Harbour BioMed Partner, Solstice Oncology, announces $225 Million Series A Financing to Advance Porustobart, a Neoadjuvant Immuno-Oncology Therapy

• Porustobart, a second-generation Fc-enhanced CTLA-4 antibody, is being advanced across two clinical indications in the neoadjuvant setting, beginning with MSS clinical stage II-III colon cancer
• Phase 2 trial of porustobart for colon cancer will be open for enrollment early in the fourth quarter of 2026
• Financing led by RA Capital Management, joined by Canaan Partners, Forbion and other investors

CAMBRIDGE, Mass., ROTTERDAM, Netherlands and SHANGHAI, Sept. 9, 2026 /PRNewswire/ -- Harbour BioMed (the "Company"; HKEX: 02142), a global biopharmaceutical company committed to the discovery and development of novel antibody therapeutics in immunology, oncology and other areas, today announced that Solstice Oncology, its partner company, has launched with a $225 million Series A financing led by RA Capital Management, with participation from Canaan Partners, Forbion and other investors. Solstice is a clinical-stage immuno-oncology company focused on treating cancer earlier, in the neoadjuvant setting.

Solstice is advancing its lead candidate porustobart, a differentiated, second-generation, Fc-enhanced cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody, across two clinical indications, one in microsatellite-stable (MSS) colon cancer and a second, undisclosed indication. Its Phase 2 trial is evaluating porustobart in combination with pembrolizumab in the neoadjuvant setting for the treatment of MSS clinical stage II-III colon cancer, the indication with the largest segment of colon cancer patients, which has yet to benefit from immunotherapy.

Porustobart was discovered and developed by Harbour BioMed. In February 2026, Harbour BioMed entered into a license agreement and equity partnership with Solstice Oncology for the exclusive development and commercialization of porustobart (also known as HBM4003 in Harbour BioMed's pipeline) outside Greater China, enabling the advancement of the program globally.

In a Phase 2 clinical study conducted by Harbour BioMed, porustobart in combination with tislelizumab, a PD-1 inhibitor, demonstrated a 30% objective response rate (7 of 23 patients) in late-line patients with MSS metastatic colorectal cancer without liver metastases, with responses showing encouraging durability. The median duration of response was 8.4 months, and porustobart demonstrated a favorable safety profile supporting its continued clinical development. These findings provide clinical support for further evaluating porustobart in combination with PD-(L)1 blockade and in earlier lines of treatment, including the neoadjuvant setting.

"We are pleased to see Solstice Oncology launch with strong support from leading investors and advance porustobart into the neoadjuvant setting," said Dr. Jingsong Wang, Founder, Chairman and CEO of Harbour BioMed. "As the originator of porustobart and a partner of Solstice, we look forward to supporting the continued development of this differentiated CTLA-4 antibody and exploring its potential to benefit patients worldwide."

"We believe the greatest opportunity in oncology lies in treating disease earlier, in the neoadjuvant setting, when the tumor is still present, the immune system is still intact, and disease hasn't yet hardened its resistance to treatment," said Caroline Loew, PhD, CEO of Solstice Oncology. "Treating patients early with an immuno-oncology combination therapy like the one we are evaluating in our Phase 2 trial could allow the immune response to act systemically, reaching micrometastatic disease well beyond the primary tumor, which is where we see the greatest opportunity to improve cure rates and long-term survival. Since founding the company in February, our team has moved with the speed and discipline this opportunity demands, filing and clearing an IND and now advancing directly into a Phase 2 trial, for which we anticipate data in the second half of 2027."

About Harbour BioMed

Harbour BioMed (HKEX: 02142) is a global biopharmaceutical company committed to the discovery and development of novel antibody therapeutics in immunology, oncology and other areas. The Company is building a robust portfolio and differentiated pipeline through internal R&D capability, strategic global collaborations in co-discovery and co-development, and selective acquisitions.

Our proprietary antibody technology platform, Harbour Mice^®, generates fully human monoclonal antibodies in both the conventional two heavy and two light chain (H2L2) format and the heavy chain-only (HCAb) format. Building upon HCAb antibodies, the HCAb-based immune cell engagers (HBICE^®) bispecific antibody technology enables tumor-killing effects that traditional combination therapies cannot achieve. The HCAb-based Antibody Plus technology (HCAb PLUS^TM) provides comprehensive modality solutions for the development of innovative multi-specific medicines in different disease areas. Additionally, building upon the Harbour Mice^® platform, Harbour BioMed launched its first fully human Generative AI HCAb Model powered by its Hu-mAtrIx^TM AI platform, accelerating the development of innovative therapies.

By integrating Harbour Mice^®, HBICE^®, HCAb PLUS^TM, a single B-cell cloning platform and AI technologies, Harbour BioMed has built a highly efficient and distinctive antibody discovery engine for developing next-generation therapeutic antibodies. For more information, please visit www.harbourbiomed.com.

About Solstice Oncology

Solstice Oncology is a clinical-stage immuno-oncology company built around the neoadjuvant treatment setting, the point in a patient's disease course where the company believes the opportunity to improve cure rates and long-term survival is greatest. Founded in February 2026, Solstice is led by a team with decades of experience building and advancing successful immunotherapy drugs in oncology. The company is advancing porustobart, a second-generation, Fc-enhanced CTLA-4 antibody, across two clinical indications: a Phase 2 study in combination with pembrolizumab in the neoadjuvant setting for clinical stage II-III MSS colon cancer, and a second, undisclosed clinical indication. Solstice's initial investors include RA Capital, Canaan Partners, and Forbion. For more information, visit www.solsticeoncology.com.

SOURCE Harbour BioMed