166Ho-Chitosan is a radiopharmaceutical drug available in South Korea as a therapy for hepatocellular carcinoma under the name Milican and launched in August 2001. Chitosan is a biological originating substance (chitin extracted from crab shell) in a gel form at slightly acid pH which becomes a solid (foam) as soon as the pH drops below 7.0. These basic pH conditions are to be found in the vicinity of tumor cells. The combination of Chitosan and 166Ho allows the radionuclide to be physically retained next to the tumor cell. The first marketing authorization was obtained for the use in hepatocarcinoma.

Several other indications have been explored including prostate cancer, rheumatoid arthritis (this indication was discontinued in 2005) or glioblastoma, as well as in form of a patch formulation for skin cancer.