What is Verzenio (abemaciclib) and its side effects?

Verzenio (Abemaciclib): Medication Overview and Side Effects

What is Verzenio?

Verzenio (abemaciclib) is an oral CDK 4/6 inhibitor approved for treating hormone receptor-positive, HER2-negative breast cancer in both early and advanced disease settings. 1

FDA-Approved Indications

Verzenio is specifically approved for: 1

• Early breast cancer: Combined with endocrine therapy (tamoxifen or aromatase inhibitor) for node-positive disease with high recurrence risk
• First-line metastatic disease: Combined with aromatase inhibitor as initial endocrine-based therapy
• Second-line metastatic disease: Combined with fulvestrant after disease progression on endocrine therapy alone
• Later-line metastatic disease: As monotherapy after progression on endocrine therapy and prior chemotherapy

Mechanism and Clinical Use

Abemaciclib works by selectively inhibiting cyclin-dependent kinases 4 and 6, which regulate cell cycle progression from G1 to S phase. 2 The NCCN guidelines recommend CDK 4/6 inhibitors (including abemaciclib) as Category 1 first-line options when combined with aromatase inhibitors for postmenopausal women and premenopausal women receiving ovarian suppression. 3

In the adjuvant setting, abemaciclib for 2 years plus endocrine therapy is recommended for patients with ≥4 positive lymph nodes or 1-3 positive nodes with additional high-risk features (grade 3 disease, tumor size ≥5 cm, or Ki-67 ≥20%). 3

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Side Effects of Verzenio

Most Common Side Effects

Diarrhea is the most frequent adverse event, occurring in 81-90% of patients, though primarily grade 1-2 severity. 3, 1

The most common side effects include: 1

• Diarrhea (most common, up to 90%)
• Fatigue (40-65%)
• Nausea (45-64%)
• Neutropenia (46%)
• Decreased appetite (46%)
• Abdominal pain
• Infections
• Anemia (low red blood cell counts)
• Leukopenia (low white blood cell counts)
• Thrombocytopenia (low platelet counts)
• Headache
• Hair thinning or hair loss

Serious Side Effects Requiring Immediate Medical Attention

Five potentially life-threatening complications require immediate reporting to healthcare providers. 1

1. Severe Diarrhea

• Most common during the first month of treatment 1
• Can lead to dehydration or infection 1
• Grade 3 or higher diarrhea occurs in 9.5-13.4% of patients 3
• Management: Start antidiarrheal medication (loperamide) immediately, increase fluid intake, and contact provider 1
• Median time to onset: 1 week; duration: 6-12 days depending on grade 4

2. Neutropenia (Low White Blood Cell Counts)

• Grade 3-4 neutropenia occurs in 21-27% of patients 3
• Can cause serious infections leading to death 1
• Febrile neutropenia is rare (0.7%) 4
• Warning signs: Fever, chills, signs of infection 1
• Requires blood count monitoring before and during treatment 1

3. Interstitial Lung Disease/Pneumonitis

• Occurs in 3.4% of patients 4
• Can be severe or life-threatening 1
• Symptoms to report: Trouble breathing, shortness of breath, cough (with or without mucus), chest pain 1
• Treated with corticosteroids and/or antibiotics 4

4. Liver Problems (Hepatotoxicity)

• Requires blood tests to monitor liver function 1
• Warning signs: Extreme fatigue, upper right abdominal pain, loss of appetite, easy bleeding or bruising 1

5. Venous Thromboembolism (Blood Clots)

• Occurs in 5.3% of patients 4
• Can be fatal 1
• Symptoms: Pain or swelling in arms/legs, shortness of breath, chest pain, rapid breathing, rapid heart rate 1
• Primarily managed with anticoagulants 4

Dose Modifications and Management

Adverse events are effectively managed through supportive medications and dose adjustments without compromising progression-free survival. 4

Common management strategies include: 4

• Diarrhea: Antidiarrheal medication (72.8%), dose omissions (17.3%), dose reductions (16.7%)
• Neutropenia: Dose omissions (16.8%), dose reductions (11.2%)
• Highest rates of grade ≥2 diarrhea occur in first cycles and decrease subsequently 4

Important Precautions

Patients must: 1

• Avoid ketoconazole during treatment
• Avoid grapefruit and grapefruit products (increases abemaciclib blood levels)
• Use effective contraception during treatment and for 3 weeks after last dose
• Not breastfeed during treatment and for 3 weeks after last dose
• Take tablets whole at the same time daily (do not crush, chew, or split)
• Inform providers of all medications, including over-the-counter drugs and supplements

Fertility Considerations

Abemaciclib may cause fertility problems in males, potentially affecting the ability to father children. 1