Solstice Oncology secures $225 million series A for immuno-oncology therapy

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."

For more information, please visit www.harbourbiomed.com

and www.solsticeoncology.com.