Tesofensine

What it is

Tesofensine inhibits reuptake of noradrenaline, dopamine and serotonin. It was developed for Parkinson's disease and Alzheimer's, performed poorly on those endpoints, and produced weight loss in trial participants substantial enough to redirect the entire programme.

The mechanism is central appetite suppression, not anything happening in fat tissue. It is a stimulant-adjacent drug in everything but name.

What the evidence shows

Phase 2 results were genuinely striking for their era. Over 24 weeks, tesofensine 0.5 mg produced roughly double the weight loss of the best drugs available at the time, in the region of 10% of body weight including the diet-and-placebo effect.

For 2008 that was remarkable. It is worth putting alongside what came later: semaglutide reached about 15% in STEP-1 and tirzepatide about 21% in SURMOUNT-1, without a monoamine mechanism.

Why it never arrived

Blood pressure and heart rate.

Triple monoamine reuptake inhibition raises sympathetic tone, and that shows up as measurable cardiovascular effects at the doses that produce weight loss. This is precisely the wrong side effect for a drug intended for long-term use in a population already at elevated cardiovascular risk.

The history of anti-obesity drugs is largely a history of this exact problem. Sibutramine was withdrawn after a cardiovascular outcomes trial found excess events. Fenfluramine was withdrawn over valvular disease. Regulators approach centrally acting appetite suppressants with a scepticism that is entirely earned, and tesofensine did not overcome it.

Practical notes

• The nine day half-life is the thing people underestimate. Levels keep climbing for weeks after starting. Someone who feels fine on day three is not yet at steady state, and side effects that appear at week four can take a month to clear after stopping.
• The drug interaction risk is real. Combining a triple reuptake inhibitor with an SSRI, an MAO inhibitor or another stimulant is a serotonin toxicity risk, and this is a compound people buy without telling anyone.
• The incretins made the trade obsolete. Accepting stimulant side effects for 10% weight loss was a defensible bargain when nothing better existed. It is a much harder case to make now.

Side effects and warning signs

Commonly reported

• Dry mouth, the most common complaint by a wide margin
• Insomnia
• Nausea
• Constipation
• Raised heart rate and blood pressure, which is the dose-limiting problem
• Agitation, irritability and mood changes

Stop and get medical help

• Sustained rise in blood pressure or resting heart rate, which is the reason this class keeps failing at the regulatory stage
• New or worsening depression, anxiety or agitation
• Any use alongside an MAO inhibitor or another serotonergic drug, given the risk of serotonin toxicity
• Palpitations or chest discomfort

Sources

1. Tesofensine, a monoamine reuptake inhibitor for the treatment of obesityreview
2. Tesofensine, a triple monoamine re-uptake inhibitor: dopamine transporter occupancy measured by PETtrial

From the community

Discussion for this compound concentrates in r/Biohackers.

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