ABSTRACT
B cell lymphoma 6 (BCL6), a highly regulated transcriptional repressor, is deregulated in several forms of non-Hodgkin lymphoma (NHL), most notably in diffuse large B-cell lymphoma (DLBCL). The activities of BCL6 are dependent on protein-protein interactions with transcriptional co-repressors. To find new therapeutic interventions addressing the needs of patients with DLBCL, we initiated a program to identify BCL6 inhibitors that interfere with co-repressor binding. A virtual screen hit with binding activity in the high micromolar range was optimized by structure-guided methods, resulting in a novel and highly potent inhibitor series. Further optimization resulted in the lead candidate 58 (OICR12694/JNJ-65234637), a BCL6 inhibitor with low nanomolar DLBCL cell growth inhibition and an excellent oral pharmacokinetic profile. Based on its overall favorable preclinical profile, OICR12694 is a highly potent, orally bioavailable candidate for testing BCL6 inhibition in DLBCL and other neoplasms, particularly in combination with other therapies.
ABSTRACT
Both previous and additional genetic knockdown studies reported herein implicate G protein-coupled receptor kinase 6 (GRK6) as a critical kinase required for the survival of multiple myeloma (MM) cells. Therefore, we sought to develop a small molecule GRK6 inhibitor as an MM therapeutic. From a focused library of known kinase inhibitors, we identified two hits with moderate biochemical potencies against GRK6. From these hits, we developed potent (IC50 < 10 nM) analogues with selectivity against off-target kinases. Further optimization led to the discovery of an analogue (18) with an IC50 value of 6 nM against GRK6 and selectivity against a panel of 85 kinases. Compound 18 has potent cellular target engagement and antiproliferative activity against MM cells and is synergistic with bortezomib. In summary, we demonstrate that targeting GRK6 with small molecule inhibitors represents a promising approach for MM and identify 18 as a novel, potent, and selective GRK6 inhibitor.
Subject(s)
Antineoplastic Agents/pharmacology , Drug Design , G-Protein-Coupled Receptor Kinases/antagonists & inhibitors , Multiple Myeloma/drug therapy , Protein Kinase Inhibitors/pharmacology , Quinazolines/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Proliferation/drug effects , Cell Survival/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , G-Protein-Coupled Receptor Kinases/metabolism , Humans , Mice , Models, Molecular , Molecular Structure , Multiple Myeloma/metabolism , Multiple Myeloma/pathology , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Quinazolines/chemical synthesis , Quinazolines/chemistry , Structure-Activity RelationshipABSTRACT
Excessive signaling from the Wnt pathway is associated with numerous human cancers. Using a high throughput screen designed to detect inhibitors of Wnt/ß-catenin signaling, we identified a series of acyl hydrazones that act downstream of the ß-catenin destruction complex to inhibit both Wnt-induced and cancer-associated constitutive Wnt signaling via destabilization of ß-catenin. We found that these acyl hydrazones bind iron in vitro and in intact cells and that chelating activity is required to abrogate Wnt signaling and block the growth of colorectal cancer cell lines with constitutive Wnt signaling. In addition, we found that multiple iron chelators, desferrioxamine, deferasirox, and ciclopirox olamine similarly blocked Wnt signaling and cell growth. Moreover, in patients with AML administered ciclopirox olamine, we observed decreased expression of the Wnt target gene AXIN2 in leukemic cells. The novel class of acyl hydrazones would thus be prime candidates for further development as chemotherapeutic agents. Taken together, our results reveal a critical requirement for iron in Wnt signaling and they show that iron chelation serves as an effective mechanism to inhibit Wnt signaling in humans.
