RA Capital Leads $225M Series A for Solstice Oncology
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Solstice Oncology, an immuno-oncology company working to treat cancer earlier in the neoadjuvant setting, has raised $225 million in Series A financing. The company is based in Boston, Massachusetts, and the round was reported on September 9, 2026.
RA Capital Management led the round. Canaan Partners, Forbion, and other investors participated.
The money will go toward advancing the company’s lead candidate, porustobart, across two clinical indications.
Led by CEO Caroline Loew, PhD, Solstice is organized around the neoadjuvant treatment window, the period before surgery, with the goal of improving cure rates and long-term survival. Porustobart is a second-generation, Fc-enhanced CTLA-4 antibody. It is currently in a Phase 2 trial in combination with pembrolizumab for clinical stage II-III MSS colon cancer, and the company is also pursuing a second, undisclosed indication.
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