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Monoclonal antibodies

Antibodies all made from a single clone of specialist cells used in both medical diagnostics and treatments

Active ingredient

The chemical which is the actual drug.

cell culture

Growing cells under controlled conditions, generally outside of their natural environment.

Heart failure

When the heart fails to pump blood effectively round the body as a result of the weakening or stiffening of the cardiac muscle or as a result of damaged heart valves.


Healing. A therapeutic treatment is one that works to treat a disease.


Proteins produced by the plasma cells (B cells, a type of white blood cell) of the immune system in response to a specific antigen..


How well the drug works


A killer disease until it was eradicated by 1980. Infected individuals are covered in skin sores and damage to body organs can cause death.


Chemical needed in very small amounts as part of a balanced diet to keep the body healthy.


A control that is used in drug trials. It looks exactly the same as the medicine under test but it does not contain the active ingredient.


Medicine that contains a dead or weakened pathogen. It stimulates the immune system so that the vaccinated person has an immunity against that particular disease.


A group of cells in an organism that are specialised to work together to carry out a particular function.


Legal protection that gives an inventor the right to be the only one to make and market their invention for the next 20 years.


A swelling made up of a mass of abnormal cells which keep multiplying in an uncontrolled way.




A large organ in the upper abdomen which manufactures, stores and breaks down substances as required by the body

Developing new medicines

In the past, many medicines and treatments were developed as a result of simple observations. People saw that eating citrus fruit prevented scurvy before they knew about vitamin C. Extracts of foxgloves were used to help people with heart failure long before cardiac muscle contraction and the interaction of digoxin with Na+/K+ ATPase was understood. Alexander Fleming observed that there were clear areas in a bacterial culture around patches of mould also growing in his culture plates. His deduction that the mould had produced something that killed the bacteria eventually led to the development of antibiotics, medicines that have saved millions of lives by curing diseases caused by bacteria.

In the past, people tried out new medicines without rigorous testing – anyone from individual scientists to condemned criminals, and from local children to family members were used as guinea pigs to see if a new treatment worked.

Edward Jenner vaccinating a boy

When Dr Edward Jenner first tried out his vaccine against smallpox on young James Phipps, no clinical trials had taken place. Eventually vaccines completely eradicated smallpox from the world. (painting by E.E. Hille Hillemacher, 1884)

Today, things are rather different … trailblazing scientists work to discover the molecules and develop the medicines needed to tackle the toughest diseases we face in society. Scientists like Dr James Black, who won the Nobel prize in 1988 for his discovery of beta blockers, the heart drugs that have changed millions of lives, and Drs Dennis Slamon and Axel Ullrich who worked on the development of Herceptin™ (trastuzumab), a drug which has improved the life expectancy of many women with breast cancer, have to understand the mechanisms of the diseases before they set out to find the molecules that will treat the symptoms or cure the problem. The process is long and hard – in the UK alone there are around 23,000 people working in research and development (R & D) in the pharmaceutical industry, hoping to step into the shoes of Sir Alexander Fleming or Louis Pasteur and discover or develop a new medicine that will change the lives of millions of people around the world.

The stages of developing a medicine

At the moment it takes over 12 years to develop a new medicine from the first scientific breakthrough to the point where it can be prescribed to the patients who need it. Each new medicine has to meet rigorous standards of quality, efficacy and safety that are laid down in law to protect the public and ensure that medicines are not released for use until they have been fully tested. Everyone wants to bring new medicines to patients faster, so scientists, doctors, and regulators are working together to develop better methods for drug development and accelerate this process.

The majority of potential medicines that begin the process of testing never make it to become a marketed drug prescribed to patients – only one or two useful medicines will result from every 10,000 chemicals that start the testing process. The rest will fall by the wayside at some stage in the testing process.

Key elements of the development process include:

The early stages: Firstly, we need to understand what goes wrong in the illness we want to treat. Scientists study a range of models, from cultured cells to animal models, to better understand the pathways and systems which malfunction in the disease. For example, if you want to develop a drug to treat a type of cancer, you may first study cancer cells to see which genes are mutated or which signalling pathways are disrupted in the cells, or you may look in an animal model to explore how cancer cells grow their own blood supply. The next step is to consider different types of chemical compounds or biological molecules and see which – if any – affect the pathways which have gone wrong. Scientists have many ways of identifying potential medicines. These include looking in huge chemical libraries, looking at natural body defences against disease, investigating chemicals in the natural world, adapting existing drugs and using computers to design new molecules.

Not all molecules which may improve or reverse the disease will make suitable medicines. The molecule also needs to:

  • be able to be delivered into the body (a delivery system)
  • be stable – there must be no risk of the drug changing into something harmful or become inactive before it works
  • be safe – it mustn’t cause damage to organs such as the liver, or have unpleasant side effects
  • be able to be made it in a very pure form
  • be able to be made in large quantities
  • be able to be made relatively cheaply

Scientists will start to think about these questions at this point, and will rule out any molecules which they know will not meet these criteria. Those which may be suitable will be taken forward to the next stages, to test if they really will treat the disease and if they really will make suitable medicines.

Rainforest Nomi Fruit


Noni fruit

Although many new medicines are designed on computers, areas of rich biodiversity such as rain forests are still seen as a source of medicines of the future. The noni fruit shown here is widely used to treat many diseases in South American countries such as Costa Rica – now scientists are investigating just how effective it really is.

For every molecule which makes the next stage, thousands are tried and rejected.

Patenting the compound: When scientists think a compound might make a useful medicine they patent the compound. A patent gives the inventor the right to be the only one to make and sell their invention for the next 20 years. It is effectively a reward for all the work that goes into discovering a possible new drug. The only problem is, with a potential new medicine, quite a few of those 20 years will be taken up with more testing!

In vitro screening: The new compound is tested on cell cultures, tissue cultures and whole organs in the lab to see if the compound does what the scientists thought it would and affects the disease in cells. Many chemicals fail at this stage because they don’t work in living tissue or because they are toxic. But if the compound passes these tests it becomes a proper drug candidate. It moves out of Research and into Development.

In Vitro testing

In vitro testing involves a lot of complex apparatus. At this stage many chemicals are still being investigated (Photo credit: James Gathany, CDC).

In vivo testing and preparation for clinical trials: It is at this stage of the development that the potential drug will be tested on animals, to find out how the drug works in a whole organism. We need to know if it gets taken into the cells, if it is changed chemically in the body and if it is excreted safely.

No-one wants to test on animals if it is not necessary. There are ethical challenges to working with animals, and it is additionally very expensive and time consuming. Therefore everyone in the pharmaceutical industry wants to see an end to animal testing as soon as possible: they are working towards the three Rs:

REPLACE the use of animals whenever possible
REDUCE the number of animals needed to a minimum
REFINE the tests to cause animals the least possible distress

Human trials – Phase 1 (first in human): Before you can try the new drug on people you have to get permission from the body (organisation) that regulates medicines and health care in the UK or across the European Union, proving to them that the results of all your testing so far means it appears safe to move on to human trials. If the regulators agree that the drug should be safe, the new drug will be given to 20-100 healthy volunteers in a Phase 1 trial, to check that the drug works as expected in the human body without causing unexpected side effects. Animal trials continue at the same time, looking at the effect of longer term use of the drug.

Human trials – Phase 2 (first in patients) If the drug makes it through Phase 1 human trials it goes into phase 2, the first time it is used with patients affected by the target disease. Between 100 and 500 patient volunteers are given the new drug. This is the first chance for scientists and doctors to see if the new medicine is likely to treat the disease in a real patient. The volunteer patients are closely monitored to find out whether the medicine works, as well as more information about the ideal dose, and any side effects.

Success at this stage means the new compound has a good chance of becoming a useful medicine.

Human trials – Phase 3 Before a new drug can be approved it must be given to thousands of patients with the target disease, to generate robust and convincing evidence that the medicine is effective in treating that disease. 1000-5000 volunteer patients take part in these trials for every medicine. In phase 3 trials, a new medicine is compared with either a placebo, or more commonly, with another medicine already used to treat the disease under investigation, so patients are not put at a disadvantage by being in the trial. The trials will be carried out ‘double blind’ - no-one knows whether an individual patient is getting the new medicine or the alternative medicine/placebo. A placebo may be a tablet or injection with no active ingredient, and so has no biological effect.

Patient taking a tablet

Medicine or placebo? In a double blind trial, neither the patient nor the doctor will know until the research period is over

Phase 3 trials are also used to fine tune the best dosage of the new medicine. Because the numbers involved are large, they also have a good chance of showing up rare adverse side effects.

Doctors and scientists must also prove that the new medicine is at least as good as anything already available to treat the target disease. If a new drug passes phase 3 trials a license to market the medicine will be applied for. This legal documentation has to be obtained before you can put a new drug on the market or use an existing drug to treat a different disease. Once a new drug has been granted a license it becomes available for doctors to prescribe for their patients.

Human trials – Phase 4 Even when a new medicine is being used to treat patients by doctors across the country and around the world, trials still continue to evaluate safety and effectiveness in the real world as well as for example to test the medicine in combination with other treatments.

Any adverse reactions suffered by patients are reported and recorded, to make sure that the benefits of using a medicine always outweigh the risks.

The typical cost of bringing a single new medicine through all the processes of development and testing to the point where it is licensed for use is around £1.15 billion.

The infographic below shows the stages a medicine has to pass through before it can be given to patients.

Timeline of medicine development

Timeline of medicine development

Chance or the evolving use of medicines

It sounds as if every medicine is carefully designed to carry out one particular therapeutic function – and in theory that is exactly what happens. But serendipity, or fortunate chance, also plays a part more often than you might imagine. In spite of centuries of study of the human body and the development of new technologies such as DNA sequencing we still do not fully understand how the human body works.

So drugs are designed to act in a particular way and treat a specific disease and laboratory, animal and human trials are run. The drug is marketed. Once it is in use, suddenly thousands or even millions of people use the new drug in the real world, a trial on an unimaginable scale. Sometimes drugs turn out to be not quite as good as we hoped at curing one thing – but unexpectedly effective at treating another. Here are a number of examples:

  • Anti-TNF (tumour necrosis factor) biologics are monoclonal antibodies originally developed to treat toxic shock. They failed Phase II trials because they just weren’t effective and indeed one major pharmaceutical company virtually gave away the molecule to another company. However, it was then discovered that the drugs were very effective at treating rheumatoid arthritis and other autoimmune conditions. More information on monoclonal antibodies is given in Detecting disease.
  • A drug developed to help treat high blood pressure and angina pain turned out to be relatively ineffective in clinical trials – but had an unexpected side effect in men. The drug we know as ViagraTM (sildenafil) restored erectile function in many impotent men, and is now one of the most prescribed drugs in the world.
  • Patient taking a tablet

    The unexpected side effect of sildenafil led to it becoming one of the most prescribed drugs – but not for the disease it was originally intended to treat.

  • Aspirin is a painkiller with anti-inflammatory properties, used for problems ranging from headaches to arthritis. However, doctors are discovering more and more potential uses for this cheap and widely used drug. For example it reduces the risk of blood clotting and may be used to reduce the risks of heart attacks and strokes in vulnerable people. Recent research suggests taking aspirin regularly may also reduce the risk of developing cancer or of cancer returning if you are affected by the disease. The jury is still out on that one.


Look into the history of medicines. Discover more about how peoples’ model of the causes of disease is linked to the way they try and cure them. Either:

  • Produce a timeline of some medical treatments from Ancient times to the 21st century.
  • Investigate and produce a poster or infographic charting the development of the treatment of one type of disease eg bacterial diseases, heart disease.
  • Write an article charting how models of disease have changed over time, and how this is reflected in the treatments that are developed.