Tesofensine

This 24-week phase 2 RCT (TIPO-1) randomized 203 obese patients (BMI 30-40) to tesofensine 0.25, 0.5, or 1.0 mg or placebo, all with an energy-restricted diet. Mean placebo-subtracted weight loss was 4.5%, 9.2%, and 10.6% for the ascending doses versus 2.0% for diet plus placebo, roughly double the efficacy of anti-obesity agents marketed at the time. Dose-dependent increases in heart rate, and at 1.0 mg blood pressure and mood/psychiatric-related events, were observed; the 0.5 mg dose was proposed as the optimal efficacy/tolerability balance. (A later audit prompted a Lancet expression of concern regarding under-reporting of some adverse events.)

In this mid-stage trial, obese adults on a reduced-calorie diet who took tesofensine lost far more weight than those on diet alone, with the middle dose producing about four times as much loss over six months. The results suggested tesofensine could produce roughly twice the weight loss of the diet drugs available then. However, higher doses raised heart rate and blood pressure and affected mood, so the drug's safety needed careful monitoring.

This report pooled four randomized, double-blind, placebo-controlled 14-week trials (two in Alzheimer's disease, two in Parkinson's disease; tesofensine n=740, placebo n=228) originally designed to assess neurologic endpoints, with no weight-loss intervention. Tesofensine produced statistically significant, dose-dependent weight loss; at the highest dose tested (1.0 mg) patients lost a mean of roughly 3.7% of body weight, with the effect most pronounced in heavier individuals. This unexpected metabolic signal from the neurodegenerative-disease development program provided the rationale for repurposing tesofensine as an anti-obesity agent.

Tesofensine was first tested as a treatment for Alzheimer's and Parkinson's disease. When researchers pooled those trials, they noticed patients were steadily losing weight even though the studies were not about weight loss, and heavier patients lost the most. This surprise finding is what led scientists to redirect the drug toward treating obesity.

This randomized, double-blind, placebo-controlled phase 2 trial evaluated tesofensine (0.125, 0.25, 0.5, or 1.0 mg once daily over 14 weeks) as adjunct therapy in 261 levodopa-treated patients with advanced Parkinson disease and motor fluctuations. Tesofensine failed to produce a consistent dose-dependent reduction in daily OFF time or meaningful improvement in UPDRS motor scores relative to placebo, and higher doses were associated with increased gastrointestinal and psychiatric/neuropsychiatric adverse events. The lack of clear efficacy on Parkinsonian endpoints contributed to discontinuation of tesofensine's neurologic development program.

This trial tested tesofensine as an add-on treatment in people with advanced Parkinson's disease whose symptoms fluctuated during the day. The drug did not reliably reduce their symptom-heavy periods or improve movement compared with a placebo, and higher doses caused more stomach and mood-related side effects. Because it did not work well enough for Parkinson's, development for that condition was stopped.