© Oxford University Press 2006.
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Nicotine Vaccines Move Toward Pivotal Trials
Three candidate vaccines to help smokers quit reached development landmarks in 2005, and at least two of them are headed toward phase III trials, according to the three companies involved. In randomized trials, all three vaccines elicited antibodies to nicotine and increased quit rates compared with those of placebos.
The three vaccines work in similar ways, stimulating the production of antibodies that bind to nicotine molecules in the blood. The resulting complex is too large to pass through the blood–brain barrier, depriving nicotine receptors in the brain of the stimulus that leads to addiction.
The largest trial was carried out by CytosBiotechnology AG in Zurich, which announced 12-month results in October for its vaccine, CYT002-NicQb. In a phase II trial with 341 smokers, researchers saw no overall difference between the vaccine group and the placebo group. However, in a subgroup analysis, 42% of the participants who produced the highest antibody levels were able to quit smoking, compared with 21% of those who received a placebo.
The next step for Cytos is to optimize the dose, regimen, and formulation to produce high antibody concentrations in most vaccinated smokers, according to Claudine Blaser, Ph.D., director of corporate communications at Cytos. The results of a dose optimization study, which began in October, are expected in the second quarter of 2006. "Depending on regulatory approvals, phase III studies could get started in the course of 2007," Blaser said.
Also last fall, Nabi Biopharmaceuticals in Boca Raton, Fla., published the results of a phase II trial with 68 smokers comparing its vaccine, NicVAX, with a placebo. After 38 weeks' follow-up, antibody levels were highest in those receiving the highest doses of the vaccine and 30-day abstinence rates in that group were higher (33%) than those in the placebo group (9%), said principal investigator Dorothy Hatsukami, Ph.D., of the University of Minnesota, Minneapolis.
The challenge now is to obtain higher and more sustained antibody levels, she said. Nabi plans to launch a phase II/III trial in 2006, funded by the National Institute on Drug Abuse, to examine dosing and efficacy, according to Scott Winston, Ph.D., Nabi's vice president for project and technology management. The company also expects the results of its European phase II trial to be available in the first quarter of 2006, he said.
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The third candidate vaccine, TA-NIC, also looked promising in a phase I trial involving 60 smokers. The results at 12 months, announced in March 2005, showed a 38% quit rate with the vaccine compared with a placebo's 8%. A spokesperson for the vaccine's maker, Xenova in Slough, United Kingdom, reported by e-mail in January that "clinical development is moving forward and we expect to start a large phase II study soon."
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