Pharmacological evaluation of disulfiram analogs as antimicrobial agents and their application as inhibitors of fosB-mediated fosfomycin resistance.

Disulfide analogs of the alcohol sobriety medication disulfiram (Antabuse®) were evaluated for antimicrobial activity. Structure-activity relationship analyses of MIC data obtained for methicillin-resistant Staphylococcus aureus (MRSA) and other pathogenic organisms revealed correlations between the lipophilicity and bulkiness of the substituents. Analogs conferring optimal anti-MRSA activity contained S-octyl disulfides and either N,N-dimethyl- or N-pyrrolidine dithiocarbamate substituents. Additional testing revealed that both disulfiram and its S-octyl derivative are capable of sensitizing S. aureus to the bactericidal effects of fosfomycin. Mechanistic studies established that the compounds decrease intracellular levels of the fosB cofactor bacillithiol through a thiol-disulfide exchange reaction. The increased fosfomycin susceptibility in S. aureus was thereby attributed to a depleted cellular bacillithiol pool available for inactivation by fosB.

Moving towards fast characterization of polymorphic drugs by solid-state NMR spectroscopy.

Solid-state nuclear magnetic resonance (SS-NMR) spectroscopy has become a common technique to study polymorphism in pharmaceutical solids at high-resolution. However, high-throughput application of high resolution SS-NMR spectroscopy is severely limited by the long 1H spin-lattice relaxation (T1) that is common to solid phase compounds. Here, we demonstrate the use of paramagnetic relaxation reagents such as chromium (III) acetylacetonate (Cr(acac)3) and nickel (II) acetylacetonate (Ni(acac)2) for fast data acquisition by significantly reducing the T1 value for carbamazepine Forms I, II, III, and dihydrate, cimetidine Forms A and B, nabumetone Form I, and acetaminophen Form I polymorphs. High resolution 13C cross-polarization and magic angle spinning were used to measure T1 values for each polymorph. In order to confirm the absence of polymorphic transitions during SS-NMR experiments, powder x-ray diffraction was implemented. The amount of chromium ions incorporated by the recrystallization process was quantified by using inductively coupled plasma optical emission spectroscopy. Our results suggest that the paramagnetic ions added to the polymorphs do not affect the polymorphic transformation or the quality of NMR spectra. We believe that this successful demonstration of fast data collection will enable high-throughput utilization of SS-NMR techniques to study polymorphic solids and could set the groundwork for NMR crystallography studies.