What it is
Tesofensine (NS2330) is a small-molecule phenyltropane derivative (molecular formula C₁₇H₂₃Cl₂NO, MW 328.28 g/mol, CAS 195875-84-4) originally synthesized at NeuroSearch in Denmark in the late 1990s for Parkinson's and Alzheimer's disease. Structurally it is a bicyclic tropane — 8-azabicyclo[3.2.1]octane core with a bis(4-chlorophenyl)methoxy substituent — and pharmacologically it is a triple monoamine reuptake inhibitor: NET IC₅₀ ~1.7–3.2 nM, SERT IC₅₀ ~11 nM, DAT IC₅₀ ~8–65 nM. It is orally bioavailable with an unusually long plasma half-life (~9 days / 220 hours), metabolized primarily by CYP3A4 to an active metabolite M1 (NS2360). The long half-life supports once-daily dosing and means steady state is not reached for weeks, which has implications for both dose titration and any adverse-event attribution. Saniona (Denmark/US) holds worldwide rights since 2014. The compound is NOT a peptide — Peptigrade covers it because it sits in the obesity therapeutic space alongside the GLP-1 and GLP-1/GIP class and is approved in at least one jurisdiction for BMI ≥30.
In plain English
Tesofensine (also called NS2330) is a small synthetic molecule — NOT a peptide. It is included on this site because it competes in the obesity treatment space alongside GLP-1 drugs. Pharmacologically it is a triple monoamine reuptake inhibitor, meaning it blocks the brain's recycling pumps for three chemicals: norepinephrine, dopamine, and serotonin. Blocking those pumps raises the active levels of all three. It was originally made in Denmark in the 1990s for Parkinson's and Alzheimer's disease — researchers noticed patients were losing weight as a side effect and shifted focus to obesity. It comes in pill form, taken once daily. It has an unusually long half-life of about 9 days, so it builds up in the body slowly and takes 3–5 weeks to reach a steady level in the blood. Saniona, a Denmark/U.S. biotech, has owned the rights since 2014.
How it works
- 01
Triple monoamine reuptake inhibition (NE/DA/5-HT)
Tesofensine binds and inhibits all three monoamine transporters — NET, DAT, and SERT — in the low-nanomolar range (Lehr 2008, J Pharmacol Exp Ther; Astrup 2008 Lancet supplement pharmacology summary). This simultaneous blockade raises synaptic concentrations of norepinephrine, dopamine, and serotonin, with the norepinephrine effect predominating in hypothalamic feeding circuits and the serotonin effect contributing to satiety signaling. The dopamine component adds reward-pathway modulation relevant to hedonic eating. This is the same receptor-class rationale as sibutramine (SNRI, withdrawn 2010 for CV events) and bupropion-naltrexone (NE/DA-focused), but with dopamine-transporter affinity closer to a phenyltropane — which is the structural basis for the ongoing scrutiny of abuse potential.
In plain English
It blocks the recycling of three brain chemicals at once
Tesofensine blocks the transporters that normally vacuum up norepinephrine, dopamine, and serotonin after they fire in the brain. Blocking those recycling pumps raises the active levels of all three. Norepinephrine effects dominate in the hunger-control areas of the brain. Serotonin adds to the feeling of fullness. Dopamine affects food reward — how pleasurable eating feels. This approach is similar to sibutramine (a drug pulled from the U.S. market in 2010 for heart risks) and bupropion-naltrexone (Contrave), but tesofensine also blocks the dopamine pump at a level closer to stimulant-class drugs — which is why abuse potential remains a live question.
- 02
Lateral hypothalamic GABAergic silencing
Perez 2018 (Nature Neuropsychopharmacology; PMID 30385867 and related electrophysiology work) showed tesofensine silences GABAergic neurons in the lateral hypothalamus in diet-induced obese rats, which disinhibits downstream satiety circuitry. The appetite-suppressant effect in rodents is reproduced by local LH microinfusion, arguing for a central — not peripheral — site of action. The appetite effect is also mediated through indirect α1 adrenergic and dopamine D1 pathway activation, consistent with the NE/DA bias of the transporter affinities.
In plain English
It quiets hunger-promoting brain cells
A 2018 rat study showed tesofensine directly silences specific nerve cells in the lateral hypothalamus — the brain region that drives hunger. Quieting those cells releases the brake on downstream circuits that signal fullness. Injecting tesofensine directly into that brain region reproduced the appetite-suppression effect in rats, confirming the main action is in the brain, not in the gut or body.
- 03
Striatal D2/D3 receptor availability and food reward
Axel 2010 (Neuropsychopharmacology) and related imaging work in obese rats showed tesofensine decreases striatal D2/D3 receptor availability, which is the imaging correlate of reduced food reward drive. In humans this has not been directly measured, but the clinical pattern — early appetite suppression, reduced snacking, preserved meal satisfaction — is consistent with reward-pathway modulation rather than pure gastric or peripheral satiety.
In plain English
It may reduce how rewarding food feels
Brain imaging studies in obese rats showed tesofensine reduces the number of available dopamine D2/D3 receptors in the brain's reward center. Fewer available receptors means the reward signal from eating is weaker. In people, this has not been directly measured with brain imaging. But the clinical pattern — early appetite loss, fewer snacks, normal meal satisfaction — fits with a dampened reward system rather than just gut-level fullness.
- 04
Thermogenesis and energy expenditure
Sjödin 2010 (Int J Obes) quantified 24-hour energy expenditure in a metabolic-chamber substudy of the Phase 2 program and found tesofensine 1.0 mg modestly increased resting energy expenditure beyond what the weight loss alone would predict — consistent with sympathetic / noradrenergic thermogenic activity. The effect is smaller than the appetite-suppression contribution to total weight loss but is mechanistically coherent with the observed BP/HR rise.
In plain English
It slightly raises the amount of energy your body burns
A metabolic-chamber substudy within the Phase 2 trial found tesofensine 1.0 mg modestly increased resting energy burn — more than the weight loss alone would explain. This is consistent with the norepinephrine (fight-or-flight) effect increasing calorie burn. It is also likely the same mechanism behind the heart rate and blood pressure increases.
- 05
Pharmacokinetics — the long half-life
Tesofensine has an elimination half-life of roughly 9 days (220 hours) in humans (Appel 2014, Clin Pharmacokinet; NeuroSearch Phase 1 data). CYP3A4 hydroxylation produces the active metabolite M1 (NS2360), which contributes to sustained effect. Steady state is not reached for 3–5 weeks, which is why the Phase 2b trials titrated over weeks and why BP/HR monitoring is front-loaded. This PK profile is unusual among obesity drugs and is a distinct practical consideration vs weekly-injected GLP-1s.
In plain English
It stays in the body for about 9 days — much longer than most drugs
Tesofensine has an unusually long half-life of about 9 days. The liver converts it to an active breakdown product (M1/NS2360) that also works. Because the drug lingers, it takes 3–5 weeks to reach a stable blood level. This is why the trials ramped up doses slowly over weeks and why blood pressure and heart rate monitoring is most important early on. The 9-day half-life is very different from weekly-injected GLP-1 drugs.
- 06
What the Tesomet combination is actually doing
Tesomet is tesofensine 0.5 mg co-formulated with metoprolol 50 mg (a β1-selective adrenergic blocker). The pharmacologic logic is to blunt the heart-rate rise driven by tesofensine's noradrenergic activity without blocking the central NE-driven appetite effect (metoprolol is hydrophilic and does not meaningfully enter the CNS at this dose). Huynh 2022 and Saniona post-marketing data from Mexico suggest HR returns closer to baseline with metoprolol co-administration while weight loss is preserved — but no head-to-head Tesomet-vs-tesofensine-monotherapy RCT has been published to quantify the safety/efficacy trade exactly.
In plain English
Why Tesomet pairs tesofensine with a beta-blocker
Tesomet pairs tesofensine with metoprolol, a beta-blocker that slows heart rate. The idea: metoprolol cancels out the heart-rate increase caused by tesofensine's norepinephrine effect, while leaving the appetite-suppression effect mostly intact — metoprolol doesn't cross into the brain much at this dose. Data from the hypothalamic obesity trial and Mexico post-market surveillance suggest heart rate does return closer to normal with the combination, while weight loss is preserved. But no head-to-head trial comparing tesofensine alone versus tesofensine-plus-metoprolol has been published.