Development of a Novel IGF2BP1 Inhibitor as Metastasis-Specific Therapeutic Agent

IGF2BP1 is a multifunctional RNA-binding protein that regulates the stability, localization and translation of its mRNA targets. High levels of IGF2BP1 expression have been shown to be associated with poor prognosis in patients with variety of cancer types. Given the correlation between elevated IGF2BP1 expression and poor clinical outcomes, the specific activation of IGF2BP paralogs in a wide variety of cancers, and the effectiveness of preventing metastasis in animal models by reducing IGF2BP1 activity, therapies directed at inhibiting IGF2BP1 function constitute a potentially powerful approach for fighting cancer. In addition, IGF2BP1’s pleiotropic effect on multiple pro-tumorigenic and pro-metastatic pathways make it a promising target, as this may avoid the development of resistance, associated with targeted agents in general. Furthermore, specific inhibitors of IGF2BP1 are expected to have minimal side effects since: i) IGF2BP1 is expressed at very low levels in normal adult tissues, and ii) adult mice with an inducible whole-mouse knockout of IGF2BP1 are healthy. To identify an efficient IGF2BP1 inhibitor, a fluorescent polarization (FP)-based high throughput screen of over 27,000 small molecules was performed, and the most promising candidates were further validated in an array of in vitro and cell-based assays leading to the identification a lead compound, “7773,” that selectively inhibited IGF2BP1 RNA binding and a variety of its cellular functions. To further optimize ‘7773’ and create more selective, effective and safe small-molecule inhibitors of IGF2BP1 that could be developed clinically as cancer therapeutics, we conducted an SAR study based on the lead ‘7773’ structure. Novel 27 compounds were designed and synthesized and evaluated for IGF2BP1 inhibition using our novel cell-based split-luciferase assay, which led to the identification of 6 compounds that performed similar or better than ‘7773’. Cell-based wound healing assay revealed that one of these selected compounds, AVJ16, was especially (>14 times than “7773”) effective in inhibiting cell migration in H1299 cell line that express high levels of endogenous IGF2BP1, but not in LKR-M cells that express very low levels of IGF2BP1. The specificity of AVJ16 was further confirmed in LKR-M cells that ectopically express IGF2BP1 – these cells become sensitive to AVJ16 upon overexpression of IGF2BP1 (but not GFP). Together our data provide strong evidence for AVJ16 to be effective and selective in inhibiting IGF2BP1 function by interfering with its ability to bind target RNAs. No conflict of interest.