A Phase I Study of LX-039 Tablets

This is a phase I dose escalation and expansion study in patients with ER+, HER2- advanced breast cancer to explore the tolerance, PK/PD(pharmacokinetics/pharmacodynamics) profiles and preliminary anti-tumor activity of different doses of LX-039 tablets. The trial consists of two parts, dose escalation and dose expansion. Part 1 is the dose escalation phase with initial 6 dose groups, and "3 + 3" design is used to explore MTD of the drug; Part 2 is the dose expansion phase with 2 \~ 3 doses selected for expansion according to the escalation results of Part 1, and more subjects are enrolled to further observe the tolerance and preliminary anti-tumor activity of the drug. After the completion of dose expansion, the recommended phase II dose (RP2D) will be determined after discussion based on the obtained tolerance and PK/PD data.