Designing new antitubercular isoniazid derivatives with improved reactivity and membrane trafficking abilities

Isoniazid (INH) is one of the two most effective first-line antitubercular drugs and is still used at the present time as a scaffold for developing new compounds to fight TB. In a previous study, we have observed that an INH derivative, an hydrazide N '-substituted with a C10acyl chain, was able to counterbalance its smaller reactivity with a higher membrane permeability. This resulted in an improved performance against the most prevalent Mycobacterium tuberculosis (Mtb) resistant strain (S315T), compared to INH. In this work, we have designed two new series of INH derivatives (alkyl hydrazides and hydrazones) with promising in silico properties, namely membrane permeabilities and spontaneous IN* radical formation. The kinetics, cytotoxicity, and biological activity evaluations confirmed the in silico predictions regarding the very high reactivity of the alkyl hydrazides. The hydrazones, on the other hand, showed very similar behavior compared to INH, particularly in biological tests that take longer to complete, indicating that these compounds are being hydrolyzed back to INH. Despite their improved membrane permeabilities, the reactivities of these two series are too high, impairing their overall performance. Nevertheless, the systematic data gathered about these compounds have showed us the need to find a balance between lipophilicity and reactivity, which is paramount to devise better INH-based derivatives aimed at circumventing Mtb resistance.

Automated summary

INH derivative showed better performance against resistant strains, while two new series of INH derivatives with promising in silico properties were designed. However, alkyl hydrazides were too reactive and hydrazones tended to hydrolyze back to INH. Finding a balance between lipophilicity and reactivity is crucial for developing better INH-based derivatives.