A 80426 mesylate

A-80426 is a potent and selective α2-adrenoceptor antagonist, it can block serotonin uptake and have putative antidepressant-like effects. It inhibits synaptosomal serotonin (5HT) uptake with an IC50 value of 13 nM and blocks [3H]-paroxetine binding to 5HT uptake sites with a Ki value of 3.8 nM. It inhibits [3H]-rauwolscine binding to α2-adrenoceptors with a Ki value of 2.0 nM, and blocks α2-adrenoceptors with a pEC30 of 7.4-7.5 in electrically stimulated rat vas deferens and atria [1].

α2-adrenoceptors mediate many physiological actions of endogenous noradrenaline and catecholamines adrenaline [2].

In radioligand binding assays with isolated tissues, the potent blocking activity of A-80426 against α2-adrenoceptor is not reflected [1].

P-chloroamphetamine (PCA)-induced hyperactivity is a measure of the blockade of serotonin uptake in vivo. In rats, p-chloroamphetamine (PCA)-induced hyperactivity was significantly reduced by A-80426 at doses of chronic (14 days) (ED50=4.1 ?mol/kg, po) and acute (ED50= 13 ?mol/kg, po). Administration (po) of A-80426 at doses of 6.7 and 22?mol/kg was effective for at least 12 h. Doses of 6.7 to 224?mol/kg, ip, of A-80426 failed to block hypoactivity and hypothermia resulted from the administration of α2-adrenoceptor agonist clonidine. Doses of 100 and 300 ?mol/kg, po, were required to block the mydriasis induced by clonidine [3].

References:
[1].  Hancock AA, Buckner SA, Oheim KW, et al. A-80426, a potent α2-adrenoceptor antagonist with serotonin uptake blocking activity and putative antidepressant-like effects: I. Biochemical profile. Drug Development Research, 1995, 35(4): 237-245.
[2].  Aantaa R, Marjam?ki A and Scheinin M. Molecular Pharmacology of α2-adrenoceptor Subtypes. Annals of Medicine, 1995, 27(4): 439-449.
[3].  Giardina WJ, Buckner SA, Brune ME, et al. A-80426, A Potent and Selective α2-Adrenoceptor Antagonist With Serotonin Uptake-Blocking Activity and Putative Antidepressant-Like Effects: II. Pharmacology Profile. Drug Development Research, 1995, 35(4): 246-260.

Treating Philadelphia chromosome/BCR-ABL1 positive patients with Glivec (Imatinib mesylate): 10 years' experience at Patan Hospital, Nepal.[Pubmed:28369812]

Br J Haematol. 2017 Jun;177(6):991-999.

The Glivec International Patient Assistance Programme makes Glivec (Imatinib mesylate) available to Philadelphia chromosome/BCR-ABL1 positive patients with chronic myeloid leukaemia (CML) in Lower and Middle Income Countries (LMIC). We have established a large cohort of 211 CML patients who are eligible for Imatinib, in Kathmandu, Nepal. Thirty-one patients were lost to follow-up. We report on 180 CML patients with a median age of 38 years (range 9-81). Of these 180 patients, 162 underwent cytogenetic testing and 110 were investigated by reverse transcription polymerase chain reaction. One hundred and thirty-nine of the 180 patients (77.2%) had at least one optimal response. Taken together, our cohort has a 95% overall survival rate and 78% of the patients were still taking Glivec at a median time of 48.8 months (range 3-140 months). The number of patients who actually failed therapy, as defined by the LeukaemiaNet 2013 criteria, was 39 (21.7%). While our cohort has some differences with those in North America or Europe, we have shown Glivec is effective in inducing an optimal response in our patients in Nepal and that it is possible to deliver a clinical service for CML patients using tyrosine kinase inhibitors in resource-poor settings.

Sab mediates mitochondrial dysfunction involved in imatinib mesylate-induced cardiotoxicity.[Pubmed:28315715]

Toxicology. 2017 May 1;382:24-35.

Imatinib mesylate is an effective treatment for chronic myelogenous leukemia and gastrointestinal stromal tumors. Although imatinib mesylate is highly tolerable, it has been implicated in severe congestive heart failure in mouse models and patients. A hallmark of imatinib mesylate-induced cardiotoxicity is mitochondrial dysfunction. The mitochondrial scaffold Sab has been implicated in facilitating signaling responsible for mitochondrial dysfunction in a c-Jun N-terminal Kinase (JNK)-dependent manner. We examined the impact of Sab-mediated signaling on imatinib mesylate cardiotoxicity in H9c2 rat cardiomyocyte-like cells. Silencing Sab increased the LD50 of imatinib mesylate 4-fold in H9c2 cells. Disrupting Sab-mediated signaling prevented imatinib mesylate-induced apoptosis as well. Knockdown of Sab or inhibition with a small peptide prevented oxidative stress, which was indicated by decreased reactive oxygen species production, lipid peroxidation, and protein carbonylation. Further, inhibition of Sab-related signaling partially rescued deficits in mitochondrial respiration, ATP production, and membrane potential in imatinib mesylate-treated H9c2 cells. Conversely, over-expression of Sab in H9c2 cells increased the cardiotoxicity of imatinib mesylate in vitro decreasing the LD50 over 4-fold. Sab expression was induced in H9c2 cells following cardiovascular-like stress in an AP-1 dependent manner. These data demonstrate that imatinib mesylate influences mitochondrial signaling leading to mitochondrial dysfunction and cardiotoxicity.

Long-term results of treatment of advanced dermatofibrosarcoma protuberans (DFSP) with imatinib mesylate - The impact of fibrosarcomatous transformation.[Pubmed:28365129]

Eur J Surg Oncol. 2017 Jun;43(6):1134-1141.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is rare, infiltrating dermal neoplasm, characterized by indolent growth and low probability of metastases. The first effective systemic therapy in DFSP introduced into clinical practice was imatinib, demonstrating high activity in advanced cases. The aim of the study was to perform an analysis of patients with advanced DFSP treated with imatinib, with or without surgery, in routine clinical practice with long-term follow-up. PATIENTS AND METHODS: We analyzed the data of 31 Caucasian patients (14 male, 17 female; median age 56 years) with locally advanced/initially inoperable and/or metastatic DFSP who started therapy with imatinib at initial dose 800 mg daily between 12/2004 and 07/2014. All diagnoses were confirmed cytogenetically for the presence of specific COL1A1-PDGFB fusion. Median follow-up time was 5.3 years. RESULTS: Metastases were present in 15 cases (8 - lungs, 5 - soft tissue, 2 - lymph nodes). Fibrosarcomatous transformation (FS-DFSP) was confirmed in 16 patients (52%). 5-year progression-free survival (PFS) rate was 58% (median 6.8 years), 5-year overall survival (OS) rate was 64% (median time for OS was not reached). The shorter PFS and OS correlated with FS-DFSP and presence of metastatic disease. 5-year PFS rate was 93% for classic DFSP and 33% for FS-DFSP. The best overall responses were: 21 partial responses (68%, including 8 FS-DFSP, but the responses were shorter than for classic DFSP), 6 stable disease (19%) and 4 progressive diseases (13%). Thirteen patients (47%) underwent resection of residual disease and nine of them remained free of disease, although imatinib was discontinued. Median survival after progression on imatinib was 19 months, and longer survival were observed only in cases were rescue surgery/radiotherapy was possible. CONCLUSIONS: Our results indicate the long-term activity of imatinib in therapy of inoperable and/or metastatic cases of DFSP, including FS-DFSP. Some DFSP patients initially evaluated as unresectable/metastatic or necessitating mutilating surgery turned resectable after imatinib therapy and this rational approach leading to complete remission maybe potentially curative.

Genetic Polymorphisms Contribute to the Individual Variations of Imatinib Mesylate Plasma Levels and Adverse Reactions in Chinese GIST Patients.[Pubmed:28335376]

Int J Mol Sci. 2017 Mar 13;18(3). pii: ijms18030603.

Imatinib mesylate (IM) has dramatically improved the outcomes of gastrointestinal stromal tumor (GIST) patients. However, the clinical responses of IM may considerably vary among single individuals. This study aimed to investigate the influences of genetic polymorphisms of drug-metabolizing enzyme (CYP3A4), transporters (ABCB1, ABCG2), and nuclear receptor (Pregnane X Receptor (PXR, encoded by NR1I2)) on IM plasma levels and related adverse reactions in Chinese GIST patients. A total of 68 Chinese GIST patients who have received IM 300-600 mg/day were genotyped for six single nucleotide polymorphisms (SNPs) (CYP3A4 rs2242480; ABCB1 rs1045642; ABCG2 rs2231137; NRI12 rs3814055, rs6785049, rs2276706), and the steady-state IM trough plasma concentrations were measured by a validated HPLC method. There were statistically significant variances in the steady-state IM trough plasma concentrations (from 272.22 to 4365.96 ng/mL). Subjects of GG in rs2242480, T allele carriers in rs1045642 and CC in rs3814055 had significantly higher steady-state IM dose-adjusted trough plasma concentrations. Subjects of CC in rs3814055 had significantly higher incidence rate of edema. The genetic polymorphisms of rs2242480, rs1045642, rs3814055 were significantly associated with IM plasma levels, and the genetic variations of rs3814055 were significantly associated with the incidence rate of edema in Chinese GIST patients. The current results may serve as valuable fundamental knowledge for IM therapy in Chinese GIST patients.