Poly-(ADP-ribsoyl) Polymerases (PARPs) are a superfamily of enzymes comprised of 17 known isoforms. PARP inhibitors (PARPi) have shown success in clinical trials for the treatment of homologous recombination-deficient cancers. Though proven effective initially, tumors treated with PARPi eventually develop resistance. Combinatorial therapeutics targeting PARP and other pathways that may re-sensitize tumors to PARP inhibition, including PI3K/AKT/mTor pathway, and cell-cycle checkpoints (such as CDKs, CHK, and Wee) are being tested. In this context, the synthetic lethality of cyclin-dependent kinase 1 (CDK1) and PARP1 is known. Evaluation of PARP1 and CDK1 pharmacophores led to the development of the tetrahydro-arylazepinone (TAAP) scaffold as a potential dual PARP1/CDK1 inhibitor. We screened a handful of TAAP analogs against PARP1 in a cell-free assay that identified the low micromolar PARP1 inhibitor 1,2,3,4-tetrahydro-5H-benzo[e][1,4]-diazepin-5-one (TBAP), which served as the lead compound. The analogous 1,2,3,4-tetrahydro-5H-pyrido[2,3-e][1,4]-diazepin-5-one (TPAP) series showed a similar bioactivity profile. Satisfyingly, the N1-benzyl TPAP analogue showed activity in the low nanomolar range. The TAAP series (i.e., 6/7-membered scaffold) unfortunately lacked CDK1 inhibitory activity. Finally, many PARPi's show poor isoform-selectivity. The development of isoform-selective PARPi can clarify the specific function of each PARP isoform and may reduce the adverse side effects shown by PARPi. A handful of TAAP analogs were screened against 13 PARP isoforms, where some compounds demonstrated exquisite PARP1/2 selectivity. Concurrently, we discovered an inhibitor for PARP11, an isoform that lacks any known synthetic ligand. Future directions are suggested towards fine-tuning the structure-activity relationship of TAAP-isoform selective PARPi as well as developing a dual PARP1/CDK1 inhibitor. / Master of Science / The aim of this work is to explore the therapeutic potential of poly-(ADP-ribosyl) polymerase inhibitors (PARPi) for the treatment of ovarian and breast cancer, specifically triple negative breast cancer. Poly-(ADP-ribsoyl) Polymerases (PARPs) are a superfamily of enzymes comprised of 17 known isoforms. Currently, there are three FDA approved PARPi - olaparib, isoforms. Further, tumors have been shown to develop resistance to PARPi. Herein, we explored the 1,2,3,4-tetrahydro-5H-aryl[1,4]diazepin-5-one scaffold as a potential PARP1/2-selective rucaparib, and niraparib; however, these PARPi demonstrate non-selectivity amongst the PARP inhibitor and its possibility for targeted pharmacology with other kinases.