Fig. 26.22 A new allosteric binding site was discovered at Sunesis that is approximately 20 Å away from the catalytic site of the phosphatase. Compound 26.54 inhibits PTP-1B 16-fold more strongly than TCPTP. The crystal structure with PTP-1B shows that the inhibitor basically wraps itself around the exposed Phe280. In TCPTP a cysteine residue is found in the same position.