Study Design
ER-positive
This multicenter nonrandomized open-label dose-escalation and -expansion phase Ia/Ib study (clinicaltrials.gov NCT03332797; GO39932) evaluated the safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of giredestrant alone and in combination with palbociclib in patients with ER-positive (ERIn the single-agent dose-escalation stage, giredestrant was administered orally once daily on days 1–28 of each 28-day cycle at 10, 30, 90, or 250 mg. A single dose was administered on cycle 1 day −7, followed by a 7-day pharmacokinetic lead-in for all single-agent giredestrant dose-escalation cohorts. In addition, a combination cohort in the dose-escalation stage explored giredestrant 100 mg once daily (days 1–28) in combination with palbociclib 125 mg once daily (days 1–21), repeated every 28 days. In the expansion stage, single-agent expansion cohorts evaluated giredestrant at doses of 30, 100, and 250 mg once daily. A combination expansion cohort evaluated giredestrant 100 mg with palbociclib 125 mg.