Category: Uncategorized

  • ISX-9

    Isoxazole-based small molecule neurogenic agent with Wnt/beta-catenin pathway activation and GPR68 agonism

    A synthetic isoxazole carboxamide identified through phenotypic screening for neuronal cell fate activation, distinguished by calcium-dependent MEF2 de-repression, NeuroD1 induction, Wnt/beta-catenin signaling through Axin1/LRP6 modulation, and proneurogenic activity in the adult hippocampus with demonstrated cognitive enhancement in rodent behavioral models.

    Abstract

    ISX-9 (Isoxazole 9; N-cyclopropyl-5-(thiophen-2-yl)isoxazole-3-carboxamide; CAS 832115-62-5) is a synthetic small molecule originally identified in a high-throughput phenotypic screen for compounds that activate neuronal cell fate in adult neural stem/progenitor cells, reported by Schneider et al. in 2008 in Nature Chemical Biology [1]. The compound triggers robust neuronal differentiation through a calcium-dependent signaling cascade: ISX-9 induces calcium influx via voltage-gated calcium channels and N-methyl-D-aspartate (NMDA) receptors, which activates calcium/calmodulin-dependent protein kinase II (CaMKII), promotes phosphorylation-dependent nuclear export of histone deacetylase 5 (HDAC5), and thereby de-represses myocyte-enhancer factor 2 (MEF2)-dependent transcription of neuronal genes including NeuroD1 [1, 2]. Subsequent mechanistic characterization identified ISX-9 as a potent activator of the Wnt/beta-catenin signaling pathway through promotion of the association between low-density lipoprotein receptor-related protein 6 (LRP6) and Axin1, resulting in beta-catenin stabilization and upregulation of Wnt target genes [3]. A parallel line of investigation established ISX-9 as a ligand of GPR68 (OGR1), a proton-sensing G protein-coupled receptor expressed in hippocampal neural stem cells, providing a molecular target that links the proneurogenic activity to extracellular pH sensing in the neurogenic niche [4].

    In vivo, ISX-9 crosses the blood-brain barrier and promotes neurogenesis in the subgranular zone of the hippocampal dentate gyrus in adult mice and rats. The Petrik et al. (2012) study in The FASEB Journal demonstrated that systemic ISX-9 administration (20 mg/kg intraperitoneally) enhanced proliferation and differentiation of hippocampal subgranular zone neuroblasts, increased dendritic arborization of adult-generated dentate gyrus neurons, and improved spatial memory performance in the Morris water maze, with all effects dependent on MEF2 isoform expression in neural stem cells [2]. The compound has been investigated across a surprisingly broad range of preclinical applications beyond hippocampal neurogenesis: protection against methamphetamine relapse through modulation of abstinence-induced neurogenesis in the dentate gyrus [5]; induction of enteroendocrine cell differentiation in mouse and human intestinal organoids through upregulation of neurogenin 3 (Ngn3), NeuroD1, and Pax4 [6]; activation of Wnt/beta-catenin-dependent hair follicle cycling and hair regrowth in C57BL/6J mice [3]; and, most recently, neuroprotection and cognitive rescue in the 5xFAD transgenic mouse model of Alzheimer’s disease through Wnt/beta-catenin pathway activation in hippocampal neurons [7].

    ISX-9 has not entered human clinical trials. No human pharmacokinetic, safety, or efficacy data exist. The compound remains a research tool, albeit one with an expanding preclinical evidence base across neurodegenerative, addiction, regenerative, and endocrine lineage specification applications. Investigators should note that ISX-9 exerts differential effects on distinct progenitor populations: it promotes neuronal differentiation of neural stem/progenitor cells but is cytotoxic to oligodendrocyte precursor cells and inhibits angiogenic tube formation in endothelial progenitor cells at comparable concentrations [8]. This cell-type specificity has implications for interpretation of in vivo effects and for combination research in central nervous system injury models where multiple progenitor populations contribute to repair. The compound is commercially available from multiple research chemical suppliers at greater than 98 percent purity and is typically supplied as a solid for reconstitution in dimethyl sulfoxide. This monograph reviews the chemistry, discovery, multi-pathway pharmacology, preclinical evidence base, comparative positioning against five neurogenesis-promoting small molecules (P7C3, NSI-189, BDNF mimetic 7,8-DHF, CHIR99021, and Dihexa), and practical considerations for laboratory use.

    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-1637Open in new tab →

    Download PDF →

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

  • Olpasiran

    N-acetylgalactosamine-conjugated small interfering RNA (GalNAc-siRNA) targeting hepatic LPA messenger RNA for lipoprotein(a) reduction

    A synthetic, chemically modified, GalNAc-conjugated siRNA developed by Arrowhead Pharmaceuticals and licensed to Amgen that silences hepatic LPA gene expression through RNA interference, producing sustained and near-complete reduction of circulating lipoprotein(a) concentrations in patients with established atherosclerotic cardiovascular disease.

    Abstract

    Olpasiran (AMG 890; formerly ARO-LPA) is an investigational, first-in-class, synthetic double-stranded small interfering RNA (siRNA) conjugated to a trivalent N-acetylgalactosamine (GalNAc) ligand for selective hepatocyte delivery via the asialoglycoprotein receptor (ASGPR). The compound targets the messenger RNA transcribed from the LPA gene, which encodes apolipoprotein(a), the defining protein component of lipoprotein(a) [Lp(a)]. Elevated Lp(a) is a genetically determined, independent, and causal risk factor for atherosclerotic cardiovascular disease (ASCVD), aortic valve stenosis, and thrombotic events, affecting an estimated 20 to 30 percent of the global population at concentrations associated with increased cardiovascular risk. Prior to the development of RNA-targeted therapies, no pharmacologic intervention produced clinically meaningful reduction in Lp(a) concentration; niacin and PCSK9 inhibitors achieve modest decreases of 20 to 30 percent, insufficient to test the causal hypothesis relating Lp(a) lowering to cardiovascular event reduction.

    Following uptake into hepatocytes through ASGPR-mediated endocytosis, the antisense strand of olpasiran incorporates into the RNA-induced silencing complex (RISC), which catalytically cleaves LPA mRNA and suppresses de novo synthesis of apolipoprotein(a). The resulting reduction in hepatic apolipoprotein(a) secretion produces a dose-dependent, sustained, and near-complete lowering of circulating Lp(a) particles. In the Phase 1 single ascending-dose trial (NCT03626662), olpasiran produced dose-dependent Lp(a) reductions of 71 to 97 percent that persisted for several months after a single subcutaneous injection, with effects lasting up to six months at higher doses [1]. In the pivotal Phase 2 OCEAN(a)-DOSE trial (NCT04270760), a randomized, double-blind, placebo-controlled study in 281 patients with established ASCVD and Lp(a) greater than 150 nmol/L, olpasiran at doses of 75 mg or higher administered every 12 weeks produced placebo-adjusted Lp(a) reductions exceeding 95 percent at 36 weeks, with the 225 mg every-12-week regimen achieving a placebo-adjusted reduction of 101.1 percent [2]. The off-treatment extension analysis demonstrated that participants who received doses of 75 mg or higher every 12 weeks sustained approximately 40 to 50 percent Lp(a) reduction close to one year after the last dose, reflecting the durability of RISC-mediated mRNA silencing in hepatocytes [3].

    The serum pharmacokinetics of olpasiran are characterized by rapid absorption after subcutaneous injection (time to maximum concentration approximately 3 to 9 hours) and rapid clearance from the systemic circulation (serum half-life approximately 3 to 8 hours), consistent with efficient hepatocyte uptake via the GalNAc-ASGPR pathway. The pharmacodynamic effect is dissociated from serum drug concentrations: the prolonged Lp(a) lowering reflects the intracellular persistence of the active RISC complex in hepatocytes rather than circulating drug exposure. The compound is well tolerated. In the OCEAN(a)-DOSE trial, the overall incidence of adverse events was similar in the olpasiran and placebo arms; the most frequently reported treatment-related adverse event was mild injection-site pain, which resolved without intervention [2]. No clinically significant changes in hepatic, renal, hematologic, or glycemic laboratory parameters were observed.

    Olpasiran is currently under evaluation in the Phase 3 OCEAN(a)-Outcomes trial (NCT05581303), a large cardiovascular outcomes study assessing the effect of olpasiran versus placebo on the composite endpoint of coronary heart disease death, myocardial infarction, or urgent coronary revascularization in participants with ASCVD and elevated Lp(a). An additional Phase 3 primary prevention trial, OCEAN(a)-PreEvent (NCT07136012), is evaluating olpasiran for prevention of first major cardiovascular events. The compound is not approved by any regulatory authority as of the date of this monograph. This document reviews the chemistry and structural class of olpasiran; the biology of lipoprotein(a) and the LPA gene target; the GalNAc-siRNA delivery mechanism; the preclinical pharmacology in transgenic mice and cynomolgus monkeys; the comprehensive human pharmacokinetic and pharmacodynamic record; the clinical evidence base from Phase 1 through Phase 3; sourcing and handling considerations for research applications; stack interactions; adverse events and safety signal; and a structured comparative assessment of five Lp(a)-lowering candidates against olpasiran on five competency standards.

    Read the full monograph

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

    KDC-MN-1626Open in new tab →

    Download PDF →

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

  • Tasimelteon

    Dual melatonin receptor agonist (MT1/MT2) with circadian rhythm entrainment activity

    A synthetic dihydrobenzofuran-cyclopropane melatonin receptor agonist developed at Bristol-Myers Squibb and advanced by Vanda Pharmaceuticals as the first FDA-approved pharmacotherapy for Non-24-Hour Sleep-Wake Disorder in totally blind individuals and for nighttime sleep disturbances in Smith-Magenis Syndrome.

    Abstract

    Tasimelteon (VEC-162, BMS-214778) is an orally active, selective dual agonist of the melatonin MT1 and MT2 G-protein-coupled receptors, approved by the United States Food and Drug Administration for the treatment of Non-24-Hour Sleep-Wake Disorder (Non-24) in totally blind individuals (January 2014) and for the treatment of nighttime sleep disturbances associated with Smith-Magenis Syndrome (December 2020). The compound is marketed by Vanda Pharmaceuticals under the trade name Hetlioz and was originally synthesized at Bristol-Myers Squibb as BMS-214778 before being licensed to Vanda in 2004 for clinical development. Tasimelteon is a circadian regulator that resets the master body clock in the suprachiasmatic nucleus of the hypothalamus by engaging both melatonin receptor subtypes, with approximately 2.1- to 4.4-fold greater affinity for the MT2 receptor (Ki approximately 0.07 to 0.17 nM) than for the MT1 receptor (Ki approximately 0.30 to 0.35 nM). The compound and its major metabolites have no appreciable affinity for more than 160 other pharmacologically relevant receptors, including gamma-aminobutyric acid, serotonin, noradrenaline, acetylcholine, dopamine, and opiate receptor systems, conferring a remarkably clean selectivity profile among circadian-active agents.

    The clinical evidence base for tasimelteon rests principally on two pivotal Phase 3 trials (SET and RESET), published in The Lancet in 2015, which demonstrated that 20 mg of oral tasimelteon administered nightly entrained the circadian pacemaker in totally blind individuals with Non-24 and that continued treatment was necessary to maintain entrainment. In the SET trial, tasimelteon achieved the co-primary endpoints of circadian entrainment of the melatonin rhythm and clinical response compared with placebo. In the RESET withdrawal trial, patients randomized to placebo after an entrainment run-in period showed significant deterioration in nighttime sleep, daytime sleep, and timing of sleep, while patients maintained on tasimelteon preserved their clinical benefit. A supplemental indication for Smith-Magenis Syndrome was approved in December 2020 based on a randomized, double-blind, placebo-controlled crossover study demonstrating improvement in nighttime sleep disturbances in both adults and children with this rare neurodevelopmental disorder characterized by an inverted circadian melatonin rhythm. A supplemental application for jet lag disorder has been twice rejected by the FDA (in 2019 and again in January 2026 upon re-review), despite court-ordered reconsideration by the DC Circuit Court of Appeals.

    Pharmacokinetics are characterized by rapid oral absorption (Tmax 0.5 to 3 hours), moderate oral bioavailability (approximately 38 percent), high plasma protein binding (approximately 90 percent), a short elimination half-life (1.3 hours), and extensive hepatic metabolism primarily through CYP1A2 and CYP3A4 oxidation pathways. The short half-life distinguishes tasimelteon from melatonin itself and from ramelteon and reflects the rapid clearance of the parent compound, with the chronobiotic effect being mediated by the timing of receptor occupancy rather than sustained plasma exposure. Eighty percent of an administered dose is recovered in urine as metabolites, with less than 1 percent excreted as unchanged parent compound. The five most abundant metabolites (M9, M11, M12, M13, M14) retain binding activity at the MT1 and MT2 receptors but at less than one-tenth the affinity of the parent compound. Clinically significant drug interactions include a 7-fold increase in exposure with fluvoxamine (a strong CYP1A2 inhibitor), a 90 percent decrease in exposure with rifampin (a strong CYP3A4 inducer), and an approximately 40 percent decrease in exposure in tobacco smokers (reflecting CYP1A2 induction). Elderly patients (older than 65 years) exhibit approximately 2-fold higher exposure than younger adults.

    This monograph reviews the chemistry, synthesis, and stereochemistry of tasimelteon; the dual melatonin receptor agonist pharmacology and circadian mechanism; the comprehensive human pharmacokinetic record including drug-drug interactions and special populations; the preclinical chronobiology; the clinical evidence base across Non-24, Smith-Magenis Syndrome, jet lag disorder, and insomnia indications; sourcing and quality verification for research applications; reconstitution and handling; stack-interaction considerations; adverse-event signal; and a structured comparative assessment of five melatonin receptor agonists and related circadian agents (ramelteon, prolonged-release melatonin, agomelatine, suvorexant, and melatonin) against tasimelteon on five competency standards (novelty, effect size, promising potential, side-effect profile, and overall validation).

    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-1629Open in new tab →

    Download PDF →

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

  • Efimosfermin

    Long-acting Fc-fusion fibroblast growth factor 21 (FGF21) analog with direct antifibrotic, anti-steatotic, and metabolic regulatory activity

    An engineered, once-monthly IgG1-Fc-fused FGF21 analog developed by Novartis and advanced through Boston Pharmaceuticals and GSK for the treatment of metabolic dysfunction-associated steatohepatitis, distinguished from other FGF21 analogs by a 21-day pharmacokinetic half-life that permits monthly subcutaneous dosing and by Phase 2 evidence of fibrosis reversal and MASH resolution in patients with moderate-to-advanced hepatic fibrosis.

    Abstract

    Efimosfermin alfa (formerly LLF580 under Novartis origination, subsequently designated BOS-580 under Boston Pharmaceuticals development, and now GSK-6519754 following acquisition by GSK plc) is a genetically engineered, long-acting analog of human fibroblast growth factor 21 (FGF21), a hepatokine and adipokine that regulates hepatic lipid oxidation, adipose tissue glucose uptake, triglyceride metabolism, and inflammatory signaling through formation of a ternary complex with the transmembrane tyrosine kinase FGF receptor 1c (FGFR1c) and the obligate co-receptor beta-klotho (KLB). The molecule is a homodimeric fusion protein in which two copies of a stabilized FGF21 variant are fused at their N-termini to the crystallizable fragment (Fc) of human immunoglobulin G1 (IgG1). The FGF21 domain is further stabilized by the introduction of a non-native disulfide bond and point mutations that increase proteolytic resistance, together producing a pharmacokinetic half-life of approximately 21 days in humans and enabling subcutaneous administration once every four weeks. This dosing interval distinguishes efimosfermin from the weekly-dosed FGF21 analogs efruxifermin (Akero Therapeutics) and pegozafermin (89bio), which require subcutaneous injection every one to two weeks.

    The compound entered clinical development as LLF580 in a Novartis-sponsored Phase 1/2 trial (CLLF580X2102) in obese adults with modest hypertriglyceridemia, where 300 mg subcutaneously every four weeks for 12 weeks produced a 54 percent reduction in serum triglycerides, a 36 percent increase in HDL cholesterol, a 52 percent reduction in hepatic fat fraction by magnetic resonance imaging-estimated proton density fat fraction (MRI-PDFF), a 24 percent reduction in pro-peptide type III collagen (Pro-C3, a circulating fibrosis biomarker), and improvements in insulin sensitivity (38 percent reduction in fasting insulin, 29 percent reduction in C-peptide, and a 103 percent increase in adiponectin), all without significant body weight change. The compound was subsequently licensed to Boston Pharmaceuticals, renamed BOS-580, and advanced into a Phase 2a multicenter randomized double-blind placebo-controlled trial in participants with phenotypic metabolic dysfunction-associated steatohepatitis (MASH), followed by a Phase 2b trial (NCT04880031) in 84 patients with biopsy-confirmed MASH and F2 or F3 fibrosis, where 300 mg once monthly for 24 weeks produced fibrosis improvement of at least one stage without MASH worsening in 45.2 percent of treated patients versus 20.6 percent on placebo (p = 0.038), MASH resolution without fibrosis worsening in 67.7 percent versus 29.4 percent on placebo (p < 0.01), and clinically meaningful improvements in glycemic control markers including glycated hemoglobin.

    In May 2025, GSK plc completed acquisition of efimosfermin from Boston Pharmaceuticals for 1.2 billion United States dollars upfront and up to 800 million dollars in milestone payments, with tiered royalties owed to Novartis Pharma AG. The compound has received United States Food and Drug Administration Breakthrough Therapy Designation and European Medicines Agency Priority Medicines (PRIME) Designation for the treatment of MASH. Phase 3 development (the ZENITH program) commenced in December 2025, with a potential first launch projected for 2029. GSK has indicated development plans in both MASH (including compensated cirrhosis) and alcohol-related liver disease (ALD), with potential for combination therapy with GSK’990, a complementary hepatology pipeline candidate. This monograph reviews the chemistry, molecular design, and receptor pharmacology of efimosfermin; the FGF21 signaling pathway; the comprehensive preclinical and clinical pharmacokinetic record; the clinical evidence base across Phase 1/2 and Phase 2 trials; the sourcing and quality considerations for this biologic investigational agent; reconstitution and handling; stack interactions and combinations; adverse events and safety signals; and a comparative assessment of five FGF21-pathway therapeutic candidates against efimosfermin on five competency standards.

    Read the full monograph

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

    KDC-MN-1631Open in new tab →

    Download PDF →

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

  • GT20029

    Topical proteolysis-targeting chimera (PROTAC) androgen receptor degrader

    A first-in-class topical PROTAC androgen receptor degrader developed by Kintor Pharmaceutical for androgenetic alopecia and acne vulgaris, distinguished from conventional antiandrogen therapies by catalytic, substoichiometric receptor protein elimination through the ubiquitin-proteasome system with negligible systemic exposure.

    Abstract

    GT20029 is a small-molecule proteolysis-targeting chimera (PROTAC) designed for topical application to skin and scalp, representing the first PROTAC compound to enter and complete clinical trials via the topical route of administration. Developed by Suzhou Kintor Pharmaceutical Ltd. on a proprietary PROTAC platform employing a novel cereblon (CRBN) E3 ubiquitin ligase recruiting element (the TD-106 scaffold), GT20029 functions as a bifunctional molecular bridge: one pharmacophore engages the androgen receptor (AR) ligand-binding domain, a chemical linker spans the two recruiting elements, and a second pharmacophore recruits the CRBN-containing Cullin-RING E3 ubiquitin ligase complex, resulting in polyubiquitination and proteasomal degradation of the AR protein [1, 2]. The catalytic mechanism permits each GT20029 molecule to cycle through multiple rounds of AR degradation, enabling pharmacologically effective AR elimination at low topical concentrations. In preclinical dihydrotestosterone (DHT)-induced mouse models, GT20029 significantly promoted hair regrowth and reversed follicular miniaturization; in testosterone propionate-induced hamster flank organ models, it significantly inhibited sebaceous gland enlargement, supporting the dual indication development for androgenetic alopecia (AGA) and acne vulgaris [3].

    Phase I clinical trials were completed in both China (92 subjects) and the United States (123 subjects) as randomized, double-blind, placebo-controlled studies with single ascending dose (SAD) and multiple ascending dose (MAD) cohorts. GT20029 demonstrated excellent safety and tolerability across all dose levels, with no systemic exposure above the lower limit of quantitation (0.003 ng/mL) in the SAD cohort and maximal plasma concentrations not exceeding 0.015 ng/mL after 14 days of continuous topical application in the MAD cohort, confirming that the compound acts locally with negligible systemic absorption [3]. The Phase II trial for AGA enrolled 180 male patients with Hamilton-Norwood grade IIIv to V pattern hair loss across 12 centers in China in a multicenter, randomized, double-blind, placebo-controlled design. Patients received GT20029 solution at 0.5% or 1.0% concentration, applied once daily (QD) or twice weekly (BIW), for 12 weeks. The primary endpoint was the change from baseline in non-vellus target area hair count (TAHC). The 0.5% QD group demonstrated an increase of 16.80 hairs per square centimeter, 6.69 hairs per square centimeter greater than placebo (P less than 0.05); the 1.0% BIW group demonstrated an increase of 11.94 hairs per square centimeter, 7.36 hairs per square centimeter greater than placebo (P less than 0.05) [4, 5]. Target area hair width also improved significantly in the 1.0% BIW group versus placebo. No adverse sexual events were observed in any treatment group, distinguishing GT20029 from systemic 5-alpha-reductase inhibitors. The Phase II trial for acne vulgaris, conducted across 10 centers in China, also met its primary endpoint for total lesion count reduction (excluding nodules) at the 0.5% QD dose (P = 0.01 versus placebo), with both 0.5% and 1.0% QD groups achieving highly significant reductions in inflammatory lesion counts (P less than 0.01) [6].

    On the basis of these results, Kintor has advanced GT20029 into Phase III clinical trials for male AGA in China and has initiated Phase II trials in the United States. The compound is not yet registered in any jurisdiction. The chemical structure of GT20029 has not been publicly disclosed; the molecular formula, molecular weight, and Chemical Abstracts Service registry number are not available in the public domain. This monograph reviews the available pharmacology, mechanism of action, preclinical and clinical evidence, pharmacokinetics, safety profile, handling considerations, and a comparative assessment of GT20029 against five alternative approaches to androgen-mediated dermatological conditions.

    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-1620Open in new tab →

    Download PDF →

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

  • Methallylescaline

    Substituted phenethylamine psychedelic of the scaline series; 5-HT2A receptor agonist and structural analog of mescaline

    A synthetic 4-methallyloxy-3,5-dimethoxyphenethylamine first characterized by Alexander Shulgin, distinguished from mescaline by approximately six-fold greater potency, prolonged duration of action, and a steep dose-response relationship attributable to enhanced lipophilicity and optimized 5-HT2A receptor engagement.

    Abstract

    Methallylescaline (MAL; 2-[3,5-dimethoxy-4-(2-methylprop-2-enoxy)phenyl]ethanamine) is a synthetic psychedelic phenethylamine of the scaline structural class, first synthesized and self-administered by Alexander Shulgin in the early 1980s and formally documented in entry number 99 of his 1991 reference work PiHKAL (Phenethylamines I Have Known and Loved). The compound is the 4-methallyloxy homolog of mescaline (3,4,5-trimethoxyphenethylamine), differing from the parent alkaloid by replacement of the 4-methoxy group with a 2-methylprop-2-enyloxy (methallyloxy) substituent. This structural modification increases lipophilicity, enhances blood-brain barrier permeability, and produces a compound with approximately six-fold greater potency than mescaline, an oral dose range of 40 to 65 milligrams (compared to 200 to 400 milligrams for mescaline), and a duration of action of 12 to 16 hours.

    The principal molecular target of methallylescaline is the serotonin 5-hydroxytryptamine type 2A (5-HT2A) receptor, at which the compound acts as an agonist to produce the characteristic psychedelic phenomenology of the phenethylamine class: visual distortion, perceptual intensification, synesthesia, and altered cognition. The compound also binds the 5-HT2C receptor and, at higher concentrations, the 5-HT1A receptor (Ki in the low micromolar range). The receptor interaction profile was formally characterized in the Kolaczynska, Luethi, Trachsel, Hoener, and Liechti (2022) systematic study of 4-alkoxy-3,5-dimethoxyphenethylamines (mescaline derivatives) and related amphetamines, which established that scalines as a class bind 5-HT2A and 5-HT2C receptors with affinities up to 63-fold and 34-fold greater than mescaline, respectively. The study further demonstrated that extending and branching the 4-alkoxy substituent increased binding affinity and activation potency at the 5-HT2A receptor while producing variable effects at the 5-HT2B receptor, a finding with implications for both potency and cardiovascular safety assessment.

    Pharmacokinetic data specific to methallylescaline in humans are absent from the peer-reviewed literature. Inferences drawn from mescaline pharmacokinetics (oral absorption with Tmax of approximately 2 hours, plasma half-life of approximately 3.5 hours, predominant elimination by oxidative deamination and renal excretion of unchanged drug) and from the structural properties of the methallyloxy substituent (increased lipophilicity, probable hepatic O-dealkylation to yield a demethylated phenolic metabolite) suggest that methallylescaline is rapidly absorbed, extensively distributed to central nervous system tissue, and eliminated over a time course consistent with its prolonged 12 to 16 hour subjective duration. The steep dose-response relationship reported by Shulgin, in which small increments in dose produce disproportionately large increases in effect intensity, is characteristic of agonists operating near the inflection point of a sigmoidal concentration-effect curve and may reflect cooperative receptor binding or threshold-dependent downstream signaling amplification.

    Preclinical pharmacology data for methallylescaline are limited. The Halberstadt, Chatha, Chapman, and Brandt (2019) study of the mouse head-twitch response (a 5-HT2A receptor-mediated behavioral proxy for psychedelic potency) characterized several mescaline analogs in the scaline series and established the general principle that extension of the 4-alkoxy chain increases in vivo potency relative to mescaline. No clinical trials, controlled human pharmacology studies, or formal toxicology assessments of methallylescaline have been conducted. The compound has no approved medical indication in any jurisdiction.

    This monograph documents the chemistry, synthesis, structural class, and nomenclature of methallylescaline; the receptor pharmacology as characterized in the Kolaczynska et al. (2022) systematic study; inferred pharmacokinetics based on the mescaline pharmacokinetic record and structural analogy; preclinical pharmacology from the scaline head-twitch response literature; the absence of clinical evidence; sourcing and quality verification considerations; reconstitution and handling; stack interaction considerations; adverse events and safety signal; and a comparative assessment of five structurally or mechanistically related phenethylamine psychedelics (mescaline, escaline, allylescaline, proscaline, and 3C-E) against methallylescaline on five competency standards.

    Read the full monograph

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

    KDC-MN-1639Open in new tab →

    Download PDF →

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

  • Elinzanetant

    Dual neurokinin-1 (NK1) and neurokinin-3 (NK3) receptor antagonist for non-hormonal treatment of menopausal vasomotor symptoms

    A non-hormonal, orally bioavailable dual NK1/NK3 receptor antagonist developed through GlaxoSmithKline, NeRRe Therapeutics, KaNDy Therapeutics, and Bayer for the treatment of moderate-to-severe vasomotor symptoms associated with menopause, distinguished from selective NK3 antagonists by concurrent blockade of substance P signaling and consequent additive benefits on sleep, mood, and thermoregulatory dysregulation.

    Abstract

    Elinzanetant (Lynkuet; BAY3427080; formerly NT-814 and GSK1144814) is a potent and selective dual antagonist of the neurokinin-1 (NK1) and neurokinin-3 (NK3) receptors, developed for the non-hormonal treatment of moderate-to-severe vasomotor symptoms (VMS) associated with menopause and with endocrine therapy for hormone receptor-positive breast cancer. The compound received its first regulatory approval in the United Kingdom in July 2025, followed by approvals in Australia, Canada, Switzerland, and the United States, where it was approved by the Food and Drug Administration on October 24, 2025, under the trade name Lynkuet at a recommended dose of 120 mg orally once daily at bedtime. Elinzanetant is the first and only approved dual NK1/NK3 receptor antagonist, mechanistically distinct from fezolinetant (Veozah), which acts solely on the NK3 receptor. The dual mechanism targets kisspeptin/neurokinin B/dynorphin (KNDy) neurons in the hypothalamic arcuate nucleus, where neurokinin B (NKB) acting through NK3 receptors initiates thermoregulatory dysregulation responsible for hot flashes, and substance P (SP) acting through NK1 receptors amplifies KNDy neuronal activity and contributes to sleep disruption, mood disturbance, and peripheral vasodilation. By antagonizing both receptor subtypes, elinzanetant addresses the composite symptom burden of menopause rather than isolated hot flash frequency alone. The compound exhibits high affinity for human NK1 receptors (pKi 8.7 to 10.2) and NK3 receptors (pKi 8.0 to 8.8), with greater than 300-fold selectivity for NK1 and greater than 100-fold selectivity for NK3 over off-target receptors. Pharmacokinetics are characterized by rapid oral absorption (median Tmax approximately 1 hour), absolute oral bioavailability of 52 percent, extensive plasma protein binding (99.7 percent), a large volume of distribution (137 L), and a long elimination half-life of approximately 45 hours that supports once-daily dosing. Metabolism is predominantly CYP3A4-mediated, producing three active metabolites with comparable NK1/NK3 potency at approximately 39 percent of parent plasma exposure. Excretion is predominantly fecal (90 percent as metabolites). The clinical evidence base comprises the OASIS Phase 3 program: OASIS 1 and OASIS 2 (12-week placebo-controlled studies in approximately 400 postmenopausal women each), OASIS 3 (52-week long-term study in 628 women), and OASIS 4 (12-week study in women receiving breast cancer endocrine therapy). All trials met primary endpoints, demonstrating statistically significant and clinically meaningful reductions in VMS frequency and severity at weeks 4 and 12, with onset of effect as early as week 1. Secondary endpoints showed significant improvements in sleep disturbances, menopause-related quality of life, and mood. Long-term efficacy was maintained through 52 weeks in OASIS 3 with no signal of hepatotoxicity, endometrial hyperplasia, or endometrial malignancy. The most common adverse events are headache (7.8 percent) and fatigue (5 percent). Elinzanetant is contraindicated in pregnancy, in severe hepatic impairment, and with concomitant strong CYP3A4 inhibitors. This monograph reviews the chemistry, synthesis, and stereochemistry of elinzanetant; the dual-receptor pharmacology in molecular and neurophysiological detail; the comprehensive human pharmacokinetic record; the clinical evidence base across the OASIS program and the dose-finding SWITCH-1 study; sourcing and quality verification considerations; reconstitution and handling; stack-interaction considerations for research applications; the adverse-event and safety signal profile; and a comparative assessment of five alternative compounds for vasomotor symptom management against elinzanetant on five competency standards.

    Read the full monograph

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

    KDC-MN-1627Open in new tab →

    Download PDF →

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

  • LDN-193189

    Selective bone morphogenetic protein (BMP) type I receptor kinase inhibitor targeting ALK2 and ALK3

    A pyrazolopyrimidine-scaffold small molecule derived from dorsomorphin structure-activity optimization, selectively inhibiting BMP type I receptor kinases ALK2 and ALK3 at low-nanomolar potency with 200-fold selectivity over TGF-beta signaling, and widely adopted as a research tool for BMP pathway dissection, directed stem cell differentiation, and preclinical modeling of fibrodysplasia ossificans progressiva and diffuse intrinsic pontine glioma.

    Abstract

    LDN-193189 (DM-3189; CAS 1062368-24-4) is a cell-permeable, small-molecule inhibitor of bone morphogenetic protein (BMP) type I receptor serine/threonine kinases, developed through structure-activity relationship optimization of dorsomorphin at the Brigham and Women’s Hospital and Harvard Medical School laboratories of Paul B. Yu. The compound inhibits activin receptor-like kinase 2 (ALK2, also designated ACVR1) with an IC50 of approximately 5 nM and activin receptor-like kinase 3 (ALK3, also designated BMPR1A) with an IC50 of approximately 30 nM, while exhibiting approximately 200-fold selectivity for BMP receptors over the transforming growth factor-beta (TGF-beta) type I receptor ALK5 and negligible activity against ALK4 and ALK7 at concentrations below 500 nM. The mechanism of action involves competitive binding at the ATP-binding pocket of BMP type I receptor kinases, preventing receptor autophosphorylation and blocking downstream phosphorylation of the canonical signaling effectors Smad1, Smad5, and Smad8. In addition to canonical Smad pathway inhibition, LDN-193189 suppresses BMP-induced non-canonical signaling through the p38 mitogen-activated protein kinase (MAPK) and Akt (protein kinase B) pathways, providing broader coverage of BMP-dependent intracellular signaling than Smad-selective interventions alone.

    The compound originated from the 2008 Cuny, Yu, and colleagues structure-activity relationship study that optimized the pyrazolo[1,5-a]pyrimidine scaffold of dorsomorphin, a compound itself discovered in 2008 by Yu et al. through a phenotypic zebrafish embryo screen of approximately 7,500 bioactive compounds for agents that could dorsalize the developing embryo and thereby phenocopy loss-of-function mutations in the BMP signaling pathway. Dorsomorphin, while the first small-molecule BMP pathway inhibitor identified, exhibited substantial off-target activity against AMP-activated protein kinase (AMPK), vascular endothelial growth factor receptor 2 (VEGFR2), and platelet-derived growth factor receptor (PDGFR), limiting its utility as a selective BMP pathway probe. LDN-193189 retained the central pyrazolopyrimidine core but incorporated a quinoline moiety and a piperazinylphenyl substituent that conferred markedly improved potency and selectivity for BMP type I receptors over the off-target kinases that compromised dorsomorphin’s pharmacological profile.

    LDN-193189 has become one of the most widely used pharmacological tools for interrogating BMP signaling in developmental biology, stem cell biology, and disease modeling. In stem cell biology, the compound is a core component of the dual SMAD inhibition protocol (in combination with the TGF-beta/Activin/Nodal inhibitor SB431542) developed by Chambers et al. (2009) for the efficient directed differentiation of human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) toward neuroectodermal and neural progenitor fates, a protocol that has become the standard method for generating central nervous system neurons from human pluripotent stem cells. In disease modeling, the compound has been extensively characterized in preclinical models of fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder caused by gain-of-function mutations in the ACVR1/ALK2 gene that produce constitutive BMP pathway activation and progressive heterotopic ossification of soft tissues. Treatment of mice expressing constitutively active ALK2 with LDN-193189 reduced heterotopic bone formation in the landmark Yu et al. (2008) Nature Medicine study. The compound has also demonstrated preclinical efficacy in orthotopic xenograft models of diffuse intrinsic pontine glioma (DIPG) harboring ACVR1 mutations, extending survival in treated animals. Additional research applications span iron metabolism and hepcidin regulation (through BMP6-dependent Smad signaling in hepatocytes), pulmonary arterial hypertension modeling, chondrogenesis and osteogenesis research, and cancer biology.

    LDN-193189 has not entered human clinical trials and is not a registered medicine in any jurisdiction. The compound is classified as a research tool and is supplied by multiple commercial vendors (Selleck Chemicals, MedChemExpress, Cayman Chemical, Tocris, Sigma-Aldrich, Stemgent/REPROCELL, and others) as the free base or hydrochloride salt at greater than 98 percent purity. In vivo pharmacokinetic characterization in mice has demonstrated oral bioavailability and brain penetration sufficient for central nervous system target engagement, though metabolic liabilities including aldehyde oxidase-dependent metabolism and generation of reactive piperazinyl iminium intermediates have been identified as concerns for clinical translation and have motivated the development of next-generation analogs (LDN-212854, LDN-214117, ML347, DMH1, K02288) with improved selectivity or metabolic profiles. This monograph reviews the chemistry, synthesis, and structural pharmacology of LDN-193189; the molecular mechanism of BMP type I receptor kinase inhibition; the preclinical pharmacology across FOP, DIPG, stem cell, iron metabolism, and cancer applications; the pharmacokinetic and metabolic characterization; sourcing, reconstitution, and handling; stack interactions with other signaling pathway modulators; the adverse-event and safety signal from preclinical studies; and a comparative assessment of five alternative BMP pathway inhibitors against LDN-193189 on five competency standards.

    Read the full monograph

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

    KDC-MN-1638Open in new tab →

    Download PDF →

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

  • Levosimendan

    Calcium sensitizer with phosphodiesterase III inhibition and ATP-sensitive potassium channel activation

    A pyridazinone-dinitrile inodilator developed at Orion Corporation as a calcium-sensitizing positive inotrope for acutely decompensated heart failure, distinguished from conventional inotropes by its ability to enhance myocardial contractility without increasing intracellular calcium concentration or myocardial oxygen consumption, and by its long-lived active metabolite OR-1896 that sustains hemodynamic effects for days beyond infusion cessation.

    Abstract

    Levosimendan, the (R)-enantiomer of simendan, is a pyridazinone-derivative calcium sensitizer and positive inotropic agent developed by Orion Corporation (Finland) and approved in approximately 60 countries for the short-term treatment of acutely decompensated severe chronic heart failure in situations where conventional therapy is not considered adequate. The compound exerts its principal pharmacological effects through three complementary mechanisms: calcium-dependent binding to the N-terminal domain of cardiac troponin C, which stabilizes the calcium-troponin C interaction and enhances myofilament sensitivity to calcium without increasing intracellular calcium concentration; selective inhibition of phosphodiesterase III (PDE3) in cardiac and vascular smooth muscle, which elevates cyclic adenosine monophosphate and contributes to positive inotropy and vasodilation; and opening of ATP-sensitive potassium channels (both sarcolemmal and mitochondrial) in vascular smooth muscle and cardiomyocytes, producing peripheral and coronary vasodilation and conferring cardioprotective effects against ischemia-reperfusion injury. The composite pharmacology produces the characteristic inodilator profile: simultaneous enhancement of cardiac contractility, reduction of cardiac preload and afterload, and improvement in coronary perfusion, all achieved without a proportional increase in myocardial oxygen demand.

    The pharmacokinetic profile of levosimendan is distinguished by the formation of an active metabolite, OR-1896, through intestinal reduction of the parent compound to the amino-derivative OR-1855 followed by hepatic N-acetylation. OR-1896 exhibits calcium-sensitizing and PDE3-inhibitory activity comparable to the parent compound and possesses an elimination half-life of approximately 75 to 80 hours in heart failure patients, compared to approximately 1 hour for the parent. This metabolite formation pathway introduces N-acetyltransferase 2 (NAT2) acetylator phenotype as a determinant of OR-1896 exposure, with slow acetylators demonstrating lower OR-1896 concentrations and potentially diminished sustained hemodynamic effects. The prolonged activity of OR-1896 sustains hemodynamic improvement for 7 to 9 days following cessation of a standard 24-hour intravenous infusion, a property unique among clinically available inotropic agents.

    The clinical evidence base comprises six principal Phase II and Phase III randomized controlled trials (LIDO, RUSSLAN, CASINO, REVIVE-I, REVIVE-II, SURVIVE) enrolling more than 3,000 patients with acute decompensated heart failure, supplemented by extensive registry data, meta-analyses, and ongoing investigation in cardiac surgery, cardiogenic shock, septic cardiomyopathy, pulmonary hypertension, right ventricular failure, and advanced heart failure with intermittent ambulatory infusion protocols. The LIDO trial demonstrated hemodynamic superiority and a 31-day survival advantage over dobutamine. The SURVIVE trial, the largest randomized comparison (1,327 patients), demonstrated superior reduction in B-type natriuretic peptide but did not achieve the primary endpoint of reduced 180-day all-cause mortality compared to dobutamine, though subgroup analyses favored levosimendan in patients on chronic beta-blocker therapy and those with prior heart failure history. Levosimendan is marketed as Simdax (Orion Corporation) and is not approved by the United States Food and Drug Administration; the original new drug application was withdrawn in 1999 following a request for additional trials. This monograph reviews the chemistry and stereochemistry, the triple-mechanism molecular pharmacology, the unique metabolite-driven pharmacokinetic profile, the comprehensive clinical evidence base, sourcing considerations, reconstitution and handling, drug interactions, adverse events, and a comparative assessment against five alternative inotropic agents on five competency standards.

    Read the full monograph

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

    KDC-MN-1623Open in new tab →

    Download PDF →

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

  • Pegozafermin

    GlycoPEGylated fibroblast growth factor 21 (FGF21) analog with extended half-life for metabolic and hepatic disease

    A long-acting glycoPEGylated analog of fibroblast growth factor 21 engineered to recapitulate the endocrine metabolic activity of native FGF21, developed by 89bio for the treatment of metabolic dysfunction-associated steatohepatitis and severe hypertriglyceridemia.

    Abstract

    Pegozafermin (BIO89-100) is a glycoPEGylated recombinant analog of human fibroblast growth factor 21 (FGF21), a hepatokine central to the regulation of lipid metabolism, glucose homeostasis, and energy expenditure. The compound was engineered using site-specific glycosylation and PEGylation to extend the circulating half-life from approximately 0.5 to 2 hours (native FGF21) to 55 to 100 hours, enabling once-weekly or once-every-two-week subcutaneous administration while preserving the receptor binding profile of the native hormone. Pegozafermin signals through the FGF receptor 1c (FGFR1c) and FGF receptor 3c in complex with the obligate coreceptor beta-klotho (KLB), activating the extracellular signal-regulated kinase 1/2 (ERK1/2) cascade and downstream transcription factors that govern hepatic de novo lipogenesis, adipose tissue adiponectin secretion, fatty acid oxidation, and insulin sensitivity. The compound was originally developed by Teva Pharmaceutical Industries and subsequently licensed to 89bio, Inc. in 2019 for global development (excluding Israel).

    In the Phase 2b ENLIVEN trial (Loomba et al., 2023, New England Journal of Medicine), 222 patients with biopsy-confirmed nonalcoholic steatohepatitis (NASH) and stage F2 or F3 fibrosis were randomized to pegozafermin 15 mg weekly, 30 mg weekly, 44 mg every two weeks, or placebo for 24 weeks. The co-primary histological endpoints were met at both the 30 mg weekly and 44 mg every-two-week doses: fibrosis improvement of at least one stage without worsening of steatohepatitis was achieved in 26 percent and 27 percent of treated patients, respectively, compared with 7 percent on placebo. NASH resolution without fibrosis worsening was achieved in 23 percent and 26 percent, respectively, compared with 2 percent on placebo. Hepatic fat fraction measured by magnetic resonance imaging proton density fat fraction (MRI-PDFF) decreased by 48.2 percent (30 mg weekly) and 41.9 percent (44 mg every two weeks) versus 5.0 percent on placebo. Alanine aminotransferase levels normalized in 59 to 65 percent of treated patients versus 24 percent on placebo, and the fibrosis biomarker PRO-C3 decreased by 17 to 18 percent versus a 6.4 percent increase on placebo.

    In the Phase 2 ENTRIGUE trial in severe hypertriglyceridemia (Bhatt et al., 2023, Nature Medicine), pegozafermin at doses of 9 to 27 mg weekly or 36 mg every two weeks produced a pooled median triglyceride reduction of 57.3 percent versus 11.9 percent on placebo, with 79.7 percent of treated patients achieving triglycerides below 500 mg/dL compared with 29.4 percent on placebo. Secondary lipid endpoints included reductions in non-HDL cholesterol (18.3 percent), apolipoprotein B (10.5 percent), apolipoprotein C3 (41.9 percent), and increases in HDL cholesterol of up to 44.5 percent at the 27 mg weekly dose.

    Safety across both trials was characterized by mild-to-moderate gastrointestinal adverse events (nausea, diarrhea) and injection site reactions. No hepatotoxicity, drug-induced liver injury, or clinically significant bone density changes were observed. One treatment-related serious adverse event (acute pancreatitis in a patient with gallbladder sludge) was reported in the ENLIVEN trial.

    Pegozafermin received Breakthrough Therapy designation from the United States Food and Drug Administration and Priority Medicines (PRIME) designation from the European Medicines Agency for the treatment of MASH with fibrosis in September 2023. The compound is currently in Phase 3 development in the ENLIGHTEN program (MASH with fibrosis and compensated cirrhosis) and the ENTRUST program (severe hypertriglyceridemia). This monograph reviews the compound identification, discovery and development history, molecular pharmacology of the FGF21 signaling axis, pharmacokinetics, preclinical pharmacology, clinical evidence base, sourcing and quality verification, reconstitution and handling, stack interactions and combinations, adverse events and safety signal, and a comparative assessment of five alternative metabolic liver disease candidates against pegozafermin on five competency standards.

    Read the full monograph

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

    KDC-MN-1630Open in new tab →

    Download PDF →

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