Dalpiciclib, a novel CDK4/6 inhibitor, as monotherapy has demonstrated tolerability and preliminary antitumor activity in pretreated HR+/HER2− advanced breast cancer ( ABC ).
Researchers have evaluated Dalpiciclib with Fulvestrant in advanced breast cancer.
In this randomized, double-blind, phase 3 trial, patients with HR+/HER2− locally advanced or metastatic breast cancer who had relapsed or progressed on previous endocrine therapy were enrolled.
Eligible patients were randomized 2:1 to receive Dalpiciclib ( Dalpiciclib; 150 mg po qd, d1-21, q4w ) or placebo with Fulvestrant ( Fulvestrant; 500 mg im, cycle 1 d1, d15, then d1 q4w ).
The primary endpoint was investigator-assessed progression-free survival ( PFS ).
As of November 15, 2020, 162 ( 71.4% of total projected ) events of disease progression or death had occurred and a preplanned interim analysis was done.
Overall, 361 patients were randomized to receive Dalpiciclib - Fulvestrant ( n = 241 ) or Placebo - Fulvestrant ( n = 120 ).
With a median follow-up of 10.5 months, Dalpiciclib - Fulvestrant has significantly improved investigator-assessed progression-free survival versus Placebo - Fulvestrant ( median, 15.7 [ 95% CI 11.1-NR ] vs 7.2 [ 95% CI 5.6-9.2 ] months; hazard ratio, HR, 0.42 [ 95% CI 0.31-0.58 ]; P less than 0.0001 ).
Progression-free survival per IRC were consistent with investigator assessment.
The benefit of Dalpiciclib extended beyond initial study treatment based on time to first subsequent chemotherapy ( TFSCT; HR, 0.47 [ 95% CI 0.32-0.69 ]; P less than 0.0001 ).
Overall survival ( OS ) data were not mature with a total of 25 deaths documented. Median duration of exposure was 9.4 ( IQR, 4.3-11.4 ) months with Dalpiciclib and 9.9 ( 4.7-11.9 ) months with Fulvestrant in the Dalpiciclib - Fulvestrant group and was 6.1 ( 3.7-11.0 ) months with Fulvestrant in the Placebo - Fulvestrant group.
The most common ( incidence 3% or more ) grade 3 or 4 adverse effects with Dalpiciclib - Fulvestrant were neutropenia ( 84.2%; vs 0% with Placebo - Fulvestrant ) and leukopenia ( 62.1%; vs 0% ).
Treatment discontinuation due to adverse effects was reported for 2.5% of patients with Dalpiciclib - Fulvestrant vs 3.3% with Placebo - Fulvestrant.
The incidence of severe adverse effect was 5.8% with Dalpiciclib - Fulvestrant vs 6.7% with Placebo - Fulvestrant.
In conclusion, the study met its primary endpoint, demonstrating that Dalpiciclib plus Fulvestrant has significantly improved progression-free survival versus placebo plus Fulvestrant, with a manageable safety profile.
The findings support Dalpiciclib plus Fulvestrant as a new treatment option in patients with HR+/HER2- advanced breast cancer who relapsed or progressed on endocrine therapy. ( Xagena )
Xu B et al, J Clin Oncol 2021;39:(suppl 15; abstr 1002). doi:10.1200/JCO.2021.39.15_suppl.1002