PERFLUOROCHEMICALS are fluorine-containing compounds, many of which are able to carry large quantities of oxygen. Fluosol-DA, a patented emulsion of two such compounds first developed in Japan, is currently undergoing human clinical trials for a variety of potential uses. Among them:
As an "ischemic modifier" in conjunction with balloon angioplasty: Balloon angioplasty, in which a tiny balloon is inserted and temporarily inflated inside a coronary artery, has become a popular method of unclogging blood vessels that bring oxygen to the heart. During the procedure, however, blood flow to the heart is blocked -- limiting the time allowed for the delicate operation. Fluosol is being used experimentally in animals to oxygenate the heart during induced "ischemia," or lack of oxygen. It is hoped that the technique will allow physicians to leave the balloon inflated longer, thereby prolonging the effects of the treatment.
"Fluosol has a very small particle size -- much, much smaller than any red blood cell," says George Groveman of Alpha Therapeutic, which holds the U.S. license to manufacture and test Fluosol. "A Fluosol particle is about one-70th the size of a red blood cell," which allows Fluosol to go "where the delivery of blood is either not possible or is submaximal."
As a cancer-therapy enhancer: Nearly all solid cancer tumors contain cells that are extremely low in oxygen -- a property that makes them resistant to both radiation therapy and chemotherapy. "Both modes of therapy require high levels of intracellular oxygen to exert their maximum effect," Groveman says, "so by oxygenating a tumor with Fluosol we are able to sensitize it to radiation or to chemotherapy." Advanced clinical trials have been "very encouraging," he says.
As a preventive of reperfusion injury: Due to a process called free-radical superoxidation, cells just behind a recently reopened clot are often injured with the first rush (reperfusion) of oxygenated blood. But the damaging reaction is apparently catalyzed by white blood cells. Researchers hope that an acellular oxygen carrier such as Fluosol may be useful as a reperfusion fluid immediately following clot-dissolving therapy.
As a cardioprotective agent during heart attack: Animal trials suggest that Fluosol may protect heart muscle if administered during a heart attack. "We're still looking at what kind of 'cocktail' would be involved," Groveman says. "But the dog trials that we've done suggest that you can salvage a third to two-thirds of that area of heart muscle that would have been infarcted" -- that is, injured by lack of oxygen.
Some researchers believe that Fluosol may also prove useful for keeping donor organs oxygenated while they are readied for transplant. And it may be an effective treatment for cerebral ischemia, in which an injury results in an interruption of oxygen flow to certain parts of the brain. A Fluosol-like oxygen carrier may even get approval as a systemic "hemoglobin substitute" for patients with seriously low levels of the natural oxygen carrier.