uprifosbuvir uprifosbuvir uprifosbuvir (mk-3682) is an antiviral drug developed for the treatment of hepatitis c. it is a nucleotide analogue which acts as an ns5b rna polymerase inhibitor. as of 2019 it was in phase iii human clinical trials. uprifosbuvirclinical datatrade namesuprifosbuvirlegal statuslegal status us: investigational new drug identifiers iupac name propan-2-yl (2r)-2-methoxy-phenoxyphosphoryl]amino]propanoate cas number1496551-77-9pubchem cid90055716drugbankdb15206chemspider57427403uniijw31kps26skeggd10996chemblchembl3833371chemical and physical dataformulac22h29cln3o9pmolar mass545.9 g·mol−13d model (jsmol)interactive image smiles c(c(=o)oc(c)c)n(=o)(oc1(((o1)n2c=cc(=o)nc2=o)(c)cl)o)oc3=cc=cc=c3 inchi inchi=1s/c22h29cln3o9p/c1-13(2)33-19(29)14(3)25-36(31,35-15-8-6-5-7-9-15)32-12-16-18(28)22(4,23)20(34-16)26-11-10-17(27)24-21(26)30/h5-11,13-14,16,18,20,28h,12h2,1-4h3,(h,25,31)(h,24,27,30)/t14-,16-,18-,20-,22-,36-/m1/s1key:sfpfzqkypowcsi-khfyhrbssa-n in 2017 owner merck wrote down the value of uprifosbuvir to us$240 million, for a write-down of $2.9 billion, reducing its earnings per share from 42¢ to a loss of 22¢ for the fourth quarter of 2016. this was attributed to the hepatitis c drug market rather than uprifosbuvir itself; the population of treatable patients diminished rapidly after the introduction in 2014 of sofosbuvir and the combination ledipasvir/sofosbuvir, drugs that cured hepatitis c, and whose market was also diminishing following their success in curing patients. clinical testing of uprifosbuvir continued.