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Pfizer's new anti-smoking drug shows promise

Published on 29/11/05 at 12:31pm

Smokers taking a new Pfizer treatment are more likely to kick the habit compared to those using GlaxoSmithKline's Zyban, according to new trial data.

Nicotine replacement therapy (NRT) products are the most popular form of smoking cessation drugs, but many pharmaceutical companies are looking to go one step further and market non-nicotine based products which make it easier to quit smoking.

In 2000, GSK's Zyban became the first such drug to hit global markets, but failed miserably, with concerns about serious side-effects its biggest handicap.

Zyban is now off-patent, but Pfizer needed to establish the superiority of its new drug in both safety and efficacy to establish its credibility.

Varenicline is a selective nicotinic acetylcholine receptor partial agonist, the first in a new class of smoking cessation drugs, and has already been filed with regulators in Europe and the US.

If approved, the drug will be marketed under the brand name of Champix, and analysts Deutsche Bank says it could reach annual peak sales of $500 million.

Varenicline works by partially stimulating and binding to the brain receptors that channel the habit-forming properties of nicotine.

"Varenicline was specifically designed to work at the same receptor site as nicotine to relieve craving and withdrawal symptoms while at the same time blocking the reinforcing effects of nicotine," said Dr Salomon Azoulay, varenicline development lead at Pfizer.

The two double-blind placebo-controlled trials, involving about 2,000 smokers, showed that patients taking varenicline were more likely to quit after 12 weeks than those patients receiving Zyban (bupropion) or placebo.

In both trials, the results showed that, at 12 weeks, 44% of smokers receiving varenicline had quit, compared with 30% of smokers receiving Zyban and 18% receiving placebo.

But the results showed that after one year only 20% of smokers receiving varenicline remained smoke-free, raising doubts that it may not offer significant longer-term advantages.

Pfizer said the drug was well tolerated in both trials but side-effects included nausea, headache, sleeping problems and abnormal dreams.

Pfizer's drug will have a number of potential competitors, including Sanofi-Aventis' Acomplia. The drug is expected to be approved for cardiovascular disease treatment early next year, but has also shown efficacy in smoking cessation, with a licence likely to follow.

Meanwhile, GSK has a new smoking cessation drug in phase II development while a number of companies, including biotechs Cytos and Xenova, are developing nicotine vaccines which could also challenge varenicline.

Smoking is the leading preventable cause of illness and premature death in the developed world and is responsible for 140,000 deaths from cardiovascular disease in the US by increasing the risk of heart attack, stroke and sudden death.

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