GENENTECH CD4/IGG PHASE I CLINICALS WILL BE EXTENDED
GENENTECH CD4/IGG PHASE I CLINICALS WILL BE EXTENDED to examine safety and efficacy of higher doses of the compound. To date, Genentech's second generation CD4 product has been tested in approximately 70 patients at doses up to 1,000 mcg/kg; the firm plans to enroll approximately 50 new patients in studies that will evaluate doses in the 3,000-5,000 mcg/kg range. Patients currently in Phase I studies will probably be given the option of continuing CD4/IgG therapy at the higher dosage levels. The move to higher doses follows somewhat disappointing results from three Phase I studies, which looked at CD4/IgG doses between 100-1,000 mcg/kg in various dosage forms. Presenting the results of those studies at the Sixth International Conference on AIDS June 21, University of Washington/Seattle researcher Lawrence Corey reported that the product "was well tolerated [with] no significant side effects" but that no consistent improvements were seen in efficacy endpoints. "An occasional patient has had an apparent increase in CD4 cells from therapy, but this has not been consistent with dosage. Similarly, an occasional patient has exhibited [a] 50-70% decrease in p24 antigen," Corey told the conference. "However," he added, "these effects have not been consistent among groups over time." Based on the Phase I studies, the firm plans to pursue I.V. bolus and subcutaneous dosage forms of CD4/IgG. An intramuscular dosage form was also evaluated in one of the studies, but was found to have a "final bioavailability of only 35%," Corey said. Phase I studies with Genentech's CD4-IgG have shown the product to have a half life of approximately 10 hours, compared to roughly 45 minutes for the first generation product, soluble CD4. According to Genentech, the 10-hour half life should be sufficient if patients are given the product two-to-three times a week.
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