Zanubrutinib, known by its brand name Brukinsa, is a prescription medication used to treat certain types of blood cancers in adults. This medication is a targeted therapy designed to specifically interfere with cancer cell growth and spread.
Understanding Zanbrutinib
Zanubrutinib belongs to a class of medications called Bruton’s tyrosine kinase (BTK) inhibitors. BTK is an enzyme that plays a role in the survival and proliferation of malignant B-cells, which are a type of white blood cell involved in certain cancers. The BTK protein sends continuous signals that encourage cancerous B cells to grow and spread.
Zanubrutinib works by forming a strong, covalent bond with a specific amino acid (cysteine 481) in the active site of the BTK enzyme. This binding action irreversibly inhibits BTK activity, effectively shutting down the signaling pathway that supports the cancer cells. By blocking this pathway, zanubrutinib disrupts the proliferation, trafficking, and adhesion of malignant B cells, ultimately leading to a reduction in tumor size.
Conditions Treated by Zanbrutinib
Zanubrutinib is approved for treating several specific types of blood cancers. It is indicated for adults with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL), which are slow-growing cancers affecting white blood cells and lymph nodes respectively. The U.S. Food and Drug Administration (FDA) approved zanubrutinib for CLL/SLL.
The medication is also approved for adults with Waldenström’s macroglobulinemia (WM), a rare, slow-growing cancer that starts in certain white blood cells in the bone marrow. Additionally, it is used for adults with mantle cell lymphoma (MCL) who have received at least one prior therapy, and for relapsed or refractory marginal zone lymphoma (MZL) in adults who have received at least one anti-CD20-based regimen. Furthermore, zanubrutinib is approved in combination with obinutuzumab for relapsed or refractory follicular lymphoma (FL) in adults after two or more lines of systemic therapy.
Taking Zanbrutinib and Potential Side Effects
Zanubrutinib is administered orally as a capsule. The typical dosage is either 160 mg taken twice daily or 320 mg taken once daily. It can be taken with or without food, but capsules should be swallowed whole with water and not opened, broken, or chewed. Treatment usually continues until the disease progresses or unacceptable side effects occur.
Common side effects of zanubrutinib can include decreased neutrophil count, upper respiratory tract infection, decreased platelet count, hemorrhage (bleeding), rash, bruising, and musculoskeletal pain. Gastrointestinal issues such as diarrhea, constipation, nausea, and vomiting are also frequently reported.
More serious potential side effects include severe bleeding, which can be life-threatening and may manifest as blood in stools or urine, or severe bruising. Zanubrutinib can also increase the risk of serious infections, including pneumonia, and may cause heart rhythm problems such as atrial fibrillation or atrial flutter, especially in patients with existing cardiac risk factors. Additionally, decreases in blood cell counts (white blood cells, platelets, and red blood cells) and liver problems have been observed. Patients should seek medical attention immediately if they experience signs of serious bleeding, infection, or heart rhythm changes.
Key Patient Considerations
Patients taking zanubrutinib should be aware of potential drug interactions. Strong or moderate inhibitors of certain liver enzymes can significantly increase zanubrutinib levels in the body, potentially leading to increased side effects. Conversely, strong or moderate inducers of these enzymes can decrease zanubrutinib levels, reducing its effectiveness, and should generally be avoided.
Regular monitoring is an important part of treatment with zanubrutinib. Healthcare providers will routinely monitor complete blood counts to check for reductions in white blood cells, platelets, and red blood cells. Liver function tests and heart function monitoring, including checks for cardiac arrhythmias, are also conducted to detect any adverse effects. Patients should be advised to use sun protection as there is an increased risk of developing new cancers, particularly skin cancer.
For women of reproductive potential, pregnancy testing is recommended before starting zanubrutinib, and effective contraception should be used during treatment and for at least one week after the last dose, as animal studies indicate potential harm to a fetus. Men should also use effective contraception and avoid fathering a child during treatment and for at least one week after the last dose. Breastfeeding is not recommended during treatment with zanubrutinib and for at least two weeks following the last dose due to the potential for serious adverse reactions in a breastfed child. Patients should discuss any other medical conditions or medications they are taking with their healthcare provider to ensure safe and effective treatment.