As a part of an ongoing search for new isoniazid-related isonicotinoylhydrazones (ISNEs), 2'-monosubstituted isonicotinohydrazides and cyanoboranes, some analogues belonging to these three series of compounds were further evaluated in an in vitro advanced antimycobacterial screening. The results here reported allowed us to extend their structure-activity relationships. A general correlation emerged between their lipophilicity and effectiveness against intracellular M. tuberculosis. On the whole, the most interesting result of this research was that some hydrazides and ISNEs proved to be more effective antimycobacterial agents than parental isoniazid in a TB-infected macrophage model.