Tesofensine

Tesofensine is an experimental weight-loss drug. In one mid-size trial it had a genuinely large short-term effect — and there’s also a long list of reasons to be careful with it. The first thing to get straight is what it actually is: tesofensine is a small molecule, an oral triple monoamine reuptake inhibitor (a drug that raises levels of three brain signaling chemicals at once), and it comes from a chemical family called the phenyltropanes. It is not a peptide, not a hormone, and not in the same family as the GLP-1 drugs (the newer injectable weight-loss medicines like semaglutide) it often gets compared to. No major regulator has approved it — not the FDA, not the EMA, and not (as of mid-2026) Mexico’s COFEPRIS — and it is banned in sport as a stimulant. This page is educational and harm-reduction oriented, and it contains no dosing, cycles, or sourcing information.

What it is

Tesofensine (lab code NS2330) is a small-molecule oral triple monoamine reuptake inhibitor. In plain terms, it stops your nerve cells from soaking up three signaling chemicals — noradrenaline, dopamine, and serotonin — so more of all three stay active in the brain. Chemically, it belongs to the phenyltropane family. To be completely clear: it is not a peptide, not a hormone, and not a growth factor.

In obesity studies, the main effect seen is appetite suppression (it makes you feel less hungry), and possibly a small bump in the calories you burn at rest. Animal research in rats traces most of that appetite effect to two brain pathways it indirectly switches on — the α1-adrenoceptor and dopamine D1 receptor pathways (Axel et al., Neuropsychopharmacology 2010). It was first developed by NeuroSearch as a treatment for Parkinson’s and Alzheimer’s disease, but it didn’t work well enough for those, so the project was dropped. The weight loss people noticed as a “side effect” is what sent it down the obesity research path instead. Tesomet is a separate, company-owned product that combines tesofensine with metoprolol (a beta-1 blocker — a heart medication added on purpose to soften tesofensine’s effects on the heart).

The claims

Tesofensine gets talked up — mostly in grey-market and “research chemical” weight-loss circles — as a powerful appetite suppressant that can match or beat the approved obesity drugs. There’s a real grain of truth behind the hype: one Phase 2b trial (covered below) found weight loss in the 9–11% range at the higher doses once you subtract out the placebo effect, which is genuinely large for a single drug. What the evidence does not back up is the suggestion that this is proven, approved, or shown to beat the modern GLP-1/GIP drugs — none of that is true.

What the evidence actually shows

Here’s the honest summary: there is one mid-size Phase 2 obesity trial with a striking result, a couple of small supporting human studies, and a Phase 3 dataset that the company has reported but that hasn’t been peer-reviewed (independently checked by outside experts). That adds up to preliminary human evidence — not the large, repeated, long-term safety-and-effectiveness track record that backs the approved obesity drugs.

• TIPO-1 (Phase 2b — the key trial): Astrup et al., Lancet 2008 (NCT00394667). This was a randomized, double-blind, placebo-controlled trial (the gold-standard setup, where neither patients nor doctors know who got the real drug) in 203 obese adults over 24 weeks plus diet, run across 5 Danish/European obesity centers. Once the placebo effect was subtracted out, average weight loss came to roughly 4.5% / 9.2% / 10.6% at the 0.25 / 0.5 / 1.0 mg doses; the authors preferred the 0.5 mg dose for striking a better balance between results and side effects. That is a large effect for a single drug — but it is one mid-size Phase 2 trial, it came before the GLP-1/GIP era, and head-to-head data versus semaglutide or tirzepatide do not exist.
• Mechanistic/metabolic human study: Sjödin et al., Int J Obes 2010, looked at how tesofensine affects energy use and appetite in overweight and moderately obese men — and the results support the idea that it works mainly by curbing appetite.
• Tesomet in hypothalamic obesity (Phase 2): Huynh et al., Eur J Endocrinol 2022 (NCT03845075). This was a small (n=21), 24-week randomized controlled trial. It showed roughly −6.3% to −6.8% placebo-subtracted weight change, and notably, with metoprolol added in, there was no significant heart-rate or blood-pressure increase. Encouraging, but still preliminary given how few people took part.
• Medix Phase 3 (obesity): company readouts describe it as hitting its targets, but there is no confirmed peer-reviewed full publication. Until it’s published, treat the Phase 3 results as company-reported only.

Legal and regulatory status

Not approved by any major regulator. Tesofensine has not been approved by the FDA or EMA; in the US it is still investigational (an IND, meaning it can only be used under a research permit), and it has never been sold in the US or EU.

Mexico (COFEPRIS): Medix ran a Phase 3 program and filed a new drug application. In February 2023, COFEPRIS’s technical committee issued a favorable but non-binding technical opinion — which is explicitly not a green light to sell the drug. According to the most recent public Saniona/Medix updates (November 2024, with a planned resubmission of the paperwork around February 2025), tesofensine had not received final COFEPRIS marketing approval; the application was confirmed as not yet approved. There’s no reliable confirmation that an approved, launched product or brand name exists, so any “approved in Mexico” claim should be treated as unconfirmed or false.

Tesomet (tesofensine + metoprolol) was Saniona’s own program aimed at hypothalamic obesity and Prader-Willi syndrome. Those Phase 2b programs were voluntarily paused — reportedly for funding reasons, not because of safety or effectiveness problems — as part of a 2022 company restructuring. Tesomet is also investigational and unapproved.

Anti-doping (WADA). Tesofensine is prohibited. On the 2025 WADA Prohibited List (in effect 1 Jan 2025), tesofensine (along with midodrine) was added as a named example under S6 Stimulants, prohibited in-competition (meaning during competition periods). USADA specifically warned that it’s showing up more and more in dietary supplements. As a stimulant it counts as a “specified” substance, but it is still banned — a stricter status than the GLP-1 agonists, which only sit on WADA’s Monitoring Program and are not prohibited. So tesofensine is banned as a stimulant (S6), not as a hormone or growth factor.

Bottom line on status: it’s research/trial-grade everywhere, with no major-regulator approval as of mid-2026. Even so, it’s sold widely as a “research chemical” / grey-market weight-loss product, which means unapproved and unregulated.

Safety

The side effects reported most consistently in obesity trials are dry mouth, headache, insomnia and other sleep problems, nausea, constipation or diarrhea, and mood/psychiatric effects.

The biggest worry is the heart. On its own, tesofensine pushed up heart rate and blood pressure, and the more you took, the bigger the rise; the Lancet trial and the commentary alongside it specifically flagged those blood-pressure and heart-rate increases, plus possible psychiatric effects. This mix of brain-chemical and stimulant-like (sympathomimetic) effects is the very same class of problem that got sibutramine pulled from the market. The Tesomet (with metoprolol) version was built specifically to counteract those heart effects, and the small Phase 2 didn’t show a significant heart-rate or blood-pressure change — but the long-term effects on the heart and mind, across large numbers of people, are simply not established.

One last point: grey-market or “research-grade” tesofensine adds extra, undocumented risks — you can’t be sure of what’s actually in it, how pure it is, or how strong it is — and that’s all stacked on top of a drug whose long-term safety is already unproven.

Bottom line

Tesofensine is an investigational small-molecule triple monoamine reuptake inhibitor — and, to be clear, not a peptide. It has a genuinely impressive short-term weight-loss signal in one mid-size Phase 2 trial (TIPO-1) plus a couple of small supporting studies. But that’s the entire human evidence base: it’s preliminary, it predates the modern GLP-1/GIP era, there’s no head-to-head data, and the larger Phase 3 dataset is still company-reported and unpublished. It is not approved by the FDA, EMA, or (as of mid-2026) COFEPRIS, its stimulant-like profile raises the same heart and psychiatric concerns that sank sibutramine, and it is banned in sport as an S6 stimulant. The version sold online as a “research chemical” piles unverified identity, purity, and dosing on top of an already-unproven drug.

Evidence grade: 7/10 · Moderate.

Sources

• Astrup A, et al. Effect of tesofensine on bodyweight loss, body composition, and quality of life in obese patients: a randomised, double-blind, placebo-controlled trial. Lancet 2008;372(9653):1906–13 (TIPO-1; doi:10.1016/S0140-6736(08)61525-1)
• ClinicalTrials.gov NCT00394667 (TIPO-1)
• Sjödin A, et al. The effect of the triple monoamine reuptake inhibitor tesofensine on energy metabolism and appetite in overweight and moderately obese men. Int J Obes 2010;34(11):1634–43 (PMID 20479765)
• Axel AMD, et al. Neuropsychopharmacology 2010 (DIO rat; α1/D1 mechanism)
• Huynh K, et al. Randomized controlled trial of Tesomet for weight loss in hypothalamic obesity. Eur J Endocrinol 2022;186(6):687–700 (doi:10.1530/EJE-21-0972; PMID 35294397)
• ClinicalTrials.gov NCT03845075 (Tesomet, hypothalamic injury-induced obesity)
• Saniona–Medix license agreement (Feb 2016, Mexico/Argentina)
• Saniona tesofensine pipeline page (developer/Medix/COFEPRIS status)
• Saniona/Inderes update: “Mexican Application for Tesofensine Not Yet Approved” (late 2024)
• USADA Athlete Advisory — 2025 WADA Prohibited List (tesofensine added as named S6 stimulant example)
• WADA Prohibited List (official)
• Tesofensine, Wikipedia (background/cross-check only)