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

• 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

• 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