Mantle cell lymphoma (MCL) is a rare and aggressive form of B-cell non-Hodgkin lymphoma (NHL). Approximately 40%-50% of MCL patients carry inactivating mutations in the gene ataxia telangiectasia mutated (ATM), a core component of the cell's DNA damage response system. MCL cells with mutations in ATM are known to have increased chromosomal imbalance, copy number loss, and hypersensitivity to DNA-damaging agents. LP-184, a small-molecule DNA-damaging agent, is known to be synthetically lethal in tumors with DNA-repair deficiencies, including tumors with ATM mutations. However, DNA damage by LP-184 is dependent on activation by the oxidoreductase prostaglandin reductase 1 (PTGR1), which is expressed at low levels in many hematological cancers. We synthesized LP-284, an enantiomer of LP-184, which retains synthetic lethality in cancers with impaired DNA damage repair pathway genes (e.g., ERCC1, ERCC2, ERCC3, ERCC6), but LP-284's activity is independent of PTGR1 expression. We demonstrated that LP-284 has enhanced tumoricidal activity in multiple hematological cancer cell lines using a B-cell NHL panel. The IC50 values for all 6 MCL cell lines treated with LP-284 were among the lowest for all hematological cell lines tested with LP-284. These MCL cell lines included cell lines resistant to ibrutinib, zanubrutinib, venetoclax, and bortezomib. Additionally, among the 6 MCL cell lines tested, the 3 cell lines with mutations in the nucleotide excision repair (NER) or homologous recombination (HR) DNA damage repair pathways had lower LP-284 IC50 values than the 3 cell lines without NER or HR mutations. Because ATM orchestrates the activities of the NER and HR pathways, MCL patients with ATM deficiencies are likely to have better responses to LP-284 treatment. Collectively, these data indicate that LP-284 is a promising preclinical DNA-damaging agent that possesses nanomolar-range anti-tumor activities in multiple and diverse MCL cell lines, with the potential to treat MCL patients who are resistant to other therapies.