pyrimidinones and crenolanib

FLT3 mutations are prevalent in AML patients and confer poor prognosis. Crenolanib, a potent type I pan-FLT3 inhibitor, is effective against both internal tandem duplications and resistance-conferring tyrosine kinase domain mutations. While crenolanib monotherapy has demonstrated clinical benefit in heavily pretreated relapsed/refractory AML patients, responses are transient and relapse eventually occurs. Here, to investigate the mechanisms of crenolanib resistance, we perform whole exome sequencing of AML patient samples before and after crenolanib treatment. Unlike other FLT3 inhibitors, crenolanib does not induce FLT3 secondary mutations, and mutations of the FLT3 gatekeeper residue are infrequent. Instead, mutations of NRAS and IDH2 arise, mostly as FLT3-independent subclones, while TET2 and IDH1 predominantly co-occur with FLT3-mutant clones and are enriched in crenolanib poor-responders. The remaining patients exhibit post-crenolanib expansion of mutations associated with epigenetic regulators, transcription factors, and cohesion factors, suggesting diverse genetic/epigenetic mechanisms of crenolanib resistance. Drug combinations in experimental models restore crenolanib sensitivity.

Topics: Adult; Aged; Aged, 80 and over; Animals; Antineoplastic Combined Chemotherapy Protocols; Benzimidazoles; Cell Line, Tumor; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Epigenesis, Genetic; Exome Sequencing; Female; fms-Like Tyrosine Kinase 3; GTP Phosphohydrolases; HEK293 Cells; Humans; Inhibitory Concentration 50; Isocitrate Dehydrogenase; Leukemia, Myeloid, Acute; Male; Membrane Proteins; Mice; Middle Aged; Mutation; Piperidines; Protein Kinase Inhibitors; Pyridones; Pyrimidinones; Tandem Repeat Sequences; Treatment Outcome

Activating mutations in the proto-oncogene KRAS are a hallmark of pancreatic ductal adenocarcinoma (PDAC), an aggressive malignancy with few effective therapeutic options. Despite efforts to develop KRAS-targeted drugs, the absolute dependence of PDAC cells on KRAS remains incompletely understood. Here we model complete KRAS inhibition using CRISPR/Cas-mediated genome editing and demonstrate that KRAS is dispensable in a subset of human and mouse PDAC cells. Remarkably, nearly all KRAS deficient cells exhibit phosphoinositide 3-kinase (PI3K)-dependent mitogen-activated protein kinase (MAPK) signaling and induced sensitivity to PI3K inhibitors. Furthermore, comparison of gene expression profiles of PDAC cells retaining or lacking KRAS reveal a role of KRAS in the suppression of metastasis-related genes. Collectively, these data underscore the potential for PDAC resistance to even the very best KRAS inhibitors and provide insights into mechanisms of response and resistance to KRAS inhibition.

Topics: Animals; Antineoplastic Agents; Benzimidazoles; Carcinoma, Pancreatic Ductal; DNA Copy Number Variations; Humans; Immunoblotting; Indazoles; Mice; Morpholines; Pancreatic Neoplasms; Phenylurea Compounds; Piperidines; Proto-Oncogene Mas; Proto-Oncogene Proteins p21(ras); Purines; Pyrimidines; Pyrimidinones; Quinazolinones; Sulfonamides; Thiazoles