A recent study published in the Journal of the American Medical Association assessing the safety of five hemoglobin-based blood substitutes indicates that recipients had a 30 percent greater risk of death than patients given whole blood transfusions; they were also nearly three times more likely to suffer heart attacks.

The researchers take the U.S. Food and Drug Administration (FDA) to task for failing to adequately review the data before giving the go-ahead for human clinical trials, noting that the risks were documented as long ago as 2000 and that dozens of deaths and heart attacks suffered during the subsequent trials could have been prevented. In the wake of the findings, study co-author Charles Natanson, a senior investigator with the U.S. National Institutes of Health's Critical Care Medicine Department, called for clinical trials to be halted until more studies are done on animals to prove their safety.

Natanson and his team reviewed results of studies on blood substitutes: Hemolink (made by Hemosol BioPharma, Inc., in Mississauga, Ontario), Hemopure (made by Biopure Corp., in Cambridge, Mass.), Hemospan (made by Sangart Inc., in San Diego, Calif.), Optro (made by Baxter Worldwide in Deerfield, Ill.) and PolyHeme (made by Northfield Laboratories, Inc., in Evanston, Ill.).

Rather than try to simulate all of the functions that blood performs, blood substitutes tend to focus on replacing hemoglobin, an iron-enriched protein in red blood cells that transports oxygen from the lungs to the rest of the body. Unfortunately, when hemoglobin is introduced directly into the bloodstream without the protection of red blood cells, the body will break down and remove the hemoglobin, a process that can be toxic to the kidneys, and which also narrows blood vessels, causing inflammation of surrounding tissue.

This past November, Scientific American Online took a look at the emerging market for blood substitutes. We primarily focused on work being done by Texas Tech University Health Sciences Center in Lubbock and by Dallas-based blood substitute developer HemoBioTech, Inc., (which was not studied by the NIH) to chemically modify bovine hemoglobin to suppress hemoglobin's inherent toxicity, improve blood flow, and spur the creation of new red blood cells.

The authors say their study was hindered by lack of access to information that they requested fromâ¬but was not supplied byâ¬blood substitute vendors such as Northfield, Baxter and Hemosol BioPharma. Their findings were based on information that they found on the Webâ¬through searches of the PubMed, EMBASE and Cochrane Library databases using the words "hemoglobin" and "blood substitutes" as well as information contained in FDA advisory committee meeting materials and Internet searches for company press releases.

In an attempt to remove such future roadblocks, the scientists are urging Congress to strip the FDA of its right to refuse to release corporate studies provided during product development. They say the agency will not even confirm the existence of an investigational or new drug, or a biologics license application until (and only if) the product is approvedâ¬even though the clinical trials could not have proceeded without its okay.

The also called on Congress to amend the Freedom of Information Act to bar federal agencies from withholding secret or confidential commercial information that could protect the public if released.

 

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