This is a Multicenter, Randomized, Double-blind, Placebo-controlled Phase III Clinical Study Evaluating the Efficacy and Safety of FCN-437c in Combination With Fluvestrant ± Goseraline Versus Placebo Combined With Fulvestrant ± Goserelin in Women With HR+ and HER2- Advanced Breast Cancer.

FCN-437c：available in 25mg and 100mg capsules for oral administration on an empty stomach. 200mg once daily on Day 1 to Day 21 of every 28-day cycle followed by 7 days off treatment until progressive disease。 Fulvestrant：500mg intramuscular injection on day 1 and day 15 for the first cycle and then on day 1 only for other cycles ； Goserelin acetate：premenopausal /perimenopausal patients should be coadministered with 3.6mg, Subcutaneously at every 28 days until progressive disease。

Placebo：available in 25mg and 100mg capsules, and is administered in the same way as FCN-437c。 Fulvestrant：500mg intramuscular injection on day 1 and day 15 for the first cycle and then on day 1 only for other cycles； Goserelin acetate：premenopausal /perimenopausal patients should be coadministered with 3.6mg, Subcutaneously at every 28 days until progressive disease。