Characterization of poly(glycolide-co-D,L-lactide)/poly(D,L-lactide) microspheres for controlled release of GM-CSF.
OBJECTIVE
This study describes the preparation and characterization of a controlled release formulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) encapsulated in poly(glycolide-co-D,L-lactide) (PLGA) and poly(D,L-lactide) (PLA) microspheres.


METHODS
GM-CSF was encapsulated in PLGA/PLA microspheres by a novel silicone oil based phase separation process. Several different blends of PLGA and low molecular weight PLA were used to prepare the microspheres. The microspheres and the encapsulated GM-CSF were extensively characterized both in vitro and in vivo.


RESULTS
Steady release of GM-CSF was achieved over a period of about one week without significant "burst" of protein from the microspheres. Analysis of microsphere degradation kinetics by gel permeation chromatography (GPC) indicated that low molecular weight PLA enhanced the degradation of the PLGA and thereby affected release kinetics. GM-CSF released from the microspheres was found to be biologically active and physically intact by bioassay and chromatographic analysis. Analysis of serum from mice receiving huGM-CSF indicated that the GM-CSF was biologically active and that a concentration of greater than 10 ng/mL was maintained for a period lasting at least nine days. MuGM-CSF was not detected following in vivo administration of muGM-CSF microspheres. The tissues of mice receiving muGM-CSF microspheres were characterized by infiltration of neutrophils, and macrophages which were in significant excess of those found in mice administered with placebo controls (i.e. microspheres without GM-CSF).


CONCLUSIONS
This study demonstrates the influence of formulation parameters on the encapsulation of GM-CSF in PLGA/PLA microspheres and its controlled release in biologically active form. The intense local tissue reaction in mice to muGM-CSF microspheres demonstrates the importance of the mode of delivery on the pharmacologic activity of GM-CSF.
Pettit
D K
DK
Department of Analytical Chemistry and Formulation, Immunex Corporation, Seattle, Washington 98101, USA. pettitd@immunex.com
Lawter
J R
JR
Huang
W J
WJ
Pankey
S C
SC
Nightlinger
N S
NS
Lynch
D H
DH
Schuh
J A
JA
Morrissey
P J
PJ
Gombotz
W R
WR
D000818:Animals; D003692:Delayed-Action Preparations; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage / Q000737:chemistry* / Q000493:pharmacokinetics; D006651:Histocytochemistry; D006801:Humans; D007279:Injections, Subcutaneous; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D051379:Mice; D008810:Mice, Inbred C57BL; D008863:Microspheres; D011091:Polyesters; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D011994:Recombinant Proteins
D003692:Delayed-Action Preparations; D011091:Polyesters; D011108:Polymers; D011994:Recombinant Proteins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C033616:poly(lactide); D016178:Granulocyte-Macrophage Colony-Stimulating Factor