Study design and treatment
toxicity, death
DISEASE PROGRESSION
All patients received dalpiciclib 125 mg daily orally for 21 days followed by seven days off and pyrotinib 400 mg daily orally in each 28-day cycle. Treatment was continued until disease progression, unacceptable toxicity, death, consent withdrawal, or investigator decision. Concomitant endocrine therapy was not allowed. Participants with BM at baseline developing isolated intracranial progression could continue study treatment after brain radiotherapy till the second progression if they would benefit from the treatment according to the physicians’ discretion. Dose interruptions and reductions were allowed to manage AEs. Dose adjustments for dalpiciclib and pyrotinib were permitted as specified in the protocol. The trial protocol is available in the 