Overview
Appendix A. Glossary
This glossary is designed as a practical companion for readers coming from different backgrounds, especially those new to medicinal chemistry, machine learning, or computational drug discovery. Its definitions are intentionally accessible and meant to serve as a quick refresher while moving through the book, helping bridge the many terms that appear across chemistry, biology, modeling, and the drug-development process.
Across the entries, the glossary covers a broad mix of core scientific concepts and modern AI methods. It explains key drug-discovery and pharmacology ideas such as potency, selectivity, bioavailability, ADMET, docking, virtual screening, protein structure, and target validation, while also introducing important machine-learning concepts like loss functions, optimization, clustering, calibration, embeddings, attention, graph neural networks, transformers, and generative models. Together, these terms show how the book connects molecular science with computational methods.
The glossary also emphasizes the practical realities of building AI-driven pipelines for discovery, including data quality, splitting strategies, model evaluation, uncertainty, applicability domain, and avoiding leakage or overfitting. It highlights advanced discovery workflows such as active learning, closed-loop optimization, de novo design, fragment-based design, protein and single-cell foundation models, targeted protein degradation, and therapeutic modalities including biologics, ASOs, cell therapies, and gene therapies. Overall, it frames the vocabulary needed to understand how modern AI systems are applied to real drug-discovery challenges.
FAQ
What is the purpose of the glossary in Appendix A?
The glossary is a quick reference to help readers with different backgrounds understand key terms used throughout the book, especially across medicinal chemistry, machine learning, computational chemistry, and drug discovery.
What does IC50 mean, and why is it important?
IC50 is the concentration of an inhibitor that reduces a biological activity by half under specific assay conditions. It is a common measure of potency, and lower IC50 values generally indicate a more potent compound.
How is ADMET related to drug discovery?
ADMET stands for Absorption, Distribution, Metabolism, Excretion, and Toxicity. These properties help determine whether a potent compound can become a viable drug by showing how it behaves in the body and whether it is safe.
What is the difference between a 505(b)(1) and 505(b)(2) regulatory pathway?
The 505(b)(1) pathway requires the applicant to provide full safety and efficacy data from its own studies. The 505(b)(2) pathway allows some supporting information to come from studies not conducted by the applicant, such as published literature or prior FDA findings.
What is the difference between potency and efficacy?
Potency refers to how much drug is needed to produce an effect, while efficacy refers to the maximum effect the drug can produce. A drug can be very potent without necessarily having high efficacy.
What is a binding pocket in a protein?
A binding pocket is a concave region on a protein surface where ligands bind. Its shape and chemical properties strongly influence whether a target is considered druggable.
What is the difference between Ki, koff, kon, and KD?
kon is the association rate constant, koff is the dissociation rate constant, and KD is the equilibrium dissociation constant. KD equals koff/kon and indicates binding affinity, where smaller KD values mean tighter binding. Ki is the equilibrium dissociation constant for an enzyme–inhibitor complex.
What is scaffold splitting and why is it used?
Scaffold splitting divides chemical datasets by molecular scaffolds rather than randomly. It creates a more challenging and realistic evaluation by testing whether a model can generalize to structurally different compounds.
What is a PROTAC?
A PROTAC is a heterobifunctional molecule with one ligand for a target protein and another for an E3 ubiquitin ligase, connected by a linker. It promotes target ubiquitination and degradation by the proteasome.
What is self-attention in a transformer model?
Self-attention is an attention mechanism in which each position in a sequence attends to all other positions in the same sequence. This lets the model capture relationships between distant elements and build rich contextual representations.