Tesofensine is a small synthetic molecule, not a peptide, and it has no amino-acid chain, no parent protein and no amino-acid length. It belongs to a class called triple monoamine reuptake inhibitors. A monoamine is a neurotransmitter built around a single amine group, and dopamine, norepinephrine and serotonin are the three that matter here. Reuptake is the process by which a transporter protein pumps a transmitter back into the nerve cell after it fires, and blocking that pump leaves more transmitter in the synapse, the gap between neurons.
The Danish company NeuroSearch A/S developed tesofensine, originally called NS 2330, as a treatment for Parkinson's and Alzheimer's disease, and the compound was in phase 2 testing for both by March 2001 [40][16]. NeuroSearch ran the early program with Boehringer Ingelheim [16]. The neurodegenerative trials did not deliver a benefit, but treated patients lost weight, and the company redirected the molecule to obesity [16][2]. That pivot made weight loss the center of the program [1][2].
The human data point to a real but narrow effect: oral tesofensine lowers body weight mainly by reducing appetite, with a smaller rise in energy expenditure [1][7]. Its liabilities are cardiovascular and psychiatric [1][5], and the main obesity trial carries a 2013 expression of concern [12]. As of October 2026, no finished tesofensine drug appears in FDA's NDC directory, which carries the substance only as a bulk ingredient [39]; the orphan designation record covers a tesofensine-metoprolol combination for hypothalamic obesity, granted on July 21, 2021, and lists it as not approved for that indication [27]. The sponsor withdrew its two planned phase 2 trials in December 2022 [32][37].
Key takeaways
- Tesofensine is a small synthetic molecule, not a peptide, that blocks the reuptake of dopamine, norepinephrine and serotonin [1][24].
- In the 24-week TIPO-1 trial, the middle dose produced 9.2% weight loss against 2.0% with diet and placebo, while heart rate rose 7.4 beats per minute and dry mouth, nausea, constipation and insomnia were common [1].
- The Parkinson's and Alzheimer's programs failed [16], and two planned tesofensine-metoprolol trials were withdrawn in 2022 [32][37]. WADA names tesofensine as an S6 stimulant [28].
How it works
Blocking three monoamine transporters
Tesofensine works at the first step of monoamine signaling, the transporter that clears the synapse. Each of the three transmitters has its own transporter, and tesofensine inhibits all three, which is why the class is called triple reuptake inhibition. The immediate effect is a longer and stronger signal at dopamine, norepinephrine and serotonin synapses.
The structural evidence comes from cryo-electron microscopy, a method that images frozen molecules at near-atomic resolution. Structures of the dopamine transporter bound to tesofensine showed the drug holding the transporter in an outward-facing conformation, the shape in which it opens toward the synapse [24]. The same study found that three other triple reuptake inhibitors, centanafadine, ansofaxine and nefazodone, capture the inward-facing form instead, so the binding pose differs across the class [24].
In humans, positron emission tomography measured how much of the dopamine transporter tesofensine occupies. Positron emission tomography, or PET, uses a short-lived radioactive tracer that binds a target so the target can be imaged in a living brain. Across the doses tested, striatal occupancy rose from 18% to 77%, with a maximum of about 80% and half of that effect reached at a plasma concentration of about 4 ng/mL [9]. The striatum is a deep brain region dense in dopamine terminals.
Appetite suppression through alpha-1 and dopamine D1 signals
The appetite effect runs through two receptors downstream of the transporters. Alpha-1 adrenoceptors are the receptors that norepinephrine activates on blood vessels and in the brain, and dopamine D1 receptors are the excitatory dopamine receptor family. Both are G-protein coupled receptors, the large family of cell-surface switches that most neurotransmitters use.
The clearest experiment used diet-induced obese rats, animals made fat by a high-energy diet. Tesofensine lowered food intake with an ED50 of 1.3 mg/kg, meaning that dose produced half its maximum effect [18]. Prazosin, an alpha-1 blocker, almost completely reversed the hypophagia, and a D1 blocker partially reversed it, while blockers of alpha-2, D2, D3 and serotonin 2A/2C receptors did nothing [18].
A 2024 study traced the effect to a specific circuit. GABAergic neurons release GABA, the brain's main inhibitory signal, and a subset of them in the lateral hypothalamus, a region that drives feeding, became quieter under tesofensine [23]. In mice engineered to express a light-sensitive channel in those neurons, the drug suppressed a subset of them, and chemogenetic silencing, a technique that switches chosen neurons off with an engineered receptor, enhanced the food-suppressing effect [23]. Tesofensine also prolonged weight loss produced by 5-HTP, a serotonin precursor, and blocked the usual weight rebound after treatment stopped [23].
Energy expenditure and the dopamine deficit of obesity
Weight loss from tesofensine is not explained by appetite alone, which points to a second effect on energy balance. Energy expenditure is the total energy the body burns, and fat oxidation is the rate at which it burns fat.
In the human chamber study, 32 overweight or moderately obese men kept their usual food intake and activity. Over two weeks, tesofensine produced 1.8 kg more weight loss than placebo, higher ratings of satiety and fullness, lower prospective food intake, 4.6% higher energy expenditure at night and 18 g more 24-hour fat oxidation [7]. Total 24-hour energy expenditure did not change, so the night-time difference is the signal and it is small [7].
Rat work supports the same split between appetite and expenditure. In a 28-day study, tesofensine at 1.0 and 2.5 mg/kg produced 5.7% and 9.9% weight loss, while pair-fed rats, given the same amount of food as treated rats, returned to baseline weight, which suggests that the drug also raised energy use [19].
Obesity in rats comes with a dopamine deficit. Diet-induced obese rats had lower extracellular dopamine in the nucleus accumbens and prefrontal cortex than chow-fed rats, and a single tesofensine dose normalized accumbal dopamine in the obese animals without changing it in lean animals [20]. The nucleus accumbens is a reward-related part of the striatum.
Why the combination adds metoprolol
Raising monoamine signaling also raises heart rate and blood pressure, because norepinephrine is the main signal of the sympathetic nervous system, the fight-or-flight branch. Metoprolol is a beta-1 blocker, a drug that blocks the heart's beta-1 adrenoceptor and slows it. Pairing the two aims to keep the weight-loss effect and cancel the cardiovascular one.
In telemetered rats, tesofensine caused dose-dependent hypophagia together with higher heart rate and blood pressure. Metoprolol at 10 to 20 mg/kg fully prevented the cardiovascular effects and left the food-intake effect intact, while telmisartan, an angiotensin receptor blocker, only partly reversed the blood-pressure rise and did not touch heart rate [21].
The clinical rationale was tested in a phase 1 interaction study. As the tesofensine dose rose, the metoprolol dose needed to hold 24-hour mean heart rate flat rose steeply, which showed that the two drugs interact as intended [31]. The fixed-dose combination tested in the later trials is the one FDA designated for hypothalamic obesity [27].
What has been studied in humans
Tesofensine has been given to humans in randomized trials for Parkinson's disease, Alzheimer's disease and obesity [1][2][3], and in smaller trials for type 2 diabetes, Prader-Willi syndrome and hypothalamic obesity [10][11][33]. Volunteer and pharmacokinetic studies have examined abuse potential, plasma half-life and urine metabolism [6][14][15]. The record is broad but not deep: most trials ran 14 to 24 weeks, and ClinicalTrials.gov lists 13 studies, none of them phase 3 [36].
The obesity program produced the strongest signal. In TIPO-1, 203 adults with a body mass index of 30 to 40 followed an energy-restricted diet and took tesofensine or placebo for 24 weeks; mean weight loss was 4.5%, 9.2% and 10.6% at the ascending doses against 2.0% with diet and placebo [1]. The middle dose raised heart rate by 7.4 beats per minute, and dry mouth, nausea, constipation, hard stools, diarrhea and insomnia were the most common adverse events [1]. An earlier meta-analysis of four Parkinson's and Alzheimer's trials, covering 968 participants, showed the same dose-dependent pattern without any weight-loss program: weight change ran from a 0.5% gain on placebo to a 2.8% loss at the highest dose over 14 weeks [2].
Mechanistic human studies separated appetite from expenditure. Thirty-two overweight or moderately obese men kept their usual food intake and activity; over two weeks, tesofensine produced 1.8 kg more weight loss than placebo, higher satiety and fullness, lower prospective food intake, 4.6% higher night-time energy expenditure and 18 g more 24-hour fat oxidation [7]. In a two-part appetite study, the composite satiety score rose with dose at week 12 and correlated with 24-week weight loss, then fell toward baseline by week 24 and returned to baseline after the drug was withdrawn [8]. Restarting treatment raised the score again, which suggests the appetite effect depends on continued treatment [8].
The neuroscience indications came first and did not succeed. A single-dose study in nine patients with advanced Parkinson's disease found no change in parkinsonian scores, alone or with levodopa [4]. A 261-patient phase 2 trial in early Parkinson's disease found no significant benefit at 14 weeks; the highest dose beat placebo at week 6, but the effect did not last, and weight loss and raised heart rate were common at that dose [3][36]. ADVANS, a 14-week trial in advanced Parkinson's disease with motor fluctuations, reported a 4.7-point improvement in daily living plus motor scores at one dose and a 7.1% reduction in off time, the periods when levodopa stops working, at another, with gastrointestinal and neuropsychiatric adverse events more frequent than placebo [5]. The Alzheimer's program ran a 430-participant phase 2 trial with a cognitive score as its primary endpoint [34], and a 2009 review concluded that tesofensine was ineffective for neurodegenerative disease [16].
The most recent program pairs tesofensine with metoprolol. In a 21-adult trial in hypothalamic obesity, a form of obesity caused by injury to the hypothalamus, the combination produced 6.3% additional weight loss against placebo over 24 weeks and did not differ significantly in heart rate or blood pressure [10]. Sleep disturbance occurred in 50% on the combination against 13% on placebo, dry mouth in 43% against 0%, and headache in 36% against 0%, and one participant stopped treatment after worsened pre-existing anxiety [10]. Registry results from the 24-week open-label extension show that, from week 24 to week 48, the placebo group lost 5.5 kg after switching to active treatment while the originally active group gained 1.4 kg [30].
Two smaller trials tested the combination in other conditions. In type 2 diabetes, a 60-participant phase 2 trial found a lower 24-hour mean heart rate on tesofensine plus metoprolol than on placebo, a 3.5 kg weight loss against 0.3 kg, and an HbA1c of 7.3% against 7.4%, where HbA1c tracks average blood glucose over about three months [11]. In Prader-Willi syndrome, an 18-participant trial reported a 4.09% weight loss in the adult group on the higher dose against 0.38% on placebo, but three of the six adults on that dose had a serious adverse event [33].
The remaining human studies round out the picture. In 52 recreational stimulant users, tesofensine produced subjective effects no different from placebo and lower than d-amphetamine, which suggests low abuse potential [6]. In a population pharmacokinetic model built from 320 patients with Alzheimer's disease, tesofensine had a plasma half-life of about 234 hours and the active metabolite M1 about 374 hours, so the drug and its metabolite accumulate slowly and persist for weeks [14]. A 2026 urine study in six volunteers identified four principal metabolites and detection windows of up to 500 hours after a supplement dose [15].
The limits are substantial. The efficacy evidence for tesofensine alone in obesity rests on one phase 2 trial, and the Lancet attached an expression of concern to it in 2013; a July letter by the trial authors followed the same year [1][12][13]. A 140-participant single-group study collected long-term safety data in 2007 and 2008, but the registry has no posted results [38]. No phase 3 trial is registered, and the two planned phase 2 trials were withdrawn before any participant was randomized [36][32][37].
Doses studied in human trials
As of October 2026, tesofensine has no FDA-approved finished product and no registered phase 3 trial. Regimens below are those reported in the cited human trials.
Tesofensine 0.25, 0.5 or 1.0 mg once daily for 24 weeks, with an energy-restricted diet; placebo comparator.
203 adults with obesity and a body mass index of 30 to 40 at five Danish obesity centers; 161 completed the study.
Tesofensine 0.125, 0.25, 0.5 or 1.0 mg once daily for 14 weeks.
968 participants: 740 assigned tesofensine and 228 assigned placebo, treated for 14 weeks without a weight-loss program.
Tesofensine 0.25, 0.5 or 1.0 mg once daily for 14 weeks; placebo comparator.
261 adults with Parkinson's disease for less than five years who were not yet receiving dopaminergic treatment.
Tesofensine 0.125, 0.25, 0.5 or 1.0 mg once daily for 14 weeks; placebo comparator.
Adults with advanced Parkinson's disease and levodopa-related motor fluctuations.
Tesofensine 2.0 mg daily for 7 days, then 1.0 mg daily for 7 days; placebo comparator.
32 healthy overweight or moderately obese men, instructed to keep food intake and physical activity constant.
Tesofensine 0.25, 0.5 or 1.0 mg once daily in part 1; 0.5 or 1.0 mg once daily in part 2.
158 participants in part 1 and 113 completers in part 2, all from the phase 2 obesity program.
Tesofensine 0.125 to 1 mg once daily for 8 to 12 days.
Human volunteers imaged after 8 to 12 days of dosing; the abstract does not state the group size.
Tesomet 0.5 mg tesofensine with 50 mg metoprolol once daily for 24 weeks; placebo comparator.
21 adults with hypothalamic obesity, 16 of them female; 18 completed 24 weeks.
Tesofensine 0.5 mg with metoprolol 100 mg once daily for 90 days; placebo comparator.
60 adults with type 2 diabetes, 30 in each arm.
Lab and animal studies
The animal literature covers whether weight loss is sustained, what the drug does to dopamine circuits, and why the heart rate rises. In a 28-day rat study, tesofensine at 1.0 or 2.5 mg/kg produced 5.7% and 9.9% weight loss, compared with 7.6% for sibutramine and only a transient effect for rimonabant; pair-fed rats returned to baseline, which suggests that tesofensine also raised energy expenditure [19]. In a separate 28-day study, tesofensine reduced caloric intake and weight gain and lowered striatal D2/D3 receptor availability, a pharmacological effect that did not correlate with the weight change [26].
The dopamine system is part of the story. Diet-induced obese rats had lower extracellular dopamine in the nucleus accumbens and prefrontal cortex than chow-fed rats, and a single tesofensine dose normalized accumbal dopamine in the obese animals without changing it in lean animals [20]. Chronic treatment also changed striatal D2 receptor expression and transporter binding [20].
The newest work adds circuit and structural detail. In mice and rats, tesofensine silenced a subset of GABAergic neurons in the lateral hypothalamus, and chemogenetic silencing of those neurons enhanced its food-suppressing effect [23]. Cryo-electron microscopy of the dopamine transporter bound to tesofensine showed that the drug stabilizes an outward-facing conformation of the transporter [24].
Side-effect biology has been modeled too. In rats, tesofensine produced head-weaving stereotypy, a purposeless repetitive movement, only in females, and orolingual dyskinesia most often, at lower levels than dopaminergic appetite suppressants [25]. Metoprolol prevented the heart-rate and blood-pressure rise in telemetered rats without reducing the appetite effect, and telmisartan only partly reversed the blood-pressure rise [21].
The active metabolite M1 contributes. In mice, M1 inhibited the dopamine transporter with an EC50 four to five times higher than tesofensine, but its steady-state concentrations were about eight times higher, so it adds to the overall effect [22].
Research in detail
Phase 2, randomized, double-blind, placebo-controlled, multicenter trial with a two-week diet run-in and 24 weeks of treatment. · 203 adults with obesity and a body mass index of 30 to 40 at five Danish obesity centers; 161 completed the study.
Mean weight loss was 4.5%, 9.2% and 10.6% at the ascending tesofensine doses against 2.0% with diet and placebo. Heart rate rose by 7.4 beats per minute at the middle dose, and dry mouth, nausea, constipation, hard stools, diarrhea and insomnia were the most common adverse events.
Evidence scope: One phase 2 efficacy trial of 24 weeks; the Lancet attached an expression of concern in 2013, and no phase 3 trial has confirmed the result. Abstract reviewed; full text not read.
Meta-analysis of four randomized, double-blind, multicenter trials, two in Parkinson's disease and two in Alzheimer's disease. · 968 participants: 740 assigned tesofensine and 228 assigned placebo, treated for 14 weeks without a weight-loss program.
Weight change was a 0.5% gain with placebo and losses of 0.5%, 0.9%, 1.8% and 2.8% at the ascending doses. In the obese subgroup, the share reaching at least 5% weight loss rose from 2.1% with placebo to 32.1% at the highest dose, and heart rate rose by up to 6.8 beats per minute with no blood-pressure effect.
Evidence scope: Participants had Parkinson's or Alzheimer's disease, so weight was a secondary observation; the trials lasted 14 weeks and included no diet program. Abstract reviewed; full text not read.
Proof-of-concept, randomized, double-blind, placebo-controlled trial of three daily doses. · 261 adults with Parkinson's disease for less than five years who were not yet receiving dopaminergic treatment.
No significant benefit at 14 weeks. The highest dose beat placebo at week 6 by 3.1 points on the Unified Parkinson's Disease Rating Scale, but the effect was not sustained. Constipation, insomnia and dry mouth were common, and weight loss and raised heart rate were common at the highest dose.
Evidence scope: The authors could not tell whether dopamine reuptake inhibition is insufficient, underdosed, or offset by other physiology; treatment lasted 14 weeks. Abstract reviewed; full text not read.
Phase 2, randomized, double-blind, placebo-controlled, parallel-group trial. · Adults with advanced Parkinson's disease and levodopa-related motor fluctuations.
Adjusted mean differences against placebo were 4.7 points on the daily-living plus motor subscales at one dose and a 7.1% reduction in off time, or 68 minutes, at another. Other doses were not significant, and no dose-response was established.
Evidence scope: Efficacy was modest and not dose-related; gastrointestinal and neuropsychiatric adverse events were more frequent than placebo, especially at higher doses. Abstract reviewed; full text not read.
Single-dose, randomized, double-blind, crossover study with placebo and active controls. · 52 recreational stimulant users.
Tesofensine effects were not significantly different from placebo and were lower than d-amphetamine on all primary and most secondary measures. Effects were lower than or not different from bupropion and atomoxetine.
Evidence scope: Single doses in experienced stimulant users; subjective ratings may not capture real-world abuse, and there was no long-term exposure. Abstract reviewed; full text not read.
Randomized, controlled trial using a respiration chamber, dual-energy X-ray absorptiometry and visual analogue appetite scales. · 32 healthy overweight or moderately obese men, instructed to keep food intake and physical activity constant.
Tesofensine produced 1.8 kg more weight loss than placebo in two weeks, higher satiety and fullness, lower prospective food intake, 4.6% higher night-time energy expenditure and 18 g more 24-hour fat oxidation. Total 24-hour energy expenditure did not change.
Evidence scope: Small, short study in men only; the chamber measures a brief window, so the night-time expenditure result needs confirmation. Abstract reviewed; full text not read.
Two-part study: a 24-week randomized, double-blind, placebo-controlled phase followed by a 24-week open-label phase after a drug-free interval. · 158 participants in part 1 and 113 completers in part 2, all from the phase 2 obesity program.
The composite satiety score rose with dose at week 12 and correlated with 24-week weight loss (r = 0.36). The effect diminished by week 24 and returned to baseline after withdrawal, then rose again when treatment restarted.
Evidence scope: A secondary analysis of appetite ratings; satiety scores are subjective, and the open-label second part has no control group. Abstract reviewed; full text not read.
Positron emission tomography study with a dopamine transporter tracer at steady state after multiple oral doses. · Human volunteers imaged after 8 to 12 days of dosing; the abstract does not state the group size.
Striatal dopamine transporter occupancy rose dose-dependently from 18% to 77%. The maximum was about 80%, and half of that occupancy came at a plasma concentration of about 4 ng/mL.
Evidence scope: The abstract does not state the group size; occupancy is a pharmacodynamic marker rather than a clinical outcome, and the measurement is limited to the striatum. Abstract reviewed; full text not read.
Randomized, double-blind, placebo-controlled trial of 24 weeks. · 21 adults with hypothalamic obesity, 16 of them female; 18 completed 24 weeks.
Tesomet produced 6.3% additional weight loss against placebo, and more participants reached at least 5% loss, 8 of 13 against 1 of 8. Heart rate and blood pressure did not differ significantly; sleep disturbance, dry mouth and headache were more common.
Evidence scope: A 21-person trial; one treatment-related serious adverse event of worsened anxiety, and the efficacy data cover 24 weeks. Abstract reviewed; full text not read.
Phase 2, randomized, double-blind, placebo-controlled trial. · 60 adults with type 2 diabetes, 30 in each arm.
At day 90, 24-hour mean heart rate was 67 beats per minute on tesofensine plus metoprolol and 70 on placebo, with a 3.5 kg weight loss against 0.3 kg. HbA1c was 7.3% against 7.4%.
Evidence scope: Registry results reviewed; no peer-reviewed report of this trial is indexed in PubMed; the trial lasted 90 days, and its primary endpoint was heart rate rather than weight or glucose.
History and where it stands today
Tesofensine moved from a Parkinson's and Alzheimer's candidate to an obesity drug, then to a combination product that stalled.
- 2001NeuroSearch A/S was developing the compound as NS 2330, and by March 2001 it was in phase 2 testing for Alzheimer's disease and Parkinson's disease [40].
- 2004A single-dose, placebo-controlled study in nine patients with advanced Parkinson's disease showed no change in parkinsonian scores when NS 2330 was given alone or with levodopa [4].
- 2007A 261-patient phase 2 trial in early Parkinson's disease reported no significant benefit at 14 weeks; the highest dose beat placebo at week 6, but the effect did not last [3].
- 2008The ADVANS trial in advanced Parkinson's disease found a 4.7-point improvement in daily-living and motor scores at one dose and a 7.1% reduction in off time at another, without a clear dose-response [5].
- 2008A meta-analysis of four Parkinson's and Alzheimer's trials found dose-dependent weight loss, and NeuroSearch moved the compound into obesity [2][16].
- 2008The 24-week TIPO-1 trial reported 9.2% weight loss at the middle dose against 2.0% with diet and placebo, with a 7.4 beat-per-minute rise in heart rate [1].
- 2013The Lancet published an expression of concern about the TIPO-1 report in April, and a July letter by the trial authors followed [12][13].
- 2021FDA granted an orphan designation for a fixed-dose tesofensine-metoprolol combination for hypothalamic obesity on July 21 [27].
- 2022A 24-week trial of the combination in hypothalamic obesity reported 6.3% additional weight loss, and in December the sponsor withdrew two planned phase 2 trials for financial reasons [10][32][37].
- October 2026No finished tesofensine product is listed in FDA's NDC directory [39], no phase 3 trial is registered [36], WADA names it in S6.B and prohibits it in competition [28], and the NCAA list does not name it but its catch-all bans substances chemically or pharmacologically related to the banned classes [29].
How it compares with related peptides
Liraglutide is a GLP-1 receptor agonist, a drug that acts at the receptor for glucagon-like peptide 1 [17]. The 2018 review of centrally acting obesity drugs covers both, and they work on different systems: liraglutide activates a cell-surface GLP-1 receptor, while tesofensine blocks three monoamine transporters [17][1]. Liraglutide belongs to the incretin side of that comparison.
Mazdutide is a dual glucagon and GLP-1 receptor agonist studied in adults with obesity [35]. A 179-participant phase 2 trial reported weight loss of up to 18.1% at 32 weeks against 0.9% with placebo, with gastrointestinal adverse events and discontinuations at the highest dose [35]. Tesofensine is an oral small molecule that blocks monoamine reuptake, and its main 24-week obesity trial reported 9.2% at the middle dose and 10.6% at the top dose [1]. The contrast is useful: an injected dual glucagon and GLP-1 receptor agonist against an oral monoamine drug, with different adverse-event profiles. Mazdutide covers the incretin side.
Side effects and safety signals
The safety picture is dominated by the cardiovascular cost of raising monoamine signaling and by the limits of a small trial base.
- Heart rate rises: 7.4 beats per minute at the middle dose in TIPO-1, and up to 6.8 beats per minute at the highest dose across the Parkinson's and Alzheimer's trials [1][2].
- Blood pressure is less clear. TIPO-1 found no significant rise at the two lower doses [1], while a 2009 review reported a significant rise at the highest dose and dose-dependent heart-rate increases [16].
- Dry mouth, nausea, constipation, hard stools, diarrhea and insomnia were the most common adverse events in TIPO-1 [1]; constipation, insomnia and dry mouth were the most common in the early Parkinson's trial [3].
- Neuropsychiatric events were more frequent than placebo in advanced Parkinson's disease, especially at the higher doses [5].
- In hypothalamic obesity, sleep disturbance occurred in 50% on the combination against 13% on placebo, dry mouth in 43% against 0%, and headache in 36% against 0%; one participant stopped after worsened anxiety [10].
- In type 2 diabetes, 20 of 30 on tesofensine plus metoprolol had an adverse event against 12 of 30 on placebo, and 24-hour mean heart rate was lower on active treatment, 67 against 70 beats per minute [11].
- In Prader-Willi syndrome, three of six adults on the higher dose had a serious adverse event against none of three on placebo, in a trial of 18 participants [33].
- Abuse potential looks low: in 52 recreational stimulant users, tesofensine effects were not different from placebo and lower than d-amphetamine [6].
- The record carries a reporting caveat: the Lancet attached an expression of concern to TIPO-1 in 2013, and a July letter by the trial authors is titled 'Under-reporting of adverse effects of tesofensine' [12][13].
- Purity and identity testing matter for a bulk ingredient. The NDC directory lists tesofensine only as a bulk ingredient, not a finished drug [39], and the COA library collects the tests suppliers publish; how to read a COA explains the common assays.
The future: what's next for Tesofensine
No tesofensine trial is recruiting as of October 2026. ClinicalTrials.gov lists 13 studies: 11 completed and two withdrawn, all phase 1 or phase 2 [36]. The two withdrawn records are the planned phase 2 Tesomet trials in hypothalamic obesity and Prader-Willi syndrome, both stopped for financial reasons before any participant was randomized [32][37]. The 48-week hypothalamic obesity trial has posted extension results, and the phase 1 metoprolol interaction study also has posted results [30][31].
The regulatory path runs through the orphan designation, not through an approval. FDA granted the tesofensine-metoprolol combination an orphan designation for hypothalamic obesity on July 21, 2021, and the record lists it as not approved for that indication [27]. The designation covers the combination rather than tesofensine alone, and no FDA action date appears on the record [27]. An approval would need a new clinical program; the registry shows no active trial after the 2022 withdrawal [32][36].
The science that matters most is still unresolved. The rat work ties appetite suppression to alpha-1 and D1 signaling, but how much each effect contributes in humans is not settled [18][7]. The cardiovascular signal can be offset in the short term with metoprolol, and the phase 1 interaction study shows the principle works [21][31]. Whether that offset holds over years, and whether it protects the heart without undercutting weight loss, is unmeasured.
A useful next trial would compare the combination with an incretin-based weight-loss drug and follow participants for at least a year. The 2026 mazdutide phase 2 trial, which reported weight loss of up to 18.1% at 32 weeks, shows the bar a new obesity drug now has to clear [35]. Its highest 24-week weight loss, 10.6% at the top dose, came in 2008 against diet and placebo [1].
- Whether tesofensine reduces cardiovascular events or diabetes, rather than only body weight, is untested.
- How much of the weight loss comes from lower appetite and how much from higher energy expenditure remains unresolved in humans.
- Whether years of monoamine reuptake blockade cause psychiatric or cardiac harm is unknown, because randomized controlled exposure stops at 24 weeks.
- Whether the metoprolol combination keeps its weight-loss effect while protecting the heart beyond 24 weeks is unproven.
- Whether tesofensine can fill the unmet need in hypothalamic obesity depends on a trial the sponsor withdrew in 2022.
