Combination Therapy with Abemaciclib (MONARCH 2)
The safety of fulvestrant (500 mg) plus abemaciclib (150 mg twice daily) versus fulvestrant plus placebo was evaluated in MONARCH 2. The data described below reflect exposure to fulvestrant in 664 patients with HR-positive, HER2-negative advanced breast cancer who received at least one dose of fulvestrant plus abemaciclib or placebo in MONARCH 2.
Median duration of treatment was 12 months for patients receiving fulvestrant plus abemaciclib and 8 months for patients receiving fulvestrant plus placebo.
Dose reductions due to an adverse reaction occurred in 43% of patients receiving fulvestrant plus abemaciclib. Adverse reactions leading to dose reductions ≥5% of patients were diarrhea and neutropenia. Abemaciclib dose reduction due to diarrhea of any grade occurred in 19% of patients receiving fulvestrant plus abemaciclib compared to 0.4% of patients receiving fulvestrant plus placebo.
Abemaciclib dose reductions due to neutropenia of any grade occurred in 10% of patients receiving fulvestrant plus abemaciclib compared to no patients receiving fulvestrant plus placebo.
Permanent study treatment discontinuation due to an adverse event was reported in 9% of patients receiving fulvestrant plus abemaciclib and in 3% of patients receiving fulvestrant plus placebo. Adverse reactions leading to permanent discontinuation for patients receiving fulvestrant plus abemaciclib were infection (2%), diarrhea (1%), hepatotoxicity (1%), fatigue (0.7%), nausea (0.2%), abdominal pain (0.2%), acute kidney injury (0.2%), and cerebral infarction (0.2%).
Deaths during treatment or during the 30-day follow up, regardless of causality, were reported in 18 cases (4%) of fulvestrant plus abemaciclib treated patients versus 10 cases (5%) of fulvestrant plus placebo treated patients. Causes of death for patients receiving fulvestrant plus abemaciclib included: 7 (2%) patient deaths due to underlying disease, 4 (0.9%) due to sepsis, 2 (0.5%) due to pneumonitis, 2 (0.5%) due to hepatotoxicity, and one (0.2%) due to cerebral infarction.
The most common adverse reactions reported (≥20%) in the fulvestrant plus abemaciclib arm were diarrhea, fatigue, neutropenia, nausea, infections, abdominal pain, anemia, leukopenia, decreased appetite, vomiting, and headache (
Table 7). The most frequently reported (≥5%) Grade 3 or 4 adverse reactions were neutropenia, diarrhea, leukopenia, anemia, and infections.
Table 7: Adverse Reactions ≥10% of Patients Receiving Fulvestrant Plus Abemaciclib and ≥2% Higher Than Fulvestrant Plus Placebo in MONARCH 2 | 1. Includes abdominal pain, abdominal pain upper, abdominal pain lower, abdominal discomfort, abdominal tenderness.
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| 2. Includes upper respiratory tract infection, urinary tract infection, lung infection, pharyngitis, conjunctivitis, sinusitis, vaginal infection, sepsis.
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| 3. Includes neutropenia, neutrophil count decreased.
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| 4. Includes anemia, hematocrit decreased, hemoglobin decreased, red blood cell count decreased.
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| 5. Includes leukopenia, white blood cell count decreased.
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| 6. Includes platelet count decreased, thrombocytopenia.
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| 7. Includes asthenia, fatigue.
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Adverse Reactions
| Fulvestrant plus Abemaciclib N=441 | Fulvestrant plus Placebo N=223 |
All Grades % | Grade 3 % | Grade 4 % | All Grades % | Grade 3 % | Grade 4 % |
Gastrointestinal Disorders |
Diarrhea | 86 | 13 | 0 | 25 | <1 | 0 |
Nausea | 45 | 3 | 0 | 23 | 1 | 0 |
Abdominal pain
1
| 35 | 2 | 0 | 16 | 1 | 0 |
Vomiting | 26 | <1 | 0 | 10 | 2 | 0 |
Stomatitis | 15 | <1 | 0 | 10 | 0 | 0 |
Infections and Infestations |
Infections
2
| 43 | 5 | <1 | 25 | 3 | <1 |
Blood and Lymphatic System Disorders |
Neutropenia
3
| 46 | 24 | 3 | 4 | 1 | <1 |
Anemia
4
| 29 | 7 | <1 | 4 | 1 | 0 |
Leukopenia
5
| 28 | 9 | <1 | 2 | 0 | 0 |
Thrombocytopenia
6
| 16 | 2 | 1 | 3 | 0 | <1 |
General Disorders and Administration Site Conditions |
Fatigue
7
| 46 | 3 | 0 | 32 | <1 | 0 |
Edema peripheral | 12 | 0 | 0 | 7 | 0 | 0 |
Pyrexia | 11 | <1 | <1 | 6 | <1 | 0 |
Metabolism and Nutrition Disorders |
Decreased appetite | 27 | 1 | 0 | 12 | <1 | 0 |
Respiratory, Thoracic, and Mediastinal Disorders |
Cough | 13 | 0 | 0 | 11 | 0 | 0 |
Skin and Subcutaneous Tissue Disorders |
Alopecia | 16 | 0 | 0 | 2 | 0 | 0 |
Pruritus | 13 | 0 | 0 | 6 | 0 | 0 |
Rash | 11 | 1 | 0 | 4 | 0 | 0 |
Nervous System Disorders |
Headache | 20 | 1 | 0 | 15 | <1 | 0 |
Dysgeusia | 18 | 0 | 0 | 3 | 0 | 0 |
Dizziness | 12 | 1 | 0 | 6 | 0 | 0 |
Investigations |
Alanine aminotransferase increased | 13 | 4 | <1 | 5 | 2 | 0 |
Aspartate aminotransferase increased | 12 | 2 | 0 | 7 | 3 | 0 |
Creatinine increased | 12 | <1 | 0 | <1 | 0 | 0 |
Weight decreased | 10 | <1 | 0 | 2 | <1 | 0 |
Additional adverse reactions in MONARCH 2 include venous thromboembolic events (deep vein thrombosis, pulmonary embolism, cerebral venous sinus thrombosis, subclavian vein thrombosis, axillary vein thrombosis, and DVT inferior vena cava), which were reported in 5% of patients treated with fulvestrant plus abemaciclib as compared to 0.9% of patients treated with fulvestrant plus placebo.
Table 8: Laboratory Abnormalities ≥10% in Patients Receiving Fulvestrant Plus Abemaciclib and ≥2% Higher Than Fulvestrant Plus Placebo in MONARCH 2 Laboratory Parameters | Fulvestrant plus Abemaciclib N=441 | Fulvestrant plus Placebo N=223 |
All Grades % | Grade 3 % | Grade 4 % | All Grades % | Grade 3 % | Grade 4 % |
Creatinine increased | 98 | 1 | 0 | 74 | 0 | 0 |
White blood cell decreased | 90 | 23 | <1 | 33 | <1 | 0 |
Neutrophil count decreased | 87 | 29 | 4 | 30 | 4 | <1 |
Anemia | 84 | 3 | 0 | 33 | <1 | 0 |
Lymphocyte count decreased | 63 | 12 | <1 | 32 | 2 | 0 |
Platelet count decreased | 53 | <1 | 1 | 15 | 0 | 0 |
Alanine aminotransferase increased | 41 | 4 | <1 | 32 | 1 | 0 |
Aspartate aminotransferase increased | 37 | 4 | 0 | 25 | 4 | <1 |