Update on practical aspects of the treatment of chronic myeloid leukemia with imatinib mesylate

A safety evaluation of imatinib mesylate in the treatment of gastrointestinal stromal tumor

INTRODUCTION

For the last 15 years, imatinib mesylate has been the first line treatment of choice for advanced (metastatic) GIST.

AREAS COVERED

This review describes key efficacy data on imatinib for the treatment of GIST, and focuses on safety and tolerability of imatinib, with emphasis on common adverse events management and long term toxicity profile.

EXPERT OPINION

Imatinib has been the standard of care for metastatic GIST and probably will continue to be so for the next few years. Still, despite dramatic responses initially, imatinib drug resistance continues to be the major factor for treatment discontinuation. The toxicity profile of imatinib has been well characterized, and although the majority of patients experience an adverse event during treatment with imatinib, these side effects are usually mild and manageable, with the majority of patients continuing treatment uninterruptedly. Early concerns regarding imatinib related cardiotoxicity in GIST have not been confirmed in large prospective randomized trials, with reports indicating a low incidence of approximately 0.2%-0.4%. Future strategies for treatment of imatinib resistant GIST will probably include novel tyrosine kinase inhibitors, combination therapies or immunotherapy.

Evaluation of deoxyhypusine synthase inhibitors targeting BCR-ABL positive leukemias

Effective inhibition of BCR-ABL tyrosine kinase activity with Imatinib represents a breakthrough in the treatment of patients with chronic myeloid leukemia (CML). However, more than 30 % of patients with CML in chronic phase do not respond adequately to Imatinib and the drug seems not to affect the quiescent pool of BCR-ABL positive leukemic stem and progenitor cells. Therefore, despite encouraging clinical results, Imatinib can still not be considered a curative treatment option in CML. We recently reported downregulation of eukaryotic initiation factor 5A (eIF5A) in Imatinib treated K562 cells. Furthermore, the inhibition of eIF5A by siRNA in combination with Imatinib has been shown to exert synergistic cytotoxic effects on BCR-ABL positive cell lines. Based on the structure of known deoxyhypusine synthase (DHS) inhibitors such as CNI-1493, a drug design approach was applied to develop potential compounds targeting DHS. Here we report the biological evaluation of selected novel (DHSI-15) as compared to established (CNI-1493, deoxyspergualin) DHS inhibitors. We show that upon the compounds tested, DHSI-15 and deoxyspergualin exert strongest antiproliferative effects on BCR-ABL cells including Imatinib resistant mutants. However, this effect did not seem to be restricted to BCR-ABL positive cell lines or primary cells. Both compounds are able to induce apoptosis/necrosis during long term incubation of BCR-ABL positive BA/F3 derivates. Pharmacological synergism can be observed for deoxyspergualin and Imatinib, but not for DHSI-15 and Imatinib. Finally we show that deoxyspergualin is able to inhibit proliferation of CD34+ progenitor cells from CML patients. We conclude that inhibition of deoxyhypusine synthase (DHS) can be supportive for the anti-proliferative treatment of leukemia and merits further investigation including other cancers.