Monocarboxylate transporter (MCT1) inhibitor (pKi = 7.6. Exhibits approximately 10-fold selectivity for MCT1 over MCT2 and no significant activity against MCT3 or 4. Inhibits graft versus host response and prolongs cardiac graft survival in a rat model. Immunosuppressant. Also inhibits brain penetration of GHB analog HOCPCA.