FDA Approves Second Protease Inhibitor to Treat HIV

Date: March 1, 1996
Source: Food and Drug Administration (FDA)

The Food and Drug Administration today approved the second in a new class of AIDS drugs called protease inhibitors. Ritonavir, the new drug, received full approval for use alone or in combination with nucleoside analogue medications, such as AZT, in people with advanced HIV disease. Ritonavir also received accelerated approval for less advanced HIV disease. FDA approved the drug about two months after receiving its application for its marketing.

Even as we celebrate this milestone, we must recommit ourselves to President Clinton's goal of finding a cure," said HHS Secretary Donna E. Shalala. "We must also face the new challenge of providing life-prolonging medications to all who need them."

The review of ritonavir is the fastest approval of any AIDS drug so far -- 72 days," said Commissioner of Food and Drugs David A. Kessler, MD. "This drug provides real hope for patients with AIDS. Patients will live longer."

FDA based its approval for ritonavir on data showing that the drug not only improves laboratory markers, such as CD4 counts and viral load, but that it can reduce disease progression and mortality in people with advanced HIV disease.

Both protease inhibitors and nucleoside analogues chemically inhibit HIV development, although at different points in the replication process. FDA approved the first nucleoside analogue, AZT, in 1987 and the first protease inhibitor, saquinavir, in December 1995.

In clinical studies, ritonavir was studied alone and in combination with nucleoside analogues in HIV-infected people in various stages of disease. Each of these trials monitored changes in participants' CD4 cell counts, an indication of immune system strength and viral load, a measure of the amount of virus that can be detected in the bloodstream.

The largest of the studies also examined mortality rates in advanced HIV patients. The cumulative mortality rate among ritonavir participants was approximately 40 percent of that seen in the placebo-controlled participants, and ritonavir participants also experienced a 50 percent greater reduction in disease progression during the six months of the study.

Another study compared patient groups on ritonavir alone, ritonavir in combination with AZT, and AZT alone. Those in the groups taking ritonavir experienced a marked increase in their CD4 cell counts and a significant decrease in their viral load.

A third noncomparative study assigned 32 HIV-infected individuals to receive a triple combination of ritonavir plus AZT and ddC. Again, the result showed marked increases in CD4 counts and significant decreases in viral load.

For patients with less advanced HIV disease, none of these studies included clinical endpoints. Accelerated approval for ritonavir in this patient population requires that longer-term data be collected.

Accelerated approval is a regulatory mechanism under which FDA bases early marketing approval for a product on laboratory markers such as CD4 cell counts until information about clinical endpoints such as disease progression or mortality is available.

Adverse events associated with ritonavir treatment included diarrhea, nausea, vomiting, weakness, tingling, liver inflammation, elevation of lipid levels and taste disturbance. FDA has worked with the drug manufacturer to assure that potentially severe drug interactions with ritonavir are clearly highlighted in the package label and that patient education materials are made available to patients.

Abbott Laboratories is marketing ritonavir under the trade name Norvir.