Fig 6. CCX559 accumulated in MC38-hPD-L1 tumors in vivo and induced PD-L1 internalization.

(A) CCX559 or vehicle was dosed orally once daily for seven days in human PD-L1 KI mice (n = 5 per group) with ≥100 mm³ MC38-hPD-L1 tumors. CCX559 levels were measured one day after the final dose and normalized per gram of tissue, or per ml of plasma. (B) In a CCX559 dosing study similar to A, tumor, plasma, and tissue drug levels were measured on days 1, 5 and 12 post dosing. CCX559 levels decreased from day 1 to day 5 and were not detected on day 12. (C-E) For the dosing study in B, only intracellular PD-L1 was observed by IHC with anti-PD-L1 monoclonal antibody 28–8, when CCX559 was still present in tumors on day 1 (C) and day 5 post dose (D), but after drug clearance on day 12 post dose plasma membrane PD-L1 was observed in tumors (E). (F-H) Cell surface PD-L1 was detected in the vehicle control tumors at all timepoints.