High-Throughput Screening for Drug Discovery toward Infectious Diseases: Options and Challenges

*Ankur Gupta, Swatantra Kumar, Vimal K. Maurya, Bipin Puri and Shailendra K. Saxena*

### **Abstract**

The increase in the number of antibiotic-resistant microbial strains makes it evident to discover and develop newer efficacious anti-infective drugs. Highthroughput screening (HTS) is a robust technology that plays a crucial role in identifying novel anti-infective lead compounds. This chapter briefly explains the role of virtual HTS (vHTS) and HTS technologies in lead identification using various categories of chemical libraries through structure-based drug design, ligand-based drug design, *in vitro* cell-based assay, and biochemical assay approaches involved in the process of drug design and discovery. The chapter also gives an insightful survey of the technologies such as fluorescence, luminescence, and atomic absorbance used for the detection of biological responses in the HTS bioassays. Applications of HTS, reverse pharmacology, current challenges, and future perspectives of HTS in the pharmaceutical and biotechnology industry are discussed in the context of anti-infective drug design, discovery, and development.

**Keywords:** HTS, vHTS, bioassay, anti-infective, drug discovery

### **1. Introduction**

Antibiotic resistance among evolving microbes has been a matter of concern for pharmaceutical and biotechnology companies around the globe. These emerging pathogens with multiple drug resistance capabilities necessitate the discovery and development of both novel targets and anti-infective drugs. The key to success in anti-infective drug discovery depends on the identification of the target (a novel target for existing or novel strain of microbe) and a substantially active lead molecule against the designated target. Among the two key steps, the former requires genome sequence analysis (genomics) and protein expression analysis (proteomics) to identify target genes/proteins for a broad variety of microbial pathways and the latter requires chemical library screening against the defined target [1]. The chemical library may be generated through various routes such as combinatorial chemistry, bioassay-guided isolation of natural products, food and drug administration (FDA)-approved drugs for repurposing, virtually designed chemical library based on structure-based drug design (SBDD) or quantitative structure-activity relationship (QSAR), or other chemicals for fragment-based drug design (FBDD). However, with the latest advancement in technology, lead identification can be performed

**Figure 1.** *Drug discovery process.*

using high-throughput screening (HTS). HTS is a highly efficient automated method of screening chemical libraries to identify the so-called "hits," which are further modified to drug "leads" for lead optimization through medicinal chemistry approaches [2]. Generally, HTS involves biological or biochemical assay screening [3], whereas computer-based chemical library screening for "hits" identification is termed virtual high-throughput screening (vHTS). However, both the methods are used simultaneously or in parallel enabling the scientists to think computationally, act chemically, and observe biologically [4, 5]; therefore, in the present chapter, vHTS has been coupled with HTS for ease of understanding the correlation between all the stages of the drug discovery process (**Figure 1**).
