Prolium Bioscience, a New York-based clinical-stage biotech, has raised $50M in Series A funding led by RTW Investments. The company develops PRO-203, a bispecific CD20xCD3 T-cell engager designed for deep B-cell depletion in severe autoimmune diseases like systemic sclerosis and lupus nephritis. The capital will fund ongoing clinical studies and a multinational Phase 1/2 trial in systemic sclerosis starting Q2 2026.
TCEs Target Autoimmune After Oncology Wins
The raise arrives amid a funding surge for T-cell engagers in autoimmunity. Candid Therapeutics, developing a similar CD20xCD3 bispecific, announced a $505M PIPE alongside a merger with Rallybio on March 1, 2026. Prolium differentiates by already dosing patients in two studies, including five with refractory lupus nephritis, while leveraging oncology data showing 59% complete response rates.
Few Options for Refractory SSc Patients
Systemic sclerosis affects 2.5 million worldwide, with therapeutics projected at $2.88B in 2026 growing at 6.2% CAGR. Current treatments fail refractory cases, where skin fibrosis progresses despite immunosuppressants. CAR-T therapies show promise but face scalability issues; off-the-shelf T-cell engagers address this gap for tissue-penetrating B-cell depletion.
PRO-203 Repurposes Oncology Tech
PRO-203, in-licensed from KeyMed Biosciences and InnoCare Pharma, uses a CD20xCD3 format proven in non-Hodgkin lymphoma trials with 82% overall response rates. Unlike CAR-T, it requires no cell manufacturing, enabling broader access. Prolium optimizes it for autoimmune safety, targeting deep depletion in hard-to-reach tissues like skin and kidneys.
As Prolium CEO Scott Requadt noted:
"T-cell engagers are the next frontier in treating autoimmune disease, offering CAR-T-like efficacy without the logistical challenges."
This positions PRO-203 ahead of competitors like Dualitas Therapeutics, whose $65M Series A-funded bispecifics target inflammation via proximity mechanisms rather than T-cell redirection.
RTW Backs Proven Immunology Bets
RTW Investments led the round as sole investor, signaling conviction in T-cell engagers for autoimmunity. The firm, managing $10B AUM, drove Prometheus Biosciences to a $10.8B acquisition by Merck and backed Immunocore's IPO with its T-cell tech. RTW's portfolio overlap in Ventyx Biosciences underscores their autoimmune focus, providing Prolium full-lifecycle support through clinical milestones.
Autoimmune Market Draws Bispecific Capital
The autoimmune therapeutics market stands at $209.53B in 2026, expanding to $382.33B by 2032 at 10.52% CAGR. T-cell engagers, shifting from oncology, fuel this with oncology precedents like 10+ FDA approvals. Clasp Therapeutics raised $150M Series A for precision engagers, while Candid's $370M prior funding plus $505M PIPE highlights investor rush post-CAR-T successes in SLE.
Prolium enters as bispecifics gain traction, with prior China oncology data de-risking PRO-203's profile against rivals like Cullinan Therapeutics' BCMAxCD3 candidate.
Phase 1/2 Trial Targets SSc in Q2 2026
Prolium has dosed healthy volunteers in a single ascending dose study and five SLE/LN patients in an investigator-initiated trial. The $50M funds a multinational Phase 1/2 in systemic sclerosis starting Q2 2026, aiming to validate deep B-cell depletion in fibrotic tissues.