Recently, Hengrui Pharmaceuticals and its subsidiary Shanghai Hengrui Pharmaceuticals Co., Ltd. received a Notice of Approval of Drug Clinical Trial from the State Drug Administration, approving the company to conduct an open, multi-center Phase I clinical study on the safety, tolerability and pharmacokinetics of HRS8807 combined with dalsylate hydroxyethanesulfonate in ER-positive, HER2-negative metastatic or locally advanced breast cancer patients.

Breast cancer is the most common malignant tumor worldwide. According to the Global Cancer Epidemiology Report 2024, breast cancer ranks first among female malignant tumors in terms of incidence and mortality, with approximately 2.31 million new cases of breast cancer and 670,000 deaths per year globally, ranking first in terms of incidence and mortality of female malignant tumors. Among all breast cancer patients, about 70% are ER-positive, and the guideline-recommended standard treatment is endocrine drugs combined with CDK4/6 inhibitors. In contrast, the new generation of oral selective estrogen receptor down-regulators (SERDs) as well as selective estrogen receptor covalent antagonists (SERCAs) have higher bioavailability and better pharmacokinetic profiles, which can inhibit and degrade ER faster and more effectively, and can address drug resistance arising from estrogen receptor mutations. Therefore, on this basis, novel endocrine combination CDK4/6 inhibitor therapy may hold promise as a new option for the treatment of ER-positive, HER2-negative breast cancer patients.

Dalsylate hydroxyethanesulfonate (trade name: Eriocan), a Class 1 new drug independently developed by Hengrui Pharmaceuticals and the first independently developed novel and highly selective CDK4/6 inhibitor in China, was approved by the State Pharmaceutical Administration for marketing in December 2021, with the approved indication of combining with fulvestrant for use in hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2-negative) recurrent or metastatic breast cancer patients who have been endocrinized for treatment after The approved indication is for the treatment of recurrent or metastatic breast cancer that has progressed after endocrine therapy in combination with an aromatase inhibitor as initial therapy for patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer. in June 2023, the indication was for the combination of an aromatase inhibitor as initial therapy.

HRS8807 is a novel, highly effective, small molecule selective estrogen receptor covalent antagonist (SERCA) independently developed by Hengrui Pharmaceuticals. It potently and highly selectively binds ER, inhibits ER activity and downstream signaling, and then inhibits tumor cell proliferation. There are currently no similar varieties on the market. In addition to the current approval, studies of HRS8807 as a single agent in breast cancer are underway.

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