Specific Inhibitor Of BCR-ABL Tyrosine Kinase Research Articles

Synthesis and antileukemic activity of an ursolic acid derivative: A potential co-drug in combination with imatinib

Imatinib, a specific Bcr-Abl tyrosine kinase inhibitor, is the most commonly used drug in the treatment of chronic myeloid leukemia. However, optimal response is not achieved in up to 33% of patients. Therefore, development of novel therapeutic strategies for chronic myeloid leukemia is critical. Betulinic (1) and ursolic (2) acids are natural pentacyclic triterpenes that exhibit antileukemic activities. In this study, we evaluated the effects of pharmacomodulations at the C-3 position of the triterpene moiety of betulinic and ursolic acids on their activity against K562 leukemia cells. Six new derivatives (1a-2c) were synthesized and evaluated for pro-apoptotic and anti-proliferative effects in mammalian and leukemic cells. 2c derivative containing an amine group at the C-3 position of ursolic acid was the most active against leukemia cells with an IC50 value of 5.2 μM after 48 h of treatment. 2c did not exhibit cytotoxic effects against VERO and HepG2 cells and human lymphocytes, showing a good selectivity index for cancer over normal cells. Induced cell death by apoptosis via caspases 3 and 8, and also caused cell cycle arrest as evidenced by accumulation of cells in the G1 phase and decreased cell population in the G2 phase. Furthermore, co-treatment of 2c with imatinib, the chemotherapy drug most commonly used to treat leukemia, resulted in a synergistic effect. Our findings provide a strong rationale for further investigation of combination therapy using the 2c derivative and imatinib in pre-clinical studies.

Activity of the Histone Deacetylase Inhibitor, Vorinostat, Against BCR-ABL Positive Leukemia Cells with Random Mutagenesis and In Combination with Nilotinib

AbstractAbstract 4460The clinical use of imatinib, a specific BCR-ABL tyrosine kinase inhibitor (TKI) is effective in inducing a complete hematological and cytogenetic remission in a high percentage of chronic myeloid leukemia (CML) and Philadelphia chromosome (Ph) positive acute lymphoblastic leukemia (ALL) patients. However, imatinib does not efficiently kill leukemic stem cells and is limited by the emergence of resistance due to the point mutations in the BCR-ABL kinase domain. Histone acetyltransferases (HAT) and histone deacetylases (HDAC) control the acetylation of histones and intracellular proteins, and regulate the transcription and function of the proteins. HDAC inhibitor is a structurally diverse class of targeted anti-cancer agent. One of the pan-HDAC inhibitor, vorinostat (suberoylanilide hydroxamic acid: SAHA) is a small-molecule inhibitor of most human class I and class II HDAC, and is reported the efficacy of malignant cells including lymphomas and myeloid malignancies.Therefore, combination therapy using a BCR-ABL tyrosine kinase inhibitor and an HDAC inhibitor, vorinostat may help prevent CML relapse due to BCR-ABL point mutation and may improve their long-term outcome. In this study, we investigated the efficacy of vorinostat by using the Ph-positive leukemia cell line, K562 and Ba/F3 BCR-ABL cell in a random mutagenesis study for BCR-ABL mutation. We first performed a comprehensive drug combination experiment using vorinostat and BCR-ABL tyrosine kinase inhibitor, imatinib or nilotinib. The treatment of imatinib or nilotinib exhibits cell growth inhibition partially against Ba/F3 BCR-ABL cell in a random mutagenesis. We also found the BCR-ABL point mutation such as T315I or M344V after 2 weeks nilotinib treatment by direct sequence analysis. We show that vorinostat potently induced cell growth inhibition of K562 and Ba/F3 BCR-ABL cells in a random mutagenesis in a dose dependent manner. Combined treatment of Ba/F3 BCR-ABL cell in a random mutagenesis with vorinostat and nilotinib or imatinib caused significantly more cytotoxicity than each drug alone by colony assay. We investigated the intracellular signaling of vorinostat. Phosphorylation of BCR-ABL, Crk-L were reduced after vorinostat treatment for 24 hours in a dose dependent manner. Caspase 3 and poly (ADP-ribose) polymerase (PARP) activation were increased after vorinostat treatment. Vorinostat potently enhanced cell growth inhibition of Ba/F3 BCR-ABL point mutants (G250E, Q252H, Y253F, E255K, M294V, T315I, T315A, F317L, F317V, M351T and H396P) compared with Ba/F3 expressing Wt BCR-ABL cells. The protein level of BCR-ABL was reduced after vorinostat treatment. BCR-ABL degradations in BCR-ABL mutant cells were significantly enhanced compared with Ba/F3 Wt BCR-ABL cells. Although long term culture of Ba/F3 BCR-ABL cell in a random mutagenesis with 2μ M vorinostat significantly decreased cell growth, the cells were increased after removal of vorinostat. We found these cells were wild type BCR-ABL by direct sequence analysis. Data from this study suggested that administration of the vorinostat may mediate its effects on BCR-ABL positive cells included BCR-ABL point mutation and enhance cytotoxic effects of nilotinib or imatinib in BCR-ABL mutant cells, and provide information of potential therapeutic relevance. Disclosures:Ohyashiki:Nippon Shinyaku Co., Ltd.: Research Funding.

Chronic Myeloid Leukemia and Second-Generation Tyrosine Kinase Inhibitors: When, How, and Which One?

Chronic myeloid leukemia (CML) is a progressive and often fatal myeloproliferative disorder. The introduction of imatinib, a tyrosine kinase inhibitor (TKI) specific for BCR-ABL, was a major breakthrough in CML therapy. Although most patients respond to first-line imatinib therapy, some experience a loss of response (resistance) or require treatment discontinuation due to toxicity (intolerance). For patients who fail with standard-dose imatinib therapy, imatinib dose escalation is a second-line option. However, high-dose imatinib is not an appropriate approach for patients experiencing drug toxicity, and there remain questions over the durability of responses achieved with this strategy. Alternative second-line options include the newer TKIs dasatinib and nilotinib. A substantial amount of long-term data for these agents is available. Although both are potent and specific BCR-ABL TKIs, dasatinib and nilotinib exhibit unique pharmacological profiles and response patterns relative to different patient characteristics, such as disease stage and BCR-ABL mutational status. To optimize therapeutic benefit, clinicians should select treatment based on each patient's historical response, adverse-event tolerance level, and risk factors.

Clinical algorithms for the treatment of patients with chronic myeloid leukemia: the 2010 perspective.

Chronic myeloid leukemia (CML) is a progressive and often fatal myeloproliferative disorder. The hallmark of CML is an acquired chromosomal translocation known as the Philadelphia chromosome (Ph) that results in the synthesis of the BCR-ABL fusion protein, a constitutively active tyrosine kinase (TK). The introduction of imatinib, a TK inhibitor (TKI) specific for BCR-ABL, was a major breakthrough in CML therapy. Although most patients respond to first-line imatinib therapy, some experience a loss of response (resistance) or require treatment discontinuation because of toxicity (intolerance). In patients for whom standard-dose imatinib therapy (400 mg/day) fails, imatinib dose escalation (600-800 mg/day) is a second-line option. However, high-dose imatinib is not an appropriate approach for patients experiencing drug toxicity, and there remain questions over the durability of responses achieved with this strategy. Alternative second-line options include the newer TKIs dasatinib and nilotinib. A substantial amount of long-term data for these agents is available. Although both are potent and specific BCR-ABL TKIs, dasatinib and nilotinib exhibit unique pharmacologic profiles and response patterns relative to different patient characteristics, such as disease stage and BCR-ABL mutational status. To optimize therapeutic benefit, clinicians should select treatment based on each patient's historical response, adverse event tolerance level, and risk factors.

Nilotinib in Patients (pts) with Philadelphia Chromosome-Positive (Ph+) Chronic Myelogenous Leukemia in Blast Crisis (CML-BC) Who Are Resistant or Intolerant to Imatinib.

Background: Nilotinib is a novel orally active aminopyrimidine. It is a highly specific Bcr-Abl tyrosine kinase inhibitor (TKI) 30-fold more potent than imatinib. Based on the efficacy and favorable tolerability demonstrated by nilotinib in the phase I study, this phase II open-label study was designed to evaluate the safety and efficacy of nilotinib in adult pts with Ph+ chronic myeloid leukemia in blast crisis (CML-BC) resistant to or intolerant of imatinib. The prognosis for these pts remains poor.Methods: The primary endpoint was confirmed hematologic response (HR). Imatinib resistance was defined as either treatment with imatinib >600 mg/day with disease progression, no HR in bone marrow after 4 weeks, or pts receiving <600 mg/day with mutations in any of the following amino acids: L248, G250, Q252, Y253, E255, T315, F317, or H396. Imatinib intolerance was defined as grade 3/4 adverse events, or grade 2 events persisting for >1 month while on imatinib. Nilotinib therapy was commenced at 400 mg twice daily (BID) with escalation to 600 mg BID for pts who had inadequate responses and no safety concerns.Results: Safety and efficacy data are reported for 135 BC (myeloid, n=103; lymphoid, n=29; unknown, n=3). The median age was 55 (18–79) years, the median time since CML diagnosis was 1.6 (<1–73) months, and 61.5% were men. 82% of the patients were imatinib-resistant and 18% were intolerant. Treatment with nilotinib is ongoing for 16 (12%) pts. The median treatment duration was 84 (3–485) days and the median average dose intensity was 800 mg/day. 119 (88%) pts discontinued treatment, of which 71 (53%) discontinued due to disease progression; 13 (10%) discontinued due to AEs. 38% of pts had >/=95% Ph+ metaphases at study entry. Chromosomal abnormalities other than Ph+ were also noted in 54% of pts at study entry. Extramedullary involvement was present in 39% of the pts. The most common Grade 3/4 hematologic laboratory abnormalities were neutropenia (67%), thrombocytopenia (62%), anemia (42%). The most common Grade 3/4 non- hematologic AEs were as follows: pneumonia (11%), pyrexia (7%), nausea (4%), diarrhea (4%), and asthenia (4%).Conclusions: Based on the CHR rates achieved in this very advanced patient population, nilotinib monotherapy appears to have clinical activity in pts with imatinib-resistant CML BC. Overall nilotinib is well tolerated in this patient population with advanced disease and with non-heme toxicity comparable to that observed for pts with CML-CP. The hematological responses were similar between myeloid and lymphoid Ph+ CML blast crises.Response for Patients With CML-BC With at Least 6 Months of Follow-upMyeloid (N = 103) n (%)Lymphoid (N = 29) n (%)Hematologic response40 (39)11 (38)CHR25 (24)8 (28)Marrow response5 (5)1 (3)Return to chronic phase10 (10)2 (7)SD31 (30)7 (24)PD18 (17)6 (21)Not evaluable5 (5)1 (3)Missing9 (9)4 (14)

Synergy between imatinib and mycophenolic acid in inducing apoptosis in cell lines expressing Bcr-Abl

AbstractBcr-Abl tyrosine kinase activity initiates a number of intracellular signaling cascades that result in leukemogenesis. Imatinib mesylate, a specific Bcr-Abl tyrosine kinase inhibitor, has been highly successful in the treatment of chronic myelogenous leukemia (CML). However, the emergence of imatinib resistance and the incomplete molecular response of a significant number of patients receiving this therapy have led to a search for combinations of drugs that will enhance the efficacy of imatinib. We have demonstrated that mycophenolic acid (MPA), a specific inosine monophosphate dehydrogenase (IMPDH) inhibitor that results in depletion of intracellular guanine nucleotides, is synergistic with imatinib in inducing apoptosis in Bcr-Abl-expressing cell lines. Studies of signaling pathways downstream of Bcr-Abl demonstrated that the addition of MPA to imatinib reduced the phosphorylation of both Stat5 and Lyn, a Src kinase family member. The phosphorylation of S6 ribosomal protein was also greatly reduced. These results demonstrate that inhibitors of guanine nucleotide biosynthesis may synergize with imatinib in reducing the levels of minimal residual disease in CML and lay the foundation for clinical trials in which IMPDH inhibitors are added to imatinib in patients who have suboptimal molecular responses to single agent therapy or who have progressive disease. (Blood. 2005; 105:3270-3277)