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Biomedical subjects

Michael H Fisher

Publications and source records attributed to Michael H Fisher.

13 recordsLinked to original sources
PubMed2005

Synthesis and SAR of 1,2-trans-(1-hydroxy-3-phenylprop-1-yl)cyclopentane carboxamide derivatives, a new class of sodium channel blockers.

Novel cyclopentane-based 3-phenyl-1-hydroxypropyl compounds were evaluated for inhibitory activity against the peripheral nerve sodium channel Na(V)1.7 and off-target activity against the cardiac potassium channel hERG. The stereochemistry of the hydroxyl group and substitution on the phenyl rings with either fluorinated O-alkyl or alkyl groups were found to be critical for conferring potency against Na(V)1.7. A benchmark compound from this series displayed efficacy in rat models of inflammatory and neuropathic pain.

Animals↗
PubMed2005

Tat-conjugated PAMAM dendrimers as delivery agents for antisense and siRNA oligonucleotides.

PURPOSE: PAMAM G5 dendrimer (P) was conjugated to Tat peptide (T), a cell penetrating peptide, in search of an efficient cellular delivery vehicle for antisense and siRNA oligonucleotides. METHODS: PAMAM G5 dendrimer was reacted with 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid, sulfosuccinimidyl ester, sodium salt (BODIPY) for visualization to yield the conjugate BP. Bifunctional sulfosuccinimidyl 6-[alpha-methyl-alpha-(2-pyridyldithio)toluamido]hexanoate (sulfo-LC-SMPT) was then used to conjugate primary amino groups of BP to cysteine derivatized Tat peptide to give the designed conjugate, BPT. This conjugate was complexed with antisense and siRNA oligonucleotides designed to inhibit MDR1 gene expression. NIH 3T3 MDR cells were used for the evaluation of biological activity of the conjugate. RESULTS: Both antisense and siRNA readily formed complexes with the synthesized BPT, introduced into NIH 3T3 MDR cells, and primarily accumulated in intracellular vesicles. MDR1 gene expression was partially inhibited by the antisense-BPT complex and weakly inhibited by the siRNA-BPT complex when both were tested at nontoxic levels of dendrimer. Conjugation with Tat peptide did not improve the delivery efficiency of the dendrimer. CONCLUSIONS: Dendrimer-oligonucleotide complexes were moderately effective for delivery of antisense and only poorly effective for delivery of siRNA. Conjugation of the dendrimer with the Tat cell penetrating peptide failed to further enhance the effectiveness of the dendrimer.

3T3 Cells↗
PubMed2005

Discovery of potent and use-dependent sodium channel blockers for treatment of chronic pain.

A new series of voltage-gated sodium channel blockers with potential for treatment of chronic pain is reported. Systematic structure-activity relationship studies, starting with compound 1, led to identification of potent analogs that displayed use-dependent block of sodium channels, were efficacious in pain models in vivo, and most importantly, were devoid of activity against the cardiac potassium channel hERG.

Chronic Disease↗
PubMed2005

(2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine: a potent, orally active dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes.

A novel series of beta-amino amides incorporating fused heterocycles, i.e., triazolopiperazines, were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-IV) for the treatment of type 2 diabetes. (2R)-4-Oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine (1) is a potent, orally active DPP-IV inhibitor (IC(50) = 18 nM) with excellent selectivity over other proline-selective peptidases, oral bioavailability in preclinical species, and in vivo efficacy in animal models. MK-0431, the phosphate salt of compound 1, was selected for development as a potential new treatment for type 2 diabetes.

Administration, Oral↗
PubMed2004

Inhibition of MDR1 gene expression by chimeric HNA antisense oligonucleotides.

Hexitol nucleic acids (HNAs) are nuclease resistant and provide strong hybridization to RNA. However, there is relatively little information on the biological properties of HNA antisense oligonucleotides. In this study, we compared the antisense effects of a chimeric HNA 'gapmer' oligonucleotide comprising a phosphorothioate central sequence flanked by 5' and 3' HNA sequences to conventional phosphorothioate oligonucleotides and to a 2'-O-methoxyethyl (2'-O-ME) phosphorothioate 'gapmer'. The antisense oligomers each targeted a sequence bracketing the start codon of the message of MDR1, a gene involved in multi-drug resistance in cancer cells. Antisense and control oligonucleotides were delivered to MDR1-expressing cells using transfection with the cationic lipid Lipofectamine 2000. The anti-MDR1 HNA gapmer was substantially more potent than a phosphorothioate oligonucleotide of the same sequence in reducing expression of P-glycoprotein, the MDR1 gene product. HNA and 2'-O-ME gapmers displayed similar potency, but a pure HNA antisense oligonucleotide (lacking the phosphorothioate 'gap') was ineffective, indicating that RNase H activity was likely required. Treatment with anti-MDR1 HNA gapmer resulted in increased cellular accumulation of the drug surrogate Rhodamine 123 that correlated well with the reduced cell surface expression of P-glycoprotein. Thus, HNA gapmers may provide a valuable additional tool for antisense-based investigations and therapeutic approaches.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Increased uptake of antisense oligonucleotides by delivery as double stranded complexes.

Antisense oligonucleotides were potentially very powerful tools to modulate gene expression. Progress in chemical modification of oligonucleotides to enhance the strength and stability of interaction, without loosing specificity, has made the antisense strategy very attractive for therapeutic manipulation of the gene expression. However, pharmacological applications of oligonucleotides have been hindered by the inability to effectively deliver these compounds to their sites of action within cells. In this study we evaluated a new concept for antisense delivery in cellular systems. We have shown that formation of a duplex between the active oligonucleotide (with a chemically modified backbone) and an easily degradable complementary oligodeoxynucleotide in the presence of Lipofectamine 2000 leads to better intracellular uptake and more significant pharmacological effect of the active oligonucleotide. To evaluate our approach we targeted the MDR1 gene, which coded for P-glycoprotein, a membrane ATPase associated with multi-drug resistance in tumor cells. The 2'-O-methyl gapmer antisense RNA (active component of the duplex) was complementary to a site flanking the AUG of the MDR1 message. Effective inhibition of P-glycoprotein expression was attained with sub-micromolar concentrations of duplexes under serum-replete conditions and was much stronger than with traditional single stranded antisense delivery. The results obtained suggested that double stranded delivery could provide a simple and effective means for enhancing cell uptake of pharmacologically active oligonucleotides.

3T3 Cells↗
PubMed2003

Benzyl vinylogous amide substituted aryldihydropyridazinones and aryldimethylpyrazolones as potent and selective PDE3B inhibitors.

Aryldihydropyridazinones and aryldimethylpyrazolones with 2-benzyl vinylogous amide substituents have been identified as potent PDE3B subtype selective inhibitors. Dihydropyridazinone 8a (PDE3B IC(50)=0.19 nM, 3A IC(50)=1.3 nM) was selected for in vivo evaluation of lipolysis induction, metabolic rate increase, and cardiovascular effects.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed2003

Nodulisporic acid side-chain modifications: access to the 2", 3", 4", and 6" registers.

Efficient routes to access the 2", 3", 4", and 6" registers of the nodulisporic acid (NsA) side chain are disclosed. A mild one-carbon, Ph(2)CdoublebondNCH(2)CtriplebondN mediated homologation of NsA's 3"-aldehyde permitted access to the 4"-register. Curtius reaction of NsA's 3"-acid yielded the corresponding 2"-aldehyde 4 from which the unnatural Delta(2",3")-olefin isomer 2b was obtained. In addition, Arndt-Eistert reactions of the parent NsA permitted a one-carbon homologation to the 6" register. These efforts identified new analogues with significant flea activity and illustrated the biological significance of unsaturation at the 1",2" register.

Alkenes↗
PubMed2002

Side-chain homologation of nodulisporic acid: synthesis of potent new dienyl derivatives.

A series of new, diene-modified nodulisporic acid analogues (2) bearing diverse functionality at the 3"- and 4"-sites was efficiently prepared from the 3"-aldehyde 3. Biological evaluation of these synthetic nodulisporic acid analogues for systemic flea efficacy identified potent compounds and further clarified the structural requirements for ectoparasite activity.

Animals↗
PubMed2002

Synthesis of side chain truncated 3"-aldehyde, 3"-carboxylic acid, and 1"-aldehyde from nodulisporic acid A.

An efficient synthesis of the truncated 3"-aldehyde (3) from nodulisporic acid A (1) under mild conditions is described. Further oxidation of 3 to 3"-carboxylic acid (4) and its subsequent oxidative degradation produced 1"-aldehyde (5). These new derivatives are versatile intermediates for the preparation of new, side chain modified derivatives of nodulisporic acid A. [reaction: see text]

Aldehydes↗
PubMed2002

Evaluating the specificity of antisense oligonucleotide conjugates. A DNA array analysis.

Antisense oligonucleotides are potentially powerful tools for selective control of cellular and viral gene expression. Crucial to successful application of this approach is the specificity of the oligonucleotide for the chosen RNA target. Here we apply DNA array technology to examine the specificity of antisense oligonucleotide treatments. The molecules used in these studies consisted of phosphorothioate oligomers linked to the Antennapedia (Ant) delivery peptide. The antisense oligonucleotide component was complementary to a site flanking the AUG of the MDR1 message, which codes for P-glycoprotein, a membrane ATPase associated with multidrug resistance in tumor cells. Using a DNA array of 2059 genes, we analyzed cellular responses to molecules comprised of Ant peptide-oligonucleotide conjugates, as well as to the Ant peptide alone. Besides the expected reduction in MDR1 message level, 37 other genes (approximately 2% of those tested) showed changes of comparable magnitude. The validity of the array results was confirmed for selected genes using Northern blots to assess messenger RNA levels. These results suggest that studies using antisense oligonucleotide technology to modulate gene expression need to be interpreted with caution.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Delivery of antisense oligonucleotides using cholesterol-modified sense dendrimers and cationic lipids.

Cholesterol modified mono-, di-, and tetrameric oligonucleotides were synthesized and hybridized with antisense oligonucleotides to study their incorporation in cationic liposomes together with the influence of this dendrimeric delivery system on biological activity. Electrostatic interactions seem to play the most important role during complexation with cationic lipids. This oligonucleotide formulation gives a small but significant increase in the inhibition of P-glycoprotein expression in a cellular system.

3T3 Cells↗