Will the targeted drug bosutinib/bosutinib grow wildly once the drug is discontinued?

Bosutinib/Bosutinib is a targeted therapy drug mainly used to treat hematological malignancies such as chronic myelogenous leukemia (CML). Patients' disease is usually effectively controlled while being treated with bosutinib, but responses after discontinuation vary among individuals.

Based on the mechanism of action of bosutinib, it inhibits the tyrosine kinase activity in cancer cells, thereby preventing the growth and proliferation of tumor cells. However, once the drug is stopped, the inhibitory effect on its target in the body disappears, and the cancer cells may regain the ability to grow. In some patients, a relapse may occur after discontinuation of the drug, sometimes referred to as the "rebound effect." The specific manifestation is that the number of leukemia cells increases rapidly, leading to aggravation of symptoms.

The question of whether will "grow crazy" is actually not completely accurate. First, the response after stopping the drug varies from person to person. About 50% of patients can maintain remission without restarting treatment. However, monitoring after discontinuation of the drug is very important. After the patient stops taking the drug, doctors will regularly detect the level of BCR-ABL1 in the peripheral blood through polymerase chain reaction (PCR), so that possible signs of recurrence can be detected in time. Close monitoring is crucial, especially during the first year after stopping the drug.

In clinical practice, although there are a few cases where the disease progresses to the accelerated phase or blast phase after drug withdrawal, this is not a common phenomenon. Moreover, even if this occurs, the vast majority of patients regain a good response after restarting TKI treatment. It should be noted that this transition may also occur in patients who continue to receive TKI treatment, so discontinuation does not automatically mean an exacerbation of the disease.

The goal of treatment-free remission (TFR) not only enables patients to enjoy a higher quality of life, but also reduces the risk of long-term complications and the cost of treatment. Because of this, more and more research is devoted to exploring how to achieve this goal safely and provide patients with more options.

Reference materials:https://pmc.ncbi.nlm.nih.gov/articles/PMC7716356/