Immuno-oncology startup raises $225 million to develop ‘next-generation drug’

Immuno-oncology startup Solstice Oncology has raised $225 million to develop next-generation cancer drugs.

Solstice Oncology said it had emerged from stealth and raised $225 million in a Series A round, BioPharma Dive reported on the 9th (local time). Investors included RA Capital Management, Canaan Partners and Forbion.

The company’s lead candidate is the CTLA-4 antibody forustobart. CEO Caroline Low said the company plans to begin a midstage clinical trial this year.

Forustobart was licensed from Chinese pharmaceutical company Harbour BioMed in February. The deal is valued at $1.2 billion, including an upfront payment of $105 million.

CTLA-4, along with PD-1, is a leading target for immuno-oncology drugs, but developing drugs against it is notoriously difficult. PD-1 inhibitors have become mainstream cancer treatments following the success of Keytruda and Opdivo.

By contrast, Bristol Myers Squibb’s Yervoy, the first commercial drug targeting CTLA-4, was approved to treat melanoma in 2011. However, it has been associated with serious immune-related adverse events and is considered less effective than PD-1 inhibitors.

Still, some pharmaceutical companies, including AstraZeneca, believe in the potential of next-generation CTLA-4 drugs and continue to develop them. Solstice Oncology has made the same bet.

The company is focusing on microsatellite-stable (MSS) colorectal cancer, which accounts for most colorectal cancer patients. MSS colorectal cancer is known as a “cold tumor,” and existing immuno-oncology drugs have had limited efficacy against it.

CEO Low said forustobart is being combined with existing PD-1 inhibitors. She said early clinical trials showed durable responses in patients who had received multiple prior treatments.

Forustobart is designed to increase depletion of regulatory T cells. Its half-life is also shorter, at 4-5 days compared with 15 days for first-generation CTLA-4 drugs, which could reduce the duration and severity of adverse effects.

“It’s like enhancing existing CTLA-4 drugs,” CEO Low said.

Josh Resnick, a partner at RA Capital, said, “The size of this financing and the caliber of the investor group reflect confidence in the science, strategy and execution.”