Trialling drugs

Lesson objectives

To describe how new medicines are developed and the possible consequences if drugs are not

tested properly.

List some medical drugs.

How long do you think it takes to get a drug to market and what does it cost?

Answer10-12 years and US$500 million

Synthetic chemicals?

First tests in laboratory

Animal testing

Phase I: Testing on students!

Phase II: Testing on patients

Phase III: Final tests and licensing

Which diseases to treat?

Traditional remedies?

Drug Development

and Testing

Developing new drugs – Stage A

Researchers target a disease and develop ideas for

treatments.

Developing new drugs – Stage B

The search for possible drugs includes the computer design of

molecules and screening hundreds of thousands of

chemicals.

Developing new drugs – Stage C

Possible drugs are made (synthesised) in the lab.

Developing new drugs – Stage D

In vitro screening – the potential medicines are tested on cell

cultures, tissue cultures and isolated whole organs in the lab. Many

chemicals fail at this stage because they don’t work or are toxic.

Developing new drugs – Stage E

Animal testing – the small number of chemicals which make it this far are now tested on animals. This finds out more about how they

work in a whole living organism. It tells us what dose is needed and

sees if they cause any side-effects.

Developing new drugs – Stage F

Animal testing continues, looking at the effect of longer-

term use of the medicine.

Developing new drugs – Stage G

Clinical testing on humans begins with phase 1 on a small number of healthy volunteers. This looks at the safety of the medicine in

people.

Developing new drugs – Stage H

Human phase 2 trials run with a small number of the patients

suffering from the target disease. This is where scientists can really

begin to see if the drug will be safe, effective and if it works.

Developing new drugs – Stage I

Human phase 3 trials continue with a larger number of patients.

Developing new drugs – Stage J

When the medicine has passed all the tests set down in law, it will be granted a licence. Now your doctor can use the new medicine to treat

your illness.

Developing new drugs – Stage K

Once the medicine is in use, phase 4 trials continue. The medicine will be monitored for as long as patients use it. This makes sure it works and is as safe as possible.

Which diseases to treat? Doctors, politicians, drug company executives, members of the public and scientists all have an opinion. At some point money will be made available for the research into a disease cure to begin.

Traditional remedies? Where to start? Sometimes researchers will look at ‘traditional remedies’ to see if there is anything to learn. Plants, animals, bacteria and fungi have all been used as sources for new medicines.

Synthetic chemicals?Chemists produce a wide range of new chemicals every year. Many are screened for useful medical effects. Sometimes chemists use computer models to design a molecule which should cure an illness. Then they try to make it in the laboratory to see if it works as predicted.

Pfizer LtdPfizer Ltd

Phase I Human trials: testing on volunteersThe (very few) chemicals that pass the animal testing stage move on to the first human tests. These are done on healthy people – often students who get paid a small amount of money for volunteering. This stage checks the safety of the drug and looks for side effects. Animal tests continue, looking for any long term effects.

Phase II: Testing on patientsThe first ill people to get the drug are the Phase II volunteers. This is where scientists can really begin to see if the drug will be safe and effective.

Phase III: Final tests and licensingIf all goes well with phase II the trials move to phase III. Many more people are given the new drug. Some of the people in the phase III trial will be given dummy treatment so that doctors can compare the effect of the drug with already available medicines or nothing at all. By the end of a successful phase III the drug company submits its research to government bodies to ask for a licence to sell the drug.

Even once a medicine has been licensed for use it is still watched carefully for unexpected problems. These phase IV trials, where doctors report on any side effects suffered by their patients, continue as long as the medicine is used. Phase IV trials can involve hundreds of thousands of people.

Sometimes the trials throw up unexpected problems - medicines can even be withdrawn from use because serious problems appear! A drug company may decide to develop a new drug to replace the original one because it has fewer side effects. The whole process begins again!

Peninsula Medical SchoolPeninsula Medical School