Xuanzhu Biopharmaceuticals' self-developed Class 1 innovative drug pirroticlib tablets (brand name: Xuanyuening®) has recently received approval from the National Medical Products Administration (NMPA) for an additional indication: combination with aromatase inhibitors (AI) for initial endocrine therapy in patients with HR+/HER2-negative advanced breast cancer. This marks the third approved indication for pirroticlib, following its previous approvals for combination with fulvestrant and as monotherapy. Pirroticlib has thus become the first and only similar drug in China to cover the entire treatment course—including first-line, second-line, and subsequent lines—for HR+/HER2-negative advanced breast cancer.
 
01 Clinical Needs and Market Potential
 
Breast cancer is the most prevalent malignant tumor among women worldwide, with 2.3 million new cases reported globally in 2022 and an estimated rise to 3.2 million cases by 2050, of which approximately 70% are HR+/HER2-subtypes, indicating a significant demand for treatment. In China, there were 357,200 new cases of breast cancer in 2022, with a five-year relative survival rate of less than 30% for advanced-stage patients. The global market size for CDK4/6 inhibitors reached nearly $13 billion in 2024, representing a year-on-year increase of approximately 18%, offering new therapeutic hope for HR+/HER2-advanced breast cancer patients.
 
02 The Innovative Mechanism of Pirrolucel
 
Pilosidib is a novel CDK2/4/6 inhibitor independently developed by Xuanzhu Biotech, exhibiting a multi-target synergistic mechanism of action targeting CDK2, CDK4, CDK6, and CDK9. This drug effectively inhibits tumor cell proliferation, significantly reduces hematological toxicities commonly associated with conventional CDK4/6 inhibitors (such as grade 3/4 neutropenia), and enhances patient treatment tolerance. Additionally, its synergistic inhibition of CDK2 and CDK9 enhances antitumor efficacy and delays the development of drug resistance.
 
03 Evidence for Efficacy of Combination Therapy versus Monotherapy
 
The approval of this new indication was based on the interim analysis results from the BRIGHT-3 study. Data from a median follow-up period of approximately 20 months demonstrated that the median progression-free survival (PFS) in the pirrolimus plus AI group had not yet been reached, with a two-year PFS rate exceeding 60%, compared to a median PFS of 18.4 months in the control group. The investigator-assessed objective response rate (ORR) reached as high as 63.5%, rising to 67.6% among patients with measurable lesions, highlighting its superior efficacy compared to similar agents currently available.
The Bright-2 study demonstrated that the combination of pirrotosil and fulvestrant achieved a median progression-free survival (PFS) of 17.5 months, which was considered the best-in-class result in non-head-to-head comparisons. The Bright-1 study showed that pirrotosil monotherapy in highly refractory advanced-stage patients yielded a median PFS of up to 11 months and a median overall survival (OS) of up to 29 months, representing the best-in-class global data.
 
04 Looking to the Future
 
With the approval of new indications, pirrolimus has completed its comprehensive treatment portfolio for first-line, second-line, and subsequent-line therapies in HR+/HER2-negative advanced breast cancer, providing domestic patients with more precise treatment options. Its outstanding efficacy and favorable safety profile are expected to reshape the landscape of breast cancer treatment in China; its differentiated safety profile also offers a superior choice for patients at high risk of myelosuppression, providing crucial evidence-based support for clinical personalized medicine.
The approval of this new indication marks a significant breakthrough for China's independently developed innovative drugs in the field of breast cancer treatment. Piraroxil will provide patients with HR+/HER2-negative advanced breast cancer with a more comprehensive and precise treatment option thanks to its excellent efficacy and safety profile.
 
Regarding pirrolizidine
Piloside tablets (brand name: Xuanyuening®), as the first approved CDK2/4/6 inhibitor in China, boasts a unique multi-target synergistic mechanism of action, offering significant advantages such as potent inhibition of tumor cell proliferation and markedly reduced hematological toxicity commonly associated with conventional CDK4/6 inhibitors. In May 2025, piloside was approved by the China National Medical Products Administration for use in combination with fulvestrant in patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer who had experienced disease progression after prior endocrine therapy; or as monotherapy in patients with HR+/HER2-advanced or metastatic breast cancer who had progressed after receiving two or more prior endocrine therapies plus one chemotherapy regimen at the metastatic stage, making it the first and only CDK2/4/6 inhibitor approved for monotherapy indication in China. According to PharmaMagic data, piloside also ranks first globally in the CDK2/4/6 inhibitor category. In December 2025, both approved indications for piloside tablets were included in the National Essential Medicines List for Basic Medical Insurance, Maternity Insurance, and Work Injury Insurance (2025), effective January 1, 2026.