Ensem Therapeutics Expands ETX-636 Trial to China, Targeting PI3Kα Mutations in Cancer
核心洞察
Ensem Therapeutics (搜索) has dosed the first patient with ETX-636 in China at Fudan University Shanghai Cancer Center as part of its global Phase 1/2 clinical trial.
ETX-636 is a potential first-in-class allosteric pan-mutant-selective PI3Kα (搜索) dual inhibitor and degrader targeting tumors with PI3Kα mutations, including breast cancer (搜索).
The drug employs a novel mechanism to selectively inhibit mutant PI3Kα (搜索) while sparing wild-type PI3Kα, potentially offering superior tolerability compared to first-generation inhibitors.
Ensem Therapeutics (搜索) has achieved a significant milestone in its global development strategy by dosing the first patient with ETX-636 in China at Fudan University Shanghai Cancer Center. The expansion of the global Phase 1/2 clinical trial into China follows the November 19th approval of the Investigational New Drug (IND) application by China's National Medical Products Administration (NMPA).
ETX-636 represents a potential breakthrough in precision oncology as a first-in-class and best-in-class allosteric pan-mutant-selective PI3Kα (搜索) dual inhibitor and degrader. The drug is being evaluated in patients with advanced solid tumors (搜索) harboring PI3Kα mutations, with particular focus on breast cancer (搜索) applications.
Novel Mechanism Addresses Current Treatment Limitations
According to Dr. Hongxia Wang, Principal Investigator in China at Fudan University Shanghai Cancer Center, mutant PI3Kα (搜索) serves as "a frequent and critical 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.
ETX-636 was rationally designed to optimally bind a specific allosteric pocket in p110α (搜索), the catalytic subunit of PI3Kα (搜索). This allosteric binding enables selective inhibition of all activating mutant forms of PI3Kα, including hotspot kinase- and helical-domain mutations, while sparing wild-type PI3Kα. The high selectivity is expected to reduce the risk of hyperglycemia and other wild-type PI3Kα-related adverse events compared with non-mutant-selective PI3Kα inhibitors.
Dual Mechanism of Action Shows Promise
Beyond potent catalytic inhibition, ETX-636 uniquely induces proteasome-dependent degradation of mutant PI3Kα (搜索) while preserving wild-type protein—a feature not observed with other allosteric PI3Kα inhibitors. This dual mechanism of action drives deep and durable pathway suppression and has demonstrated robust tumor regression in kinase- and helical-domain PI3Kα-mutant breast cancer (搜索) xenograft models, both as monotherapy and in combination with fulvestrant, with or without a CDK4/6 inhibitor.
In preclinical toxicology studies, ETX-636 did not disrupt glucose homeostasis at predicted human efficacious doses, supporting its potential for improved tolerability.
Global Trial Progress and Future Milestones
The ongoing first-in-human, global Phase 1/2 study (NCT06993844) is evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of ETX-636 in patients with advanced solid tumors (搜索) harboring PI3Kα (搜索) mutations. Since the first patient was dosed in the United States in June 2025, multiple leading U.S. cancer centers have joined the study.
ETX-636 is being evaluated both as monotherapy and in combination with fulvestrant, an approved selective estrogen receptor degrader, for the treatment of advanced HR+/HER2- breast cancer (搜索). Dose escalation in the United States is progressing as planned, and ETX-636 has been well tolerated to date, with no observed hyperglycemia or dose-limiting toxicities.
"The expansion of the ETX-636 clinical trial into China represents a significant milestone that strengthens our global clinical presence," said Dr. Shengfang Jin, Co-Founder and Chief Executive Officer of ENSEM. "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."
The company expects to disclose preliminary clinical data supporting proof of concept in the second half of 2026, marking a critical inflection point for the program's development trajectory.