Developing New Medicines

Developing a new medicine is a long, expensive, and rigorous process. In this lesson you will learn about the drug development pipeline from discovery to approval, the importance of clinical trials, placebos, double-blind testing, and peer review. Understanding this process is essential for your Edexcel GCSE Biology exam.

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Where Do New Drugs Come From?

Many drugs have their origins in natural sources, while others are designed in the laboratory:

Natural Sources

Source	Example
Plants	Aspirin — originally extracted from willow bark (contains salicin). Digitalis — from foxglove; used to treat heart conditions.
Microorganisms	Penicillin — produced by the Penicillium mould, discovered by Alexander Fleming in 1928. Many other antibiotics come from soil bacteria and fungi.
Animals	Some painkillers are derived from animal venoms.

Synthetic Sources

• Modern pharmaceutical chemistry allows scientists to design drugs in the laboratory
• Computer modelling is used to predict how a molecule will interact with a target in the body
• Scientists can modify natural compounds to improve their effectiveness or reduce side effects

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The Drug Development Pipeline

Developing a new medicine typically takes 10–15 years and costs over £1 billion. The process involves multiple stages, each designed to ensure the drug is safe and effective.

Stage 1: Discovery and Target Identification

• Scientists identify a biological target (e.g. a receptor, enzyme, or protein involved in a disease)
• They search for or design a compound that interacts with this target
• Thousands of potential compounds may be screened using high-throughput techniques
• Most compounds will fail at this stage

Stage 2: Pre-clinical Testing

Pre-clinical testing is done before the drug is tested on humans.

Testing on cells and tissues (in vitro):

• The compound is tested on human cells and tissues grown in the laboratory
• This checks whether the drug has the desired effect on the target
• It also checks for obvious toxicity (does it kill cells it shouldn't?)

Testing on animals (in vivo):

• If cell testing is successful, the drug is tested on live animals
• This is done to:
  • Check how the drug behaves in a whole living organism
  • Test for toxicity — does it cause damage to organs?
  • Find the correct dosage — how much is needed and how much is too much?
  • Check for side effects — does it cause unexpected problems?
  • Test efficacy — does it work as expected in a living organism?
• Animal testing is legally required in the UK before a drug can be tested on humans
• It is a controversial topic — some people argue it is necessary for safety, while others believe it is unethical

Exam tip: Pre-clinical testing involves two phases: first on cells and tissues, then on animals. The purpose is to check for toxicity, efficacy, and dosage before any human testing.

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Stage 3: Clinical Trials (Testing on Humans)

If pre-clinical testing is successful, the drug moves to clinical trials — testing on human volunteers. Clinical trials are conducted in three phases:

Phase 1: Safety Trial

Feature	Detail
Participants	Small number of healthy volunteers (typically 20–100)
Purpose	Test for safety and side effects
What is measured	How the drug is absorbed, distributed, metabolised, and excreted by the body; any adverse reactions
Dosage	Start with very low doses, gradually increase

Phase 2: Efficacy and Dosage Trial

Feature	Detail
Participants	Small number of patients who have the target disease (typically 100–300)
Purpose	Test whether the drug works (efficacy) and find the optimal dosage
What is measured	Whether symptoms improve compared to a control group; best dose for maximum benefit with minimum side effects

Phase 3: Large-Scale Efficacy Trial

Feature	Detail
Participants	Large number of patients (typically 1,000–5,000 or more)
Purpose	Confirm efficacy on a large scale, monitor for rare side effects
What is measured	Statistical comparison between drug and control group; long-term effects
Duration	Can last several years

Stage 4: Regulatory Approval

• The pharmaceutical company submits all data to a regulatory body
• In the UK, this is the Medicines and Healthcare products Regulatory Agency (MHRA)
• The regulatory body reviews all evidence and decides whether to approve the drug for use
• Even after approval, the drug is monitored long-term for any unexpected side effects in the wider population (post-market surveillance or Phase 4)

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Placebos

A placebo is a dummy treatment that looks identical to the real drug but contains no active ingredient (e.g. a sugar pill or saline injection).

Why Use Placebos?

• Placebos are used as a control in clinical trials
• Some patients improve simply because they believe they are receiving treatment — this is the placebo effect
• By comparing the drug group with the placebo group, scientists can determine whether the drug is genuinely effective — i.e. that any improvement is due to the drug itself, not the placebo effect

Exam tip: The placebo must look, taste, and feel identical to the real drug so that participants cannot tell which group they are in. This ensures a fair test.

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Double-Blind Trials

In a double-blind trial:

• Neither the patient nor the doctor administering the treatment knows who is receiving the real drug and who is receiving the placebo
• The information is held by a third party and revealed only after the trial is complete

Why Double-Blind?

Problem it prevents	Explanation
Patient bias	If the patient knows they are taking the real drug, they might report feeling better due to the placebo effect, or report more side effects due to anxiety
Doctor/researcher bias	If the doctor knows which patient has the real drug, they might unconsciously interpret results differently (e.g. being more optimistic about the drug group's progress)

Double-blind trials produce the most reliable and unbiased results.

Exam tip: "Double-blind" means neither patient nor doctor knows who gets the drug vs placebo. This eliminates bias from both sides. If the question asks why, explain that it prevents the patient from experiencing the placebo effect and prevents the researcher from unconsciously influencing the results.

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Peer Review

Before the results of a clinical trial (or any scientific study) are published, they undergo peer review.

What Is Peer Review?

• The researchers submit their paper to a scientific journal
• Independent experts in the same field critically evaluate the study
• They check:
  • Is the methodology sound? (Was the study well designed?)
  • Are the results supported by the data?
  • Are the conclusions justified?
  • Were there any errors, bias, or conflicts of interest?
• If the paper passes peer review, it is published
• If not, it may be sent back for revisions or rejected

Why Is Peer Review Important?

• It acts as a quality control mechanism for science
• It helps prevent fraudulent or incorrect results from being published
• It ensures that findings are reproducible — other scientists should be able to repeat the experiment and get similar results
• It maintains public trust in scientific findings