KDC-MN-230 – Kodiac biolabs

Plain-language summaryIntrigue 38 / 100

Toloxatone (Humoryl) is a French reversible MAO-A inhibitor from Delalande, approved in France in 1984. Like moclobemide and pirlindole it can be displaced from the enzyme by dietary tyramine, which means patients can eat aged cheese without triggering a hypertensive crisis. The drug had a brief moment of relevance in French psychiatry but never spread to other markets, was not pursued for FDA approval, and was eventually discontinued in France in the 2000s as newer antidepressants displaced it. It is mostly of historical interest now, although it remains a useful research probe for MAO-A pharmacology because of its clean mechanism. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundEstablished workhorse

25/100

A 1984 French RIMA overtaken by moclobemide; minimal novelty, thin evidence base, shrinking research relevance

Look, toloxatone is a compound that made sense in 1984. Delalande was doing real chemistry, the RIMA concept was genuinely interesting at the time, and getting a reversible MAO-A inhibitor that didn’t require tyramine restriction was a meaningful step away from the irreversible MAOI era. We get that. But we’re not rating it for 1984.

The mechanism is single-enzyme competitive inhibition of MAO-A. That’s it. There’s no dual target story, no allosteric angle, no novel downstream pathway. MAO-A biology is about as well-mapped as neurochemistry gets at this point, and the RIMA concept was fully articulated and validated long before this compound hit its peak. Moclobemide became the reference RIMA because it has broader international approval, more trial data, and a cleaner pharmacological record. Toloxatone sits behind it on every dimension that matters to a working investigator.

The evidence situation is genuinely thin by current standards. French MDD trials from the 1980s were sufficient for a French approval in a different regulatory climate, but that literature hasn’t grown in any meaningful way. The compound never cleared regulatory review outside France. Clinical use has substantially declined, which is the field voting with its feet. There’s no live clinical program, no recent phase 2 data, nothing in ClinicalTrials.gov worth flagging. What you have is historical evidence that it works roughly as expected for a RIMA, which isn’t the same as having evidence that it does anything moclobemide doesn’t.

The only honest positive we can offer is the bench probe angle. The abstract notes it’s used as a reference oxazolidinone RIMA in mechanism studies, and thats real, if narrow. If you’re specifically studying the oxazolidinone scaffold or doing comparative binding work across RIMA chemotypes, toloxatone gives you a specific structural reference that moclobemide doesn’t. That’s a genuine, if limited, use case. But it doesn’t move the needle much for most programs.

Honestly, the compound reads like a chapter in the history of antidepressant pharmacology rather than an active research target. Investigators working on MAO biology will reach for moclobemide, harmaline derivatives, or clorgyline depending on selectivity needs. There’s no scenario where toloxatone is the first or second choice. The score reflects a real compound with real historical evidence that has been quietly made irrelevant by better alternatives and a mechanism that no longer surprises anyone.

Novelty: 18
Mechanism promise: 22
In-category differentiation: 18
Evidence quality: 32
Translational signal: 38
Research bench value: 28

Rationale Toloxatone scores low across the board because it’s a four-decade-old regional approval with no international uptake, a well-understood single-enzyme mechanism that moclobemide executes better, and an evidence base that never cleared the bar for approval outside France. The oxazolidinone scaffold gives it marginal probe identity but not enough to rescue the score.

Reversible MAO-A inhibitor

A 5-(hydroxymethyl)oxazolidinone RIMA approved in France in 1984; an early-generation reversible inhibitor of MAO-A.

Abstract

Toloxatone (5-(hydroxymethyl)-3-(3-methylphenyl)oxazolidin-2-one; CAS 29218-27-7; molecular formula C11H13NO3; molecular weight 207.23) is an oxazolidinone RIMA developed at Delalande in France and approved there in 1984 under the trade name Humoryl. The compound is a reversible competitive MAO-A inhibitor with a clinical profile broadly comparable to moclobemide; selectivity for MAO-A over MAO-B is approximately 50-fold at therapeutic concentrations. Plasma half-life is approximately 2 hours; hepatic metabolism is the primary clearance pathway. Tyramine restriction is not required at clinical doses. Clinical efficacy in major depressive disorder was demonstrated in French trials but the drug never received approval outside France and clinical use has substantially declined. Used historically and as a reference oxazolidinone RIMA in mechanism studies.

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Tag: KDC-MN-230

Toloxatone

Abstract

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