ABSTRACT
The BET family of proteins consists of BRD2, BRD3, BRD4, and BRDt. Each protein contains two distinct bromodomains (BD1 and BD2). BET family bromodomain inhibitors under clinical development for oncology bind to each of the eight bromodomains with similar affinities. We hypothesized that it may be possible to achieve an improved therapeutic index by selectively targeting subsets of the BET bromodomains. Both BD1 and BD2 are highly conserved across family members (>70% identity), whereas BD1 and BD2 from the same protein exhibit a larger degree of divergence (â¼40% identity), suggesting selectivity between BD1 and BD2 of all family members would be more straightforward to achieve. Exploiting the Asp144/His437 and Ile146/Val439 sequence differences (BRD4 BD1/BD2 numbering) allowed the identification of compound 27 demonstrating greater than 100-fold selectivity for BRD4 BD2 over BRD4 BD1. Further optimization to improve BD2 selectivity and oral bioavailability resulted in the clinical development compound 46 (ABBV-744).
Subject(s)
Cell Cycle Proteins/antagonists & inhibitors , Cell Cycle Proteins/metabolism , Drug Discovery/methods , Pyridines/chemistry , Pyridines/metabolism , Pyrroles/chemistry , Pyrroles/metabolism , Transcription Factors/antagonists & inhibitors , Transcription Factors/metabolism , Animals , Female , HeLa Cells , Humans , Mice , Mice, SCID , Protein Domains/drug effects , Protein Domains/physiology , Protein Structure, Secondary , Protein Structure, Tertiary , Pyridines/pharmacology , Pyrroles/pharmacology , Xenograft Model Antitumor Assays/methodsABSTRACT
Novel conformationally constrained BET bromodomain inhibitors have been developed. These inhibitors were optimized in two similar, yet distinct chemical series, the 6-methyl-1H-pyrrolo[2,3-c]pyridin-7(6H)-ones (A) and the 1-methyl-1H-pyrrolo[2,3-c]pyridin-7(6H)-ones (B). Each series demonstrated excellent activity in binding and cellular assays, and lead compounds from each series demonstrated significant efficacy in in vivo tumor xenograft models.
Subject(s)
Nuclear Proteins/antagonists & inhibitors , Pyridones/chemistry , Transcription Factors/antagonists & inhibitors , Animals , Binding Sites , Cell Cycle Proteins , Cell Line, Tumor , Cell Proliferation/drug effects , Crystallography, X-Ray , Drug Evaluation, Preclinical , Half-Life , Humans , Mice , Microsomes/metabolism , Molecular Dynamics Simulation , Multiple Myeloma/drug therapy , Nuclear Proteins/metabolism , Protein Structure, Tertiary , Pyridones/pharmacokinetics , Pyridones/pharmacology , Pyridones/therapeutic use , Structure-Activity Relationship , Transcription Factors/metabolism , Transplantation, HeterologousABSTRACT
The development of bromodomain and extraterminal domain (BET) bromodomain inhibitors and their examination in clinical studies, particularly in oncology settings, has garnered substantial recent interest. An effort to generate novel BET bromodomain inhibitors with excellent potency and drug metabolism and pharmacokinetics (DMPK) properties was initiated based upon elaboration of a simple pyridone core. Efforts to develop a bidentate interaction with a critical asparagine residue resulted in the incorporation of a pyrrolopyridone core, which improved potency by 9-19-fold. Additional structure-activity relationship (SAR) efforts aimed both at increasing potency and improving pharmacokinetic properties led to the discovery of the clinical candidate 63 (ABBV-075/mivebresib), which demonstrates excellent potency in biochemical and cellular assays, advantageous exposures and half-life both in animal models and in humans, and in vivo efficacy in mouse models of cancer progression and inflammation.
Subject(s)
Drug Discovery , Proteins/antagonists & inhibitors , Pyridones/pharmacology , Sulfonamides/pharmacology , Animals , Cell Line, Tumor , Chromatography, High Pressure Liquid , Fluorescence Resonance Energy Transfer , Half-Life , Humans , Mass Spectrometry , Mice , Proton Magnetic Resonance Spectroscopy , Pyridones/chemistry , Pyridones/pharmacokinetics , Structure-Activity Relationship , Sulfonamides/chemistry , Sulfonamides/pharmacokineticsABSTRACT
Members of the BET family of bromodomain containing proteins have been identified as potential targets for blocking proliferation in a variety of cancer cell lines. A two-dimensional NMR fragment screen for binders to the bromodomains of BRD4 identified a phenylpyridazinone fragment with a weak binding affinity (1, Ki = 160 µM). SAR investigation of fragment 1, aided by X-ray structure-based design, enabled the synthesis of potent pyridone and macrocyclic pyridone inhibitors exhibiting single digit nanomolar potency in both biochemical and cell based assays. Advanced analogs in these series exhibited high oral exposures in rodent PK studies and demonstrated significant tumor growth inhibition efficacy in mouse flank xenograft models.
Subject(s)
Macrocyclic Compounds/chemistry , Macrocyclic Compounds/pharmacology , Pyridones/chemistry , Pyridones/pharmacology , Animals , Crystallography, X-Ray , Drug Discovery , Macrocyclic Compounds/pharmacokinetics , Molecular Structure , Pyridones/pharmacokinetics , Rats , Structure-Activity RelationshipABSTRACT
An NMR fragment screen for binders to the bromodomains of BRD4 identified 2-methyl-3-ketopyrroles 1 and 2. Elaboration of these fragments guided by structure-based design provided lead molecules with significant activity in a mouse tumor model. Further modifications to the methylpyrrole core provided compounds with improved properties and enhanced activity in a mouse model of multiple myeloma.