UC Researchers Report New Drug Helps Smokers Quit, Limits Weight Gain
Researchers at the UC College of Medicine presented results of one of the largest smoking cessation trials ever conducted in the United States, STRATUS-US (STudies with Rimonabant And Tobacco USe). The findings show that a new drug, rimonabant, doubled the odds of quitting smoking compared with placebo, markedly reduced post-cessation weight gain at 10 weeks, and was well-tolerated.
"Smoking cessation is an enormous struggle for many people," said Robert Anthenelli, MD, one of the principal investigators in the STRATUS-US trial and an associate professor of psychiatry at the UC College of Medicine and Cincinnati VA Medical Center. "People who smoke are at high risk for cardiovascular disease. It is imperative to do anything and everything we can to treat tobacco dependence. Rimonabant represents a potentially promising new treatment option that can help people stop smoking while curbing post cessation weight gain. This may be a major step forward in smoking cessation."
Rimonabant is the first in a new class of drugs called Selective CB1 Blockers. The drug works by inhibiting the CB1 receptor, one of two receptors found in the EndoCannabinoid System (or EC System), that are located in the brain and in other parts of the body. Associated with systems regulating the body's intake of food, the EC system is also involved in tobacco dependency. Chronic tobacco use over-stimulates the EC system creating an imbalance. By blocking the CB1 receptor, rimonabant helps restore balance to the EC system resulting in reduced dependence on tobacco. In addition, in other clinical trials with rimonabant, researchers discovered that CB1 receptors are also found in adipose tissue (fat cells), which are associated with lipid and glucose metabolism. Blocking CB1 receptors in this part of the body has shown, in a recently completed obesity clinical trial called RIO-LIPIDS, results of which were also presented at the American College of Cardiology, that rimonabant not only significantly induces significant weight loss but reduces abdominal fat in overweight/obese people with untreated dyslipidemia, and also increases HDL-cholesterol (good cholesterol), lowers triglycerides, and significantly improves impaired glucose and insulin levels, all contributing risk factors for cardiovascular disease.
"It is widely known that smoking is linked to respiratory diseases and lung cancer, but smokers are also at 70 percent greater risk for cardiovascular disease than non smokers," said Dr. Anthenelli. "Since these two studies show that rimonabant treats obesity and related metabolic disorders in overweight/obese patients, and also helps people to quit smoking without significant post-cessation weight gain, we may have a very promising new approach for managing two major and preventable risk factors for cardiovascular disease with one and the same drug."
Summary of STRATUS US Findings STRATUS-US is a double-blind, placebo-controlled study, conducted in 11 clinical trial sites in the United States. The study enrolled 787 smokers who were motivated to quit, but had previously failed to do so. On average, patients enrolled in the trial were aged 42, smoked 23 cigarettes a day, had been smokers for 11-24 years and were classified as moderately to heavily nicotine-dependent based on the Fagerstrom Scale (measures nicotine dependence).
Patients received a daily fixed-dose of either 5mg or 20mg of rimonabant, or placebo. Patients were on treatment for 10 weeks. For an initial two-week period, they were allowed to smoke while initiating treatment but were given a target quit date at day 15. Abstinence was determined during the final four weeks of treatment and was measured by carbon monoxide concentrations in expired air (²10 ppm) and by plasma cotinine measurements (the principal nicotine metabolite).
Results indicate that rimonabant 20mg doubled the odds of quitting vs. placebo (p=0.002). Among patients completing the study, prolonged abstinence was significantly higher in the patients treated with 20mg of rimonabant (36.2 percent) when compared with patients treated placebo (20.6 percent). Prolonged abstinence was achieved in 20.2 percent of patients treated with rimonabant 5mg.
The trial also assessed weight changes in all randomized patients in the different groups and found that on average patients lost just over half a pound (0.3kg) on rimonabant 20 mg vs. a 2.5 lbs (1.1kg) weight gain for patients on placebo [p=0.001].
Further analysis of the impact of rimonabant 20mg on post-cessation weight gain shows that, overweight and obese patients lost weight during the 10-week treatment period, while normal weight smokers did not. There was no change in weight of normal weight smokers treated with rimonabant 20mg vs. a gain of 2 lbs (1kg) on placebo. Overweight smokers on rimonabant 20mg lost a pound (0.5kg) vs. a weight gain of 2lbs (0.9kg) on placebo. Obese smokers also lost just over a pound (0.6kg) vs. a weight gain of almost 3lbs (1.3kg) for those on placebo (p<0.001).
There was no difference in the overall drop out rate between patients on rimonabant or placebo. The number experiencing side effects in the rimonabant groups were slightly higher than those in the placebo group. Side effects were mostly mild and transient. The most common side effects where incidence was higher with rimonabant 20mg than placebo were nausea (15.7 percent vs. 9.2 percent) and upper respiratory tract infection (10 percent vs. 5.7 percent). The drop out rate due to side effects was 6.9 percent in the rimonabant 20mg group vs. 3.8 percent with placebo. Importantly, no cardiovascular safety concerns were identified with rimonabant.
About STRATUS The STRATUS program has enrolled over 6,500 patients in three worldwide Phase III trials. The studies are designed to provide evidence supporting indications for smoking cessation and long-term abstinence as well as reduction of post-cessation weight gain. STRATUS-US is the first of the three studies to be completed and the findings of this study were presented at the American College of Cardiology annual meeting. STRATUS-EU is being conducted in 32 sites throughout Europe and has an identical protocol to STRATUS-US. STRATUS-WW is a one-year maintenance study currently underway in 54 sites worldwide. Results for STRATUS-EU and STRATUS-WW are expected in the next 12 months.