Role of Pharmacotherapy in Counteracting Weight Regain in Adolescents With Severe Obesity
Keywords
Abstract
Description
Severe obesity, afflicting ~8% of adolescents in the U.S., is a serious and challenging medical and public health problem. The number and levels of cardiovascular risk factors are considerably higher in the context of severe obesity compared to milder forms of obesity. Approximately 85% of youth with severe obesity have ≥1 cardiovascular risk factor. Non-alcoholic fatty liver disease is highly-prevalent among adolescents with severe obesity with estimates nearing 60%. Subclinical atherosclerosis and arterial stiffening is present in youth with severe obesity at levels similar to those with type 2 diabetes. Youth with severe obesity have high levels of inflammation and oxidative stress, adverse adipokine profiles, and arterial endothelial activation. Moreover, longitudinal data implicate obesity in childhood as a strong predictor of future risk factor clustering and sub-clinical atherosclerosis in adulthood. Risk of developing type 2 diabetes is high in youth with severe obesity. Severe obesity in adolescence is associated with chronic disability from a wide range of causes later in life. Perhaps most disturbing is the poor long-term prognosis for these youth. Approximately 90% will have a BMI ≥35 kg/m2 in adulthood. Disturbingly, severe obesity in adulthood reduces life expectancy by 7-14 years.
In the field of obesity management, weight loss maintenance has proven to be an arduous challenge. Indeed, long-term weight loss maintenance is seldom achieved owing to numerous biological adaptations occurring in the post-weight loss setting. These include, but are not limited to, neuroendocrine changes in the gut-brain axis influencing appetite and satiety and reduction of energy expenditure. Following weight loss, peripheral and central mechanisms respond in a way similar to starvation by conveying a sense that energy reserves have dwindled, activating a strong and persistent counter-response to increase caloric intake. Moreover, metabolic rate decreases, further compounding the propensity for weight rebound. These counter-regulatory adaptations persist for many years following initial weight loss, and in fact might be permanent.
Adolescents with severe obesity (BMI ≥120% above the 95th percentile or BMI ≥35 kg/m2) are not immune to the vexing issue of weight regain as evidenced by the poor outcomes of interventions using lifestyle modification alone.22-25 Indeed, large clinic-based studies from Europe and the U.S. reported that only a small fraction of patients were able to achieve and maintain clinically-meaningful weight loss with lifestyle modification therapy. Metabolic/bariatric surgery is an effective treatment but uptake is very low and many pediatricians and parents are concerned about the irreversible nature of this treatment and worry about the possibility of long-term (decades) risks, which are currently unknown. Therefore, a large treatment gap exists between lifestyle modification therapy and metabolic/bariatric surgery that remains unfilled.
Pharmacotherapy has the potential to prevent weight regain by targeting counter-regulatory mechanisms in the post-weight loss setting, with various agents demonstrating improved long-term weight loss durability in adults. Unfortunately, pediatric options are limited as only one obesity medication is approved for use among adolescents for long-term use (orlistat), and is rarely prescribed because of modest efficacy and notable side effects. Among the most promising candidates in the pediatric pipeline, owing to its relatively high degree of efficacy compared to other medications, is the combination of phentermine and topiramate, which is the most effective FDA-approved adult obesity medication currently available. Placebo-subtracted weight loss at one and two years with phentermine/topiramate is 9% at the top dose in adult trials. The mechanisms of action of phentermine/topiramate, which together are thought to reduce appetite, enhance satiety, and potentially increase energy expenditure, are well-suited for the purpose of weight loss maintenance since they target many of the biological adaptations known to induce relapse and subsequent regain.
The rationale for specifically focusing on phentermine/topiramate (vs. other medications) to prevent weight regain is supported by its multiple mechanisms of action, which are thought to target many of the post-weight loss counter-regulatory biological adaptations known to induce relapse. These mechanisms include: 1) reducing appetite through inhibition of norepinephrine reuptake (phentermine) and reduction of hypothalamic glutamate neurotransmission (topiramate) and lowering the levels of neuropeptide Y (topiramate); 2) enhancing satiety by slowing gastric emptying (combination of phentermine/topiramate); and 3) increasing energy expenditure (both phentermine and topiramate independently). Through these mechanisms of action, sustained weight loss has been demonstrated with phentermine/topiramate treatment in adults. While other obesity medications target some of these pathways, their respective mechanisms of action are generally less comprehensive, and accordingly have lower efficacy, ranging from 3-5% placebo-subtracted weight reduction at 1 year.
In terms of safety, topiramate is FDA-approved in children and adolescents for the treatment of seizures and migraine headaches with a reasonable safety track-record. Importantly, the investigators observed no signal of cognitive problems in a pilot clinical trial of topiramate for the treatment of obesity. Phentermine is FDA-approved for short-term use in ages >16 years old for treatment of obesity and is the most widely-prescribed adult obesity medication in the U.S. Although in a distinct medication class, phentermine is not dissimilar in mechanism of action and side effects to many of the stimulant medications widely-prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) in youth. Adult data suggest no adverse cardiovascular effects or increased risk of addiction potential or withdrawal symptoms associated with phentermine use and the investigator's clinical experience with phentermine in adolescents with obesity demonstrated an acceptable safety profile.
Dates
Last Verified: | 04/30/2020 |
First Submitted: | 02/20/2020 |
Estimated Enrollment Submitted: | 03/03/2020 |
First Posted: | 03/05/2020 |
Last Update Submitted: | 05/10/2020 |
Last Update Posted: | 05/11/2020 |
Actual Study Start Date: | 07/31/2020 |
Estimated Primary Completion Date: | 03/30/2025 |
Estimated Study Completion Date: | 03/30/2027 |
Condition or disease
Intervention/treatment
Drug: Phentermine-Topiramate
Dietary Supplement: Meal Replacement Therapy
Other: Placebo
Phase
Arm Groups
Arm | Intervention/treatment |
---|---|
Experimental: Meal Replacement Therapy Participants who are enrolled in the study will be administered a short-term (six weeks) meal replacement induction period. Because the trial is deigned to evaluate weight loss maintenance, participants must achieve at least 5% BMI reduction at week six of the meal replacement period in order to be randomized. Subjects will be asked to strictly follow the eating regimen, which will include a total of approximately 1,000 kcals per day of commercially-available liquid shakes (breakfast and lunch), pre-packaged frozen entrée meals for dinner, two servings of fruit, and three servings of vegetables. Shakes/meals will be provided free of charge - fruits/vegetables will be purchased by the participants. Guidance will be provided regarding the use of the meal replacement shakes at school, and participants will be encouraged to engage in family meal sessions despite eating different foods. | Dietary Supplement: Meal Replacement Therapy The first six weeks of the study, subjects will receive meal replacement therapy in an effort to reduce their BMI by at least 5%. |
Active Comparator: Phentermine/Topiramate Participants who achieve at least 5% BMI reduction at week six of the meal replacement period will be randomized (1:1) to receive either phentermine/topiramate or placebo. Participants randomized to phentermine/topiramate will start treatment at 3.75 mg/23 mg orally once daily in the morning for 14 days, then increased to 7.5 mg/46 mg orally once daily in the morning for 14 days, then be increased to 11.25 mg/69 mg orally once daily in the morning for 14 days, then increased to 15 mg/92 mg orally once daily in the morning for the remainder of the trial. Following the final study visit, participants will be down-titrated gradually by taking medication every other day for seven days before stopping treatment altogether. | |
Placebo Comparator: Placebo Participants who achieve at least 5% BMI reduction at week six of the meal replacement period will be randomized (1:1) to receive either phentermine/topiramate or placebo. Participants randomized to the placebo will receive inert tablets that look like the active comparator. In order to mimic the active comparator arm, subjects randomized to the placebo arm will up titrate their placebo at the beginning of the study treatment and will down titrate as in the active comparator arm. Participants will be instructed to take the medication under the supervision of a parent/guardian and pill counts of returned product will serve as a proxy of treatment compliance. |
Eligibility Criteria
Ages Eligible for Study | 12 Years To 12 Years |
Sexes Eligible for Study | All |
Accepts Healthy Volunteers | Yes |
Criteria | Inclusion Criteria: - Severe obesity (BMI >/= 120% of the 95th percentile or BMI >/= 35 kg/m2) - Age 12 to < 18 years of age at enrollment (screening) and Tanner stage >/= 2 Exclusion Criteria: - Diabetes (type 1 or 2) - Current or recent (< six months prior to enrollment) use of anti-obesity medication(s) defined as orlistat, phentermine, topiramate, combination phentermine/topiramate, liraglutide, lorcaserin, and/or combination naltrexone/bupropion |
Outcome
Primary Outcome Measures
1. To measure changes in BMI. [58 weeks.]
2. To measure changes in total body fat [iDXA will be conducted at four timepoints (Baseline, 1 day of Randomization, Week 26 and Week 52).]
3. To measure changes in visceral fat. [iDXA will be conducted at four timepoints (Baseline, 1 day of Randomization, Week 26 and Week 52).]
4. To measure changes in arterial stiffness. [SphygmoCor testing will be conducted at four timepoints (Baseline, 1 day of Randomization, Week 26 and Week 52).]
5. To measure changes in lipids. [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]
6. To measure changes in glucose. [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]
7. To measure changes in insulin. [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]
8. To measure changes in hemoglobin A1c. [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]
9. To measure changes in C-reactive protein (CRP). [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]
10. To measure changes in oxidized LDL. [Baseline, 1 day of Randomization, Week 26 and Week 52 visits.]