After decades of clinical failures and ethical controversy, could 2008 mark a new dawn for artificial blood? That鈥檚 the hope of HemoBioTech of Dallas, Texas, which claims to have developed a blood substitute that is safer than rival products. It plans to test the blood in surgical patients in India and the US later this year.
Like many previous blood substitutes designed to keep people alive when donor blood is unavailable, HemoTech is based on a form of oxygen-carrying haemoglobin extracted from cow blood, in which the haemoglobin molecules have been chemically bound together. This is necessary because free haemoglobin is toxic and can cause blood vessels to constrict, restricting blood flow. However, in many previous trials of blood substitutes, more deaths occurred among patients given the blood product than in controls receiving saline, suggesting that the toxicity problem had not been overcome.
HemoBioTech claims to have solved the problem by binding the haemoglobin molecules together with adenosine 鈥� a molecule that causes blood vessels to dilate. Originally developed at Texas Tech University in Lubbock, HemoTech was tested in 1991 in nine Zairian children with sickle-cell anaemia. When given as 25 per cent of blood volume, the substitute made blood vessels dilate, showed no kidney toxicity, caused no inflammation and even stimulated production of new red blood cells, says Arthur Bollon, chairman of HemoBioTech.
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Since then, the company claims to have conducted further animal and lab studies confirming these effects, but other researchers doubt whether HemoTech will fare any better than its rivals. 鈥淚 don鈥檛 consider the trial in Zaire a recommendation,鈥� says John Hess, director of the blood bank at the University of Maryland Medical Center in Baltimore. 鈥淎 lot of very bright people have been over these humps unsuccessfully before.鈥�
In 1998, for example, Baxter International of Deerfield, Illinois, abruptly halted a multimillion-dollar programme to develop a blood substitute called HemAssist, following trials in which 46 per cent of recipients died, compared with 17 per cent of controls.
More recently, Northfield Laboratories of Evanston, Illinois, courted controversy by testing its product, called PolyHeme, on unconscious trauma patients who couldn鈥檛 consent to the treatment (New 杏吧原创, 21 October 2006, p 8). Northfield is expected to publish the results of that trial in the near future.
