Solstice Oncology has launched with a $225 million Series A financing led by RA Capital Management, with participation from Canaan Partners, Forbion and other investors.
The clinical-stage immuno-oncology company is focused on treating cancer earlier in the disease course through neoadjuvant therapy, with its initial development program centered on porustobart.
Porustobart is a second-generation, Fc-enhanced CTLA-4 antibody being advanced across two clinical indications. One program targets microsatellite-stable clinical stage II-III colon cancer, while the second indication has not been disclosed.
Solstice plans to open enrollment for a Phase 2 study early in the fourth quarter of 2026, evaluating porustobart in combination with pembrolizumab as neoadjuvant therapy for MSS colon cancer.
Porustobart was originally discovered and developed by Harbour BioMed. In February 2026, Harbour BioMed entered into a license and equity partnership granting Solstice exclusive rights to develop and commercialize the therapy outside Greater China.
In an earlier Phase 2 trial conducted by Harbour BioMed, porustobart combined with tislelizumab generated a 30% objective response rate in late-line MSS metastatic colorectal cancer patients without liver metastases, with a median duration of response of 8.4 months.
Solstice expects data from its upcoming Phase 2 program in the second half of 2027.
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“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.”
Dr. Jingsong Wang, Founder, Chairman and CEO of Harbour BioMed
“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.”
Caroline Loew, PhD, CEO of Solstice Oncology
