Discovery and biological evaluation of an adamantyl-amide derivative with likely MmpL3 inhibitory activity

A series of previously synthesized molecules containing bulky lipophilic scaffolds were screened for activity against Mycobacterium tuberculosis and a number of compounds with antimycobacterial activity were identified. Further analysis of the most active compound showed that (2E)-N-(adamantan-1-yl)-3-phenylprop-2-enamide (C1) has a low micro molar minimum inhibitory concentration, low cytotoxicity (therapeutic index = 32.26), a low mutation frequency and is active against intracellular Mycobacterium tuberculosis. Whole genome sequencing of mutants resistant to C1 showed a mutation in mmpl3 leading to an F644L amino acid change which may point to the involvement of MmpL3 in the antimycobacterial activity of the compound. In silico mutagenesis and molecular Modelling studies were performed to better understand the binding of C1 within MmpL3 and the role that the specific mutation may play in the interaction at protein level. Analysis revealed that the mutation increases the energy required for binding of C1 within the protein translocation channel of MmpL3. The mutation also decreases the solvation energy of the protein suggesting that the mutant protein might be more solvent-accessible thereby restricting its interaction with other molecules. The results reported here describe a new molecule that may interact with the MmpL3 protein, provides insights into the effect of mutations on MmpL3 protein level interactions and provides a better understanding of this essential protein as a drug target.