Tag: NOVEL

  • ANAVEX 3-71

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

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

    Abstract

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

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  • Tofersen

    Antisense oligonucleotide targeting SOD1 mRNA via RNase H-dependent degradation for SOD1-associated amyotrophic lateral sclerosis

    A 2′-O-methoxyethyl gapmer antisense oligonucleotide developed by Ionis Pharmaceuticals and Biogen for intrathecal reduction of SOD1 protein in genetically defined SOD1-associated amyotrophic lateral sclerosis, the first gene-targeted therapy approved for any form of ALS.

    Abstract

    Tofersen (BIIB067, marketed as Qalsody) is a 20-base 2′-O-methoxyethyl (MOE) gapmer antisense oligonucleotide that binds to and mediates RNase H-dependent degradation of superoxide dismutase 1 (SOD1) messenger RNA, reducing synthesis of both mutant and wild-type SOD1 protein in the central nervous system. Developed by Ionis Pharmaceuticals and licensed to Biogen, tofersen received accelerated approval from the United States Food and Drug Administration on April 25, 2023, for the treatment of amyotrophic lateral sclerosis (ALS) in adults with a confirmed SOD1 gene mutation, making it the first gene-targeted therapy approved for any form of ALS. Subsequent approvals followed from the European Medicines Agency (May 30, 2024), the Therapeutic Goods Administration of Australia (January 5, 2025), and Health Canada (March 3, 2025). SOD1 mutations, first identified in familial ALS by Rosen et al. in 1993, account for approximately 13 to 20 percent of familial ALS cases and 1 to 2 percent of sporadic ALS cases. Over 200 pathogenic SOD1 variants have been reported, producing a spectrum of disease phenotypes from rapidly progressive (p.A5V, median survival approximately 1 year from onset) to slowly progressive (p.D91A homozygous, median survival exceeding 10 years). The pathogenic mechanism is a toxic gain of function in which mutant SOD1 protein undergoes misfolding, aggregation, and formation of cytoplasmic inclusions in motor neurons and astrocytes, driving neurodegeneration through oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, and impaired protein degradation. Tofersen addresses this mechanism directly by reducing the concentration of the causative toxic protein. The clinical development program comprises a Phase 1-2 ascending-dose trial (50 participants) establishing dose-dependent CSF SOD1 reduction of up to 36 percent at the 100 mg intrathecal dose; the Phase 3 VALOR trial (108 participants) that did not meet its primary efficacy endpoint of change in the ALS Functional Rating Scale-Revised (ALSFRS-R) at 28 weeks (difference 1.2 points, p = 0.97) but demonstrated robust reductions in CSF SOD1 protein (29 percent) and plasma neurofilament light chain (60 percent); and an open-label extension demonstrating that participants who initiated tofersen early had a statistically significant 3.5-point advantage on ALSFRS-R decline compared with those whose treatment was delayed (p = 0.03 at 52 weeks). Accelerated approval was based on the reduction in plasma neurofilament light chain as a surrogate endpoint reasonably likely to predict clinical benefit. The ongoing ATLAS trial (NCT04856982) evaluates tofersen initiation in presymptomatic SOD1 variant carriers using plasma neurofilament light chain as a biomarker trigger for randomization. Tofersen is administered intrathecally at a dose of 100 mg in 15 mL, with three loading doses at 14-day intervals followed by maintenance doses every 28 days. The estimated CSF half-life is approximately four weeks, and elimination occurs through exonuclease-mediated hydrolysis without cytochrome P450 involvement. The principal adverse events are procedure-related (pain, headache) and drug-related (CSF pleocytosis in 42 percent of treated participants, fatigue, arthralgia, myalgia). Serious neurologic adverse events including myelitis, radiculitis, papilledema with elevated intracranial pressure, and aseptic meningitis have been reported in approximately 7 percent of tofersen-treated participants. This monograph reviews the chemistry, development history, molecular mechanism, pharmacokinetics, preclinical and clinical evidence, sourcing and handling, adverse event profile, and a comparative assessment of five alternative ALS therapeutic agents against tofersen.

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  • CAD-31

    Trifluoroacetyl hydrazone geroneuroprotector with AMPK-mediated neuroprotective and neurogenic activity

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

    Abstract

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

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  • Traxoprodil

    NR2B subunit-selective N-methyl-D-aspartate receptor antagonist

    A second-generation phenylethanol amine ifenprodil derivative developed at Pfizer as a forebrain-selective neuroprotectant, distinguished from first-generation NR2B antagonists by absence of alpha-1 adrenergic receptor activity and clinically evaluated in traumatic brain injury, treatment-resistant major depression, and levodopa-induced dyskinesia in Parkinson’s disease.

    Abstract

    Traxoprodil (CP-101,606) is a potent and selective antagonist of N-methyl-D-aspartate (NMDA) receptors containing the NR2B (GluN2B) subunit, originally synthesized at the Central Research Division of Pfizer Inc. in Groton, Connecticut, and first disclosed by Chenard et al. in 1995 as a neuroprotectant with high selectivity for forebrain neurons. Structurally a substituted 4-phenylpiperidine and single-isomer phenylethanol amine derivative of the first-generation NR2B antagonist ifenprodil, traxoprodil retains the high-affinity NR2B binding (KD of 4.2 nanomolar in adult rodent forebrain) while eliminating the alpha-1 adrenergic receptor activity that limited the clinical utility of its predecessor. The compound binds at the amino-terminal domain interface of the NR1/NR2B heterodimer and inhibits channel opening by enhancing tonic proton inhibition, a mechanism formally characterized by Mott et al. (1998) that distinguishes the phenylethanol amine class from channel-blocking NMDA antagonists such as ketamine and memantine. Pharmacokinetics in humans are dominated by hepatic cytochrome P450 2D6 (CYP2D6) metabolism, producing a striking polymorphic phenotype: in CYP2D6 extensive metabolizers, the oral bioavailability at a 100 mg dose is approximately 39.5 percent with a plasma elimination half-life of 2 to 4 hours, whereas in poor metabolizers the bioavailability approaches 80 percent with a half-life of approximately 20 hours. The nonlinear, dose-dependent oral pharmacokinetics in extensive metabolizers reflect saturation of hepatic first-pass CYP2D6 metabolism; at high oral doses the impact of CYP2D6 polymorphism on exposure diminishes as the enzyme saturates. The compound was advanced through three principal clinical programs. In traumatic brain injury, an open-label study of 30 patients with severe head injury or spontaneous intracerebral hemorrhage demonstrated safety, tolerability, and 80 percent good recovery at 3 months; a subsequent randomized, double-blind, placebo-controlled Phase 2/3 trial of 404 severe TBI patients showed trends toward improved functional outcome (7.5 percent improvement on the dichotomized Glasgow Outcome Scale, p = 0.07) and reduced mortality (7 percent difference, p = 0.08) but did not reach conventional statistical significance. In treatment-resistant major depression, a randomized, double-blind, placebo-controlled proof-of-concept trial of 30 paroxetine-nonresponders demonstrated a 60 percent response rate on the Hamilton Depression Rating Scale after a single intravenous infusion of CP-101,606 versus 20 percent on placebo, with 78 percent of responders maintaining response for at least one week, and without dissociative side effects. In Parkinson’s disease, a double-blind crossover trial in 12 patients showed approximately 30 percent reduction in levodopa-induced dyskinesia but dose-dependent dissociative and amnestic adverse events. Clinical development was ultimately discontinued due to cardiovascular safety concerns, specifically QTc interval prolongation attributed to inhibition of the human ether-a-go-go-related gene (hERG) potassium channel, a liability that Pfizer determined precluded further advancement. This monograph reviews the chemistry and stereochemistry of traxoprodil; the NR2B-selective pharmacology including the proton-enhancing mechanism and the two-class distinction among NR2B antagonists; the comprehensive CYP2D6-dependent human pharmacokinetics; the preclinical neuroprotection, antinociception, antiparkinsonian, and antidepressant pharmacology; the clinical evidence across traumatic brain injury, treatment-resistant depression, and Parkinson’s disease; and a comparative assessment of five NR2B-selective or NMDA-targeting compounds (rislenemdaz, ifenprodil, Ro 25-6981, radiprodil, and ketamine) against traxoprodil on five competency standards. The compound is not approved by any regulatory authority for any indication. It is available as a research-grade preparation; investigators should obtain analytical confirmation of identity and purity on every lot.

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  • 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.

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  • Resmetirom

    Liver-directed, beta-selective thyroid hormone receptor agonist (thyromimetic)

    A first-in-class, orally administered, hepatocyte-targeted partial agonist of thyroid hormone receptor beta developed by Madrigal Pharmaceuticals for the treatment of metabolic dysfunction-associated steatohepatitis with liver fibrosis, and the first pharmacotherapy approved by the United States Food and Drug Administration for this indication.

    Abstract

    Resmetirom (MGL-3196, VIA-3196; marketed as Rezdiffra) is a first-in-class, orally administered, small-molecule, liver-directed partial agonist of the thyroid hormone receptor beta (THR-beta) that received accelerated approval from the United States Food and Drug Administration on March 14, 2024, for the treatment of adults with noncirrhotic metabolic dysfunction-associated steatohepatitis (MASH, formerly nonalcoholic steatohepatitis or NASH) with moderate to advanced liver fibrosis (stages F2 to F3), in conjunction with diet and exercise. Resmetirom is distinguished from earlier thyromimetic compounds by approximately 28-fold functional selectivity for THR-beta over THR-alpha, hepatocyte-directed uptake mediated by organic anion transporting polypeptide 1B1 (OATP1B1), and a liver-to-plasma concentration ratio of approximately 8:1, properties that collectively minimize the extrahepatic thyrotoxic effects (tachycardia, bone loss, skeletal muscle wasting) that terminated development of prior thyroid hormone receptor agonists including eprotirome and sobetirome. The molecular mechanism involves activation of THR-beta in hepatocytes, promoting fatty acid beta-oxidation, mitochondrial biogenesis, mitophagy, and autophagy while inhibiting de novo lipogenesis; these effects reduce intrahepatic triglyceride accumulation and attenuate the inflammatory and fibrotic cascades characteristic of progressive steatohepatitis. In the pivotal Phase 3 MAESTRO-NASH trial (n = 888, biopsy-confirmed noncirrhotic MASH with F2 to F3 fibrosis), resmetirom at 100 mg daily achieved MASH resolution without fibrosis worsening in 36 percent of patients versus 13 percent on placebo at 52 weeks, and fibrosis improvement by at least one stage without worsening of MASH activity in 28 percent versus 15 percent on placebo, both co-primary endpoints reaching statistical significance. Secondary endpoints demonstrated reductions in low-density lipoprotein cholesterol (16.3 percent), apolipoprotein B (16.5 percent), and triglycerides (23.4 percent), consistent with the hepatic metabolic mechanism. Pharmacokinetics are characterized by oral absorption with a median time to peak concentration of approximately 4 hours, greater than 99 percent plasma protein binding, a median terminal half-life of 4.5 hours, metabolism predominantly through cytochrome P450 2C8 (CYP2C8), and elimination principally via feces (67 percent) with a minor renal component (24 percent). The principal adverse events are diarrhea and nausea, which are generally mild to moderate and self-limiting. Clinically significant drug interactions include inhibition of organic anion transporting polypeptide transporters (elevating statin exposures) and CYP2C8-mediated metabolic interactions. This monograph reviews the chemistry, synthesis, and structural pharmacology of resmetirom; the thyroid hormone receptor biology and mechanism of action in detail; the comprehensive human pharmacokinetic record; the preclinical pharmacology; the clinical evidence base across the MAESTRO trial program; sourcing and quality verification for research-grade material; reconstitution and handling; stack-interaction considerations; adverse-event signal and safety profile; and a comparative assessment of five alternative MASH pharmacotherapy candidates against resmetirom on five competency standards.

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  • Saroglitazar

    Dual peroxisome proliferator-activated receptor alpha/gamma (PPARalpha/gamma) agonist with predominant PPARalpha activity

    A first-in-class dual PPARalpha/gamma agonist developed by Zydus Cadila as the first new chemical entity discovered and approved in India, indicated for diabetic dyslipidemia and non-cirrhotic non-alcoholic steatohepatitis, and under clinical investigation for primary biliary cholangitis and metabolic dysfunction-associated steatotic liver disease in the United States.

    Abstract

    Saroglitazar, the magnesium salt of (2S)-2-ethoxy-3-[4-(2-{2-methyl-5-[4-(methylsulfanyl)phenyl]-1H-pyrrol-1-yl}ethoxy)phenyl]propanoic acid, is a first-in-class dual agonist of peroxisome proliferator-activated receptors alpha and gamma (PPARalpha/gamma) with predominant PPARalpha and moderate PPARgamma activity. Developed by Zydus Cadila (now Zydus Lifesciences) under the development code ZYH1, it was the first new chemical entity discovered entirely in India to receive marketing authorization, granted in 2013 by the Drug Controller General of India for the treatment of diabetic dyslipidemia and hypertriglyceridemia in patients with type 2 diabetes mellitus not controlled by statins alone. In 2020, saroglitazar received a second indication in India for the treatment of non-cirrhotic non-alcoholic steatohepatitis (NASH), making it the first drug approved anywhere in the world for that condition. The compound is marketed in India as Lipaglyn at an oral dose of 4 mg once daily and has subsequently received approval in Mexico.

    The dual PPARalpha/gamma mechanism provides a pharmacological profile that bridges the lipid-lowering activity of fibrates (PPARalpha agonists) with the insulin-sensitizing activity of thiazolidinediones (PPARgamma agonists) while avoiding the weight gain, edema, and cardiovascular risk signals that led to the withdrawal of earlier glitazar-class compounds (muraglitazar, tesaglitazar, ragaglitazar). PPARalpha activation increases hepatic fatty acid beta-oxidation, reduces triglyceride synthesis, and elevates high-density lipoprotein cholesterol. PPARgamma activation enhances peripheral insulin sensitivity in adipose and skeletal muscle tissue, reduces hepatic gluconeogenesis, and modulates adipokine secretion. The dual activation also provides anti-inflammatory and antifibrotic effects in the liver through suppression of nuclear factor kappa B signaling, reduction of pro-inflammatory cytokines (tumor necrosis factor alpha, interleukin-6, interleukin-1 beta), and modulation of the leptin-to-adiponectin ratio.

    Pharmacokinetics in healthy human subjects are characterized by rapid oral absorption (median time to peak plasma concentration of 0.6 to 1.0 hours under fasting conditions), extensive plasma protein binding (approximately 96 percent), hepatic metabolism to saroglitazar sulfoxide and other metabolites, and a terminal elimination half-life of approximately 3 to 6 hours depending on sex and formulation. The compound does not accumulate on repeated once-daily dosing, and food does not meaningfully affect overall systemic exposure. The pharmacokinetic profile has been characterized in healthy volunteers, in patients with hepatic impairment (including cholestatic cirrhosis), and in patients with renal impairment.

    The clinical evidence base spans multiple Phase 2 and Phase 3 programs. The PRESS series of trials (PRESS I through PRESS VIII) established efficacy in diabetic dyslipidemia and hypertriglyceridemia, demonstrating non-inferiority to fenofibrate for triglyceride reduction and superiority to pioglitazone for lipid parameter improvement. The EVIDENCES series of trials evaluated saroglitazar in non-alcoholic fatty liver disease (NAFLD) and NASH, with the EVIDENCES II Phase 3 trial in India demonstrating significant histological improvement at 52 weeks. A US-based Phase 2 trial (Gawrieh et al. 2021) in 106 patients with biopsy-proven NASH demonstrated significant improvement in NAFLD activity score, liver enzymes, and lipid parameters at 16 weeks. In primary biliary cholangitis (PBC), the Phase 2 proof-of-concept study demonstrated a 49 to 51 percent reduction in alkaline phosphatase at 16 weeks in ursodeoxycholic acid-resistant or -intolerant patients, and the Phase IIb/III EPICS-III trial met its primary and secondary endpoints; regulatory submission to the United States Food and Drug Administration for this indication is anticipated in the first quarter of 2026. The compound has received orphan drug designation and Fast Track designation from the FDA for PBC.

    Saroglitazar is well tolerated at the 4 mg clinical dose. The principal adverse events are mild gastrointestinal complaints (dyspepsia, gastritis), asthenia, and pyrexia, with no clinically significant effects on body weight, hepatic transaminases, renal function, creatine phosphokinase, or cardiac parameters at doses up to 128 mg in single-dose safety studies. The absence of the thiazolidinedione-class adverse events (peripheral edema, weight gain, bone fracture, bladder cancer signal) is attributed to the predominant PPARalpha and moderate PPARgamma pharmacological balance. This monograph reviews the chemistry, synthesis, and stereochemistry of saroglitazar; the dual-receptor pharmacology; the comprehensive human pharmacokinetic record; the clinical evidence base across diabetic dyslipidemia, NAFLD/NASH, PBC, and metabolic liver disease indications; reconstitution, sourcing, and handling considerations for laboratory work; stack-interaction implications; adverse-event and safety signals; and a comparative assessment of five alternative PPAR-targeting compounds against saroglitazar on five competency standards (novelty, effect size, promising potential, side-effect profile, and overall validation).

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  • 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.

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  • 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.

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  • T3D-959

    Dual peroxisome proliferator-activated receptor delta/gamma (PPARd/g) agonist with primary PPARd selectivity and brain-penetrant insulin-sensitizing activity

    A non-thiazolidinedione dual nuclear receptor agonist originally developed for metabolic disease and repositioned as a first-in-class brain insulin-sensitizing therapy for Alzheimer’s disease, distinguished by concurrent PPARd and PPARg activation, high central nervous system penetrance, and Phase 2 evidence of disease-modifying effects on cognition and amyloid biomarkers.

    Abstract

    T3D-959 (DB-959, DB-959Na as the sodium salt) is an orally bioavailable, brain-penetrant, non-thiazolidinedione dual agonist of peroxisome proliferator-activated receptor delta (PPARd; human ED50 19 nM) and peroxisome proliferator-activated receptor gamma (PPARg; human ED50 297 nM), conferring approximately 15-fold selectivity for the delta isoform. The compound was originally synthesized by Bayer and advanced through Phase 1 clinical trials for dyslipidemia and type 2 diabetes by DARA BioSciences before being acquired in 2013 by T3D Therapeutics and repositioned as a disease-modifying candidate for Alzheimer’s disease (AD) on the basis of the “type 3 diabetes” hypothesis, which posits that sporadic AD is driven by progressive brain insulin resistance, deficient insulin and insulin-like growth factor signaling, and consequent neurometabolic dysfunction. T3D-959 is the first PPARd-activating compound to enter clinical development for AD and represents a mechanistically distinct approach from the anti-amyloid antibody and cholinesterase inhibitor classes that dominate the current AD therapeutic landscape. Preclinical characterization in the intracerebral streptozotocin (i.c. STZ) rat model of sporadic AD, conducted principally by the de la Monte laboratory at Brown University, demonstrated that oral T3D-959 at doses of 0.3 to 3.0 mg/kg/day preserved spatial learning and memory in the Morris water maze, prevented brain weight loss, normalized phosphorylated tau and amyloid precursor protein-amyloid beta 42 (AbPP-Ab42) levels, reduced markers of oxidative stress, and partially restored cholinergic enzyme expression and white matter integrity. Therapeutic effects were observed even when treatment was delayed seven days after the STZ insult, suggesting relevance to mild and moderate disease stages. A separate preclinical study demonstrated that T3D-959 at 1.0 mg/kg/day improved motor function and prevented cerebellar white matter atrophy in the same model. An exploratory Phase 2a clinical trial in 36 subjects with mild to moderate AD (Chamberlain et al. 2020) demonstrated safety and tolerability at oral doses of 3, 10, 30, and 90 mg daily for 14 days, with no serious adverse events. Pharmacokinetic analysis confirmed dose-dependent systemic exposure exceeding the PPARd ED50 at all doses tested. Plasma metabolomics showed dose-dependent reductions in branched-chain amino acids and ceramides and increases in acylcarnitines, consistent with improved insulin sensitivity and enhanced fatty acid beta-oxidation. FDG-PET neuroimaging demonstrated dose-dependent increases in regional cerebral glucose metabolism, with the strongest effects in the putamen, anterior cingulate, insula, and orbital frontal cortex. Cognitive assessments showed improvements on the ADAS-Cog11 at 30 mg and on the Digit Symbol Substitution Test at all doses, with a delayed improvement pattern consistent with a transcriptional regulatory mechanism of action and an apparent ApoE4 genotype interaction. The Phase 2 PIONEER trial, a 24-week multicenter randomized double-blind placebo-controlled study in 250 patients with mild to moderate AD, reported positive top-line results in November 2023 at the 16th Clinical Trials on Alzheimer’s Disease (CTAD) conference. In the modified intent-to-treat population (n=141), the 30 mg group showed improvement on ADAS-Cog11 (0.73 versus 2.70 on placebo; p=0.073), and the 15 mg group showed improvement on ADCS-CGIC (0.39 versus 0.86 on placebo; p=0.060). Plasma amyloid beta 42/40 ratio improved significantly in the 30 mg (p=0.011) and 45 mg (p=0.033) groups, and the neurodegeneration marker neurogranin improved significantly in the 30 mg group (p=0.035). The compound was well tolerated, with adverse event rates similar between active and placebo arms (37.3% versus 43.1%) and no treatment-related serious adverse events. A Phase 2b/3 trial (NCT06964230) at 30 mg daily for 78 weeks in approximately 376 patients with biomarker-validated mild to moderate AD is planned to initiate in 2026. T3D-959 is not approved for any indication in any jurisdiction. This monograph reviews the chemistry, dual-receptor pharmacology, preclinical evidence base, clinical development program, pharmacokinetics, sourcing, reconstitution, stack interactions, adverse-event signal, and a comparative assessment of five alternative PPAR-targeting and insulin-sensitizing candidates against T3D-959 on five competency standards.

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