Six years ago, Brandon Turunen, PhD, answered a call from his employer, GSK, for proposals to develop new medicines.
“They would oftentimes do calls for new ideas amongst the company to look for new innovative ways that are transformational, but hard to do, and invest in those, and this was one of those,” Turunen told GEN. “I proposed using small molecules first to unlock undruggable targets but then use them to recruit a patient’s immune system to treat their disease. It’s antibody pharmacology.”
The idea behind Turunen’s proposal was to design a platform to unlock antibody-intractable cell surface targets and build next-generation that harness the power of biologics with the vast target binding space of small molecules. Turunen was able to lead a program team from concept to development to clinical molecules at GSK and build this platform—until there was a major shakeup in GSK’s investment priorities and strategy. GSK told Turunen it would be a great idea for the company to partner externally and find a home for the technology to get the best medicines for the patients that need them.
This week, Turunen introduced Solu Therapeutics, a Boston-based business founded by the Longwood Fund, announcing the successful completion of a $31-million seed financing. Solu Therapeutics will use the funding to leverage and develop the unique CyTaC (Cytotoxicity Targeting Chimera) platform and drug candidates. In addition to being the company co-founder, Turunen is also the chief technology officer at Solu, which is Finnish for “cell”—a nod to Turunen’s roots.
“The big idea here is to eliminate harmful cells from the body with a precision-based approach,” David Donabedian, PhD, co-founder, start-up CEO, and executive partner at the Longwood Fund, told GEN. “We’re focusing on high-value targets in oncology, immunology, and inflammation that pharma has not been able to drug with antibodies.”
Longwood and Santé Ventures jointly led the financing, with participation from DCVC Bio, Astellas Venture Management, and Alexandria Venture Investments. As part of the financing, Christoph Westphal, MD, PhD, founding executive chairman, Solu Therapeutics, and founding partner, Longwood Fund; Omar Khalil, partner, Health Ventures; John Hamer, PhD, managing director, DCVC Bio; Satoshi Konagai, Astellas Venture Management; and Peter Hutt have joined Solu’s board of directors.
The CyTaC platform and drug candidates were in-licensed from GSK by Solu. In return for the license, GSK received equity in Solu and will receive milestones and royalties on products derived from the platform.
The One-Two Punch
According to Turunen, antibodies have been successful in helping patients deplete tumor cells and pathogenic immune cells or bringing the body’s immune function to those sites of action. However, the problem is that effective biologics cannot engage many of those targets.
So, Turunen built a platform based on an antibody that effectively engages the immune system and can be generated quickly and at a large scale. What’s unique about this antibody is that it doesn’t bind to a cell-surface protein. It doesn’t recognize human proteins. Instead, it recognizes Solu’s small-molecule component—CyTaC, a hetero-bivalent small molecule. The two-sided molecule binds Solu’s “antibody” on one side, a target receptor on the other. Turunen says this accesses deep binding sites that are unreachable with a biologic.
Donabedian said the prime targets include G-protein-coupled receptors (GPCR), ion channels, and enzymes. The elegance of the platform is that it depends on doing small-molecule screening to identify candidates for these undruggable targets.
“CyTaC allows us now to take advantage of the small molecule binding and specificity and leverage the pharmacology of an antibody—it’s a one-two punch,” said Donabedian.
More money, more modules
Donabedian said that during the financing process, there was a lot of inbound interest, which has led to active partnering discussions. “I think of this as a robust chemistry platform with some strong biology,” he said.
When I ask about swapping out the immune-recruiting biologic for one that engages some other biology, Donabedian steps in. “Brandon has articulated one form of engaging the system,” he said. “There are other ways to do that, and we are already working on that. However, we can’t get into details at this point.”
We will have to wait and see what other signaling systems the team at Solu will choose to trigger. For now, at the top of Solu’s list of priorities is to get into the clinic. And that’s exactly how they plan to use this funding round—to advance their lead program, which Donabedian predicts is about two years away from the clinic.