Tesofensine

Tesofensine is defined as a combined norepinephrine-serotonin-dopamine reuptake inhibitor that is currently in Phase 3 trials, initially developed for Parkinson’s disease and Alzheimer’s dementia, but found to induce significant weight loss as a side effect.

Tesofensine is a pharmacological compound classified as a triple monoamine reuptake inhibitor, targeting the synaptic reuptake of three key neurotransmitters: dopamine, norepinephrine (also known as noradrenaline), and serotonin. 1 2 3 Initially developed for the treatment of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease, clinical trials revealed limited efficacy for these indications. Despite this, tesofensine has demonstrated significant effects on weight loss in clinical studies, which has shifted research interest towards its potential applications in obesity management. Additionally, tesofensine is reported to indirectly stimulate the cholinergic system, although the full details of its pharmacological profile remain incompletely characterized.

Tesofensine functions by inhibiting the reuptake of dopamine, norepinephrine, and serotonin at synaptic junctions, thereby increasing the extracellular concentrations of these neurotransmitters. 1 2 This mechanism is consistent with its classification as a triple monoamine reuptake inhibitor. While originally intended for neurodegenerative conditions, clinical trials revealed limited therapeutic benefit for these diseases; however, a notable side effect was persistent weight loss.

Preclinical studies in diet-induced obese rats demonstrated that tesofensine treatment led to reduced caloric intake and weight gain, accompanied by decreased dopamine D2/3 receptor availability in brain regions such as the nucleus accumbens and dorsal striatum, which are involved in reward and feeding behavior. 4 In human studies, a double-blind 14-day trial in obese subjects reported increased fat metabolism, elevated nighttime energy expenditure, and reduced appetite following tesofensine administration. 2 The weight loss observed in humans was primarily due to reductions in body fat and was associated with an increased metabolic rate. The drug’s modulation of monoamine neurotransmitters aligns with evidence that these systems regulate appetite suppression and metabolic rate enhancement, with norepinephrine particularly linked to increased energy expenditure. Common adverse effects reported include dry mouth, nausea, constipation, dizziness, and abdominal pain. Tesofensine has also been associated with dose-dependent increases in heart rate and blood pressure, and some patients experienced increased anxiety; however, it was found to lack abuse potential in studies involving recreational stimulant users. 1 5

Although tesofensine was initially developed for neurodegenerative diseases, its limited efficacy in these areas has redirected focus towards its potential as an anti-obesity agent. 2 1 Phase II clinical trials have demonstrated promising results in weight reduction among both non-obese and obese patients. In non-obese patients with body mass index (BMI) less than 30 kg/m², tesofensine produced placebo-adjusted weight losses of 1.8 kg and 2.5 kg at doses of 0.5 mg and 1 mg, respectively, over 14 weeks. In patients with BMI ≥ 30 kg/m², weight loss increased to 1.6 kg and 3.6 kg for the same doses.