Recent advances in next generation sequencing (NGS) and molecular subtyping of tumors have opened the door to clinically available targeted therapies. Although the treatment of many solid tumors still rely on a steady regimen of non-targeted chemotherapeutic agents, it is becoming increasingly more apparent that certain tumors with defects in DNA damage repair (DDR) genes may be exquisitely sensitive to DNA damaging agents or therapies targeting key elements of this pathway such PARP1, ATR, or ATM. Still, for tumors with DDR defects the challenges are multi-fold including: (I) identifying these tumors in patients in time for a window of opportunity of treatment; (II) ensuring that these tumors are still reliant or addicted to this pathway; and (III) making sure these tumors are matched with the precise treatment option. Herein, we will discuss the opportunities, challenges, and future of targeting a subset of DDR-defective tumors.