Donafenib (CM-4307) is a derivative of sorafenib, where [1H] hydrogens on the terminal methyl group are substituted by deuterium. The drug was developed by the Chinese company Suzhou Zelgen Biopharmaceuticals. Upon oral administration, donafenib binds to and blocks the activity of Raf kinase, and inhibits Raf-mediated signal transduction pathways. This inhibits cell proliferation in Raf-expressing tumor cells. In addition, donafenib may inhibit unidentified RTKs, and thus may further block tumor cell proliferation in susceptible tumor cells. Donafenib is being investigated in phase 3 clinical trials for the treatment of 131I-refractory differentiated thyroid cancer, advanced hepatocellular carcinoma, and metastatic colorectal cancer.