The low frequency of clinical resistance to PDGFR inhibitors in myeloid neoplasms with abnormalities of PDGFRA might be related to the limited repertoire of possible PDGFRA kinase domain mutations in vitro.

Posted by rob on October 26, 2010 under Uncategorized | Comments are off for this article

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The low frequency of clinical resistance to PDGFR inhibitors in myeloid neoplasms with abnormalities of PDGFRA might be related to the limited repertoire of possible PDGFRA kinase domain mutations in vitro.

Oncogene. 2010 Oct 25;

Authors: von Bubnoff N, Gorantla SP, Engh RA, Oliveira TM, Thöne S, Aberg E, Peschel C, Duyster J

Myeloproliferation with prominent eosinophilia is associated with rearrangements of PDGFR-A or -B. The most common rearrangement is FIP1L1-PDGFRA (FP). The majority of patients with PDGFR-rearranged myeloproliferation respond to treatment with imatinib. In contrast to BCR-ABL-positive chronic myelogenous leukemia, only few cases of imatinib resistance and mutations of the FP kinase domain have been described so far. We hypothesized that the number of critical residues mediating imatinib resistance in FP in contrast to BCR-ABL might be limited. We performed an established systematic and comprehensive in vitro resistance screen to determine the pattern and frequency of possible TKI resistance mutations in FP. We identified 27 different FP kinase domain mutations including 25 novel variants, which attenuated response to imatinib, nilotinib or sorafenib. However, the majority of these exchanges did not confer complete inhibitor resistance. At clinically achievable drug concentrations, FP/T674I predominated with imatinib, whereas with nilotinib and sorafenib, FP/D842V and the compound mutation T674I+T874I became prevalent. Our results suggest that the PDGFR kinase domain contains a limited number of residues where exchanges critically interfere with binding of and inhibition by available PDGFR kinase inhibitors at achievable concentrations, which might explain the low frequency of imatinib resistance in this patient population. In addition, these findings would help to select the appropriate second-line drug in cases of imatinib-resistant disease and may be translated to other neoplasms driven by activated forms of PDGFR-A or -B.Oncogene advance online publication, 25 October 2010; doi:10.1038/onc.2010.476.

PMID: 20972453 [PubMed - as supplied by publisher]

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Response to dasatinib in a patient with concomitant chronic myeloid leukemia and chronic lymphocytic leukemia.

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Response to dasatinib in a patient with concomitant chronic myeloid leukemia and chronic lymphocytic leukemia.

Acta Haematol. 2010;124(2):105-9

Authors: Serpa M, Bendit I, Seguro F, Xavier F, Cavalcante M, Steinbaum D, Nardinelli L, Aldred VL, de Paula HM, Dorlhiac-Llacer PE

While chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML) are common diseases in the elderly, they rarely occur simultaneously in the same patient. Here we present the case of a 77-year-old patient diagnosed with CML in the chronic phase who showed an optimal response to 400 mg/day of imatinib. This patient progressed to Binet B-CLL with an 11q22.3 deletion and CD38 positivity in the 4th month of treatment. During the follow-up, his lymphocyte number doubled in <6 months. Based on previous reports, dasatinib was chosen instead of imatinib. After 6 months of treatment with 100 mg/day of dasatinib, the patient demonstrated a partial response, characterized by the regression of lymph node enlargement, a hemoglobin level of 10.7 g/dl, neutrophils of 1.7 × 10(9)/l, a 82% reduction in the lymphocyte number and an increase in cytotoxic CD8+ and large granular lymphocytes. This partial response has persisted to the present time. While little data have been published regarding the in vitro effect of dasatinib monotherapy for CLL, this case report provides some evidence of the clinical activity of dasatinib in CLL.

PMID: 20720403 [PubMed - indexed for MEDLINE]

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