Introduction: Drug Design, and Development

Drug design seeks to explain:
 Effects of biological compounds on the basis of molecular interaction in
terms of molecular structures or precisely the physico-chemical
properties of the molecules involved.
 Various processes by which the drugs usually produce their
pharmacological effects.
 How the drugs specifically react with the protoplasm to elicit a
particular pharmacological response.
 How the drugs usually get modified or detoxicated, metabolized or
eliminated by the organism.
 Probable relationship between biological activities with chemical
structure.

The ‘drug design’ in a broader sense implies random evaluation of synthetic as
well as natural products in bioassay systems, creation of newer drug molecules
based on biologically-active-prototypes derived from either plant or animal
kingdom, synthesis of congeners displaying interesting biological actions, the
basic concept of isosterism and bioisosterism, and finally precise design of a
drug to enable it to interact with a receptor site efficaciously.

What is a Drug

Drug is any substance presented for treating, curing or preventing disease in human beings or in animals.It may also be used for making a medical diagnosis or for restoring, correcting, or modifying physiological functions.
In medicinal chemistry, the chemist attempts to design and synthesize a
pharmaceutical agent that has a desired biological effect on the human body or
some other living system. Such a compound could also be called a 'drug', but
this is a word that many scientists dislike because society views the term with
suspicion.
With media headlines such as 'Drugs Menace’ or 'Drug Addiction Sweeps City
Streets’ this is hardly surprising.
•However, it suggests that a distinction can be drawn between drugs that are
used in medicine and drugs that are abused.
• Is this really true? Can we draw a neat line between 'good drugs' like penicillin
and 'bad drugs' like heroin?
• If so, how do we define what is meant by a good drug or a bad drug in the first
place? Where would we place a so called social drug like cannabis in this divide?
What about nicotine, or alcohol?

Medicinal chemistry unit 1 Drigs.

• Drugs – natural and synthetic alike – are chemicals used for medicinal purposes.
They interact with complex chemical systems of humans or animals.
• Medicinal chemistry is concerned with this complex interaction, focusing on the
organic and biochemical reactions of drug substances with their targets.
• Other important aspects are the synthesis and the analysis of drug substances. The
two latter aspects together are sometimes called Medicinal Chemistry, but the
synthesis of drugs is considered by some people – mainly chemists – to be part of
medicinal chemistry, denoting analytical aspects as pharmaceutical chemistry.
Objectives
The objective of Medicinal chemistry is to: Find, develop and improve drug substances that
cure or alleviate diseases and understand the causative and accompanying chemical
processes .
Medicinal chemistry is an interdisciplinary science covering a particularly wide domain
situated at the interface of organic chemistry with life sciences, such as biochemistry,
pharmacology, molecular biology, genetics, immunology, pharmacokinetics and toxicology
on one side, and chemistry-based disciplines such as physical chemistry, crystallography,
spectroscopy and computer-based techniques of simulation, data analysis and data
vis4ualization on the other side
Definition of medicinal chemistry (given by a IUPAC specialized commission)
Medicinal chemistry concerns the discovery, the development, the identification and
the interpretation of the mode of action of biologically active compounds at the
molecular level.
• Emphasis is put on drugs, but the interests of the medicinal chemist are not
restricted to drugs but include bioactive compounds in general.
• Medicinal chemistry is also concerned with the study, identification, and
synthesis of the metabolic products of various drugs and related compounds.
Medicinal chemistry is a chemistry-based discipline, involving aspects of
biological, medical and pharmaceutical sciences. It is concerned with the
invention, discovery, design, identification and preparation of biologically
active compounds, the study of their metabolism, the interpretation of their
mode of action at the molecular level and the construction of structure-
activity relationships (SARs).
Structure-activity relationship (SAR) is the relationship between chemical
structure and pharmacological activity for a series of compounds.
Lead compound is a compound that has a desirable biological activity with
therapeutic relevance, but typically has some shortcoming that is likely to be
overcome through the development of analogs.