OST-HER2 Earns Rare Pediatric Disease Designation for Osteosarcoma

According to a November 3, 2021 news release from biopharmaceutical company OS Therapies, the company’s therapeutic candidate OST-HER2 (OST31-164 / Listeria monocytogenes) received Rare Pediatric Disease Designation from the FDA. The therapy is designed to help patients with osteosarcoma, a rare bone cancer. 


So what exactly is OST-HER2? The L. monocytogenes are injected into the body via a vaccine. According to OS Therapies, the treatment works by generating T-cells (a type of immune cell), which attack and destroy cancerous cells. As the cells are destroyed, spilling their contents, the immune system then focuses on destroying the contents. 

Thus far, OST-HER2 has received Orphan Drug designation in both the United States and European Union. While the treatment is not yet approved for humans, OST-HER2 has been approved to treat osteosarcoma in dogs. Studies highlight how treatment improved overall survival rates and reduced disease progression in canine patients. At the same time, OST-HER2 has been given to around 450 volunteers. Moving forward, OS Therapies will evaluate OST-HER2 in a Phase 2b clinical trial. 

Current therapeutic options for osteosarcoma include surgery and chemotherapy. OST-HER2 offers a potentially less invasive option. Additionally, patients whose cancer returns following treatment have a much worse prognosis. Thus, OST-HER2 also has the opportunity to fill an unmet need in this community. 

The Rare Pediatric Disease designation is granted to therapies intended to treat or prevent a rare pediatric disease. In this case, this is a serious or life-threatening condition affecting under 200,000 Americans aged 18 or under. The drug developer may then receive expedited review and a Priority Review voucher.


Also called osteogenic sarcoma, osteosarcoma is a rare cancer that manifests in areas where bone is quickly growing, such as the femur near the knee or the upper arm bone. Although this cancer is rare, it is also the most common bone cancer, especially in children. The average age of diagnosis is 15 years old. Risk factors include being male, radiation exposure, bone infarctions, or p53 gene mutations. Symptoms include:

  • Bone pain and tenderness
  • A warm mass or lump that can be felt through the skin
  • Limping or limited joint movement
  • Unexplained fever
  • Redness or swelling
  • Bone fractures or breaks with no clear reason
  • Pain which worsens at night or following exertion

Learn more about osteosarcoma.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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