Boston-based Hillstar Bio emerged Tuesday with $67 million in Series A funding to advance a precision immunology platform targeting pathogenic immune cells in autoimmune diseases. The company's approach aims to selectively deplete disease-causing cells while preserving healthy immune function, potentially offering more durable therapeutic responses than traditional immunosuppressive treatments.
Lead Program Targets TRBV9+ T Cells
Hillstar's flagship program, HSB-101, focuses on TRBV9+ T cells, a specific subset implicated in various autoimmune conditions. The initial indication is axial spondyloarthritis (AxSpA), a type of arthritis affecting the chest, spine, and pelvis. The company plans to enter clinical trials with HSB-101 in 2026.
"Our first program, HSB-101, is based on early clinical data that demonstrated efficacy of targeting pathogenic TRBV9+ T cells in AxSpA patients," said CEO Robert Mabry. "The interplay between HLA-B27 and TRBV9+ T cells in autoimmune conditions like AxSpA offers a unique opportunity for our lead program."
Proof-of-concept studies have shown significant therapeutic effects from targeting and selectively deleting these T cells, including putting a single patient with ankylosing spondylitis in remission for years.
Precision Approach to Immune Reset
Unlike traditional therapies that broadly suppress the immune system, Hillstar's platform selectively targets pathogenic cells while sparing healthy ones. This precision-driven approach holds the promise of providing durable relief and potentially reducing the long-term need for immunosuppressive therapies.
"Our innovative approach aims to deliver longer-lasting, more effective results compared to current treatments, improving patient outcomes and potentially reducing the long-term need for immunosuppressive therapies," Mabry stated.
The company's versatile approach leverages tailored discovery techniques for each therapeutic, free from the constraints of traditional drug development platforms. Work on additional indications beyond AxSpA is currently in the discovery stage, with plans to expand the portfolio to include precision immunology therapies for other autoimmune conditions associated with specific immune cell types.
Leadership and Investment
The Series A round was led by a syndicate of investors including Frazier Life Sciences, Droia Ventures, Novo Holdings A/S (the investment arm of Novo Nordisk), LifeArc Ventures, and Hummingbird Bioscience.
Hillstar's leadership team brings extensive industry experience. CEO Robert Mabry previously served as chief scientific officer at Orna Therapeutics and global head of biologics at Takeda. Chief Development Officer Mitchell Keegan was previously SVP of clinical development at Boston Pharmaceuticals, while Chief Operating Officer Lauren Mifflin serves as principal of company creation at Frazier Life Sciences.
"We are excited to collaborate with the Hillstar Bio team in bringing groundbreaking, precision-driven immunotherapies to patients living with autoimmune diseases," said Luc Dochez, Executive Chair at Hillstar Bio and Managing Partner at Droia Ventures. "Hillstar Bio has the critical elements necessary to transform autoimmune disease treatment, including top-tier antibody engineering capabilities, a deep understanding of immune cell biology, and an exceptional team of scientists, industry leaders, and advisors."
The funding will support advancement of the TRBV9 program through clinical proof-of-concept studies while enabling expansion of the company's broader precision immunology pipeline.
