Scorpion Therapeutics has closed a $150 million series C to support development of its precision oncology pipeline, including lead compound STX-478—a highly specific PI3Kα inhibitor. The financing was co-led by Frazier Life Sciences and Lightspeed Venture Partners and included additional new support from Willett Advisors and leading healthcare institutional investors, along with existing investors.
In particular, Scorpion plans to use the funds to expand clinical development of its allosteric, differentiated, mutant-selective PI3Kα inhibitor, STX-478, which is first being tested in breast cancer and other solid tumors. Further, the Company will continue to advance its clinical-stage EGFR inhibitor franchise, including STX-721 and STX-241, and its discovery pipeline of next-generation precision oncology therapies.
“The robust demand for this capital raise is a testament to Scorpion’s continued clinical execution, the strength of our emerging clinical data, and the quality of our rapidly advancing pipeline,” said Adam Friedman, MD, PhD, CEO of Scorpion.
In connection with the financing, Shelley Chu, MD, PhD, partner at Lightspeed Venture Partners, will transition to an investor board member and Albert Cha, MD, PhD, Managing Partner at Frazier Life Sciences, will join Scorpion’s board as an observer.
“STX-478, has the potential to become a best-in-class treatment for patients with PI3Kα-mutated breast cancer and other solid tumors, and we look forward to partnering with management to further explore STX-478 in mid-stage clinical trials,” said Chu.
Scorpion points out that only a small number of cancer drivers have been successfully targeted and treated with precision therapies. Currently, about 14% of all patients with cancer are eligible for existing precision oncology therapies and only 7% realize clinical benefits.
PI3Kα is a critical lipid kinase and highly mutated protein in cancer, occurring in over 166,000 patients per year with breast, gynecological and other solid tumors in the United States alone. The first FDA approved PI3Ka inhibitor was Novartis’ alpelisib. It inhibits both the wild-type and mutant enzyme. Inhibiting the wild type enzyme causes side effects. So STX-478 was designed to be more specific.
In preclinical models, STX-478 has demonstrated robust activity across a range of PI3Kα mutations while sparing wild-type PI3Kα inhibition in normal tissues; previous generations of non-selective PI3Kα inhibitors have limited patient benefit due to these on-target toxicities.
Scorpion’s Phase I/II clinical trial is a multi-center, global, open-label study designed to evaluate the safety and tolerability of STX-478 in multiple ascending doses for patients with locally advanced or metastatic HR+/HER2- breast cancer and other solid tumors driven by PI3Kα mutations.
The program entered the clinic in 2023 and is now in multiple expansion cohorts across a range of solid tumors and in breast cancer as monotherapy and in combinations with fulvestrant and CDK4/6 inhibitors. Scorpion says it “Remains on-track to disclose initial safety, pharmacokinetic and pharmacodynamic data, and preliminary efficacy data at a future academic conference.”
Chu said, “The team has made remarkable progress since inception, and we believe Scorpion’s targeted approach may be able to overcome the selectivity challenges that plague existing treatment options, ultimately providing better outcomes to patients by offering improvements in both efficacy and safety. In particular, Scorpion’s mutant-selective PI3Kα inhibitor, STX-478.”
