Multiple clinical trials are actively investigating the role of targeting homologous recombination deficiency (HRD) in ES via CHK1 (ClinicalTrials.gov identifier: NCT05275426) and PARP inhibition (ClinicalTrials.gov identifier: NCT01858168, NCT04901702). This evidence concerns the gene CHEK1 and hypoparathyroidism-retardation-dysmorphism syndrome.