Encoding the genetic instructions essential to both our development and function as living organisms, our DNA must be maintained with exquisite precision and integrity, especially throughout replication [1, 2]. DNA can undergo damage in many different ways by both endogenous and exogenous agents. Thus, the numerous mechanisms by which DNA damage is both recognized and repaired are essential to cell survival. ATAD5 is involved in the DNA damage response, and its protein level increases in response to DNA damage without an increase in mRNA transcription [3, 4]. Identification of pathway(s) that stabilize ATAD5 protein levels in response to DNA damage and inhibitors of these pathway(s) would be beneficial to understanding a novel mechanism involved in the DNA damage response and introduce a new therapeutic approach for sensitizing cancer cells, respectively [5, 6]. However, no chemical matter is currently known that perturbs ATAD5 function. To understand the biology of ATAD5 and to evaluate its therapeutic potential, we conducted a quantitative high throughput screening campaign and subsequent medicinal chemistry optimization in pursuit of small molecules that destabilize ATAD5. Herein, we detail the discovery of ML367, a probe molecule that has low micromolar inhibitory activity in the ATAD5 destabilizer screen run with 10 μM 5-fluorouridine (5-FUrd) as the DNA damaging agent. Interestingly, ML367 was found to block general DNA damage responses including RPA32-phosphorylation and CHK1-phosphorylation in response to UV irradiation. In this regard, the probe molecule could block DNA repair pathways that function upstream of ATAD5. Additionally, the compound sensitized cells possessing a knock-out mutation of the PARP1 gene and as a result may serve as a sensitizer to kill cancer cells defective in the poly (ADP-ribose) polymerase 1 (PARP1)-dependent DNA repair pathway.