MON-095 Phentermine Induces Weight Loss in Prader-Willi Syndrome

Introduction: Prader-Willi syndrome (PWS) is a neurodevelopmental disorder caused by the absence of paternal genes on chromosome 15. It affects both sexes equally. It has an incidence of ~1 in 15,000 births and a worldwide prevalence of ~400,000. PWS is the most common obesity-linked syndrome. Hyperphagia, a defining characteristic of PWS, usually presents in childhood and leads to excessive weight gain. Hyperphagia and obesity related complications are among the leading causes of morbidity and mortality in PWS. Weight management in PWS is challenging which necessitates a multifaceted approach that includes pharmacological therapy. There are several FDA approved weight loss medications for adults with obesity; however, there is scant evidence to support their effectiveness in PWS. Clinical case: This is a 38 year old male diagnosed with PWS in late childhood. He weighed 34 kg at age 5 and continued to gain weight throughout his childhood, adolescence, and adulthood. He was diagnosed with type 2 diabetes (T2D) at age 17. The patient was initially managed with insulin but later switched to oral agents GLP-1 analogues. The latter were used for the last 10 years with no long-term effect on body weight. On the contrary, the patient continued to gain weight over the years and his glycemic control was fluctuating but overall remained poorly controlled.. In September of 2017, the patient was referred to an endocrinologist sub-specializing in bariatric medicine. At that point, he had a weight of 91 kg, BMI 38.9, HbA1c 8%, and was on metformin, glipizide, pioglitazone, and dulaglutide. He was started on phentermine in addition to switching his pioglitazone to empagliflozin. Upon starting phentermine, the patient and his caregivers reported a decrease in the patient’s food cravings. Over the following 12 months, he lost 19kg (21% of baseline body weight) with little to no adverse effects. Despite the significantly weight loss, there was no improvement in the patient’s glycemic control. Conclusion: This case illustrates the potential of using phentermine in weight management of patients with Prader-Willi syndrome. Further studies are needed to confirm the effectiveness of this therapy in PWS.