Chemical structure modifications and nano-technology applications for improving ADME-Tox properties, a review

The chemical structure of a drug molecule affects its physicochemical properties and subsequent biological activities. Many pharmacologically active molecules fail to reach the market or have an inconvenient route of administration due to their chemical structure. This is especially important with the recent tendency to develop drug candidates beyond the drug-likeness space for addressing difficult targets such as protein-protein interfaces. The objective of this review is to discuss chemical and pharmaceutical approaches for circumventing structure-related problems and achieving acceptable ADME-Tox properties. The chemical structure-associated limitations are critically discussed. Chemical modifications and pharmaceutical technology applications for improving drug-likeness are illustrated. Attention is paid to modern therapeutic candidates and targets. In conclusion, chemical modifications as well as nanotechnology applications can be used effectively to enhance absorption, permeability, and selective distribution to a body compartment, to improve drug specificity, to limit off-target toxicity as well as to enhance stability and to protect against metabolism. The nano-technology-based solutions are relatively easier to develop over a new molecular entity, but adopting the chemical approach is more established in terms of safety, quality control, and regulatory assessment methods.