Image caption A graphic by its makers of the MP4OX compound being tested in clinical trials

A London hospital is leading a worldwide trial of a drug designed to aid the recovery of patients with heavy blood loss.

MP4OX is made from expired blood stocks and seeks to replicate the function of red blood cells in carrying oxygen around the body.

It is being given to patients with heavy blood loss in 56 centres around the world.

The Royal London Hospital is leading the clinical trials.

The initial trial seemed to show that people got out of hospital much quicker than patients who hadn't had the drug Prof Karm Brohi, The Royal London Hospital

MP4OX has been developed by US pharmaceutical company Sangart, which is funding the trial, and is a haemoglobin-based product processed from expired blood transfusion stocks.

Haemoglobin molecules are the proteins in red blood cells which carry oxygen to muscles and tissue around the body.

In trauma patients who have undergone heavy blood loss, these molecules are in short supply, and its makers claim MP4OX can deliver an oxygen boost to organs and tissue in the body, reducing the risk of organ failure.

They say it carries no infection risk and can be given safely to all patients.

Prof Karim Brohi, of the Barts and The Royal London Hospital, is leading the trials.

"We're giving it to people who been severely injured in car crashes, have fallen out of a window, been stabbed etc," he told BBC News.

Media playback is unsupported on your device Media caption Claire Rourke of the Royal London Hospital explains how the MP4OX trial is being conducted

"Basically it's a drug which takes up oxygen and delivers it to cells which are starved of oxygen because there's not enough blood going around the body."

The drug has already been tested in a pilot trial of 50 patients, which appeared to show the drug was safe.

That pilot has now been extended to a worldwide trial encompassing some 360 patients, to further test its safety and efficacy. That trial is now approaching completion although the researchers have yet to process any of the results.

"In the initial trial, it seemed to show that people got out of hospital much quicker than patients who hadn't had the drug," he said.

"It was a small trial with lots of room for error, but there was a pretty strong signal that there were a lot more patients who were alive and out of hospital at 28 days compared to the ones who hadn't had the drug."

However, he stressed that it was only after results from the extended "Phase 2b" trial were in, that they would know how much promise the drug showed.

The trial is what is know as "randomised", with patients randomly prescribed the drug or a placebo according to instructions enclosed in a sealed paper envelope. The drug is also wrapped up in a black bag in the lab prior to delivery to the ward or theatre, so neither clinicians nor patient know what they are being given.

These measures are designed to improve the accuracy and impartiality of results.

The trial is one of many projects around the world in which researchers are trying to replicate some of the functions of blood.

A recent BBC Radio 4 documentary looked at some of the attempts, past and present, to create artificial blood products, including efforts to develop haemoglobin treatments from E.coli bacteria and from stem cells.

But Prof Brohi says MP4OX should not be regarded as "artificial blood".

"This isn't a substitute for blood because we give less than a Coke can's worth to each patient - while these patients may have lost up to five litres of blood - so in no way is it a substitute for giving red blood cells to patients," he said.

"What it's doing is augmenting the ability of those red blood cells to do their job."