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Tag: Sulfonamide AMPA potentiator

PEPA

Plain-language summaryIntrigue 32 / 100

PEPA is a sulfonamide AMPA potentiator developed in Japan. Used as a research probe for AMPA receptor pharmacology. 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 Kodiac editorial, not peer-reviewed.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 compoundNiche research probe

42/100

Potent AMPA PAM with sharp in vitro probe value but fatal PK and no translational signal

Look, PEPA occupies a very specific niche in the AMPA receptor pharmacology toolkit, and understanding that niche is the whole story. The compound’s core value is as a high-potency positive allosteric modulator of AMPA-type glutamate receptors, and its sulfonamide scaffold gives it a mechanistic fingerprint distinct from the benzamide ampakines like CX-614 or the aniracetam derivatives that most investigators reach for first. AMPA receptor potentiation is genuinely interesting biology. Positive allosteric modulation slows receptor desensitization and deactivation, amplifies AMPA-mediated currents, and downstream recruits BDNF signaling cascades implicated in LTP and synaptic consolidation. That’s a real mechanism with real relevance to cognitive neuroscience.

Here’s the thing though: PEPA’s potency advantage over marketed ampakines is real in vitro and essentially academic in vivo. The compound has poor oral bioavailability and a short plasma half-life that have kept it firmly in the cell culture and slice prep world. Investigators trying to use it for in vivo behavioral work face serious delivery challenges that newer AMPA PAMs in the research literature dont have. That PK profile isn’t a minor inconvenience, it’s a structural limitation that caps how much you can ask of this compound as a research tool.

What we like: the potency-per-molecule is legitimately high, and for receptor binding studies, selectivity profiling, and electrophysiology in brain slices, PEPA gives you sharp, clean AMPA potentiation that’s useful for dissecting receptor subtype contributions. The sulfonamide scaffold also offers SAR diversity that benzamide-class AMPA PAMs dont, which gives it genuine value for chemists doing scaffold comparisons or exploring allosteric site geometry. For a program centered squarely on AMPA receptor biology, this compound earns a spot on the shelf.

What we dont like: availability is a real constraint. PEPA hasn’t crossed into research-chemical-grade commercial supply in any meaningful way, which means sourcing is limited to academic supply chains and adds friction to any program trying to use it at scale. And without human data of any kind, its translational story is essentially zero. The broader ampakine class has had a rough decade in Phase 2 trials, and PEPA’s poor PK means it was never even a candidate to generate the kind of clinical signal that would make it more interesting from an investment standpoint.

Honestly, this is a probe compound doing exactly what probe compounds are supposed to do: give you mechanistic resolution in controlled in vitro settings. For AMPA receptor pharmacologists specifically, its genuinely useful. For anyone outside that niche, theres little reason to engage with it over compounds that offer better translational geometry. A score of 42 reflects that accurately. High bench value in a narrow context, with almost nothing pointing toward broader relevance.

Novelty

38

Mechanism promise

58

In-category differentiation

42

Evidence quality

38

Translational signal

18

Research bench value

60

Rationale PEPA’s primary scoring axis is bench value as a high-potency sulfonamide AMPA PAM with a distinct mechanistic fingerprint from the benzamide ampakines, but poor oral bioavailability and a short plasma half-life confine it to cell culture and slice prep applications, producing essentially zero translational signal and dragging the overall down to niche-probe territory; novelty is modest because AMPA PAMs as a class date to the 1990s.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Sulfonamide AMPA potentiator

A potent benzothiazide AMPA potentiator used principally as a research probe for AMPA receptor pharmacology.

Abstract

PEPA (4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide; CAS 158235-23-7) is a potent sulfonamide-class AMPA receptor positive allosteric modulator developed as a research tool compound. The compound shows substantially greater AMPA potentiation per molecule than the marketed and Phase 2 ampakines, but with poor pharmacokinetic properties (low oral bioavailability, short plasma half-life) that limit clinical translation. PEPA is used principally as a research probe for AMPA receptor pharmacology in vitro and ex vivo. The compound has not been advanced to human clinical trials and has no significant research-chemical-grade availability outside academic research supply chains.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

KDC-MN-059Open in new tab →

Download PDF →

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.

May 9, 2026
Org-26576

Plain-language summaryIntrigue 40 / 100

Org-26576 is a sulfonamide AMPA potentiator developed at Organon. Phase 2 trials investigated it in major depressive disorder and ADHD. 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 compoundNiche research probe

39/100

Discontinued Merck ampakine with modest Phase 2 signal and limited bench accessibility

AMPA receptor positive allosteric modulators have a genuinely compelling theoretical basis. By slowing channel deactivation and desensitization, they amplify glutamatergic throughput, drive BDNF expression, and modulate synaptic plasticity in ways that NMDA-targeted compounds simply can’t replicate. The mechanism is interesting, the rationale for depression and cognitive enhancement is plausible, and Org-26576 at least made it further through clinical development than most ampakines. Organon built the program, Schering-Plough inherited it, Merck finished it, and then walked away. That arc matters.

Here’s the thing about the AMPA PAM class: it has a long, frustrating history of preclinical promise colliding with clinical disappointment. CX516, CX717, farampator, LY404187 and a dozen others all generated real excitement in the late 1990s through mid-2000s, showed plausible Phase 1 tolerability, and then produced Phase 2 data described in almost identical language to whats in Org-26576’s dossier: modest cognitive endpoint improvements, no adverse signal. In pharmaceutical development that’s a polite way of saying the delta wasn’t there. When a well-resourced pharma group has already invested in full IND-enabling studies and a Phase 2 execution and still walks away, the independent research community is left with a thin published evidence base and whatever can be reconstructed from conference abstracts.

The sulfonamide scaffold is a genuine chemical differentiator. Org-26576 is not just a CX-class analog; the sulfone headgroup changes the binding geometry and potentially the kinetic profile of AMPA channel modulation in ways that aren’t fully worked out in the public literature. For a group specifically investigating structure-activity relationships across AMPA PAM chemotypes, or trying to understand whether kinetic selectivity differences between ampakine classes have functional consequences, this compound represents a well-defined clinical-stage data point. It cleared human safety. That’s real. It’s also about the extent of the positive case.

Sourcing is a serious obstacle. The compound is rarely available in research-chemical-grade markets, which means bench accessibility is low and reproducibility across labs is essentially hypothetical. Researchers who want an AMPA PAM probe with documented methodology would typically reach for farampator, which has more published protocol support, or look at the newer BNT-III class compounds generating current literature. We think the under-characterized sulfonamide angle is the only genuine hook here, and it’s a narrow one.

Honestly, this scores where it does because the class is mature, the clinical outcome was modest, the compound is hard to source, and the evidence base is largely gated behind Merck’s development files. Interesting chemistry in an underdelivering class isnt the same as a compelling research target.

Novelty

38

Mechanism promise

57

In-category differentiation

30

Evidence quality

40

Translational signal

35

Research bench value

28

Rationale Org-26576 earns modest scores across the board: the sulfonamide AMPA PAM scaffold has chemical interest but the class has a consistent history of clinical underdelivery, and Merck’s discontinuation leaves the evidence base thin and sourcing nearly nonexistent for independent labs. Mechanism score is the brightest spot; differentiation and bench value are both dragged down by limited availability and a crowded class where better-characterized probes already exist.

Editorial commentary from Kodiac biolabs. Not a recommendation, not clinical advice. Research use only.

Sulfonamide AMPA potentiator

An Organon/Merck ampakine that reached Phase 2 in major depressive disorder.

Abstract

Org-26576 is a sulfonamide-class AMPA receptor positive allosteric modulator developed by Organon (subsequently Schering-Plough, Merck) for cognitive enhancement in major depressive disorder and other indications. The compound advanced through Phase 2 trials with results consistent with the ampakine class profile (modest cognitive endpoint improvements, no adverse signal). The development program was discontinued under Merck. Pharmacokinetics: plasma half-life approximately 5 hours; oral bioavailability adequate. The compound is rarely available in research-chemical-grade markets.

Read the full monograph

The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

KDC-MN-060Open in new tab →

Download PDF →

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.

May 9, 2026

Bench-grade research compounds. Cited research. Verified COAs.

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