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Solstice Oncology is testing porustobart, an antibody that releases a brake on the immune system, given with the immunotherapy pembrolizumab before surgery. Its first trial is in people with stage II to III colon cancer of the common type that has not usually responded to immunotherapy (microsatellite stable).
Solstice Oncology, Inc., at 200 Berkeley Street, Boston, Massachusetts, was built with RA Capital and founded in February 2026, according to the company, under chief executive Caroline Loew. It develops porustobart, a second-generation, Fc-enhanced, heavy-chain-only CTLA-4 antibody originally discovered by Harbour BioMed, which the company says has a shorter half-life than first-generation CTLA-4 antibodies and depletes regulatory T cells in the tumour. Porustobart is given with anti-PD-1 therapy in the neoadjuvant setting, before surgery: a phase 2 trial with pembrolizumab in microsatellite-stable clinical stage II to III colon cancer was due to open early in the fourth quarter of 2026, and a second, undisclosed early-stage indication is planned. Its first registered cancer trial, NCT07808151, was posted on ClinicalTrials.gov in September 2026. The company launched on 9 September 2026 with a USD 225 million Series A led by RA Capital Management, joined by Canaan Partners, Forbion and other investors.
| Round | Year | Amount | Source |
|---|---|---|---|
| Series A · Led by RA Capital Management, with Canaan Partners and Forbion. | 2026 | $225M | solsticeoncology.com |
Amounts only where the cited source states them. Rounds without a public source are not listed.
Shares Forbion, RA Capital Management.
Shares CTLA-4, PD-1, Monoclonal antibodies, Immune checkpoint inhibitors.
Shares CTLA-4, PD-1, Immune checkpoint inhibitors.
Shares CTLA-4, PD-1, Immune checkpoint inhibitors.
Shares CTLA-4, PD-1, Immune checkpoint inhibitors.
Shares CTLA-4, PD-1, Immune checkpoint inhibitors.
Shares RA Capital Management, PD-1, Immune checkpoint inhibitors.
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