HEART DISEASE I: New Drugs May Provide ‘Natural’ Bypass
Preliminary studies have shown that two experimental drugs significantly reduce chest pain by stimulating the growth of new blood vessels. Both therapies trigger "therapeutic angiogenesis" -- the growth of narrow "collateral" blood vessels capable of carrying blood to parts of the heart cut off from the circulatory system by clogged arteries. A study published in today's issue of the journal Circulation found that 30 patients who received injections of a strand of DNA known as vegF, vascular endothelial growth factor, through a surgical incision in the chest, experienced less pain within three weeks of treatment (Altman, New York Times, 12/22). Conventional treatments such as bypass surgery, balloon or stent angioplasty and drug therapy had failed to reduce chest pain for the patients who underwent the hour-long procedure, which required a four-day hospital stay. "If it works in these patients, who are really pretty end-stage, I think it would likely work pretty effectively for (other) patients," said Dr. Jeffrey Isner, director of cardiovascular research at St. Elizabeth's Medical Center of Boston and the study's lead author (SoRelle, Houston Chronicle, 12/22). Isner also found that patients reported an average drop from 53.9 to 9.8 tablets of nitroglycerine per week needed to control angina. In a second study, Dr. Thomas-Joseph Stegmann of Fulda, Germany, administered injections of a protein known as FGF-1, fibroblast growth factor, to 20 patients and found that they also experienced reduced chest pain. Both doctors contend that heart scans, EKGs and coronary angiograms evaluated before and after treatment by doctors unaffiliated with the study provide objective evidence that therapeutic angiogenesis occurred.
Delivery In Question
Dr. Valentin Fuster, head of cardiology at Mount Sinai Medical Center, cautioned that definitive results will take years. Concerns about subjecting patients to "sham surgery" precluded use of a control group in both studies, allowing no evaluation of possible placebo effects. But other researchers are testing new ways to deliver the drugs that may not require surgery. Currently, vegF DNA must be injected directly into heart muscle because injecting it into veins would leave the DNA vulnerable to enzymes that could alter its structure. One approach would use a crippled virus as a vector for delivering vegF (Times, 12/22). A second approach, pioneered by scientists at the Texas Heart Institute, would thread a catheter through a patients' circulatory system to deliver the drug directly to the heart (Chronicle, 12/22).
Shortage Of Clot-Busting Drug
In separate news, a government embargo on a common clot-busting drug is forcing hospitals to ration supplies and use alternative treatments. The Food and Drug Administration last November ordered Abbott Laboratories to stop distributing the drug, known as urokinase, in light of fears that the kidney cells used to produce it were contaminated with hepatitis B. The Chicago-based company is the sole urokinase manufacturer in the United States (Everett, Ark ansas Democrat-Gazette, 12/22). "We'll be able to handle the problem," said John Coleman, pharmacy director of Loyola University Medical Center. "This is not life-threatening by any means, but it is an inconvenience." Coleman is advising doctors to use alternatives such as streptokinase and tissue plasminogen activator, TPA for short (Ritter, Chicago Sun-Times, 12/22). Urokinase dissolves blood clots and clears tubes used for chemotherapy and kidney dialysis. "It's the kind of drug that you use in an emergency situation. You can't really plan for it. From my standpoint and my colleagues', we hope this restriction will be removed fairly quickly" (AP/Dallas Morning News, 12/22).