Monocarboxylate transporter inhibitors
CRUK is testing a MCT1i produced by AstraZeneca (NCT01791595) and some data have been presented in the past . The reason I mention this is because a second (MCT4i) is likely going to be moved forward into the clinic  and this paper tested both with metformin .
A second company is also active in this space. Some data on their lead  and they are working on a second (MTC1i).