Biodegradable block copolymer drug delivery composition

An injectable biodegradable drug delivery composition comprising:

• (i) a mixture of at least three different block copolymers, wherein each block copolymer is:
• (a) a biodegradable triblock copolymer having the formula:
• Av-Bw-Ax
• wherein A is a polyester and B is polyethylene glycol and v and x are the number of repeat units ranging from 1 to 3,000 and w is the number of repeat units ranging from 3 to 300 and v=x or v≠x;
• or
• (b) a biodegradable diblock copolymer having the formula:
• Cy-Az
• wherein A is a polyester and C is an end-capped polyethylene glycol and y and z are the number of repeat units with y ranging from 2 to 250 and z ranging from 1 to 3,000;
• and
• wherein the mixture comprises at least one (a) and at least one (b);
• and the weight ratio of the sum of the biodegradable triblock copolymers of (a) and the sum of the biodegradable diblock copolymers of (b) is 1:19 to 5:1;
• and
• (ii) at least one pharmaceutically active ingredient;
• wherein the release kinetics of said at least one active ingredient from said biodegradable drug delivery composition can be modulated without adversely affecting injectability and/or viscosity before injection of the injectable biodegradable drug delivery composition and/or depot robustness after injection of the biodegradable drug delivery composition, compared to a composition having a single biodegradable triblock of the copolymer of (a) and a single biodegradable diblock of the copolymer of (b).