Developing New Medicines (OCR Gateway GCSE Biology: Combined Science)

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Discovery of Potential New Medicines

  • Traditionally, drugs were extracted from plants and microorganisms
  • New drugs are being developed all the time by scientists at universities and drug companies around the world
    • Sophisticated computer modelling is done to identify 'candidate' molecules
      • Candidates are synthetic compounds that could be manufactured and could have the same or similar therapeutic effect on disease as existing drug compounds
  • A lot of the medication that we use today are based on chemicals extracted from plants
    • The heart drug digitalis originates from foxgloves
    • The painkiller aspirin originates from willow

  • Penicillin was discovered by Alexander Fleming from the Penicillium mould (a fungus)
    • Fleming left some petri dishes that had been contaminated with mould from the air and found that bacteria would not grow near the mould
    • He discovered that the mould (Penicillium notatum) was releasing a chemical (penicillin) that killed the bacteria surrounding it
  • Most new drugs are synthesised by chemists in the pharmaceutical industry
    • However, the starting point may still be a chemical extracted from a plant

Drugs From Plants Table Drugs from plants table, downloadable IGCSE & GCSE Biology revision notes

Testing of Potential New Medicines

  • All new drugs need to be tested and trialled before they can be used in patients
  • They are tested for:
    • Toxicity – does it have harmful side effects?
    • Efficacy – does the drug work?
    • Dose – what dose is the lowest that can be used and still have an effect?
  • The results of any testing are then peer-reviewed to make sure that the results are described accurately. The results would then be published in journals

Developing new drugs and medicines

  • Once a candidate drug has been identified and synthesised, preclinical testing is done in a laboratory using cells, tissues and live animals
  • Clinical trials use healthy volunteers and patients
  • Very low doses of the drug are given at the start of the clinical trial
  • If the drug is found to be safe, further clinical trials are carried out to find the optimum dose for the drug
  • In double-blind trials, some patients are given a placebo
    • Double-blind means that the doctors/nurses in direct contact with the trial patients are not aware of whether that patient is receiving the active drug or the placebo
      • This is controlled by other people who do not see the patients
    • This removes the chance of a doctor/ nurse influencing a patient unintentionally and displaying bias

The three stages of drug development

Preclinical testing

  • The drug is tested on cells in the lab
  • Computer models may also be used to simulate the metabolic pathways that may be taken by the drug
  • Efficacy (how effective the drug is as a therapy) and toxicity (harmful side effects) are tested at this stage

Whole organism testing

  • The drug is tested on animals to see the effect on a whole organism – all new medicines in the UK have to have tests on 2 different animals by law
  • Efficacy, toxicity and dosage are tested at this stage
  • The effect on unborn foetuses has to be assessed

Clinical trials

  • The drug is tested on human volunteers first, generally with a very low dose then increased
    • This is to make sure it is safe in a body that is working normally
  • The next stage is to test on patients with the condition
  • The patients are often split into two groups; one given the active drug the other given a placebo
    • This is called a double-blind study; neither the doctor nor the patient knows if the patient is getting the placebo or the active drug
  • Once the drug is found to be safe then the lowest effective dose is tested at this stage

Future medications

  • Pharmaceutical companies are always looking to find new medications
  • These include:
    • Vaccinations to different diseases
    • Antibiotics that have a different action on the bacteria, so that bacteria are not resistant to them
    • Painkillers with fewer side effects
    • Antiviral drugs that don't damage the body's tissues
  • Sources of these medications may be plants or microorganisms

Exam Tip

You should be able to describe the process of discovery and development of potential new medicines, including preclinical and clinical testing in the exam.

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Author: Phil

Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.