Prolium Bioscience, a NYC-based clinical-stage biotechnology company, has raised $50 million in a Series A funding round led by RTW Investments (RTW).
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The company plans to use the funds to grow its operations and support research and development.
Prolium Bioscience, Inc., a clinical-stage biotechnology company, announced that it has initiated dosing healthy volunteers with PRO-203 in an ongoing single-ascending-dose study and expects to begin a multinational Phase 1/2 study for systemic sclerosis (SSc) in the second quarter of 2026.
The company has also treated five patients with advanced systemic lupus erythematosus (SLE) who did not respond to prior treatments and have lupus nephritis (LN) in an investigator-initiated study, with results to be presented at a future medical conference. Prolium also plans to start additional clinical studies this year for other severe autoimmune diseases, mainly driven by abnormal B-cells.
PRO-203 binds to CD20+ B cells and CD3 on T cells, bringing them together so that T cells can destroy B cells through a process called T-cell-dependent cellular cytotoxicity (TDCC). Prolium obtained global rights to use PRO-203 for non-cancer diseases and rights outside Asia for cancer treatments from KeyMed Biosciences and InnoCare Pharma. The drug was previously tested in a Phase 1/2 trial in China in patients with relapsed or refractory Non-Hodgkin Lymphoma (NHL), where it showed strong results, with a 59% complete response rate and an overall response rate of 82% in patients who received therapeutic doses.
“Scott Requadt, CEO of Prolium, said that T-cell engagers could be a new way to treat autoimmune diseases because they may remove B-cells in tissues deeply, similar to CAR-T therapy, but with fewer challenges. He added that CD20 is a well-proven target in B-cell-driven autoimmune diseases. Based on early safety and effectiveness data, the company believes PRO-203 could help achieve strong and long-lasting remission in patients. It may become an important treatment for scleroderma and other serious autoimmune diseases.”
“Peter Fong, Partner and President at RTW, said that PRO-203 could change how scleroderma and other serious autoimmune diseases are treated. He also said that Prolium’s team is making strong progress and is expected to produce important data on PRO-203 in several autoimmune diseases within the next two years.”
About Prolium Bioscience
Founded in 2025, Prolium Bioscience is a clinical-stage company developing PRO-203, a bispecific CD20xCD3 antibody that could become a leading treatment for systemic sclerosis and other severe autoimmune diseases. The company was founded and supported by RTW Investments and has built a team with strong experience in developing treatments for autoimmune diseases.
About RTW Investments, LP
RTW Investments, LP is a New York–based global investment firm that focuses on new and innovative developments in the biopharmaceutical and medical technology sectors. The firm works closely with industry and academic partners and uses its scientific expertise and investment approach to help develop and support companies that are creating new therapies.
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