CDA deficiency is not associated with higher sensitivity to immune checkpoint inhibitors in melanoma patients

Cytidine deaminase (CDA) is an enzyme of the pyrimidine salvage pathway that metabolizes cytidine. CDA plays an important role in the sensitivity/resistance of cancer cells to treatment with cytidine analogues, and early severe toxicity has been reported in cancer patients with low levels of CDA activity treated with gemcitabine, azacytidine or cytarabine [1]. The impact of CDA on the clinical outcome of gemcitabine has been particularly studied over the last decade [2]. Therefore, CDA testing is routinely performed at our institution as part of routine screening of cancer patients to predict potential treatment-related toxicities.