Healthcare Industry News:  antiviral 

Biopharmaceuticals

 News Release - September 28, 2006

ViroPharma Initiates First of Two Phase 3 Studies of Maribavir in Transplant Patients

First International Study Will Evaluate Efficacy of Maribavir in Stem Cell Transplant

EXTON, Pa., Sept. 28 (HSMN NewsFeed) -- ViroPharma Incorporated (Nasdaq: VPHM ) today announced that it had initiated the first of two Phase 3 clinical studies of maribavir in transplant patients. The current study will evaluate the prophylactic use of maribavir in stem cell transplant (SCT) patients, and will be conducted in approximately 80 transplant centers in the U.S., Canada, and several European countries.

ViroPharma's international Phase 3 stem cell transplant study will evaluate the efficacy, safety and tolerability of prophylactic use of maribavir administered orally for up to 12 weeks for the prevention of cytomegalovirus (CMV) disease in recipients of allogeneic stem cell transplants. The study also will evaluate the pharmacokinetics of maribavir in this subject population.

"This marks the first pivotal study in over a decade of an anti-CMV agent that represents an entirely new class of compound with a unique mechanism of action," commented Colin Broom, M.D., ViroPharma's chief scientific officer. "Our goal is for maribavir to offer transplant patients an efficacious and specific antiviral therapy with a more favorable side effect profile than the currently available therapies. In Phase 2, maribavir was well-tolerated and showed robust antiviral activity in preventing CMV infections post-transplant. We were encouraged that no maribavir treated patients developed CMV disease, compared to an incidence of 11 percent in patients treated on the placebo arm of the study. The current Phase 3 study will further evaluate the efficacy and safety of maribavir in this very sick patient population. We also have the ambitious goal of initiating a Phase 3 trial in solid organ transplant patients late this year."

Continued Broom, "I was pleased to see the enthusiasm and interest shown at our investigators' meeting held earlier this month. Maribavir could be an important drug for transplant physicians, and for the 46,000 patients undergoing stem cell or solid organ transplants in the U.S. each year. Its profile to date suggests that it could be an important therapeutic option and could change the therapeutic paradigm to more widespread adoption of prophylaxis against this potentially lethal disease."

SCT Phase 3 Study Design

ViroPharma has initiated a randomized, double-blind, placebo-controlled, multicenter pivotal Phase 3 study intended to enroll approximately 500 patients who have undergone allogeneic stem cell transplantation. Per the final protocol, following transplantation and transplant engraftment, eligible patients will be randomized to receive maribavir or matching placebo in a 2:1 randomization ratio. Patients will receive maribavir 100 mg BID or placebo for a maximum duration of 12 weeks. The target for completion of enrollment is 18 months.

Enrolled subjects will undergo testing for CMV infection at least weekly. CMV surveillance will include weekly testing at a central laboratory for the presence of CMV pp65 antigenemia and for the presence of CMV DNA in plasma using a polymerase chain reaction (PCR). If CMV infection is detected during the study drug administration period (or if CMV organ disease is diagnosed), study drug will be discontinued and the subject will be managed according to standard CMV treatment practices at the transplant center.

The primary efficacy endpoint will be the incidence of CMV disease within 180 days post-transplant, which is predicted to be approximately 10 percent in the placebo (current standard of care) arm based on data from the Phase 2 study, data from published literature, and information from transplant center databases. Following extensive dialogue with FDA, a number of key secondary endpoints associated with CMV reactivation have been identified and assessment of these endpoints will play an important part in assessing the clinical benefit of maribavir. These key secondary endpoints include incidence of initiation of preemptive anti-CMV therapy, incidence of graft-versus-host disease, mortality and CMV disease-free survival.

Maribavir Phase 2 Data

In March of 2006, ViroPharma announced positive preliminary results from a Phase 2 study with maribavir. The study enrolled 111 patients from 13 US transplant centers and demonstrated that prophylaxis with maribavir displayed strong antiviral activity, as measured by significant reduction in the rate of reactivation of CMV in recipients of allogeneic stem cell transplants, and that administration of maribavir for up to 12 weeks had a favorable tolerability profile. Maximum duration of follow-up in this study was five months post-transplant. Data from the Phase 2 study included:

-- In an intent-to-treat analysis of the first 100 days post-transplant, the number of subjects who required pre-emptive anti-CMV therapy was statistically significantly reduced in each of the maribavir groups compared to the placebo group.

-- Including the follow-up period, cases of CMV disease in the study occurred only in the placebo group (11 percent); no cases of CMV disease occurred in patients receiving maribavir.

-- For each of the CMV assays used there was consistency in showing fewer CMV infections in the maribavir groups compared to placebo. In most cases, the reduction in rates of infection between patients in the maribavir groups and placebo were statistically significant, irrespective of the assay used.

-- Maribavir administered for up to 12 weeks had a favorable tolerability profile. The incidence of most adverse events occurred at similar rates in maribavir and placebo groups.

-- Consistent with prior clinical studies, the most notable adverse events were taste disturbance and nausea.

-- Analyses of laboratory data did not identify any notable differences between maribavir groups and placebo; there was no adverse impact on neutrophil count or other hematologic parameters.

The company expects the full Phase 2 data set to be presented at the 48th Annual Meeting of the American Society of Hematology (ASH) to be held in Orlando, Florida on December 9 through 12, 2006.

About Maribavir

Maribavir is a potent and selective, orally bioavailable antiviral drug with a unique mechanism of action against cytomegalovirus and a favorable early clinical safety profile. It is a potent member of a new class of drugs called benzimidazole ribosides. 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.

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% and 85% 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 a biopharmaceutical company dedicated to the development and commercialization of products that address serious diseases treated by physician specialists and in hospital settings. ViroPharma commercializes Vancocin®, approved for oral administration for treatment of antibiotic-associated pseudomembranous colitis caused by Clostridium difficile and enterocolitis caused by Staphylococcus aureus, including methicillin- resistant strains (for prescribing information, please download the package insert at http://www.viropharma.com/docs/pulvules_pi.pdf). ViroPharma currently focuses its drug development activities in viral diseases including cytomegalovirus (CMV) and hepatitis C (HCV). For more information on ViroPharma, visit the company's website at http://www.viropharma.com.

Certain statements in this press release may contain forward-looking statements that involve a number of risks and uncertainties, including those relating to our expected timeframe to complete enrollment of the first Phase 3 study and for the initiation of additional pivotal studies; our expected incidence of CMV disease within 180 days post-transplant; and our hope that maribavir could be an important drug for transplant physicians and that maribavir could change the current treatment paradigm for transplant patients. Our actual results could differ materially from those results expressed in, or implied by, these forward-looking statements. The development and commercialization of pharmaceutical products is subject to risks and uncertainties. Further testing such as the planned Phase 3 clinical trials, may not support any or all of the statements in this press release. There can be no assurance that that we will initiate dosing or complete enrollment of the Phase 3 study, or that the second Phase 3 study will be initiated within the timelines described in this press release or at all, that our Phase 3 program will yield positive results or that maribavir will ever be approved by the FDA. These factors, and other factors, including, but not limited to those described in ViroPharma's quarterly report on Form 10-Q for the quarters ended March 31, 2006 and June 30, 2006 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 may become outdated over time. ViroPharma does not assume any responsibility for updating any forward-looking statements.


Source: ViroPharma

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