Blood Substitutes
Blood substitutes have been studied for at least 70 years; the search continues. All of the first and second generations of these replacements for human blood have been discontinued. Some of the third generation products have also been discontinued. There are a few still being studied.
One of these is PolyHeme, a pyridoxylated, polymerized hemoglobin with a half-life of about 24 hours and a refrigerated shelf life longer than 12 months. Data indicate that fewer allogenic red blood cell transfusions are needed with these products; a study a few years ago showed quite promising data in patients whose hemoglobin was less than 1.0 gm/dL (sic) -- 75 percent of those treated with PolyHeme survived versus 16 percent of historical controls with the same level.
Recently the data from a multi-site Phase III trial of more than 700 patients indicated that although there were more adverse events in the PolyHeme group, the benefit-to-risk ratio of PolyHeme is favorable when blood is needed but not available.
The other first-generation polymerized hemoglobin product, Hemopure, a polymerized form of bovine hemoglobin an intravascular half-life of 8-23 hours and a shelf life of 36 months at room temperature. Hemopure is approved in South Africa for the treatment of adult surgical patients who are acutely anemic. In the United States, phase II trials have been put on hold due to safety issues. Biopure is currently addressing the FDA's questions regarding safety and efficacy of the product.
Considering the rather severe problems with the early blood substitutes, we are making progress. The data with these two products have been more than a little encouraging. We will keep you posted on developments.