PRO-001 demonstrates in vivo antitumor activity in an FGFR3-driven xenograft tumor model. (A) FDCP-FGFR3^S249C cells were cultured in the presence of increasing amounts of PRO-001 or control antibody (C). Two days later, cell proliferation was determined by XTT analysis. Data are the average of duplicate cultures. (B) Nude mice (3 in each group) were injected subcutaneously at 2 locations, one on each flank (a, right flank; b, left flank), with 2 × 10⁶ FDCP-FGFR3^S249C cells each. A week later, mice were randomized to receive PRO-001 or PBS control by intraperitoneal injection, according to the schedule described in Table 1. Tumor volume was estimated from measurements in 3 dimensions at 22 or 29 days after cell injection.