A bioresorbable polymer is obtained by reacting together (a) a prepolymer comprising co-polymerised units of a caprolactone and poly(alkylene oxide) moieties; (b) a polycaprolactone diol comprising co-polymerised units of a caprolactone and a C2-C6 diol; and (c) a diisocyanate. The polymer may be loaded with a pharmaceutically active agent to produce a drug delivery device.