Moving forward with molecular skeleton editing (MSE) for new drug discovery: where to next?

INTRODUCTION: Molecular Skeleton Editing has emerged as a powerful strategy in medicinal chemistry, gaining significant attention over the past decade for its ability to rapidly access structurally diverse molecules. This approach encompasses the substitution, deletion and insertion of atoms within molecular frameworks, often resulting in ring expansion or contraction. From a drug discovery perspective, these transformations enable the direct conversion of core scaffolds into bioisosteric analogues while preserving substitution patterns, providing an efficient route to optimize biological and physicochemical properties. AREAS COVERED: This review focuses on molecular editing approaches relevant to drug discovery that involve single-atom substitution, deletion or insertion, leading to skeletal modifications of cyclic frameworks. Representative examples highlighting the synthesis of therapeutically relevant compounds through these methodologies will be discussed. Peripheral editing, skeletal recasting, stereochemical editing, and functional group transpositions are beyond the scope of this review. EXPERT OPINION: . Despite these advances, important challenges remain, particularly the extension of editing methodologies to saturated sp³-rich systems and the development of stereoselective processes that preserve or generate optically pure products.