Treating disease

• Antibiotic


  A substance that kills or inhibits the growth of bacteria (no effect on viruses), produced by living organisms e.g. fungi, with no effect on cells in the host organism
• Identifying target molecules for new medicines


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

  2. 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. Approval by a medical agency
• Screening


  1. Uses a machine to test large libraries of chemical substances

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

  3. Chemicals may be altered, allowing scientists to produce a drug that reacts with target molecules in a specific way
• Preclinical trials


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

  2. Drug then tested on live animals to establish a safe dose for humans and observe any side effects
• Clinical testing


  1. 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

  2. Drug then tested on patients with the disease to determine its efficacy. Dosage is slowly increased until an upper limit is established. Optimum dosage is found.
• Placebo


  A substance that appears just like the real drug but has no effect on the recipient
• Blind trial


  Where the participants don't know whether they are receiving the new drug or the placebo, preventing the patient's bias affecting the results
• Double-blind trial


  Neither the participants nor the doctors know who is receiving the new drug or the placebo, preventing bias from doctors when analysing the results
• It is unethical to prescribe a sick patient with a placebo knowing that it will not help their condition improve
• Monoclonal antibodies (mAbs)


  Antibodies that are clones from one parent cell, specific to one type of antigen
• Production of monoclonal antibodies


  1. Specific antigen injected into an animal

  2. B-lymphocytes producing complementary antibodies extracted

  3. B-lymphocytes fuse with myeloma cells to form hybridoma cells

  4. Hybridoma cells cultured

  5. Monoclonal antibodies collected and purified
• Myeloma cells


  Type of tumour cell
• Uses of monoclonal antibodies


  • Detection of pathogens
  • Location of cancer cells and blood clots
  • Treatment of cancer
  • Used in pregnancy test kits
• Pregnancy test


  Tests for hCG in urine
• Pregnancy test procedure


  1. A stick containing monoclonal antibodies (mAbs) specific to hCG: mAbs attached to a blue bead (free to move), mAbs fixed to the test stick

  2. If 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

  3. If not pregnant, no hCG in urine so a blue line is not formed

  
• Advantages of using monoclonal antibodies to test for pathogens


  • Specific to one particular antigen
  • Very accurate
  • Quick results
• Tumour markers


  Specific antigens on the membranes of cancer cells
• Using monoclonal antibodies to diagnose cancer

  1. mAbs tagged to a radioactive substance

  2. mAbs injected into the patient's bloodstream

  3. mAbs bind to 'tumour markers' on cancer cells

  4. Emitted radiation is detected using a specialised scanner enabling doctors to determine the location of cancer cells
• Using monoclonal antibodies to target drugs to cancer cells


  1. mAbs attached to an anti-cancer drug

  2. mAbs injected into the patient's bloodstream

  3. mAbs bind to 'tumour markers' on cancer cells

  4. Anti-cancer drug destroys cancer cells
• Advantages of cancer treatments using monoclonal antibodies


  • Radiotherapy and chemotherapy target rapidly dividing cells, damaging healthy cells and producing unpleasant side effects
  • mAbs only target cancer cells, reducing damage to normal cells
• Using monoclonal antibodies to locate blood clots

  1. mAbs tagged to a radioactive substance

  2. mAbs target and bind to specific proteins in blood clots

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