TQB-3912

Primary objective Phase Ib of cohort 2: To evaluate the maximum tolerated dose and phase II recommended dose (RP2D) of TQB3912 tablets combined with fulvestrant injection and TQB3616 capsules in the treatment of subjects with locally advanced or metastatic HR-positive, HER2-negative breast cancer. Phase II of cohort 1 and cohort 2: This study aims to prove that TQB3912 tablets combined with fulvestrant injection ± TQB3616 capsules can improve the objective response rate (ORR) of subjects with locally advanced or metastatic HR-positive, HER2-negative breast cancer. Secondary objective To prove the effectiveness of TQB3912 tablets combined with fulvestrant injection ± TQB3616 capsules in subjects with locally advanced or metastatic HR-positive, HER2-negative breast cancer by evaluating PFS, DOR, DCR, CBR, OS, etc. Safety of TQB3912 tablets combined with fulvestrant injection ± TQB3616 capsules in subjects with locally advanced or metastatic HR-positive, HER2-negative breast cancer Pharmacokinetic (PK) characteristics of TQB3912 tablets combined with fulvestrant injection ± TQB3616 capsules in subjects with locally advanced or metastatic HR-positive, HER2-negative breast cancer.