Michael Chlenov

Discovery of Begacestat, a Notch-1-Sparing γ-Secretase Inhibitor for the Treatment of Alzheimer's Disease

SAR on HTS hits 1 and 2 led to the potent, Notch-1-sparing GSI 9, which lowered brain Abeta in Tg2576 mice at 100 mg/kg po. Converting the metabolically labile methyl groups in 9 to trifluoromethyl groups afforded the more stable analogue 10, which had improved in vivo potency. Further side chain modification afforded the potent Notch-1-sparing GSI begacestat (5), which was selected for development for the treatment of Alzheimers disease.

Relative hydrophobicity and lipophilicity of drugs measured by aqueous two-phase partitioning, octanol-buffer partitioning and HPLC. A simple model for predicting blood-brain distribution.

Relative hydrophobicity and lipophilicity of 63 compounds with known permeability through the blood-brain barrier (BBB) was examined by partitioning in aqueous dextran-poly(ethylene glycol) two-phase system and octanol-buffer system, and by gradient RP-HPLC at pH 7.4. Combination of the relative hydrophobicity estimates, N(CH(2)) obtained by aqueous two-phase partitioning and the lipophilicity (logD(exp) or logD(HPLC)) values obtained by the shake-flask technique or HPLC technique allows one to differentiate between compounds capable of crossing the BBB and those that cannot. A simple model for predicting blood-brain distribution is proposed.

Relative hydrophobicity and lipophilicity of β-blockers and related compounds as measured by aqueous two-phase partitioning, octanol–buffer partitioning, and HPLC

Partitioning of 15 beta-blockers and structurally related compounds was examined in aqueous dextran-PEG two-phase systems and octanol-buffer systems at pH from 2.0 up to 12.5. The same compounds were examined by gradient RP-HPLC at pH 2.0, 7.4, and 11.0. The differences between the hydrophobic character of the phases in all three systems at different pH values were characterized using a homologous series of dinitrophenyl-amino acids by measuring the free energy of transfer of a methylene group. Estimates of the relative hydrophobicity, N(CH(2)), and lipophilicity, logD, of the compounds obtained by the three techniques employed were compared. The data indicate that while similar pH profiles for a given compound were established by all these techniques, the information provided is different. It is suggested that the combination of the two descriptors, logD and N(CH(2)), may be useful for quantitative structure-activity relationship analysis of the biological activities involving distribution and/or transport of chemical compounds in biological systems.

Use of solute partition for comparative characterization of several aqueous biphasic polymeric systems

Abstract Eight biphasic ficoll-dextran systems differing in the molecular weight of the latter polymer and in the polymer composition were studied. The effect of the salt composition on the phase diagrams for all systems was examined and it is shown that salts present in the polymer mixture should be considered as essential components of the mixture involved in the separation of phases. The partition behaviour of a number of proteins and dinitrophenyl-amino acids in the systems was studied. It is shown that the partition coefficients obtained in different phase systems can be correlated using the relation ln Kl = a ln Ko + b, where Kl and Ko are the partition coefficients of a solute in the system in question and in the system chosen as the reference, respectively, and a and b are the scaling factors independent of the chemical nature of the solutes partitioned. The difference in the relative hydrophobicities between the two phases was determined experimentally in two phase systems and calculated for six other systems. It is shown that it is possible to compare the partition results obtained in various polymer phase systems using any solutes chosen as “partition markers”.

Synthesis and structure–activity relationship of novel lactam-fused chroman derivatives having dual affinity at the 5-HT1A receptor and the serotonin transporter

The structure-activity relationship (SAR) for three series of lactam-fused chroman derivatives possessing 3-amino substituents was evaluated. Many compounds exhibited affinities for both the 5-HT(1A) receptor and the 5-HT transporter. Compounds 45 and 53 demonstrated 5-HT(1A) antagonist activities in the in vitro cAMP turnover model.

Synthesis of indane derivatives as mechanism-based inhibitors of dopamine β-hydroxylase

Abstract A series of indane derivatives was synthesized and evaluated as mechanism-based inhibitors of dopamine β-hydroxylase (DBH).

Optimization of normal-phase chromatographic separation of compounds with primary, secondary and tertiary amino groups

The retention behavior of primary, secondary and tertiary amines was studied using normal-phase-HPLC on silica, diol, and cyano stationary phases. Several classes of amines, including benzylamines, anilines, ephedrines, tryptamines, and azatryptamines were chromatographed using mixtures of hexane and ethoxynonafluorobutane with methylene chloride and methanol. Peak tailing, diminished selectivity and low plate count were minimized by the addition of volatile amines to the mobile phase. The optimal additive was n-propylamine at 0.1% concentration. On diol columns, the elution order of free primary, N-N-methyl, and N,N-dimethylamines was predictable, while the elution order of primary and secondary amines on cyano columns varied depending on the alcohol modifier concentration. The feasibility of preparative normal-phase chromatography was demonstrated by the separation of a mixture of primary, secondary and tertiary amines obtained by direct methylation of norephedrine. The procedures described may provide a practical alternative to traditional methods of analysis and purification of potential drug candidates.

Mass‐Directed Normal‐Phase Preparative HPLC with Atmospheric Pressure Chemical Ionization Detection

Abstract A novel approach to auto‐purification of a wide variety of organic compounds is described. It is based on normal‐phase (NP) gradient high performance liquid chromatography (HPLC), performed on a 2 × 15 cm cyano column hyphenated with atmospheric pressure chemical ionization (APCI) source, and a single quad mass spectrometer (MS). A commercially available preparative HPLC–MS system, equipped with mass‐directed fraction collection capabilities, has been successfully used for NP purification of neutral, acidic, and basic pharmacologically active compounds. Samples of 10–100 mg were chromatographed in gradients of methanol in hydrophobic organic solvents, and collected using generic chromatographic, detection and fraction collection experimental parameters. “Smart” collection—one component–one collection vessel—with 90–95% recovery, was achieved by controlling injection volume and gradient slope and by adding acetic acid and diethylamine to the mobile phase to keep peak elution volumes below 50 mL. Auto‐collection of a solute was based on the main ion in its APCI–MS spectrum. The technique described has been also successfully used for chiral preparative HPLC applications and purification of non‐UV‐active compounds.

New approaches to chromatographic purification of bovine dopamine-β-hydroxylase

The use of the traditional scheme for the isolation of bovine dopamine-beta-hydroxylase (bDBH) from bovine adrenal medulla resulted in active but not pure bDBH, containing about 50% of admixtures. Immobilized metal chelate affinity chromatography on agarose modified with iminodiacetic acid residues and charged with cobalt ions was applied in the final stage to obtain more than 90% pure and active bDBH. Final purification of bDBH using step elution with 0-0.5 M methyl-D-mannoside in buffer solution from concanavalin A-Sepharose was studied. The determination of bDBH in various samples was performed using size-exclusion chromatography.

Novel human metabolites of the angiotensin-II antagonist tasosartan and their pharmacological effects.

Three novel metabolites of the angiotensin-II (A-II) receptor antagonist tasosartan have been identified in humans, and the syntheses and pharmacologic profiling of these metabolites are reported. Each metabolite bound the human A-II receptor with IC(50)s between 20 and 45nM. The in vivo effects of these compounds in attenuating the pressor response to angiotensin-II challenge in anesthetized rats were also investigated. An unsaturated diol metabolite exhibited in vivo efficacy at intravenous doses of 1 and 3mg/kg, while the other metabolites, both carboxylic acids, had no significant effect at the same doses.