Developing New Medicines

Where do medicines come from, and how do we know they are safe? This lesson traces drugs from their origins — many were first found in plants and microorganisms — through the long process of testing and clinical trials that every new drug must pass before doctors can prescribe it. We finish with a Higher-tier / separate-science topic: monoclonal antibodies, identical antibodies made in the laboratory and used in pregnancy tests, diagnosis and targeted treatment. Understanding drug development connects the health strand of B6 to the wider story of how science is checked and trusted.

By the end of this lesson you should be able to give examples of drugs originally extracted from plants and microorganisms, describe the stages of preclinical testing and clinical trials, explain the terms placebo, double-blind and peer review, and (Higher/separate) explain how monoclonal antibodies are made and used.

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Where Do Drugs Come From?

Many of the medicines we rely on today were first discovered in plants and microorganisms. Three classic examples are required knowledge:

Drug	Original source	Use
Digitalis	The foxglove plant (Digitalis)	Treats heart conditions
Aspirin	A chemical from willow bark	Painkiller; reduces fever and inflammation
Penicillin	The Penicillium mould (a fungus)	The first widely used antibiotic

Penicillin has a famous discovery story. In 1928 Alexander Fleming noticed that a mould (Penicillium) had contaminated one of his bacterial culture plates, and that the bacteria would not grow near the mould — the mould was producing a substance that killed them. That substance was penicillin. It took other scientists, later, to extract and mass-produce it as a usable antibiotic.

Today, drugs are often synthesised by chemists in the laboratory, but the starting point for many is still a chemical first found in nature.

Exam Tip: Learn these three source–drug pairs cold: foxglove → digitalis (heart), willow → aspirin (painkiller), Penicillium mould → penicillin (antibiotic, Fleming). They are among the most reliably examined facts in this lesson.

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Testing and Trialling New Drugs

A new drug must be safe, must actually work (be effective), and must be given at the right dose. Before any new medicine reaches patients it goes through years of careful testing in two main phases.

Preclinical testing

Done before any human is involved:

1. The drug is tested on cells and tissues grown in the laboratory.
2. It is then tested on animals to check for toxicity (harmful effects) and to find roughly what dose might be needed.

Only drugs that pass these stages move on to humans.

Clinical trials

Tests on human volunteers:

3. The drug is first given at very low doses to a small number of healthy volunteers, mainly to check it is safe and to see how the body handles it.
4. If it is safe, it is given to patients who have the illness. Doctors adjust the dose to find the optimum dose — the dose that works best with the fewest side effects — and check that the drug is actually effective (efficacy).

Placebo, double-blind trials and peer review

To make trials fair and reliable, scientists use several safeguards:

• Placebo. A placebo looks identical to the real drug but contains no active ingredient. Comparing patients given the drug with patients given the placebo shows whether the drug really works, or whether people simply feel better because they think they are being treated (the "placebo effect").
• Double-blind trial. In a double-blind trial, neither the patient nor the doctor knows who is receiving the real drug and who is receiving the placebo until the trial ends. This prevents either of them being biased in how they report or judge the effects.
• Peer review. When the results are written up, other independent scientists check the work — its methods and conclusions — before it is published. Peer review helps to detect false claims and errors, so that doctors and the public can trust the findings.

Why each stage exists — and in that order

A common higher-level question asks you to justify the testing sequence rather than just list it. Each stage is there to answer a different question, and the order is deliberate so that the cheapest, safest tests come first and humans are only ever exposed once the obvious dangers have been ruled out.

• Cells and tissues first because they are cheap, fast and involve no animal or human risk; if the drug is toxic to cells, it is rejected before anything more costly begins.
• Animals next because a whole living body shows effects that isolated cells cannot — how the drug is absorbed, broken down and excreted, and whether it harms organs. This stage gives the first idea of a safe dose.
• Healthy volunteers before patients, and at very low doses, because the single most important question at this point is "is it safe in a human at all?". Starting low and in healthy people limits harm if there is an unexpected reaction; a sick patient might be put at greater risk, and their illness would make safety harder to judge.
• Patients last, because only people with the illness can show whether the drug actually works (its efficacy) and what the optimum dose is — the dose that gives the most benefit with the fewest side effects.

The animal-testing stage is sometimes asked about as an evaluation. On one side, testing on animals helps to identify drugs that are toxic or have harmful effects on whole-body systems before any human is exposed, which has prevented many dangerous medicines from reaching people. On the other side, some people object on ethical grounds — animals can suffer, and an animal's body does not always respond in exactly the same way as a human's, so a result is not a guarantee. In the UK, animal testing of new medicines is required by law but is also tightly regulated to limit suffering. A good evaluation states the benefit (safety screening), the objection (ethics and imperfect prediction), and a sensible conclusion (the testing is regulated and used because no fully reliable alternative yet exists).

The timescale and cost of drug development

Developing a new medicine is slow and very expensive. Bringing a drug from first discovery to the pharmacy typically takes well over ten years, and the great majority of candidate substances fail at some stage and never reach patients. The cost of researching, testing and trialling a single successful drug runs to many millions, partly because the cost of all the failures has to be covered too. This has real consequences: it helps explain why new antibiotics are developed so slowly (a point that matters for antibiotic resistance), and why drug companies focus on illnesses where they can recover their costs. It is also the reason the safeguards above matter so much — a drug that reached patients without proper testing could cause widespread harm, as has happened historically, so the long, careful process is the price of safety.

Exam Tip: Be precise about who gets the drug at each stage: healthy volunteers first (to test safety at low doses), then patients (to find the optimum dose and test efficacy). Mixing these up is a frequent error.

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Higher Tier / Separate Science Only: Monoclonal Antibodies

Higher tier only (separate-science / Biology B6.2): the following section on monoclonal antibodies is required for separate (triple) Biology and is not needed by Combined Science students. If you are taking Combined Science you can treat it as enrichment.