Saquinavir mesylate is a different formulation, designed to be combined with another protease inhibitor that increases the bioavailability of the saquinavir.

History

Saquinavir was the first protease inhibitor (and sixth antiretroviral) approved by the Food and Drug Administration (FDA). It was approved on December 6, 1995, as Invirase®, a poorly-absorbed hard gel capsule which quickly led to viral resistance in many of the pioneer patients.

It was approved again on Nov 7, 1997 as Fortovase®, a soft gel capsule reformulated for improved bioavailability. The manufacturer, Roche, is alleged to have rushed Invirase® to market, but the conditions that prevailed at the time were very bad and there was a lot of pressure to produce products quickly.

Method of activity

When given alone, the HIV Protease Inhibitor (HPI) saquinavir has a very low oral bioavailability. In the clinic, it was found that the oral bioavailability of saquinavir significantly increases when patients also receive the HPI ritonavir. For patients, this has the major benefit that they can take less saquinavir, while maintaining sufficient saquinavir blood plasma levels to efficiently suppress the replication of HIV.

The mechanism behind this welcome observation was not directly known, but later it was determined that ritonavir inhibits the enzyme Cytochrome P450 3A4. Normally, this enzyme metabolizes saquinavir to an inactive form, but with the ritonavir inhibiting this enzyme, the saquinavir blood plasma levels increased considerably. Additionally, ritonavir also inhibits multidrug transporters, although to a much lower extent.

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Investigational drugs available - Invirase by Hoffmannn-LaRoche for AIDS and riluzole by Rhone-Poulenc Rorer for Lou Gehrig's disease in investigational
From FDA Consumer, 9/1/95

Two investigational drugs--one for HIV infection and the other for Lou Gehrig's disease--have joined the growing list of treatments FDA is making available while they're under study to patients with serious illness.

In a lottery system, saquinavir is available in an open-label study to 2,280 persons infected with HIV, the virus that causes AIDS. The drug is being distributed under the trade name Invirase by its manufacturer, Hoffmann-La Roche Inc. of Nutley, N.J.

It is a protease inhibitor, a new class of anti-AIDS drugs that block an enzyme necessary for HIV replication in the body. Saquinavir is the first protease inhibitor available outside controlled clinical trials. None have been approved for marketing.

Patients who have not benefited from existing anti-HIV therapy and who are not currently enrolled in saquinavir trials are eligible to be registered for the open label study by their physicians by calling (1-800) 332-2144.

FDA has granted riluzole, an investigational drug, Treatment IND (investigational new drug) status, making it available to certain patients with amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

Patients with ALS suffer progressive muscle weakness and paralysis. There is no cure, including riluzole.

One study has shown that at one year, 74 percent of patients taking riluzole were alive, compared to 58 percent on placebo. In another study showing survival rates at 18 months, 57 percent of patients taking the drug were alive, compared to 50 percent on placebo.

Riluzole is distributed by Rhone-Poulenc Rorer Inc. of Collegeville, Pa., under the trade name Rilutek.

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