We hypothesise that considering the lack of clinically significant hyperphosphataemia, the relative sparing of FGFR1, and the lack of clear dose-related increase in FGF23, ARQ 087 may be in the unique position of potently inhibiting cancers with FGFR2 dysregulation without causing hyperphosphataemia. Here, FGFR1 is linked to hyperphosphatemia.