Harbour BioMed announced on September 9, 2026 that its partner company Solstice Oncology has officially launched with a $225 million Series A financing round. RA Capital Management led the investment, and Canaan Partners, Forbion and other investors also participated. The new clinical-stage immuno-oncology company will focus on treating cancer earlier through neoadjuvant approaches and will pursue a global development strategy.
Financing and strategic focus
Solstice Oncology will apply the new capital to advance porustobart, its lead clinical candidate, across two neoadjuvant indications. The first indication is microsatellite-stable colon cancer, which represents the largest segment of colon cancer patients and has not yet benefited from immunotherapy. The company has not disclosed the second indication but said it is also being evaluated in the neoadjuvant setting.
Phase 2 trial plans
A Phase 2 trial is expected to open for enrollment early in the fourth quarter of 2026. The study will evaluate porustobart in combination with pembrolizumab in the neoadjuvant treatment of microsatellite-stable clinical stage II-III colon cancer. This design targets patients whose tumors remain less resistant and whose immune systems may mount a more effective response.
Clinical evidence for porustobart
Porustobart was discovered and developed by Harbour BioMed and previously carried the designation HBM4003 in its pipeline. In an earlier Phase 2 study, porustobart combined with the PD-1 inhibitor tislelizumab produced a 30 percent objective response rate among late-line patients with microsatellite-stable metastatic colorectal cancer without liver metastases. The median duration of response was 8.4 months, and the safety profile was considered favorable for continued development.
Partnership and commercial rights
In February 2026 Harbour BioMed entered into a license agreement and equity partnership with Solstice Oncology. Under the agreement, Solstice holds exclusive development and commercialization rights to porustobart outside Greater China. The arrangement is intended to support global advancement of the program while preserving Harbour BioMed's role as the originating company and active partner.
Leadership views on earlier treatment
Dr. Jingsong Wang, Founder, Chairman and CEO of Harbour BioMed, said the company is pleased to see Solstice launch with strong support from leading investors. He noted that Harbour BioMed looks forward to supporting the continued development of this differentiated CTLA-4 antibody. He added that the ultimate goal remains exploring its potential to benefit patients worldwide across multiple oncology indications.
Caroline Loew, PhD, CEO of Solstice Oncology, said the greatest opportunity in oncology lies in treating disease earlier, when the tumor is still present and the immune system is intact. She explained that an early immuno-oncology combination may allow the immune response to act systemically against micrometastatic disease beyond the primary tumor. Since February, the company has filed and cleared an IND and advanced directly into a Phase 2 trial, with data anticipated in the second half of 2027.
The launch of Solstice Oncology and its $225 million Series A round underscore continued investor confidence in earlier cancer treatment strategies and differentiated immuno-oncology assets across the sector. With porustobart already in clinical development and a Phase 2 trial nearing enrollment, the company is positioned to generate important data on neoadjuvant CTLA-4 blockade. The first clinical readout is expected in the second half of 2027 and could help clarify whether this approach improves outcomes for patients with colon cancer.