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At least 739 records · Page 41Linked to original sources
PubMed2004

Prediction of resistance to small molecule FLT3 inhibitors: implications for molecularly targeted therapy of acute leukemia.

Mutations in the receptor tyrosine kinase FLT3 occur frequently in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Small molecules that selectively inhibit FLT3 kinase activity induce apoptosis in blasts from AML patients with FLT3 mutations and prolong survival in animal models of FLT3-induced myeloproliferative disease. A spectrum of structurally different small molecules with activity against FLT3 have been described, and their efficacy for treatment of AML and ALL is now being investigated in clinical trials. Here, we describe the results of an in vitro screen designed to identify mutations in the ATP-binding pocket of FLT3 that confer resistance to tyrosine kinase inhibitors. Mutations at four different positions (Ala-627, Asn-676, Phe-691, and Gly-697) were identified that confer varying degrees of resistance to PKC412, SU5614, or K-252a. FLT3 proteins mutated at Ala-627, Asn-676, or Phe-691 remained sensitive to higher concentrations of the inhibitors, but the G697R mutation conferred high-level resistance to each of these inhibitors as well as to six additional experimental inhibitors. These data provide insights into potential mechanisms of acquired resistance of FLT3 to small molecule inhibitors and indicate that the G697R mutation may be a clinically problematic resistance mutation that warrants proactive screening for additional inhibitors.

Acute Disease↗
PubMed2004

HER2-targeted therapy reduces incidence and progression of midlife mammary tumors in female murine mammary tumor virus huHER2-transgenic mice.

PURPOSE: This study examined the effectiveness of early and prolonged mu4D5 (the murine form of trastuzumab/Herceptin) treatment in transgenic mice that overexpress human HER2 (huHER2), under the murine mammary tumor virus promoter, as a model of huHER2-overexpressing breast cancer. EXPERIMENTAL DESIGN: Mice were randomly assigned to one of three treatment groups and received i.p. injections from 17 weeks of age until either 52 weeks of age or morbidity. Fourteen mice received 100 mg/kg mu4D5, 14 mice received 100 mg/kg antiherpes simplex virus glycoprotein D control antibody, and 11 mice received a diluent control. RESULTS: High levels of huHER2 expression were detectable in mammary glands of young virgin founder mice. Mammary adenocarcinomas were frequently found in female founders and progeny at an average age of 28 weeks, with some progressing to metastatic disease. The incidence of mammary tumors was significantly reduced, and tumor growth inhibition was observed in mice receiving mu4D5 compared with control mice. In addition, Harderian gland neoplasms, highly associated with overexpression of huHER2 in this transgenic line, were entirely absent in the mu4D5 treatment group, indicating down-regulation of huHER2 in vivo activity. CONCLUSIONS: Early intervention with mu4D5 was of benefit in our transgenic mice at high risk for developing huHER2-overexpressing breast cancer. This study suggests a potential benefit of early treatment with Herceptin in HER2-positive primary breast cancer.

Animals↗
PubMed2006

Targeted therapy for glioblastoma multiforme neoplastic meningitis with intrathecal delivery of an oncolytic recombinant poliovirus.

PURPOSE: The toxicity and antitumor activity of regional intrathecal delivery of an oncolytic recombinant poliovirus, PVS-RIPO, was evaluated in rodent models of glioblastoma multiforme neoplastic meningitis. EXPERIMENTAL DESIGN: To evaluate for toxicity, PVS-RIPO was administered into the spinal cord of transgenic mice that express the human poliovirus receptor, CD155, and into the intrathecal space of athymic rats without tumor. To evaluate efficacy, two different doses of PVS-RIPO were administered intrathecally 3 days after athymic rats were inoculated intrathecally with an aggressive human glioblastoma multiforme xenograft. RESULTS: No clinical or histologic evidence of toxicity was found. In efficacy studies, median survival was increased by 174.47% from 8.5 days in the group treated with UV light-inactivated virus to 15 days in the rats treated with 1.0 x 10(7) plaque-forming units (pfu) of PVS-RIPO (P < 0.0001). A similar increase in median survival was seen in the group receiving 1.0 x 10(9) pfu PVS-RIPO (P < 0.0001); however, there was no statistically significant dose-response relationship (P = 0.345). In addition, 1 of 10 rats in lower-dose PVS-RIPO-treated group and 3 of 10 rats in higher-dose PVS-RIPO-treated group survived >60 days after tumor cell inoculation and had no evidence of residual tumor at autopsy. CONCLUSION: These results suggest that intrathecal treatment with PVS-RIPO may be useful for treatment of neoplastic meningitis in patients with glioblastoma multiforme and provides a rationale for clinical trials in this area.

Animals↗
PubMed2006

Targeted therapy with antineoplastons A10 and AS2-1 of high-grade, recurrent, and progressive brainstem glioma.

BACKGROUND: Brainstem glioma carries the worst prognosis of all malignancies of the brain. Most patients with brainstem glioma fail standard radiation therapy and chemotherapy and do not survive longer than 2 years. Treatment is even more challenging when an inoperable tumor is of high-grade pathology (HBSG). The objective of this report is to summarize the outcome of patients with HBSG treated with antineoplastons in 4 phase 2 trials. PATIENTS: The following group of 18 patients was evaluable: 4 patients with glioblastomas and 14 patients with anaplastic HBSG. Fourteen patients had diffuse intrinsic tumors. Twelve patients suffered from recurrence, and 6 patients did not have radiation therapy or chemotherapy. METHODS: Antineoplastons, which consist of antineoplaston A10 (A10I) and AS2-1 injections, were given in escalating doses by intravenous injections. The median duration of antineoplaston administration was 5 months, and the average dosage of A10I was 9.22 g/kg/d and of AS2-1 was 0.31 g/kg/d. Responses were assessed by gadolinium-enhanced magnetic resonance imaging and positron emission tomography. RESULTS: The overall survival at 2 and 5 years was 39% and 22%, respectively, and maximum survival was more than 17 years for a patient with anaplastic astrocytoma and more than 5 years for a patient with glioblastoma. Progression-free survival at 6 months was 39%. Complete response was achieved in 11%, partial response in 11%, stable disease in 39%, and progressive disease in 39% of patients. Antineoplastons were tolerated very well with 1 case of grade 4 toxicity (reversible anemia). CONCLUSION: Antineoplastons contributed to more than a 5-year survival in recurrent diffuse intrinsic glioblastomas and anaplastic astrocytomas of the brainstem in a small group of patients.

Adolescent↗
PubMed2005

The MLL partial tandem duplication: evidence for recessive gain-of-function in acute myeloid leukemia identifies a novel patient subgroup for molecular-targeted therapy.

MLL (ALL-1) chimeric fusions and MLL partial tandem duplications (PTD) may have mechanistically distinct contributions to leukemogenesis. Acute myeloid leukemia (AML) blasts with the t(9;11)(p22; q23) express MLL-AF9 and MLL wild-type (WT) transcripts, while normal karyotype AML blasts with the MLL(PTD/WT) genotype express MLL PTD but not the MLL WT. Silencing of MLL WT in MLL(PTD/WT) blasts was reversed by DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors, and MLL WT induction was associated with selective sensitivity to cell death. Reduction of MLL PTD expression induced MLL WT and reduced blast colony-forming units, supporting opposing functions for MLL PTD and MLL WT whereby the MLL PTD contributes to the leukemic phenotype via a recessive gain-of-function. The coincident suppression of the MLL WT allele with the expression of the MLL PTD allele, along with the functional data presented here, supports the hypothesis that loss of WT MLL function via monoallelic repression contributes to the leukemic phenotype by the remaining mutant allele. These data from primary AML and the pharmacologic reversal of MLL WT silencing associated with a favorable alteration in the threshold for apoptosis suggest that these patients with poor prognosis may benefit from demethylating or histone deacetylase inhibitor therapy, or both.

Acute Disease↗
PubMed2004

B lymphocytes in systemic lupus erythematosus: lessons from therapy targeting B cells.

Systemic lupus erythematosus (SLE) is a complex disease characterized by numerous autoantibodies and clinical involvement in multiple organ systems. Autoantibodies are usually present in serum for years before the onset of clinical disease. Autoimmunity begins with a limited number of autoantibodies and evolves to become progressively more diverse. Eventually clinical disease ensues. The immunological events triggering the onset of clinical manifestations have not yet been defined. While undoubtedly T cells and dendritic cells appear to play major roles in SLE, a central role for B cells in the pathogenesis of this disease has been brought to the fore in the last few years by work performed both in mice and humans by multiple laboratories. As a result, there is little doubt about the importance of B cells in the development of SLE. Yet much remains to be learned about their role in the ongoing disease process and the merit of targeting B cells for the treatment of SLE. This article will review the role of B cells in human SLE as well as the currently available data on the treatment of SLE by depleting B cells with anti-CD20 (rituximab).

Antibodies, Monoclonal↗
PubMed2003

The phase III trial in the era of targeted therapy: unraveling the "go or no go" decision.

PURPOSE: To review characteristics of contemporary phase III oncology trials and create an explicit framework to help clinical researchers prioritize novel therapies for phase III testing. METHODS: We searched the MEDLINE and EMBASE databases for all reviews of phase III trials; cataloged all phase III trials in two national clinical trial databases; and reviewed approval criteria of recently approved oncology drugs from public data provided by the US Food and Drug Administration. Industry data not available elsewhere in the medical literature were obtained from a sourcebook published by a large contract research organization. RESULTS: Phase III oncology trials are the most expensive and time-consuming aspect of the drug development process. The results of these trials continue to exert the greatest influence on the treatment decision of oncologists and remain pivotal to the granting of drug approval. Making optimal decisions about which agents to advance to phase III testing may decrease the overall cost of cancer drug development and limit the number of patients exposed to ineffective drugs. A conceptual decision model for prioritizing novel therapies for phase III testing is presented. CONCLUSION: Cancer drug development has become more complex and expensive, whereas overall clinical progress remains slow. The transition from phase II to phase III requires a strategic decision that is based on new considerations. A greater investment in phase I and II drug trials may be required to provide the information necessary for phase III planning.

Antineoplastic Agents↗