A Study of Lerociclib in Participants With Advanced Breast Cancer

Prior treatment

• Participant with central nervous system (CNS) involvement unless they are at least 4 weeks from prior therapy completion to starting the study treatment and have stable CNS tumor at the time of screening and not receiving steroids and/or enzyme inducing anti-epileptic medications for brain metastases.
• Has received prior treatment with chemotherapy (except for neoadjuvant/ adjuvant chemotherapy) or any CDK4/6 inhibitor.
• Has received prior treatment with fulvestrant.
• Participant is currently receiving any of the following substances and cannot be discontinued 14 days prior to start the treatment:
  • Known strong or moderate CYP3A inducers or strong inhibition of CYP3A
  • Substances that have a narrow therapeutic window and are predominantly metabolized through CYP3A4/5.

Other illness

• Symptomatic visceral disease or any disease burden that makes the participant ineligible for endocrine therapy per the Investigator's best judgment.
• Inflammatory breast cancer at screening.
• Clinically significant, uncontrolled heart disease and/or cardiac repolarization abnormality
• Evidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or oral temperature > 38°C at screening
• Interstitial pneumonia or severe impairment of lung function

Lab values

• Has a history of prolonged QT syndrome or Torsades de Pointes
• Echocardiogram done within the past 12 months with ejection fraction of ≤ 45% or documented history of congestive heart failure with reduced ejection fraction.

Other

• Peritoneal carcinomatosis.
• Use of systemic estrogens

• Participant must be 18 or the legal age of consent in the jurisdiction in which the study is taking place, at the time of signing the informed consent.
• Histologically and/or cytologically confirmed diagnosis of estrogen-receptor positive and/or progesterone receptor positive breast cancer by local laboratory and has HER2-negative breast cancer.
• Advanced (locoregionally recurrent not amenable to curative therapy, eg, surgery and/or radiotherapy, or metastatic) breast cancer
• Eastern Cooperative Oncology Group performance status (ECOG PS) 0 or 1.
• Adequate bone marrow and organ function
• Female that is not pregnant and agrees to contraceptive use that is consistent with local regulations regarding the methods of contraception to be used during the study
• Males agree to use a highly effective method of contraception and will refrain from donating sperm from the first dose of any study intervention
• Participant is capable of giving signed informed consent