Multicomponent Synthesis and Binding Mode of Imidazo[1,2- a]pyridine-Capped Selective HDAC6 Inhibitors

The multicomponent synthesis of a mini-library of histone deacetylase inhibitors with imidazo[1,2- a]pyridine-based cap groups is presented. The biological evaluation led to the discovery of the hit compound MAIP-032 as a selective HDAC6 inhibitor with promising anticancer activity. The X-ray structure of catalytic domain 2 from Danio rerio HDAC6 complexed with MAIP-032 revealed a monodentate zinc-binding mode.

Anti-tubercular activity of a natural stilbene and its synthetic derivatives

Objectives: Tuberculosis (TB) and multidrug- and extensively drug-resistant TB in particular are remaining a major global health challenge and efficient new drugs against TB are needed. This study evaluated the anti-tubercular activity of a natural stilbene and its synthetic derivatives against M. tuberculosis.

Methods: Isopropylstilbene and its synthetic derivatives were analyzed for their anti-tubercular activity against M. tuberculosis ATCC 27294 as well as multidrug- and extensively drug-resistant M. tuberculosis clinical isolates by using MGIT 960 instrumentation and EpiCenter software equipped with TB eXiST module. Cytotoxic effects of drug candidates were determined by a MTT dye reduction assay using A549 adenocarcinomic human alveolar basal epithelial cells.

Results: Growth of M. tuberculosis ATCC 27294 was suppressed by the natural isopropylstilbene HB64 as well as synthetic derivatives DB56 and DB55 at 25 µg/ml. Growth of clinical isolates MDR and XDR M. tuberculosis was suppressed by HB64 at 100 µg/ml as well as by synthetic derivatives DB56 and DB55 at 50 µg/ml and 25 µg/ml, respectively. No anti-tubercular activity was demonstrated for synthetic derivatives DB53, EB251, and RB57 at 100 µg/ml. Toxicity in terms of IC₅₀ values of HB64, DB55 and DB56 were 7.92 µg/ml, 12.15 µg/ml and 16.01 µg/ml, respectively.

Conclusions: Synthetical derivatives of stilbene might be effective candidates as anti-tubercular drugs. However, toxicity of these substances as determined by IC₅₀ values might limit therapeutic success in vivo. Further investigations should address lowering the toxicity for parenteral administration by remodeling stilbene derivatives.