WALTHAM, Mass.– Ensem Therapeutics said it has dosed the first patient in China with ETX-636 as part of its ongoing global Phase 1/2 clinical trial, marking an expansion of the study aimed at accelerating enrollment and broadening patient access.
The first patient in China was treated at Fudan University Shanghai Cancer Center. ETX-636 is being evaluated in patients with tumors harboring activating PI3Kα mutations, including breast cancer. The expansion follows approval of the investigational new drug application by China’s National Medical Products Administration on Nov. 19.
ETX-636 is a potential first-in-class, allosteric pan-mutant-selective PI3Kα dual inhibitor and degrader designed to selectively target mutant PI3Kα while sparing the wild-type form of the protein.
“Ensem is committed to advancing innovative precision oncology medicines for patients worldwide,” said Shengfang Jin, Ph.D., co-founder and chief executive officer of Ensem Therapeutics. “The expansion of the ETX-636 clinical trial into China represents a significant milestone that strengthens our global clinical presence. We are pleased that several leading oncology centers in China are joining the study, which has the potential to accelerate enrollment, expand access to a broader and underserved patient population, and further strengthen the global clinical data package supporting ETX-636.”
Hongxia Wang, M.D., principal investigator in China at Fudan University Shanghai Cancer Center, said mutant PI3Kα is a frequent oncogenic driver across many cancers, including nearly half of hormone receptor-positive, HER2-negative advanced breast cancers.
“While first-generation PI3Kα inhibitors have clinically validated the target, their limitations, particularly toxicities associated with wild-type PI3Kα inhibition, underscore the need for improved therapies,” Wang said. “ETX-636 employs a novel allosteric mechanism of action to selectively inhibit and degrade mutant PI3Kα while sparing wild-type PI3Kα, potentially offering superior tolerability with robust anti-tumor activity. We are excited to collaborate with Ensem to evaluate ETX-636’s clinical potential and bring new treatment options to patients in China.”
The first-in-human, global Phase 1/2 study is evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of ETX-636 in patients with advanced solid tumors harboring PI3Kα mutations. The trial includes both monotherapy and combination treatment with fulvestrant for patients with advanced hormone receptor-positive, HER2-negative breast cancer.
The first patient in the United States was dosed in June 2025, and multiple U.S. cancer centers are participating in the study. Dose escalation in the U.S. is progressing as planned, and the company said ETX-636 has been well tolerated to date, with no observed hyperglycemia or dose-limiting toxicities.
Ensem expects to disclose preliminary clinical data supporting proof of concept in the second half of 2026.
