“Burst-free” sustained release poly-(lactide/glycolide) microspheres

• US 7,033,608 B1
• Filed: 06/22/1999
• Issued: 04/25/2006
• Est. Priority Date: 05/22/1995
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Reid, Robert H., Setterstrom, Jean A., Van Hamont, John E., McQueen, Charles E., Jevanthi, Ramasubbu, Roberts, F. Donald, Friden, Phil
• Primary Examiner(s): Page, Thurman K.
• Assistant Examiner(s): TRAN, SUSAN T
• Application Number:
  US09/337,945
• Time in Patent Office: 2,499 Days
• Field of Search: 424/489, 424/490, 424/491, 424/493, 424/496, 424/501
• US Class Current: 424/490
• CPC Class Codes: A61K 9/5031 obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyethylene glycol, poly(lactide-co-glycolide)

Abstract

Novel burst-free, sustained release biocompatible and biodegrable microcapsules which can be programmed to release their active core for variable durations ranging from 1–100 days in an aqueous physiological environment. The microcapsules are comprised of a core of polypeptide or other biologically active agent encapsulated in a matrix of poly(lactide/glycolide) copolymer as a blend of uncapped (free carboxyl end group) and end-capped forms ranging in ratios from 100/0 to 1/99.

Claims

1. A process for preparing controlled release microcapsule formulations characterized by burst-free, sustained, programmable release of biologically active agents comprising:

Dissolving biodegradable poly (lactide/glycolide), polymer in a form of uncapped/end-capped blend in a ratio of from 50/50 to 1/99 in methylene chloride, and dissolving a biologically active agent or active core in water;

adding the aqueous layer to the polymer solution and emulsifying to provide an inner water-in-oil (w/o) emulsion;

stabilizing said inner w/o emulsion in a solvent-saturated aqueous phase containing an oil-in-water (o/w) emulsifier;

emulsifying said inner w/o emulsion in an external aqueous layer containing oil-in-water emulsifier to form a ternary emulsion; and

stirring the resulting water-in-oil-in-water (w/o/w) emulsion for sufficient time to remove said solvent to harden microcapsules, and rinsing the hardened microcapsules with water and lyophilizing said hardened microcapsules.

2. The process of claim 1 wherein a solvent-saturated external aqueous phase is added to emulsify the inner w/o emulsion prior to addition of the external aqueous layer, to provide microcapsules of narrow size distribution range between 0.05–

500 μ

m.

3. The process of claim 1 wherein a low temperature of about 0–

4°

C. is provided during preparation of the inner w/o emulsion, and a low temperature of about 4–

20°

C. is provided during preparation of the w/o/w emulsion to provide a stable emulsion and high encapsulation efficiency.

4. The process of claim 1 wherein a the blend of uncapped and end-capped polymer is used to provide release of the active core in a continous and sustained manner without a lag phase.