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ASTRA'S FOSCAVIR SURVIVAL IMPROVEMENT COMPARED TO SYNTEX' CYTOVENE

Executive Summary

ASTRA'S FOSCAVIR SURVIVAL IMPROVEMENT COMPARED TO SYNTEX' CYTOVENE in AIDS patients with cytomegalovirus retinitis was shown in a National Eye Institute-sponsored study that has been halted as a result of the findings. At an NEI press conference Oct. 21, principal investigator Douglas Jabs, MD, Johns Hopkins School of Medicine, reported that patients treated with Foscavir (foscarnet) in the Foscarnet-Ganciclovir Cytomegalovirus Retinitis Trial lived an average of 12.6 months compared to 8.5 months for patients receiving Cytovene (ganciclovir). The study results suggest that "foscarnet for many AIDS patients may be a preferrable initial treatment [compared to ganciclovir] for CMV retinitis," Jabs said. Ironically, FDA had warned Astra against making safety and efficacy comparisons to ganciclovir in promotional materials when foscarnet was approved on Sept. 27 ("The Pink Sheet" Sept. 30, T&G-1). Speaking at the press conference, National Institutes of Health Director Bernadine Healy, MD, stressed the importance of disseminating information on a therapy that improves "quality as well as quantity of life." NIH has issued a clinical alert describing the study results to more than 40,000 physicians and other professionals who take care of AIDS patients. CMV retinitis is estimated to occur in 20%-25% of AIDS patients. NEI estimates the CMV retinitis population in the U.S. at 47,000 patients, but some researchers and Astra believe the number is closer to 20,000-30,000 patients. Ganciclovir, which has been available since June 1989, generated sales in fiscal 1991 (ended July 31) of $ 53.6 mil. Foscavir therapy costs approximately $ 22,000 annually based on the wholesale price of the drug, with an estimated daily cost of $ 58 for the maintenance dose of 90 mg/kg. One year of ganciclovir therapy, based on the price to wholesalers, is roughly $ 8,000 per year. Some AIDS activist groups hope that the potential for wider use of foscarnet will bring down the drug's price. Astra said it will not consider pricing changes until results from the trial formally have been incorporated into labeling. Jabs cautioned that the study findings should not be interpreted as a blanket recommendation that all CMV retinitis patients be started on foscarnet therapy. He noted that in a subgroup of patients with impaired renal function (creatinine clearance 1.2 ml/min/kg) ganciclovir was associated with greater survival and that patients who fit that criteria should receive ganciclovir as initial therapy. Median survival for patients with compromised renal function was approximately eight months in the ganciclovir group and four months for the foscarnet-treated patients. The trial, begun in March 1990, was halted on Oct. 7 by the study's independent Policy and Data Monitoring Board, which concluded that patients on foscarnet therapy were living an average four months longer than those on ganciclovir therapy. The study is part of NEI's Studies of Ocular Complications of AIDS (SOCA) collaborative research project. The study findings have been submitted for publication in a major medical journal. The study enrolled 240 AIDS patients who had not been treated previously for CMV retinitis. Patients received either 60 mg/kg of foscarnet every eight hours, or 5 mg/kg of ganciclovir every 12 hours. Following the induction phase, patients were given maintenance doses of 90 mg/kg daily of foscarnet and 5 mg/kg daily of ganciclovir. Both treatments require intravenous administration. Patients receiving foscarnet showed improved survival when compared to ganciclovir irrespective of the type of antiretroviral therapy they were receiving. In fact, a subset of patients who did not receive any concurrent antiretroviral therapy still faired better on foscarnet. Most patients in the study received either AZT, ddl or ddC. Foscarnet and ganciclovir were found to be identical in terms of preventing CMV retinitis progression and preserving visual function, Jabs said. Side effects similar to those previously reported for each drug were seen in the trial. Foscarnet therapy was associated with decreased renal function, nausea and metabolic abnormalities, which could lead to seizures. Ganciclovir's major toxicity is myelosuppression, which makes concomitant therapy with AZT difficult. About one-third of patients started on foscarnet were switched to ganciclovir during the study because of toxicity. In a same-day statement, Cytovene manufacturer Syntex contended that the trial was designed primarily to study the effects of foscarnet and ganciclovir on the progression of CMV retinitis. "The trial was not designed in such a way as to optimally compare survival," Syntex asserted. The company maintains that because antiretroviral therapy was not controlled for in the study it is difficult to compare survival between the two groups. In addition, the company argued "the mortality analysis was performed as if patients continued on intially assigned therapy throughout the duration of the study." The study's researchers maintain that patients who received ganciclovir throughout the study faired much worse than those receiving foscarnet throughout the study or those patients that, because they switched therapies, received both drugs during the trial. Syntex said it will discuss the implications of the trial results with FDA.
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