LYPHOMED's AEROSOLIZED PENTAMIDINE RECOMMENDED FOR APPROVAL FOR PRIMARY AND SECONDARY PROPHYLAXIS OF PCP; FISONS NDA NOT CONSIDERED BY ADVISORY COMMITTEE
Lyphomed's aerosolized pentamidine was unanimously recommended for approval for the prevention of Pneumocystis carinii pneumonia by FDA's Anti-Infective Drugs Advisory Committee on May 1. The advisory committee recommended that Lyphomed's aerosolized Pentam be approved for use in both secondary prophylaxis - patients who have already had at least one bout of PCP -- and primary prophylaxis -- HIV-infected individuals with a CD4 lymphocyte count less than or equal to 200 cells per cubic millimeter. The committee joined FDA in strongly urging the company to do follow-up Phase IV studies. Lyphomed has already submitted final protocols for two studies, which will be double-blind, randomized, controlled studies testing the current Treatment IND 300 mg once-monthly dose against a 500 mg once-monthly dose. The protocols submitted to FDA call for patient enrollment of 1,000 patients -- with patients with a history of PCP in one study and patients with CD4 counts less than or equal to 200 in the other trial. The advisory committee also suggested that Lyphomed conduct post-marketing studies in other immune-compromised individuals, such as cancer patients, organ transplant patients and other HIV-infected patients. Lyphomed presented the results of a 12-month study in 408 patients with aerosolized pentamidine, conducted by the San Francisco Community Consortium. In a comparison of 300 mg once-monthly to an active control of 30 mg once-monthly, the studies found that PCP events occurred 1.5 times as frequently in all patients receiving 30 mg as in patients receiving 300 mg. Approximately 50% of the patients in the San Francisco study were also taking AZT (Retrovir). Although the patients on AZT were not stratified in the study, presenter David Feigal, MD, University of San Francisco, said, a retrospective analysis of concomitant AZT and aerosolized pentamidine use was done. "These therapies are well tolerated together and it is quite possible to use these therapies concomitantly," Feigal remarked. The analysis shows that "there is about a two-fold reduction in PCP events comparing AZT [treated patients] to all [non-AZT] treatment arms combined," Feigal told the panel. In spite of the approval recommendation, FDA Anti-Viral Division Director Ellen Cooper, MD, noted that "the data in the NDA do not demonstrate efficacy for primary prophylaxis when these patients are analyzed alone." However, Cooper explained that FDA "feels it is reasonable to extend the indication" given the drug's efficacy in secondary prophylaxis "to include primary prophylaxis of high risk patients, and [it is] unreasonable to expect the sponsor to conduct a controlled trial against placebo or low dose drugs in high risk patients who have not yet experienced PCP." Fison's Pneumopent NDA, which is also pending at the agency, was not considered at the meeting. Fisons filed its NDA one week before the advisory committee meeting and hoped to be included in the agenda. FDA Commissioner Young told the meeting that "although Fisons has submitted a marketing application for this same drug, and will be speaking during the public session, their application is not on the table for discussion today." Cooper said her division has "not yet had time to review the Fisons application." In late March, Fisons filed a Treatment IND for Pneumopent, which is under extended FDA review. Fisons presented data from its double-blind placebo-controlled Canadian study. Out of a total of 162 patients, 84 received 60 mg pentamidine through the ultrasonic FISONeb nebulizer once every two weeks for a mean treatment duration of 3.7 months. Out of 32 confirmed cases of PCP, 27 cases occurred in the 78-patient placebo group, while 5 cases occurred in the treatment group. One potential distinguishing point between Lyphomed and Fisons' products are differences in efficiency of the Respirgard II and FISONeb nebulizers. Fisons maintains that their studies prove that an 80% reduction in PCP can be achieved with 120 mg of Pneumopent per month, less than half the 300 mg required for Lyphomed's Pentam. Fisons has pointed out to FDA that the reduction in dose would lead to cost savings of 50%. Lyphomed is currently charging $ 100 per 300 mg vial of Pentam plus approximately $ 20 for the nebulizer. FDA is planning to review the differences in nebulizers, shortly. "We are in the beginning of trying to organize . . . a workshop and symposium on the nebulizer issue," Anti-Viral Division Reviewer Carol Trapnell told the committee. "We are hoping to put together some kind of position paper or something -- we still don't know what yet -- to help people decide about different nebulizers for different drugs," Trapnell said. Although Lyphomed has a clear lead over Fisons in bringing aerosolized pentamidine to market, the issue of which product will profit from orphan exclusivity is still up in the air. "The issues that are related to the orphan drug status of the two applications and questions relating to exclusive marketing rights will also not be discussed today," Commissioner Young declared. "These are separate issues and they will be resolved at another date."
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