FDA Will Speed Use of Key AIDS Treatment : Experimental Drug Has Been Shown to Prevent Most Common Infection Threatening Patients

The U.S Food and Drug Administration will approve widespread distribution of an experimental drug that has been shown to prevent pneumocystis carinii pneumonia, the most common life-threatening infection seen in AIDS patients, agency officials said Tuesday.

The action, expected to be announced within days, will allow between 50,000 and 100,000 patients with AIDS or pre-AIDS immune system abnormalities to have access to aerosol pentamidine months before the drug receives final FDA approval to be marketed.

Important Advance Seen

Leading AIDS physicians hailed the decision as a significant therapeutic advance for AIDS patients, which may save money, decrease hospitalizations and perhaps tame one of the most feared complications of the disease. Wider distribution of aerosol pentamidine “is going to change the face of AIDS,” predicted one knowledgeable physician.

But unlike most experimental drugs, the patients will have to pay for aerosol pentamidine. The price is still to be determined and most health insurance programs, such as the federal Medicare and Medicaid programs, have yet to decide whether they will cover it.

“We have something that is fairly imminent,” said Don McLearn, an FDA spokesman, responding to an inquiry from The Times. McLearn confirmed that the plan will be approved.

The FDA decision is based on the still unannounced results of a 400-patient study in San Francisco. That study has shown that a monthly 300-milligram pentamidine treatment--administered as an aerosol spray--is highly effective both in preventing initial cases and recurrences of the deadly lung infection, sources familiar with the results said.

AIDS physicians with knowledge of the decision declined to be quoted by name until after it is formally announced. “The most common infection seen in AIDS will become a very uncommon infection,” one said. “It may make people live longer and live better lives because they are not going to be ill with recurrent bouts of pneumocystis.”

“It is really important,” said another leading AIDS physician, who pointed out that because aerosol pentamidine appears to have no serious side effects, it should be “easy to use” with AZT, the antiviral drug that has already been shown to prolong the life of some AIDS patients. About 50,000 patients with AIDS or pre-AIDS conditions are estimated to be taking AZT, according to FDA officials.

Under the FDA plan, LyphoMed Inc., of Rosemont, Ill., the drug’s manufacturer, will be granted a treatment IND (investigational new drug application) for aerosol pentamidine, the sources said. Details of the company’s distribution program are still being formulated.

The treatment IND program allows certain experimental drugs to be made available to seriously ill patients before the FDA grants final approval to sell the drug commercially.

In addition, companies granted treatment INDs are allowed to recover their costs by charging patients, although they may not promote or advertise the drug.

LyphoMed has marketed pentamidine, in an intravenous dosage form, since October, 1984, for the treatment of pneumocystis cases. The cost to pharmacies is about $100 a vial, although patients may be charged much more.

The drug company will now be able to make the drug available to two additional groups--AIDS patients who have already had pneumocystis cases as well as individuals who have never had pneumocystis but are infected with the human immunodeficiency virus and have “T-4” white blood cells counts of 200 or below, sources said.

Aerosol pentamidine already is believed to be used by thousands of AIDS patients, either in controlled clinical trials or under the supervision of their personal physicians. But, based on the results of the new San Francisco study, many have been using less effective doses of the medication and potentially less effective delivery systems.

The experimental treatments are given by dissolving pentamidine powder designed for intravenous administration in sterile water. The patient then inhales the medicine through an inexpensive device that disperses the medication into a fine mist.

The new 400-patient study was conducted by Dr. A. Bruce Montgomery, Dr. Gifford S. Leoung, other San Francisco General Hospital physicians and a group of community physicians in San Francisco who treat AIDS patients. Preliminary results were presented at the international AIDS meeting in Stockholm in June.

The study tested three doses of aerosol pentamidine over an 18-month period. It found that the most effective dose was the monthly 300-milligram treatment. The doses found to be less effective were 150 milligrams every two weeks, which is currently the most commonly used dose in the United States, and 30 milligrams every two weeks, sources said.

For patients with previous pneumocystis cases, the overall relapse rate at one year was about 10%, compared to the predicted relapse rate of 60%. Even patients who received the lowest dose of aerosol pentamidine had a relapse rate of only 30%.

Similar results were found for patients who had never had pneumocystis, although the difference between treatment groups was not as great for these patients because fewer of them became sick.

“The results became clear within the last several weeks,” one source said. “People who came down with pneumocystis tended to have mild cases and the mortality rate was very low, about 4%. This suggests some sort of protective role for all doses.”

Investigators and patients are being notified of the results and all the patients will be switched to the 300-milligram dose.

In addition, the sources said the study demonstrated the effectiveness of a delivery system known as the “Respigard II nebulizer,” which is one of several devices that have been used to administer aerosol pentamidine.

The FDA has granted treatment IND status to eight drugs, including the AIDS drugs trimetrexate and ganciclovir, since the program was started in 1987. In addition, AZT, or azidothymidine, was made available to more than 4,000 AIDS patients before it received final marketing approval in 1987.