A member of the class of pyrazoles that is 1<em>H</em>-pyrazole substituted by 6-methylpyridin-2-yl and 1,5-naphthyridin-2-yl groups at positions 3 and 4, respectively. It is a potent and selective inhibitor of TGF-β R1 kinase (IC<small>₅₀</small> = 4 nM) and ALK5 autophosphorylation and binding (IC<small>₅₀</small> = 23 nM). ChEBI: RepSox is a member of the class of pyrazoles that is 1H-pyrazole substituted by 6-methylpyridin-2-yl and 1,5-naphthyridin-2-yl groups at positions 3 and 4, respectively. It is a potent and selective inhibitor of TGF-beta R1 kinase (IC50 = 4 nM) and ALK5 autophosphorylation and binding (IC50 = 23 nM). It has a role as a TGFbeta receptor antagonist, an antineoplastic agent, an EC 2.7.10.1 (receptor protein-tyrosine kinase) inhibitor and a bone density conservation agent. It is a 1,5-naphthyridine derivative, a member of pyrazoles and a member of pyridines.