ABSTRACT
Herein we describe the design of a novel series of ATP competitive B-Raf inhibitors via structure-based methods. These 3-N-methylquinazoline-4(3H)-one based inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 16, a potent, selective and orally available agent with excellent pharmacokinetic properties and robust tumor growth inhibition in xenograft studies. Our work also demonstrates that by replacing an aryl amide with an aryl sulfonamide, a multikinase inhibitor such as AZ-628, can be converted to a selective B-Raf inhibitor, a finding that should have broad application in kinase drug discovery.
Subject(s)
Drug Design , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Quinazolines/chemical synthesis , Quinazolines/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Crystallography, X-Ray , Enzyme Activation/drug effects , Humans , Inhibitory Concentration 50 , Molecular Structure , Protein Kinase Inhibitors/chemistry , Quinazolines/chemistry , Tumor Burden/drug effects , Xenograft Model Antitumor AssaysABSTRACT
Herein we describe the discovery of a novel series of ATP competitive B-Raf inhibitors via structure based drug design (SBDD). These pyridopyrimidin-7-one based inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 17, a potent, selective and orally available agent with excellent pharmacokinetic properties and robust tumor growth inhibition in xenograft studies.
Subject(s)
Drug Discovery , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Pyrimidinones/pharmacology , Administration, Oral , Biological Availability , Crystallography, X-Ray , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacokinetics , Pyrimidinones/chemistry , Pyrimidinones/pharmacokineticsABSTRACT
Recent clinical data provided proof-of-concept for selective B-Raf inhibitors in treatment of B-Raf(V600E) mutant melanoma. Pyrazolopyridine-type B-Raf inhibitors previously described by the authors are potent and selective but exhibit low solubility requiring the use of amorphous dispersion-based formulation for achieving efficacious drug exposures. Through structure-based design, we discovered a new class of highly potent aminopyrimidine-based B-Raf inhibitors with improved solubility and pharmacokinetic profiles. The hinge binding moiety possesses a basic center imparting high solubility at gastric pH, addressing the dissolution limitation observed with our previous series. In our search for an optimal linker-hinge binding moiety system, amide-linked thieno[3,2-d]pyrimidine analogues 32 and 35 (G945), molecules with desirable physicochemical properties, emerged as lead compounds with strong efficacy in a B-Raf(V600E) mutant mouse xenograft model. Synthesis, SAR, lead selection, and evaluation of key compounds in animal studies will be described.
Subject(s)
Aminopyridines/chemical synthesis , Antineoplastic Agents/chemical synthesis , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Aminopyridines/pharmacokinetics , Aminopyridines/pharmacology , Animals , Antineoplastic Agents/pharmacokinetics , Antineoplastic Agents/pharmacology , Cell Line, Tumor , Crystallography, X-Ray , Drug Screening Assays, Antitumor , Mice , Models, Molecular , Molecular Structure , Neoplasm Transplantation , Quinazolines/chemical synthesis , Quinazolines/pharmacokinetics , Quinazolines/pharmacology , Rats , Solubility , Structure-Activity Relationship , Thiophenes/chemical synthesis , Thiophenes/pharmacokinetics , Thiophenes/pharmacology , Transplantation, HeterologousABSTRACT
A single crystal was obtained of a lead B-Raf(V600E) inhibitor with low aqueous solubility. The X-ray crystal structure revealed hydrogen-bonded head-to-tail dimers formed by the pyrazolopyridine and sulfonamide groups of a pair of molecules. This observation suggested a medicinal chemistry strategy to disrupt crystal packing and reduce the high crystal lattice energy of alternative inhibitors. Both a bulkier group at the interface of the dimer and an out-of-plane substituent were required to decrease the compound's melting point and increase aqueous solubility. These substituents were selected based on previously developed structure-activity relationships so as to concurrently maintain good enzymatic and cellular activity against B-Raf(V600E).
Subject(s)
Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Pyrazoles/pharmacology , Pyridines/pharmacology , Crystallography, X-Ray , Models, Molecular , Molecular Structure , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Proto-Oncogene Proteins B-raf/metabolism , Pyrazoles/chemical synthesis , Pyrazoles/chemistry , Pyridines/chemical synthesis , Pyridines/chemistry , Solubility , Structure-Activity Relationship , Water/chemistryABSTRACT
Herein we describe a novel series of ATP competitive B-Raf inhibitors based on the pyrazolo[1,5-a]pyrimidine scaffold. These inhibitors exhibit both excellent cellular potency and striking B-Raf selectivity. Optimization led to the identification of compound 17, a potent, selective and orally available agent with improved physicochemical and pharmacokinetic properties.
