Table 1.

Completed phase II–III clinical trials investigating CDK4/6 inhibitors in hormone receptor-positive metastatic breast cancer (mBC)

Trial	Study design	Randomized	Phase	Sample size	Population	Experimental arm	Control arm	PFS (months)	OS (months)
Paloma-1	Open label	Yes 1:1	2	165	AI sensitive Treatment naive for mBC Postmenopausal	Palbociclib plus Letrozole	Letrozole	20.2 vs 10.2 HR 0.48	37.5 vs 34.5 HR 0.89 (NS)
Paloma-2	Placebo control	Yes 2:1	3	666	AI sensitive Treatment naive for mBC Postmenopausal	Palbociclib plus Letrozole	Letrozole plus placebo	24.8 vs 14.5 HR 0.58	NA
Paloma-3	Placebo control	Yes 2:1	3	521	Endocrine resistant Pre/peri and postmenopausal	Palbociclib plus Fulvestrant	Fulvestrant plus placebo	9.5 vs 4.6 HR 0.46	34.9 vs 28.0 HR 0.81
Monarch-1	Open label	No	2	184	AI resistant CT treated mBC Postmenopausal	Abemaciclib	///	6.0	22.3
Monarch-2	Placebo control	Yes 2:1	3	669	AI resistant CT naive for mBC Pre/peri and Postmenopausal	Abemaciclib plus Fulvestrant	Fulvestrant plus placebo	16.4 vs 9.3 HR 0.55	NA
Monarch-3	Placebo control	Yes 2:1	3	493	Endocrine sensitive Postmenopausal	Abemaciclib plus Anastrozole/Letrozole	Anastrozole/Letrozole plus placebo	28.1 vs 14.7 HR 0.54	NA
Monaleesa-2	Placebo control	Yes 1:1	3	668	Endocrine sensitive Treatment naive for mBC Postmenopausal	Ribociclib plus Letrozole	Letrozole plus placebo	25.3 vs 16.0 HR 0.56	NA
Monaleesa-3	Placebo control	Yes 2:1	3	725	Endocrine sensitive and endocrine resistant mBC Postmenopausal	Ribociclib plus Fulvestrant	Fulvestrant plus placebo	20.5 vs 12.8 HR 0.59	NA
Monaleesa-7	Placebo control	Yes 2:1	3	672	Endocrine sensitive Pre/perimenopausal	Ribociclib plus Anastrozole/Letrozole plus LH–RH analog	Anastrozole/Letrozole plus LH–RH analog plus placebo	23.8 vs 13.0 HR 0.55	NR vs 40.9 HR 0.71

HR hazard ratio, LH–RH luteinizing hormone-releasing hormone, NA not available, NR not reached, NS not significant, OS overall survival, PFS progression-free survival