Konruns Pharmaceutical Enrolls First Subject in Phase II Study of KC1086 Combined with Fulvestrant for Breast Cancer

Beijing Konruns Pharmaceutical Co., Ltd. (603590.SH) announced on November 11 that the first subject has been enrolled and dosed in its Phase II clinical study (KC1086-COM-01) evaluating KC1086 tablets in combination with fulvestrant for the treatment of HR+/HER2- locally advanced or metastatic breast cancer.

The milestone marks a key step forward for the internally developed KC1086, a potent small-molecule inhibitor that simultaneously targets KAT6 and KAT7 — two enzymes implicated in tumor cell proliferation and survival. The Phase II trial is designed to assess the efficacy and safety of the combination regimen in patients whose cancers harbor hormone-receptor-positive and HER2-negative status, a subtype that accounts for a significant share of advanced breast cancer cases globally.

KC1086's clinical development has advanced rapidly. The company initiated a Phase I clinical trial in August 2025 and subsequently received clearance from the U.S. Food and Drug Administration to proceed with investigational studies under an Investigational New Drug application. The regulatory green light from the FDA underscores the agency's recognition of the compound's potential and the rigor of the preclinical data supporting its clinical evaluation.

Konruns Pharmaceutical said KC1086 is the world's first KAT6/7 dual-target small-molecule inhibitor to enter clinical development, a distinction that positions the company at the forefront of a relatively unexplored therapeutic avenue. The KAT6 and KAT7 histone acetyltransferases have drawn increasing attention from oncology researchers for their roles in gene regulation and cancer progression, yet no other small-molecule candidates targeting both enzymes have advanced into human trials.

The combination of KC1086 with fulvestrant — an established estrogen-receptor antagonist widely used in HR+ breast cancer — reflects a strategy of pairing a novel mechanism of action with a proven therapeutic backbone. Fulvestrant, marketed originally as Faslodex by AstraZeneca, is a standard treatment option for patients with hormone-receptor-positive advanced breast cancer, particularly in the second-line setting and beyond.

For Konruns, a Beijing-based pharmaceutical company listed on the Shanghai Stock Exchange, the enrollment of the first patient in the Phase II study signals a transition from early-stage safety assessment toward pivotal efficacy evaluation. Data from the KC1086-COM-01 trial could inform the design of larger, registrational studies and potentially support regulatory filings if results prove compelling. The company has not disclosed a timeline for readout of the Phase II data.

The breast cancer franchise is one of the most competitive arenas in oncology drug development, with multiple approved therapies and a deep pipeline of investigational agents. Yet the HR+/HER2- segment — which represents roughly 70% of all breast cancers — still faces significant unmet needs, particularly after patients progress on standard endocrine therapies. A novel agent like KC1086, if it demonstrates meaningful clinical benefit in combination with fulvestrant, could carve out a differentiated position in this crowded but still underserved market.

Konruns did not respond to requests for comment beyond the announcement. The company's shares trade on the Shanghai Stock Exchange main board under the ticker 603590.