Variation in Adherence Measures to Imatinib Therapy

JAK2 as Predictor of Therapeutic Response in Patients with Chronic Myeloid Leukemia Treated with Imatinib

Background

Chronic myeloid leukemia (CML) or chronic granulocytic leukemia is a myeloproliferative neoplasm indicated by the presence of the Philadelphia (Ph+) chromosome. First-line tyrosine kinase inhibitor, imatinib, is the gold standard for treatment. However, there has been known unresponsiveness to treatment, especially due to the involvement of other genes, such as the Janus kinase 2 (JAK2) gene. This study aimed to evaluate the relationships between JAK2 levels and complete hematological response (CHR), as well as early molecular response (EMR) after 3 months of imatinib treatment in patients with chronic phase CML.

Methods

Patients with Ph+ CML in the chronic phase (n = 40; mean age, 40 ± 11 years) were recruited to complete assessments consisting of clinical examination and blood test, including evaluation of complete blood counts and the JAK2 levels, at baseline and following 3 months of therapy with imatinib (at an oral dose of 400 mg per day). Subjects were divided into two groups according to the presence of CHR and EMR.

Results

JAK2 gene levels, phosphorylated, and total JAK2 proteins at baseline were significantly lower in the group with the presence of CHR and EMR. In addition, baseline JAK2 levels, including JAK2 gene expression, phosphorylated, and total JAK2 proteins, were negatively correlated with the presence of CHR and EMR.

Conclusions

Based on these findings, JAK2 levels may be a potential indicator for evaluating treatment response on imatinib due to its role in the pathophysiology of CML.

Meeting the needs of CML patients in resource-poor countries

Subsequent to the development and global availability of BCR/ABL-targeted tyrosine kinase inhibitors (TKIs), the prognosis of patients with chronic myeloid leukemia (CML), at least those in the chronic phase, has markedly improved, and in the developed world, the average lifespan of these patients is now close to that of age- and sex-matched subjects without the disease. However, the situation in low- and middle-income countries (LMICs) may not be so rosy. Many important differences in hematological cancers, including CML, have been highlighted in various publications in LMICs vs developed countries. These include differences in incidence and prevalence rates, age and stage of disease at diagnosis, response rates, and survival. Some of the possible reasons proposed for these are varying socioeconomic milieu (impacting availability of effective drugs and essential monitoring), environmental factors (mainly exposure to viral infections and pesticides), nutritional factors with interplay of malnutrition and diet on drug absorption and blood levels, and possible unknown genetic factors. Although generic first-generation TKIs (imatinib) are available in many parts of the world, several challenges remain in providing optimal treatment to patients with CML in resource-poor countries. Some of these include availability of optimal and high-quality BCR/ABL testing, availability and expense related to use of second- and third-generation TKIs (nilotinib, dasatinib, bosutinib, and ponatinib) and hematopoietic stem cell transplantation, issues with compliance and toxicities of drugs, and ensuring a minimal standard-of-care treatment and monitoring for every patient diagnosed with CML. For the purpose of this article, the more objective country label-LMIC-coined by the World Bank will be used (gross national income per capita between $1026 and $3995; World Bank, June 2019). Some of these issues will be discussed in this article in greater detail by experts in the field in 3 different but interconnected sections.