Unit 1: New Drug Discovery and Development

Semester 8

BP804T

Introduction to New Drug Discovery and Development

This unit maps the monumental, billion-dollar journey of creating a medicine from scratch. It distinguishes the scientific stages of discovering a new molecule (Innovator Drug), testing it in animal models (Pre-clinical), and finally proving safety and efficacy in humans (Clinical Studies). It then pivots to the highly lucrative business of Generics—how competitor companies legally develop cheap, identical copies of these drugs once the original patents expire.

Syllabus & Topics

1Stages of Drug Discovery: A highly attritional process (starting with 10,000 compounds to get 1 approved drug). (1) Target Identification: Discovering the specific protein/gene causing a disease. (2) Target Validation: Proving that interacting with this target cures the disease. (3) Hit Discovery: Screening thousands of chemicals to find one that binds to the target. (4) Lead Optimization: Chemically modifying the ‘hit’ to improve its safety/efficacy, resulting in a ‘Candidate Drug’.
2Pre-clinical Studies (In-vivo / Animal Testing): Mandatory regulatory testing conducted strictly before human exposure. Purpose: To determine the drug’s fundamental pharmacokinetic profile (ADME) and absolute safety. Key tests: Acute, sub-acute, and chronic toxicity testing (to find the MTD – Maximum Tolerated Dose). Special toxicity: Teratogenicity (does it harm fetuses?), Mutagenicity (does it mutate DNA/Ames test?), Carcinogenicity (does it cause cancer?).
3Non-clinical Activities: Activities happening simultaneously with animal testing. Includes Preformulation profiling (solubility, degradation), inventing a scalable synthesis process for the Active Pharmaceutical Ingredient (API), and formulating the actual prototype dosage form (e.g., creating a stable tablet that won’t degrade on a pharmacy shelf).
4Clinical Studies (Human Trials): The most expensive and lengthy phase. Phase 1 (Human Pharmacology): Conducted on a small group (20-100) of HEALTHY volunteers. Objective: Determine basic safety, tolerated dosage range, and pharmacokinetics in humans. Phase 2 (Therapeutic Exploratory): Conducted on a larger group (100-300) of PATIENTS specifically suffering from the disease. Objective: Prove ‘Proof of Concept’ (does it actually cure the disease?) and determine the exact clinical dose. Phase 3 (Therapeutic Confirmatory): Massive, multi-center trials on thousands of patients (300-3000). Objective: Statistically confirm efficacy and monitor adverse reactions. Phase 4 (Post-Marketing Surveillance): Ongoing safety monitoring after the drug is launched in the general population to catch rare side effects.
5Innovator and Generics: Innovator Drug: A brand new chemical entity invented by an R&D company. The innovator is granted a 20-year patent monopoly to exclusively sell the drug at a high price to recover their massive (billion-dollar) research costs. Generic Drug: An identical copy of an innovator drug. Manufactured by a competitor company legally ONLY AFTER the innovator’s 20-year patent expires. It is legally required to be exactly identical in active ingredient, dosage form, safety, strength, and route of administration.
6Generic Drug Product Development: Because generics do not have to invent the molecule, their development is vastly cheaper and faster (taking 2-3 years). Their primary regulatory hurdle is NOT proving clinical efficacy again. Their sole hurdle is proving Bioequivalence: demonstrating that their cheap generic tablet dissolves in the stomach and enters the human bloodstream at the exact same rate and extent (Cmax and AUC) as the expensive Innovator tablet.

Learning Objectives

Map the NDDD Pipeline: Sequence the stages of New Drug Discovery correctly from ‘Target Identification’ through to ‘Lead Optimization’.

Differentiate Pre-clinical vs Clinical: Explain the distinct, legally mandated goals of testing a drug in rats (Pre-clinical acute toxicity) versus testing in humans.

Detail Clinical Phases: Distinguish between the primary objectives and subject profiles of Phase 1 clinical trials (healthy volunteers) versus Phase 2 trials (sick patients).

Define Generics vs. Innovators: Clearly articulate the legal, economic, and scientific differences between an Innovator drug and a Generic drug.

Understand Generic Equivalence: Explain the paramount concept of ‘Bioequivalence’ and why it is the sole regulatory requirement for approving a generic.

Exam Prep Questions

Q1. Why do Phase 1 clinical trials use “Healthy” volunteers instead of sick patients?

The primary objective of Phase 1 is strictly “Safety” and determining how the drug is metabolized by a normal human body, NOT whether it cures a disease. Sick patients have altered physiologies, liver impairment, or are taking other medications that would confound the pharmacokinetic data. Healthy young male volunteers provide a “clean slate” to accurately measure dangerous side effects and calculate fundamental safe dosing limits.

Q2. If a generic drug is exactly the same as the branded innovator drug, why is it 80% cheaper?

When Pfizer invents a new drug, they spend over a billion dollars on 15 years of failed experiments and massive clinical trials. Their high price reflects recovering those sunk costs. When a generic company (like Sun Pharma) makes a copy 20 years later, they completely skip the billion-dollar clinical trials. Their only cost is manufacturing the chemical (API) and running a small, cheap bioequivalence study on 30 people. Thus, they can sell it profitably for drastically less.

Q3. What is the difference between Teratogenicity and Carcinogenicity testing in pre-clinical studies?

Teratogenicity testing assesses if the drug crosses the placenta and causes physical birth defects or malformations in a developing fetus (this prevents tragedies like the Thalidomide disaster). Carcinogenicity testing assesses whether prolonged, lifetime exposure to the drug induces tumor growth or cancer in the animal model. Both are mandatory before the drug can be approved for widespread human use.