Liquid inhalation formulation comprising RPL554

A liquid pharmaceutical composition suitable for administration by inhalation comprising a diluent and a suspension of particles of 9,10-dimethoxy-2-(2,4,6-trimethylphenylimino)-3-(N-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one (RPL554) or a pharmaceutically acceptable salt thereof,

• wherein the composition comprises a phosphate buffer at a concentration of less than about 5 mg/mL;
• wherein the particles of RPL554 have a particle size distribution with a Dv50 (median particle size by volume) value of from about 0.2 μm to about 5 μm,
• wherein the concentration of particles of RPL554 in the liquid pharmaceutical composition is from about 0.1 mg/mL to about 6 mg/mL.