On December 22, 2025 Alphamab Oncology (stock code: 9966.HK) reported that that the clinical trial application for the independently developed TROP2/HER3 bispecific antibody-drug conjugate (ADC) JSKN016, in combination with InventisBio’s oral selective estrogen receptor degrader (SERD) D-0502, has been approved by the Center for Drug Evaluation (CDE) of the National Medical Products Administration (NMPA). The trial (Study Number: JSKN016-204) is for the treatment of locally advanced or metastatic HR-positive, HER2-negative (HR+/HER2-) breast cancer.

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Breast cancer is the most prevalent malignancy among Chinese women, with the HR+/HER2- subtype accounting for approximately 70% of all breast cancer cases. The current first-line standard of care involves endocrine therapy combined with CDK4/6 inhibitors. However, primary or acquired resistance often leads to disease progression, resulting in a significant unmet clinical need in later-line treatment. Therefore, it is crucial to explore novel-mechanism drugs and combination therapies.

JSKN016 is a novel bispecific ADC that simultaneously targets TROP2 and HER3 on the surface of tumor cells. It blocks the corresponding signaling pathways while enhancing cellular endocytosis and release of topoisomerase I inhibitors, enabling precise tumor killing. Early phase clinical studies have shown promising antitumor activity and a favorable safety profile in various solid tumors, including breast cancer. D-0502 is a novel, oral SERD independently developed by InventisBio. Early phase clinical studies have demonstrated its antitumor activity and good tolerability as monotherapy. The combination of both drugs is expected to achieve multiple synergistic effects, which may lead to prolonged disease control and improved survival outcomes for patients.

JSKN016-204 is a multicenter, open-label, randomized controlled phase Ib/II clinical study. It aims to evaluate the safety, tolerability, dose-limiting toxicity (DLT), preliminary antitumor activity, and pharmacokinetics (PK)/pharmacodynamics (PD) of JSKN016 in combination with D-0502 in patients with locally advanced or metastatic HR+/HER2- breast cancer who have been previously treated with CDK4/6 inhibitor in combination with endocrine therapy.

Ms. Yang Liu, Chief Operating Officer of Alphamab Oncology, stated: "Oral SERDs, including InventisBio’s D-0502, have recently demonstrated superior efficacy in HR+ breast cancer. Currently, there are no global precedents for combining an ADC with an oral SERD. Our JSKN016 has shown excellent efficacy and safety in later-line HR+ breast cancer. By combining with D-0502, we hope to further extend the progression-free survival for HR+ breast cancer patients after front-line therapy resistance and translate it into high-quality, long-term survival benefits. We greatly look forward to this collaboration."

Dr. Ling Zhang, Chief Medical Officer of InventisBio, stated: "We are very pleased that the clinical trial application for the combination therapy of D-0502 and JSKN016 has been approved. Drug resistance in HR+/HER2- breast cancer remains a major clinical challenge, with limited treatment options in later lines. D-0502, an oral SERD with a favorable safety profile and high bioavailability, in combination with the ADC JSKN016, is expected to synergistically inhibit tumor growth through a dual mechanism of action, offering new hope for patients with refractory disease."

About JSKN016

JSKN016 is a TROP2/HER3 targeting bispecific ADC developed using the proprietary single-domain antibody and bispecific antibody platforms. It is conjugated via site-specific glycosylation to generate a homogeneous and stable ADC with a drug-to-antibody ratio (DAR) of 4. Upon binding to TROP2 and/or HER3 on the tumor cell surface, JSKN016 blocks the corresponding signaling pathways and enhances cellular endocytosis to release topoisomerase I inhibitors, thereby exerting anti-tumor effects.

JSKN016 has demonstrated promising antitumor activity and a favorable safety profile across multiple solid tumors. Dose optimization and dose confirmation have been completed, and it is poised to advance into Phase III clinical studies.

About D-0502 (Taragarestrant)

D-0502 is a novel, oral selective estrogen receptor degrader (SERD) independently developed by InventisBio, intended for the treatment of estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Compared to existing injectable SERDs, its oral administration offers greater convenience for patients. D-0502 has demonstrated favorable antitumor activity and a promising safety profile in both preclinical studies and clinical trials. In October 2021, the Center for Drug Evaluation (CDE) granted approval to initiate a registrational Phase III clinical trial in China for D-0502. This trial is designed as a head-to-head comparison against standard of care in patients with ER-positive, HER2-negative locally advanced or metastatic breast cancer. The first patient was successfully enrolled in this registrational Phase III trial in September 2022, and the trial is currently proceeding as planned.

(Press release, Alphamab, DEC 22, 2025, View Source [SID1234662085]).