Protein Delivery (eBook)

Contributors 6
Preface to the Series 9
Preface 11
Contents 13
Protein Delivery from Biodegradable Microspheres 22
1. INTRODUCTION 22
2. COMPONENTS FOR SUCCESSFUL DEVELOPMENT OF MICROSPHERE FORMULATIONS 24
2.1. Polymer Chemistry 24
2.2. Engineering of Microsphere Formulations 29
2.3. Protein Stability 42
3. CASE STUDIES OF DRUG DELIVERY FROM BIODEGRADABLE MICROSPHERES 45
3.1. LupronDepot 45
3.2. MNrgp120 Controlled Release Vaccine 47
4. IMMUNOGENICITY AND INJECTION- SITE CONSIDERATIONS 51
5. REGULATORY REQUIREMENTS FOR DEVELOPMENT OF PROTEIN DELIVERY FROM MICROSPHERES 55
5.1. Toxicology Studies 55
5.2. Residual Solvent Concerns 56
5.3. Manufacturing Issues 57
5.4. Preclinical Animal Models and Clinical Experiments 58
6. SUMMARY 59
REFERENCES 60
Degradable Controlled Release Systems Useful for Protein Delivery 65
1. INTRODUCTION 65
2. DEFINITIONS 68
3. SYNTHETIC HYDROPHOBIC DEGRADABLE POLYMERS 69
3.1. Poly(lactic acid), Poly(glycolic acid), and Their Copolymers 69
3.2. Polycaprolactone 75
3.3. Poly(hydroxybutyrate), Poly(hydroxyvalerate), and Their Copolymers 76
3.4. Poly(ortho esters) 77
3.5. Polyanhydrides 81
3.6. Polyphosphazenes 85
3.7. Delivery of Vaccines 85
4. HYDROPHILIC POLYMERIC BIOMATERIALS AND HYDROPHOBIC NONPOLYMERIC BIOMATERIALS 90
4.1. General 90
4.2. Specific Hydrophilic Polymeric Biomaterials 91
4.3. Specific Hydrophobic Nonpolymeric Biomaterials 99
4.4. Miscellaneous 101
5. CONCLUSIONS 102
REFERENCES 103
Delivery of Proteins from a Controlled Release Injectable Implant 113
1. THE ATRIGEL ™ DRUG DELIVERY SYSTEM 113
2. EFFECTS OF FORMULATION VARIABLES ON PROTEIN RELEASEKINETICS 115
2.1. Polymer Type 116
2.2. Polymer Concentration 117
2.3. Polymer Molecular Weight 118
2.4. Solvent 119
2.5. Protein Load 120
2.6. Additives 121
3. CHARACTERIZATION 122
3.1. Protein Quantitation in Different ReleaseMedia 122
3.2. Protein Structure 125
3.3. Enzyme Activity 127
3.4. Cellular Bioactivity 128
4. IN VIVO EVALUATIONS 130
4.1. Biocompatibility 130
4.2. Protein Release Kinetics 131
4.3. Bioactivity 133
5. CONCLUSIONS 135
REFERENCES 136
Protein Delivery from Nondegradable Polymer Matrices 138
1. INTRODUCTION 138
1.1. Biocompatible Polymers Used as Hydrophobic Matrices 139
1.2. Protein Release from Polymer Matrices 141
2. MECHANISMS AND MODELS FOR PROTEIN RELEASE FROM MATRICES 143
2.1. Macroscopic Models of Diffusion in Porous Polymer Matrices 144
2.2. Microscopic Models of Diffusion in Porous Polymer Matrices 150
3. APPLICATIONS OF PROTEIN/ POLYMER MATRIX SYSTEMS 151
3.1. Topical Delivery 152
3.2. Targeted Delivery of Proteins to Specific Tissue Regions 152
3.3. Systemic Delivery for Extended Periods 153
REFERENCES 153
Diffusion-Controlled Delivery of Proteins from Hydrogels and Other Hydrophilic Systems 157
1. INTRODUCTION 157
1.1. Mechanisms of Protein Diffusion 158
1.2. Structure of Hydrophilic Polymers 160
1.3. Methods for Loading Proteins into Hydrogels 162
2. DIFFUSION- CONTROLLED DELIVERY SYSTEMS 163
2.1. Reservoir Systems 163
2.2. Matrix Systems 165
2.3. Biodegradable Hydrogels 167
3. FACTORS AFFECTING THE DIFFUSION OF PROTEINS 169
3.1. Environmental Conditions 169
3.2. Hydrogel Structure 170
4. TECHNIQUES FOR MEASUREMENT OF THE DIFFUSION COEFFICIENT 171
4.1. Membrane Permeation Method 173
4.2. Absorption/Desorption Method 175
4.3. Scanning Electron Microscopy (SEM) 178
4.4. Fourier Transform Infrared (FTIR) Spectroscopy 178
4.5. Quasi-Elastic Light Scattering (QELS) Method 179
4.6. Other Techniques 180
REFERENCES 180
Poly(ethyleneglycol)-CoatedNanospheres: Potential Carriers for Intravenous Drug Administration 184
1. Introduction 184
1.1. Approaches to Increase Particle Blood Circulation Time 186
1.2. PEG Hydrophilic Coatings: Mechanism of Protein Rejection 187
2. PEG-COATED LONG-CIRCULATING DRUG CARRIERS 188
3. PEG-COATED BIODEGRADABLE NANOSPHERES POTENTIAL LONG-CIRCULATING DRUG CARRIERS 190
3.1. Biodegradable Polymers Containing PEG Blocks 191
3.2. Preparation of PEG- Coated Nanospheres 193
4. NANOSPHERE CHARACTERIZATION 194
4.1. Morphology Studies 194
4.2. Size Distribution Measurement 196
4.3. Detection and Stability of the PEG Coating 197
4.4. Surface Hydrophobicity and Charge Determination 198
5. DRUG ENCAPSULATION IN PEG- COATED NANOSPHERES 200
5.1. Drug Encapsulation and Release Properties 200
5.2. Parameters Influencing Drug Release 201
6. STUDIES (PHAGOCYTOSIS ASSAY) 204
7. BLOOD HALF-LIFE AND ORGAN DISTRIBUTION OF PEG COATED NANOSPHERES 205
8. CONCLUSION 209
REFERENCES 210
Multiple Emulsions for the Delivery of Proteins 216
1. INTRODUCTION 216
2. METHODS OF PREPARATION 217
3. STABILITY ISSUES 218
3.1. Background 218
3.2. Surfactant Migration 219
3.3. Osmotic Gradients 219
3.4. Process Denaturation of Protein 219
3.5. Methods to Determine Physical Stability 220
4. APPLICATIONS 220
4.1. Parenteral Administration 220
4.2. Oral Administration 221
5. SOLID- STATE EMULSIONS 222
5.1. Method of Preparation 223
5.2. Physical Properties of Solid- state Emulsions 223
5.3. Oral Administration of Vancomycin Solid- state Emulsion 224
6. MISCELLANEOUS APPLICATIONS 225
6.1. Vaccine Adjuvants 225
6.2. Enzyme Immobilization 225
7. SUMMARY 226
REFERENCES 226
Transdermal Peptide Delivery Using Electroporation 229
1. INTRODUCTION 229
2. RESULTS AND DISCUSSION 233
2.1. In Vitro Transport 233
2.2. Isolated Perfused Porcine Skin Flap 243
2.3. Skin Toxicology following Electroporation 248
3. CONCLUSION 251
REFERENCES 251
Protein Delivery with Infusion Pumps 255
1. INTRODUCTION 255
1.1. Rationale for Infusion Therapy 255
1.2. Limitations of Infusion Therapy 258
2. HISTORY OF INFUSION THERAPY 259
3. STATIONARY AND PORTABLE INFUSION PUMPS 261
3.1. Stationary Infusion Pumps 262
3.2. Implantable Infusion Pumps 265
3.3. External Infusion Pumps 266
4. SUMMARY 268
REFERENCES 269
Oral Delivery of Microencapsulated Proteins 271
1. INTRODUCTION 271
2. MECHANISMS OF INTESTINAL ABSORPTION OF PROTEINS AND PEPTIDES 273
2.1. Passive Diffusion 273
2.2. Carrier-Mediated Transport 275
2.3. Receptor-Mediated and Non-Receptor-Mediated Endocytosis 277
3. MECHANISMS OF INTESTINAL ABSORPTION OF MICROPARTICULATES 280
3.1. Transcellular Pathway 281
3.2. Paracellular Transport 283
3.3. Liposome Absorption 284
4. CASE STUDIES 285
4.1. Introduction 285
4.2. Polyester Microspheres 286
4.3. Zein Microspheres 287
4.4. Proteinoid Microspheres 288
4.5. Polycyanoacrylate Microspheres 289
4.6. Lipid-Based Systems 291
5. CONCLUSION 293
REFERENCES 293
Controlled Delivery of Somatotropins 305
1. INTRODUCTION 305
2. PREFORMULATION DEVELOPMENT 307
2.1. Solution Stability 307
2.2. Molecular Modification 309
3. IN JECTABLES 311
3.1. Oil-Based Gel Depots 311
3.2. Microsphere Systems 315
3.3. Liposomes 317
3.4 Emulsions 317
3.5. Aqueous Gels and Complexes 318
4. IMPLANTS 319
4.1. Uncoated Implants 319
4.2. Coated Implants 321
5. OSMOTIC DEVICES 326
6. MISCELLANEOUS SYSTEMS 328
6.1. Wound Healing 328
6.2. Nasal Delivery Systems 329
7. CONCLUSIONS 329
ACKNOWLEDGMENTS 329
REFERENCES 329
Insulin Iontophoresis 334
1. INTRODUCTION 334
2. SPECIFIC DRUG DELIVERY REQUIREMENTS FOR INSULIN 337
2.1. Duplicating the Function of the Pancreas 337
2.2. Candidate Systems for Insulin Delivery 338
3. CAPABILITIES OF IONTOPHORESIS RELATED TO INSULIN DELIVERY 341
3.1. Noninvasive Delivery of Insulin 342
3.2. Control of Delivery Rate of Insulin 342
3.3. Bolus Administration 342
3.4. Dose Precision 343
3.5. Portal Delivery 343
3.6. Bioavailability 343
3.7. Compliance 344
3.8. Summary of Capabilities Related to Insulin Delivery 345
4. THEORETICAL LIMITATIONS AND PUBLISHED RESULTS 345
4.1. Published Results of Insulin Iontophoresis 345
4.2. Theoretical and Practical Limitations to Insulin Iontophoresis 348
5. PHYSICOCHEMICAL PROPERTIES OF INSULIN RELATED TO IONTOPHORESIS 351
5.1. Charge Titration 351
5.2. Solubility 352
5.3. Enzymatic Degradation 353
5.4. Insulin Self-Association 353
6. FUTURE PROSPECTS FOR IONTOPHORETIC DELIVERY OF INSULIN 354
REFERENCES 355
Insulin Formulation and Delivery 357
1. INTRODUCTION 357
2. FORMULATION OF INSULIN 358
2.1. Introduction 358
2.2. Formulation for Parenteral Administration 359
2.3. Formulation for Alternative Routes 365
2.4. Insulin Analogs and Derivatives 366
3. DELIVERY OF INSULIN 369
3.1. Introduction 369
3.2. Parenteral Insulin Delivery 371
3.3. Alternative Routes of Insulin Delivery 382
4. SUMMARY AND FUTURE PERSPECTIVES 399
REFERENCES 400
Index 425

Chapter 3
Delivery of Proteins from a Controlled Release Injectable Implant (p. 93-94)

GeraldL. Yewey, Ellen G. Duysen,
S. Mark Cox, and Richard L. Dunn

1. THE ATRIGEL™ DRUG DELIVERY SYSTEM

Development of controlled release systems for the delivery of recombinant proteins remains a critical research challenge for the biotechnology industry. Current therapies with these biopharmaceutical agents require frequent injections or infusion owing to the short half-lives of the proteins (Bodmer et al., 1992). Biodegradable implants and microspheres for parenteral administration could extend the half-life of serum-labile proteins and provide an effective mechanism for localized as well as systemic delivery. Although such sustained release therapies may result in higher formulation costs, they have the potential to reduce overall medical costs by decreasing the frequency of administration. They are also more convenient for the patient to use, with a resulting improvement in compliance. Biodegradable systems that allow repetitive courses of therapy to be administered without the need for a subsequent medical procedure to remove the device contribute even more to lower costs.

Recently, a liquid polymer system (ATRIGEL™) has been developed which has both the simplicity and control of solid biodegradable implants and the injectability of microspheres for delivering drugs (Dunn et al., 1992). This drug delivery system combines a biodegradable polymer with a biocompatible solvent, resulting in a solution that can be injected using standard syringes and needles. When the system contacts physiologic fluid, the polymer precipitates as the solvent diffuses into the surrounding tissues. As a result, a biodegradable polymeric implant is formed. For controlled release applications, a drug can be incorporated into the delivery system. The incorporated drug is physically entrapped within the precipitated polymer matrix and is then slowly released. The polymer type, concentration, and molecular weight as well as the carrier solvent, drug load and formulation additives each influence the release kinetics. Manipulation of these formulation variables provides diverse drug delivery profiles as well as polymer biodegradation rates for specific applications.

Candidate biodegradable polymers for use in the drug delivery system include homopolymers of poly( DL -lactide) (PLA) and copolymers of poly(DL -lactide-co-glycolide) (PLG) and poly(DL-lactide-co-caprolactone) (PLC). These polymers are similar in chemical composition to biodegradable sutures and have been well characterized in the literature (Kulkarni et al., 1971, Cutright et al., 1971, Gourlay et al., 1978, Rice et al., 1978, Nakamura et al., 1989). They are well tolerated in the body and generally accepted as safe by the medical/pharmaceutical community. Biodegradation of the polymers is effected by their hydrolysis to lactic, glycolic, and hydroxycaproic acids, respectively. These are either metabolized by the Krebs (or tricarboxylic acid) cycle to CO2 and H2O (Brady et al., 1973, Gilding, 1981, Woodward et al., 1985, Hollinger and Battistone, 1986) or, in the case of D-lactic acid, are excreted unchanged by the kidney. Biocompatible solvents utilized with the system include N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). Safety studies conducted with pharmaceutical-grade solvents provide extensive toxicological profiles that support substantial margins of safety for both the neat solvents and ATRIGEL™ formulations prepared with these solvents (Wilson et al., 1965, Jacob and Wood, 1971, David, 1972, Bartsch et al., 1976, Wells and Digenis, 1988, Shirley et al., 1988, Wells et al., 1992, International Specialty Products, unpublished results).