Drug Screening

Did you know that, on average, approximately 10,000 compounds are screened for every medicine that becomes a "blockbuster"?

• 10,000 compounds screened
• 1,000 compounds trialled in animals
• 100 compounds enter clinical trails
• 10 medicines are marketed, but not all recover costs
• 1 blockbuster

Did you know that in the mid 1980’s, 30-50 samples were screened, and it took 6 hours? Today we are screening 6,500 samples and it takes 2 hours. In this millennium we expect to be screening 50,000 plus samples in an hour.

Initial Testing

At this stage a basic product description is established, eg, physical characteristics, structure and stability.

Following initial synthesis the medicine is tested on animals, such as rabbits or rats, to determine whether the medicine appears to be safe, i.e. it is neither toxic, carcinogenic nor teratogenic.

These tests also allow the researchers to examine the pharmacodynamics of the medicine, eg. absorption, metabolism and excretion rates.

Clinical Trials, Phase I-V

There are five phases in clinical trials:

1. Phase I  trials are the first trials in humans. They are usually done in 10-20 healthy volunteers, where a single dose of the medicine is given. This is calculated from the animal data, and then titrated until therapeutic doses are achieved in humans. The objectives of Phase I trials are to assess the safety of gradually increasing doses, and to obtain basic pharmacokinetic information.
2. Phase II trials are trials in patients who have the disease that medicine is intended for. Approximately 100-200 patients are given the medicine over a 4-6 week period. They start with very low doses, and are closely monitored. The aim is to find the most suitable dose schedule. They provide information on clinical efficacy in relation to the concentration of the drug, and its metabolites, as well as information on adverse events. These studies also provide information on risk/benefit ratios as there is no such thing as absolute safety as all medicines have potential side effects. For example, AIDS medicines have very sever side effects but the alternative is death. During Phase II, the Go/No Go decision is made as to whether to continue trialling the medicine
3. Phase III trials test the medicine compared to either standard therapy or placebo. They involve treating 1000-3000 patients for periods up to 3 years, depending on the nature of the drug. During these trials, long term safety and efficacy data is obtained. These studies tend to be multinational studies, and are mainly what we undertake in NZ.
4. Phase IV and Phase V trials are often referred to as CDSP or Clinical Development Studies Programme. Phase IV is primarily for market penetration or market expansion, with ongoing long term safety data collection. Phase V trials are for new indications and repeats phases II and III. For example, male pattern baldness for finasteride (originally for benign enlarged prostates) and Paget’s Disease for alendronate (originally for osteoporosis).

WMA Prepared by Company

The company prepares what is known as a WMA – a world wide marketing application – or an NMA – a new medicine application. There are different requirements in different countries so generally two applications are prepared; one for the US and one for Europe. NZ uses the European application.

Depending on the medicine concerned, it may contain some 20 plus volumes of information that covers everything from discovery (drug screening) to manufacture.

WMA Submitted to Ministry of Health (MOH)

The WMA is submitted to the Ministry of Health (MOH) where the Medicine Assessment Advisory Committee (MAAC) reviews the package to decide whether the product is safe and efficacious, and what the indications of the product should be. During this process they may ask the company for further information.

A recent development has been the review of the Australian TGA Expert Report as part of the registration process. This has the potential to slow down the registration process as medicines were frequently registered in NZ before Australia.

Gazette Notice

Once a medicine has been approved by the Ministry of Health as being safe and efficacious, the company is advised that registration has been approved. The official notice of registration appears in the Gazette and then we can launch it, and sell it.

11-04-GEN-03-NZ-4249-O

TAPS NA8593
 

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