LY2109761 is a small-molecule inhibitor selectively targeting both TGF-β receptor type I and II ((TβRI/II)) with Ki of 38 nM and 300 nM, respectively [1]. It gave IC50 value of 69 nM in TβRI enzymatic assay [2]. Crystal structure showed the binding of LY2109761 to the ATP binding site of the TGF-β R1 kinase domain [2]. Weak inhibitory activities were reported for other kinases, including Lck, Sapk2α, MKK6, Fyn, and JNK3 (18–89% inhibition at 20 μM) [2].

LY2109761 has shown potential anti-tumor activity in preclinical studies. Deregulation of TGF-β signaling pathway is correlated with various malignant. LY2109761 suppressed proliferation, migration and invasion, and induced apoptosis of pancreatic cancer cells [1]. When combined with gemcitabine, it inhibited tumor growth and metastasis in a mouse model of metastatic pancreatic cancer [1]. It also inhibited the anti-apoptotic effects of TGF-beta1 in myelo-monocytic leukaemic cells [3]. Results in GBM cell lines and an orthotopic intracranial model indicated that LY2109761 increased radiosensitivity and resulted in prolonged survival in glioblastoma [4]. In addition, LY2109761 reduced radiation-induced pneumonitis and pulmonary fibrosis in a murine model [5].

References:
[1]Melisi D, Ishiyama S, Sclabas GM et al. LY2109761, a novel transforming growth factor beta receptor type I and type II dual inhibitor, as a therapeutic approach to suppressing pancreatic cancer metastasis. Mol Cancer Ther 2008; 7: 829-840.[2]Li HY, McMillen WT, Heap CR et al. Optimization of a dihydropyrrolopyrazole series of transforming growth factor-beta type I receptor kinase domain inhibitors: discovery of an orally bioavailable transforming growth factor-beta receptor type I inhibitor as antitumor agent. J Med Chem 2008; 51: 2302-2306.[3]Xu Y, Tabe Y, Jin L et al. TGF-beta receptor kinase inhibitor LY2109761 reverses the anti-apoptotic effects of TGF-beta1 in myelo-monocytic leukaemic cells co-cultured with stromal cells. Br J Haematol 2008; 142: 192-201.[4]Zhang M, Kleber S, Rohrich M et al. Blockade of TGF-beta signaling by the TGFbetaR-I kinase inhibitor LY2109761 enhances radiation response and prolongs survival in glioblastoma. Cancer Res 2011; 71: 7155-7167.[5]Flechsig P, Dadrich M, Bickelhaupt S et al. LY2109761 attenuates radiation-induced pulmonary murine fibrosis via reversal of TGF-beta and BMP-associated proinflammatory and proangiogenic signals. Clin Cancer Res 2012; 18: 3616-3627.