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Executive Summary

Viratek's Virazole (ribavirin), the first antiviral approved by FDA for severe lower respiratory infections caused by respiratory syncytial virus, will be targeted to a potential U.S. infant and pediatric population of 95,000-100,000 hospitalized patients per year. The aerosol product was approved by FDA Jan. 2. Labeling states that ribavirin is "indicated in the treatment of carefully selected hospitalized infants and young children with severe lower respiratory tract infections due to respiratory syncytial virus (RSV)". Viratek's parent company, ICN, estimated in introductory material on the antiviral that "in the U.S. alone, over 800,000 infants are infected by RSV infections annually," of which "95,000 to 143,000 are hospitalized." The company added that "an estimated 5% of hospitalized infants die" from respiratory syncytial virus. For the treatment of RSV, Virazole is administered through a small particle aerosol generator (SPAG) which delivers the drug as a fine mist directly to the lungs. The SPAG was developed by ICN and Baylor University. ICN explains that the patient is kept in a tent or hood and the drug is given continuously for up to 18 hours per dose "for at least three and no more than seven days." Virazole is a synthetic analog of guanosine, a naturally occurring chemical required by cells for RNA and protein production. The drug was launched the date of approval. It is being marketed by ICN's subsidiary, SPI Pharmaceuticals. Price to whslrs. is $229 for 6 gm of drug per 100 ml vial. The U.S. approval for RSV culminates the first stage of a 15-year development project by ICN for ribavirin for the U.S. market. The NDA for ribavirin in RSV was submitted to FDA over three years ago, in September 1982. ICN notes the drug has been sold for over 10 years all over the world. "Its efficacy in combating influenza A and B, parainfluenza, measles, chickenpox, herpes simplex, herpes zoster, hepatitis A, and hemorrhagic fever, among other diseases, is evidence of its broad spectrum utility," ICN maintains. ICN is continuing to evaluate the safety and efficacy of Virazole aerosol against influenza, parainfluenza and adenovirus infections. ICN said in 1986 it will file supplemental NDAs for adult influenza and conduct a trial of 350 patients with AIDS related complex in eight medical centers. The AIDS research is being conducted with Eastman Kodak ("The Pink Sheet" Oct. 7, T&G-7). The company noted that it will continue post-marketing surveillance of infants and children treated with ribavirin in controlled clinical trials until the children reach age seven. ICN stated that "as of this time, a two-year follow-up has failed to demonstrate any delayed detrimental effects of Virazole aerosol on the respiratory tracts of treated children." The ICN approval may be a precursor to one of the initial indications for interferon. Since May 1983, Schering-Plough has had an application for alpha interferon at FDA for prophylaxis of the common cold. The ribavirin approval, and postmarketing studies, may prove a precedent for FDA's review of interferon. The ICN product's acceptance in the medical community may indicate the interest in antiviral treatment of respiratory diseases. The adverse reactions section of the labeling states: "Approximately 200 patients have been treated with ribavirin aerosol in controlled or uncontrolled clinical studies. Pulmonary function significantly deteriorated during ribavirin aerosol treatment in six of six adults with chronic obstructive lung disease and in four of six asthmatic adults. Dyspnea and chest soreness were also reported in the latter group. Minor abnormalities in pulmonary function were also seen in healthy adult volunteers." With regard to use in infants, the labeling notes that "several serious adverse events occurred in severely ill infants with life-threatening underlying diseases, many of whom required assisted ventilation. The role of ribavirin aerosol in these events is indeterminate." Reactions included "worsening of respiratory status, bacterial pneumonia, pneumothorax, apnea, and ventilator dependence, cardiac arrest, hypotension, and digitalis toxicity." A bold-faced boxed warning at the beginning of the prescribing information states that ribavirin aerosol should not be used for infants requiring assisted ventilation. The labeling states that "deterioration of respiratory function has been associated with ribavirin use in infants, and in adults with chronic obstructive lung disease or asthma." ICN says it also has three anticancer agents "now in various stages of study." The agents are 3-deazaguaine, tiazofurin, and uricytin. Roland Robins, the Director of Molecular Research at ICN's Nucleic Acid Research Institute, is credited by the company for being "responsible for the design and synthesis of ribavirin, allupurinol" and two of the cancer research products, 3-deazaguaine and tiazofurin. The two cancer agents are licensed to Warner-Lambert. The company further stated: "We have several other antiviral agents, antiparasitic agents and immune modulators that are currently being developed." VIRAZOLE LABELING INDICATIONS The following is excerpted from approved labeling for Virazole (ribavirin). Indications and Usage: Ribavirin aerosol is indicated in the treatment of carefully selected hospitalized infants and young children with severe lower respiratory tract infections due to respiratory syncytial virus (RSV). In two placebo controlled trials in infants hospitalized with RSV lower respiratory tract infection, ribavirin aerosol treatment had a therapeutic effect, as judged by the reduction by treatment day 3 of severity of clinical manifestations of disease. Virus titers in respiratory secretions were also significantly reduced with ribavirin in one of these studies. Only severe RSV lower respiratory tract infection is to be treated with ribavirin aerosol. The vast majority of infants and children with RSV infection have no lower respiratory tract disease or have disease that is mild, self-limited, and does not require hospitalization or antiviral treatment. Many children with mild lower respiratory tract involvement will require shorter hospitalization than would be required for a full course or ribavirin aerosol (3 to 7 days) and should not be treated with the drug. Thus the decision to treat with ribavirin aerosol should be based on the severity of the RSV infection. The presence of an underlying condition such as prematurity or cardiopulmonary disease may increase the severity of the infection and its risk to the patient. High risk infants and young children with these underlying conditions may benefit from ribavirin treatment, although efficacy has been evaluated in only a small number of such patients. Ribavirin aerosol treatment must be accompanied by and does not replace standard supportive respiratory and fluid management for infants and children with severe respiratory tract infection.

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