Listeria monocytogenes designed to drive robust immune responses against HER2-expressing cancer cells; and OST-tADC, a next-generation tunable antibody-drug conjugate platform featuring a patented silicone-based component that enhances both safety and efficacy.
- The lead OST-Lm program—OST-HER2—is an off-the-shelf immunotherapy targeting HER2-expressing cancers. OST-HER2 is in clinical development for osteosarcoma and breast cancer, and holds conditional approval for canine osteosarcoma.
- The osteosarcoma program (lead indication in recurrent, resected lung-metastatic osteosarcoma) is the nearest to regulatory submission and has received the FDA’s rare pediatric disease designation, as well as orphan drug and fast track designations from the FDA and the European Medicines Agency (EMA).
- A Phase 2b trial of OST-HER2 in osteosarcoma has completed its treatment phase, showing statistically significant benefits in 12-month Event-Free Survival (EFS) (35% vs. ~20% historical; primary endpoint) and a strong early overall survival benefit (OS) (75% two-year OS vs. ~40% historical), alongside a favorable safety profile.
- OS Therapies believes that the demonstrated efficacy, favorable safety profile, and significant unmet clinical need in osteosarcoma support the potential for accelerated regulatory approval of OST-HER2, enabling advancement through the approval process without requiring a Phase 3 trial.
- The Company is preparing a rolling BLA submission for Q1 2026 with a targeted FDA Accelerated Approval decision in Q3 2026. OS Therapies is also preparing conditional MAA submissions to the UK’s MHRA and the EMA in Q1 2026.
- The osteosarcoma program (lead indication in recurrent, resected lung-metastatic osteosarcoma) is the nearest to regulatory submission and has received the FDA’s rare pediatric disease designation, as well as orphan drug and fast track designations from the FDA and the European Medicines Agency (EMA).
- OS Therapies is targeting the expansion of its Lm-platform into multiple high-value oncology indications through the development of additional product candidates: OST-AXAL (HPV-related cancers), OST-503 (NSCLC and glioblastoma), and OST-504/PSA (prostate cancer), along with additional preclinical programs targeting more than 30 solid tumor types.
- The Company also plans to create additional shareholder value through the proposed spin-off of its subsidiary, OS Animal Health (OSAH), which is developing OST-HER2 for canine osteosarcoma. OSAH plans to resubmit for USDA conditional approval in January 2026, with a potential commercial launch in 2026.
- OS Therapies is further advancing its proprietary OST-tADC platform, which is currently in preclinical development and is initially being evaluated for use in ovarian and breast cancers. The OST-tADC platform features patented pH-sensitive SiLinkers™ and CAP payloads, enabling precise payload release only in the tumor microenvironment, enhancing safety, reducing off-target toxicity, and enabling higher effective dosing.
- The Company established a dedicated subsidiary, OS Drug Conjugates, to support internal development of the platform and pursue future licensing or partnership opportunities.
- The Company established a dedicated subsidiary, OS Drug Conjugates, to support internal development of the platform and pursue future licensing or partnership opportunities.
- OS Therapies is led by a management team with a strong track record of drug development, commercialization, and multiple M&A exits. The Company is developing several potential revenue streams for 2026 and 2027, including its canine osteosarcoma product (2026), the potential sale of a Priority Review Voucher, and the market introduction of OST-HER2 in osteosarcoma (2027).
- In August 2025, the Company announced that its NYSE American listing (OSTX) was included in the Russell Microcap, Russell Microcap Value, and Russell Microcap Growth indexes.
- As of September 30, 2025, the Company reported cash of $1.876 million; subsequent to quarter-end, OS Therapies received an additional $1.5 million from the exercise of warrants.
Updated on January 9, 2026.
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