Cystathionine-γ-lyase (CSE) is a key enzyme for H₂S generation in the pathogenic bacteria Staphylococcus aureus, Pseudomonas aeruginosa, etc. Suppression of CSE activity significantly increases the antibiotic susceptibility of bacteria. In this work a method to synthesize a novel indole-based CSE inhibitor, 3-ammo-5-[(6-bromo-1#-mdol-1-yl)methyl]thiophene, named MNS1, has been developed. The synthesis of MNS1 is based on the modification of substituted thiophene as a main structural fragment, which is involved in alkylation of 6-bromoindole at final steps. The dissociation constant of the MNS1 complex with S. aureus CSE (SaCSE) is 0.5 μM, one order of magnitude lower than with human CSE (hCSE). MNS1 was shown to efficiently enhance the antibacterial effect of gentamicin against Bacillus subtilis, suggesting its possible use as an antibiotic potentiator to inhibit the growth of CSE-expressing bacterial cells.