New Hope on the Horizon for Obesity
Two New Drugs, Qnexa and Contrave, Meet FDA Criteria for Weight Loss
Sep 27, 2009
The first step in tackling obesity is a change in diet and exercise; however, many obese people find it difficult to maintain short-term weight loss and the utilisation of pharmacological therapy may be employed, with surgery as a last resort. However, for those patients who require weight-loss drugs to help with weight management, their options are limited.
Obesity and Comorbid Conditions
Obesity is defined as having excess body fat and is often associated with comorbid conditions, such as diabetes, high blood pressure, stroke and high cholesterol. Research has shown that even a modest weight loss of 5-10% can help improve these conditions and also lower the risk for heart disease.
Current Treatment - OTC Diet Pills
There are a multitude of diet pills available over-the-counter (OTC), and while some may have been studied in clinical trials claiming they aid weight loss, they have not been officially approved as weight-loss drugs by the Food and Drug Administration (FDA). Therefore, the real clinical effectiveness of diet pills such as these is unknown.
Current Obesity Treatment - Prescription Weight-loss Drugs
Even the FDA approved weight-loss drugs have limited effectiveness, with a maximum weight loss of 10% of body weight achieved. These products are also not without unpleasant side effects.
Such therapies include sibutramine and phentermine, which act as appetite suppressants, but can also cause dry mouth, insomnia, high blood pressure and headache.
Orlistat is available in both prescription form as Xenical and OTC as Alli (the only FDA approved OTC weight-loss drug available). Orlistat is a lipase inhibitor, and acts in the gut to stop fat being absorbed. Therefore the side effects seen with appetite suppressants are not present, but other unwanted effects may occur, such as loose stools, flatulence and abdominal discomfort.
Weight-loss drugs other than these have failed to gain FDA approval or have previously been removed from the market due to risks associated with such products. One prominent case was that of rimonabant (Acomplia), which never gained access to the US market based on its association with a high number of psychiatric side effects. The drug was available in Europe for some time, but a re-evaluation of clinical safety data by authorities led to its removal in 2008.
As such, pharmaceutical companies are now embarking on developing drugs for stimulating weight loss that have fewer side effects.
What’s in the Pipeline for Obesity Treatment?
Two of the most promising weight-loss drugs in the pipeline are Qnexa and Contrave. These products are among the most advanced in clinical development, and positive results from late-stage trials have recently been reported that suggest each of the new drugs meets the FDA criteria to be considered an effective treatment for weight management.(The criteria include that twice the number of patients in the treatment group achieve more than 5% weight loss compared to the control group of patients, or that there be at least a 5% difference in weight loss between the treatment and control groups.)
Qnexa and Contrave each contain two active ingredients that are already available separately. Contrave consists of the antidepressants bupropion and naltrexone, while Qnexa contains the appetite suppressant phentermine in combination with the anticonvulsant topiramate.
Each of these new drugs has been studied for their effectiveness at inducing weight loss in large placebo-controlled trials, where obese patients were treated with the active drug or a placebo (control). All patients were asked to follow a reduced-calorie diet.
Qnexa and Contrave – Effectiveness for Weight Loss
In two separate studies, analysis of patients who completed one year of treatment with Contrave achieved an average weight loss of 8.1% (COR-I) and 8.2% (COR-II), compared with 1.8% and 1.5% for the control groups in each respective study. Trials for Qnexa showed more positive results, with average weight reductions of 14.7% (EQUIP) and 13.2% (CONQUER) for treated patients, compared with 2.5% and 2.4% for those on placebo, respectively. Furthermore, sub-analysis of the data showed that 43% and 39% of Qnexa treated patients achieved weight loss of at least 15% of their body weight in the EQUIP and CONQUER trials, respectively.
Both Qnexa and Contrave saw around three times the proportion of treated patients lose at least 5% of their body weight compared with the control group for trials with each drug.
Additional benefits to weight loss were also observed. Qnexa and Contrave both improved cardiovascular and metabolic risk factors, while Qnexa had the additional benefit of reducing inflammatory risk factors.
Qnexa and Contrave – Side Effects
Both Qnexa and Contrave were associated with side effects. Side effects for Qnexa were typical of appetite suppressants, including dry mouth, tingling, constipation and insomnia. Contrave was associated with nausea, headache and constipation. Importantly, however, there were no differences in the proportions of depressed episodes reported in the control and treatment groups for trials of either new product.
Which Weight-Loss Drug to Chose?
The perfect weight-loss drug would be one that works effectively with no side effects. Therefore physicians and patients will have to weigh up these new options in light of these factors. Nonetheless, with drug companies planning to market these products in the near future, physicians and patients will be presented with a lot more choices for obesity treatment than currently on offer, renewing the hope for those still struggling to combat their weight, having tried and failed on existing therapies.
Readers may also be interested in the following article: Will New Weight-Loss Drug Make it to Market?: Lorcaserin Reports Moderate Weight Loss in Late-Stage Studies
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