*2.4. Isoniazid Analogs*

Among the many Inh analogs synthesized, Sudoterb (LL 3858) was successfully progressed to Phase 1 [22,23]. Inh, because of its simplicity of structure, remains an attractive starting point for analog-based discovery.

The approach involving modifications of existing drug scaffolds has two important aims: firstly, to discover novel analogs that are active on MTB strains resistant to the parent drug, and secondly, to design 'drug-friendly' molecules. This approach has yielded two, drugs and a third is in development: Pretomanid (Pre), Delamanid (Del), and SQ-109, respectively.

The key learning from these examples is that sustained effort can lead to useful drugs, even though the starting scaffolds have issues.
