MONARCH 1, A Phase II Study of Abemaciclib, a CDK4 and CDK6 Inhibitor, as a Single Agent, in Patients with Refractory HR+/HER2− Metastatic Breast Cancer
- Study type
- Clinical trial
- Study name
- MONARCH 1
- Phase
- Phase 2
- Design
- Single-arm, open-label phase 2 study
- Sample size
- 132 patients
- Source
- Clinical Cancer Research · 2017
In plain words
This study tested the drug abemaciclib, taken as a tablet on its own, in women with advanced breast cancer that had stopped responding to earlier treatments (hormone therapy and chemotherapy). In about one in five patients the tumours shrank, and the typical time without the disease getting worse was 6 months. The most common side effects were diarrhoea, tiredness and nausea, and only a few patients (7.6%) stopped treatment because of side effects.
Key results
Treatment arms and regimens
Abemaciclib 200 mg orally every 12 hours, continuously until disease progression or unacceptable toxicity.
Source of the regimen details: Abstract of the paper
Doses are given for the information of specialists, as in this study’s protocol, and are not a prescription. Every drug must be prescribed by the treating physician for the individual patient.
Study population
Women with HR-positive/HER2-negative metastatic breast cancer that had progressed on or after prior endocrine therapy and who had received 1 or 2 chemotherapy regimens in the metastatic setting. Patients had received a median of 3 prior systemic therapies (range 1 to 8) in the metastatic setting; 90.2% had visceral disease and 50.8% had at least 3 metastatic sites.
Endpoints
Primary objective: investigator-assessed objective response rate (ORR). Other endpoints: clinical benefit rate, progression-free survival (PFS) and overall survival (OS). The study also aimed to evaluate the single-agent activity and adverse event profile of abemaciclib.
Safety and side effects
The most common treatment-emergent adverse events of any grade were diarrhoea, fatigue and nausea. Discontinuation due to adverse events was infrequent (7.6%). Rates of grade 3 or higher adverse events are not reported in the abstract; the full text should be consulted.
Clinical significance and place in guidelines
This single-arm phase 2 study showed that single-agent abemaciclib has promising clinical activity and acceptable tolerability in heavily pretreated patients with HR-positive/HER2-negative metastatic breast cancer. The abstract gives no information on regulatory approvals or the drug's place in guidelines; these should be checked separately in current sources.
Limitations
The study was single-arm, open-label and uncontrolled, so direct comparison with other treatments is not possible. The lower bound of the 95% CI for ORR (13.3%) was below 15%, so a rate of 15% was not excluded. The primary endpoint was investigator-assessed. An erratum has been published for this paper.
This summary was prepared by the editorial team from the published paper; the original paper is the final reference. Read the original abstract on PubMed.