LDN-193189

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.