Immunotherapy Company Finds Rare Cancer Breakthrough in U.S.

1) James Guttman wrote this article for Streetwise Reports LLC and provides services to Streetwise Reports as an employee.

2)  This article does not constitute investment advice and is not a solicitation for any investment. Streetwise Reports does not render general or specific investment advice and the information on Streetwise Reports should not be considered a recommendation to buy or sell any security. Each reader is encouraged to consult with his or her personal financial adviser and perform their own comprehensive investment research. By opening this page, each reader accepts and agrees to Streetwise Reports' terms of use and full legal disclaimer. Streetwise Reports does not endorse or recommend the business, products, services or securities of any company. 

For additional disclosures, please click here.

OS Therapies Inc. (OSTX:NYSEAMERICAN) has formally requested a Type C meeting with the U.S. Food and Drug Administration (FDA) to align on the use of surrogate clinical endpoints for Breakthrough Therapy Designation and a conditional Biologics License Application (BLA) for its lead investigational immunotherapy, OST-HER2. This meeting request follows an invitation from the FDA dated April 2, 2025, and is expected to take place in the second quarter of 2025.

OST-HER2 is being developed to prevent or delay the recurrence of fully resected lung metastatic osteosarcoma, a rare and aggressive pediatric bone cancer. OS Therapies reported statistically significant results from a Phase 2b single-arm clinical trial involving 39 patients across 21 U.S. sites. The study met its primary endpoint of 12-month event-free survival (EFS), with a 33% response rate compared to 20% in historical controls (p=0.0158). The FDA previously advised against placebo-controlled trials for this condition due to ethical and feasibility concerns.

To support regulatory approval, the company launched OST-400, a retrospective longitudinal study involving more than 200 patient records from oncology centers in the U.S., U.K., and France. These records are being used to construct a matched external historical control cohort, addressing FDA feedback received during a prior Breakthrough Therapy Designation request.

OST-HER2 is a Listeria-based immunotherapy that stimulates HER2-specific T-cell responses to target cancer cells. It has received Rare Pediatric Disease Designation from the FDA. If a conditional BLA is granted before September 30, 2026, the therapy would qualify OS Therapies for a Priority Review Voucher (PRV). The most recent PRV sale, in February 2025, fetched US$150 million.

"Our clinical and regulatory teams are diligently preparing for the meeting and the subsequent BLA submission that is targeted to begin after the public release of additional clinical trial data at MIB Factor in June," said Dr. Robert Petit, Chief Medical & Scientific Officer, in a company news release.

The company currently has approximately US$7 million in cash and expects to fund operations into mid-2026. OS Therapies anticipates submitting a rolling BLA and, pending FDA alignment, aims to secure Accelerated Approval for OST-HER2 by year-end 2025.

Immunotherapy Innovation and Investment Trends in Oncology Biotech

The immunotherapy sector continued to expand its footprint in cancer treatment throughout early 2025, with a growing emphasis on precision approaches and immune-based technologies.

According to a February report from BioSpace, the U.S. immunotherapy drugs market was calculated at US$102.89 billion in 2025 and was expected to reach approximately US$464.06 billion by 2034. Monoclonal antibodies, particularly those used in cancer therapy, remained dominant, though the report also noted that vaccines were projected to grow rapidly within the space.

In a company update dated April 2, 2025, Brookline Capital Markets reaffirmed its Buy rating on OS Therapies and maintained a price target of US$9.00. 

In a March 18 interview with PharmaVoice, Jay Hartenbach, president of Diakonos Oncology, described the changing investment landscape and the growing role of non-traditional backers.

"With the VCs less interested, we're working with a variety of family offices in the SAFE round," he explained, referring to simple agreements for future equity. Hartenbach emphasized that high-net-worth individuals and family offices have become essential for companies pursuing riskier modalities, including therapies aimed at historically difficult targets. "They're willing to be more objective with the data without the bias of a track record," he said, adding that these investors often prioritize humanitarian goals alongside financial returns.

According to Hartenbach, the industry's contraction had led to more disciplined decision-making, especially around trial design and cost efficiency. "That increases discipline, and for companies that are really moving the needle, it filters out the noise," he noted.

On April 4, KuicK Research reported that the global bispecific antibody market had reached an estimated US$12 billion in 2024 and was projected to surpass US$50 billion by 2030. These antibodies are engineered to bind two distinct antigens, enhancing the immune system's ability to target cancer cells with precision. "Bispecific antibodies . . .  often connect immune effector cells directly to tumor cells or affected tissues to trigger a strong immune response," the report stated. It also highlighted the approval of 17 bispecific antibodies to date, underlining the segment's clinical maturity and commercial traction.

Trispecific antibodies — designed to engage three separate targets — remained in earlier stages of development but showed promise. More than 50 trispecific candidates were undergoing clinical trials globally. KuicK Research noted that trispecific antibodies may help address tumor heterogeneity and immune escape mechanisms, which have limited the effectiveness of some existing therapies.

Analyst Endorsements and Valuation Support for OS Therapies

In a company update dated April 2, 2025, Brookline Capital Markets reaffirmed its Buy rating on OS Therapies and maintained a price target of US$9.00. Analyst Kumaraguru Raja stated that OS Therapies was "advancing two platform technologies with significant potential," including OST-HER2 and the OST-tADC platform. He cited the successful achievement of primary endpoints in the Phase 2b osteosarcoma trial and emphasized ongoing regulatory discussions with the FDA, UK's MHRA, and EMA. According to Raja, "OST-HER2 is potentially expected to improve outcomes in osteosarcoma patients, a disease area with significant unmet need and market opportunity." The valuation was based on a discounted cash flow model with a 60% probability of success, peak US market penetration of 40%, and anticipated sales of US$400,000 per patient, leading to a projected enterprise value of US$216 million.

That same day, Lake Street Capital Markets released a report on OS Therapies with a Buy rating and a 12-month price target of US$19.00, as outlined in a report dated April 2, 2025. Analyst Chad Messer pointed to the positive Phase 2b data from OST-HER2, noting its 33% 12-month event-free survival rate and projected peak US sales exceeding US$400 million. Messer wrote, "We believe US and UK regulatory approval could come as early as 4Q [2025], with broader EU approval coming in 1Q [2026]." The firm also highlighted the company's RPDD status, enabling eligibility for a PRV that Messer estimated could be sold for approximately US$150 million. He valued OST-HER2 for human use at US$391 million and attributed an additional US$10 million to canine osteosarcoma licensing opportunities. Lake Street's valuation included contributions from future out-licensing of OS Therapies' tADC platform and potential expansion of OST-HER2 into HER2-positive breast cancer and other solid tumors.

According to an April 7 report from D. Boral Capital, OS Therapies received a Buy rating with a 12-month price target of US$20.00. Analyst Jason Kolbert highlighted that the company's investigational immunotherapy, OST-HER2, demonstrated a statistically significant 33% 12-month event-free survival rate in Phase 2b trials compared to 20% in historical controls. Kolbert stated that the data "suggest a meaningful clinical benefit in preventing recurrence of lung metastatic osteosarcoma." He also noted that OS Therapies held sufficient cash reserves to operate into mid-2026 and was "strategically positioned" to pursue regulatory milestones in 2025, including a rolling Biologics License Application (BLA) submission and a potential Accelerated Approval. The valuation included expectations for monetizing a Priority Review Voucher (PRV) and applying a 10% probability of success with a 30% discount rate, resulting in a modeled price target of US$20.00.

OS Therapies Targets Key Regulatory and Commercial Milestones

According to the company's February 2025 investor presentation, OS Therapies is pursuing multiple near-term milestones that could significantly impact its clinical and regulatory trajectory. These include the planned Type C FDA meeting and subsequent BLA submission in the first half of 2025, followed by potential Accelerated Approval before the end of the year.

OST-HER2 is positioned within a rare disease market with a reported total addressable market (TAM) of US$1.2 billion for human osteosarcoma. OS Therapies projects top-line revenue potential exceeding US$500 million annually for this indication alone. The therapy also has provisional approval from the U.S. Department of Agriculture for canine osteosarcoma, with a follow-on regulatory path pending.

The broader OST-HER2 development platform includes potential expansion into breast cancer and other HER2-positive solid tumors. In preclinical studies, OST-HER2 combined with HER2-targeting antibodies showed enhanced tumor suppression, including in models of brain metastases. A Phase 2 trial in breast cancer is anticipated for 2025.

In parallel, OS Therapies is developing a tunable antibody-drug conjugate (tADC) platform built around patented silicon linker technology. This system allows for interchangeable payloads and ligands, potentially improving safety, efficacy, and specificity in targeted cancer therapies. The tADC program includes candidates for ovarian, lung, and prostate cancers, with first-in-human trials expected in 2025.

As of its latest disclosures, OS Therapies holds over 20 issued patents across major markets and continues to engage with leading academic institutions and patient advocacy organizations to support the OST-HER2 program.

Ownership and Share Structure

Refinitiv lists management and insiders with a 21.01% ownership of OS Therapies Inc. Of them, Paul Romness owns 11.42%, Thomas Satterfield Jr has 5.85%, Theodore Search and John Ciccio hold 1.10% each.

12.95% of the company is owned by strategic entity Eindomil LLC. .67% is held by institutions and the rest is retail.

OS Therapies has 14.31 million free float shares, 21.66 million shares outstanding, and a market cap of US$30.33 million. Its 52 week range is US$1.36 - 1.56.