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Table 1 Reported clinical trials with targeted CDK4/6 inhibitors in breast cancer

From: Recent advances of highly selective CDK4/6 inhibitors in breast cancer

Breast tumor type

Phase

Dosage

Response rate

NCT

Ref

Palbociclib

RB+ ABC

N = 5

I

Administrated in six dose escalation cohorts (standard 3 + 3 design) MTD and RP2D: 125 mg

SD: 20% (1/5)

NCT

00141297

[84]

ER+/HER2- ABC

N = 9

I

MTD: 125 mg; Palbociclib (125 mg QD, 3 weeks on/1 week off) plus letrozole (2.5 mg, continuous)

PR: 33% (2/6)

SD: 33% (2/6)

NCT

01684215

[83]

ER+/HER2-ABC

N = 165

II

Palbociclib (125 mg QD, 3 weeks on/1 week off) plus letrozole (2.5 mg, continuous)

PFS: 20.2 months for the palbociclib plus letrozole group and 10.2 months for the letrozole group (HR 0.488, 95%CI 0.319-0.748; one-sided

p = 0.0004)

NCT

00721409

[88]

RB+ MBC

N = 37

II

Palbociclib (125 mg QD, 3 weeks on/1 week off)

PR: 7% (2/28)

SD: 50% (14/28)

PFS: 3.8 months

(1.9–5.8) for HR+/HER2- patients, 5.1 months (5.1–∞)for HR+/HER2+ patients, 1.5 months (0.62-∞) for HR-/HER2- patients, 4.5 months for HR+ patients, and 1.5 months for HR- patients

NCT

01037790

[87]

HR+/HER2-ABC

N = 521

III

Palbociclib (125 mg QD, 3 weeks on/1 week off) plus fulvestrant (500 mg IM every 2 weeks

For the first three injections and then every 4 weeks), or matching placebo plus fulvestrant

PFS: 9.2 months

(95%CI, 7.5 to ∞) for palbociclib plus fulvestrant group and 3.8 months (95%CI, 3.5 to 5.5) for placebo plus fulvestrant group (HR: 0.42; 95%CI,0.32 to 0.56; P < 0.001)

NCT

01942135

[90]

ER+/HER2-ABC

N = 666

III

Palbociclib (125 mg QD, 3 weeks on/1 week off) plus letrozole (2.5 mg, continuous)

PFS: 24.8 months for the palbociclib plus letrozole group and 14.5 months for the letrozole group (HR 0.488, 95%CI 0.319-0.748; one-sided p = 0.0004)

NCT

01740427

[89]

Ribociclib

RB+ ABC

N = 20

I

MTD: 900 mg QD for 3 weeks on/1 week off RDE: 600 mg QD For 3 weeks on/1 week off; Ribociclib: 600 mg QD 3 weeks on/1 week off or continuous

PR: 1 (1/20)

(600 mg/day continuous)

NCT

01237236

[85]

HR+/HER2-

RBC or MBC

N = 668

III

Ribociclib (600 mg QD 3 weeks on/1 week off) plus letrozole (2.5 mg QD) or matching placeboplus letrozole.

PFS: ribociclib

group versus placebo group (0.56;95%CI, 0.43to 0.72, p < 0.001); ribociclib group versus placebo group (63.0% (95%CI, 54.6 to 70.3) and 42.2% (95%CI,34.8 to 49.5) after 18 months, OR: ribociclib Group versus placebo group (52.7% and 37.1%)

NCT

01958021

[91]

Abemaciclib

BC

N = 66

I

Abemaciclib (200 mg Q12H continuous for 4 weeks)

PR: 31% in HR+ patients and none in HR- patients SD: 50% in HR+ patients and 33% in HR- patients

NCT

01394016

[75]

ER-/PR-/HER2 + BC

N = 1

I

Abemaciclib (200 mg Q12H continuous for 4 weeks)

Tumor size decreases more than 30% from baseline

NCT

02014129

[93]

  1. Abbreviations: ABC Advanced breast cancer, CI confidence interval, ER+ Estrogen receptor-positive, HER2- Human epidermal growth factor receptor 2-negative, HR Hazard ratio, HR Hormone receptor, IM intramuscular injection, MBC Metastatic breast cancer, MTD Maximum tolerated dose, N Number of enrolled breast cancer patients, NCT National clinical trial, OR overall response, PFS Progression-free survival, PR Partial response, QD Once daily, Q12H Twice daily, RB+ Retinoblastoma-positive, RBC Recurrent breast cancer, RP2D Recommended dose for phase II studies, SD Stable disease