Combination formulation of two antiviral compounds

A pharmaceutical composition in the form of a fixed dose combination tablet comprising: a) from 1% to 25% w/w of a solid dispersion comprising Compound I dispersed within a polymeric matrix formed by copovidone, where the ratio in weight of Compound I to copovidone in the solid dispersion is 1:1 and wherein Compound I is substantially amorphous having the formula: **(See formula)** b) 35% to 45% w/w of sofosbuvir characterized by 2θ reflections of XRPD (º ± 0.2θ) at: 6.1 and 12.7 or at: 6.1, 20 .1 and 20.8, where sofosbuvir is substantially crystalline having the formula: **(See formula)** c) from 1% to 40% w/w of microcrystalline cellulose; d) from 1% to 8% w/w croscarmellose sodium; and e) from 0.5% to 2.5% w/w of magnesium stearate; for use in the treatment of hepatitis C.