ViroPharma Announces Initiation of Clinical Studies to Evaluate Maribavir for Treatment of Cytomegalovirus (CMV) Infection

EXTON, Pa., June 4, 2012 /PRNewswire/ -- ViroPharma Incorporated (NASDAQ: VPHM) today announced the initiation of a Phase 2 program to evaluate maribavir for the treatment of cytomegalovirus infections in transplant recipients.  The planned program will consist of two independent Phase 2 clinical studies that will include subjects at different ends of the spectrum of CMV infection or disease, namely those who have asymptomatic CMV, and those who have failed therapy with other anti-CMV agents.  Maribavir was granted U.S. Orphan Drug Designation in May of 2011 for treatment of clinically significant cytomegalovirus viremia and disease in at-risk patients. 

In addition, an abstract of data collected through the use of maribavir at six French transplant centers as part of a named patient program (NPP) has been accepted for the 24^th International Congress of the Transplantation Society to be held on July 15^th through 19^th in Berlin, Germany. 

"Physicians continue to see potential value in the novel mechanism of action of maribavir when used at higher doses in critically ill patients, particularly when other options have failed," stated Marc E. Uknis, MD, medical director, ViroPharma Incorporated.  "The outcomes seen in a small number of the NPP patients and the previously published experience in emergency-use IND patients suggests the possibility that maribavir may provide meaningful antiviral effects in treating active CMV infection and merits further careful evaluation because of the serious unmet need in immunocompromised transplant patients."

"Asymptomatic" CMV Study
ViroPharma has initiated a randomized, dose blinded multicenter Phase 2 study intended to enroll up to 160 subjects (recipients of either hematopoietic stem cell or solid organ transplant) who have demonstrated CMV viremia but do not have CMV organ disease.  Further, these subjects cannot have CMV infection that is resistant to other anti-CMV agents.  Subjects will be randomized to receive oral maribavir at one of three doses (400mg, 800mg or 1200mg BID) or valganciclovir for up to 12 weeks.  Blood levels of CMV DNA will be monitored throughout the study, and minimum virologic responses will be required after 3 and 6 weeks of treatment to continue study drug.  The study will be conducted at multiple transplant centers in 3-4 countries in Europe.

Resistant/Refractory CMV Study
ViroPharma is planning to initiate a second study, a randomized, dose blinded multicenter Phase 2 study intended to enroll up to 120 subjects (recipients of either hematopoietic stem cell or solid organ transplant) who have demonstrated CMV viremia with or without CMV organ disease.  All subjects will have failed to have an adequate virologic response to prior treatment with ganciclovir, valganciclovir, or foscarnet, and may have documented viral genetic resistance to any of these anti-CMV agents.  Subjects will be randomized to receive oral maribavir at one of three doses (400mg, 800mg or 1200mg BID) for up to 24 weeks.  Blood levels of CMV DNA will be monitored throughout the study, and minimum virologic responses will be required after 3 and 6 weeks of treatment to continue study drug.  The study is planned to be conducted at multiple transplant centers in the United States.

About Maribavir
Maribavir, a member of a new class of drugs called benzimidazole ribosides, is a potent and selective, orally bioavailable antiviral drug with a unique mechanism of action against cytomegalovirus and a favorable clinical safety profile.    Unlike currently available anti-CMV agents that inhibit CMV DNA polymerase, maribavir inhibits viral DNA assembly and inhibits egress of viral capsids from the nucleus of infected cells.  Maribavir is active in vitro against strains of CMV that are resistant to commonly used anti-CMV drugs.  The previous focus of clinical development of maribavir as an anti-CMV agent was on the prevention of CMV disease in transplant patients.  Results from Phase 3 studies indicated that maribavir at a dose of 100mg BID failed to meet its efficacy endpoints; however, maribavir has demonstrated a favorable safety and tolerability profile in all clinical studies to date.  While Phase 3 studies of CMV prophylaxis at the 100mg BID dose did not show sufficient activity to prevent CMV disease, the overall safety profile of maribavir and limited data from cases in which open-label maribavir was used as CMV treatment suggest that higher doses may provide clinical activity.  The U.S. Food and Drug Administration (FDA) granted Orphan Drug Designation to maribavir in May of 2011 for treatment of clinically significant cytomegalovirus viremia and disease in at-risk patients.

About Cytomegalovirus
CMV is a member of the herpes virus group, which includes the viruses that cause chicken pox, mononucleosis, herpes labialis (cold sores), and herpes genitalis (genital herpes).  Like other herpesviruses, CMV has the ability to remain dormant in the body for long periods of time.  Human CMV infection rates average between 50 percent and 85 percent of adults in the U.S. by 40 years of age, but in healthy adults causes little to no apparent illness.  However, in immunocompromised individuals including cancer patients, HIV patients, and transplant patients, and in children born with primary CMV infection, CMV can lead to serious disease or death.  Patients who are immunosuppressed following hematopoietic stem cell (bone marrow) or solid organ transplantation are at high risk of CMV infection.  In these patients, CMV can lead to severe conditions such as pneumonitis or hepatitis, or to complications such as acute or chronic rejection of a transplanted organ.  While currently available systemic anti-CMV agents are effective against the virus, their use is limited by toxicities, most notably bone marrow suppression and renal impairment. 

About ViroPharma Incorporated
ViroPharma Incorporated is an international biopharmaceutical company committed to developing and commercializing novel solutions for physician specialists to address unmet medical needs of patients living with diseases that have few if any clinical therapeutic options.  ViroPharma is developing a portfolio of therapeutics for rare and Orphan diseases including C1 esterase inhibitor deficiency, Friedreich's Ataxia, and adrenal insufficiency, cytomegalovirus (CMV); and recurrent C. difficile infection (CDI).  Our goal is to provide rewarding careers to employees, to create new standards of care in the way serious diseases are treated, and to build international partnerships with the patients, advocates, and health care professionals we serve.  ViroPharma's commercial products address diseases including hereditary angioedema (HAE), seizures, adrenal insufficiency and C. difficile-associated diarrhea (CDAD); for full U.S. prescribing information on our products, please download the package inserts at http://www.viropharma.com/Products.aspx; the prescribing information for other countries can be found at www.viropharma.com. 

ViroPharma routinely posts information, including press releases, which may be important to investors in the investor relations and media sections of our company's web site, www.viropharma.com. The company encourages investors to consult these sections for more information on ViroPharma and our business.

Forward Looking Statements
Certain statements in this press release contain forward-looking statements that involve a number of risks and uncertainties. Forward-looking statements provide our current expectations or forecasts of future events, including the therapeutic indication and use, safety, efficacy, tolerability and potential of maribavir and our focus, goals, strategy, research and development programs, and ability to develop pharmaceutical products, commercialize pharmaceutical products, and execute on our plans including clinical development activities with maribavir related to treatment of subjects with asymptomatic CMV as well as resistant / refractory CMV disease. In February 2009, based upon preliminary analysis of the data, we announced that our Phase 3 trial evaluating maribavir used as prophylaxis in allogeneic stem cell, or bone marrow, transplant patients did not achieve its primary endpoints. In addition, the study failed to meet its key secondary endpoints. Additionally, we announced that our Phase 3 trial evaluating maribavir in liver transplant patients was discontinued and that all patients on study drug were moved to current standard of care. While the current studies are in different patient populations and utilize different dosing levels, there can be no assurance that our clinical program with maribavir for the treatment of subjects with asymptomatic CMV as well as resistant / refractory CMV disease will yield positive results or support further development of maribavir for either indication.  The preliminary results from a small number of NPP and emergency-use IND patients may not be predictive of the results of the studies described in this press release. The FDA or EMA may view the data regarding maribavir for the treatment of subjects with asymptomatic CMV as well as resistant / refractory CMV disease as insufficient or inconclusive, request additional data, require additional clinical studies, delay any decision past the time frames anticipated by us, limit any approved indications, or deny the approval of maribavir for the treatment of subjects with asymptomatic CMV as well as resistant / refractory CMV disease.

These factors, and other factors, including, but not limited to those described in our annual report on Form 10-K for the year ended December 31, 2011 and quarterly reports on Form 10-Q filed with the Securities and Exchange Commission, could cause future results to differ materially from the expectations expressed in this press release. The forward-looking statements contained in this press release are made as of the date hereof and may become outdated over time. ViroPharma does not assume any responsibility for updating any forward-looking statements. These forward looking statements should not be relied upon as representing our assessments as of any date subsequent to the date of this press release.

SOURCE ViroPharma Incorporated