Small Molecule Drug Development & Discovery

Small molecule screening, also known as high-throughput screening (HTS), is a drug discovery approach that involves testing large compound libraries to identify potential lead compounds with therapeutic activity against specific molecular targets or diseases. Small molecule screening assays typically use automated robotic systems to rapidly screen thousands to millions of compounds against biological targets or cellular models in a high-throughput manner. Screening assays may involve biochemical assays, cell-based assays, or phenotypic assays tailored to the target or disease of interest. Small molecule screening enables the identification of hit compounds that modulate target activity or exhibit desired biological effects, providing starting points for lead optimization and drug development. This approach accelerates the drug discovery process, facilitates the identification of novel drug candidates, and expands the chemical space for therapeutic intervention in various diseases. Incorporating DNA encoded libraries into the screening process can further enhance the efficiency and diversity of compound identification.

Small molecule and biologics development represent two distinct approaches to drug discovery and development based on different types of compounds and manufacturing processes. Small molecule drugs are chemically synthesized organic compounds with low molecular weight (<900 Daltons), whereas biologics are large, complex molecules derived from living organisms, such as proteins, peptides, antibodies, or nucleic acids. Amino acids often serve as the building blocks for biologics, contributing to their complex structures and functions. Small molecule drugs typically target intracellular enzymes, receptors, or ion channels, whereas biologics target extracellular or cell surface proteins, typically via binding interactions. Small molecule drugs are orally bioavailable and can be synthesized using chemical methods, while biologics are often administered via injection and produced using recombinant DNA technology in living cells. Small molecule drugs have simpler chemical structures, lower production costs, and shorter development timelines compared to biologics, which require specialized manufacturing processes, regulatory considerations, and quality control measures. Despite these differences, both small molecule and biologics development play critical roles in drug discovery and offer diverse therapeutic options for various diseases. 

Small molecules in drug discovery and development are characterized by several criteria that distinguish them from other types of compounds and pharmaceutical agents. Key criteria for small molecules include:

1. Low molecular weight: A molecular weight below 900 daltons, allowing them to penetrate cell membranes, exhibit favorable pharmacokinetic properties, and be orally bioavailable.
2. Simple chemical structure: Relatively simple chemical structures composed of carbon, hydrogen, oxygen, nitrogen, and occasionally other elements, facilitating chemical synthesis, modification, and optimization.
3. Drug-like properties:  Properties such as solubility, stability, permeability, and selectivity, enabling them to interact with specific biological targets and exert pharmacological effects.
4. Synthetic accessibility: Can be synthesized using chemical methods from commercially available starting materials or intermediates, allowing for efficient production, scalability, and chemical diversity.
5. Oral bioavailability: Often administered orally and can be absorbed through the gastrointestinal tract, reaching systemic circulation and target tissues to exert therapeutic effects.
6. Target specificity: Bind to specific molecular targets, such as enzymes, receptors, or ion channels, modulating their activity or function to achieve therapeutic outcomes.
7. Pharmaceutical development: Rigorous pharmaceutical development processes, including lead identification,  optimization, preclinical studies, and clinical trials, to demonstrate safety, efficacy, and regulatory compliance for market approval.

Overall, these criteria define small molecules as versatile and widely used compounds in drug discovery and development, offering numerous advantages for therapeutic intervention in various diseases.