Direct effect of dasatinib on proliferation and cytotoxicity of natural killer cells in in vitro study

Lymphocytosis predominantly due to natural killer (NK) cells has been reported in nearly a half of chronic myelogenous leukemia (CML) patients who were being treated with dasatinib. Besides, dasatinib‐treated patients with lymphocytosis have a better prognosis than patients without lymphocytosis. In order to elucidate the effects of dasatinib on the proliferation of lymphocyte subset, dasatinib was added to the culture of peripheral blood mononuclear cells with IL‐2 (lymphokine‐activated killer culture) or a low dose of IL‐2 with zoledronate (γδ T‐cell culture). In both culture conditions, NK cells were increased in both percentage and absolute number in the culture with dasatinib compared with control culture without dasatinib. The increase of NK cells was dose dependent of dasatinib in the range of 2–25 nM. NK cell cytotoxicity of cultured cells with dasatinib was demonstrated to be superior to control cells without dasatinib in cytotoxicity assay using EGFP‐transfected K562 cells as target cells. The present study suggested that lymphocytosis in dasatinib‐treated CML patients is at least partly associated with a direct effect of dasatinib to stimulate the proliferation of NK cells. Favourable prognosis in patients with dasatinib‐induced lymphocytosis might be associated with the effects of dasatinib to potentiate NK cytotoxicity in vivo. Copyright © 2012 John Wiley & Sons, Ltd.     

Complete Cytogenetic Response and Major Molecular Response as Surrogate Outcomes for Overall Survival in First-Line Treatment of Chronic Myelogenous Leukemia: A Case Study for Technology Appraisal on the Basis of Surrogate Outcomes Evidence

ObjectivesIn 2012, the National Institute for Health and Care Excellence assessed dasatinib, nilotinib, and standard-dose imatinib as first-line treatment of chronic phase chronic myelogenous leukemia (CML). Licensing of these alternative treatments was based on randomized controlled trials assessing complete cytogenetic response (CCyR) and major molecular response (MMR) at 12 months as primary end points. We use this case study to illustrate the validation of CCyR and MMR as surrogate outcomes for overall survival in CML and how this evidence was used to inform National Institute for Health and Care Excellence’s recommendation on the public funding of these first-line treatments for CML.MethodsWe undertook a systematic review and meta-analysis to quantify the association between CCyR and MMR at 12 months and overall survival in patients with chronic phase CML. We estimated life expectancy by extrapolating long-term survival from the weighted overall survival stratified according to the achievement of CCyR and MMR.ResultsFive studies provided data on the observational association between CCyR or MMR and overall survival. Based on the pooled association between CCyR and MMR and overall survival, our modeling showed comparable predicted mean duration of survival (21–23 years) following first-line treatment with imatinib, dasatinib, or nilotinib.ConclusionsThis case study illustrates the consideration of surrogate outcome evidence in health technology assessment. Although it is often recommended that the acceptance of surrogate outcomes be based on randomized controlled trial data demonstrating an association between the treatment effect on both the surrogate outcome and the final outcome, this case study shows that policymakers may be willing to accept a lower level of evidence (i.e., observational association).     

Tyrosine kinase inhibitors for the treatment of Philadelphia chromosome-positive adult acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a heterogeneous disorder, with the greatest prevalence in children, but it also affects adults, and has an increasing incidence with age. Chromosomal abnormalities in ALL have been frequently described, the most common is the Philadelphia chromosome (Ph). The resulting fusion gene, BCR-ABL1, encodes for a chimerical oncoprotein (BCR-ABL) with constitutive tyrosine kinase activity, which leads to uncontrolled cell proliferation, reduced apoptosis, and impaired cell adhesion. Treating Philadelphia chromosome-positive (Ph+) ALL patients with conventional chemotherapy has not substantially improved their long-term outcomes. Recently, however, BCR-ABL-targeted strategies have been successfully adopted. Imatinib is an oral competitive inhibitor of ABL with demonstrated phase 2 efficacy in patients with treatment-naive and pretreated ALL. Despite its efficacy, imatinib may induce specific resistance in a large proportion of patients, mainly because of the occurrence of ABL1 mutations. Therefore, novel inhibitors have been developed. Dasatinib is a multitargeted kinase inhibitor of BCR-ABL, SRC, C-KIT, PDGFRs, and ephrin A receptor kinases. Unlike imatinib, it binds both the active and inactive BCR-ABL as well as the majority of ABL mutants. Dasatinib is approved for treatment of imatinib-pretreated Ph+ ALL, and chronic myeloid leukemia (CML) on the basis of phase 2 trials that demonstrated impressive efficacy and favorable tolerability profiles. Nilotinib is another BCR-ABL targeted agent that is similar in structure to imatinib but has significantly greater binding affinity. It also has demonstrated promising efficacy in Ph+ ALL but is still being evaluated in phase 2 trials. In this article, the authors reviewed current knowledge on novel tyrosine-kinase inhibitors in adult Ph+ ALL patients.     

In vitro sensitivity to dasatinib in lymphoblasts from a patient with t(17;19)(q22;p13) gene rearrangement pre-B acute lymphoblastic leukemia

Patients with t(17;19) acute lymphoblastic leukemia (ALL) have a dismal prognosis even with the most intensive current therapies that include stem cell transplant. We present the case of a patient with t(17;19)(q22;p13) gene rearranged B-cell precursor ALL whose lymphoblasts were found to have significant in vitro sensitivity to dasatinib. The patient tolerated the addition of dasatinib with combination therapy and remained in remission for over nine months until his recurrence. Therefore, future studies will be needed to interrogate whether dasatinib has any therapeutic benefit in children with t(17;19) B-cell precursor ALL.     

A deuterated analog of dasatinib disrupts cell cycle progression and displays anti-non-small cell lung cancer activity in vitro and in vivo

The pan-Src family kinase inhibitor dasatinib has been approved for chronic myeloid leukemia treatment but displays limited activity in lung cancer patients. In this study, we used a deuterium substitution strategy to develop a class of novel chemicals based on dasatinib and found that these compounds maintain inhibition on c-Src activity and display anti-non-small cell lung cancer activity in vitro and in vivo. BRP800, one of these compounds, was chosen for further studies. BRP800 mainly displayed antiproliferative but not proapoptotic activity. Molecularly, BRP800 did not show significant effects on the expression of antiapoptotic genes, such as Bcl-2 and Mcl1, or on the activation of apoptotic enzymes, such as caspase-3, -8 or 9. However, BRP800 decreased expression of cell cycle promoting genes such as cyclins D1, D3, E, A and CDK4 and 6, and increased the expression of cell cycle negative regulators including p21, p27 and p53. Consistent with these findings, BRP800 arrested cells at the G0/G1 phase in a concentration-dependent manner, and the G0/G1 fraction was increased from 64% in control to 85% in BRP800-treated cells. We also evaluated the effects of BRP800 on NSCLC xenografts using H460 as a model in nude mice. Compared with the known NSCLC drug docetaxel, BRP800 displayed potent and similar antitumor activity but with less toxicity. These findings suggest that the deuterated analog of dasatinib is antiproliferative by inhibiting c-Src and disrupting cell cycle progression, and could be further developed as a novel drug for non-small lung cancer treatment.     

Targeting tyrosine-kinases and estrogen receptor abrogates resistance to endocrine therapy in breast cancer

Despite numerous therapies that effectively inhibit estrogen signaling in breast cancer, a significant proportion of patients with estrogen receptor (ER)-positive malignancy will succumb to their disease. Herein we demonstrate that long-term estrogen deprivation (LTED) therapy among ER-positive breast cancer cells results in the adaptive increase in ER expression and subsequent activation of multiple tyrosine kinases. Combination therapy with the ER down-regulator fulvestrant and dasatinib, a broad kinase inhibitor, exhibits synergistic activity against LTED cells, by reduction of cell proliferation, cell survival, cell invasion and mammary acinar formation. Screening kinase phosphorylation using protein arrays and functional proteomic analysis demonstrates that the combination of fulvestrant and dasatinib inhibits multiple tyrosine kinases and cancer-related pathways that are constitutively activated in LTED cells. Because LTED cells display increased insulin receptor (InsR)/insulin-like growth factor 1 receptor (IGF-1R) signaling, we added an ant-IGF-1 antibody to the combination with fulvestrant and dasatinib in an effort to further increase the inhibition. However, adding MK0646 only modestly increased the inhibition of cell growth in monolayer culture, but neither suppressed acinar formation nor inhibited cell migration in vitro and invasion in vivo. Therefore, combinations of fulvestrant and dasatinib, but not MK0646, may benefit patients with tyrosine-kinase-activated, endocrine therapy-resistant breast cancer.     

Treatment-free remission after dasatinib in patients with chronic myeloid leukaemia in chronic phase with deep molecular response: Final 5-year analysis of DASFREE

Patients with chronic myeloid leukaemia in chronic phase (CML-CP) who have a sustained deep molecular response (DMR) are eligible to discontinue treatment and attempt treatment-free remission (TFR). In the DASFREE study ( ClinicalTrials.gov ; NCT01850004), the 2-year TFR rate after dasatinib discontinuation was 46%; here we present the 5-year update. Patients with a stable DMR after ≥2 years of dasatinib therapy discontinued treatment and were followed for 5 years. At a minimum follow-up of 60 months, in 84 patients discontinuing dasatinib, the 5-year TFR rate was 44% (n = 37). No relapses occurred after month 39 and all evaluable patients who relapsed and restarted dasatinib (n = 46) regained a major molecular response in a median of 1.9 months. The most common adverse event during the off-treatment period was arthralgia (18%, 15/84); a total of 15 withdrawal events were reported in nine patients (11%). At the 5-year final follow-up, almost half of the patients who discontinued dasatinib after a sustained DMR maintained TFR. All evaluable patients who experienced a relapse quickly regained a DMR after restarting dasatinib, demonstrating that dasatinib discontinuation is a viable and potentially long-term option in patients with CML-CP. The safety profile is consistent with the previous report.     

Dasatinib as an investigational drug for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults

Introduction: Acute lymphoblastic leukemia (ALL) with BCR-ABL1 translocation is an aggressive malignancy that is usually treated with intensive chemotherapy with the possibility of allogeneic stem cell transplantation. The encoded fusion protein may be important for leukemogenesis; clinical studies show that dasatinib has an antileukemic effect in combination with steroids alone or intensive chemotherapy.

Areas covered: Relevant publications were identified through literature searches (the used terms being acute lymphoblastic leukemia plus dasatinib) in the PubMed database. We searched for original articles and reviews describing the pharmacology and clinical use of dasatinib in ALL with BCR-ABL1. The mechanism of action, pharmacology and clinical study findings are examined.

Expert opinion: Dasatinib is associated with a high complete remission rate in ALL when used alone and in combination with steroids or intensive chemotherapy. However, mutations at T315 and F317 are associated with dasatinib resistance. Overall toxicity has been acceptable in these studies and no unexpected toxicity was observed. It is not known whether the antileukemic effect of dasatinib differs between subsets of BCR-ABL1⁺ patients or is attributed to inhibition of the fusion protein alone, or a combined effect on several kinases, and whether dasatinib-containing combination treatment should be preferred in these patients instead of other emerging strategies, e.g. monoclonal antibodies.