OS Therapies (OSTX) Investor presentation summary

Disease background and unmet need

• Osteosarcoma is a major pediatric bone cancer with ~1,000 US cases annually, primarily affecting ages 12–39.

• No FDA-approved treatments exist for recurrent, resected lung metastases; prognosis has not improved in 30 years.

• Systematic reviews highlight a lack of new therapies and justify the use of historical control data in trials.

OST31-164 innovation and mechanism

• OST31-164 is a first-in-class microbial vector gene therapy using attenuated Listeria encoding a chimeric fusion protein targeting Her2.

• Triggers multi-modal anti-tumor immune responses, including T cell and NK cell activation, and modulates the tumor microenvironment.

• Effective even with low or cytoplasmic Her2 expression, broadening applicability beyond antibody-based therapies.

Biomarker strategy and translational findings

• Gene transcript modulation is the preferred biomarker, capturing both innate and adaptive immune responses.

• Transcript upregulation after three doses correlates with outcomes in both canine and human trials.

• Comparative oncology studies in dogs demonstrate efficacy and parallel human disease biology.