Bosulif, with the active substance bosutinib, is a medication for treating Chronic Myeloid Leukemia (CML). As a targeted therapy, it is designed to act on specific molecular targets associated with cancer. Bosulif is classified as a tyrosine kinase inhibitor (TKI), a class of drugs that interferes with enzymes involved in cancer cell growth. It is prescribed for adults and some children with CML characterized by the Philadelphia chromosome abnormality. The medication’s purpose is to control the disease by targeting the underlying cellular mechanisms that drive the leukemia.
How Bosulif Targets CML Cells
Chronic Myeloid Leukemia is driven by a specific genetic abnormality where parts of chromosome 9 and 22 swap places. This creates an altered, shorter chromosome 22 known as the Philadelphia chromosome. This event forms a new fusion gene called BCR-ABL, which is not found in healthy cells.
The BCR-ABL gene produces an abnormal protein called a tyrosine kinase. In healthy cells, tyrosine kinases regulate cell growth, but the BCR-ABL kinase is constantly active. It sends continuous signals that cause the bone marrow to produce an excess of abnormal white blood cells. Bosulif functions by specifically targeting and inhibiting this overactive BCR-ABL tyrosine kinase. By blocking the enzyme, Bosulif interrupts the signaling pathway that drives uncontrolled cell multiplication, leading to a reduction in leukemia cells while having a minimal effect on many healthy cells.
Who Is Prescribed Bosulif
One primary use for Bosulif is as a first-line treatment for adults newly diagnosed with CML in its chronic phase, which is the earliest and most treatable stage. The medication is also an option for patients who have not had success with other treatments. It is approved for adults with CML in the chronic, accelerated, or blast phases who have previously been treated with other tyrosine kinase inhibitors. This includes individuals whose leukemia is resistant to other TKIs, where the previous medications are no longer effective. It is also for patients who are intolerant to prior therapies, meaning they experienced side effects too severe to continue treatment.
Taking Bosulif Correctly
Bosulif is an oral tablet taken once daily with a meal. Taking it with food helps the body absorb the drug and can lessen stomach-related side effects. For adults with newly diagnosed chronic phase CML, the starting dose is 400 mg once a day. For patients taking Bosulif due to resistance or intolerance to a prior therapy, the starting dose is 500 mg once daily. A physician determines the precise dose and may adjust it based on treatment response and side effects.
Patients should swallow the tablets whole without crushing, cutting, or chewing them. If a dose is missed by more than 12 hours, the patient should skip that dose and take the next one at the regularly scheduled time. An extra dose should not be taken to make up for the missed one, as this can increase the risk of side effects.
Potential Side Effects of Bosulif
The most common side effects are gastrointestinal issues, including diarrhea, nausea, vomiting, and abdominal pain; diarrhea is particularly frequent. Other common effects include skin rash, fatigue, fever, and headache. Patients should report these symptoms to their healthcare provider.
Bosulif can also cause more serious health issues that require medical attention. The medication can affect liver function, leading to elevated liver enzymes, so regular blood tests are performed to monitor for liver problems. Fluid retention is another potential effect, which can manifest as swelling in the ankles, hands, or feet, or as fluid buildup around the lungs or heart. Other reported serious effects include heart problems, kidney issues, and low blood cell counts such as anemia, neutropenia, and thrombocytopenia.
Measuring Treatment Success
The effectiveness of Bosulif treatment is tracked through regular tests that measure the body’s response. One of the first indicators is the hematologic response, evaluated with a complete blood count (CBC). The goal of a complete hematologic response is for the numbers of white blood cells, red blood cells, and platelets to return to and remain within normal ranges.
A deeper level of monitoring involves a cytogenetic response, which looks for the Philadelphia chromosome in cells from the bone marrow. A bone marrow sample is analyzed to count the percentage of cells that contain this genetic abnormality. A complete cytogenetic response (CCyR) is achieved when no cells with the Philadelphia chromosome are detected.
The most sensitive measure is the molecular response, assessed with a quantitative polymerase chain reaction (qPCR) blood test. This test detects and quantifies the amount of the BCR-ABL fusion gene’s messenger RNA (mRNA). The goal is to achieve a major molecular response (MMR), where the levels of the BCR-ABL gene are very low or undetectable.