RESEARCH MONOGRAPH · KDC-MN-231

Sembragiline

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

51/100

Investigational reversible MAO-B inhibitor with a clean profile and an Alzheimer's trial that didnt deliver

Sembragiline is a selective reversible MAO-B inhibitor that Roche pushed into Alzheimer's disease trials in the 2010s with the hypothesis that elevating brain dopamine through MAO-B inhibition might slow cognitive decline. The mechanism story is reasonable. MAO-B activity increases with age, particularly in astrocytes, and contributes to oxidative stress through H2O2 generation alongside its monoamine-catabolism role. So a clean reversible MAO-B inhibitor without the propargylamine confounds had a plausible neuroprotective rationale.

The MAYFLOWER ROAD phase 2 study didn't hit. The signal on the primary cognitive endpoint was essentially flat, with some subgroup hints that didnt hold up under reasonable scrutiny. Roche didn't push the program forward and sembragiline has been quiet since, which is the typical fate of investigational compounds that fail a well-powered registration-pathway trial.

What we find interesting is the pharmacology was actually clean by all accounts. Selective, reversible, no amphetamine metabolites, dose-response well characterized in the early studies. So the failure was about the hypothesis being wrong (or at least insufficient) rather than the compound being a bad probe. Thats a useful kind of failure to learn from, because it tells you something about whether MAO-B inhibition alone can shift Alzheimer's pathology, and the answer at least in this trial was no.

For research, sembragiline remains a potentially useful tool compound for selective reversible MAO-B work, particularly when you want to avoid the propargylamine confounds that rasagiline and selegiline carry. The challenge is sourcing. As an investigational compound that didn't reach approval, reference material is harder to find than for the established MAO-B inhibitors and per-gram costs can be steep.

What we dont like is the literature density. There's the Roche development data, the Alzheimer's trial, and not much else. Pharmacology characterization beyond what got published for the registration program is thin. If you need additional context for an experiment, you'll be filling in the gaps yourself.

Sourcing varies a lot. HPLC validation is fine on clean material but vendor quality is inconsistent.

Mostly a historical investigational compound at this point. Interesting if you specifically need a clean reversible MAO-B probe, otherwise pick rasagiline.

Evidence: 50
Mechanism: 75
Reliability: 55
Safety: 70
Sourcing: 45
Value: 40
Signal: 35
Staying power: 38

Plain-language summary Intrigue 40 / 100

Sembragiline is an investigational selective reversible MAO-B inhibitor from Roche and EVOTEC, originally developed as a possible Alzheimer disease treatment. The rationale was elegant: MAO-B is upregulated in the reactive astrocytes that surround amyloid plaques in Alzheimer brain tissue, and that upregulation contributes to oxidative damage. Selectively shutting it down with a reversible blocker should, in theory, reduce that damage without interfering with normal brain function. The Phase 2 MAyflOwer RoAD trial in mild-to-moderate Alzheimer disease failed to show clinical benefit, however, and development was halted. The compound retains research value as a mechanistic probe but has no clinical future. 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.

Selective reversible MAO-B inhibitor (investigational)

A selective reversible MAO-B inhibitor investigated for Alzheimer disease; failed phase 2 efficacy.

Abstract

Sembragiline (EVT-302, RG1577; molecular formula C19H22FN3O; molecular weight 327.40) is a selective reversible MAO-B inhibitor developed at Roche and EVOTEC as a candidate for Alzheimer disease. The mechanistic rationale: MAO-B is upregulated in reactive astrocytes in Alzheimer brain tissue, contributing to oxidative stress and amyloid pathology; selective reversible inhibition might reduce this contribution without the irreversible enzyme abolition of selegiline or rasagiline. Phase 2 MAyflOwer RoAD trial in mild-to-moderate Alzheimer disease (n=542) failed to show significant slowing of cognitive decline at 52 weeks; development was halted. The compound retains research utility as a clean tool for selective reversible MAO-B inhibition (selectivity ratio greater than 1000:1 over MAO-A) and is used in academic studies of MAO-B's role in neurodegeneration. Used as the reference reversible selective MAO-B inhibitor in academic neuroscience.

Mechanism of action

Selective reversible MAO-B inhibition (greater than 1000:1 selectivity over MAO-A). Distinct from selegiline and rasagiline by reversibility.

Reported research dose ranges

Reported research dose ranges in the literature.

References

Nave S, et al. Sembragiline in moderate Alzheimer's disease: results of the MAyflOwer RoAD trial. J Alzheimers Dis 2017.
Borroni E, et al. Sembragiline: a novel, selective, reversible MAO-B inhibitor. J Pharmacol Exp Ther 2017.

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KDC-MN-231

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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Sembragiline

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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