Extended release microparticles and suspensions thereof for medical therapy

A solid aggregating biodegradable microparticle comprising a prodrug of a therapeutically active compound, encapsulated in (a) poly(lactic-co-glycolic acid) (PLGA) and/or polylactic acid (PLA) and (b) poly(lactic-co-glycolic acid) (PLGA) covalently bound to polyethylene glycol (PEG) and/or polylactic acid (PLA) covalently bound to polyethylene glycol (PEG), and a surfactant, wherein the microparticle

• (i) has a mean diameter between 20 μm and 40 μm;
• (ii) has been surface-modified with a surface-treatment agent to partially degrade surface polymer at a temperature less than about 18° C. wherein the surface-treatment agent is selected from (a) an aqueous base/alcohol, (b) an aqueous acid/alcohol, (c) phosphate buffered saline/alcohol, or (d) water/alcohol;
• (iii) aggregates in vivo to form at least one pellet of at least 500 μm in vivo that provides sustained drug delivery in vivo for at least three months;
• and
• (v) wherein the prodrug is of the formula:
• or a pharmaceutically acceptable salt thereof
• wherein
• y is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10;
• and
• y′ is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.