Prolium Bioscience

About Prolium Bioscience

Prolium Bioscience is a clinical-stage biotechnology company developing therapeutics for severe autoimmune diseases. The company was founded in 2024 by the investment firm RTW Investments and launched in March 2026 with an initial $50 million Series A financing, also led by RTW. The CEO is Scott Requadt.

Prolium's primary focus is the clinical development of its lead asset, PRO-203, a bispecific CD20xCD3 T-cell engager antibody. The company's business model centers on in-licensing and advancing promising drug candidates. Prolium acquired the global rights for PRO-203 (also known as ICP-B02 or CM355) in all non-oncology indications and ex-Asia rights for oncology from KeyMed Biosciences and InnoCare Pharma. This licensing agreement involved an upfront payment of $17.5 million, with potential milestone payments reaching up to $520 million, in addition to tiered royalties on future sales. KeyMed and InnoCare also retain a minority equity stake in Prolium.

PRO-203 is designed to treat severe, B-cell-driven autoimmune diseases by binding to CD20 on B-cells and CD3 on T-cells. This mechanism redirects T-cells to eliminate the aberrant B-cells through T-cell-dependent cellular cytotoxicity. Prolium is initially targeting systemic sclerosis (SSc), with plans to initiate a multinational Phase 1/2 study in the second quarter of 2026. The company has also started dosing healthy volunteers in a single ascending dose study and plans to initiate further clinical studies in other severe autoimmune diseases. An investigator-initiated study is also underway to evaluate PRO-203 in patients with treatment-refractory, advanced systemic lupus erythematosus (SLE) and lupus nephritis (LN).