Table 1.

Pivotal studies on the three approved CDK4/6 inhibitors.

	Study	Description	Phase	Number of Patients Enrolled	Median PFS	Identifier NCT	Status	Treatment
1st line	PALOMA-1	Palbociclib + Letrozol vs. Placebo + Letrozole	II	177	18.1 m vs. 11.1 m	NCT00721409	Completed	Palbociclib 125 mg/d orally for 3 weeks, followed by 1 week off Letrozole 2.5 mg/d orally on a continuous regimen Placebo 125 mg/d orally for 3 weeks, followed by 1 week off
	PALOMA-2	Palbociclib + Letrozol vs. Placebo + Letrozole	III	666	24.8 m vs. 14.5 m	NCT01740427	Active, not recruiting	Palbociclib 125 mg/d orally for 3 weeks, followed by 1 week off Letrozole 2.5 mg/d orally on a continuous regimen Placebo 125 mg/d orally for 3 weeks, followed by 1 week off
	MONALEESA-2	Ribociclib + Letrozol vs. Placebo + Letrozole	III	668	25.3 m vs. 16.0 m	NCT01958021	Active, not recruiting	Ribociclib 200 mg × 3/d orally for 3 weeks, followed by 1 week off Letrozole 2.5 mg/d orally on a continuous regimen Placebo 200 mg × 3/d orally for 3 weeks, followed by 1 week off
	MONALEESA-7	Ribociclib + Goserelin + Tamoxifen/Letrozole/Anastrozole vs. Placebo +Goserelin +Tamoxifen/Letrozole/Anastrozole	III	672	23.8 m vs. 13.0 m	NCT02278120	Active, not recruiting	Ribociclib 200 mg × 3/d orally for 3 weeks, followed by 1 week off Goserelin 3.6 mg subcutaneous injection once every 28 days Letrozole 2.5 mg/d orally or Anastrozole 1 mg/d orally or Tamoxifen 20 mg/d orally on a continuous regimen Placebo 200 mg × 3/d orally for 3 weeks, followed by 1 week off
	MONARCH-3	Abemaciclib + Letrozole/Anastrozole vs. Placebo + Letrozole/Anastrozole	III	493	28.18 m vs. 14.76 m	NCT02246621	Active, not recruiting	Abemaciclib 150 mg × 2/d orally Letrozole 2.5 mg/d orally or Anastrozole 1 mg/d orally Placebo 150 mg × 2/d orally
2nd line	PALOMA-3	Palbociclib + Fulvestrant vs. Placebo + Fulvestrant	III	521	9.50 m vs. 4.60 m	NCT01942135	Completed	Palbociclib 125 mg/d orally for 3 weeks, followed by 1 week off Fulvestrant 500 mg intramuscular injection on day 1 and day 15 of cycle 1 and then on day 1 of each cycle Placebo 125 mg/d orally for 3 weeks, followed by 1 week off
	MONARCH-2	Abemaciclib + Fulvestrant vs. Placebo + Fulvestrant	III	669	16.40 m vs. 9.30 m	NCT02107703	Active, not recruiting	Abemaciclib 150 mg × 2/d orally Fulvestrant 500 mg intramuscular injection on day 1 and day 15 of cycle 1 and then on day 1 of each cycle Placebo 150 mg × 2/d orally
Later line	MONARCH-1	Abemaciclib alone (one arm clinical trial)	II	132	5.95 m	NCT02102490	Completed	Abemaciclib 200 mg × 2/d orally