Richard A. Dalterio

Envelope Conformational Changes Induced by Human Immunodeficiency Virus Type 1 Attachment Inhibitors Prevent CD4 Binding and Downstream Entry Events

ABSTRACT BMS-488043 is a small-molecule human immunodeficiency virus type 1 (HIV-1) CD4 attachment inhibitor with demonstrated clinical efficacy. The compound inhibits soluble CD4 (sCD4) binding to the 11 distinct HIV envelope gp120 proteins surveyed. Binding of BMS-488043 and that of sCD4 to gp120 are mutually exclusive, since increased concentrations of one can completely block the binding of the other without affecting the maximal gp120 binding capacity. Similarly, BMS-488043 inhibited virion envelope trimers from binding to sCD4-immunoglobulin G (IgG), with decreasing inhibition as the sCD4-IgG concentration increased, and BMS-488043 blocked the sCD4-induced exposure of the gp41 groove in virions. In both virion binding assays, BMS-488043 was active only when added prior to sCD4. Collectively, these results indicate that obstruction of gp120-sCD4 interactions is the primary inhibition mechanism of this compound and that compound interaction with envelope must precede CD4 binding. By three independent approaches, BMS-488043 was further shown to induce conformational changes within gp120 in both the CD4 and CCR5 binding regions. These changes likely prevent gp120-CD4 interactions and downstream entry events. However, BMS-488043 could only partially inhibit CD4 binding to an HIV variant containing a specific envelope truncation and altered gp120 conformation, despite effectively inhibiting the pseudotyped virus infection. Taken together, BMS-488043 inhibits viral entry primarily through altering the envelope conformation and preventing CD4 binding, and other downstream entry events could also be inhibited as a result of these induced conformational changes.

Carbamates as potent calcitonin gene-related peptide antagonists with improved solution stability.

The calcitonin gene-related peptide (CGRP) receptor has been implicated in the pathogenesis of migraine. A class of urethanamide derivatives has been identified as potent inhibitors of the CGRP receptor. Compound 20 was found to be among the most potent (IC(50)=17pM). It was shown to retain excellent aqueous solubility (>50mg/mL, pH 7) while dramatically improving solution stability as compared to our previously disclosed development candidate, BMS-694153 (1).

Separation of maxi-K channel opening 3-substitued-4-arylquinolinone atropisomers by enantioselective supercritical fluid chromatography

Many 3-substituted-4-arylquinolinones containing an ortho substituent on the aryl ring were known as a class of compounds with maxi-K opening activity. These quinolinones, which contained a stereogenic axis in their structures due to their bulky ortho substituents on the two aryl rings, exhibited atropisomerism. The rotationally hindered atropisomers could have differential biological and pharmacological activity, and it was highly desirable to separate them and test the individual atropisomers in biological assays. To explore the potential of supercritical fluid chromatography (SFC) to separate the atropisomers of this class of compounds, six 3-substituted-4-arylquinolinones with various hydrophilic and hydrophobic substituents in various positions were screened using three alcoholic modifiers (methanol, ethanol and 2-propanol) with four polysaccharide-based chiral stationary phases (Chiralpak AD-H and AS-H, Chiralcel OD-H and OJ-H). Our results showed that all six compounds studied were successfully resolved under multiple SFC conditions regardless of their structural differences and polarity. The majority of the separations were completed within 10 min. The Chiralpak AD-H column appeared to be superior to the other three chiral columns, and methanol and ethanol showed higher successful rate than 2-propanol in separating atropisomers of this class of compounds. These SFC methods were efficient and easily scalable for preparative separation. Thus, SFC was found to be the methodology of choice for resolving the atropisomers of this class of compounds.

Chiral separation of potent corticotropin-releasing factor-1 receptor antagonists by supercritical fluid chromatography.

Pyrazinones bearing an N-1-alkyl chain with a chiral center have been reported as potent antagonists of the corticotropin-releasing factor-1 receptor (CRF1R). Separation of individual enantiomers for preclinical testing was an important aspect of lead optimization. To evaluate the applicability and efficiency of supercritical fluid chromatography (SFC) for enantiomeric resolution of this class of compounds, enantiomeric pairs of eight pyrazinones with different structural characteristics were tested under an array of SFC conditions. The results showed that pyrazinones with a 1-cyclopropyl-2-methoxyethyl substituent were readily separated with a Chiralpak AD-H or Chiralcel OD-H column with ethanol as the modifier. On the other hand, analogs with a less polar alkyl substituent were not amenable to the general method and required further optimization of the chromatographic conditions. In addition, structural variations on the pyrazinone core and aromatic moiety had an impact on the chiral resolution of this class of compounds. This investigation led to the development of efficient chiral SFC methods for separating all eight pyrazinone enantiomeric pairs encompassing an array of structural variations.