Treating disease

• Antibiotic


  • A substance that kills or inhibits the growth of bacteria (no effect on viruses)

  • No effect on cells in the host organism

  • Produced by living organisms e.g. fungi
• Describe how ‘target’ molecules for new medicines can be identified

  • Comparisons of the genomes of unaffected individuals and those who are affected by a disease to identify potential disease-causing alleles

  • The alleles themselves or the proteins that they code for can be used as a target
• Stages of drug development :

  1. Screening for potential drugs
  2. Preclinical trials
  3. Clinical trials
  4. Approved by a medical agency
• Process of screening


  • Uses a machine to test large libraries of chemical substances

  • Enables the identification of pre-existing chemicals which may affect the target molecule

  • Chemicals may be altered, allowing scientists to produce a drug that reacts with target molecules in a specific way
• What do pre-clinical trials involve?

  • Drug tested on cultured human cells and using computer models to determine its toxicity (potential to cause damage) and efficiency

  • Drug then tested on live animals to establish a safe dose for humans and observe any side effects
• What happens during clinical testing?

  • The drug is first tested on healthy human volunteers to ensure that it is safe to use and has no other unwanted effects on the body

  • Drug then tested on patients with the disease to determine its efficiacy

  • Dosage is slowly increased until an upper limit is established

  • Optimum dosage is found
• Placebos 


  A substance that appears just like the real drug but has no effect on the recipient
• What is a blind trial?


  • The participants don’t know whether they are receiving the new drug or the placebo

  • Prevents the patient’s bias affecting the results
• What is a double-blind trial?


  • Neither the participants nor the doctors know who is receiving the new drug or the placebo

  • Prevents bias from doctors when analysing the results
• What is the problem associated with using placebos on patients with a disease?

  Is it ethical to prescribe a sick patient with a placebo knowing that it will not help their condition improve?
• What are monoclonal antibodies (mAbs)?


  • Antibodies that are clones of one parent cell

  • Specific to one type of antigen
• Describe how monoclonal antibodies are produced

  • Specific antigen injected into animal

  • B-lymphocytes producing complimentary antibodies are extracted

  • B-lymphocytes fuse with myeloma cells to form hybridoma cells

  • Hybridoma cells cultured

  • Monoclonal antibodies collected and purified
• What is a myeloma cell?

  A tumour cell
• What is a hybridoma cell?

  A cell that is created by fusing a B-lymphocyte cell with a cancerous myeloma cell
• Outline the uses of monoclonal antibodies

  • Detection of pathogens

  • Location of cancer cells and blood clots

  • Treatment of cancer

  • Used in pregnancy test kits
• What do pregnancy kits test for?

  hCG in urine
• What does a pregnancy test consist of?

  A stick containing monoclonal antibodies (mAbs) specific to hCG :

  • mAbs attached to a blue bead (free to move)

  • mAbs fixed to the test stick
• Describe what happens to the test stick if the woman is pregnant

  • hCG in urine binds to mAbs attached to a blue bead

  • mAbs with hCG diffuse up dipstick

  • mAbs fixed to the stick bind to hCG

  • Blue line forms
• Describe what happens to the test stick if the woman is not pregnant

  No hCG in urine so a blue line is not formed
• What is the advantage of using monoclonal antibodies to test for pathogens?

  • Specific to one particular antigen

  • Very accurate

  • Quick results
• What is hCG?


  • Human chorionic gonadotropin

  • A hormone produced during pregnancy that is detected in pregnancy tests
• Why can monoclonal antibodies be used to target cancer cells?

  • Cancer cells have specific antigens called ‘tumour markers’ on their membranes

  • mAbs are specific to one type of antigen so can be targeted to ‘tumour markers’ without damaging other cells
• Describe how monoclonal antibodies can be used to diagnose cancer

  • mAbs tagged to a radioactive substance

  • mAbs injected into a patient’s bloodstream

  • mAbs bind to ‘tumour markers’ on cancer cells

  • Emitted radiation is detected using a specialised scanner enabling doctors to determine the location of cancer cells
• How can monoclonal antibodies be used to target drugs to cancer cells?

  • mAbs attached to an anti-cancer drug

  • mAbs injected into the patient’s bloodstream

  • mAbs bind to ‘tumour markers’ on cancer cells

  • Anti-cancer drug destroys cancer cells
• Why are cancer treatments that use monoclonal antibodies favoured over traditional treatments?

  • Radiotherapy and chemotherapy target rapidly dividing cells

  • Healthy cells (e.g. hair follicle cells, bone marrow cells) are damaged as a consequence, producing unpleasant side effects

  • mAbs ONLY target cancer cells, reducing damage to normal cells
• How can monoclonal antibodies be used to locate blood clots?

  • mAbs tagged to a radioactive substance

  • mAbs target and bind to specific proteins in blood clots

  • Radiation emitted by mAbs is detected, enabling the location of blood clots to be identified