Cytel Corp. announced Friday that it has begun a Phase I trialof its hepatitis B immunotherapeutic, CY-1899 in 27 healthyvolunteers.
The placebo-controlled, dose-escalating study will evaluatesafety and tolerance, as well as the ability of the compound toinduce antigen-specific cytotoxic T cells (CTLs).
CY-1899 is a peptide-based immunotherapeutic comprised ofan antigenic peptide, a fragment of the organism causinghepatitis B, which is specifically recognized by CTLs and givesthe drug its disease specificity. A Cytel representativeexplained that the peptide, presented together with MHC(major histocompatibility complex), activates the T cells, whichthen proliferate and kill the hepatitis B infected cells.
The peptide is intended for treatment of people with chronichepatitis B and is therefore not a vaccine -- which typically isfor prophylactic use. The representative said that Cytel willprobably stop referring to CY-1899 as a vaccine. The companyplans to evaluate the drug in both a chronic active populationand in chronic carriers.
According to Cytel, about 1 million people in the U.S. andapproximately 300 million people worldwide are chronicallyinfected with the hepatitis B virus. Of these, approximately 10percent have chronic "active" hepatitis B infection; theremainder are chronic carriers.
Cytel (NASDAQ:CYTL) of San Diego noted that several othercompanies are also working on therapies that stimulate CTLs,but claimed that its approach is more specific.
Cytel uses a portion of the disease-causing antigen to create anantigenic peptide that induces an antigen-specific CTL responseto kill only hepatitis B infected cells. Other approaches attemptto induce an overall CTL response, the company said.
Other hepatitis B immunotherapeutics in development includeAlpha 1 Biomedicals Inc.'s alpha 1 thymosin, which is in PhaseIII testing, and Biogen Inc.'s beta interferon, in Phase II.
Alpha interferon (Schering-Plough's Intron A and Hoffmann-LaRoche's Roferon-A) is currently the only therapeutic on themarket for treatment of hepatitis B. Cytel said that "fewer than50 percent of those receiving alpha interferon see anyresponse, and a very large percentage of those receiving thedrug (20-45 percent) experience severe side effects."
In addition, the relapse rate following therapy is high, Cytelsaid. While alpha interferon activates the entire immunesystem, CY-1899 seeks to activate CTLs only against cellsinfected with hepatitis B and thus may result in increasedefficacy and less toxicity.
Cytel is developing several other peptide-basedimmunotherapeutics for various diseases, including hepatitis C,HIV, malignant melanoma and cervical cancer. Each of thesedrugs consists of a peptide that is present in all strains of thetargeted disease and thus makes the therapeutic antigenspecific. Cytel expects to begin clinical studies of peptides formalignant melanoma and cervical cancer next year.
Cytel's stock was up 63 cents a share on Friday, closing at$5.50.
-- Brenda Sandburg News Editor
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