6 research outputs found

    Highly Potent Clickable Probe for Cellular Imaging of MDM2 and Assessing Dynamic Responses to MDM2-p53 Inhibition

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    MDM2 is a key negative regulator of the p53 tumor suppressor. Direct binding of MDM2 to p53 represses the protein’s transcriptional activity and induces its polyubiquitination, targeting it for degradation by the proteasome. Consequently, small molecule inhibitors that antagonize MDM2-p53 binding, such as RG7388, have progressed into clinical development aiming to reactivate p53 function in <i>TP53</i> wild-type tumors. Here, we describe the design, synthesis, and biological evaluation of a trans-cyclooctene tagged derivative of RG7388, RG7388-TCO, which showed high cellular potency and specificity for MDM2. The in-cell reaction of RG7388-TCO with a tetrazine-tagged BODIPY dye enabled fluorescence imaging of endogenous MDM2 in SJSA-1 and T778 tumor cells. RG7388-TCO was also used to pull down MDM2 by reaction with tetrazine-tagged agarose beads in SJSA-1 lysates. The data presented show that RG733-TCO enables precise imaging of MDM2 in cells and can permit a relative assessment of target engagement and MDM2-p53 antagonism in vitro

    Fragment-Based Discovery of a Potent, Orally Bioavailable Inhibitor That Modulates the Phosphorylation and Catalytic Activity of ERK1/2

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    Aberrant activation of the MAPK pathway drives cell proliferation in multiple cancers. Inhibitors of BRAF and MEK kinases are approved for the treatment of BRAF mutant melanoma, but resistance frequently emerges, often mediated by increased signaling through ERK1/2. Here, we describe the fragment-based generation of ERK1/2 inhibitors that block catalytic phosphorylation of downstream substrates such as RSK but also modulate phosphorylation of ERK1/2 by MEK without directly inhibiting MEK. X-ray crystallographic and biophysical fragment screening followed by structure-guided optimization and growth from the hinge into a pocket proximal to the C-Îą helix afforded highly potent ERK1/2 inhibitors with excellent kinome selectivity. In BRAF mutant cells, the lead compound suppresses pRSK and pERK levels and inhibits proliferation at low nanomolar concentrations. The lead exhibits tumor regression upon oral dosing in BRAF mutant xenograft models, providing a promising basis for further optimization toward clinical pERK1/2 modulating ERK1/2 inhibitors

    Fragment-Based Discovery of a Potent, Orally Bioavailable Inhibitor That Modulates the Phosphorylation and Catalytic Activity of ERK1/2

    No full text
    Aberrant activation of the MAPK pathway drives cell proliferation in multiple cancers. Inhibitors of BRAF and MEK kinases are approved for the treatment of BRAF mutant melanoma, but resistance frequently emerges, often mediated by increased signaling through ERK1/2. Here, we describe the fragment-based generation of ERK1/2 inhibitors that block catalytic phosphorylation of downstream substrates such as RSK but also modulate phosphorylation of ERK1/2 by MEK without directly inhibiting MEK. X-ray crystallographic and biophysical fragment screening followed by structure-guided optimization and growth from the hinge into a pocket proximal to the C-Îą helix afforded highly potent ERK1/2 inhibitors with excellent kinome selectivity. In BRAF mutant cells, the lead compound suppresses pRSK and pERK levels and inhibits proliferation at low nanomolar concentrations. The lead exhibits tumor regression upon oral dosing in BRAF mutant xenograft models, providing a promising basis for further optimization toward clinical pERK1/2 modulating ERK1/2 inhibitors
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