Among the 28 measurable patients, 16 patients had a PR, the ORR was 57.1% (95% CI 37.2–75.5); the CBR was 82.1% (95% CI 63.1–93.9) (Table)....At 6 and 12 months, PFS rates were 92.3% and 83.5%, and DOR rates were 100% and 90%, respectively....FCN-437c plus letrozole was well tolerated and demonstrated antitumor activity in patients with previously untreated HR+/HER2– ABC.