An orally available inhibitor of monocarboxylate transporter 1 (MCT1), with potential antineoplastic activity. Upon oral administration, MCT1 inhibitor AZD3965 binds to MCT1 and prevents the transport of lactate into and out of the cell. This leads to an accumulation of lactate, intracellular acidification, and eventually cancer cell death. MCT1, a protein overexpressed on tumor cells, is responsible for the transport of monocarboxylates across the cell membrane and plays a key role in cell metabolism.