pyrimidinones and veliparib

Synthetic lethality refers to a lethal phenotype that results from the simultaneous disruptions of two genes, while the disruption of either gene alone is viable. Many DNA double strand break repair (DSBR) genes have synthetic lethal relationships with oncogenes and tumor suppressor genes, which can be exploited for targeted cancer therapy, an approach referred to as combination therapy. DNA double-strand breaks (DSBs) are one of the most toxic lesions to a cell and can be repaired by non-homologous end joining (NHEJ) or homologous recombination (HR). HR and NHEJ genes are particularly attractive targets for cancer therapy because these genes have altered expression patterns in cancer cells when compared with normal cells and these genetic abnormalities can be targeted for selectively killing cancer cells. Here, we review recent advances in the development of small molecule inhibitors against HR and NHEJ genes to induce synthetic lethality and address the future directions and clinical relevance of this approach. © 2017 IUBMB Life, 69(12):929-937, 2017.

Topics: Benzimidazoles; Cell Cycle; Chromones; Clinical Trials as Topic; DNA Breaks, Double-Stranded; DNA End-Joining Repair; DNA, Neoplasm; Humans; Indoles; Molecular Targeted Therapy; Morpholines; MRE11 Homologue Protein; Neoplasms; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Pyrimidinones; Recombinational DNA Repair; Synthetic Lethal Mutations; Thiones

This trial assessed the utility of applying tumor DNA sequencing to treatment selection for patients with advanced, refractory cancer and somatic mutations in one of four signaling pathways by comparing the efficacy of four study regimens that were either matched to the patient's aberrant pathway (experimental arm) or not matched to that pathway (control arm).. Adult patients with an actionable mutation of interest were randomly assigned 2:1 to receive either (1) a study regimen identified to target the aberrant pathway found in their tumor (veliparib with temozolomide or adavosertib with carboplatin [DNA repair pathway], everolimus [PI3K pathway], or trametinib [RAS/RAF/MEK pathway]), or (2) one of the same four regimens, but chosen from among those not targeting that pathway.. Among 49 patients treated in the experimental arm, the objective response rate was 2% (95% CI, 0% to 10.9%). One of 20 patients (5%) in the experimental trametinib cohort had a partial response. There were no responses in the other cohorts. Although patients and physicians were blinded to the sequencing and random assignment results, a higher pretreatment dropout rate was observed in the control arm (22%) compared with the experimental arm (6%;. Further investigation, better annotation of predictive biomarkers, and the development of more effective agents are necessary to inform treatment decisions in an era of precision cancer medicine. Increasing prevalence of tumor mutation profiling and preference for targeted therapy make it difficult to use a randomized phase II design to evaluate targeted therapy efficacy in an advanced disease setting.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Benzimidazoles; Carboplatin; DNA, Neoplasm; Double-Blind Method; Everolimus; Female; Gene Expression Profiling; Humans; Male; Middle Aged; Molecular Diagnostic Techniques; Neoplasms; Pyrazoles; Pyridones; Pyrimidinones; Temozolomide; Young Adult

The poly(ADP-ribose) polymerase (PARP) family represents a new class of therapeutic targets with diverse potential disease indications. PARP1 and PARP2 inhibitors have been developed for breast and ovarian tumors manifesting double-stranded DNA-repair defects, whereas tankyrase 1 and 2 (TNKS1 and TNKS2, also known as PARP5a and PARP5b, respectively) inhibitors have been developed for tumors with elevated β-catenin activity. As the clinical relevance of PARP inhibitors continues to be actively explored, there is heightened interest in the design of selective inhibitors based on the detailed structural features of how small-molecule inhibitors bind to each of the PARP family members. Here, the high-resolution crystal structures of the human TNKS2 PARP domain in complex with 16 various PARP inhibitors are reported, including the compounds BSI-201, AZD-2281 and ABT-888, which are currently in Phase 2 or 3 clinical trials. These structures provide insight into the inhibitor-binding modes for the tankyrase PARP domain and valuable information to guide the rational design of future tankyrase-specific inhibitors.

Topics: Benzamides; Benzimidazoles; Bridged Bicyclo Compounds, Heterocyclic; Catalytic Domain; Crystallography, X-Ray; Enzyme Inhibitors; Humans; Models, Molecular; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Protein Conformation; Pyrimidinones; Quinazolines; Tankyrases