From rxpgnews.com
Maribavir Shows Promising Activity Against Cytomegalovirus
By Akanksha, Pharmacology Correspondent
Mar 8, 2005, 14:26
ViroPharma Incorporated today announced the presentation of clinical data from the Phase 1 program for maribavir, the company's anti-cytomegalovirus (CMV) compound, currently in Phase 2 clinical testing. The data were presented at the 2005 American Society for Clinical Pharmacology and Therapeutics (ASCPT) Annual meeting in Orlando, Florida.
"We believe that all data to date strongly suggest that maribavir, our Phase 2 anti-CMV compound, is a safe and well tolerated compound, with promising antiviral activity against CMV," commented Colin Broom, ViroPharma's chief scientific officer.
"The antiviral activity of the compound on CMV was demonstrated in the original clinical studies performed by GlaxoSmithKline in HIV-positive patients. In addition, these Phase 1 data suggest that not only is maribavir well tolerated with a favorable pharmacokinetic profile, it also does not appear to induce CYP3A, an enzyme that metabolizes a large number of drugs used by transplant patients. These data are essential parts of the growing supportive body of clinical data for the compound. It is our hope that, if the data from the ongoing Phase 2 study in allogeneic stem cell transplant patients are supportive, we should be in pivotal Phase 3 studies with maribavir by this time next year - the first quarter of 2006."
Two abstracts described data from a double blind, placebo-controlled study in 20 nonsmoking, men and women between the ages of 18 and 55 years of age. The study was designed to evaluate the safety, tolerability, pharmacokinetics, and potential for drug interaction of single and multiple dose maribavir.
Healthy adult subjects were randomized 4:1 to receive a drug probe cocktail plus either 400 mg oral maribavir or placebo twice daily for 10 days.
In the first abstract, titled "Single and Multiple Dose Pharmacokinetics (PK) of Maribavir (MB) In Healthy Adults," by Joseph D. Ma, PharmD, et al., the safety, tolerability and pharmacokinetics of maribavir in the study were described. Pharmacokinetics were consistent with previously reported data with steady state plasma concentrations achieved after the first dose, consistent with a mean elimination half life of 3.7 hours.
Maribavir was also shown to be well tolerated, with taste disturbance reported as the most common adverse event. All subjects (16 maribavir, 4 placebo) completed the study.
The second abstract, entitled "Effect of the Anti-Cytomegalovirus Drug Maribavir on the Activities of Cytochrome P450 (CYP) 1A2, 2C9, 2C19, 2D6, 3A, N-Acetyltransferase-2, and Xanthine Oxidase as Assessed by the Modified Cooperstown 5+1 Drug Cocktail," by Joseph D. Ma, PharmD, et al., described the assessment of the drug interaction potential of maribavir in this study. Repeated dose maribavir did not affect CYP1A2, CYP2C9, or CYP3A activity.
Importantly, CYP3A, which was unaffected by repeated doses of maribavir, is an enzyme responsible for metabolizing a large number of drugs, including those used by transplant patients. Repeated dose maribavir may decrease CYP2C19 activity and had an equivocal effect on CYP2D6 activity. The clinical significance of these effects remains to be determined, but is unlikely to be of major clinical importance
Maribavir is a benzimidazole compound being studied for the prevention and treatment of cytomegalovirus (CMV) infections. The mechanism of action of maribavir is through the inhibition of UL97 kinase which impacts viral DNA synthesis and capsid maturation.
ViroPharma licensed maribavir from GlaxoSmithKline (GSK) in August 2003, conducted additional Phase 1 testing, and is now conducting Phase 2 clinical evaluation in allogeneic stem cell transplant patients. Prior to that date, maribavir had been administered orally to 100 human subjects in several GSK clinical studies.
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.
In most individuals with intact immune systems, CMV causes little to no apparent illness. However, in immunocompromised individuals, CMV can lead to serious disease or death. Before the availability of potent anti-HIV therapy, CMV associated retinitis was commonly seen in patients with HIV/AIDS.
Currently, patients who are immunosuppressed following hematopoietic stem cell (e.g., bone marrow) or solid organ transplantation remain 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.
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