Tesofensine

What is Tesofensine?

Tesofensine is an oral small-molecule triple monoamine reuptake inhibitor that blocks the reuptake of serotonin, noradrenaline, and dopamine — the three neurotransmitters most involved in appetite, satiety, and reward. Originally developed by NeuroSearch for Alzheimer's and Parkinson's disease, weight loss was observed as a "side effect" in those trials, redirecting development toward obesity. In a Phase 2 trial published in The Lancet (203 patients, 24 weeks), tesofensine 0.5 mg plus diet produced 9.2% average weight loss versus 2.0% with diet plus placebo. The investigators suggested this might be about twice what approved drugs of the time achieved, but that was a cross-trial comparison, not a head-to-head result. In 2013 The Lancet attached an expression of concern to the paper after a Danish regulatory inspection found that some adverse events had not been reliably recorded. It is not a peptide, but is widely discussed alongside peptides in the weight loss and compounding pharmacy space. It is not approved anywhere. A technical committee of COFEPRIS, Mexico's regulator, gave a non-binding favorable opinion in February 2023, but the agency withheld approval in November 2024; partner Medix resubmitted in February 2025 and was still pursuing approval as of August 2026. Tesomet, a separate investigational combination of tesofensine with the beta-blocker metoprolol, holds FDA orphan drug designation for Prader-Willi syndrome and hypothalamic obesity.

What Tesofensine Is Investigated For

Tesofensine is investigated primarily for general obesity, hypothalamic obesity, and Prader-Willi syndrome hyperphagia, and the strongest peer-reviewed evidence is the Phase 2 TIPO-1 trial published in The Lancet (203 patients, 24 weeks). With diet, tesofensine produced average weight loss of 4.5%, 9.2%, and 10.6% at 0.25, 0.5, and 1 mg, versus 2.0% with placebo. The paper has carried an expression of concern since 2013 over incomplete adverse-event recording. It is not approved in Mexico or anywhere else: a COFEPRIS technical committee issued a non-binding favorable opinion in February 2023, but approval was withheld in November 2024, and the application Medix resubmitted in February 2025 was still pending as of August 2026. Tesomet, the tesofensine-plus-metoprolol combination, is a separate investigational product with FDA orphan drug designation for hypothalamic obesity and Prader-Willi syndrome. The honest caveats are substantial. Tesofensine is not a peptide but a small-molecule triple monoamine reuptake inhibitor, it is not FDA-approved for any indication, and the 372-patient Mexican Phase 3 trial is described only in company statements (about 10% weight loss at 0.5 mg over 24 weeks), not in a peer-reviewed journal — leaving long-term cardiovascular and psychiatric safety in larger populations inadequately characterized. The dose-dependent heart rate increase (~7.4 bpm at 0.5 mg) is a meaningful concern, serotonergic drug interactions (SSRIs, SNRIs, MAOIs, triptans) carry serotonin syndrome risk, and in a December 2025 warning letter FDA listed tesofensine among ingredients ineligible for use in 503A human drug compounding.

History & Discovery

Tesofensine (NS2330) was discovered at NeuroSearch, a Danish CNS-focused biotech, as a triple monoamine reuptake inhibitor — blocking presynaptic transporters for serotonin, noradrenaline, and dopamine. The original development thesis was neurodegenerative: NeuroSearch tested tesofensine in Phase 2 trials for Alzheimer's disease and Parkinson's disease in the early 2000s, partly with Boehringer Ingelheim, where it did not show convincing benefit: a 430-patient, 14-week Alzheimer's trial was negative, a trial in early Parkinson's showed no significant benefit, and a trial in advanced Parkinson's showed only modest effects without a clear dose response. The neurology programme was large and precisely dated: the 430-patient Alzheimer's trial (NCT00153010) began in February 2003, the 254-patient advanced-Parkinson's ADVANS study (NCT00148512) in March 2003, and the 261-patient early-Parkinson's trial (NCT00148486) in June 2003, preceded by a 9-patient acute study in advanced Parkinson's published in 2004. What investigators noticed in those trials was unexpected weight loss — substantial enough to redirect the molecule's development entirely toward obesity. The pivot was not an anecdote but a quantified finding: a pooled analysis of four of these neurology trials (740 patients on tesofensine, 228 on placebo, 14 weeks, with no diet or lifestyle programme at all) found mean weight changes of +0.5%, −0.5%, −0.9%, −1.8%, and −2.8% across placebo and the 0.125, 0.25, 0.5, and 1.0 mg doses, and among the obese subgroup 2.1%, 8.2%, 14.1%, 20.9%, and 32.1% of patients achieved at least 5% weight loss. The authors characterised this as roughly 4% placebo-subtracted weight loss over 14 weeks without any lifestyle therapy — comparable to sibutramine, but with no blood-pressure effect at the doses analysed. FDA endorsed a Phase 3 obesity programme around 2009. The pivotal Phase 2 obesity study (TIPO-1) was published in The Lancet in 2008, with 203 patients across five Danish centers showing dose-dependent weight loss up to 10.6% at the 1 mg dose over 24 weeks, and 9.2% at the more tolerable 0.5 mg dose. In 2013 The Lancet attached an expression of concern to the TIPO-1 paper after an inspection by the Danish Health and Medicines Authority found that adverse events had not been reliably recorded. By the sponsor's own count the molecule has now been through 34 clinical trials with 1,921 patients exposed to therapeutic doses for up to a year. NeuroSearch transferred tesofensine to the Danish company Saniona in October 2014. Saniona licensed Mexico and Argentina to Medix, which ran a 372-patient Phase 3 trial and filed in Mexico at the end of 2019. A COFEPRIS technical committee issued a non-binding favorable opinion in February 2023, but approval was withheld in November 2024; Medix resubmitted in February 2025 and was still pursuing approval as of August 2026. Tesomet pairs tesofensine with metoprolol, a beta-blocker, to offset the dose-dependent heart rate increase observed with tesofensine alone. The molecule has FDA orphan drug designation for hypothalamic obesity and Prader-Willi syndrome but is not approved in the US for any indication; the sponsor reports that FDA confirmed Tesomet may proceed via the 505(b)(2) regulatory pathway for both. Saniona sizes those populations at roughly 25,000 people in the US and 40,000 in Europe for hypothalamic obesity, and 34,000 and 50,000 respectively for Prader-Willi syndrome. A completed 60-patient Phase 2 trial of tesofensine with metoprolol in type 2 diabetes (NCT02737891, 2016-2017) has never been published. Note that tesofensine is a small molecule, not a peptide — it is included on this site because it is widely discussed alongside peptides in the obesity and compounding-pharmacy space.

How It Works

Tesofensine blocks the recycling of three brain chemicals — serotonin, noradrenaline, and dopamine — that control appetite, mood, and reward. By keeping more of these neurotransmitters active in the brain, it reduces hunger, increases the feeling of fullness, and decreases the reward drive to eat. In a two-week human study it did not change total 24-hour energy expenditure, though it slightly raised night-time energy use and fat burning. Research in mice shows it quiets a subset of feeding-promoting neurons in the hypothalamus.

Tesofensine is a triple monoamine reuptake inhibitor that blocks the presynaptic transporters for serotonin (SERT), noradrenaline (NET), and dopamine (DAT), increasing synaptic concentrations of all three neurotransmitters. The inhibition is not balanced: reported IC50 values are 1.7 nM at NET, 6.5 nM at DAT, and 11 nM at SERT, so it is most potent at the noradrenaline transporter and weakest at the serotonin transporter. Tesofensine is a tropane alkaloid — the same chemical family as cocaine — and 2025 cryo-EM structures resolved it bound to all three human transporters, showing the tropane ring in nearly the same pocket pose as cocaine while binding DAT with roughly 50-fold higher affinity, and locking the transporter in an outward-facing conformation that distinguishes it from reuptake inhibitors such as centanafadine and ansofaxine. The primary weight loss mechanism is appetite suppression (reduced food intake), with at most a minor contribution from energy expenditure. In overweight men, tesofensine did not significantly change total 24-hour energy expenditure but raised night-time expenditure by 4.6% and increased 24-hour fat oxidation. In human PET imaging, dopamine transporter occupancy rose from 18% to 77% across doses of 0.125 to 1 mg, with half the maximal effect at about 0.25 mg. A 2024 study in mice and rats found that tesofensine inhibits a subset of GABAergic neurons in the lateral hypothalamus — a brain region directly involved in feeding behavior — providing a specific neuroanatomical target for its anorectic effects. The triple reuptake profile distinguishes it from SSRIs/SNRIs (which affect only 1-2 monoamines) and from GLP-1 agonists (gut-hormone mimics that act on GLP-1 receptors in the brainstem and hypothalamus). In Phase 2 (203 patients, 24 weeks, Lancet), dose-dependent weight loss was observed: 4.5% (0.25 mg), 9.2% (0.5 mg), and 10.6% (1.0 mg) vs 2.0% placebo, all alongside an energy-restricted diet (modified intention-to-treat analysis), with 0.5 mg considered the optimal therapeutic dose balancing efficacy and cardiovascular safety.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Tesofensine:

• 01Independent, peer-reviewed publication of the 372-patient Mexican Phase 3 efficacy and safety data — the main dataset behind the COFEPRIS application. The trial is not registered on ClinicalTrials.gov under any sponsor, so there is no public protocol, endpoint list, or results posting against which the company's summary can be checked.
• 02Effect on muscle and lean mass — a 2026 systematic review of randomized trials in acquired hypothalamic obesity found that Tesomet reduced both body weight and lean mass, and rated the certainty of the body-composition evidence as low (PMID: 42644866).
• 03Long-term cardiovascular safety beyond 24 weeks at scale — TIPO-1 was a 24-week study with a 2013 expression of concern over adverse-event recording, and the 372-patient Mexican Phase 3 trial has not been published in a peer-reviewed journal, leaving multi-year cardiovascular outcomes incompletely characterized.
• 04Psychiatric safety in larger and more diverse populations — monoamine reuptake inhibition carries rare but serious psychiatric risks, and the published data are inadequate to estimate event rates with confidence. The clearest existing signal sits in the posted results of a 37-volunteer Phase 1 study rather than in any publication: serious events of hypomania, depression, impulse-control disorder, and an unspecified nervous system disorder were recorded there, and insomnia is the characteristic adverse effect of the whole monoamine-targeting weight-loss class.
• 05Whether combination with GLP-1 agonists is safe and effective — mechanistically additive (central dopamine plus peripheral incretin signaling) but untested in dedicated trials.
• 06Direct head-to-head comparisons with semaglutide, tirzepatide, naltrexone-bupropion, and phentermine-topiramate.
• 07Hypothalamic obesity and Prader-Willi syndrome — orphan-designated indications where tesofensine's dopaminergic mechanism may be uniquely useful, but only small Phase 2 trials exist — 21 adults with hypothalamic obesity and 18 people with Prader-Willi syndrome — and the planned Phase 2b trials were withdrawn before enrollment for financial reasons.
• 08Pediatric and adolescent use — largely uncharacterized; the only adolescent exposure is the 18-participant Tesomet trial in Prader-Willi syndrome.
• 09Sex differences — females with reduced kidney function showed about 62% higher exposure than males with normal function in the population pharmacokinetic analysis, and in rats weight loss was greater and more uniform in females. Neither observation has been followed up in a human trial, and no dose adjustment has been proposed.
• 10Type 2 diabetes — Saniona completed a 60-patient Phase 2 trial of tesofensine with metoprolol in type 2 diabetes (NCT02737891) in 2017, and no results have been published or posted.

Forms & Administration

Tesofensine is taken as a once-daily oral tablet, typically 0.5 mg. The 0.25 mg dose is effective but less potent; the 1.0 mg dose produces more weight loss but more side effects. Tesomet, an investigational product used only in clinical trials, combines tesofensine with metoprolol to manage heart rate effects. It is not approved for sale in any country. Some US compounders and online sellers offer it, but FDA considers it ineligible for 503A compounding, and it has been sold online labeled as a dietary supplement.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

Tesofensine is not FDA-approved. It is not approved in any other country either. The doses cited reflect clinical trial protocols only, not prescribing guidance, and any use outside a clinical trial is unsupervised and unregulated.

Timeline of Effects

Common Questions

Who Tesofensine Is NOT For

Drug & Supplement Interactions

The most clinically important interaction domain is serotonergic: tesofensine combined with SSRIs, SNRIs, MAOIs, triptans, tramadol, MDMA, or other serotonergic agents raises serotonin syndrome risk through additive serotonergic load. MAOIs in particular should not be combined with tesofensine. Because tesofensine's half-life is about 10 days and its active metabolite's longer still, any washout before starting an MAOI would be far longer than for typical antidepressants, and no validated washout interval has been published. The dopaminergic activity introduces theoretical interactions with antipsychotics (which block dopamine receptors and could be antagonized) and with dopamine-replacement therapy in Parkinson's disease (additive dopaminergic load). The noradrenergic activity adds to the cardiovascular effects of stimulants, decongestants (pseudoephedrine), and certain ADHD medications. The Tesomet combination with metoprolol is itself a designed pharmacokinetic and pharmacodynamic strategy to manage the cardiovascular effect of tesofensine. Tesofensine is partly cleared by the liver enzyme CYP3A4: in a modeling analysis, the CYP3A4 inhibitor itraconazole reduced tesofensine clearance by 38% and raised predicted exposure by 63%, so strong CYP3A4 inhibitors could raise its levels and side effects.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions