Nabi Biopharmaceuticals announced positive phase II clinical results for NicVAXT (Nicotine Conjugate Vaccine), a vaccine that is being developed to prevent and treat nicotine addiction by acting as an aid to smoking cessation.

The results indicated a 33 per cent quit rate in smokers who received NicVAX at the highest dose level versus 9 per cent in the placebo group. The results represented a vaccine-only effect, as patients were only given NicVAX without any supplemental treatments, behavioural support or counselling. The objectives of the study were to show that NicVAX was able to safely generate nicotine- specific antibodies in smokers, and to assess its potential use as an aid in smoking cessation among smokers who wanted to quit.

NicVAX is designed to cause the immune system to produce antibodies that bind to nicotine and prevent it from entering the brain, thereby preventing the 'rush' that occurs when nicotine binds to receptors in the brain. This 'rush' is believed to be the main physical reason that most people cannot stop smoking, the release says.

The phase II trial was a double-blinded, placebo-controlled, randomized study in smokers designed to assess safety and antibody response. In addition, standard measures of anti-smoking efficacy, such as percentage of patients who quit smoking, was included. Conducted at three clinical trial sites across the United States, a total of 68 smokers were randomized to receive a series of up to 4 injections containing either NicVAX or a placebo.

Three doses (50, 100 or 200 micrograms) of NicVAX or a placebo were administered on days 0, 28, 56 and 182. The results showed that, at the 200- microgram dose, 33 per cent of smokers in the treated group quit smoking (defined as no smoking for at least 30 consecutive days) versus 9 per cent in the placebo group. In addition, results showed a substantial reduction in average cigarette consumption in smokers who received the highest dose of NicVAX versus lower doses or placebo. Smoking cessation was confirmed by cotinine and carbon monoxide levels, which are biochemical markers of smoking. Nicotine dependency was measured by a questionnaire and also showed a substantial reduction at the top dose of NicVAX as compared to placebo or the lower dose levels. NicVAX was very well tolerated and side effects were similar between the active dose levels and the placebo group. The outside clinical costs for the trial were funded by a grant from the National Institute on Drug Abuse, under the US National Institutes of Health.

"The vaccine-only effect that we saw in this trial is truly impressive," said Henrik S Rasmussen, senior vice president clinical, medical and regulatory affairs, Nabi Biopharmaceuticals. Dr. Rasmussen continued, "If these results could be repeated in a larger study, it would make NicVAX potentially one of the most efficacious approaches to smoking cessation available. The 33 per cent efficacy rate that we saw at the high dose level is particularly remarkable when one takes into consideration that this was a vaccine-effect only and that psychological counselling or other behavioural interventions were not provided."

Dr. Rasmussen concluded, "We will continue to analyze the data from this study, as well as start discussions with regulatory authorities about the future development path for this compound. These additional analyses, combined with inputs from regulatory authorities and key opinion leaders in the field will help us devise the optimal development path NicVAX. However, these data clearly support the continued development of NicVAX on an aggressive time scale."

Thomas H McLain, chairman, CEO and president, Nabi Biopharmaceuticals stated, "These results are very encouraging and we believe indicate that NicVAX may represent a new paradigm in treating nicotine addiction, recognized as one of the most difficult addictions to break. In addition, since NicVAX uses the same carrier protein as StaphVAX, these results provide further proof for our conjugate vaccine technology. Using this technology we are able to help the body's immune system recognize and deal with problems it otherwise would ignore."