TesofensineWeight Loss / GLP-1

Overview

Tesofensine (NS2330) is an orally active, centrally-acting small molecule (not a peptide) of the phenyltropane class that inhibits presynaptic reuptake of noradrenaline, dopamine and serotonin. It was originally developed by NeuroSearch for Alzheimer's and Parkinson's disease; both programs were discontinued for limited efficacy, but the weight loss seen in those trials redirected it toward obesity (later via Saniona/Medix, including the combination product Tesomet). Despite positive phase 2 data it is not approved by the FDA or EMA — it remains investigational and research-only.

Mechanism

Tesofensine is a triple monoamine reuptake inhibitor, blocking the NET, DAT and SERT transporters to raise synaptic noradrenaline, dopamine and serotonin. The anti-obesity effect is driven mainly by appetite suppression with some increase in energy expenditure. In diet-induced obese rats, the appetite effect was almost fully reversed by the alpha-1 antagonist prazosin and partly by the dopamine D1 antagonist SCH23390, implicating indirect alpha-1-adrenergic and D1 signaling. This stimulant-like pharmacology also underlies the observed increases in heart rate and blood pressure.

Clinical evidence

The pivotal human data come from the phase 2 TIPO-1 trial (Astrup et al., Lancet 2008), a 24-week randomized, double-blind, placebo-controlled study. Placebo-subtracted weight loss was dose-dependent — roughly 4.5%, 9.2% and 10.6% at 0.25, 0.5 and 1.0 mg versus ~2% on placebo — about double the efficacy of anti-obesity drugs marketed at the time, and predominantly fat mass. Later phase 3 work in Latin America reported significant weight loss, and combination (Tesomet) studies have been run in Prader-Willi syndrome. These findings are real but must be read alongside the safety concerns below, and tesofensine remains unapproved.

Safety profile

This is a YMYL-critical compound. Its stimulant-like action produces dose-dependent increases in heart rate and blood pressure and a psychiatric/CNS signal (agitation, mood changes, anxiety, insomnia), alongside dry mouth, nausea and constipation. Critically, a 2013 Lancet correspondence flagged under-reporting of adverse events in the pivotal TIPO-1 trial after a Danish regulatory audit found certain pre-randomization symptoms were not recorded as adverse events — a concern about under-stated psychiatric/cardiovascular risk. Tesofensine is not approved by any major regulator, is sold only as a research chemical, and is prohibited in sport (newly named on the 2025 WADA list as a stimulant). Research-use only; no dosing-as-treatment guidance.

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