The MCT1 inhibitor AZD3965 is in early phase clinical trials (www.clinicaltrials.gov) with phase I expansion cohort enrichment for Burkitt lymphoma and diffuse large B cell lymphoma cases, given the promising pre-clinical results obtained with the drug in this setting.11–13 Gaining an insight into the consequences of MCT1 inhibition on metabolism and tumour function as a whole is therefore necessary to (a) improve our understanding of the processes relevant to the drug’s mechanism of action and (b) enable the discovery of pharmacodynamic (PD) biomarkers of target modulation. The gene discussed is SLC16A1; the disease is diffuse large B-cell lymphoma.