Pharmacologic Treatment Options for Obesity: Current and Potential Medications

Models and Strategies in the Development of Antiobesity Drugs

Obesity is a leading cause of morbidity and mortality worldwide. There is still a wide disparity between the necessity and availability of safe and effective antiobesity pharmacotherapies. Current drugs are associated with adverse effects and are limited in their efficacy. There is thus an urgent need for new antiobesity agents. Animal models are critical to the study of the biological mechanisms underpinning energy homeostasis and obesity and provide useful tools for the development of novel antiobesity agents. Our understanding of the complex neuronal and hormonal systems that regulate appetite and body weight has largely been based on studies in animals. This review describes the physiological basis of appetite, rodent models used in the development of antiobesity drugs, and potential future targets for novel antiobesity agents.

Gastric electrical stimulation for the treatment of obesity: from entrainment to bezoars-a functional review

GROWING WORLDWIDE OBESITY EPIDEMIC HAS PROMPTED THE DEVELOPMENT OF TWO MAIN TREATMENT STREAMS: (a) conservative approaches and (b) invasive techniques. However, only invasive surgical methods have delivered significant and sustainable benefits. Therefore, contemporary research exploration has focused on the development of minimally invasive gastric manipulation methods featuring a safe but reliable and long-term sustainable weight loss effect similar to the one delivered by bariatric surgeries. This antiobesity approach is based on placing external devices in the stomach ranging from electrodes for gastric electrical stimulation to temporary intraluminal bezoars for gastric volume displacement for a predetermined amount of time. The present paper examines the evolution of these techniques from invasively implantable units to completely noninvasive patient-controllable implements, from a functional, rather than from the traditional, parametric point of view. Comparative discussion over the available pilot and clinical studies related to gastric electrical stimulation outlines the promises and the fallacies of this concept as a reliable alternative anti-obesity strategy.

New drug targets for the treatment of obesity

There is a huge void in the current pharmacological treatment options for obesity. This gap is surprising given the high prevalence and associated costs of obesity. Many factors have prevented active drug development, including the poor safety and efficacy of earlier antiobesity drugs. However, there are now several compelling targets on the horizon. The new generation of antiobesity drugs offers hope for the management of obesity, but no single agent is likely to be a panacea. Rather, obesity will need to be managed like many other chronic diseases, with combination therapies and long-term treatment in order to achieve sustained success. New targets have arisen as more research has been performed to understand the complex circuitry that controls energy homeostasis. The goal of this review is to discuss the latest pharmacological agents and strategies that are under development and that may eventually be used for the treatment of obesity.

The new puzzle about the treatment of type 2 diabetes after the ACCORD and Da Qing studies

INTRODUCTION

There is a dramatic increase in the worldwide incidence of obesity, diabetes mellitus type 2, and other cardiovascular risk factors, summarized previously under the term "metabolic syndrome". Although preventive lifestyle modifications are effective, they are hard to implement and are therefore associated with a high number needed to treat. In most cases, intervention studies with hard endpoints such as myocardial infarction, stroke, or death are missing.

RESULTS

For example, the Da Qing study proved the efficacy of lifestyle modification with respect to manifestation of diabetes, but failed to show clear benefits regarding cardiovascular mortality. Several studies raised doubt, whether the concept of optimally reducing glucose is the optimal treatment for improving cardiovascular endpoints. Moreover other studies, such as Steno-2, showed an impressive effect of a multimodal therapy on hard endpoints.

CONCLUSIONS

In the future, the focus on new strategies for individualized therapies will increase. Additionally, approaches targeting novel molecular pathways are on the horizon, since plasma levels of posttranslationally modified proteins such as HbA1c are strong cardiovascular risk predictors despite normal glucose levels. For the clinician, it now becomes obvious that epidemiologically proven associations do not necessarily reflect causality. Studies addressing defined clinical endpoints, such as micro- and macrovascular morbidity and mortality are needed, as well as basic research, investigating other pathophysiological mechanisms, e.g., reactive metabolites and the digestive tract. The unexplained reduction in diabetes and its complications by bariatric surgery will give further insight not only into new therapeutic approaches, but also into mechanisms yet to be discovered.

Pharmacotherapies for obesity: past, current, and future therapies

Past therapies for the treatment of obesity have typically involved pharmacological agents usually in combination with a calorie-controlled diet. This paper reviews the efficacy and safety of pharmacotherapies for obesity focusing on drugs approved for long-term therapy (orlistat), drugs approved for short-term use (amfepramone [diethylpropion], phentermine), recently withdrawn therapies (rimonabant, sibutamine) and drugs evaluated in Phase III studies (taranabant, pramlintide, lorcaserin and tesofensine and combination therapies of topiramate plus phentermine, bupropion plus naltrexone, and bupropion plus zonisamide). No current pharmacotherapy possesses the efficacy needed to produce substantial weight loss in morbidly obese patients. Meta-analyses support a significant though modest loss in bodyweight with a mean weight difference of 4.7 kg (95% CI 4.1 to 5.3 kg) for rimonabant, 4.2 kg (95% CI 3.6 to 4.8 kg) for sibutramine and 2.9 kg (95% CI 2.5 to 3.2 kg) for orlistat compared to placebo at ≥12 months. Of the Phase III pharmacotherapies, lorcaserin, taranabant, topiramate and bupropion with naltrexone have demonstrated significant weight loss compared to placebo at ≥12 months. Some pharmacotherapies have also demonstrated clinical benefits. Further studies are required in some populations such as younger and older people whilst the long term safety continues to be a major consideration and has led to the withdrawal of several drugs.

Naltrexone for the treatment of obesity: review and update

Since their discovery in the brain and gastrointestinal tract nearly 40 years ago, endogenous opioid peptides have been progressively shown to play a role in the regulation of food intake. Animal and human studies regarding opioid peptides and ingestive behavior are reviewed. While the opioid receptor antagonist naltrexone is associated with minimal weight loss as monotherapy, it does have potential utility in the treatment of obesity when combined with the pro-opiomelanocortin activator bupropion.