Cobimetinib- 13 C 6 (GDC-0973- 13 C 6 ; XL518- 13 C 6 ) racemate is the deuterium labeled Cobimetinib (racemate). Cobimetinib racemate (GDC-0973 racemate; XL518 racemate) is the racemate of Cobimetinib. Cobimetinib is a potent and selective MEK inhibitor.