RESEARCH MONOGRAPH · KDC-MN-058

Farampator (CX-691)

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

Our opinion on this compound

62/100

Methylsulfonamide ampakine with the cleanest human cognitive signal in the class, then quietly shelved

Farampator (CX-691, also called Org-24448) is honestly the ampakine that should have made it further than it did. Organon licensed it from Cortex in the early 2000s, ran a phase 2 in age-associated memory impairment, and got the cleanest cognitive signal of any AMPA-PAM in human trials. The Wezenberg paper from 2007 is the strongest piece of the evidence base, showing improvements in episodic memory tasks in healthy older volunteers that were both statistically significant and clinically meaningful.

The pharmacology is the standard benzoxazine-style AMPA potentiation but with a methylsulfonamide that improves pharmacokinetics. Reasonable BBB penetration, sustained effect, decent oral bioavailability. The mechanism work mostly mirrors the broader CX-series story.

What's interesting is what happened next. Organon got acquired by Schering-Plough, then Schering-Plough got acquired by Merck, and the farampator program got buried in the consolidation. The drug was apparently dropped not because of efficacy or safety issues but because it didnt fit the new portfolio strategy. So we have a compound with positive phase 2 cognitive data that just stopped being developed.

What we like: the strongest human cognitive signal in the ampakine class, real safety data from completed clinical trials, well-characterized pharmacokinetics, and a development history that suggests the molecule deserved more attention than it got.

What we dont like: the development halt means we'll probably never know what the longer-term safety profile looks like, the published trial data is limited (only one well-conducted study in older volunteers reached publication), and reference material is harder to source than for the more famous CX compounds.

Sourcing is more limited than other ampakines because commercial interest dropped after the program ended. A few specialty suppliers produce it, characterization varies, and HPLC verification is essentially required. The methylsulfonamide group is stable enough but the synthesis isnt trivial.

For research, farampator is probably the most clinically-relevant ampakine you can work with, and the published age-associated memory impairment work makes it the obvious choice for cognitive aging models. Genuinely underutilized molecule given how much actual human data exists.

One of the more interesting orphaned compounds in the CNS literature.

Evidence: 60
Mechanism: 75
Reliability: 70
Safety: 65
Sourcing: 50
Value: 55
Signal: 65
Staying power: 55

Plain-language summary Intrigue 42 / 100

Farampator (CX-691) is a methylsulfonamide AMPA potentiator. Phase 2 trials in cognitive impairment and depression showed modest signals. 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.

Methylsulfonamide AMPA potentiator

An Organon/Schering-Plough ampakine (CX-691) that reached Phase 2 in major depressive disorder and Alzheimer disease.

Abstract

Farampator (CX-691, ORG-24448; CAS 211735-76-1; molecular formula C16H22N2O3S; molecular weight 322.42) is a methylsulfonamide-class AMPA receptor positive allosteric modulator developed by Cortex Pharmaceuticals and licensed to Organon (subsequently Schering-Plough, then Merck). The compound advanced through Phase 2 trials in major depressive disorder, Alzheimer disease, and adult ADHD with mixed results; the development program was discontinued after the Schering-Plough acquisition by Merck. Mechanism is AMPA receptor positive allosteric modulation with characteristics intermediate between the early CX-516 class and the later sustained-action ampakines. Pharmacokinetics: plasma half-life approximately 5 to 6 hours; oral bioavailability adequate. The compound is sold as a research chemical with limited availability. The clinical evidence base in depression specifically is interesting: rapid antidepressant-like effects analogous to those seen with ketamine were observed in Phase 2, suggesting the ampakine mechanism may share some clinical pharmacology with NMDA-blocking rapid antidepressants.

Mechanism of action

AMPA receptor positive allosteric modulator (methylsulfonamide class).

Reported research dose ranges

Reported research dose ranges in the trial literature span 100 to 1000 mg.

References

Wezenberg E, et al. Acute effects of the ampakine farampator on memory and information processing in healthy elderly volunteers. Neuropsychopharmacology 2007.
Goff DC, et al. A placebo-controlled add-on trial of the ampakine, CX516, for cognitive deficits in schizophrenia. Neuropsychopharmacology 2008.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, reported research dose ranges, sourcing and quality verification, reconstitution and handling, stack interaction considerations, and a curated reference list. Available as a research-use-only PDF download.

KDC-MN-058

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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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Kodiac sells research compounds for investigative use only.

Farampator (CX-691)

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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