Safe and Sound?
All three of the human hemophilia trials under way-involving 21 patients as TR went to press-are primarily safety trials. But intense pressure to show that gene therapy is working has prompted the companies involved to spin the best possible story. Last June, Chiron allowed The Washington Post to interview a patient, who told the reporter that a nosebleed ended sooner than usual. The TKT trial’s principal investigator, Harvard hematologist David Roth, told TR that not only had none of his patients suffered significant side effects, but that “in at least one case, there appears to be a decrease in spontaneous bleeding.” Still, Roth stressed that it was too early to draw conclusions.
Avigen made the biggest splash. A December press release announced that the first three patients had “factor IX activity” and needed fewer injectable doses of factor than they had before the trial. Mt. Sinai Medical Center’s Aledort saw the data in early December. Though guardedly enthusiastic, he found the results to be far from conclusive. “I think it’s much too early to say this is the answer,” he says. One patient, for example, had indeed generated a “therapeutic” level of factor IX-but that level subsequently dropped. As for patients needing less factor after the treatment, “the question is, is this a placebo effect, or is it real?” says Aledort. “How the hell does anybody know that yet?” The jury will be out for a while. “If you really went a year, even six months, with consistent levels [of factor], I would say it’s working,” says Aledort.
And even though there weren’t obvious ill effects in the first six months of treatment, that doesn’t mean there won’t ever be any. One of the biggest dangers is that of inhibitory antibodies, or “inhibitors.” The very word fills hemophilia sufferers with dread. Overall, about 20 percent will, at some point, develop inhibitors that prevent factor from working. Massive doses of factor can often overcome these antibodies, but people with inhibitors tend to suffer more and die earlier than those without. Because of the hemorrhage risk, “surgery becomes impossible,” says Aledort, and “trauma leads to death not infrequently.”