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Category: Uncategorized

TRV045

Our opinion on this compoundNovel, promising

65/100

Genuinely differentiated S1P1R agonist with clean Phase 1 data, awaiting Phase 2 proof in patients

Look, the S1P receptor space has been dominated by a single pharmacological idea since fingolimod hit the market in 2010: functional antagonism through receptor internalization. Every approved S1P modulator works by trapping lymphocytes in lymph nodes, which is great for MS and catastrophic for almost every other indication you might want to explore. TRV045 is Trevena’s answer to that constraint, and the mechanism is actually interesting enough to pay attention to.

The core claim is that TRV045 produces sustained S1P1R agonism without triggering receptor internalization, downregulation, or functional desensitization. If that holds, and the preclinical evidence says it does, you get CNS-active S1P1R engagement with no lymphopenia, no first-dose bradycardia, and no atrioventricular conduction drama. Trevena ran fingolimod head-to-head in a CIPN model and showed roughly 70 percent reduction in S1P1R functional activity for fingolimod versus sustained activity for TRV045 over the same 14-day dosing window. Thats a meaningful mechanistic contrast, not marketing language. The epilepsy signal through the NIH ETSP is a bonus: pentylenetetrazol threshold and maximal electroshock data at 18 mg/kg ED50 in rats put it in credible anticonvulsant territory, and the NIH doesn’t collaborate on this screening program with compounds that don’t clear a real bar.

What we like here is the Phase 1 execution. Three completed studies, 89 healthy volunteers in the first-in-human ascending dose work, then 25 subjects each in a PainCart capsaicin model and a TMS/EEG cortical engagement study. The capsaicin allodynia reduction at 150 and 300 mg was statistically significant and dose-dependent. The EEG power spectral density shifts across alpha, beta, and gamma after four days of 250 mg daily dosing are consistent with real CNS target engagement. No serious adverse events, no lymphopenia, no bradycardia across all three studies. The tolerability story is genuinely cleaner than any approved S1P modulator.

What we don’t like is the gap that remains. PainCart results in healthy volunteers are encouraging but dont tell you what happens in a 58-year-old with ten years of diabetic neuropathy. Phase 2 hasn’t started. The disease-modifying signal from the 100 mg/kg prevention paradigm in rodents is intriguing but very preliminary. The dual indication strategy (pain plus epilepsy) is smart if resources allow it, risky if they don’t. Trevena is a mid-size specialty pharma; the execution risk is real. As a bench tool, TRV045 is valuable precisely because it lets investigators dissect S1P1R CNS pharmacology without the lymphopenia confound that has limited mechanistic work with the approved class. That’s a genuine contribution to the research toolkit regardless of how the Phase 2 eventually reads out.

Honestly, 65 feels right here. The mechanism differentiation and Phase 1 readout are stronger than most compounds at this stage; the absence of Phase 2 patient data keeps it from claiming the scores the GLP-1 class earns. Watch the Phase 2 design closely when it’s announced.

Novelty

72

Mechanism promise

74

In-category differentiation

76

Evidence quality

45

Translational signal

48

Research bench value

62

Rationale TRV045 earns its scores primarily on differentiation and mechanism: sustained S1P1R agonism without desensitization or lymphopenia is a real pharmacological break from the fingolimod class, and three completed Phase 1 studies with positive target engagement in both a capsaicin pain model and TMS/EEG cortical excitability readout give it genuine early human signal. Evidence and translational scores are held back because no Phase 2 efficacy data exist in actual patient populations yet, and the gap between PainCart results in healthy volunteers and durable analgesia in diabetic neuropathy patients is non-trivial.

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

Selective sphingosine-1-phosphate subtype 1 receptor (S1P1R) agonist with sustained signaling and absence of receptor desensitization or lymphocyte sequestration

A selective S1P1 receptor agonist developed by Trevena as a non-opioid treatment for diabetic neuropathic pain, distinguished from fingolimod-class functional antagonists by sustained receptor activation without S1P1R desensitization, protein downregulation, or peripheral lymphocyte depletion, and with additional preclinical evidence for anti-seizure activity.

Abstract

TRV045 (CAS 2256030-24-5) is a novel, orally bioavailable, selective sphingosine-1-phosphate subtype 1 receptor (S1P1R) agonist under clinical development by Trevena, Inc. as a potential non-opioid treatment for acute and chronic neuropathic pain secondary to diabetic peripheral neuropathy and, through a collaboration with the National Institutes of Health, as a potential treatment for epilepsy. The compound is distinguished from the approved S1P receptor modulator class (fingolimod, siponimod, ozanimod, ponesimod) by a pharmacological mechanism that produces sustained S1P1R agonism without the receptor internalization, functional desensitization, or S1P1R protein downregulation that characterizes fingolimod and related agents. The practical consequence of this mechanistic differentiation is the absence of peripheral lymphocyte sequestration (lymphopenia), the absence of first-dose bradycardia and atrioventricular conduction delay, and the absence of the immunosuppressive liability that defines the approved S1P modulator class and limits its application outside multiple sclerosis. In preclinical models of diabetic peripheral neuropathy and chemotherapy-induced peripheral neuropathy (CIPN), oral TRV045 at 1 to 10 mg/kg produced dose-dependent reversal of mechanical allodynia, cold allodynia, and thermal hyperalgesia. Effects were sustained over 14 days of repeated dosing without evidence of tolerance, receptor desensitization, or S1P1R protein reduction in spinal cord tissue. In contrast, fingolimod in the same CIPN model produced approximately 70 percent reduction in S1P1R functional activity and 30 percent protein reduction. At higher doses (100 mg/kg) in a prevention paradigm, TRV045 reduced both mechanical and cold hypersensitivity 24 hours after the final dose, with cold hypersensitivity reduction persisting seven days after treatment cessation, suggesting potential disease-modifying activity. In epilepsy models conducted through the NIH-supported Epilepsy Therapy Screening Program (ETSP), TRV045 at 30 mg/kg significantly increased time to myoclonic twitch in the pentylenetetrazol seizure threshold test and produced dose-dependent protection in the maximal electroshock seizure test with an ED50 of 18 mg/kg in rats. In human Phase 1 clinical studies, TRV045 has been evaluated in three completed trials comprising a first-in-human single and multiple ascending dose study in 89 healthy volunteers, a target engagement proof-of-concept study using the capsaicin-induced pain (PainCart) model in 25 healthy subjects, and a transcranial magnetic stimulation (TMS) and electroencephalography (EEG) proof-of-concept study in 25 healthy male subjects. The target engagement study demonstrated statistically significant, dose-dependent reduction in capsaicin-induced mechanical allodynia at 150 mg and 300 mg single doses compared to placebo. The TMS/EEG study demonstrated statistically significant increases in alpha, beta, and gamma frequency band power spectral density after four days of 250 mg daily dosing, consistent with central nervous system target engagement and modulation of cortical excitability. Across all three completed Phase 1 studies, TRV045 demonstrated a favorable tolerability profile with no serious adverse events, no drug-related discontinuations, no clinically significant lymphopenia, no bradycardia, no blood pressure changes, and no prolongation of QTcF or PR intervals. The most common adverse events were mild headache, somnolence, dizziness, and fatigue. Trevena is advancing an optimized oral formulation through clinical pharmacokinetic evaluation in preparation for Phase 2 development. TRV045 is an investigational compound not approved by the United States Food and Drug Administration. This monograph reviews the chemistry and identification of TRV045; the S1P1R agonist mechanism of action and its differentiation from functional antagonist S1P modulators; the preclinical pharmacology in neuropathic pain and epilepsy models; the Phase 1 clinical evidence base; sourcing and quality verification; reconstitution and handling; stack interaction considerations; adverse events and safety; and a comparative assessment of five S1P receptor modulators (fingolimod, siponimod, ozanimod, ponesimod, amiselimod) against TRV045 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 20, 2026
Aminotadalafil

Our opinion on this compoundLow merit

14/100

Forensic adulterant reference with no independent research program or novel mechanism

Look, aminotadalafil exists in the biomedical literature for one reason: someone found it in a supplement that was supposed to be herbal, and analytical labs needed a reference standard to confirm the hit. Thats not a research program. That’s a forensic problem, and treating it as the former because the latter requires it is a mistake worth naming explicitly.

The structural story is as simple as it gets. Swap the N-methyl on tadalafil’s piperazinedione ring for a primary amine and you have aminotadalafil. One functional group change. The beta-carboline scaffold is intact, PDE5 active-site recognition is preserved, and cross-reactivity with anti-tadalafil polyclonal antibodies runs above 100 percent. So yes, it almost certainly inhibits PDE5. We already knew that from the class. There is no new mechanism here, no dual-target angle, no allosteric surprise waiting to be characterized. PDE5 inhibition is about as mature a mechanism as phosphodiesterase biology gets: sildenafil, tadalafil, vardenafil, and avanafil have been in clinical use for decades, the crystal structures are solved, selectivity profiles are mapped across the PDE superfamily, and the downstream cGMP-nitric oxide pathway is textbook. Aminotadalafil contributes nothing to that picture.

What makes this compound genuinely uninteresting as a research candidate is the evidence situation. There is no formal pharmacokinetic characterization. No rodent toxicology package. No human pharmacology trial of any kind. The closest thing to translational data is an adverse event corpus drawn from people who consumed adulterated supplements without knowing it, which isnt a controlled exposure arm by any stretch. You cant extract clean pharmacology from that. The differentiation case is equally grim: if you need a PDE5 inhibitor for bench work, tadalafil is commercially available, comes with established handling protocols, and carries decades of selectivity data. Aminotadalafil is, by every research metric, inferior to its own parent. Strictly so.

We think the only legitimate use case here is as a certified reference material for regulatory or analytical chemistry labs running supplement screening panels. That work matters, it’s genuinely important for consumer safety, but it isnt what a research compound library is built to support. The library is for compounds that give investigators new angles on a biological question. Aminotadalafil doesn’t do that. It’s a known adulterant, a forensic footnote, and a reminder that the supplement industry operates a shadow pharmacopoeia with no clinical trial infrastructure behind it. A bench scientist looking for a PDE5 probe should reach for tadalafil without hesitation. A lab building a supplement adulterant detection panel should source aminotadalafil as a reference standard. Those are different jobs, and this compound belongs only in the second.

Novelty

18

Mechanism promise

15

In-category differentiation

8

Evidence quality

12

Translational signal

10

Research bench value

22

Rationale Aminotadalafil appears in the literature almost exclusively as a dietary supplement adulterant flagged by regulatory enforcement labs; PDE5 inhibition is a fully saturated mechanism with multiple approved parent compounds, and the complete absence of formal pharmacology data leaves this analog with near-zero bench value except as an analytical reference standard for detection assays.

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

Synthetic phosphodiesterase type 5 (PDE5) inhibitor analog; tadalafil N-methyl-to-amino substituted derivative

A synthetic structural analog of tadalafil in which the piperazinedione N-methyl group is replaced by a primary amine, yielding an unapproved phosphodiesterase type 5 inhibitor principally encountered as an undeclared adulterant in dietary supplements marketed for erectile dysfunction.

Abstract

Aminotadalafil, formally (6R,12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione (CAS 385769-84-6), is a synthetic structural analog of tadalafil, the selective cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) inhibitor marketed as Cialis for the treatment of erectile dysfunction, pulmonary arterial hypertension, and benign prostatic hyperplasia. The single structural modification that distinguishes aminotadalafil from the parent drug is the replacement of the N-methyl substituent on the 2-position of the piperazinedione (diketopiperazine) ring with a primary amino group (NH2), a change that alters hydrogen-bonding capacity, basicity, and physicochemical properties while preserving the core beta-carboline-fused diketopiperazine scaffold responsible for PDE5 active-site recognition. Aminotadalafil retains inhibitory activity at PDE5 and exhibits greater than 100 percent cross-reactivity with anti-tadalafil polyclonal antibodies, confirming close structural and immunochemical homology with the parent compound [1]. The compound has not undergone formal preclinical toxicology, human pharmacokinetic characterization, or clinical efficacy evaluation in any regulatory jurisdiction, and it is not approved for human use by any national medicines authority. Its principal significance in the biomedical literature arises from its repeated identification as an undeclared adulterant in dietary supplements, herbal products, and electronic cigarette liquids marketed for sexual enhancement, where it poses uncharacterized risks to consumers who are unaware of its presence and who may be concurrently taking nitrate-containing medications or other agents that interact with the cGMP-nitric oxide signaling pathway [2, 3, 4, 5].

The analytical chemistry literature on aminotadalafil is substantial. The compound has been identified and structurally characterized by proton and carbon-13 nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, Fourier transform infrared spectroscopy, and ultraviolet spectrophotometry in dietary supplement matrices across multiple continents, including reports from Latin America, Asia, Europe, and North America [2, 6, 7]. Validated high-performance liquid chromatography with diode array detection (HPLC-DAD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods permit simultaneous identification and quantification of aminotadalafil alongside other PDE5 inhibitor analogs (hydroxythiohomosildenafil, thiosildenafil, dimethylsildenafil, thiodimethylsildenafil) in complex supplement matrices [3, 8]. A dimeric interaction product of aminotadalafil has also been isolated from adulterated health food products, suggesting that the compound undergoes degradation or condensation reactions under storage conditions encountered in supplement manufacture [9].

The pharmacological characterization of aminotadalafil is limited. No peer-reviewed study has reported a direct IC50 determination for aminotadalafil against recombinant human PDE5, and no selectivity panel across the eleven mammalian phosphodiesterase families has been published. The compound’s activity is inferred from its structural homology to tadalafil (IC50 approximately 1.8 to 5.0 nanomolar against PDE5) and from the immunochemical cross-reactivity data. Structure-activity relationship studies of the broader tadalafil analog series indicate that modifications at the 2-position of the diketopiperazine ring modulate PDE5 affinity, and that the (6R,12aR) stereochemistry derived from L-tryptophan is essential for potent inhibition [10, 11]. Aminotadalafil preserves this stereochemistry. No human pharmacokinetic, dose-response, or safety data exist; toxicological risk assessment must therefore rely on extrapolation from tadalafil and on the general pharmacology of the PDE5 inhibitor class. This monograph reviews the chemistry, structural pharmacology, inferred pharmacokinetics, regulatory history, detection methodology, sourcing considerations, and comparative assessment of aminotadalafil against five alternative PDE5 inhibitor analogs encountered in the adulterated supplement landscape.

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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 15, 2026
NSI-189

Plain-language summaryIntrigue 45 / 100

NSI-189 is a small molecule developed at Neuralstem to stimulate hippocampal neurogenesis (the birth of new neurons in the dentate gyrus). Preclinical rodent studies showed proliferation of neural progenitor cells, hippocampal volume increase, and antidepressant-like behavior in chronic stress models, generating considerable hope that this could be a fundamentally new class of antidepressant. Phase 1 trials were uneventful. Phase 2 trials in major depression in 2014 and 2017 failed to beat placebo on the primary endpoints, and Neuralstem ended development. It briefly became popular in nootropic communities sourced as a research chemical, on the strength of secondary cognitive endpoints in the failed trials. The clinical case is essentially closed. 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 compoundNovel, promising

63/100

First-in-class neurogenic small molecule with compelling biology but a Phase 2 primary miss that tempers enthusiasm

Look, the discovery story here is legitimately compelling. Karl Johe’s team at Neuralstem screened roughly 10,000 compounds directly against human hippocampal neural stem cells and pulled out something that hit no known receptor, no transporter, no kinase panel in the standard pharmacology sweep. A compound that’s clean across 52 neurotransmitter targets and 900 kinases and still produces dose-dependent hippocampal volume increases up to 66 percent in rodents is not a me-too. Thats a real signal, and it earns attention.

The mechanism promise is the strongest thing NSI-189 has going for it. Adult hippocampal neurogenesis as a lever for depression isn’t new as a hypothesis, but NSI-189 is the first small molecule to pursue it directly as the primary mode of action in clinical development. The anatomical specificity matters: the morphological effects are confined to the dentate gyrus and subventricular zone, not a blunt neurotrophic push across the whole brain. Downstream TrkB/Akt activation, BDNF upregulation alongside SCF, GDNF, and VEGF gives investigators tractable pathway targets to interrogate. The bell-shaped dose-response relationship in preclinical work (30 mg/kg outperforming 100 mg/kg) is either an interesting biology clue or a translation headache, probably both.

Here’s the thing, though: the Phase 2 trial (Papakostas et al. 2020) missed its primary endpoint. MADRS reduction hit p=0.063 – trending, not significant. The Phase 1b data from Fava et al. 2016 was more encouraging, and sub-population signal in the Phase 2 secondary analyses kept Alto Neuroscience interested enough to run a Phase 2b as ALTO-100, but those results aren’t in yet. A compound thats been in development since roughly 2010 without hitting approval is on a slow clock. We dont know yet whether patient selection refinement will rescue the clinical story or whether the preclinical-to-human translation gap is just wide.

What we like: NSI-189 is the best probe we have for studying direct hippocampal neurogenesis stimulation in living subjects. There is no alternative compound for that specific question. If your research program touches neurogenesis biology, BDNF pathway pharmacology, or hippocampal volume as a functional biomarker, NSI-189 belongs on the bench for exactly that reason.

What we dont like: the evidence base is thinner than the mechanism press suggests. Small Ns across all trials, one primary miss, and preclinical dose-response complexity that makes rational human dosing genuinely hard to reason about. The translational arrow exists but its uncertain. Net view: first-in-class mechanism, real but unresolved human signal, indispensable as a tool for serious neurogenesis research right now.

Novelty

72

Mechanism promise

78

In-category differentiation

72

Evidence quality

42

Translational signal

38

Research bench value

62

Rationale NSI-189 scores high on novelty and mechanism because its phenotypic discovery yielded something genuinely unlike any marketed antidepressant: zero activity at 52 standard targets, 900 kinases, and all monoamine transporters, with direct hippocampal neurogenesis stimulation as the primary mode of action. Evidence and translational scores are pulled down by the Phase 2 primary endpoint miss (Papakostas et al. 2020, p=0.063 on MADRS) and uniformly small clinical Ns, while bench value stays solid because NSI-189 is the only direct hippocampal neurogenesis probe available for human research programs.

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

Benzylpiperazine-aminopyridine neurogenic compound with indirect brain-derived neurotrophic factor modulation and hippocampal neurogenesis stimulation

A first-in-class small molecule neurogenic agent discovered through phenotypic screening of human hippocampal neural stem cells, developed for major depressive disorder and under investigation for cognitive impairment, diabetic neuropathy, and post-traumatic stress disorder.

Abstract

NSI-189 (amdiglurax; ALTO-100) is a benzylpiperazine-aminopyridine small molecule identified through a phenotypic screen of approximately 10,000 compounds against human hippocampal neural stem cells and advanced as a first-in-class hippocampal neurogenesis stimulator for the treatment of major depressive disorder (MDD). The compound was discovered by Karl Johe and colleagues at Neuralstem, Inc. (Germantown, Maryland) and is now under development by Alto Neuroscience (Mountain View, California) under the designation ALTO-100. NSI-189 is mechanistically distinct from all marketed antidepressants: it has no detectable activity at serotonin, norepinephrine, or dopamine transporters, no binding at 52 standard neurotransmitter receptor and ion channel targets, and no activity across a panel of 900 kinases. Instead, the compound stimulates proliferation and neurogenic differentiation of hippocampal neural stem cells in vitro with low-micromolar potency and, on oral administration to rodents at 10 to 30 mg/kg/day, produces dose-dependent increases in hippocampal volume (up to 66 percent at 30 mg/kg in mice), upregulation of brain-derived neurotrophic factor (BDNF), stem cell factor (SCF), glial cell line-derived neurotrophic factor (GDNF), and vascular endothelial growth factor (VEGF), and activation of the TrkB/Akt signaling pathway. The morphological effects are confined to the dentate gyrus of the hippocampus and the subventricular zone; no structural changes have been observed elsewhere in the brain. A bell-shaped dose-response relationship is observed in preclinical hippocampal volume endpoints, with 100 mg/kg producing less effect than 30 mg/kg, suggesting an optimal range for neurogenic stimulation.

Clinical development has proceeded through Phase 1 (41 healthy volunteers, 2011), Phase 1b (24 MDD patients, Fava et al. 2016, published in Molecular Psychiatry), and Phase 2 (220 MDD outpatients, Papakostas et al. 2020, published in Molecular Psychiatry). The Phase 1b trial demonstrated safety and tolerability at 40, 80, and 120 mg daily for 28 days, with medium-to-large effect sizes on the Symptoms of Depression Questionnaire (SDQ) and the Cognitive and Physical Functioning Questionnaire (CPFQ). The Phase 2 trial, conducted using a sequential-parallel comparison design across 12 weeks, did not meet its primary endpoint (change from baseline on the Montgomery-Asberg Depression Rating Scale, MADRS) at either 40 mg or 80 mg daily. However, 40 mg daily produced statistically significant improvements on the SDQ (pooled mean difference -8.2; Cohen’s d = -0.64 in Stage 2; p = 0.04), the CPFQ (pooled mean difference -1.9; p = 0.03), and several objective cognitive measures on the CogScreen battery (Cohen’s d ranging from 0.12 to 1.12 for significant measures). Hippocampal volume was not significantly changed in MDD patients at the studied doses and duration, despite the robust preclinical volumetric signal.

Alto Neuroscience acquired the NSI-189 program in October 2021 and redesignated the compound ALTO-100. A Phase 2b trial (301 adults with MDD, 34 U.S. sites, 6 weeks, biomarker-enriched design using a cognitive memory test) reported topline results in 2024: ALTO-100 did not demonstrate statistically significant improvement in MADRS versus placebo in the biomarker-defined population and did not meet secondary endpoints. The compound was well tolerated, with headache, nausea, and abnormal dreams as the most common adverse events at rates similar to placebo. A Phase 2b trial in bipolar depression is expected to report in 2026, and the compound remains under investigation for post-traumatic stress disorder.

Preclinical pharmacology extends beyond depression. NSI-189 reverses cognitive and motor deficits in a rat model of ischemic stroke (30 mg/kg oral), ameliorates central and peripheral neuropathy in mouse models of type 1 and type 2 diabetes (10 to 30 mg/kg oral), enhances synaptic plasticity and reverses motor and cognitive impairments in a mouse model of Angelman syndrome through TrkB/Akt pathway activation, and enhances long-term potentiation in hippocampal slice preparations in vitro. The compound has linear pharmacokinetics across the 40 to 120 mg/day clinical dose range, an oral Tmax of 1 to 2 hours, a plasma elimination half-life of 17.4 to 20.5 hours supporting once-daily dosing, and achieves steady state within 4 to 5 days.

This monograph reviews the chemical identity and synthesis of NSI-189; the discovery through phenotypic screening; the molecular pharmacology and neurotrophic factor cascade; the comprehensive pharmacokinetic profile; the preclinical evidence base across depression, stroke, neuropathy, and Angelman syndrome models; the clinical evidence base from Phase 1 through Phase 2b; sourcing, reconstitution, and handling considerations; stack interactions; the adverse-event and safety signal; and a structured comparative assessment of five neurogenesis-associated compounds (fluoxetine, ketamine, agomelatine, psilocybin, and 7,8-dihydroxyflavone) against NSI-189 on five competency standards. The compound is not approved by any regulatory authority for any indication. It is sold 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 15, 2026
Anadrol

Our opinion on this compoundEstablished workhorse

43/100

Old-school oral AAS with genuine erythropoietic credentials and unresolved mechanistic puzzles that haven’t drawn fresh research attention

Look, Anadrol is about as old as the Syntex steroid chemistry program that produced it. Ringold and colleagues synthesized oxymetholone in 1959, the FDA approved it for refractory anemias in the early 1960s, and the compound has occupied a narrow but legitimate pharmacopeia slot ever since. That history isnt disqualifying on its own, but it does mean the interesting questions about this molecule have had six decades to be answered, and most of them have been.

The erythropoietic story is the strongest part of the dossier. Urinary erythropoietin levels elevated fivefold at therapeutic doses is a real, documented effect, not marketing copy. The Hengge et al. 2003 Phase III trial in HIV-associated wasting is a clean piece of evidence, 3.0 to 3.5 kg weight gain over 16 weeks at 100 to 150 mg daily, placebo-controlled, adequate N. FDA approval for aplastic anemia, congenital aplastic anemia, and myelofibrosis reflects genuine clinical utility. On translational signal and evidence quality, this compound has receipts that most peptides in the Kodiac library would envy. Those scores pull the overall up.

What keeps the overall modest is layered. Novelty is essentially zero for a researcher entering the field in 2026. There’s no unexplored corner of oxymetholone pharmacology that hasn’t had someone’s career spent on it. The mechanism is interesting in a “this shouldn’t work this way but it does” sense: the compound shows negligible direct androgen receptor binding affinity in competitive displacement assays, yet produces potent anabolic activity; and it causes estrogenic effects despite structural inability to aromatize, possibly through direct ER-alpha activation. Those are genuinely puzzling phenomena. The problem is they’ve been puzzling researchers since the 1970s without producing a tidy resolution, and systematically applying modern receptor pharmacology tools to oxymetholone isn’t a priority grant target for anyone right now.

The hepatotoxicity profile is the sharpest practical constraint. The 17-alpha-alkylation that delivers oral bioavailability also makes oxymetholone one of the more aggressive hepatotoxins in the oral AAS class. Peliosis hepatis, cholestatic jaundice, hepatocellular carcinoma with prolonged use, these arent theoretical flags, they’re documented in the clinical record with case fatalities. For bench work, that safety profile narrows the experimental window considerably and complicates study design at any meaningful dose range.

Differentiation is weak in 2026. For erythropoiesis research, recombinant EPO and darbepoetin offer better mechanistic specificity and cleaner profiles. For muscle wasting and anabolic biology, oxandrolone covers similar clinical ground with substantially lower hepatotoxic liability and comparable clinical evidence. Anadrol lands in an awkward position: potent but not clean, old but not fully understood, approved but barely used. The non-aromatizing estrogenicity question is the one thread genuinely worth pulling if that specific mechanism is your program. Otherwise, better-targeted probes exist for every question this compound could credibly answer.

Novelty

22

Mechanism promise

38

In-category differentiation

40

Evidence quality

62

Translational signal

63

Research bench value

40

Rationale Oxymetholone is a 1959-vintage oral AAS with real FDA-backed clinical evidence in aplastic anemia and HIV wasting, but near-zero novelty for a researcher entering today; the paradoxical non-aromatizing estrogenicity and low AR binding despite high anabolic potency are genuinely unresolved mechanistic puzzles, but they’ve been sitting unanswered since the 1970s, and the aggressive 17-alpha-alkylation hepatotoxicity profile narrows bench applicability considerably.

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

17-alpha-alkylated anabolic-androgenic steroid; synthetic dihydrotestosterone derivative with potent erythropoietic and anabolic activity

A 17-alpha-alkylated oral anabolic-androgenic steroid derived from dihydrotestosterone, developed at Syntex in the late 1950s for the treatment of anemias characterized by deficient red blood cell production, distinguished by potent erythropoietic stimulation, marked nitrogen retention, and significant hepatotoxic liability.

Abstract

Oxymetholone, marketed as Anadrol-50 (Syntex, later Unimed Pharmaceuticals, now Alaven Pharmaceutical) and Anapolon (Imperial Chemical Industries and generics), is a synthetic 17-alpha-alkylated derivative of dihydrotestosterone first described by Ringold et al. at Syntex in 1959 and introduced into clinical medicine in the early 1960s for the treatment of anemias, osteoporosis, and catabolic wasting states. The compound is the 2-hydroxymethylene analog of 17-alpha-methyl-dihydrotestosterone (mestanolone), bearing an unusual hydroxymethylene substituent at the C2 position that confers oral bioavailability through resistance to first-pass hepatic inactivation and that can be metabolically cleaved to yield mestanolone as an active metabolite. Oxymetholone is one of the most potent oral anabolic-androgenic steroids in clinical use, exhibiting a high ratio of anabolic to androgenic activity in classical levator ani and ventral prostate bioassays while paradoxically demonstrating low direct binding affinity for the androgen receptor in competitive displacement studies. The principal pharmacodynamic effects are stimulation of erythropoiesis through increased renal erythropoietin production (with urinary erythropoietin levels elevated up to fivefold at therapeutic doses), promotion of positive nitrogen balance and skeletal muscle protein synthesis, and a poorly characterized but clinically significant estrogenic activity that occurs despite the compound’s structural inability to undergo aromatization, possibly through direct activation of estrogen receptor alpha. The compound received approval from the United States Food and Drug Administration for the treatment of anemias caused by deficient red blood cell production, including acquired aplastic anemia, congenital aplastic anemia, myelofibrosis, and hypoplastic anemias due to the administration of myelotoxic drugs. In the mid-1970s, the FDA restricted the approved indication exclusively to anemias characterized by deficient erythropoiesis, withdrawing prior approvals for osteoporosis and general catabolic states. Clinical investigation has subsequently extended to HIV/AIDS-associated wasting (Hengge et al. 2003 Phase III trial demonstrating 3.0 to 3.5 kg weight gain over 16 weeks at 100 to 150 mg daily), antithrombin III deficiency, and pediatric growth failure, with varying degrees of success. The hepatotoxic liability of the 17-alpha-alkylated structure is the principal safety concern: cholestatic jaundice occurs in approximately 1 percent of treated patients, typically within 1 to 4 months of initiation; peliosis hepatis (blood-filled sinusoidal cysts) develops with prolonged administration and has resulted in fatal hepatic rupture and hemorrhage in case reports; and hepatocellular carcinoma and hepatic adenoma have been reported after 2 to 15 years of continuous use, predominantly in patients with Fanconi anemia and aplastic anemia receiving chronic androgen therapy. The compound is classified as a Schedule III controlled substance in the United States under the Controlled Substances Act and is subject to equivalent regulatory controls in most jurisdictions. This monograph reviews the chemistry, synthesis, and structure-activity relationships of oxymetholone; the androgen receptor, erythropoietic, and estrogenic pharmacology; the limited but clinically relevant pharmacokinetic record; the preclinical pharmacology in animal models of anemia and wasting; the clinical evidence base across anemia, HIV wasting, and ancillary indications; sourcing and quality verification for research applications; reconstitution and handling; stack interactions and combinations with other anabolic and therapeutic agents; the adverse-event and safety signal including detailed hepatotoxicity characterization; and a comparative assessment of five alternative anabolic-androgenic agents (oxandrolone, nandrolone decanoate, stanozolol, testosterone enanthate, danazol) against oxymetholone 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 15, 2026
CE-123

Our opinion on this compoundSingle-lab provenance

47/100

Genuinely novel DAT-selective modafinil analogue with strong probe value but single-lab evidence and no human data

Look, CE-123 is one of those compounds where the chemistry is genuinely clever and the preclinical story is compelling, but the evidence base is so narrow it should give serious investigators pause before committing real resources to it.

The structural innovation is real. By replacing the acetamide sidechain of modafinil with a thiazole bioisostere, the Lubec group at Vienna achieved approximately 30-fold selectivity for the dopamine transporter over the norepinephrine transporter, compared to the essentially nonselective profile of the parent compound. That selectivity matters if you’re trying to ask clean mechanistic questions about dopaminergic cognition. You get less adrenergic noise, more interpretable data. The five-fold improvement in unbound brain-to-plasma ratio (Kp,uu,brain 0.5 versus 0.1 for R-modafinil) is a genuine PK win for CNS penetration, not a marginal difference.

The atypical inhibitor mechanism deserves real credit. CE-123 locks the outward-facing conformation of DAT without triggering reverse transport or vesicular release, which separates it cleanly from substrate-type releasers and places it in the same mechanistic class that makes modafinil theoretically lower-risk than amphetamine. For investigators trying to dissect the dopaminergic basis of cognitive flexibility or motivation, this is a cleaner tool than GBR 12909 or methylphenidate if you need to minimize adrenergic confounds.

Here’s the thing though: virtually everything we know about CE-123 comes from one research group. The Lubec laboratory has systematically extended the preclinical profile from 2017 through 2024, covering spatial memory, cognitive flexibility, aged rats, maternal separation stress, and fetal alcohol spectrum disorder models. That breadth is impressive for a single academic group. But its also the entire evidence base. No independent replication, no multi-site preclinical studies, and the clinical section exists in name only because there are no human data.

The 9.3-fold faster hepatic clearance relative to modafinil, mediated through CYP2C19, CYP3A, and CYP2B6, is worth flagging separately. Rapid metabolism may complicate translational pharmacology and introduces metabolite characterization obligations that haven’t been fully resolved. M1, formed by aromatic hydroxylation, is the principal metabolite, but the downstream activity profile is not well characterized.

What we like about CE-123 is its selectivity profile and its utility as a DAT probe for cognition research where noradrenergic contributions need to be controlled. What we dont like is that the Lubec group is essentially the sole voice in the room, and the compound has not crossed into human biology in any form. The score reflects a research tool with genuine novelty that simply hasnt earned broader trust through independent validation yet.

Novelty

58

Mechanism promise

60

In-category differentiation

55

Evidence quality

25

Translational signal

18

Research bench value

58

Rationale CE-123 achieves real pharmacological distinction from modafinil via thiazole bioisosterism and meaningful 30-fold DAT/NET selectivity, and the atypical inhibitor mechanism gives it genuine bench utility. However, the entire preclinical evidence base derives from the Lubec group at the University of Vienna with no independent replication, no multi-site confirmation, and a clinical section that is essentially empty, anchoring this firmly in single-lab-only territory despite the compound’s structural and mechanistic interest.

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

Atypical selective dopamine transporter inhibitor; modafinil analogue with thiazole bioisosteric replacement

A benzhydrylsulfinylmethylthiazole developed at the University of Vienna as a next-generation modafinil analogue, distinguished from the parent compound by approximately 30-fold selectivity for the dopamine transporter over the norepinephrine transporter, five-fold superior blood-brain barrier penetration, and a preclinical cognitive enhancement profile spanning memory acquisition, cognitive flexibility, motivation, and social cognition in rodent models of aging, early-life stress, and fetal alcohol spectrum disorders.

Abstract

CE-123 (5-((benzhydrylsulfinyl)methyl)thiazole; CAS 1879038-73-9) is a synthetic modafinil analogue and atypical dopamine transporter (DAT) inhibitor developed at the Department of Pharmaceutical Chemistry, University of Vienna, under the direction of Gert Lubec as part of a structure-activity exploration of heterocyclic diphenylmethylsulfinyl derivatives designed to achieve higher selectivity and affinity at the dopamine transporter than the parent compound modafinil. The active enantiomer, (S)-CE-123, inhibits DAT-mediated dopamine reuptake with an EC50 of approximately 2.76 micromolar in HEK293 cells stably expressing human DAT, with approximately 30-fold selectivity over the norepinephrine transporter (NET) and greater than 400-fold selectivity over the serotonin transporter (SERT). The compound interacts with the outward-facing conformation of DAT to block substrate access without triggering reverse transport or vesicular release, a mechanism that defines the atypical DAT inhibitor class and is associated with lower abuse liability than substrate-type releasers such as amphetamine. Pharmacokinetic characterization in Sprague-Dawley rats demonstrates that (S)-CE-123 achieves an unbound brain-to-plasma concentration ratio (Kp,uu,brain) of 0.5, compared to 0.1 for R-modafinil, indicating approximately five-fold superior blood-brain barrier penetration. Hepatic metabolism proceeds via CYP2C19, CYP3A, and CYP2B6, with a 9.3-fold faster hepatic clearance rate compared to modafinil. The principal metabolite (M1) is formed by hydroxylation of one of the aromatic rings.

The preclinical pharmacology of CE-123 spans multiple cognitive domains tested in several rodent models. In the spatial hole-board paradigm in male Sprague-Dawley rats, daily oral CE-123 at doses of 1 and 10 mg/kg improved both memory acquisition and memory retrieval, with significantly increased reference memory indices and shortened latency to find baited holes. In the attentional set-shifting task, CE-123 at 0.3 and 1.0 mg/kg increased cognitive flexibility (reduced extra-dimensional shift errors) without increasing impulsivity. In aged (26-month) Lister Hooded rats, (S)-CE-123 markedly enhanced motivation and performance in a new-to-learn operant discrimination task and in a cooperation assay of social cognition, with post-treatment proteomic analysis of prefrontal cortex synaptosomes revealing modulation of pathways involved in synaptic vesicle recycling, receptor-mediated endocytosis, and alpha-synuclein membrane localization. In a maternal separation model of early-life stress, CE-123 restored spatial memory deficits in adolescent rats with sex-dependent effects favoring females, and normalized maternal-separation-induced upregulation of DAT and dopamine D1 receptor expression in the prefrontal cortex and hippocampus. In a neonatal ethanol exposure model of fetal alcohol spectrum disorders, CE-123 at 3 and 10 mg/kg attenuated locomotor hyperactivity and ameliorated reversal learning impairment. Neurochemical microdialysis studies in freely moving rats demonstrated that (S)-CE-123 at 10 mg/kg intraperitoneally increased extracellular dopamine in the infralimbic/prelimbic cortex with a pharmacodynamic profile distinct from R-modafinil, and produced only a low and transitory dopamine increase in the nucleus accumbens shell, consistent with reduced reinforcing potential.

No human clinical trials of CE-123 have been published or registered as of the date of this monograph. The compound is not approved by any regulatory authority for human use. It is supplied as a research-grade preparation by multiple chemical vendors at greater than 98 percent purity. A process development and scale-up synthesis has been published (ACS Omega, 2023), establishing a scalable route to the (S)-enantiomer. This monograph reviews the chemistry, synthesis, and stereochemistry of CE-123; the DAT inhibitor pharmacology in molecular and functional detail; the pharmacokinetic characterization including blood-brain barrier penetration; the preclinical cognitive pharmacology across multiple behavioral paradigms and disease models; sourcing and quality verification; reconstitution and handling; stack-interaction considerations; adverse-event signal from preclinical studies; and a comparative assessment of five alternative cognitive-enhancing DAT-active compounds against CE-123 on five competency standards. The compound is strictly a research tool at this stage of development; investigators should obtain analytical confirmation of identity and purity on every lot and should not extrapolate preclinical findings to human dose-response without appropriate regulatory and ethical authorization.

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May 15, 2026
Tuftsin

Our opinion on this compoundEstablished workhorse

39/100

Classic IgG-derived phagocyte activator with elegant mechanism but stalled clinical program and a more tractable derivative in Selank

Look, tuftsin is one of those compounds where the discovery story is genuinely elegant but the research trajectory kind of stalled out. Najjar’s 1970 work at Tufts nailed the biology: a tetrapeptide (Thr-Lys-Pro-Arg) cleaved sequentially from the CH2 domain of IgG heavy chain by tuftsin-endocarboxypeptidase in the spleen and then by a phagocyte-surface leukokinase. That two-enzyme liberation mechanism, with the spleen as an obligate processing organ, is textbook-quality immunology that still gets cited in phagocyte biology courses. The splenectomy deficiency syndrome is the kind of documented, reproducible human-relevant validation that most research peptides never get close to.

The neuropilin-1 receptor story adds a layer of contemporary interest. NRP-1 sits at an intersection of immune signaling, angiogenesis, and SARS-CoV-2 entry co-receptor biology, and tuftsin’s affinity for it gives the peptide a current research hook thats not entirely exhausted. Downstream TGF-beta pathway engagement and calcium-dependent phagocyte activation are mechanistically coherent if not spectacular. Multi-target it is not, but the signaling logic is clean and the endogenous origin lends the mechanism a physiological credibility that purely synthetic immunostimulants lack.

What we dont like is where the clinical program went after the early work. The Phase I safety study and Phase II cancer data are old, small, and haven’t been followed with any modern well-powered trials in the Western literature. Selank, the heptapeptide extension (Thr-Lys-Pro-Arg-Pro-Gly-Pro), ended up capturing most of the practical clinical interest, with an anxiolytic and neuroprotective program primarily in Russia. For most investigators who care about the pharmacological space tuftsin opened, Selank is the more tractable compound today. Tuftsin itself suffers from a plasma half-life measured in minutes, low oral bioavailability, and a dependence on splenic processing that makes in vivo dosing design awkward.

The drug delivery scaffold angle is honestly the most active frontier right now. TKPR-bearing conjugates and tuftsin-functionalized nanoparticle systems have been explored as macrophage-targeting vectors, and the specificity for activated phagocytes gives it real probe value in that context even if the parent peptide isnt the pharmacological endpoint. For investigators working on macrophage-targeted drug delivery or NRP-1 signaling biology, tuftsin remains a genuinely useful tool rather than a historical footnote.

We think this is a compound with a beautiful mechanistic origin, documented human deficiency biology, and solid bench utility in specific programs. But the clinical development never materialized in any modern rigorous way, the most interesting derivative has its own separate story, and for an immunostimulatory research program there’s stronger and more current evidence in other peptide classes. A serious investigator outside macrophage targeting or NRP-1 work would have limited reason to put this at the top of the queue.

Novelty

28

Mechanism promise

42

In-category differentiation

37

Evidence quality

42

Translational signal

40

Research bench value

50

Rationale Tuftsin earns real evidence credit from 50-plus years of multi-lab preclinical work and the well-documented splenectomy deficiency syndrome, but the absence of modern well-powered clinical trials, rapid plasma degradation, and the fact that Selank has absorbed most of the actionable development interest keep the score firmly in established-mature territory; the drug delivery scaffold angle and NRP-1 hook prevent it from dropping lower.

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

Endogenous immunostimulatory tetrapeptide derived from the CH2 domain of immunoglobulin G

A spleen-dependent, IgG-derived tetrapeptide that activates phagocytic cells through neuropilin-1 receptor binding, stimulating macrophage phagocytosis, chemotaxis, and tumoricidal activity, and serving as the structural parent of the anxiolytic heptapeptide Selank.

Abstract

Tuftsin (L-threonyl-L-lysyl-L-prolyl-L-arginine) is an endogenous tetrapeptide corresponding to residues 289 through 292 of the CH2 domain of the immunoglobulin G (IgG) heavy chain. First identified in 1970 by Victor A. Najjar and Keisuke Nishioka at the Tufts University School of Medicine during investigations of phagocytosis by polymorphonuclear granulocytes, the peptide derives its name from its institutional origin and has since become the prototype endogenous immunostimulatory peptide. Tuftsin is not synthesized de novo but is liberated from a larger IgG-associated polypeptide termed leukokinin through the sequential action of two proteases: tuftsin-endocarboxypeptidase, a splenic enzyme that cleaves the C-terminal bond of the tetrapeptide within the intact immunoglobulin, and leukokinase, a serine protease on the outer membrane of phagocytic cells that releases the active N-terminal tetrapeptide from the partially processed fragment. This two-step enzymatic liberation places the spleen as an obligate organ in tuftsin physiology and accounts for the well-documented tuftsin deficiency, impaired phagocytic function, and increased susceptibility to overwhelming bacterial infection observed following splenectomy.

The molecular pharmacology of tuftsin centers on its binding to neuropilin-1 (NRP1), a single-pass transmembrane glycoprotein that also serves as a co-receptor for vascular endothelial growth factor (VEGF) and transforming growth factor beta (TGF-beta). Tuftsin binds the b1 domain of neuropilin-1 through a motif similar to the C-terminal sequence encoded by exon 8 of VEGF165, and signals through TGF-beta receptor 1 (a co-receptor of NRP1) via the canonical Smad3 phosphorylation pathway, with concurrent reduction in Akt phosphorylation. At the cellular level, tuftsin binding stimulates phagocytosis, pinocytosis, chemotaxis, respiratory burst (superoxide anion and hydrogen peroxide generation), antigen presentation, and tumoricidal activity in monocytes, macrophages, neutrophils, microglia, and Kupffer cells. Intracellular calcium serves as a critical second messenger in tuftsin-mediated phagocyte activation. In neuroinflammatory models, tuftsin promotes an anti-inflammatory M2 microglial phenotype shift, suppresses pro-inflammatory Th1 responses, upregulates Th2 responses, and expands regulatory T cell populations.

Pharmacokinetically, tuftsin is an extremely labile peptide in vivo, with a plasma half-life of approximately 16 minutes owing to rapid degradation by serum aminopeptidases and carboxypeptidases. Oral bioavailability is negligible because of gastric peptidase destruction. The rapid enzymatic clearance has been the principal barrier to clinical development. Initial clinical studies conducted at the Weizmann Institute of Science demonstrated that tuftsin is nontoxic in humans when administered intravenously at doses up to 5 mg per injection in patients with advanced malignancy; a Phase II study in 25 patients with various advanced cancers reported leucocytosis and increased natural killer activity with two partial responses among 16 evaluable patients, confirming biological activity but insufficient monotherapy efficacy.

The most significant translational legacy of tuftsin is the development of Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro), a synthetic heptapeptide analog in which the tuftsin sequence is extended at the C-terminus with a Pro-Gly-Pro tripeptide motif that confers resistance to enzymatic degradation and facilitates blood-brain barrier penetration. Selank was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences and is approved in Russia as a nasal spray for generalized anxiety disorder and neurasthenia. Selank exhibits pronounced anxiolytic, nootropic, and immunomodulatory activity through mechanisms including allosteric modulation of GABA-A receptors and modulation of monoamine neurotransmitter metabolism, and does so without the sedation, tolerance, or dependence associated with benzodiazepines.

Beyond Selank, tuftsin has been developed as a targeting ligand for liposomal and nanoparticle drug delivery systems. Palmitoyl tuftsin grafted onto liposome surfaces enables selective binding to phagocytic cells and has demonstrated augmented antitumor efficacy of encapsulated cytotoxic agents (etoposide, doxorubicin, curcumin) against fibrosarcoma and Ehrlich ascites carcinoma in murine models. Tuftsin-bearing liposomes have also been used to deliver antimicrobial agents to macrophage-resident intracellular pathogens including Leishmania and Plasmodium species.

This monograph reviews the chemistry, enzymatic biogenesis, and structural biology of tuftsin; the neuropilin-1 receptor pharmacology and downstream signaling; the pharmacokinetic constraints and stabilization strategies; the preclinical pharmacology across immunostimulatory, anti-inflammatory, antitumor, and anti-infective applications; the clinical evidence base; sourcing and quality verification; reconstitution and handling; stack interactions; adverse events and safety; and a comparative assessment of five immunostimulatory peptide candidates (Selank, thymosin alpha-1, muramyl dipeptide, GM-CSF, and thymopentin) against tuftsin 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 15, 2026
1,4-DMAA

Our opinion on this compoundLow merit

13/100

An uncharacterized supplement adulterant with inferred mechanism, zero primary pharmacology, and no research merit

Look, the honest framing here is that 1,4-DMAA is not a research compound. It’s a positional isomer that got caught hiding in pre-workout supplements because nobody was looking for it specifically, and the two papers that define its entire published existence (Cohen et al., 2018 in Clinical Toxicology; Fleming et al., 2012 on geranium detection) are analytical chemistry and regulatory forensics, not pharmacology. There are no receptor binding studies, no transporter interaction assays, no in vivo behavioral data, no pharmacokinetics. The mechanism section of any monograph is necessarily a thought experiment borrowed from 1,3-DMAA’s sparse literature.

The structural analogy reasoning goes like this: 1,3-DMAA inhibits the dopamine transporter with an IC50 around 29.4 micromolar (Bhatt et al., 2023), roughly 60-fold weaker than amphetamine, and induces DAT endocytosis through cocaine- and PKA-sensitive pathways. Move the methyl branch one carbon position and you get 1,4-DMAA. Does that change potency? Selectivity? Transporter preference? Nobody has measured it. We genuinely dont know whether the 1,4-isomer has any meaningful pharmacological activity in a preparation you could actually run an assay on.

Whats particularly damaging from a research-merit standpoint is the differentiation picture. If you want to study aliphatic alkylamine sympathomimetics, 1,3-DMAA is the reference compound with a real (if limited) pharmacological literature. If you want a well-characterized indirect sympathomimetic, amphetamine and methamphetamine have decades of mechanistic data. 1,4-DMAA offers nothing that either of those alternatives doesnt already provide, except the unique property of being even less characterized. Thats not a research advantage.

The regulatory situation makes bench work harder for no scientific payoff. The FDA has stated that dietary supplements containing 1,4-DMAA are illegal and should not be consumed. WADA lists it on the Prohibited List under S6 (stimulants). Institutional review for any human study involving this compound would be essentially impossible to obtain at this stage given the complete absence of safety data and the regulatory posture. The cardiovascular risk signal inferred from the class (hypertension, tachycardia, theoretical hemorrhagic stroke risk) is real enough to require serious caution in any in vivo work, and you’d be accepting that risk without even knowing the actual dose-response relationship.

We think the only legitimate bench application is as an analytical reference standard for supplement testing and plant material identification work. Thats genuinely narrow, and it doesnt require understanding the pharmacology at all. If your lab is doing supplement adulterant detection, a certified reference standard matters. If your lab is doing anything else, theres no reason to reach for this compound over any better-characterized alternative in the sympathomimetic space. The score reflects a compound that exists in the pharmacological literature the same way a shipping manifest exists in a scientific archive: useful as a record that something passed through, not useful for understanding anything.

Novelty

28

Mechanism promise

15

In-category differentiation

8

Evidence quality

7

Translational signal

5

Research bench value

12

Rationale 1,4-DMAA has no independent pharmacological characterization whatsoever; every mechanistic claim is borrowed by structural analogy from 1,3-DMAA, and the only published literature consists of two detection papers. Evidence, translational signal, and differentiation scores collapse to the floor, producing a raw overall of 13 before any cap consideration.

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

Aliphatic alkylamine sympathomimetic stimulant and putative monoamine releasing agent

A branched-chain aliphatic amine structurally related to methylhexanamine (1,3-DMAA), identified in geranium plant material and in dietary supplements, with presumed sympathomimetic and catecholamine-releasing activity but no approved pharmaceutical application and a minimal primary pharmacological literature.

Abstract

1,4-Dimethylamylamine (1,4-DMAA), systematically named 5-methylhexan-2-amine, is a branched-chain aliphatic amine of the alkylamine stimulant class. It is a positional isomer of the better-characterized 1,3-dimethylamylamine (1,3-DMAA, methylhexanamine), differing in the placement of the methyl branch along the carbon backbone: in 1,3-DMAA the branch is at carbon 4 (producing 4-methylhexan-2-amine), whereas in 1,4-DMAA the branch is at carbon 5 (producing 5-methylhexan-2-amine). The compound has never been developed or marketed as a pharmaceutical agent, in contrast to 1,3-DMAA, which was introduced by Eli Lilly as an inhaled nasal decongestant (Forthane) in 1948 and voluntarily withdrawn in 1983. 1,4-DMAA came to regulatory and scientific attention through its identification in dietary supplements marketed for pre-workout stimulation and weight loss, where it was detected at doses of 21 to 94 mg per serving alongside other undeclared stimulants including 1,3-DMAA, octodrine, and 1,3-dimethylbutylamine, as reported by Cohen et al. (2018) in Clinical Toxicology. The compound has also been detected at trace concentrations (13 to 162 ng/g) in Pelargonium graveolens (geranium) plant material from the Changzhou region of China, as documented by Fleming et al. (2012), though these concentrations are insufficient to account for the milligram-scale quantities found in commercial supplement formulations. The pharmacology of 1,4-DMAA has not been independently characterized in published receptor-binding, transporter-interaction, or in vivo behavioral studies. Its mechanism of action is inferred by structural analogy to 1,3-DMAA and to the broader class of aliphatic alkylamine sympathomimetics. 1,3-DMAA has been characterized as an indirect sympathomimetic agent that competitively inhibits dopamine uptake at the human dopamine transporter (DAT) with an IC50 of approximately 29.4 micromolar (roughly 60-fold less potent than amphetamine) and that induces DAT endocytosis through cocaine- and protein kinase A-sensitive mechanisms, as reported by Bhatt et al. (2023). By structural analogy, 1,4-DMAA is presumed to function as a catecholamine releasing agent with sympathomimetic properties, producing vasoconstriction, elevated blood pressure, increased heart rate, and central nervous system stimulation, though the potency and selectivity of these effects relative to 1,3-DMAA remain unquantified. No human pharmacokinetic data specific to 1,4-DMAA have been published. The pharmacokinetic profile of 1,3-DMAA, characterized by Bloomer et al. (2013) in seven healthy men receiving a single 25 mg oral dose, provides the closest available analog: peak plasma concentration of approximately 70 ng/mL at 3.6 hours, terminal elimination half-life of 8.5 hours, oral clearance of 20 L/hr, and volume of distribution of 236 L. Whether these parameters translate to the 1,4-isomer is unknown. The safety of 1,4-DMAA in humans is unknown. The compound has not been studied in controlled clinical trials at any dose. Cardiovascular adverse events (hypertension, tachycardia, and theoretical risk of hemorrhagic stroke and sudden cardiac death) are inferred from the pharmacology of structurally related sympathomimetic amines and from case reports associated with 1,3-DMAA-containing products. The United States Food and Drug Administration considers 1,4-DMAA to be an illegal ingredient in dietary supplements and has stated that products containing it should not be consumed. The World Anti-Doping Agency includes 1,4-dimethylamylamine on the Prohibited List under category S6 (stimulants, prohibited in competition). This monograph reviews the chemistry, structural classification, inferred mechanism of action, pharmacokinetic analogy data, detection in plant material and supplements, regulatory status, adverse-event signal, sourcing and handling considerations, and a comparative assessment of five structurally or functionally related alkylamine stimulants against 1,4-DMAA on five competency standards: novelty, effect size, side-effect profile, regulatory status, and overall validation.

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May 15, 2026
Apelin-13

Our opinion on this compoundEstablished, active research

51/100

Endogenous APJ agonist with genuine multi-organ biology but critical PK constraints limit research utility

Look, the apelin system is one of those GPCR programs where the underlying biology is genuinely interesting but the native peptide keeps running into the same wall: it’s gone before you can study it properly. Apelin-13, identified in 1998 from the Tatemoto lab’s deorphanization of APJ, is the highest-potency endogenous agonist of that receptor. The predominant circulating form is [Pyr1]apelin-13, the pyroglutamylated version that survives aminopeptidase attack better than the unmodified sequence. That stability difference matters, but even [Pyr1]apelin-13 clears in minutes under physiological conditions, and that shapes what you can realistically do with it bench-side.

The mechanism earns real credit. APJ is a class A GPCR with characterized cardiovascular inotropic activity, vasodilation via nitric oxide pathways, aquaretic effects through a non-ADH renal mechanism, and emerging metabolic and neuroprotective angles. Thats a multi-organ footprint thats not typical of most peptide receptor systems. The beta-arrestin recruitment and biased agonism angle adds genuine complexity: different downstream signaling pathways give investigators something real to dissect. The 2015 identification of Elabela as a second endogenous APJ ligand confirmed the system has biological depth that isnt fully mapped.

Preclinical evidence is solid and multi-lab. Cardiovascular pharmacology, nephrology, and metabolism groups across multiple continents have worked the APJ axis since the early 2000s. Hemodynamic studies in healthy volunteers, modest heart failure data, and some CKD work constitute the clinical base. Honestly, that clinical evidence is the weak link: small N, short duration, modest effect sizes, and no published phase 2 with a stabilized analogue demonstrating durable benefit. The human signal is real but it hasnt been developed.

Differentiation is where the calculus gets complicated. Apelin-13 is the reference ligand for APJ receptor pharmacology, and for that role it remains indispensable. But Amgen’s AMG-986 and Bristol-Myers Squibb’s BMS-986224 are synthetic APJ agonists with engineered pharmacokinetics that are clearly superseding native apelin-13 for anything resembling translational or in vivo modeling work. If your program is characterizing receptor binding, signaling bias, or downstream pathway pharmacology, the native peptide anchors the field. If your program is trying to model sustained APJ activation in a disease model, you probably want a stabilized analogue.

We think apelin-13 sits comfortably in the established-active tier. The receptor system is still yielding new biology, particularly around biased agonism and the dual-ligand story with Elabela. But the compound itself is 25 years old with well-documented limitations. Investigators who care about APJ biology should know it well and use it for receptor characterization work. As the primary research compound in a cardiovascular or metabolic peptide program, there are better tools available now.

Novelty

48

Mechanism promise

62

In-category differentiation

42

Evidence quality

48

Translational signal

45

Research bench value

62

Rationale Apelin-13 has a legitimate and still-active research footprint across cardiovascular, renal, and metabolic pharmacology, but as a 1998-identified native peptide with sub-minute plasma half-life, it scores moderate on novelty and differentiation; the mechanism is genuinely interesting (multi-organ GPCR with biased agonism biology), but synthetic APJ agonists from Amgen and BMS are already outpacing it for translational work, and clinical evidence remains thin.

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

Endogenous bioactive peptide agonist of the apelin receptor (APJ/APLNR), a class A G protein-coupled receptor

A pyroglutamyl-modified tridecapeptide derived from the C-terminus of preproapelin, identified as the predominant circulating isoform and the highest-potency endogenous agonist of the APJ receptor, with characterized cardiovascular inotropic, vasodilatory, aquaretic, metabolic, and neuroprotective activities.

Abstract

Apelin-13, the C-terminal tridecapeptide fragment of the 77-amino-acid preproapelin precursor, is the most potent endogenous agonist of the apelin receptor (APJ, also designated APLNR), a class A rhodopsin-like G protein-coupled receptor originally cloned as an orphan receptor in 1993 by O’Dowd et al. on the basis of sequence homology with the angiotensin II type 1 receptor. The receptor was deorphanized in 1998 by Tatemoto and colleagues at the Takeda Chemical Research Institute, who isolated apelin from bovine stomach extracts using an extracellular acidification assay on APJ-expressing Chinese hamster ovary cells and demonstrated that apelin-13 displayed 8- to 60-fold higher potency than the longer apelin-36 isoform. The predominant circulating form in human plasma is [Pyr1]apelin-13 (pyroglutamyl apelin-13), in which the N-terminal glutamine residue undergoes spontaneous or enzymatic cyclization to pyroglutamate, conferring modest resistance to aminopeptidase degradation and representing the principal bioactive isoform in cardiovascular tissue and plasma.

Apelin-13 activates APJ with sub-nanomolar potency (EC50 approximately 0.37 nM in cellular acidification assays), coupling predominantly through Gi/o proteins to inhibit adenylyl cyclase and reduce intracellular cAMP, through Gq/11 to activate phospholipase C and mobilize intracellular calcium, and through G12/13 to engage RhoA-dependent cytoskeletal rearrangement. The receptor also recruits beta-arrestin 1 and 2, mediating receptor internalization and activating extracellular signal-regulated kinase 1/2 (ERK1/2) through G protein-independent pathways. The downstream signaling cascade includes activation of phosphoinositide 3-kinase (PI3K)/Akt, endothelial nitric oxide synthase (eNOS), AMP-activated protein kinase (AMPK), and inhibition of reactive oxygen species generation, collectively producing the cardiovascular, metabolic, and cytoprotective effects that define the pharmacological profile.

The cardiovascular pharmacology of apelin-13 is the most extensively characterized domain. In human clinical studies, systemic infusion of [Pyr1]apelin-13 at 30 to 300 nmol/min produces a sustained approximately 10 percent increase in cardiac index, increased ejection fraction, reduced systemic vascular resistance by approximately 12 percent, and reduced mean arterial pressure by approximately 4 percent, effects observed in both healthy volunteers and patients with chronic heart failure and chronic kidney disease. The mechanism involves direct positive inotropic action on cardiomyocytes through APJ-mediated calcium sensitization, nitric oxide-dependent vasodilation in resistance arteries, and counter-regulatory opposition to the renin-angiotensin-aldosterone system. Preclinical models demonstrate cardioprotective effects in myocardial infarction, ischemia-reperfusion injury, pressure-overload hypertrophy, and diabetic cardiomyopathy, with mechanisms including salvage of the peri-infarct border zone, mobilization of endogenous cardiac stem cells, and suppression of pathological fibrosis.

The renal pharmacology is defined by the functional antagonism between apelin and arginine vasopressin (AVP) at the collecting duct. Apelin-13 inhibits vasopressin-induced translocation of aquaporin 2 (AQP2) water channels to the apical membrane of principal cells through Gi-mediated inhibition of cAMP/protein kinase A signaling, producing a diuretic (aquaretic) effect that opposes AVP-driven water reabsorption. This reciprocal regulation positions the apelin/AVP axis as a physiological rheostat for water homeostasis, with therapeutic implications for hyponatremia and states of AVP excess.

Metabolic pharmacology encompasses insulin-sensitizing and glucoregulatory effects. Apelin-13 administration in diabetic rodent models reduces blood glucose, increases serum insulin, improves pancreatic islet mass, and enhances glucose uptake in skeletal muscle through AMPK-dependent GLUT4 translocation. Neuroprotective activity has been demonstrated in models of ischemic stroke, diabetes-associated cognitive decline, and excitotoxic injury, with mechanisms including antioxidant defense through the SIRT3/FoxO3 pathway, anti-inflammatory cytokine modulation, and direct neuronal survival signaling through PI3K/Akt.

The principal pharmacokinetic limitation of apelin-13 is its extremely short plasma half-life. Native [Pyr1]apelin-13 has a plasma half-life of approximately 21 to 24 minutes in rodents, driven by rapid proteolytic degradation at the Leu5-Ser6 peptide bond by neprilysin, angiotensin-converting enzyme 2 (ACE2), and plasma kallikrein. This has motivated extensive medicinal chemistry efforts to develop stabilized analogues (macrocyclic peptides, D-amino acid substitutions, PEGylation) and small-molecule APJ agonists (AMG-986, BMS-986224, azelaprag) for chronic administration.

This monograph reviews the chemistry, identification, and structural biology of apelin-13; the discovery and deorphanization history of the APJ receptor; the molecular pharmacology across Gi, Gq, G12/13, and beta-arrestin pathways; the pharmacokinetic profile and proteolytic degradation pathways; the preclinical evidence base across cardiovascular, renal, metabolic, and neurological domains; the clinical evidence from human hemodynamic studies; sourcing and quality verification for research-grade material; reconstitution and handling protocols; stack interactions with vasoactive and metabolic agents; the adverse-event and safety profile; and a comparative assessment of five APJ receptor agonist candidates against apelin-13 on five competency standards. The compound is not an approved therapeutic agent in any jurisdiction. It is supplied as a research-grade peptide; investigators should obtain analytical confirmation of identity, purity, and peptide content 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 15, 2026
Dapoxetine

Our opinion on this compoundEstablished workhorse

42/100

Clinically approved PE-specific SSRI with modest novelty and narrow research utility

Look, the story of dapoxetine is fundamentally a repositioning story, not a discovery story. Eli Lilly synthesized LY 210448 in the late 1980s chasing antidepressant activity, it didn’t work, got shelved, bounced through PPD and then ALZA before landing on an indication it actually fits. That history tells you something important about its research profile: the molecule is old, the mechanism is standard SSRI pharmacology, and the interesting finding wasn’t a new compound but a new application of known pharmacokinetics to a clinical problem that had no good oral solution.

The pharmacokinetic angle is genuinely the differentiator. Conventional SSRIs are dosed chronically because their half-lives don’t accommodate on-demand use, and the ejaculatory delay they produce is a side effect people tolerate, not a therapeutic intent. Dapoxetine was optimized around rapid absorption and short initial half-life specifically to make event-based dosing viable. That engineering is smart. But the underlying mechanism, central serotonin transporter inhibition with downstream modulation of the supraspinal ejaculatory reflex, is not novel biology. We’ve known for decades that serotonin signaling brakes ejaculatory threshold. Dapoxetine just does it with better timing.

The evidence base is real and well-constructed. Multiple large Phase 3 RCTs, long-term extension data, meta-analyses, and regulatory approval in over 60 countries add up to one of the more credible approval packages in this corner of pharmacology. The FDA’s 2005 not-approvable letter was a process and data sufficiency issue, not a signal that the effect isn’t there. Effect sizes in pivotal trials show intravaginal ejaculatory latency time roughly doubling or tripling from baseline, which is clinically meaningful even if it doesn’t look dramatic in absolute terms.

What we don’t like, from a research-library perspective, is how narrow this all is. Dapoxetine is interesting if your program is PE pathophysiology, ejaculatory reflex circuitry, or the comparative pharmacology of on-demand versus chronic SSRI dosing. Outside those lanes, theres almost nothing to work with. It’s not a useful probe for broader serotonin biology where paroxetine or citalopram are already better characterized. It doesn’t open any new mechanistic territory. The PK profile is the science, and thats already been documented extensively.

Honestly, if you’re in sexual medicine research, dapoxetine is a legitimate reference compound. If you’re outside that area, it’s a compound to note in a table and move past. The score reflects that accurately.

Novelty

25

Mechanism promise

25

In-category differentiation

50

Evidence quality

65

Translational signal

60

Research bench value

28

Rationale Dapoxetine scores on differentiation and evidence because it is genuinely the only approved on-demand oral PE pharmacotherapy, with multiple Phase 3 trials and 60-plus international registrations behind it. What drags the overall down is that the mechanism is vanilla SERT inhibition, novelty is low for a compound synthesized in the late 1980s, and bench value outside ejaculatory-reflex physiology is essentially nil.

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

Short-acting selective serotonin reuptake inhibitor (SSRI) with rapid-onset, rapid-elimination pharmacokinetics developed for on-demand treatment of premature ejaculation

A naphthalene-derived phenylpropylamine SSRI originally developed at Eli Lilly as an antidepressant candidate, repositioned as the first and only oral pharmacotherapy specifically approved for on-demand treatment of premature ejaculation, distinguished from conventional SSRIs by rapid absorption, short initial half-life, and suitability for event-based rather than chronic dosing.

Abstract

Dapoxetine (LY 210448) is a short-acting selective serotonin reuptake inhibitor (SSRI) and the first oral pharmacotherapy specifically developed and approved for the on-demand treatment of premature ejaculation (PE) in adult men aged 18 to 64 years. Originally synthesized at Eli Lilly and Company as an antidepressant candidate in the late 1980s, the compound was shelved after failing to demonstrate sufficient efficacy in depression, subsequently licensed to Pharmaceutical Product Development (PPD) in 2003, and then advanced through Phase 3 clinical development by ALZA Corporation (a Johnson and Johnson subsidiary) for the PE indication. Dapoxetine received its first regulatory approvals in Finland and Sweden in 2009 under the trade name Priligy and has since been registered in over 60 countries across Europe, Asia, Latin America, and Oceania. The compound has not been approved by the United States Food and Drug Administration, which issued a not-approvable letter in 2005 citing the need for additional efficacy and safety data.

The pharmacological mechanism of dapoxetine is inhibition of the serotonin transporter (SERT) at both peripheral and central sites, increasing serotonin availability at postsynaptic receptors in the ejaculatory pathway. Preclinical electrophysiology studies in anaesthetized rats demonstrated that dapoxetine inhibits the ejaculatory expulsion reflex at a supraspinal level, specifically modulating activity of lateral paragigantocellular nucleus (LPGi) neurons that project to spinal ejaculatory motor centers. The compound exhibits high selectivity for the serotonin transporter over the norepinephrine and dopamine transporters, with Ki values of approximately 1.0 nM for SERT, 66 nM for the norepinephrine transporter, and greater than 1000 nM for the dopamine transporter.

The critical pharmacokinetic distinction of dapoxetine from conventional SSRIs (paroxetine, fluoxetine, sertraline, citalopram) is its rapid absorption and elimination profile. After oral administration, dapoxetine reaches maximum plasma concentration (Cmax) within approximately 1.0 to 1.3 hours, with an initial distribution half-life of 1.3 to 1.4 hours and a terminal elimination half-life of 18.7 to 21.9 hours. Oral bioavailability is approximately 42 percent, with substantial interindividual variability (range 15 to 76 percent) attributable to first-pass hepatic metabolism. Metabolism proceeds through CYP3A4, CYP2D6, and flavin-containing monooxygenase 1 (FMO1) pathways, producing dapoxetine N-oxide (inactive), N-desmethyldapoxetine (active), and N,N-didesmethyldapoxetine (active) as the principal circulating metabolites. Plasma protein binding exceeds 99 percent.

Five pivotal Phase 3 randomized, double-blind, placebo-controlled trials enrolling 6,081 men across more than 25 countries established the clinical efficacy of dapoxetine at 30 mg and 60 mg on-demand doses. Integrated analysis demonstrated that mean intravaginal ejaculatory latency time (IELT) increased from a baseline of 0.9 minutes to 3.2 minutes with dapoxetine 30 mg and 3.5 minutes with dapoxetine 60 mg, compared to 1.9 minutes with placebo. Statistically significant improvements were observed across all patient-reported outcome domains including ejaculatory control, satisfaction with sexual intercourse, ejaculation-related personal distress, and interpersonal difficulty. The safety profile is consistent with the SSRI pharmacological class; the most common adverse events are nausea (8.7 to 20.1 percent), dizziness (5.8 to 10.9 percent), headache (5.6 to 8.8 percent), diarrhea (3.9 to 6.8 percent), and somnolence. A specific safety concern is vasovagal-mediated syncope, observed at rates of 0.06 percent with 30 mg and 0.23 percent with 60 mg compared to 0.05 percent with placebo. Dapoxetine is contraindicated with potent CYP3A4 inhibitors, monoamine oxidase inhibitors, other serotonergic agents, and in patients with significant cardiovascular disease or a history of syncope.

This monograph reviews the chemistry, synthesis, and stereochemistry of dapoxetine; the serotonin transporter pharmacology and supraspinal ejaculatory reflex modulation mechanism in molecular and electrophysiological detail; the comprehensive human pharmacokinetic record including CYP2D6 and CYP3A4 metabolic polymorphism; the clinical evidence base across premature ejaculation and combination therapy with phosphodiesterase type 5 inhibitors; the reconstitution, sourcing, and quality verification considerations for laboratory work; stack-interaction implications; adverse-event signal including syncope and serotonin syndrome risk; and a comparative assessment of five alternative premature ejaculation pharmacotherapies against dapoxetine on five competency standards (novelty, effect size, promising potential, side-effect profile, and overall validation).

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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.

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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 15, 2026
Nortadalafil

Our opinion on this compoundNiche research probe

16/100

Minor tadalafil analogue with no independent research value beyond forensic reference use

Look, the honest question to ask about nortadalafil is: compared to what? And the answer, almost always, is tadalafil. The N-methyl group removal from the piperazinedione ring is a minor structural change that produces a compound with roughly twice the IC50 at PDE5 (around 11 to 12 nM versus tadalafil’s approximately 5 nM), a dramatically shorter elimination half-life (approximately 6 hours versus tadalafil’s 17.5 hours), no regulatory approval in any jurisdiction, no controlled clinical trials, and no systematic toxicology. This is not the story of a promising analogue. Its the story of a compound that exists primarily because supplement manufacturers wanted PDE5 inhibitory activity in a product while evading the analytical screens that flag tadalafil itself.

The mechanism is PDE5 inhibition through the cGMP-nitric oxide signaling cascade. That pathway is extraordinarily well understood. Tadalafil has carried FDA approval since 2003. Sildenafil since 1998. The PDE5 inhibitor space has been mapped exhaustively by multiple well-funded pharma programs across hundreds of peer-reviewed studies. Nortadalafil adds nothing to that mechanistic picture. It’s not probing a novel allosteric pocket, it’s not demonstrating unique isoform selectivity, and its slightly altered PK profile (attributable to increased hepatic clearance after losing the N-methyl group) doesnt unlock any new research question that couldn’t be addressed more cleanly with the approved parent compound.

Where it does carry genuine, if narrow, utility is analytical and forensic work. If your lab is characterizing adulterated dietary supplements, building detection methods for novel PDE5 inhibitor variants in complex matrices, or assembling a reference standard library for regulatory or customs-support applications, nortadalafil is a legitimate research-grade tool. The analytical characterization literature covering HPLC-DAD, HRMS, and NMR structural confirmation is real and reasonably thorough for that specific purpose. That’s not nothing. But it’s a long way from defining a research program.

What we don’t see here is any translational pathway. No investigator is running an IND on this compound. No first-in-human studies are planned or obvious. The safety profile is inferred entirely from the PDE5 inhibitor class, with the absolute contraindication of concurrent nitrate administration being the headline concern, and interactions with alpha-1 antagonists and potent CYP3A4 inhibitors applying by extension. The actual dose-response and adverse-event profile specific to nortadalafil is simply unknown.

We think the calculus is straightforward here. If you need a PDE5 inhibitor probe for mechanistic research, use tadalafil. If you need to detect and characterize nortadalafil in a supplement matrix, this is your reference standard. Outside those narrow windows, theres no compelling scientific case to work with this compound over its better-characterized, approved, and pharmacologically superior parent.

Novelty

18

Mechanism promise

15

In-category differentiation

10

Evidence quality

12

Translational signal

14

Research bench value

32

Rationale Nortadalafil is a structurally trivial, pharmacologically inferior variant of an approved PDE5 inhibitor, present in the scientific literature almost entirely through supplement adulteration detection work; it carries no novel mechanism, weaker PDE5 potency than the parent compound, zero controlled clinical data, and only narrow utility as an analytical reference standard.

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

Synthetic phosphodiesterase type 5 (PDE5) inhibitor; N-desmethyl analogue of tadalafil

An unapproved, demethylated structural analogue of tadalafil with retained nanomolar PDE5 inhibitory potency, identified principally as a synthetic adulterant in dietary supplements marketed for sexual enhancement and as a reference standard for forensic and analytical chemistry.

Abstract

Nortadalafil (demethyl tadalafil, CAS 171596-36-4) is a synthetic analogue of the clinically approved phosphodiesterase type 5 (PDE5) inhibitor tadalafil, distinguished from the parent compound by the absence of the N-methyl substituent on the piperazinedione ring of the hexahydropyrazinopyridoindole scaffold. The compound retains nanomolar inhibitory potency against PDE5 (IC50 approximately 11 to 12 nM against bovine PDE5, compared to approximately 5 nM for tadalafil) and produces cGMP-mediated smooth muscle relaxation with EC50 values of 300 to 600 nM in rat aortic preparations. Despite this pharmacological activity, nortadalafil has never been submitted for regulatory approval in any jurisdiction and has not been the subject of controlled clinical trials in human subjects. The compound first entered the scientific literature through its detection as an undeclared adulterant in herbal and dietary supplements marketed for erectile dysfunction, a context in which it represents one member of a large and expanding family of synthetic PDE5 inhibitor analogues (including aminotadalafil, N-octylnortadalafil, chloropretadalafil, and others) introduced into the unregulated supplement market to evade analytical screening for the approved parent compounds. Analytical characterization of nortadalafil in adulterated products relies on high-performance liquid chromatography with diode-array and mass spectrometric detection, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy. The pharmacokinetic profile of nortadalafil diverges substantially from tadalafil: the reported elimination half-life is approximately 5.9 to 6.2 hours after single oral doses of 40 to 120 mg, compared to the 17.5-hour half-life of tadalafil, a difference attributable to the loss of the N-methyl group and the resulting alteration of hepatic metabolic clearance. No systematic toxicology, no formal pharmacokinetic characterization in healthy volunteers under regulatory oversight, and no controlled efficacy data exist for the compound. Safety concerns are inferred from the PDE5 inhibitor class and include the absolute contraindication of concurrent nitrate administration (risk of severe, potentially fatal hypotension), the interaction with alpha-adrenergic receptor antagonists and potent CYP3A4 inhibitors, and the unknown dose-response and adverse-event profile of a compound consumed without medical supervision at uncharacterized doses in adulterated supplements. This monograph reviews the chemistry, synthesis, and structural relationship of nortadalafil to tadalafil; the molecular pharmacology of PDE5 inhibition and the cGMP-nitric oxide signaling cascade; the limited pharmacokinetic data; the forensic and regulatory context of dietary supplement adulteration; sourcing and quality verification for research applications; handling and reconstitution; stack-interaction considerations; the adverse-event and safety signal inferred from the PDE5 inhibitor class; and a comparative assessment of five PDE5 inhibitor compounds against nortadalafil on five competency standards. The compound is not approved by any regulatory authority. It is available as a research-grade reference standard; investigators should obtain analytical confirmation of identity and purity on every lot.

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-1538Open in new tab →

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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 15, 2026

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