Structure-Activity Relationship Study of 16 a-Thiocamptothecins: an Integrated In Vitro and In Silico Approach

• Published in: ChemMedChem 2010-12, Vol.5 (12), p.2006-2015
• Main Authors: Samorì, Cristian, Beretta, Giovanni L., Varchi, Greta, Guerrini, Andrea, Di%emsp14, Micco, Simone, Basili, Serena, Bifulco, Giuseppe, Riccio, Raffaele, Moro, Stefano, Bombardelli, Ezio, Zunino, Franco, Fontana, Gabriele
• Format: Article
• Language: English
• Subjects: antitumor agents; Binding Sites; Camptothecin - analogs & derivatives; Camptothecin - chemical synthesis; Camptothecin - toxicity; camptothecins; cancer; Cell Line, Tumor; Computer Simulation; DNA - metabolism; DNA Cleavage; DNA Topoisomerases, Type I - chemistry; DNA Topoisomerases, Type I - metabolism; Humans; Lactones - chemistry; Structure-Activity Relationship; structure-activity relationships; Thermodynamics; Topoisomerase I Inhibitors - chemical synthesis; Topoisomerase I Inhibitors - chemistry; Topoisomerase I Inhibitors - toxicity; topoisomerase I
• ISSN: 1860-7179; 1860-7187
• DOI: 10.1002/cmdc.201000369

The instability of the hydroxylactone E ring represents a critical drawback of camptothecins, because the lactone ring is recognized to be essential for stabilization of topoisomerase I‐mediated DNA cleavage. In an attempt to investigate the effect of the thiopyridone pharmacophofore on the molecular and pharmacological features of the drug, we prepared a series of novel 16 a‐thiocamptothecin analogues. Due to the sulfur atom, a destabilization of the hydrogen bond between the hydroxy group in position 17 of the opened E ring and the carbonyl of the pyridone moiety is predicted, thus shifting the equilibrium toward the closed lactone form and increasing the lipophilic properties of the compounds. This feature was associated with superior antiproliferative potency, with reduced interaction with the human serum albumin and with substantial increase of the persistence of the topoisomerase I–DNA cleavable complex. These effects were prominent for thio‐SN38, the most active compound of the series. The favorable interactions at the molecular and cellular level of the reported thiocamptothecins confer promising features, and these compounds warrant preclinical development. Camping it up! 16 a‐thiocamptotecins analogues show superior antiproliferative potency, with reduced interaction with human serum albumin and a substantial increase in the persistence of the topoisomerase I–DNA cleavable complex. The favorable interactions at a molecular and cellular level of the reported thiocamptothecins confer promising features, and these compounds warrant preclinical development.