Table 3.

Trials testing CDK4/6 inhibitors.

Trial	Phase	Treatment	n	Primary Endpoint	Results	Target
PATRICIA	II	Palbociclib 200 mg 2 w on 1 w off or 125 3 w on 1 w off + H 600 mg sc every 3 w ER+ patients were treated with Letrozole vs. Placebo	71 (56 ER+)	PFS at 6 m	6 m PFS in ER+ patients treated with Palbociclib + H 42.8% vs. 46.4% Luminal disease by PAM50 had longer PFS (10.6 m vs. 4.2 m)	Similar potency against CDK 4 than CDK 6
Ribociclib, NCT02657343	Ib/II	Ribociclib 400 mg daily (phase II) + H iv	13 (ER + in 8)	MTD and CBR	1 experienced stable disease >24 w PFS was 1.3 m	Greater potency against CDK 4 than CDK 6
Ribociclib, NCT02657343	Ib	Ribociclib 400 mg given on days 8–21 of a 21-day cycle with T-DM1	12	MTD for phase II	PFS was 10.4 m	Greater potency against CDK 4 than CDK 6
MonarchHER	II	A: Abemaciclib 150 mg/12 h + H iv B: Abemaciclib + BPC ChT C: Abemaciclib + fulvestrant im + H iv	237 physician’s choice (all HER+/ER+)	PFS between groups	Abemaciclib + H + Fulvestrant longer PFS: 8.3 m vs. 5.7 m and 5.7 m compared with the other groups	Greater potency against CDK 4 than CDK 6, also CDK 1/2/5 inhibitor
PATINA	III	H + P with endocrine therapy (letrozole, anastrozole, exemestane or fulvestrant) +/- palbociclib	496 already recruited	PFS	Not reported yet	Similar potency against CDK 4 than CDK 6
ASPIRE	I/II	Palbociclib (100 and 125 mg 3 w on 1 w off) + H iv + P iv + Anastrozole	36 planned	DLT, MTD, CBR	Not reported yet	Similar potency against CDK 4 than CDK 6

MTD: Maximum Tolerated Dose; PFS: Progression-Free survival; CBR: Clinical Benefit Rate; BPC: best physician’s choice; ROR: rate of overall response; DLT: dose limiting toxicity; iv: intravenous; im: intramuscular; sc: subcutaneous, H: trastuzumab; P: pertuzumab; ChT: chemotherapy; m: months; w: weeks.