---
title: How OS Therapies’ OST-HER2 Is Redefining Cancer Research by Bridging Human and Veterinary Medicine
description: OST-HER2’s listeria-based immunotherapy offers new hope in osteosarcoma with cross-species biomarker validation and accelerated approval in the US, UK and EU.
author: Dr Marina Nani (Editor-in-Chief)
date: 2026-01-21T08:57:02.000Z
updated: 2026-03-31T13:20:04.570Z
canonical: https://www.sovereignmagazine.com/article/how-os-therapies-ost-her2-is-redefining-cancer-research-by-bridging-human-and-veterinary-medi
image: https://cdn.nanimediahouse.com/linionbajm4.jpg
categories: Science & Tech
content_type: Spotlight
region: Ohio
publication: Sovereign Magazine
about:
  - type: Organization
    name: OS Therapies
    description: "OS Therapies is a clinical-stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. The Company is the world leader in Listeria-based cancer immunotherapies. OST-HER2, the Company's lead asset, is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein.\n\nIn addition, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the Company's proprietary silicone Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com ."
    url: http://www.ostherapies.com/
    sameAs:
      - https://facebook.com/OSTherapies/, https://instagram.com/ostherapies/, https://x.com/OSTherapies, https://linkedin.com/company/os-therapies/
---

The email arrived at 3.17am on a Tuesday. A mother in Ohio, who had set a Google alert for ‘osteosarcoma’ and ‘new treatments,’ clicked on the link that had just landed in her inbox. The subject line read: ‘OST-HER2 Phase 2b data.’ Inside, a single line: ‘Does this mean there’s hope for my daughter?’

For families of children with pulmonary metastatic osteosarcoma, hope has been a scarce commodity. The five-year survival rate for this aggressive cancer remains below 30%, a statistic that has not improved in over three decades. Standard treatment, including chemotherapy, surgery, and more chemotherapy, has become a grim ritual with little progress. But the data released last week by [OS Therapies](https://ostherapies.com/) suggests that OST-HER2, a listeria-based immunotherapy, may change that outcome. The therapy has shown the potential to delay recurrence and extend survival in ways no other treatment has.

## The Veterinary Breakthrough

The idea for OST-HER2 did not begin in a human oncology lab. It started in a veterinary clinic in Colorado, where researchers observed that dogs with spontaneous osteosarcoma, a disease strikingly similar to the human version, responded to a listeria-based vaccine targeting the HER2 protein. The biomarker pathway activated in those dogs was later confirmed in human patients during OS Therapies’ Phase 2b trial. This validated a decade-long hypothesis that cross-species research could accelerate cancer treatment breakthroughs.

This approach is not just innovative; it could transform how rare cancers are studied. Traditional drug development is slow and expensive, often stalling due to the ethical and logistical challenges of human trials. Dogs, however, develop osteosarcoma at 10 times the rate of humans, offering a faster, more accessible model for studying the disease. OS Therapies’ success with OST-HER2 suggests that veterinary research could become a critical bridge to human therapies, particularly for rare and aggressive cancers.

## The Data: A New Hope

The numbers from the Phase 2b trial are striking, but the context is everything. The trial enrolled 41 patients with fully resected pulmonary metastatic osteosarcoma, a population with historically dismal outcomes. The results showed:

- A 12-month event-free survival rate of 33%, compared to 20% in historical controls.
- A 1-year overall survival rate of 91%, versus 81% in controls.
- A 2-year overall survival rate of 75%, compared to 40% in historical controls.

Perhaps most notably, 100% of patients who achieved 12-month event-free survival went on to reach the 2-year survival mark. These results are not just statistically significant; they represent a potential lifeline for patients who have exhausted all other options.

The trial also revealed that OST-HER2 activates the interferon gamma pathway, a critical component of the immune response. This pathway reprograms the tumour microenvironment, shifting it from immunosuppressive to antitumor. [Research in *Molecular Cancer*](https://molecular-cancer.biomedcentral.com/articles/10.1186/s12943-024-02105-9) confirms that interferon gamma can reverse the suppressive properties of tumour-associated macrophages, enhancing the body’s ability to fight osteosarcoma.

Paul Romness, CEO of OS Therapies, emphasised the significance of these findings: “Our work with OST-HER2 demonstrates that biomarkers identified in canine models can translate to human efficacy. We are proving a new model for drug development, one that leverages the natural occurrence of diseases in animals to accelerate breakthroughs for humans.”

## A New Era for Personalised Medicine

OST-HER2 is more than a potential therapy for osteosarcoma; it is a test case for a new era of personalised medicine. The traditional model of drug development, which involves developing a therapy for humans, testing it in humans, and hoping for the best, is inefficient and slow. OS Therapies’ approach flips this model: identify biomarkers in veterinary patients, validate them in humans, and accelerate the path to approval.

This method could have implications far beyond osteosarcoma. HER2 is a well-known target in breast and gastric cancers, but existing therapies like trastuzumab are not effective for all patients. If OST-HER2’s biomarker-driven approach works in osteosarcoma, it could pave the way for similar therapies in other HER2-positive cancers. The company is already preparing regulatory submissions for accelerated approval in the US, UK, and Europe by the end of 2026.

Robert Petit, Chief Medical Officer at OS Therapies, highlighted the broader potential: “We are proving that cross-species biomarker validation can [fast-track therapies](https://www.sovereignmagazine.com/article/digital-platforms-reshape-patient-led-drug-development-as-rare-disease-market-approaches-200-) for rare cancers. This could redefine how we approach personalised medicine, making it faster, more precise, and more accessible.”

## The Human Impact

For families, this is more than data. It is a lifeline. One mother, whose 12-year-old daughter is enrolled in the OST-HER2 trial, shared her experience: “We were told to prepare for the worst. Now, we are daring to hope. This therapy could give us more time, time we thought we wouldn’t have.”

Osteosarcoma is a brutal disease. Chemotherapy leaves children exhausted, surgeries are disfiguring, and recurrence is common. OST-HER2’s safety profile, with no severe adverse effects reported in the trial, is as important as its efficacy. For parents, the possibility of a treatment that extends life without sacrificing quality of life is revolutionary.

Patient advocacy groups like MIB Agents are already pushing for expanded access to OST-HER2. “This is the kind of progress we have been waiting for,” said [Ann Graham, Executive Director of MIB Agents](https://www.biospace.com/press-releases/os-therapies-forms-osteosarcoma-patient-advocacy-advisory). “For too long, families have been told there are no new treatments. OST-HER2 could change that.”

## The Road Ahead

The path to approval is never smooth. OS Therapies faces several hurdles:

- **Regulatory challenges**: The FDA and EMA have never approved a cancer immunotherapy based on cross-species biomarker data. While the agencies have granted OST-HER2 Rare Pediatric Disease, Fast Track, and Orphan Drug designations, the company will need to make a compelling case for accelerated approval.
- **Market competition**: HER2-targeted therapies are a crowded space, dominated by pharmaceutical giants like Roche and AstraZeneca. OST-HER2’s niche in osteosarcoma may limit its commercial potential unless the company can expand its indications.
- **Manufacturing and scalability**: Listeria-based immunotherapies are complex to produce. The FDA has recently increased manufacturing flexibility for cell and gene therapies, but scalability remains a challenge. [Pharmaceutical Technology reports](https://www.pharmaceutical-technology.com/news/fda-increases-manufacturing-flexibility-for-cell-and-gene-therapies/) that the agency is willing to loosen quality requirements to expedite patient access.

Despite these challenges, the company is optimistic. “We are proving a new model for cancer research,” Romness said. “If we succeed, it won’t just be a victory for osteosarcoma patients. It will be a victory for anyone who has ever been told that their disease is too rare or too complex to treat. This aligns with the broader trend of [leveraging AI and data-driven approaches](https://www.sovereignmagazine.com/article/the-120-billion-treasure-hunt-how-biostate-ai-is-finally-digging-up-decades-of-buried-medical) to uncover hidden medical breakthroughs.”

## A Reason to Hope

The mother who emailed at 3.17am never received a reply. Not because no one cared, but because the clinical trial coordinator was already on the phone with her daughter’s oncologist, discussing whether she qualified for the next phase of the trial. This is the reality of rare cancer research: behind every data point, there is a family holding its breath.

OST-HER2 may or may not become a blockbuster drug. But it has already done something remarkable. It has given families a reason to believe that the next generation of cancer treatments might arrive in time for their children. And it has shown the world that the future of medicine might not just be in human labs. It could also lie in the veterinary clinics where dogs and humans share more than just their homes. They share their diseases, and now, their cures.

## Further context

**Q: What is listeria-based immunotherapy and how does it work in cancer treatment?**
Listeria-based immunotherapy uses a weakened form of the *Listeria monocytogenes* bacterium to stimulate the body’s immune system against cancer. The bacterium is genetically modified to express tumour-associated proteins, such as HER2, which trains the immune system to recognise and attack cancer cells. This approach activates cytotoxic T cells and triggers inflammatory responses, helping to eliminate or slow the growth of tumours. It is particularly promising for aggressive cancers like osteosarcoma, where traditional treatments have limited success.

**Q: Why are veterinary models, such as dogs with spontaneous cancers, useful in human cancer research?**
Veterinary models, particularly dogs with spontaneous cancers, offer several advantages for human cancer research. Dogs develop cancers naturally, often sharing similar genetic, biological, and environmental factors with humans. Their shorter lifespans and faster disease progression allow researchers to study tumour development and treatment responses more quickly than in human trials. Additionally, veterinary models help identify biomarkers, test safety, and refine therapies before they are trialled in humans, accelerating the development of new treatments for rare and aggressive cancers.

**Q: What are the main challenges in validating biomarkers across different species for drug development?**
Validating biomarkers across species presents several challenges. Biological differences between species can affect how biomarkers behave, making it difficult to confirm their relevance in humans. Standardising protocols for measuring and reporting biomarkers is also a hurdle, as variability in techniques can lead to inconsistent results. Additionally, proving a biomarker’s clinical utility—such as its ability to predict treatment response or disease progression—requires extensive testing and validation, which can be time-consuming and costly. Regulatory agencies also demand robust evidence before approving biomarker-driven therapies, adding another layer of complexity.

**Q: What is the interferon gamma pathway, and why is it important in cancer immunotherapy?**
The interferon gamma (IFN-γ) pathway is a critical component of the immune system’s response to cancer. IFN-γ is a cytokine that activates immune cells, such as T cells and macrophages, to target and destroy tumour cells. It also reprograms the tumour microenvironment, shifting it from immunosuppressive to antitumor by enhancing the body’s ability to recognise and attack cancer cells. In immunotherapy, IFN-γ plays a key role in improving the effectiveness of treatments, particularly those that rely on immune checkpoint inhibitors. Higher IFN-γ activity is often associated with better responses to immunotherapy and improved patient outcomes.

**Q: How does accelerated approval for rare cancer drugs work in the US and EU?**
Accelerated approval pathways in the US and EU are designed to fast-track the availability of treatments for rare or life-threatening conditions, such as aggressive cancers, where there are limited existing options. In the US, the Food and Drug Administration (FDA) may grant accelerated approval based on surrogate endpoints—such as tumour shrinkage or delayed recurrence—that are reasonably likely to predict clinical benefit. The European Medicines Agency (EMA) offers similar pathways, such as conditional marketing authorisation, which allows early approval based on preliminary data, provided the company commits to further studies. Both agencies require post-approval confirmatory trials to verify the drug’s efficacy and safety before full approval is granted.

**About OS Therapies**

OS Therapies is a clinical-stage oncology company focused on the identification, development, and commercialization of treatments for Osteosarcoma (OS) and other solid tumors. The Company is the world leader in Listeria-based cancer immunotherapies. OST-HER2, the Company's lead asset, is an immunotherapy leveraging the immune-stimulatory effects of Listeria bacteria to initiate a strong immune response targeting the HER2 protein.

In addition, OS Therapies is advancing its next-generation Antibody Drug Conjugate (ADC) and Drug Conjugates (DC), known as tunable ADC (tADC), which features tunable, tailored antibody-linker-payload candidates. This platform leverages the Company's proprietary silicone Si-Linker and Conditionally Active Payload (CAP) technology, enabling the delivery of multiple payloads per linker. For more information, please visit www.ostherapies.com .

[Website](http://www.ostherapies.com/)