The present invention relates to a pharmaceutical composition comprising a solid suspension prepared by hot melt extrusion of isobutyric acid (2R,3S,4R,5R)-5-(4-amino-2-oxo-2H-pyrimidin-1-yl)-2-azido-3,4-bis-iso-butyryloxy-tetrahydro-furan-2-ylmethyl ester; hydrochloride salt (I) and a polyethylene glycol (PEG)/polypropylene glycol (PPG) block copolymer.