Camvia (maribavir) disease in the populations at risk, elevations of liver enzymes in 8 Cytomegalovirus (CMV) is a common and in Europe in November 2007 percent of our patients. As I am virus that infects most of the adult for cytomegalovirus disease in writing this letter at the end of population. In the U.S., at least 80 patients with impaired cell-mediated March 2008, there is yet much work percent of the population is infected immunity. These designations to be done, including meeting with the with the virus by the time they provide important financial and U.S. Food and Drug Administration reach adulthood. For most people, exclusivity opportunities to elucidate any possible path thankfully, a healthy immune system to ViroPharma. forward for the compound. For keeps the virus at bay. However, CMV this great medical need, this is can cause severe and potentially We are currently enrolling in two time and energy well spent. deadly disease including pneumonia, international Phase 3 studies – one in gastroenteritis, and meningoen- patients undergoing stem cell trans- NTCD cephalitis (infection of the brain plant, the other in liver transplant Hospital acquired infections (HAI) and the membrane surrounding patients – with the goal of filing our are on the rise throughout the U.S., the brain and spinal cord) in initial NDA in 2009 and our initial accounting for approximately 1.7 immunosuppressed populations, MAA in the European Union in a million infections and 99,000 deaths including transplant patients. similar time frame. As we interact per year. One of the most common with our numerous clinical trial sites and dangerous HAIs is caused by C. Each year, more than 100,000 in North America and Europe, we difficile. Today’s C. difficile infection transplants are performed throughout continue to see great enthusiasm for (CDI) is very different from the disease the world. For each of these patients, the drug. Our preparations for launch of the past. Institutions have experi- the most common and often lethal have already begun, encompassing enced not only increased rates of viral illness is CMV infection and global initiatives by our marketing, disease, but also increased virulence disease. While anti-CMV agents medical affairs, and public relations/ and severity. And while the disease are available, they are often used advocacy organizations. For transplant is well treated by a small number sparingly due to many well-known physicians, maribavir may represent of drugs including Vancocin,® the safety drawbacks. Typically these the first new advancement in the only approved drug for use in drugs are used pre-emptively, or field of CMV prevention in more CDI, prevention of recurrence of when CMV is shown to have emerged than a decade, and the opportunity disease remains a great unmet in the bloodstream. However, once for a shift in the treatment paradigm medical need. CMV emerges, the patient’s outcome for these very sick patients. is already at risk – thus the need According to published literature, for a well-tolerated prophylactic HCV-796 approximately 20 to 30 percent of alternative to prevent emergence According to the World Health patients suffering from CDI will have of the virus. Organization (WHO) and U.S. at least one episode of recurrence Centers for Disease Control and of disease; and of the patients who Our Phase 2 trial results with Prevention (CDC), approximately have one episode of recurrence, maribavir demonstrated that pro- 4.1 million Americans and 170 million more than half will have additional phylaxis with the drug dramatically people worldwide (3 percent of the episodes. The costs to the U.S. reduced the incidence of CMV world’s population) have been infected healthcare system alone of recur- infection in stem cell transplant with hepatitis C virus (HCV). Of the rent CDI are estimated to exceed patients compared to the current people infected today, fewer than 2 one billion dollars annually. The standard of care. We also saw no percent are receiving adequate goal of our novel preclinical NTCD CMV disease in patients receiving therapy for their disease. (non-toxigenic C. difficile) program maribavir. The tolerability of the drug is to prevent such recurrences. was also strong in that study, and we For ViroPharma’s Phase 2 drug saw none of the myelosuppression HCV-796, this has been a challeng- ViroPharma acquired NTCD in or renal toxicities that limit the use ing 12 months. In August 2007, February 2006 from one of the most of current anti-CMV agents. ViroPharma and Wyeth announced well-respected opinion leaders in the our decision to suspend dosing with CDI space, Dr. Dale Gerding of the Maribavir was granted orphan HCV-796 in our ongoing combination Hines VA. The goal of this novel drug designation in the U.S. in study with pegylated interferon and treatment approach is to prevent February 2007 for prevention ribavirin because, despite strong 12- disease recurrence through the oral of cytomegalovirus viremia and week data, we saw clinically significant administration of non-toxin producing

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