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Eli Lilly to Acquire Scorpion Therapeutics' Mutant PI3Kα Inhibitor for $2.5B

NEW YORK – Eli Lilly on Monday said it will acquire Scorpion Therapeutics' mutant-PI3Kα inhibitor STX-478 for up to $2.5 billion while Scorpion spins out a new entity to develop its non-PI3Kα assets.

Under the terms of the agreement, Scorpion's shareholders will receive an upfront payment and subsequent regulatory and sales milestone payments.

Scorpion and Lilly have been among a cohort of companies developing next-generation PI3Kα inhibitors for hormone receptor-positive, HER2-negative breast cancer that zero in on the mutant form of the protein. Those companies hope to avoid adverse effects associated with this class of drugs, particularly hyperglycemia, which has hampered uptake of Novartis' PI3Kα inhibitor Piqray (alpelisib), the first approved drug in the class. Piqray inhibits both the wild-type and mutant forms of PI3Kα.

The US Food and Drug Administration approved Roche's Itovebi (inavolisib), the first of these new mutant-specific drugs, in October 2024. Meanwhile, Lilly discontinued its own mutant PI3Kα inhibitor program, LOXO-783, after the drug delivered disappointing results in a Phase Ia/b trial, which the company reported at the San Antonio Breast Cancer Symposium (SABCS) in December. Although LOXO-783 had a 52 percent disease control rate with minimal hyperglycemia when given to patients with advanced, PI3Kα-mutated, HR-positive, HER2-negative breast cancer in combination with physician's choice of anti-estrogen therapy, 85 percent of patients had diarrhea, limiting investigators' ability to reach the optimal dose.

However, results from a first-in-human Phase I/II trial of Scorpion's STX-478, also presented at SABCS, showed that patients with advanced PI3Kα-mutated, HR-positive, HER2-negative breast cancer on STX-478 and fulvestrant had a 68 percent disease control rate with a favorable safety profile, including low rates of hyperglycemia and no patients with grade 3 or higher hyperglycemia.

"The selectivity profile of STX-478 has led to a differentiated clinical profile, enabling use in combinations with standard-of-care therapies to potentially deliver meaningful impact in earlier treatment settings when there is the best opportunity to improve outcomes for patients," Jacob Van Naarden, executive VP and president of Lilly Oncology, said in a statement.

As part of the transaction, Lilly will hold a minority equity interest in the new company spun out of Scorpion, which current Scorpion shareholders will own. Scorpion CEO Adam Friedman will lead the new company, which will advance Scorpion's remaining pipeline of investigational drugs, including two EGFR inhibitor programs, STX-721 and STX-241, that it is codeveloping with Pierre Fabre. Scorpion is studying STX-721 in a Phase I/II trial in patients with advanced or metastatic non-small cell lung cancer whose tumors harbor EGFR exon 20 insertion mutations.