The success of poly(ADP-ribose) polymerase–1 (PARP-1) inhibitors (PARPi) to treat cancer relates to their ability to trap PARP-1 at the site of a DNA break. Although different forms of PARPi all target the catalytic center of the enzyme, they have variable abilities to trap PARP-1. We found that several structurally distinct PARPi drive PARP-1 allostery to promote release from a DNA break. Other inhibitors drive allostery to retain PARP-1 on a DNA break. Further, we generated a new PARPi compound, converting an allosteric pro-release compound to a pro-retention compound and increasing its ability to kill cancer cells. These developments are pertinent to clinical applications where PARP-1 trapping is either desirable or undesirable.

A novel set of 64 analogues based on our lead compound 1 was designed and synthesized with an initial objective of understanding the structural requirements of ligands binding to a highly perplexing substrate-binding site of P-glycoprotein (P-gp) and their effect on modulating the ATPase function of the efflux pump. Compound 1, a stimulator of P-gp ATPase activity, was transformed to ATPase inhibitory compounds 39, 53, and 109. The ATPase inhibition by these compounds was predominantly contributed by the presence of a cyclohexyl group in lieu of the 2-aminobenzophenone moiety of 1. The 4,4-difluorocyclohexyl analogues, 53 and 109, inhibited the photolabeling by [I]-IAAP, with IC values of 0.1 and 0.76 μM, respectively. Selected compounds were shown to reverse paclitaxel resistance in HEK293 cells overexpressing P-gp and were selective toward P-gp over CYP3A4. Induced-fit docking highlighted a plausible binding pattern of inhibitory compounds in the putative-binding pocket of P-gp. The current study underscores the stringent requirement by P-gp to bind to chemically similar molecules.

Clostridium difficile infection (CDI) is the leading cause of healthcare-associated infection in the United States. Therefore, development of novel treatments for CDI is a high priority. Toward this goal, we began in vitro screening of a structurally diverse in-house library of 67 compounds against two pathogenic C. difficile strains (ATCC BAA 1870 and ATCC 43255), which yielded a hit compound, 2-methyl-8-nitroquinazolin-4­(3H)-one (2) with moderate potency (MIC = 312/156 μM). Optimization of 2 gave lead compound 6a (2-methyl-7-nitrothieno­[3,2-d]­pyrimidin-4­(3H)-one) with improved potency (MIC = 19/38 μM), selectivity over normal gut microflora, CC50s > 606 μM against mammalian cell lines, and acceptable stability in simulated gastric and intestinal fluid. Further optimization of 6a at C2-, N3-, C4-, and C7-positions resulted in a library of >50 compounds with MICs ranging from 3 to 800 μM against clinical isolates of C. difficile. Compound 8f (MIC = 3/6 μM) was identified as a promising lead for further optimization.

To evaluate interrater agreement in categorizing treatment outcomes and drug responsiveness status according to the International League Against Epilepsy (ILAE) definition of drug-resistant epilepsy. Methods: A total of 1053 adults with focal epilepsy considered by the investigators to meet ILAE criteria for drug resistance were enrolled consecutively at 43 centers and followed up prospectively for 18-34 months. Treatment outcomes for all antiepileptic drugs (AEDs) used up to enrollment (retrospective assessment), and on an AED newly introduced at enrollment, were categorized by individual investigators and by 2 rotating members of a 16-member expert panel (EP) that reviewed the patient records independently. Interrater agreement was tested by Cohen's kappa (k) statistics and rated according to Landis and Koch's criteria. Results: Agreement between EP members in categorizing outcomes on the newly introduced AED was almost perfect (90.1%, k = 0.84, 95% confidence interval [CI] 0.80-0.87), whereas agreement between the EP and individual investigators was moderate (70.4%, k = 0.57, 95% CI 0.53-0.61). Similarly, categorization of outcomes on previously used AEDs was almost perfect between EP members (91.7%, k = 0.83, 95% CI 0.81-0.84) and moderate between the EP and investigators (68.2%, k = 0.50, 95% CI 0.48-0.52). Disagreement was related predominantly to outcomes considered to be treatment failures by the investigators but categorized as undetermined by the EP. Overall, 19% of patients classified as having drug-resistant epilepsy by the investigators were considered by the EP to have "undefined responsiveness."Significance: Interrater agreement in categorizing treatment outcomes according to ILAE criteria ranges from moderate to almost perfect. Nearly 1 in 5 patients considered by enrolling neurologists to be "drug-resistant" were classified by the EP as having "undefined responsiveness."

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