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Author: kodiac

Navacaprant

Our opinion on this compoundNovel, promising

63/100

Cleanest KOR antagonist in clinical testing, real anhedonia signal, but Phase 3 null is hard to explain away

Look, the kappa opioid receptor story for depression is genuinely interesting biology, and navacaprant is the cleanest version of the hypothesis we’ve seen in a clinical setting. The KOR system is deeply wired into stress circuits, anhedonia, and dysphoria. Blocking it isn’t just another monoamine trick; it’s targeting a specific neurobiological substrate that standard antidepressants don’t touch. That mechanistic angle is real, and the compound’s selectivity profile makes it the best available probe for it.

The pharmacology is unusually clean. 1.2 nM potency at KOR in native VTA dopamine neurons, 300-fold selectivity over mu, 340-fold over delta, no detectable agonist activity at any opioid subtype in vitro. The problems that killed JDTic (c-JNK activation, cardiac toxicity in humans), made nor-BNI impractical (weeks-long receptor occupancy), and muddied aticaprant’s mechanism (partial mu/delta activity in native tissue electrophysiology) simply don’t apply here. The PET occupancy work is also genuinely useful: a single 160 mg dose achieving roughly 90 percent KOR occupancy, with the 80 mg clinical dose projected to maintain that at steady state. That kind of pharmacokinetic-pharmacodynamic clarity is exactly what you want in a research probe.

Here’s the thing though. The clinical picture is complicated. The Phase 2a data from Mathew et al. 2025 has a real signal buried in it: in the moderate-to-severe MDD subgroup, response rates were 45.5 percent versus 24.1 percent for placebo, and an NNT of 5 for response is genuinely meaningful. Anhedonia-specific improvements on the SHAPS are mechanistically consistent with what you’d predict from KOR blockade. But the primary endpoint failed. And then KOASTAL-1 failed badly: both arms reported identical 12.5-point MADRS reductions, p equals 0.993. Thats not a near-miss, that’s a null, and a large-N null at that.

We think the compound is probably doing something real in a specific subpopulation, and the failure mode is patient selection rather than mechanism failure. The exploratory differential response in female participants in KOASTAL-1 and the protocol modifications for KOASTAL-2 and KOASTAL-3 suggest Neumora’s team agrees. Whether that stratification story holds up in 2026 matters enormously for any translational read. For now, the human evidence is inconsistent enough that we score it conservatively.

What we still like: navacaprant is the only available selective reversible KOR antagonist with Phase 3-grade pharmacokinetic characterization and confirmed brain penetrance in humans. For anyone studying stress-induced anhedonia models, dynorphin signaling, or KOR circuit biology in affective states, this is the probe you’d reach for over any alternative. The tolerability profile is also a research asset: no weight gain, no sexual dysfunction, fewer treatment-emergent adverse events than placebo in Phase 2. That matters for study design and for modeling the KOR system without the confounds that follow legacy compounds in this class.

Novelty

68

Mechanism promise

68

In-category differentiation

72

Evidence quality

56

Translational signal

44

Research bench value

68

Rationale Navacaprant represents best-in-class pharmacology within the KOR antagonist class, with a mechanistically coherent anhedonia signal in Phase 2 and genuine probe utility for stress-circuit biology, but the KOASTAL-1 null (p=0.993, identical 12.5-point reductions in both arms) meaningfully depresses translational scores and prevents placement in the novel-frontier tier.

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

Selective, reversible kappa opioid receptor antagonist with no agonist activity at kappa, mu, or delta opioid receptors

A fluorinated quinoline-oxadiazole kappa opioid receptor antagonist discovered at Scripps Research and advanced through Phase 3 clinical trials for major depressive disorder, distinguished from earlier KOR antagonists by full receptor antagonism without mu or delta cross-reactivity, rapid reversibility, and a favorable tolerability profile in controlled clinical studies.

Abstract

Navacaprant (BTRX-335140, NMRA-140, CYM-53093) is a potent, highly selective, and reversible antagonist of the kappa opioid receptor (KOR) under clinical development for the treatment of major depressive disorder (MDD). The compound was discovered in collaboration between Scripps Research faculty members Hugh Rosen and Edward Roberts and was advanced through clinical development first by BlackThorn Therapeutics and subsequently by Neumora Therapeutics. Navacaprant blocks the KOR with an IC50 of 1.2 nanomolar in native ventral tegmental area dopamine neurons and 29 nanomolar in recombinant CHO-K1 cells, with approximately 300-fold selectivity over the mu opioid receptor and greater than 340-fold selectivity over the delta opioid receptor. The compound exhibits no detectable agonist activity at any opioid receptor subtype in vitro (EC50 greater than 10 micromolar) and no opioid agonist effects in vivo, including no alteration of extracellular dopamine in the nucleus accumbens at oral doses up to 100 mg/kg in rats. The pharmacological profile differentiates navacaprant from earlier KOR antagonists: unlike JDTic (which activates c-Jun N-terminal kinase and produced cardiac toxicity in humans), nor-binaltorphimine (which has an impractically long duration of action), and aticaprant (which partially blocks mu and delta opioid receptor responses in native tissue electrophysiology), navacaprant combines full KOR antagonism with rapid reversibility, clean selectivity, and no off-target opioid effects. In a Phase 1 program in healthy volunteers, navacaprant demonstrated favorable pharmacokinetics across single oral doses of 5 to 240 mg and multiple daily doses of 20 to 160 mg for 10 days, with good tolerability and no serious adverse events. A positron emission tomography receptor occupancy study confirmed brain KOR engagement, with a single 160 mg dose producing approximately 90 percent occupancy and pharmacokinetic-pharmacodynamic modeling projecting approximately 90 percent occupancy at steady state with 80 mg once daily. In a Phase 2a randomized, double-blind, placebo-controlled trial in 204 adults with MDD (Mathew et al. 2025), navacaprant 80 mg once daily for 8 weeks did not meet the primary endpoint in the full efficacy population (Hamilton Depression Rating Scale least-squares mean difference versus placebo of negative 1.7 points, p equals 0.121), but demonstrated statistically significant improvements in the moderate-to-severe MDD subgroup on both depressive symptoms and anhedonia as measured by the Snaith-Hamilton Pleasure Scale, with response rates of 45.5 percent versus 24.1 percent for placebo (number needed to treat equals 5) and remission rates of 26.1 percent versus 10.8 percent (number needed to treat equals 7). Fewer treatment-emergent adverse events occurred in the navacaprant group than in the placebo group, and no serious adverse events, weight gain, or sexual dysfunction were reported with navacaprant. In Phase 3, the KOASTAL-1 trial (n equals 383) failed to demonstrate separation from placebo on the Montgomery-Asberg Depression Rating Scale primary endpoint, with both treatment arms reporting identical 12.5-point reductions (p equals 0.993); exploratory subgroup analyses suggested a differential response in female participants. The KOASTAL-2 and KOASTAL-3 Phase 3 trials were paused for protocol modifications and are expected to report data in 2026. This monograph reviews the chemistry and structural pharmacology of navacaprant; the molecular pharmacology including receptor binding, selectivity, and electrophysiological characterization; the available pharmacokinetic data; the preclinical pharmacology in stress and cognitive models; the clinical evidence base including the Phase 2 and Phase 3 programs; sourcing and quality verification; handling considerations; stack interactions; adverse events; and a comparative assessment of five kappa opioid receptor candidates (aticaprant, buprenorphine-samidorphan, JDTic, nor-binaltorphimine, and PF-04455242) against navacaprant. The compound is investigational and is not approved by any regulatory authority. It is available as a research-grade preparation; investigators should obtain analytical confirmation of identity and purity on every lot.

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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.

May 22, 2026
CMS121

Our opinion on this compoundNovel, promising

60/100

Salk-derived FASN inhibitor with Phase 1 PK data and coherent multi-model neuroprotective preclinical signal

CMS121 came out of a serious medicinal chemistry campaign: over 160 synthetic fisetin derivatives screened at the Salk Institute for Biological Studies, not for receptor binding but for functional neuroprotection in HT22 hippocampal cells under glutamate and iodoacetic acid toxicity. That’s phenotypic screening done properly. The compound that emerged had nanomolar protective activity, oral bioavailability, and anti-inflammatory activity the parent flavonoid lacked. It was then dosed in mice for years before anyone went looking for the target. The Ates et al. 2020 Redox Biology paper identifying fatty acid synthase as the molecular anchor is a real mechanistic result, not a mechanism-by-assertion story you see too often in this space.

What we like is the mechanistic coherence downstream of FASN. Inhibit the enzyme, reduce polyunsaturated fatty acid availability, cut the ferroptotic lipid peroxidation signal, lower 4-HNE adducts, suppress iNOS and COX-2 in microglia. That’s a clean causal chain to an increasingly important cell death pathway in neurodegeneration. But the Currais et al. eLife 2019 paper adds a layer most anti-ferroptotic compounds can’t claim: elevated acetyl-CoA feeds histone H3K9 acetylation in SAMP8 mice, and that epigenetic angle tracks with preserved cognition. Connecting lipid metabolism to chromatin state in the aging brain is not a well-trodden route, and honestly thats what makes CMS121 interesting as a research tool beyond its therapeutic ambitions.

The preclinical width is real. APPswe/PS1deltaE9 AD mice, SAMP8 accelerated aging, R6/2 and YAC128 Huntington’s models, db/db metabolic mice. Cross-indication breadth like that either means the mechanism is genuinely fundamental to age-associated cell stress or the lab is skilled at finding what it’s looking for. The HD lifespan extension data, up to 17 percent in R6/2, is hard to dismiss. What it isn’t is independently replicated. Almost all of this literature traces back to the Maher and Schubert group at Salk. Thats one consortium, and the calibration anchors say that matters.

The Phase 1 (NCT05318040, 88 healthy volunteers, single ascending doses to 1800 mg, multiple ascending doses to 900 mg/day for seven days) moved things forward in a specific way. CMS121 reaches systemic circulation in humans, tolerability was generally acceptable, PK was dose-proportional or slightly supraproportional, and the CMS121-C2 metabolite dominates circulating exposure, which has implications for what’s actually doing the work in vivo. Elderly subjects showed higher exposure and longer half-life than young adults. That’s a lot to know at Phase 1. What it is not is efficacy data. Zero human cognitive or biomarker signal has been reported.

For bench investigators, the probe case is specific: if you want to study ferroptosis in neural or aging contexts with a drug-like, orally bioavailable FASN inhibitor, CMS121 fills a niche that ferrostatin-1 can’t because of its PK and that denifanstat (TVB-2640) wasn’t designed for given its oncology orientation. The FASN/acetyl-CoA/histone axis tool value is genuine. We think this is worth following, particularly if Phase 2 efficacy trials move forward. Right now it’s a well-built compound with an interesting story and one lab telling it.

Novelty

72

Mechanism promise

75

In-category differentiation

62

Evidence quality

42

Translational signal

38

Research bench value

65

Rationale CMS121 earns its score on genuine mechanistic novelty: FASN inhibition driving ferroptosis suppression and histone H3K9 acetylation is an unusual and internally coherent story, and the Phase 1 completion elevates it above pure single-lab status. The ceiling is the Salk/Maher group’s near-monopoly on the literature and the complete absence of human efficacy data.

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

Geroneuroprotective small molecule; synthetic fisetin derivative; fatty acid synthase inhibitor with anti-ferroptotic and anti-inflammatory activity

A synthetic quinoline derivative of the flavonoid fisetin, developed at the Salk Institute through phenotypic screening against age-associated neuronal cell death, that inhibits fatty acid synthase and acetyl-CoA carboxylase 1 to protect against ferroptotic lipid peroxidation and cognitive decline in transgenic Alzheimer’s disease and accelerated aging mouse models, with Phase 1 human pharmacokinetic data completed in 2022.

Abstract

CMS121 (CAS 1353224-53-9) is a synthetic quinoline derivative of the dietary flavonoid fisetin (3,7,3′,4′-tetrahydroxyflavone), identified through a phenotypic screening cascade at the Salk Institute for Biological Studies as a potent inhibitor of oxytotic/ferroptotic neuronal cell death with nanomolar protective activity in glutamate toxicity and iodoacetic acid toxicity assays in the HT22 hippocampal cell line. The compound was selected from more than 160 synthetic fisetin derivatives prepared by Chiruta, Schubert, Dargusch, and Maher (Journal of Medicinal Chemistry, 2012) through a multitiered screening approach that evaluated neuroprotective potency, anti-inflammatory activity, and oral pharmacokinetic suitability. The molecular target of CMS121 was subsequently identified as fatty acid synthase (FASN), with dose-dependent enzymatic inhibition demonstrated in cell lysate assays (Ates, Goldberg, Currais, and Maher, Redox Biology, 2020). Downstream of FASN inhibition, CMS121 engages the AMP-activated protein kinase/acetyl-CoA carboxylase 1 (AMPK/ACC1) axis, elevating intracellular acetyl-CoA levels and promoting histone H3 lysine 9 acetylation, a modification linked to memory enhancement in the senescence-accelerated mouse prone 8 (SAMP8) model (Currais et al., eLife, 2019). The anti-ferroptotic mechanism operates through reduction of polyunsaturated fatty acid substrates available for lipid peroxidation, thereby decreasing 4-hydroxynonenal protein adduct accumulation and suppressing downstream neuroinflammatory cascades including inducible nitric oxide synthase, cyclooxygenase-2, and tumor necrosis factor-alpha expression in activated microglia. Preclinical efficacy has been demonstrated across multiple disease models: in APPswe/PS1deltaE9 double transgenic Alzheimer’s disease mice, dietary CMS121 at 400 parts per million (approximately 34 mg/kg/day) for three months beginning at nine months of age normalized spatial memory, contextual fear conditioning, and hippocampal lipid peroxidation markers to wild-type levels; in SAMP8 accelerated aging mice, four months of treatment preserved cognition and reduced transcriptional markers of brain aging; in R6/2 and YAC128 Huntington’s disease models, CMS121 slowed motor dysfunction and extended median lifespan by up to 17 percent; and in db/db leptin receptor deficient mice and wild-type C57BL/6 mice, the compound ameliorated metabolic dysfunction, reduced adiposity, and improved hepatic and renal biomarkers. The compound was advanced to a first-in-human Phase 1 clinical trial (NCT05318040) by Virogenics, Inc. in collaboration with the National Institute on Aging, conducted at Celerion (Lincoln, Nebraska) in 2022. Single ascending doses up to 1800 mg and multiple ascending doses up to 900 mg per day for seven days were generally well tolerated in approximately 88 healthy volunteers, with the majority of treatment-emergent adverse events mild in severity. Pharmacokinetics were dose-proportional or slightly greater than dose-proportional; the CMS121-C2 metabolite was the predominant circulating species; urinary excretion was minimal; systemic exposure was approximately 50 percent higher in the fed state; and elderly subjects exhibited higher exposures and longer terminal elimination half-lives than young adults (Maher, Christopher, Evans, and Raschke, medRxiv, 2025, preprint). This monograph reviews the chemistry and structural relationship to fisetin; the FASN/ACC1/AMPK molecular pharmacology; the preclinical evidence base across Alzheimer’s disease, Huntington’s disease, aging, and metabolic models; the Phase 1 human pharmacokinetic and safety data; sourcing and handling considerations for research applications; and a comparative assessment of five related compounds (fisetin, J147, CAD031, denifanstat, and ferrostatin-1) against CMS121 on five competency standards. The compound has not received regulatory approval for any therapeutic indication. It is positioned as a research-grade geroneuroprotector for investigational use.

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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.

May 22, 2026
ANAVEX 3-71

Our opinion on this compoundNovel, promising

63/100

Dual allosteric M1/sigma-1 agonist with compelling washout data and clean human PK but thin clinical efficacy read

Look, the mechanistic story here is genuinely interesting, and thats rare in the cholinergic space. For decades the approach to muscarinic pharmacology in Alzheimer’s disease was orthosteric agonism, which meant you paid the price in M2/M3/M4/M5 side effects every time you got meaningful M1 engagement. ANAVEX 3-71 approaches this differently: allosteric binding at sub-nanomolar concentrations (approximately 0.05 nM at M1), which gives you receptor-state bias without dragging the full muscarinic family into the response. The addition of sigma-1 agonism at nanomolar potency is not decorative. Sigma-1 receptors sit at mitochondria-associated membranes and regulate proteostasis, calcium signaling, and neuroinflammation in ways that directly complement the cholinergic deficit hypothesis in AD. When Fisher’s group at IIBR screened 83 GPCRs, ion channels, and transporters at 10 micromolar and came back clean across the board, that’s a compound worth paying attention to.

The preclinical data is the strongest argument in the file. Three studies across two distinct transgenic models, the 3xTg-AD mouse and the McGill-R-Thy1-APP rat, report convergent findings: cognitive rescue, amyloid reduction, tau phosphorylation correction at multiple epitopes, neuroinflammation attenuation, and BDNF pathway normalization. What we find most compelling is the washout persistence. Hall et al. (2018) and Orciani et al. (2023) both report that effects endure through treatment interruption periods of four to five weeks. Symptomatic compounds don’t behave like that. The McGill group’s involvement in the rat studies adds meaningful cross-lab weight, but Fisher’s lab still has its fingerprints on most of the preclinical pharmacology and the single-consortium concern is not fully resolved. The preclinical base is solid for this stage of development; it is not independently replicated at a level that would move this into established-active territory.

Clinically, we’re early. The Phase 1 SAD study (NCT04442945, 36 subjects) returned clean dose-proportional pharmacokinetics with a 3.56-hour half-life for the parent compound and no QTc signal across the full dose range. That’s the right foundation. The Phase 2 in schizophrenia (NCT06245213, 71 subjects) showed dose-dependent improvements in EEG biomarkers with favorable tolerability and no serious adverse events. That’s encouraging, but EEG endpoints are not efficacy endpoints, and there is no completed Phase 2 efficacy read in Alzheimer’s disease or any other indication yet. The clinical story is promising and clean, not yet compelling by itself.

For bench investigators, ANAVEX 3-71 is a high-value probe. The clean off-target profile and exceptional M1 allosteric potency make it a useful tool for dissecting M1 allosteric pharmacology from orthosteric mechanisms, and for studying sigma-1 biology in a neurodegeneration context where both receptors are implicated. We think the compound earns its place in the library on the strength of the mechanistic differentiation and the preclinical washout data. The score reflects real promise held back by an evidence base that is still, for now, mostly one lab and one Phase 2 biomarker signal.

Novelty

70

Mechanism promise

78

In-category differentiation

68

Evidence quality

45

Translational signal

45

Research bench value

65

Rationale Sub-nanomolar allosteric M1 potency combined with sigma-1 dual mechanism is genuinely differentiated from orthosteric cholinergic approaches, and convergent two-model preclinical washout data makes a credible disease-modification case; scored down by Fisher-group concentration in the preclinical literature and absence of any completed Phase 2 efficacy readout in any indication.

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

Dual allosteric M1 muscarinic acetylcholine receptor agonist and sigma-1 receptor agonist

A spirocyclic thiadiazine-piperidine compound developed at the Israel Institute for Biological Research as a dual allosteric M1 muscarinic and sigma-1 receptor agonist, distinguished by sub-nanomolar allosteric potency at M1, disease-modifying preclinical efficacy in transgenic Alzheimer’s disease models, and active clinical development across schizophrenia, frontotemporal dementia, and Alzheimer’s disease indications.

Abstract

ANAVEX 3-71 (development code AF710B; CAS 1235733-73-9) is a synthetic spirocyclic thiadiazine-piperidine compound and a dual allosteric agonist at the M1 subtype of the muscarinic acetylcholine receptor and the sigma-1 receptor (SIGMAR1). The compound was invented by Abraham Fisher at the Israel Institute for Biological Research (IIBR) in Ness Ziona, Israel, as the fourth generation of a series of cholinergic agonists (AF102B, AF267B, AF292, AF710B) with progressively greater selectivity and allosteric character at the M1 muscarinic receptor. ANAVEX 3-71 emerged from high-throughput receptogram profiling as a compound with sub-nanomolar allosteric binding affinity at M1 muscarinic receptors (approximately 0.05 nM) and nanomolar affinity at the sigma-1 receptor (Ki approximately 1.3 nM), with no agonistic activity at M2 through M5 muscarinic subtypes, no significant binding at alpha-4-beta-2 or alpha-7 nicotinic receptors, and a clean off-target profile across 83 additional G-protein-coupled receptors, ion channels, and transporters screened at 10 micromolar. The preclinical pharmacology of ANAVEX 3-71 has been characterized principally in three studies using transgenic rodent models of Alzheimer’s disease. Fisher et al. (2016) reported that AF710B at 10 micrograms per kilogram per day intraperitoneally for two months in 3xTg-AD mice reversed cognitive deficits in the Morris water maze, decreased BACE1, GSK3-beta activity, and tau phosphorylation at multiple epitopes (AT180, AT270, PHF-1), reduced soluble and insoluble amyloid-beta 40 and 42, and rescued mushroom dendritic spine loss in hippocampal neuronal cultures at 30 nanomolar. Hall et al. (2018) extended these findings to McGill-R-Thy1-APP transgenic rats, demonstrating that oral treatment at 10 micrograms per kilogram per day for 4.5 months at 13 months of age (postplaque) reverted cognitive deficits, reduced amyloid pathology and neuroinflammation, and increased cerebrospinal fluid amyloid clearance, with effects maintained following a 5-week treatment interruption consistent with disease-modifying rather than symptomatic activity. Orciani et al. (2023) demonstrated that early (preplaque, 7 months of age) treatment at the same dose for 7 months prevented cognitive impairment, reduced hippocampal plaque burden and cortical amyloid-beta peptides, attenuated microglial and astrocytic neuroinflammation, and rescued pro-BDNF to mature BDNF conversion, with effects persisting through a 4-week washout. Human pharmacokinetics characterized in a Phase 1 single ascending dose study (NCT04442945; 36 healthy volunteers; 5 to 200 mg) demonstrate linear, dose-proportional, and time-invariant pharmacokinetics with a mean apparent terminal elimination half-life of 3.56 hours for the parent compound and 6.59 hours for the M8 metabolite. No clinically relevant effects on QTc or other electrocardiographic parameters were observed across the full studied dose range. Food had no effect on the pharmacokinetics of ANAVEX 3-71 or its M8 metabolite. Clinical development is ongoing across multiple indications. A Phase 2 study in schizophrenia (NCT06245213; 71 subjects) reported dose-dependent improvements in electroencephalographic biomarkers and favorable safety and tolerability with no serious treatment-emergent adverse events. A modified-release oral tablet enabling once-daily dosing was successfully developed in a Phase 1b study completed in October 2025. ANAVEX 3-71 is not approved by any regulatory authority and is supplied as a research-grade preparation. This monograph reviews the chemistry, dual-receptor pharmacology, preclinical pharmacology in transgenic Alzheimer’s models, human pharmacokinetics, the clinical evidence base, sourcing and quality verification, handling considerations, interaction profile, adverse event signal, and a comparative assessment of five mechanistically related compounds against ANAVEX 3-71 on five competency standards.

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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.

May 22, 2026
CAD-31

Our opinion on this compoundNovel, promising

58/100

Salk-origin AMPK geroneuroprotector with genuine dual neurogenesis-neuroprotection profile, preclinical only

Look, CAD-31 earns its score from the quality of the science, not a crowded clinical evidence base. The Salk Institute’s Cellular Neurobiology Lab ran four generations of phenotypic optimization on curcumin-derived scaffolds, screened more than 200 derivatives of J147, and selected CAD-31 specifically for superior potency in a human embryonic stem cell-derived neural precursor cell neurogenesis assay. Unlike most compounds in this space, which optimize for neuroprotection alone, CAD-31 was pushed toward a combined neurogenic and neuroprotective profile, and that dual activity is real. Nestin, Pax6, doublecortin, and Ki67 markers come up 2.6 to 5.2-fold relative to J147 at matched concentrations in hNPC cultures, which is the distinctive pharmacological advance of this compound within the series.

The mechanism story is what we find most interesting. CAD-31 activates AMPK via phosphorylation at Thr172 and inhibits ACC1 at Ser79, pulling free fatty acid synthesis down and elevating acetyl-CoA and ketone body availability in neural tissue. This is metabolic reprogramming of the aging brain, not conventional receptor binding. The upstream target is likely the alpha-F1 subunit of mitochondrial ATP synthase, where the parent J147 is confirmed to bind; CAD-31 shares the downstream signature, though formal binding confirmation for CAD-31 specifically is still pending. Thats a knowledge gap worth noting, and it keeps the mechanism score from climbing higher than it otherwise might.

In vivo data is preclinical only, but its good preclinical. The APPswe/PS1deltaE9 therapeutic paradigm study showed hippocampal memory rescue in symptomatic 10-month-old mice across fear conditioning, Morris water maze, and elevated plus maze. The SAMP8 accelerated-aging work is actually the more compelling data point: roughly 30% median lifespan extension when administered in the final quarter of life, with preservation of youthful gene, protein, and metabolite profiles in the brain. Brain penetrance is excellent: brain-to-plasma ratio of 2.8 at eight hours, peak brain concentrations roughly tenfold above the in vitro EC50 range of 12 to 95 nanomolar. The preclinical safety screen is clean across hERG, Ames, micronucleus, and five major CYP enzymes at concentrations well above the effective range.

What keeps the score where it is: all of this comes from one lab. The Salk group is serious and the methodology is transparent, but independent replication is absent. The translational arrow from transgenic AD mouse models to people has a historically weak record across the whole field, and CAD-31 hasnt entered Phase 1 while the parent compound J147 has completed safety trials (NCT03838185). As a bench tool for studying AMPK-axis metabolic neuroprotection and adult neurogenesis in human neural precursors, it’s genuinely useful. As a clinical candidate, it’s interesting but unvalidated, sitting at the preclinical frontier. We think independent replication and CNS pharmacodynamic readouts outside the transgenic AD context would change this score meaningfully.

Novelty

70

Mechanism promise

76

In-category differentiation

65

Evidence quality

35

Translational signal

33

Research bench value

60

Rationale Fourth-generation curcumin-scaffold optimization from the Salk Institute with a mechanistically interesting ATP synthase-AMPK-acetyl-CoA axis and distinctive human NPC neurogenesis activity; scored down by single-lab origin, zero clinical data for CAD-31 specifically, and the historically weak AD mouse-to-human translational arrow.

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

Trifluoroacetyl hydrazone geroneuroprotector with AMPK-mediated neuroprotective and neurogenic activity

A synthetic trifluoroacetyl hydrazone derived from the curcumin scaffold via four generations of phenotypic optimization at the Salk Institute, selected for combined neuroprotective and neurogenic activity in human neural precursor cells, with preclinical efficacy in transgenic Alzheimer’s disease and accelerated-aging mouse models through AMPK-dependent modulation of fatty acid metabolism, inflammation, and acetyl-CoA homeostasis.

Abstract

CAD-31 (CAD-031; CAS 2071209-49-7) is a synthetic trifluoroacetyl hydrazone (molecular weight 404.31, C18H14F6N2O2) derived from the curcumin scaffold through four generations of phenotypic optimization at the Cellular Neurobiology Laboratory of the Salk Institute for Biological Studies. The compound was selected from a library of more than 200 derivatives of the parent compound J147 on the basis of superior potency in a human embryonic stem cell-derived neural precursor cell (hNPC) neurogenesis assay and retention of broad neuroprotective activity across six cell culture models of age-associated brain toxicity [1, 2]. In assays for trophic factor withdrawal, oxidative stress (oxytosis), in vitro ischemia, extracellular and intracellular amyloid-beta toxicity, and BDNF-like neurotrophic activity, CAD-31 demonstrates EC50 values in the range of 12 to 95 nanomolar, comparable to J147 in most assays and superior in the trophic factor withdrawal model [1]. Neurogenesis markers in human neural precursor cells (nestin, Pax6, doublecortin, Ki67) are elevated 2.6- to 5.2-fold relative to J147 at matched concentrations, representing the distinctive pharmacological advance of CAD-31 within the compound series [2]. The molecular mechanism of CAD-31 converges on the AMP-activated protein kinase (AMPK) signaling cascade. CAD-31 activates AMPK by phosphorylation at threonine 172 and inhibits the downstream target acetyl-CoA carboxylase 1 (ACC1) by phosphorylation at serine 79, resulting in elevated acetyl-CoA levels, reduced free fatty acid synthesis, and increased ketone body availability in the brain [1, 6]. This metabolic reprogramming is accompanied by reductions in inflammatory markers (vascular cell adhesion molecule, receptor for advanced glycation endproducts, clusterin) and increases in synaptic proteins (drebrin, activity-regulated cytoskeleton-associated protein) in hippocampal tissue of transgenic Alzheimer’s disease mice [1]. In the therapeutic APPswe/PS1deltaE9 transgenic mouse model of Alzheimer’s disease, CAD-31 administered orally at approximately 10 mg/kg/day to symptomatic 10-month-old mice for three months rescued hippocampus-dependent memory deficits in fear conditioning, Morris water maze, and elevated plus maze paradigms to wild-type control levels [1]. In rapidly aging SAMP8 mice, CAD-31 extended median lifespan by approximately 30 percent when administered in the final quarter of life, with corresponding preservation of youthful gene, protein, and metabolite expression profiles in the brain [6]. Pharmacokinetic characterization in rats demonstrates brain penetrance with a brain-to-plasma ratio of 2.8 at eight hours after oral gavage at 20 mg/kg, and maximum brain concentrations approximately tenfold higher than the in vitro EC50 values [1]. Preclinical safety screening shows no acute toxicity at 2 g/kg, no activity in hERG, Ames, or micronucleus assays, and no inhibition of five major cytochrome P450 enzymes at concentrations more than tenfold above the effective range [1]. No formal molecular target has been identified for CAD-31; the parent compound J147 binds the alpha-F1 subunit of mitochondrial ATP synthase (ATP5A), and CAD-31 likely engages the same or a closely related target given the shared downstream AMPK activation and neuroprotective phenotype [7, 8]. CAD-31 has not entered human clinical trials. The parent compound J147 completed a Phase 1 safety study (NCT03838185), and the related compound CMS121 has received National Institutes of Health funding for Investigational New Drug studies [5]. This monograph reviews the chemistry and synthesis lineage, molecular pharmacology, preclinical pharmacokinetics, in vivo efficacy in transgenic Alzheimer’s disease and accelerated-aging models, the safety profile, and a comparative assessment of five compounds in the geroneuroprotector and Alzheimer’s disease therapeutic landscape against CAD-31. The compound is available as a research-grade preparation from multiple chemical suppliers; it has no approved medical indication in any jurisdiction.

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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.

May 22, 2026
Fasudil

Our opinion on this compoundEstablished, active research

59/100

First approved systemic ROCK inhibitor, uniquely positioned for CNS and ALS translational research

Look, fasudil occupies a genuinely unusual position in the research catalog. It was first synthesized in 1984, approved in Japan in 1995, and has been standard of care for cerebral vasospasm in Japanese neurosurgical units for three decades. And yet the ROCK pathway remains one of the more underexplored kinase systems in CNS and cardiovascular medicine, and fasudil is still the only ROCK inhibitor approved for systemic clinical use anywhere in the world. That combination of age and continued relevance is what landed it in the established-active tier rather than historical trivia.

The mechanism is what keeps this compound interesting. ROCK1 and ROCK2 sit downstream of Rho GTPase signaling and regulate a surprisingly broad biology: myosin light chain phosphorylation and cytoskeletal tension, NF-kB inflammatory cascades, microglial activation states, axonal retraction, and the PPARalpha-NOX neuroprotective axis. Fasudil inhibits both isoforms at the ATP-binding domain, with ROCK2 slightly preferred (Ki approximately 47 nM versus 76 nM for ROCK1). What most investigators miss: the parent compound is effectively a prodrug. Hepatic aldehyde oxidase converts fasudil to hydroxyfasudil within about thirty minutes, and hydroxyfasudil has comparable or greater ROCK potency plus a plasma half-life roughly ten times longer. Ignoring this when designing PK studies is a recurring mistake in the secondary literature.

The evidence base is real, if geographically concentrated. The pivotal Shibuya 1992 trial in 267 patients was a genuine double-blind RCT, and a meta-analysis across 8 trials confirmed vasospasm benefit at an odds ratio of 0.48. In pulmonary hypertension, meta-analyses covering up to 865 patients show significant improvements in pulmonary artery pressure and 6-minute walk distance. The most recent and, honestly, the most interesting data point is the ROCK-ALS Phase 2 trial in 120 patients: safety confirmed, electrophysiological biomarker preservation demonstrated, and CSF penetration of hydroxyfasudil confirmed at concentrations matching preclinical efficacy targets. That last finding matters considerably for any investigator building a CNS case.

The differentiation story is underappreciated. Y-27632 dominates in vitro ROCK work but hasnt been through any clinical trial. Ripasudil and netarsudil are topical ophthalmic preparations. Belumosudil is ROCK2-selective and approved only for chronic graft-versus-host disease. Fasudil is the only systemic, clinical-grade ROCK inhibitor with a real human PK and safety dataset, which gives investigators trying to bridge bench findings to clinic a practical foothold that doesnt exist anywhere else in the class.

We think the honest limitation is the age: thirty-plus years old, not approved in the US or EU, and every lot should come with analytical verification of identity and purity. The novelty score reflects that frankly. But the ALS signal, the expanding neurodegeneration research program, and the singular position as the only systemically-validated ROCK inhibitor keep this well above the noise floor. If you’re doing ROCK biology with any translational intent, this is where the human data actually lives.

Novelty

38

Mechanism promise

62

In-category differentiation

65

Evidence quality

67

Translational signal

68

Research bench value

58

Rationale Fasudil scores above the noise floor primarily on differentiation and translational signal: it remains the only ROCK inhibitor approved for systemic clinical use anywhere, and the ROCK-ALS Phase 2 data with confirmed CSF penetration of hydroxyfasudil gives it a real translational foothold newer bench tools like Y-27632 simply don’t have. Novelty is appropriately penalized for a 1984 compound; the expanding neurodegeneration program keeps it active but doesn’t rescue the age.

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

Isoquinolinesulfonamide Rho-associated protein kinase (ROCK) inhibitor with vasodilatory, anti-inflammatory, and neuroprotective activity

An isoquinolinesulfonamide kinase inhibitor developed by Asahi Kasei as the first clinically approved ROCK inhibitor, registered in Japan and China for cerebral vasospasm after subarachnoid hemorrhage, with expanding investigational applications in pulmonary hypertension, amyotrophic lateral sclerosis, and cardiovascular disease.

Abstract

Fasudil (HA-1077, AT-877), the isoquinolinesulfonamide derivative of the H-series protein kinase inhibitors first described by Hidaka et al. in 1984, is the only Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor approved for systemic clinical use and the first protein kinase inhibitor to receive regulatory approval for any indication. Developed by Asahi Kasei Pharma (Tokyo, Japan) and marketed as Eril, fasudil has been approved in Japan since 1995 and in China for the treatment of cerebral vasospasm following aneurysmal subarachnoid hemorrhage, where it is standard of care in Japanese neurosurgical practice. The compound inhibits ROCK by competitive occupation of the ATP-binding domain, with a Ki of approximately 0.33 micromolar against ROCK activity and modest preferential selectivity for ROCK2 (Ki approximately 47 nanomolar) over ROCK1 (Ki approximately 76 nanomolar) in purified kinase assays. Off-target inhibition of protein kinase A, protein kinase G, protein kinase C, and myosin light chain kinase occurs at approximately 5- to 100-fold higher concentrations. The principal metabolic transformation is rapid hepatic conversion to hydroxyfasudil by aldehyde oxidase (not cytochrome P450), producing an active metabolite with ROCK inhibitory potency similar to or greater than the parent compound and a substantially longer plasma half-life (approximately 5.5 hours versus 0.55 hours for fasudil). This metabolic profile renders fasudil effectively a prodrug of hydroxyfasudil in the oral context. The clinical evidence base in cerebral vasospasm rests on a pivotal 267-patient double-blind placebo-controlled trial (Shibuya et al. 1992) demonstrating significant reductions in angiographic vasospasm (38 versus 61 percent), symptomatic vasospasm (35 versus 50 percent), and poor outcome on the Glasgow Outcome Scale (12 versus 26 percent), confirmed by a 1,462-patient postmarketing surveillance study and a meta-analysis of 8 trials (odds ratio 0.48 for symptomatic vasospasm). Head-to-head comparison with nimodipine demonstrated comparable or superior outcomes (74.5 versus 61.7 percent good clinical outcome). Expanding investigational programs span pulmonary arterial hypertension, where meta-analyses of up to 865 patients demonstrate significant reductions in pulmonary artery pressure, vascular resistance, and 6-minute walk distance with no serious adverse events; and amyotrophic lateral sclerosis, where the 120-patient ROCK-ALS Phase 2 trial confirmed safety, demonstrated significant electrophysiological biomarker preservation (motor unit number index), and confirmed cerebrospinal fluid penetration of the active metabolite at concentrations matching preclinical efficacy. This monograph reviews the chemistry, synthesis, and structure-activity relationships of fasudil; the kinase inhibition profile and downstream signaling including ROCK-mediated myosin light chain phosphorylation, NF-kappaB inflammatory signaling, PPARalpha-NOX neuroprotective axis, and microglial modulation; the comprehensive pharmacokinetics of fasudil and hydroxyfasudil from the first formal Phase I oral bioavailability study; the preclinical evidence across cerebrovascular, cardiovascular, spinal cord injury, and neurodegenerative disease models; the full clinical evidence base across cerebral vasospasm, pulmonary hypertension, amyotrophic lateral sclerosis, and coronary vasospasm indications; and a comparative assessment against four ROCK inhibitor comparators (Y-27632, ripasudil, netarsudil, belumosudil) and the calcium channel blocker nimodipine. Fasudil is approved only in Japan and China. It is available as a research-grade preparation from established chemical suppliers; investigators should obtain analytical confirmation of identity and purity on every lot.

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May 22, 2026
Elamipretide

Our opinion on this compoundNovel, promising

69/100

First-in-class cardiolipin-binding peptide with FDA approval for Barth syndrome and genuine bench probe utility

Look, the Szeto-Schiller peptide story is one of the more interesting accidents in mitochondrial pharmacology. SS-31 was discovered while chasing opioid receptors, and what came out was something genuinely different: a synthetic tetrapeptide that ignores cytoplasm almost entirely, concentrates more than 1000-fold in the inner mitochondrial membrane, and works not as a stoichiometric antioxidant but as an electrostatic modulator of cardiolipin-containing bilayers. The Mitchell et al. 2020 biophysical work nailed the mechanism with real precision: dissociation constant of 2.0 to 2.9 micromolar for cardiolipin membranes, saturable surface potential reduction, divalent cation exclusion operating independently of membrane potential. Thats not receptor hand-waving. That’s a physical chemistry description of how the compound actually works.

The FDA accelerated approval for Barth syndrome in September 2025 under the name FORZINITY is meaningful, and we should say so plainly. Barth syndrome patients carry tafazzin gene mutations that produce structurally defective cardiolipin, which is precisely the molecular substrate where elamipretide is most directly operative. The TAZPOWER open-label extension showed cumulative 96-meter improvement in six-minute walk distance at 168 weeks (P = 0.003) plus sustained knee extensor gains. Its not a massive effect size, but in a disease with no prior approved therapy and a mechanism this well-matched to the underlying pathology, it clears the bar. The ex vivo failing human heart work is equally compelling: at 100 micromolar, elamipretide selectively restored Complex I-driven oxygen flux and respiratory control ratio in failing tissue but not in non-failing controls, a disease-selective readout you can’t get from a generic antioxidant.

What we don’t love is the broader program. MMPOWER-3 (n = 218) missed its co-primary endpoints in primary mitochondrial myopathy. Heart failure with reduced ejection fraction trials, including PROGRESS-HF and EMBRACE-STEMI, similarly didn’t meet primary endpoints. The dry AMD ReCLAIM series added another failure. The pattern that emerges is a compound that’s exquisitely suited to populations with primary cardiolipin pathology and much weaker in heterogeneous mitochondrial dysfunction. The MMPOWER post hoc finding of a responding subgroup with nuclear DNA replisome variants and CPEO phenotype is genuinely worth following, but its not confirmatory.

For investigators, the bench probe value here is substantial and somewhat independent of the clinical story. Elamipretide is currently the only tool that lets you interrogate cardiolipin-ETC supercomplex interactions in live or freshly explanted tissue without membrane disruption. If your research program touches cardiolipin remodeling, cristae architecture, or supercomplex stability, this is the compound that makes previously unanswerable questions answerable. Pharmacokinetically it’s clean: 92 percent subcutaneous bioavailability, no hepatic metabolism, no CYP interactions, short half-life, predictable dosing profile for preclinical translation.

We place this solidly in the novel-promising tier. The mechanism is first-in-class, the Barth syndrome approval gives the cardiolipin story real regulatory weight, and the bench utility is high. But repeated broad-indication failures and an accelerated rather than full approval temper the translational score. The aging skeletal muscle and CPEO subgroup programs are worth watching closely as the next legible signal.

Novelty

68

Mechanism promise

78

In-category differentiation

75

Evidence quality

58

Translational signal

62

Research bench value

70

Rationale Elamipretide holds the first-in-class cardiolipin-binding mechanism with rigorous biophysical characterization and FDA accelerated approval in Barth syndrome, but a broad clinical program that repeatedly failed primary endpoints outside that genetically defined population keeps translational and evidence scores from climbing higher; bench probe value for cardiolipin-ETC supercomplex work is independently strong.

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

Mitochondria-targeted aromatic-cationic tetrapeptide that binds cardiolipin in the inner mitochondrial membrane

A first-in-class cardiolipin-binding tetrapeptide developed by Szeto and Schiller that stabilizes mitochondrial cristae architecture, restores electron transport chain supercomplex function, and received FDA accelerated approval for Barth syndrome as the first mitochondria-targeted peptide therapeutic.

Abstract

Elamipretide (D-Arg-2′,6′-dimethylTyr-Lys-Phe-NH2; also designated SS-31, MTP-131, and Bendavia) is a synthetic aromatic-cationic tetrapeptide that concentrates more than 1000-fold in the inner mitochondrial membrane, where it binds cardiolipin and modulates membrane surface electrostatics to stabilize cristae architecture, optimize electron transport chain supercomplex assembly, and reduce reactive oxygen species generation at the mitochondrial source. Discovered fortuitously by Hazel Szeto and Peter Schiller during opioid receptor research, the compound was characterized in a foundational 2004 report demonstrating nanomolar-range cytoprotection against oxidative cell death and reperfusion injury in isolated mitochondria and ex vivo cardiac tissue. Biophysical studies by Mitchell et al. (2020) have since established that the primary mechanism is not stoichiometric antioxidant scavenging but rather electrostatic modulation of anionic lipid bilayer properties: SS-31 partitions into the membrane interfacial region with a dissociation constant of 2.0 to 2.9 micromolar for cardiolipin-containing membranes, saturably reduces surface potential, and decreases interfacial divalent cation accumulation by over an order of magnitude; these effects are independent of mitochondrial membrane potential. In freshly explanted failing human heart tissue, elamipretide at 100 micromolar selectively restored Complex I-driven oxygen flux, supercomplex coupling, and respiratory control ratio without affecting non-failing hearts, confirming a disease-selective mechanism operating through cardiolipin-protein interaction stabilization rather than cardiolipin remodeling. Stealth BioTherapeutics advanced elamipretide through clinical programs in Barth syndrome (TAZPOWER), primary mitochondrial myopathy (MMPOWER series), heart failure with reduced ejection fraction (PROGRESS-HF, EMBRACE-STEMI), and dry age-related macular degeneration (ReCLAIM series). The Barth syndrome program, conducted in patients with tafazzin gene mutations and defective cardiolipin remodeling, demonstrated sustained improvements in six-minute walk distance (cumulative 96.1 meters at 168 weeks, P = 0.003) and knee extensor muscle strength in the open-label extension, leading to FDA accelerated approval in September 2025 under the brand name FORZINITY for improvement of muscle strength in adult and pediatric patients weighing at least 30 kilograms. The 12-week randomized crossover portion of TAZPOWER did not meet its primary endpoints, and the pivotal Phase 3 trial in primary mitochondrial myopathy (MMPOWER-3, n = 218) did not meet co-primary endpoints on six-minute walk test and fatigue score, though post hoc analysis identified a responding subgroup with nuclear DNA replisome pathogenic variants and chronic progressive external ophthalmoplegia phenotype. Heart failure and macular degeneration trials similarly did not meet primary endpoints, though exploratory signals in cardiac volume reduction and ellipsoid zone preservation were observed. Pharmacokinetically, elamipretide is administered as a 40 mg subcutaneous injection once daily, with absolute bioavailability of approximately 92 percent, time to peak concentration of 0.5 to 1 hour, plasma elimination half-life of approximately 3 to 4 hours, and exclusively renal elimination with no hepatic metabolism and no cytochrome P450 interactions. This monograph reviews the chemistry and structure, discovery history, cardiolipin-binding pharmacology, pharmacokinetics, preclinical evidence across cardiac, renal, neuroinflammatory, and aging models, the complete clinical trial inventory across all studied indications, sourcing and quality verification, handling, drug interactions, adverse event profile, and a comparative assessment of five mitochondrial therapeutics (idebenone, omaveloxolone, MitoQ, vatiquinone, and coenzyme Q10) against elamipretide on five competency standards.

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May 22, 2026
NPT520-34

Our opinion on this compoundNovel, promising

64/100

First-in-class oral TLR2 antagonist breaking alpha-synuclein feedforward loop, strong mechanism, no patient data yet

Honestly, NPT520-34 is one of the more conceptually interesting compounds we’ve reviewed in the neurodegeneration space. The core story is a feedforward loop that’s been building in the Parkinson’s literature for years: oligomeric alpha-synuclein activates TLR2 on microglia and neurons, TLR2 activation suppresses autophagy through the AKT/mTOR axis, which lets alpha-synuclein accumulate further, which drives more TLR2 signaling. Neuropore’s compound interrupts that cycle at the TLR2 node. That’s not a trivial target choice. Postmortem PD brain data shows TLR2 neuronal expression climbing from roughly 3 percent in control tissue to 47 percent in late-stage disease, which is the kind of biological anchor that justifies building a selective antagonist for it. The dual pharmacology is genuinely elegant: you clear the aggregates and suppress the inflammation from the same single target.

The preclinical package in the mThy1-alpha-synuclein Line 61 transgenic model is solid for a small-molecule CNS program. Daily dosing at 0.5 to 10 mg/kg produced dose-dependent reductions in total alpha-synuclein in the neocortex (P less than 0.0001 at the higher doses), reductions in proteinase K-resistant synuclein in the striatum, and functional improvements in grip strength and gait analysis. The acute LPS-challenge data showing suppression of IL-6, TNF-alpha, and MIP-2 adds to the anti-inflammatory story. Mouse PK confirms brain penetrance in a dose-linear fashion, and the oral bioavailability is essential for any realistic chronic neurodegeneration program.

Phase 1 (NCT03954600) enrolled 49 healthy volunteers across single and multiple ascending doses up to 500 mg/day for 14 days. Dose-linear PK, half-life around 8 hours, no serious adverse events, headache as the primary complaint. That’s a clean safety readout. The FDA orphan designation for ALS in August 2019 signals regulators found the mechanistic rationale credible. But we have to be honest about where the evidence stops: the Phase 1 data remains unpublished in a peer-reviewed journal, theres no registered Phase 2 in PD or ALS patients, and essentially all the preclinical data comes from within the Neuropore program itself. The Line 61 model is well-regarded as a synuclein overexpression tool, but transgenic PD models have a stubborn history of poor clinical translation.

What we like here is the mechanism specificity and the oral brain-penetrant profile. As a research tool for TLR2-mediated neuroinflammation in synucleinopathy models, this is genuinely useful in a way that most peptide candidates are not. The comparison field is worth noting: anle138b is still preclinical-only, prasinezumab showed signal only in fast-progressors, nilotinib essentially failed its PD trials. NPT520-34 occupies a distinct mechanistic lane. What we dont like is the development pause. No public Phase 2 timeline, a silent publication record on the clinical data, and without patient efficacy numbers the translational signal stays entirely mechanistic. Promising first-in-class compound, real questions about whether anyone is still actively pushing it forward.

Novelty

75

Mechanism promise

78

In-category differentiation

74

Evidence quality

42

Translational signal

40

Research bench value

62

Rationale High novelty and mechanism scores reflect first-in-class TLR2 antagonism with a well-defined feedforward-loop rationale and confirmed oral CNS penetrance; evidence and translational scores are capped by single-consortium preclinical data, unpublished Phase 1 results, and a complete absence of Phase 2 patient efficacy data.

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

Orally bioavailable, brain-penetrant small molecule toll-like receptor 2 (TLR2) antagonist with dual activity promoting autophagic clearance of alpha-synuclein aggregates and attenuating neuroinflammation

A first-in-class small molecule TLR2 antagonist developed by Neuropore Therapies for Parkinson’s disease and amyotrophic lateral sclerosis, acting through dual suppression of neuroinflammation and enhancement of autophagic protein clearance in neurodegenerative synucleinopathies.

Abstract

NPT520-34 is an orally bioavailable, brain-penetrant small molecule antagonist of toll-like receptor 2 (TLR2), developed by Neuropore Therapies, Inc. (San Diego, California) as a disease-modifying therapeutic candidate for Parkinson’s disease and amyotrophic lateral sclerosis. The compound was identified through cell-based assays of alpha-synuclein clearance and subsequently characterized for two complementary pharmacological actions: enhancement of autophagic clearance of neurotoxic protein aggregates and direct attenuation of neuroinflammation mediated by microglia and astrocytes [1]. The mechanistic rationale targets TLR2, a pattern-recognition receptor of the innate immune system that is upregulated approximately twofold in postmortem Parkinson’s disease brain tissue, with neuronal TLR2 expression increasing from approximately 3 percent of neurons in control brain to 47 percent in late-stage disease [3]. Neuron-released oligomeric alpha-synuclein acts as an endogenous agonist of TLR2, driving a feedforward loop of TLR2 activation, AKT/mTOR-dependent autophagy inhibition, alpha-synuclein accumulation, and neuroinflammatory cytokine release [2, 4]. NPT520-34 is proposed to interrupt this cycle through TLR2 antagonism. In the principal preclinical study, daily intraperitoneal administration of NPT520-34 at 0.5 to 10 mg/kg to mThy1-alpha-synuclein (Line 61) transgenic mice for one or three months produced statistically significant reductions in total alpha-synuclein in the neocortex (P < 0.0001 at 5 and 10 mg/kg), reductions in proteinase K-resistant alpha-synuclein in the striatum (P < 0.05 at 1, 5, and 10 mg/kg), and reductions in the neuroinflammation markers TSPO and TLR2 mRNA, with concurrent improvements in grip strength (P < 0.001 to P < 0.0001), forelimb clasping, and computerized gait analysis parameters [1]. In a separate acute lipopolysaccharide-challenge model, a single dose of NPT520-34 reduced plasma levels of pro-inflammatory cytokines including interleukin-6, tumor necrosis factor alpha, and macrophage inflammatory protein 2 [1]. In vitro, NPT520-34 increased LC3 puncta accumulation in B103 neuroblastoma cells at concentrations of 1 to 10 micromolar, consistent with autophagy induction [1]. Mouse pharmacokinetic studies demonstrated dose-dependent linear exposures in both plasma and brain tissue, confirming blood-brain barrier penetration [1]. In a Phase 1 randomized, double-blind, placebo-controlled trial (NCT03954600) enrolling 49 healthy adult volunteers, single ascending oral doses from 125 to 1000 mg and multiple ascending doses of 250 to 500 mg daily for 14 days demonstrated dose-linear pharmacokinetics with an elimination half-life of approximately 8 hours [7, 9, 11]. NPT520-34 was safe and well tolerated at all doses tested, with no serious adverse events, no discontinuations, and headache as the most frequently reported adverse event [9, 11]. The U.S. Food and Drug Administration granted orphan drug designation for the treatment of amyotrophic lateral sclerosis in August 2019 [10]. As of the date of this monograph, no Phase 2 trials in patients with Parkinson's disease or amyotrophic lateral sclerosis have been registered, and peer-reviewed publication of the Phase 1 pharmacokinetic and safety data remains pending. Investigators should treat the available clinical data as preliminary. This monograph reviews the chemistry, the TLR2-mediated mechanism of action in the context of the broader synucleinopathy literature, the preclinical pharmacology across neurodegenerative disease models, the Phase 1 clinical data, and a comparative assessment of five alternative alpha-synuclein-targeting therapeutic candidates. The compound is not approved for any indication in any jurisdiction and is available only for research use.

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May 22, 2026
Danavorexton

Our opinion on this compoundNovel frontier

72/100

First-in-class small-molecule OX2R agonist with extraordinary Phase 1 human signal, constrained by IV route and advancing oral successors

Look, danavorexton earns its place at the frontier in a way that few investigational compounds do: its the first nonpeptide small-molecule orexin 2 receptor agonist to generate human clinical proof-of-concept, and the effect sizes in narcolepsy type 1 are striking enough that they essentially validated the orexin replacement hypothesis in a single Phase 1 program. That matters for how we think about this class.

The chemistry story is genuinely interesting on its own. Takeda’s medicinal chemistry campaign converted a micromolar hit (EC50 570 nM) into a low-nanomolar agonist (EC50 5.5 nM) with greater than 18,000-fold selectivity for OX2R over OX1R. Selectivity that extreme in a receptor pair this structurally similar is mechanistically meaningful, and the cryo-EM structures of the OX2R-G protein complex at 3.2 to 3.3 angstrom resolution show exactly why: two residue differences at positions 2.61 and 3.33 create steric and desolvation disparities that danavorexton exploits through a compact U-shaped conformation and a critical sulfonamide-Gln134 hydrogen bond. That structural resolution is a research contribution independent of the therapeutic story, and it makes danavorexton a useful anchor compound for anyone building OX2R pharmacophore models.

What we find most compelling is the translational signal. In NCT03748979, narcolepsy type 1 participants maxed out the Maintenance of Wakefulness Test ceiling (40 minutes across all sessions), reduced cataplexy episodes to zero during infusion, and normalized Epworth Sleepiness Scale scores from 18.6 to 0.0 by day 7. Placebo-adjusted sleep latency improvement of 29.4 minutes in idiopathic hypersomnia. Reversal of remifentanil-induced respiratory depression (minute volume increase of 13.0 L/min, p less than 0.001) without reversing analgesia. These arent modest signals; the mechanism-to-effect arrow here is unusually clean.

The honest limitation is the route. Intravenous infusion over nine hours is a proof-of-concept instrument, not a clinical product. Takedas program knew this: TAK-994 demonstrated even stronger oral efficacy but was discontinued after three Hy’s law hepatotoxicity cases, and TAK-861 (oveporexton) is now advancing toward Phase 3 registration with no hepatic signal. Danavorexton’s therapeutic path is effectively closed. What remains is its value as the most pharmacologically characterized OX2R agonist in the literature, with six registered clinical studies, a cryo-EM resolved structure, and unusually clean PK-PD data from controlled IV administration.

For investigators working on sleep circuitry, orexin-system biology, opioid-respiratory crosstalk, or GPCR structural pharmacology, this compound is a legitimate and well-validated research tool. Evidence is Phase 1-weight, which is why overall doesn’t reach the high seventies, but the novelty of the structural class and the magnitude of the human signal place it solidly in frontier territory.

Novelty

70

Mechanism promise

75

In-category differentiation

72

Evidence quality

58

Translational signal

80

Research bench value

75

Rationale Scores are driven upward by a genuinely paradigm-defining translational signal in Phase 1 narcolepsy and idiopathic hypersomnia studies, novel structural biology (first cryo-EM OX2R agonist complex resolved at 3.2 Å), and first-in-class status as the only small-molecule OX2R agonist with clinical proof of concept. Evidence and differentiation scores are held back by Phase 1-only weight and the reality that oral successors have already moved the field past this specific molecule as a therapeutic candidate.

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

Selective orexin 2 receptor agonist (nonpeptide, intravenous piperidine carbamate)

A selective nonpeptide orexin 2 receptor agonist developed at Takeda Pharmaceutical Company, the first small-molecule OX2R agonist to achieve clinical proof of concept for orexin replacement therapy across narcolepsy type 1 and type 2, idiopathic hypersomnia, obstructive sleep apnea, and opioid-induced respiratory depression.

Abstract

Danavorexton (TAK-925) is a potent, selective, brain-penetrant, nonpeptide orexin 2 receptor (OX2R) agonist developed by Takeda Pharmaceutical Company as the first small-molecule orexin receptor agonist to enter clinical development. Identified through high-throughput screening and optimized through a medicinal chemistry campaign that converted a micromolar-potency hit (EC50 570 nM) into a low-nanomolar agonist (EC50 5.5 nM in calcium mobilization assays) with greater than 18,000-fold selectivity for human OX2R over OX1R, danavorexton is a (2R,3S)-piperidine carbamate bearing a cis-4-phenylcyclohexyl ether and a methylsulfonamide pharmacophore. The compound adopts a compact U-shaped conformation that engages the OX2R orthosteric pocket through a critical hydrogen bond between the sulfonamide nitrogen and Gln134(3.32), as resolved by two cryo-electron microscopy structures of the OX2R-G protein complex at 3.2 to 3.3 angstrom resolution. Selectivity over OX1R arises from subtle differences at only two residues (Thr111(2.61) and Thr135(3.33) in OX2R versus Ser and Ala at the corresponding positions in OX1R) that alter steric complementarity and desolvation within the orthosteric pocket. Administered exclusively by intravenous infusion, danavorexton has completed Phase 1 clinical studies in narcolepsy type 1, narcolepsy type 2, idiopathic hypersomnia, obstructive sleep apnea with residual excessive daytime sleepiness, and opioid-induced respiratory depression, collectively enrolling over 150 participants across six registered trials. In a multiple-rising-dose study (NCT03748979), danavorexton at 44 mg intravenous over 9 hours produced maximal Maintenance of Wakefulness Test sleep latency (40 minutes in all sessions) in all narcolepsy type 1 participants, reduced cataplexy episodes to zero during infusion, and normalized the Epworth Sleepiness Scale score from a baseline of 18.6 to 0.0 by day 7. Comparable wakefulness-promoting effects were demonstrated in narcolepsy type 2, idiopathic hypersomnia (placebo-adjusted sleep latency improvement of 29.4 minutes), and sleep-deprived healthy volunteers (sleep latency of 31.8 minutes at 112 mg versus 9.2 minutes on placebo). In a crossover study of remifentanil-induced respiratory depression, danavorexton reversed respiratory depression (minute volume increase of 13.0 L/min at 19 mg, p < 0.001) and sedation without reversing opioid analgesia. Human pharmacokinetics are characterized by dose-proportional plasma concentrations, a terminal half-life of approximately 3 to 5 hours, negligible accumulation with daily 9-hour infusions, and a cerebrospinal fluid-to-plasma concentration ratio of approximately 2.8 percent. The compound is well tolerated across all studied populations. The most common drug-related adverse events are pollakiuria (urinary frequency), transient blood pressure elevation, insomnia, headache, and dizziness, all predominantly mild in severity. No hepatotoxicity has been observed, distinguishing danavorexton from its oral successor TAK-994 (firazorexton), which demonstrated exceptional efficacy in a Phase 2 narcolepsy trial but was discontinued following drug-induced liver injury in three participants meeting Hy's law criteria. The second-generation oral OX2R agonist TAK-861 (oveporexton), structurally distinct from both danavorexton and TAK-994, has completed a positive Phase 2 trial with no hepatic signal and is advancing toward Phase 3 registration. This monograph reviews the medicinal chemistry, structural biology, receptor pharmacology, pharmacokinetics, preclinical and clinical evidence base, adverse event profile, sourcing and handling considerations, and a comparative assessment of danavorexton against four alternative agents in the narcolepsy and excessive daytime sleepiness pharmacotherapy space (TAK-994, TAK-861, pitolisant, solriamfetol) on five competency standards. Danavorexton is not approved for any indication in any jurisdiction. It is an investigational compound available in research-grade preparations; investigators should obtain analytical confirmation of identity and purity on every lot.

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May 22, 2026
Iclepertin

Our opinion on this compoundNiche research probe

46/100

Best-in-class GlyT1 probe with real Phase II signal, sunk by decisive Phase III replication failure

Iclepertin (BI 425809) came out of Boehringer Ingelheim’s push to do the GlyT1 inhibition story properly. The mechanism rationale is real: block GlyT1 astrocytic reuptake, saturate the NMDA glycine-B co-agonist site, and you’re effectively turning up the gain on glutamatergic neurotransmission in circuits that NMDA hypofunction models have implicated in schizophrenia’s cognitive deficits for three decades. At 5.0 nM IC50 in SK-N-MC cells, the compound is genuinely potent, and the azabicyclo[3.1.0]hexane scaffold with its three defined stereocenters gives you selectivity you dont get from sarcosine or D-serine. Mechanistically, this is probably the cleanest GlyT1 probe the field has produced.

The Phase II result (NCT02832037) was the thing that made people pay attention. A standardized effect size of 0.34 on the MCCB composite at 10 mg isn’t a throwaway signal. Honestly, in a space where cognitive endpoints in schizophrenia almost never move, 0.34 is remarkable. The qEEG substudy showed target engagement consistent with the occupancy modeling. There was a dose-response that made pharmacological sense, tracking the inverted-U relationship the preclinical team had flagged early. We liked this compound going into Phase III.

And then the CONNEX programme landed. 1835 patients across three trials, well-powered, and the Phase II signal did not replicate. This is where the story gets genuinely complicated for the research community. The failure isn’t obviously interpretable as “the mechanism is wrong.” Bitopertin, Roche’s GlyT1 inhibitor, failed Phase III earlier, which should have been a warning sign. The open question now is whether the NMDA hypofunction/GlyT1 approach is fundamentally broken for CIAS, or whether both programmes had endpoint selection, patient stratification, and concomitant antipsychotic confounds that swamped a real but modest effect. The field hasn’t reached consensus, and thats actually an interesting scientific problem.

What we think now: as a clinical candidate for CIAS, iclepertin is done. But as a probe compound, it’s still the most potent and selective small-molecule GlyT1 inhibitor in the public literature, and any investigator working on glutamate biology, NMDA receptor pharmacology, or the synaptic glycine co-agonist system has legitimate reasons to reach for it. The inverted-U dose-response data is useful for bench work on its own terms. You can use this compound to interrogate GlyT1 occupancy thresholds in rodent cognitive models in ways sarcosine or D-serine simply don’t allow.

What we don’t like: two large Phase III failures for the same mechanistic class is a heavy prior against the clinical translation story. The path from GlyT1 occupancy to durable cognitive benefit in schizophrenia populations looks harder than the preclinical models ever suggested, and that’s a problem the whole glutamate field is still working through. Score reflects the probe value as real, the clinical value as spent.

Novelty

38

Mechanism promise

45

In-category differentiation

47

Evidence quality

62

Translational signal

35

Research bench value

55

Rationale Iclepertin is the most potent and selective small-molecule GlyT1 inhibitor available and produced the strongest Phase II CIAS signal in its class (ES 0.34 on MCCB), but the CONNEX Phase III programme across 1835 patients failed to replicate; it scores as a serious research probe with intact mechanistic rationale, but the translational path for the primary clinical indication is broken and the GlyT1/CIAS hypothesis is now two-for-two in Phase III failure.

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

Selective glycine transporter type 1 (GlyT1) inhibitor for glutamatergic NMDA receptor enhancement

A potent azabicyclo[3.1.0]hexane methanone GlyT1 inhibitor developed by Boehringer Ingelheim to normalize glutamatergic hypofunction in schizophrenia, distinguished by positive Phase II cognitive efficacy signals (standardized effect size 0.34 on MCCB at 10 mg) and subsequent failure to replicate in the 1835-patient Phase III CONNEX programme.

Abstract

Iclepertin (BI 425809) is a potent and selective inhibitor of glycine transporter type 1 (GlyT1) with an IC50 of 5.0 nanomolar in human SK-N-MC cells, developed by Boehringer Ingelheim for the treatment of cognitive impairment associated with schizophrenia (CIAS). The compound is an orally bioavailable azabicyclo[3.1.0]hexane methanone bearing two trifluoromethyl groups and a methylsulfonyl substituent, with three defined stereocenters and a molecular weight of 512.42 g/mol. By blocking the reuptake of glycine from the synaptic cleft into astrocytes and presynaptic terminals, iclepertin increases synaptic glycine concentration at the glycine-B co-agonist site of the N-methyl-D-aspartate (NMDA) receptor, thereby enhancing glutamatergic neurotransmission. This mechanism addresses the NMDA receptor hypofunction hypothesis of schizophrenia, which posits that reduced glutamatergic signaling contributes to the cognitive deficits observed in the disorder.

Pharmacokinetically, iclepertin exhibits a terminal half-life of 34 to 59 hours, supporting once-daily oral dosing with steady-state conditions achieved by day 6. Oral bioavailability is approximately 72 percent for a 25 mg tablet under fasted conditions. The compound is metabolized predominantly (90 percent or greater) by cytochrome P450 3A4, rendering it sensitive to strong CYP3A4 inhibitors (approximately 6-fold AUC increase with itraconazole) and inducers (approximately 90 percent AUC reduction with rifampicin). In Phase I studies, oral administration of 10 mg produced a dose-dependent approximately 50 percent increase in cerebrospinal fluid glycine levels, confirming central target engagement.

The Phase II clinical programme produced divergent results across indications. In a 509-patient randomized, double-blind, placebo-controlled trial in schizophrenia (NCT02832037), iclepertin at 10 mg once daily for 12 weeks produced a statistically significant improvement on the MATRICS Consensus Cognitive Battery overall composite T-score, with an adjusted mean difference of 1.98 points and a standardized effect size of 0.34 versus placebo. However, a parallel 610-patient Phase II trial in mild-to-moderate Alzheimer’s disease dementia (NCT02788513) failed to demonstrate any dose-response relationship on the ADAS-Cog11 primary endpoint. A subsequent Phase II trial combining iclepertin with computerized cognitive training (NCT03859973, n=200) also failed to meet its primary endpoint. The compound received United States Food and Drug Administration Breakthrough Therapy Designation for CIAS in May 2021. In January 2025, Boehringer Ingelheim reported that the Phase III CONNEX programme, comprising three replicate randomized controlled trials enrolling 1835 patients across 338 sites in 41 countries with 26 weeks of treatment at 10 mg once daily, failed to meet its primary or key secondary endpoints (pooled MCCB adjusted mean difference 0.127, 95 percent confidence interval negative 0.396 to 0.650, p=0.63). Iclepertin was well tolerated across all trials, with adverse event rates numerically similar to or lower than placebo. The compound is not approved in any jurisdiction.

This monograph reviews the chemistry and synthesis of iclepertin; the molecular pharmacology of GlyT1 inhibition and the NMDA receptor enhancement mechanism; the comprehensive pharmacokinetic characterization including CYP3A4 drug-drug interactions; preclinical efficacy in MK-801 deficit and social recognition models; the complete clinical evidence base across schizophrenia, Alzheimer’s disease, and cognitive training paradigms; reconstitution, sourcing, and handling considerations; adverse event and safety signals; and a comparative assessment of five alternative NMDA-enhancing or GlyT1-targeting compounds (bitopertin, sarcosine, D-serine, PF-03463275, luvadaxistat) against iclepertin on five competency standards.

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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.

May 22, 2026
LM22B-10

Our opinion on this compoundNovel, promising

58/100

Dual TrkB/TrkC small-molecule probe with impressive preclinical breadth but a contested mechanism and thin independent evidence base

Look, the neurotrophin field has needed a credible small-molecule dual TrkB/TrkC tool for a long time. Recombinant BDNF and NT-3 don’t cross the blood-brain barrier at useful concentrations, and 7,8-dihydroxyflavone activates TrkB reasonably well but ignores TrkC entirely. LM22B-10, identified by Yang, Massa, and Longo at Stanford through in silico BDNF loop-domain pharmacophore screening combined with low-throughput neuronal survival assays, is the first small molecule reported to co-activate both receptors, with TrkB EC50 of approximately 1.8 micromolar, TrkC EC50 of approximately 2.5 micromolar, and neuronal survival EC50 in the 200 to 300 nanomolar range that the discovery group claims exceeds recombinant BDNF and NT-3 individually and in combination. That’s a real pitch, and the triarylmethane scaffold is genuinely novel for this receptor class.

The preclinical breadth is the other thing that gets our attention. In R6/2 and Q140 Huntington’s disease mouse models, the compound reduced intranuclear huntingtin aggregates, attenuated medium spiny neuron degeneration, suppressed microglial activation, and improved motor performance. In a rat controlled cortical impact model, 10 mg/kg intraperitoneal reduced cortical cell death roughly 59 percent and increased hippocampal doublecortin-positive neurogenesis approximately 65 percent, with concurrent behavioral improvement. Corneal nerve regeneration in both healthy and diabetic mouse wound models via topical eye drops adds a genuinely distinct indication. The oral-bioavailability-optimized derivative PTX-BD10-2 from PharmatrophiX then showed prevention of cholinergic atrophy and restoration of hippocampal LTP in late-stage hAPPLond/Swe Alzheimer’s mice. Aging, neurodegeneration, acute neurotrauma, peripheral neuropathy: four distinct indication spaces with preclinical signal is not nothing.

Here’s the thing though: an independent validation study using microscale thermophoresis reported Kd approximately 83 micromolar at the TrkB extracellular domain and failed to induce TrkB, Akt, or ERK1/2 phosphorylation in conventional blotting assays. That directly contradicts the original characterization, and the discrepancy has not been resolved. A 2025 Journal of Medicinal Chemistry review proposed that LM22B-10 and related putative Trk agonists may function as positive allosteric modulators at the transmembrane domain rather than classical orthosteric agonists. That model might actually account for the biology better than the original story, but it means the mechanism claim the compound was built on remains formally contested.

For investigators running a TrkB/TrkC signaling program, LM22B-10 is still one of very few BBB-permeant small-molecule probes producing a dual-receptor functional effect in vivo, and resolving whether it’s orthosteric, allosteric, or something more indirect is a legitimately important open question. The bench value is real. What we don’t like: no clinical trials, no IND, no human pharmacokinetic data, and the evidence base outside the Stanford/PharmatrophiX ecosystem is thin enough that sourcing and batch-to-batch consistency become investigator problems, not vendor problems. The translational arrow is long. Dont treat the preclinical breadth as a substitute for independent replication of the core pharmacology claim first.

Novelty

75

Mechanism promise

68

In-category differentiation

70

Evidence quality

35

Translational signal

28

Research bench value

62

Rationale LM22B-10 earns its novelty marks as the first small molecule co-activating both TrkB and TrkC with BBB permeability, producing signal across aging, Huntington’s disease, TBI, corneal neuropathy, and an AD derivative model; however, a failed independent validation at 83 micromolar Kd and a 2025 JMedChem reinterpretation of its mechanism as transmembrane allosteric rather than orthosteric represent unresolved liabilities that meaningfully compress evidence quality and translational confidence.

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

Non-peptide triarylmethane small-molecule TrkB/TrkC neurotrophin receptor co-activator

A triarylmethane neurotrophin mimetic identified through in silico screening of BDNF loop-domain pharmacophores, distinguished as the first small molecule to co-activate TrkB and TrkC receptors with preclinical efficacy across aging, Alzheimer’s disease, Huntington’s disease, traumatic brain injury, and corneal neuropathy models.

Abstract

LM22B-10 (CAS 342777-54-2) is a non-peptide, blood-brain barrier permeant, triarylmethane small molecule that co-activates tropomyosin-related kinase B (TrkB) and tropomyosin-related kinase C (TrkC) neurotrophin receptors. It was identified by Yang, Massa, and Longo at Stanford University through in silico screening with a brain-derived neurotrophic factor (BDNF) loop-domain pharmacophore, coupled with low-throughput neuronal survival screening, and was first reported in Neuropharmacology in 2016. LM22B-10 is distinguished from prior small-molecule Trk ligands, which typically activate a single receptor subtype, by its dual activation of TrkB (EC50 approximately 1.8 micromolar) and TrkC (EC50 approximately 2.5 micromolar), producing neurotrophic activity with an EC50 for neuronal survival of 200 to 300 nanomolar that exceeds the effects of recombinant BDNF and neurotrophin-3 (NT-3), individually and in combination, in hippocampal neuronal assays. The compound selectively activates TrkB and TrkC without engaging TrkA, and drives downstream Akt and ERK1/2 signaling in vitro and in vivo. Preclinical studies in aged mice demonstrated that LM22B-10 activates hippocampal and striatal TrkB and TrkC signaling, increases dendritic spine density, and supports neuronal integrity. In mouse models of Huntington’s disease (R6/2 and Q140), the compound reduced intranuclear huntingtin aggregates, dendritic spine loss, microglial activation, and degeneration of medium spiny neurons while improving motor performance. In a rat controlled cortical impact model of traumatic brain injury, LM22B-10 at 10 mg/kg intraperitoneal reduced cortical cell death by approximately 59 percent and increased hippocampal doublecortin-positive neurogenesis by approximately 65 percent, with concurrent improvement in spatial memory and anxiety-related behavior in injured animals. The compound has also demonstrated corneal nerve regeneration in both healthy and diabetic mouse wound models when delivered as topical eye drops. A derivative, PTX-BD10-2, was developed by PharmatrophiX with improved oral bioavailability and has demonstrated prevention of cholinergic neuron atrophy, restoration of hippocampal long-term potentiation, and normalization of synaptic function in late-stage Alzheimer’s disease mouse models (hAPPLond/Swe) following chronic oral dosing. The mechanism of TrkB/TrkC activation by LM22B-10 is not without controversy. An independent validation study using microscale thermophoresis reported weak binding to the TrkB extracellular domain (Kd approximately 83 micromolar) and failure to induce TrkB, Akt, or ERK1/2 phosphorylation in conventional blotting assays, results that contrast with the original characterization. A 2025 review in the Journal of Medicinal Chemistry proposed that LM22B-10 and related putative Trk agonists may function as positive allosteric modulators binding the transmembrane domain rather than as classical orthosteric agonists. The discrepancy remains unresolved and constitutes a significant open question in the field. LM22B-10 has not entered clinical trials; it remains a preclinical research tool. This monograph reviews the chemistry, dual-receptor pharmacology, preclinical evidence base across disease models, the mechanistic controversy, sourcing and handling considerations, and a comparative assessment of five neurotrophin receptor ligands against LM22B-10 on five competency standards.

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-1640Open 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 22, 2026

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