Managing imatinib resistance in chronic myeloid leukaemia:

A Comprehensive Review of Cancer Drug-Induced Cardiotoxicity in Blood Cancer Patients: Current Perspectives and Therapeutic Strategies

Cardiotoxicity has emerged as a serious outcome catalyzed by various therapeutic targets in the field of cancer treatment, which includes chemotherapy, radiation, and targeted therapies. The growing significance of cancer drug-induced cardiotoxicity (CDIC) and radiation-induced cardiotoxicity (CRIC) necessitates immediate attention. This article intricately unveils how cancer treatments cause cardiotoxicity, which is exacerbated by patient-specific risks. In particular, drugs like anthracyclines, alkylating agents, and tyrosine kinase inhibitors pose a risk, along with factors such as hypertension and diabetes. Mechanistic insights into oxidative stress and topoisomerase-II-B inhibition are crucial, while cardiac biomarkers show early damage. Timely intervention and prompt treatment, especially with specific agents like dexrazoxane and beta-blockers, are pivotal in the proactive management of CDIC.

ABL1 tyrosine kinase domain mutations in chronic myeloid leukemia treatment resistance

The development of mutations in the BCR-ABL1 fusion gene transcript causes resistance to tyrosine kinase inhibitors (TKIs) based therapy in chronic myeloid leukemia (CML). Thereby, screening for BCR-ABL1 mutations is advised especially in patients undergoing poor response to treatment. In the current study the authors investigated 43 patients with CML that failed or had suboptimal response to TKIs treatment. Blood samples were collected from patients that were treated with TKIs. The analysis of genetic mutations was performed using a semi-nested PCR assay, followed by Sanger sequencing. The analysis revealed 15 mutations (32.55%): 14 point mutations and an exon 7 deletion. In roughly 30% of cases, mutations in the BCR-ABL1 fusion gene are common causes for treatment resistance.

Detecting Autophagy and Autophagy Flux in Chronic Myeloid Leukemia Cells Using a Cyto-ID Fluorescence Spectrophotometric Assay

Autophagy is a catabolic process whereby cellular components are degraded to fuel cells for longer survival during stress. Hence, autophagy plays a vital role in determining cell fate and is central for homeostasis and pathogenesis of many human diseases including chronic myeloid leukemia (CML). It has been well established that autophagy is important for the leukemogenesis as well as drug resistance in CML. Thus, autophagy is an intriguing therapeutic target. However, current approaches that detect autophagy lack reliability and often fail to provide quantitative measurements. To overcome this hurdle and facilitate the development of autophagy-related therapies, we have recently developed an autophagy assay termed as the Cyto-ID fluorescence spectrophotometric assay. This method uses a cationic fluorescence dye, Cyto-ID, which specifically labels autophagic compartments and is detected by a spectrophotometer to permit a large-scale and quantitative analysis. As such, it allows rapid, reliable, and quantitative detection of autophagy and estimation of autophagy flux. In this chapter, we further provide technical details of this method and step-by-step protocols for measuring autophagy or autophagy flux in CML cell lines as well as primary hematopoietic cells.

Nilotinib rapidly reverses breakpoint cluster region-Abelson oncogene fusion gene and M244V mutations in a patient with chronic myelogenous leukemia: A case report

Chronic myelogenous leukemia (CML) is a condition characterized by a balanced genetic translocation, t (9;22) (q34;q11.2), which leads to a fusion of the Abelson oncogene (ABL) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is referred to as the Philadelphia chromosome. At a molecular level, this translocation results in the formation of the BCR-ABL fusion oncogene, which translates into a BCR-ABL oncoprotein. Imatinib, nilotinib and dasatinib are three tyrosine kinase inhibitors that have been approved by the US Food and Drug Administration for the treatment of patients diagnosed with CML in the chronic phase (CML-CP). The present study describes the case of a patient with imatinib-resistant CML who, following two months of treatment with nilotinib, no longer exhibited detectable BCR-ABL fusion genes or M244V mutations. This suggests that nilotinib may be effective for treating CML cases in which the BCR-ABL fusion protein has an M244V mutation.

Potent mechanism-based inhibition of CYP3A4 by imatinib explains its liability to interact with CYP3A4 substrates

BACKGROUND AND PURPOSE

Imatinib, a cytochrome P450 2C8 (CYP2C8) and CYP3A4 substrate, markedly increases plasma concentrations of the CYP3A4/5 substrate simvastatin and reduces hepatic CYP3A4/5 activity in humans. Because competitive inhibition of CYP3A4/5 does not explain these in vivo interactions, we investigated the reversible and time-dependent inhibitory effects of imatinib and its main metabolite N-desmethylimatinib on CYP2C8 and CYP3A4/5 in vitro.

EXPERIMENTAL APPROACH

Amodiaquine N-deethylation and midazolam 1'-hydroxylation were used as marker reactions for CYP2C8 and CYP3A4/5 activity. Direct, IC(50) -shift, and time-dependent inhibition were assessed with human liver microsomes.

KEY RESULTS

Inhibition of CYP3A4 activity by imatinib was pre-incubation time-, concentration- and NADPH-dependent, and the time-dependent inactivation variables K(I) and k(inact) were 14.3 µM and 0.072 in(-1) respectively. In direct inhibition experiments, imatinib and N-desmethylimatinib inhibited amodiaquine N-deethylation with a K(i) of 8.4 and 12.8 µM, respectively, and midazolam 1'-hydroxylation with a K(i) of 23.3 and 18.1 µM respectively. The time-dependent inhibition effect of imatinib was predicted to cause up to 90% inhibition of hepatic CYP3A4 activity with clinically relevant imatinib concentrations, whereas the direct inhibition was predicted to be negligible in vivo.

CONCLUSIONS AND IMPLICATIONS

Imatinib is a potent mechanism-based inhibitor of CYP3A4 in vitro and this finding explains the imatinib-simvastatin interaction and suggests that imatinib could markedly increase plasma concentrations of other CYP3A4 substrates. Our results also suggest a possibility of autoinhibition of CYP3A4-mediated imatinib metabolism leading to a less significant role for CYP3A4 in imatinib biotransformation in vivo than previously proposed.

The expanding options for front-line treatment in patients with newly diagnosed CML

The past decade has seen remarkable advances in the treatment of chronic myeloid leukemia (CML). The discovery of the underlying cause of CML, a chromosomal translocation resulting in the expression of an aberrant tyrosine kinase, has enabled the rational development of targeted therapy with tyrosine kinase inhibitors (TKIs). The first available TKI, imatinib, dramatically improved survival rates and demonstrated the potential for long-term treatment. A number of additional strategies have been tested to further maximize outcomes in patients with newly diagnosed CML, including newer TKIs, imatinib dose escalation, and combination therapy. The advanced, more potent TKIs, nilotinib and dasatinib, have proven effective for newly diagnosed patients and for those who experience inadequate response or intolerance to imatinib. Randomized phase 3 studies have shown that nilotinib and dasatinib are more efficacious than imatinib in achieving primary study endpoints. Nilotinib was superior to imatinib in the rate of major molecular response at 12 months; dasatinib was superior to imatinib in the rate of complete cytogenetic response by 12 months. These phase 3 studies are ongoing to further define longer-term efficacy and safety. Research on additional contributing signaling pathways in CML, T315I mutations, and other causes of treatment resistance has identified additional potential treatments that are now in early stages of clinical development, with encouraging preliminary results. With continued advances, it is conceivable that the ultimate goal - a cure for CML - is in our sights.

Use of tyrosine kinase inhibitors for chronic myeloid leukemia: management of patients and practical applications for pharmacy practitioners

OBJECTIVE

To summarize the use of tyrosine kinase inhibitors (TKIs) for treatment of patients with chronic myeloid leukemia (CML) and provide practical information for patient management.

DATA SOURCES

Literature was retrieved from PubMed (2000-January 2011), using the search terms chronic myeloid leukemia and tyrosine kinase inhibitor. Abstracts presented at the 2008-2010 annual meetings of the American Society of Hematology and the American Society of Clinical Oncology, reference citations from identified publications, as well as the manufacturers' full prescribing information for cited drugs, also were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Articles evaluating the efficacy and safety of the TKIs imatinib, nilotinib, and dasatinib were evaluated. Focus was placed on publications supporting management of patients with CML in the chronic phase. Reports presenting clinical trial information of TKIs in development also were included.

DATA SYNTHESIS

The discovery of targeted tyrosine kinase inhibition of BCR-ABL kinase dramatically changed the treatment of CML. Imatinib, the first TKI approved for treatment of patients with Philadelphia chromosome--positive CML, demonstrated significant superiority over the previous standard of care: interferon plus cytarabine. The newer, more potent TKIs, nilotinib and dasatinib, have demonstrated improved efficacy over imatinib as first-line therapy and provide an effective option for patients with resistance or intolerance to imatinib.

CONCLUSIONS

To maximize efficacy of TKI therapy, close patient management, involving frequent monitoring of patient response, is essential. Given the importance of continuing TKI therapy, early recognition and management of adverse events are critical to optimizing outcomes in patients with CML. In addition to the safety profile and considerations of comorbidities, additional factors can affect therapeutic selection, including drug-drug and drug-food interactions. Research investigating new therapies, particularly for patients harboring the T315I mutation-which remains refractory to current TKIs-continues in the quest to improve outcomes in patients with CML.

Navigating the road toward optimal initial therapy for chronic myeloid leukemia

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) and are now widely accepted as the initial therapy of choice in this disease, supplanting interferon and allogeneic stem cell transplantation. There are currently three drugs approved by the US Food and Drug Administration (FDA) for front-line treatment of CML: imatinib, nilotinib, and dasatinib. A fourth drug, bosutinib, may also win FDA approval in 2011. The goal of this review is to summarize the most recent information on initial treatment of CML and to aid clinicians in managing newly diagnosed CML patients.

RECENT FINDINGS

Phase III studies comparing imatinib with nilotinib or dasatinib in newly diagnosed CML were published in June 2010, leading to accelerated FDA approval for both of these 'second-generation' TKIs for initial therapy of CML. There are significant differences between the agents in terms of frequency and rate of responses, progression-free survival, and side-effects. However, the follow-up period on these trials is short, and there are as yet no significant differences in overall survival. Guidelines for monitoring CML patients on TKI therapy have been recently revised.

SUMMARY

Management of newly diagnosed CML patients in the coming decade will begin to resemble antibiotic treatment of infection, with therapy individualized based on patient risk factors, co-morbidities, and tolerability. In addition, the cost of therapy will emerge as an important consideration as generic imatinib becomes available in 2015. In this context, clinical trials to guide decision-making in newly diagnosed CML patients are needed.

Neferine increases STI571 chemosensitivity via inhibition of P-gp expression in STI571-resistant K562 cells

We investigated the effects of neferine (Nef) on STI571 sensitivity and the possible mechanism in STI571-resistant K562/G01 cells. We observed cell proliferation by the modified MTT (methyl thiazolyl tetrazolium) assay. We determined the intracellular concentration of STI571 in K562/G01 cells by high-performance liquid chromatography (HPLC), the expression of P-glycoprotein (P-gp) by Western blotting, and the expression of MDR-1 mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR). We observed that drug resistance to STI571 for K562/G01 cells was 43.99-fold higher than that for K562 cells. We also observed that a low concentration of Nef (<8 μM) and verapamil hydrochloride (VRP) (<10 μM) showed no direct cytotoxicity but significantly reduced the 50% cell growth inhibitory concentration (IC(50)) values of STI571 in K562/G01 cells. The reverse multiples for 8 μM Nef and 10 μM VRP were approximately two-fold. Both Nef (8 μM) and VRP (10 μM) decreased MDR-1 mRNA and P-gp protein expression and increased intracellular STI57I concentrations significantly in K562/G01 cells. Nef is a candidate chemical that can increase STI571 chemosensitivity in STI571-resistant K562 cells by inhibition of P-gp expression and increasing intracellular STI571 accumulation.