A Phase II Clinical Study of the Efficacy and Safety of Culmerciclib Rechallenge in HR-positive, HER2-negative Breast Cancer Patients With Resistance to First-line Endocrine Therapy.
To evaluate the efficacy and safety of Culmerciclib combined with fulvestrant compared with investigator-selected CDK4/6 inhibitors combined with fulvestrant in patients with HR-positive/HER2-negative breast cancer who have progressed after first-line endocrine therapy