Preparation of biodegradable polyesters with low-burst properties by supercritical fluid extraction

US8324343B2 · kind B2 · utility

Assignee

• Tolmar Therapeutics, Inc. · US

Inventors

• Lester Moore · Port Aransas, US
• Richard L. Norton · Fort Collins, US

Key dates

• Filing date: Oct 13, 2011
• Grant date: Dec 4, 2012
• Expiry date: Oct 13, 2031

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02P20/54
• WIPO field: Pharmaceuticals
• WIPO sector: Chemistry

Abstract

The invention provides methods of extracting a biodegradable polyester with a supercritical fluid effective to obtain a purified biodegradable polyester, such as a purified biodegradable poly(lactide-glycolide) (PLG). The supercritical fluid can be carbon dioxide at an elevated pressure, or can be carbon dioxide with one or more cosolvents. Methods for carrying out stepwise purification of the biodegradable polyester at multiple pressures or multiple temperatures, or both, are also provided. When the polyester is PLG, a purified PLG copolymer is obtained having a narrowed molecular weight distribution with respect to the unpurified polyester. The purified PLG copolymer can have a polydispersity index of less than about 1.7, less than about 2% monomers, and less than about 10% oligomers. The purified PLG copolymer can exhibit a reduced initial burst effect when incorporated into a controlled release formulation such as a flowable implant adapted to be injected into body tissues.