Fat capsules boost breast drug

Tamoxifen resistance can stop the drug working properly

Enclosing one of the world's best-known anti-cancer drugs in tiny fat droplets may allow it be used successfully for longer.

It could help thousands of women who have grown resistant to the breast cancer drug tamoxifen because they have been taking it for many months.

The majority of women with breast cancer have tumours which are likely to grow faster if exposed to the sex hormone oestrogen.

Tamoxifen blocks the hormone, and is prescribed to hundreds of thousands of women worldwide.

Many chemotherapies are made more potent by placing them in liposomes - tiny artificially-created sacs surrounded by a membrane.

To take an important drug like tamoxifen and substantially improve it...is a major step forward

Dr Iduna Fichtner, Max-Delbruck Center, Berlin

These can work as slow-release mechanisms, keeping the level of the drug in the body constant, or can be engineered to deliver their contents only to tissues containing a tumour.

Tamoxifen has been dubbed a "wonder-drug" and credited with much of the steep decline in breast cancer deaths in the UK over the past decade.

However, the majority of women taking tamoxifen long-term develop some sort of resistance to its effects.

This means that the same dose of the drug does not have as potent an effect on breast tissue as when they first started to take it.

Tumours which had stopped growing under the influence of the drug can start to grow again.

Boost the effect

Although boosting the dose of the drug would reproduce the original effect, the side-effects might be unjustifiable.

A team of researchers in Berlin conducted experiments to see if putting the drug in liposomes could help counter this effect.

In experiments in both laboratory cell cultures and mice with implanted tamoxifen-resistant human breast tumours, their liposomal version of the drug was able to have a far more pronounced effect than the standard drug.

Dr Iduna Flichtner, leading the research, said: "To take an important drug like tamoxifen and substantially improve it with a new formulation is a major step forward.

"We're anxious to see this developed further."

She said that while the reason the liposomes helped was not yet fully understood, one possibility could be because the membrane of each liposome slowed down the process by which the liver removed the drug from the bloodstream.

She told BBC News Online that human trials of the new liposomal tamoxifen should begin next year.

The market for the drug is estimated at $575m every year in the US.

However, a spokesman for the Cancer Research Campaign said that it was by no means certain that the effect would be reproduced in humans with breast cancer.

She said: "There are more and more alternatives to tamoxifen being developed.

"These are likely to be at least as effective and have a better toxicity profile - for example, there may be less risk of endometrial cancer."