**Preface to "In Silico Approaches in Drug Design"**

Mainly due to the development of new hardware architectures and software technologies, Computational Chemistry has achieved maturity and, nowadays is one of the central scientific fields in the pharmaceutical industry. In particular, in silico approaches have been shown to be fundamental for the development of drugs and the study of biological systems, not only at the molecular level, but also at the cellular level.

Applications of in silico tools are crucial in the early stages of drug design, such as planning more efficient and economic synthetic routes for chemical administration, screening of huge databases, as well as proposing hypotheses for probable mechanisms of action of drugs in macromolecular targets. Such endeavors are extremely complex and require the usage of modern and sophisticated approaches, such as artificial intelligence, data mining, computational molecular simulations through classical mechanics and quantum mechanics, molecular docking, chemoinformatics, applied mathematics, and biostatistics.

To celebrate the success story and advances in the important synergistic combination of drug design and in silico investigation, I accepted the challenge of editing a Special Issue for the prestigious journal *Pharmaceuticals*, which is now assembled into a reprint. The text is a collection of 31 original articles and four reviews, published from 2021 to 2022, focused on the application of a wide range of computational tools in medicinal chemistry projects: from molecular docking to artificial intelligence approaches.

I am grateful to Mr. Owen Shu from MDPI for his dedication and wonderful professional support for organizing this work, and, of course, I cannot forget to thank my lovely wife, Claudia Valeria, for encouraging me all the time.

I hope that this reprint makes for interesting reading and will be useful to fellow scientists and graduate students interested in Computational Medicinal Chemistry.

This book is dedicated to: Prof. Dr. J. Daniel Figueroa-Villar Prof. Dr. Anton J. Hopfinger, *in memoriam* Prof. Dr. Ricardo Bicca de Alencastro, *in memoriam*

> **Osvaldo Santos-Filho** *Editor*
