Coadministration has not been studied and is not recommended. Nilotinib is metabolised by CYP3A4 and concentrations are expected to increase due to strong inhibition of CYP3A4 by nirmatrelvir/ritonavir. Ketoconazole (a strong CYP3A4 inhibitor) increased nilotinib AUC by 3-fold. A similar effect is expected with nirmatrelvir/ritonavir and coadministration is not recommended. Nirmatrelvir/ritonavir and nilotinib should not be coadministered to patients with accelerated or blast phase chronic myelogenous leukaemia (CML). For this particular indication, maintain nilotinib treatment and consider an alternative COVID-19 therapy. In chronic phase CML, the decision to pause or dose adjust nilotinib should be made in conjunction with the patient’s oncologist. Restart nilotinib 3 days after completing nirmatrelvir/ritonavir treatment given that CYP3A4 inhibition takes several days to resolve. Alternatively, if coadministration is necessary, consider reducing nilotinib dose to 400 mg daily with close monitoring for toxicity.