A New York biotech built around one molecule and one idea: reset the immune system by clearing the B cells that drive autoimmune disease.
The Prolium Bioscience wordmark. Founded 2025 in New York; backed by RTW Investments; led by CEO Scott Requadt. Its sole asset, PRO-203, entered the clinic in early 2026.
Most biotech companies begin with a scientist and a molecule, then go looking for money. Prolium Bioscience did it in a different order. An investment firm, RTW Investments, found a promising antibody in China, wrote the check, hired a veteran chief executive, and pointed the whole enterprise at a single disease with almost no good options.
Prolium Bioscience is a clinical-stage biotechnology company based in New York and incorporated in Delaware. Founded in 2025 and unveiled publicly in March 2026, it exists to develop one experimental therapy - PRO-203 - for people living with severe autoimmune diseases such as systemic sclerosis (scleroderma) and lupus. The company describes its purpose in four words: "Depleting Disease, Empowering Health."
What makes Prolium worth watching is not size. With roughly eight employees and $50 million in the bank, it is deliberately small. What makes it interesting is focus. The company has a single asset, a single mechanism, and a clear thesis about where the field of autoimmune treatment is heading - toward deep, controllable depletion of the B cells that misfire and attack a patient's own body.
The immediate customers are patients and the rheumatologists who treat them, along with the clinical trial sites - more than twenty of them, across at least five countries - now enrolling patients. The commercial customer does not exist yet, and will not unless PRO-203 works. That is the honest arithmetic of an early-stage biotech: everything depends on the data.
Figures reflect publicly disclosed information as of mid-2026. The $520M figure represents the maximum potential value of Prolium's antibody license: $17.5M in upfront and near-term payments plus up to $502.5M in milestones, alongside royalties and equity to the licensors.
In many autoimmune diseases, B cells - a type of white blood cell - become the drivers of damage, producing the antibodies and signals that turn the immune system against the body. Prolium's approach is to remove them.
PRO-203 is a bispecific antibody, meaning it grabs two targets at once. One arm binds CD20, a marker on the surface of B cells. The other binds CD3, found on T cells. By holding the two cells together, the drug forms what scientists call an immunological synapse and redirects the T cell to destroy the B cell through a process known as T-cell dependent cellular cytotoxicity.
The pitch is that this can be done "off the shelf." Unlike CAR-T cell therapies, which require harvesting and re-engineering a patient's own cells in a lengthy, individualized manufacturing process, PRO-203 is designed to be a subcutaneous injection - a shot, drawn from a vial, that any qualified clinic could in principle administer. If it delivers similar depth of B-cell depletion without the manufacturing burden, it could reach far more patients.
Originally developed in China as ICP-B02, PRO-203 was in-licensed by Prolium for all global non-oncology indications and ex-Asia oncology indications. The company is advancing it first in systemic sclerosis, then in lupus and additional autoimmune diseases. Administered subcutaneously, it is positioned as a scalable alternative to cell therapy for patients whose disease is driven by B cells.
People with severe, often treatment-refractory autoimmune disease - systemic sclerosis, lupus and lupus nephritis first, with more indications planned. These are conditions where existing options are limited and the need is acute.
Current B-cell therapies can be incomplete, and cell therapies like CAR-T are powerful but complex, costly, and slow to manufacture per patient. Prolium is targeting the gap between the two.
Prolium joins a wave of companies chasing B-cell depletion for autoimmune disease - CAR-T developers and other bispecific/T-cell engager programs. Its edge is a clinical-stage, off-the-shelf molecule and a tightly focused team.
Prolium is a venture-backed, single-asset biotech. It creates value not by selling a product today but by advancing PRO-203 through clinical milestones - each successful step de-risks the drug and raises the company's worth toward an eventual approval, partnership, or acquisition.
Bars are an illustrative representation of publicly described stage, not precise enrollment figures.
A life-sciences investor and operator, Requadt previously served as President and CEO of Talaris Therapeutics, where he led the company through its IPO. His earlier career spans venture roles at Clarus, business development, and a start as an attorney at Davis Polk & Wardwell. He holds an MBA from Harvard Business School.
A New York-based, full-life-cycle life sciences investment firm focused on transformational innovation in biopharma and medical technology. RTW created, seeded, and led Prolium's $50M Series A - an example of its model of building companies rather than only funding them.
Prolium describes its team as experienced entrepreneurs and clinicians in drug development, organized around a values framework it calls ARCH: Accountability, Resourcefulness, Collaboration, and Humility.
Prolium's antibody was not invented in New York. It came from two Chinese biopharma companies, and the deal that brought it west is the backbone of the whole company.
Co-developers of the CD20xCD3 bispecific (ICP-B02). In January 2025 they granted Prolium global non-oncology rights and ex-Asia oncology rights, in exchange for $17.5M upfront and near-term, up to $502.5M in milestones, tiered royalties, and a minority equity stake.
Financed the transaction and the company that would run the clinical program - turning a licensed molecule into an operating biotech with a leadership team and a multinational trial.
RTW Investments creates and backs the clinical-stage biotech, based in New York and incorporated in Delaware.
InnoCare Pharma and KeyMed Biosciences grant Prolium global non-oncology and ex-Asia oncology rights to ICP-B02 in a deal worth up to $520M.
Prolium emerges from stealth, discloses first patients dosed with PRO-203 across healthy-volunteer and lupus studies.
Prolium begins its multinational Phase 1/2 study (up to 24 patients, 20+ sites, 5+ countries) and completes follow-up in its lupus nephritis study.
It is a clinical-stage biotech developing PRO-203, a bispecific CD20xCD3 T-cell engager that depletes disease-driving B cells as an off-the-shelf therapy for severe autoimmune diseases like systemic sclerosis and lupus.
It binds CD20 on B cells and CD3 on T cells at the same time, forming an immunological synapse that redirects T cells to destroy the B cells. It is given as a subcutaneous injection rather than a custom cell therapy.
Prolium was founded and funded by RTW Investments and is led by CEO Scott Requadt, former CEO of Talaris Therapeutics. It launched with a $50 million Series A in March 2026.
Prolium in-licensed the antibody (originally ICP-B02) from China's InnoCare Pharma and KeyMed Biosciences, gaining global non-oncology and ex-Asia oncology rights in a deal worth up to $520 million.
As of mid-2026: healthy-volunteer dosing is complete, an investigator-led lupus nephritis study finished follow-up, and a multinational Phase 1/2 study in systemic sclerosis has dosed its first patient.
This profile summarizes publicly available information about Prolium Bioscience as of July 2026. Clinical development is early and outcomes are uncertain; figures such as the $520M license value reflect maximum potential payments, not guaranteed amounts. Sources include the company website, GlobeNewswire, BioSpace, Fierce Biotech, AllSci, FinSMEs, and PitchBook.