The 4-year results from monarchE indicate that the invasive disease-free survival gain offered by adjuvant abemaciclib in people with high-risk, hormone receptor-positive, HER2-negative, early breast cancer is maintained even after the 2-year treatment period.

Updated findings from the MONARCH 3 trial show a nonsignificant overall survival gain with the addition of abemaciclib to a first-line nonsteroidal aromatase inhibitor in postmenopausal patients with hormone receptor-positive, HER2-negative advanced breast cancer.

The incidence of thrombosis among people receiving the CDK4/6 inhibitor abemaciclib for metastatic breast cancer is approximately threefold higher in a real-world setting than that observed in clinical trials, US study data show.

medwireNews : The EMA’s Committee for Medicinal Products for Human Use (CHMP) has recommended adopting a new indication for abemaciclib  as adjuvant therapy for early breast cancer patients at high risk for recurrence.

The patient-reported outcomes from the monarchE trial add support for the addition of abemaciclib to endocrine therapy in the treatment of high-risk, early breast cancer, say the researchers.

A phase 2 trial has demonstrated promising antitumor activity and manageable toxicity of abemaciclib in previously treated patients with p16ink4A-negative malignant mesothelioma.

The FDA also approved a companion diagnostic assay – namely Ki-67 IHC MIB-1 pharmDx (Agilent, Inc, Santa Clara, California, USA) – to identify patients who can receive abemaciclib.

Further follow-up of the monarchE trial shows that the addition of abemaciclib to adjuvant endocrine therapy continues to offer an invasive disease-free survival benefit to patients with high-risk, hormone receptor-positive, HER2-negative, early breast cancer.

Adding abemaciclib to adjuvant endocrine therapy significantly reduces the risk for recurrence in patients with high-risk, hormone receptor-positive, HER2-negative, early breast cancer, show phase 3 trial findings.

Abemaciclib has also been approved by the US FDA in both these first-line and subsequent settings.

medwireNews : The US FDA has granted approval for the use of abemaciclib against HR-positive, HER2-negative advanced or metastatic breast cancer in patients who have progressed during endocrine therapy.

Adverse events associated with abemaciclib include diarrhea, neutropenia, fatigue, infection, nausea, abdominal pain, and anemia.

Results from the MONARCH 3 study give support to first-line use of the oral selective CDK4/6 inhibitor abemaciclib, taken alongside nonsteroidal aromatase inhibitor therapy, in patients with advanced hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. Click here for an expert comment on the trial.

She added that the results are “good news for our patients,” as now there are two CDK4/6 inhibitors – ribociclib and abemaciclib – “that increase the chances for cure in this setting, both with an acceptable safety profile.”

The discussant said that the PFS HRs for both the DAWNA-1 trial of endocrine-resistant disease and the DAWNA-2 trial of endocrine-sensitive tumors are “consistent” with phase 3 trial findings for palbociclib, ribociclib, and abemaciclib in these settings.

The guideline makes no change to the first-line treatment option of trastuzumab, pertuzumab, plus a taxane, but recommends trastuzumab deruxtecan as a new second-line option and several new options in the third and later line, including regimens with tucatinib, trastuzumab emtansine, margetuximab, and abemaciclib plus trastuzumab and fulvestrant.

The most common prior CDK4/6 inhibitor was palbociclib (84%) followed by ribociclib (11%), palbociclib plus another CDK4/6 inhibitor (3%), and abemaciclib (2%).

Ruth O'Regan comments on the monarchE trial of abemaciclib and the PENELOPE-B and PALLAS trials of palbociclib investigating CDK4/6 inhibitor therapy in the adjuvant, hormone receptor-positive, early-stage breast cancer setting (6:35).

George Sledge Jr speculates on the reasons for the contrasting results of the monarchE and PALLAS trials of adjuvant abemaciclib and palbociclib, respectively, in hormone receptor-positive, early-stage breast cancer.

The investigators also point out the three CDK4/6 inhibitors had differing AE profiles, such that palbociclib and ribociclib were primarily associated with hematologic toxicity and abemaciclib with diarrhea and fatigue.