TDG-IN-1

TDG-IN-1 is an orally active, selective small molecule inhibitor of thymine DNA glycosylase (TDG) with a Ka of 1.46 nM. It disrupts TDG's DNA binding ability, induces downregulation of DHX9 expression, leads to double-stranded RNA accumulation, and activates the RIG-I/MDA5-MAVS pathway. Additionally, it acts as a tumor suppressor, innate immune activator, and immune stimulator. TDG-IN-1 inhibits the growth of p53-deficient tumor cells and xenografts, exhibiting a synthetic lethal effect with p53. This compound is useful for research in p53-deficient cancers.

TDG-IN-1 (Compound C-271) exhibits potent inhibition of the glycosylase activity of purified human TDG on various double-stranded DNA (dsDNA) substrates, with an IC50 range of 0.16 to 0.25 μM when applied for 1 hour. Additionally, TDG-IN-1 obstructs TDG's ability to bind to multiple dsDNA substrate types, with an IC50 range of 0.11 to 0.19 μM after overnight incubation. When used at 1.25 μM for 4 days, TDG-IN-1 inhibits the viability of p53-deficient KP lung adenocarcinoma cells in a TDG-dependent manner. It selectively suppresses the viability of p53-deficient human solid tumor cell lines, achieving IC50 values below 5 μM in all 16 tested p53-deficient cell lines. Moreover, treatment of p53-deficient KP lung adenocarcinoma cells with 1.25 μM of TDG-IN-1 for 4 days results in the accumulation of cytoplasmic dsRNA. Furthermore, TDG-IN-1 decreases the expression of DHX9 protein in a dose-dependent manner in p53-deficient KP lung adenocarcinoma cells in vitro, when used at concentrations ranging from 0.625 to 2.5 μM over 4 days.

Administered at 50 mg/kg intragastrically once daily for 14 to 25 days, TDG-IN-1 (Compound C-271) effectively inhibits tumor growth in p53-null NCI-H1299 and p53-mutated NCI-H446 xenograft models, while also prolonging mouse survival without significant toxicity. At a dose of 5 mg/kg given intragastrically once per day for 30 to 50 days, TDG-IN-1 works synergistically with anti-CTLA4 antibody, enhancing suppression of tumor growth and extending survival in p53-deficient KP allograft tumor model mice. Additionally, at 5 mg/kg, administered intragastrically daily for 25 to 50 days, the compound in combination with anti-CTLA4 antibody also enhances tumor growth inhibition and prolongs survival in p53-deleted 4T1 breast cancer xenograft models.