Design, synthesis and structure-activity relationship study of wollamide B; a new potential anti TB agent

Wollamide B is a cationic antimycobacterial cyclohexapeptide that exhibits activity against Mycobacterium bovis (M. bovis) (IC50 of 3.1 mu M). Aiming to define its structural activity relationship (SAR), optimizing potency and pharmacokinetic properties, libraries of analogues were synthesized following a standard Fmoc-based solid phase peptide synthesis approach. The antimycobacterial activities of wollamide B and all the synthesized analogues were tested against Mycobacterium tuberculosis (Mtb) H37Rv. Parallely, in vitro drug metabolism and pharmacokinetic (ADME) profiling was done for the synthesized compounds to evaluate their drug likeness. Among the 25 synthesized wollamides five of them showed potent activities with MICs <= 3.1 mu M and found to be nontoxic against human HepG2 cells up to 100 mu M. The results of the in vitro ADME profiling revealed the remarkable plasma stability and very good aqueous solubility of the class in general while the metabolic stability was found to be moderate to low. Of particular note, compounds 7c (MIC = 1.1 mu M) and 13c (0.6 mu M) that exhibited good balance of antimycobacterial activity vs. optimal pharmacokinetic properties could be used as a new lead for further development.