Nandini Katre - Academia.edu (original) (raw)

Papers by Nandini Katre

Journal of Immunology, 1990

Human rIL-2, expressed and purified from Escherichia coli, is currently being tested as an antica... more Human rIL-2, expressed and purified from Escherichia coli, is currently being tested as an anticancer therapeutic agent. Some of the patients undergoing clinical trials with rIL-2 have developed antibodies to rIL-2. We describe a chemical modification of rIL-2 that reduces its immunogenicity. rIL-2 has been chemically modified with a water soluble polymer, monomethoxy polyethylene glycol (PEG). This covalent conjugate PEG-rIL-2 has enhanced solubility and extended in vivo circulation. Attachment of PEG to rIL-2 reduces its immunogenicity when tested in rabbits and in mice. Ag-specific IgG antibody titers were 100 to 1000-fold lower when PEG-rIL-2 was used as the Ag, compared to rIL-2. In a long term study, 7 of 10 rabbits injected with PEG-rIL-2 had no Ag-specific IgG antibody response. In these seven rabbits, the in vivo behavior of the injected PEG-rIL-2 remained essentially unchanged after repeated immunizations. PEG-rIL-2 injected before rIL-2 injections, immunosuppressed the antibody response to rIL-2 in rabbits. The maintenance of the systemic exposure of PEG-rIL-2 after repetitive dosing is related to its decreased immunogenicity. Thus, the PEGylation (covalent attachment of PEG) of rIL-2-enhances its potential as an anticancer therapeutic.

Archives of Biochemistry and Biophysics, Dec 1, 1977

ABSTRACT

Developments in biological standardization, 1992

Native human interleukin-2 (IL-2) comprises a group of glycoproteins of MW 13,000-17,500. Recombi... more Native human interleukin-2 (IL-2) comprises a group of glycoproteins of MW 13,000-17,500. Recombinant human IL-2 (rhIL-2) (Cetus) is derived from E. coli and is not glycosylated. We have evaluated several processes for manufacturing rhIL-2, based on different chaotropic agents for solubilization of insoluble protein pastes. Formulation work carried out with material purified by one of these processes is reported here. Our studies have indicated that the presence of a stabilizer in the form of an amorphous excipient, such as amino acids, a non-ionic surfactant (polysorbate 80), hydroxypropyl-beta-cyclodextrin or human serum albumin was essential for preservation of rhIL-2 during lyophilization. Each of these formulations exhibited its own unique problems. We have overcome these problems through a systematic formulation development program and have been successful in developing several lyophilized formulations of rhIL-2 with optimum properties and performance.

The attachment of water-soluble polymers, such as polyethylene glycol (PEG), to proteins has been... more The attachment of water-soluble polymers, such as polyethylene glycol (PEG), to proteins has been an area of exploration for several decades. With the advent of recombinant technology, it became possible to engineer specific amino acid residues into the amino acid sequence of protein therapeutics for polymer conjugation to improve their efficacy. This chapter will cover the evolution of site-specific conjugation of PEGs to cysteine residues engineered on protein therapeutics. The specific attachment of PEG (PEGylation) to cysteine residues is a very viable method because cysteine residues in proteins are less than 1% of the total amino acid content, and most of them are involved in disulfide bonds. The selection of the site(s) on a protein for cysteine mutation to covalently attach a polymer without the loss of its bioactivity is a critical step in the process of enhancing the therapeutic potential of the protein. The approaches to this selection, the various Cys-directed PEGylation...

L'invention concerne un procede de production de liposomes, par exemple des liposomes multive... more L'invention concerne un procede de production de liposomes, par exemple des liposomes multivesiculaires (MVL), contenant un ou plusieurs agents biologiquement actifs, dans lequel la charge des agents actifs dans les liposomes est modulee par ajustement de l'osmolarite du constituant aqueux dans lequel les agents sont dissous avant encapsulation. Afin d'augmenter la charge de l'agent actif, l'osmolarite du constituant aqueux est reduite, et afin de diminuer la charge de l'agent actif, l'osmolarite du constituant aqueux est augmentee. Dans la production de MVL, le procede consiste a dissoudre l'agent actif et un excipient osmotique facultatif dans un premier constituant aqueux encapsule a l'interieur des liposomes. Pour n'importe quelle concentration donnee de medicaments, l'osmolarite du premier constituant aqueux peut etre ajustee par augmentation ou diminution de la concentration ou de la masse moleculaire des excipients osmotiques utilis...

A process for controlling loading of a biologically active to a liposome which includes agent: (a... more A process for controlling loading of a biologically active to a liposome which includes agent: (a) load modulation of a biologically active agent into a liposome by adjusting the osmolarity of an aqueous solution which dissolves the agent, where the osmolarity of the aqueous solution is increased to decrease loading agent, or decreased to increase; and then (b) Encapsulation of the aqueous solution in the liposome.

L'invention concerne une composition pharmaceutique pour des proteines non solubles de manier... more L'invention concerne une composition pharmaceutique pour des proteines non solubles de maniere stable. La proteine est l'IL-2 et la composition preferee comprend des acides amines, des vitamines, des polymeres des acides gras ou des acides de faible masse moleculaire.

Journal of Controlled Release, 2000

A major challenge in the development of sustained-release formulations for protein and peptide dr... more A major challenge in the development of sustained-release formulations for protein and peptide drugs is to achieve high drug loading sufficient for prolonged therapeutic effect coupled with a high recovery of the protein / peptide. This challenge has been successfully met in the formulation of several peptide and protein drugs using the DepoFoamE, multivesicular lipid-based drug delivery system. DepoFoam technology consists of novel multivesicular liposomes characterized by their unique structure of multiple non-concentric aqueous chambers surrounded by a network of lipid membranes. The objective of this paper is to demonstrate that DepoFoam technology can be used to develop sustained-release formulations of therapeutic proteins and peptides with high loading. DepoFoam formulations of a protein such as insulin, and peptides such as leuprolide, enkephalin and octreotide have been developed and characterized. The data show that these formulations have high drug loading, high encapsulation efficiency, low content of free drug in the suspension, little chemical change in the drug caused by the formulation process, narrow particle size distribution, and spherical particle morphology. Drug release assays conducted in vitro in biological suspending media such as human plasma indicate that these formulations provide sustained release of encapsulated drug over a period from a few days to several weeks, and that the rate of release can be modulated. In vivo pharmacodynamic studies in rats also show a sustained therapeutic effect over a prolonged period. These results demonstrate that the DepoFoam system is capable of efficiently encapsulating therapeutic proteins and peptides and effectively providing controlled delivery of these biologically active macromolecules.

Biophysical Journal, 1986

Divalent cations are involved in the function of bacteriorhodopsin (bR) as a light-driven proton ... more Divalent cations are involved in the function of bacteriorhodopsin (bR) as a light-driven proton pump. If cations are removed from purple membranes they become blue. Divalent cations such as Ca2" or Pb2+ or trivalent ions, can be stoichiometrically titrated back on to these deionized membranes. The color transitions as a function of ion concentration for Ca2" or Pb2+ are precisely comparable and indicate that approximately three stoichiometric equivalents of cations are required to effect the color transition (Kimura et al., 1984). We found four main partially occupied binding sites for cations at a stoichiometric ratio of 3 Pb2+/bR. We localized the binding sites for Pb2+ using x-ray diffraction of membranes reconstituted with 1, 2, and 3 equivalents of Pb2+ per bR. The site of highest affinity is located on helix 7. At 2 Pb2+/bR, sites on helix 6 and between helix 2 and 3 are occupied. At 3 Pb2+/bR a fourth site above helix 3 is occupied.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1980

The uncoupler of mitochondrial oxidative phosphorylation, 2-nitro-4-azido-carbonylcyanide phenylh... more The uncoupler of mitochondrial oxidative phosphorylation, 2-nitro-4-azido-carbonylcyanide phenylhydrazone (N3CCP) which is capable of photoaffinity labeling has been used to examine the effect of uncouplers on the energy conserving membrane of Paracoccus denitrificans and Tetrahymena pyriformis. The N3CCP uncouples respiration in P. denitrificans and T. pyriformis cells with U1/2 values of 1.05 microM and 0.24 microM, respectively. Binding studies show the presence of 0.65 +/- 0.05 high affinity sites per cytochrome alpha with Kd of 0.5 +/- 0.1 microM in P. denitrificans membranes and 1.4 +/- 0.2 sites per cytochrome alpha 2 with a Kd of 0.4 +/- 0.1 microM in T. pyriformis membranes. Irradiation of [3H]-N3CCP bound to the membranes leads to a covalent linking of the radioactive uncoupler to a peptide of 10--15 kdaltons as analyzed by SDS-polyacrylamide gel electrophoresis. It is concluded that these two microbial systems contain a specific high affinity uncoupler binding site very similar to that of mammalian mitochondria (Katre, N.V. and Wilson, D.F. (1978) Arch. Biochem. Biophys. 191, 647--656).

Journal of Immunology, 1990

Human rIL-2, expressed and purified from Escherichia coli, is currently being tested as an antica... more Human rIL-2, expressed and purified from Escherichia coli, is currently being tested as an anticancer therapeutic agent. Some of the patients undergoing clinical trials with rIL-2 have developed antibodies to rIL-2. We describe a chemical modification of rIL-2 that reduces its immunogenicity. rIL-2 has been chemically modified with a water soluble polymer, monomethoxy polyethylene glycol (PEG). This covalent conjugate PEG-rIL-2 has enhanced solubility and extended in vivo circulation. Attachment of PEG to rIL-2 reduces its immunogenicity when tested in rabbits and in mice. Ag-specific IgG antibody titers were 100 to 1000-fold lower when PEG-rIL-2 was used as the Ag, compared to rIL-2. In a long term study, 7 of 10 rabbits injected with PEG-rIL-2 had no Ag-specific IgG antibody response. In these seven rabbits, the in vivo behavior of the injected PEG-rIL-2 remained essentially unchanged after repeated immunizations. PEG-rIL-2 injected before rIL-2 injections, immunosuppressed the antibody response to rIL-2 in rabbits. The maintenance of the systemic exposure of PEG-rIL-2 after repetitive dosing is related to its decreased immunogenicity. Thus, the PEGylation (covalent attachment of PEG) of rIL-2-enhances its potential as an anticancer therapeutic.

Archives of Biochemistry and Biophysics, Dec 1, 1977

ABSTRACT

Developments in biological standardization, 1992

Native human interleukin-2 (IL-2) comprises a group of glycoproteins of MW 13,000-17,500. Recombi... more Native human interleukin-2 (IL-2) comprises a group of glycoproteins of MW 13,000-17,500. Recombinant human IL-2 (rhIL-2) (Cetus) is derived from E. coli and is not glycosylated. We have evaluated several processes for manufacturing rhIL-2, based on different chaotropic agents for solubilization of insoluble protein pastes. Formulation work carried out with material purified by one of these processes is reported here. Our studies have indicated that the presence of a stabilizer in the form of an amorphous excipient, such as amino acids, a non-ionic surfactant (polysorbate 80), hydroxypropyl-beta-cyclodextrin or human serum albumin was essential for preservation of rhIL-2 during lyophilization. Each of these formulations exhibited its own unique problems. We have overcome these problems through a systematic formulation development program and have been successful in developing several lyophilized formulations of rhIL-2 with optimum properties and performance.

The attachment of water-soluble polymers, such as polyethylene glycol (PEG), to proteins has been... more The attachment of water-soluble polymers, such as polyethylene glycol (PEG), to proteins has been an area of exploration for several decades. With the advent of recombinant technology, it became possible to engineer specific amino acid residues into the amino acid sequence of protein therapeutics for polymer conjugation to improve their efficacy. This chapter will cover the evolution of site-specific conjugation of PEGs to cysteine residues engineered on protein therapeutics. The specific attachment of PEG (PEGylation) to cysteine residues is a very viable method because cysteine residues in proteins are less than 1% of the total amino acid content, and most of them are involved in disulfide bonds. The selection of the site(s) on a protein for cysteine mutation to covalently attach a polymer without the loss of its bioactivity is a critical step in the process of enhancing the therapeutic potential of the protein. The approaches to this selection, the various Cys-directed PEGylation...

L'invention concerne un procede de production de liposomes, par exemple des liposomes multive... more L'invention concerne un procede de production de liposomes, par exemple des liposomes multivesiculaires (MVL), contenant un ou plusieurs agents biologiquement actifs, dans lequel la charge des agents actifs dans les liposomes est modulee par ajustement de l'osmolarite du constituant aqueux dans lequel les agents sont dissous avant encapsulation. Afin d'augmenter la charge de l'agent actif, l'osmolarite du constituant aqueux est reduite, et afin de diminuer la charge de l'agent actif, l'osmolarite du constituant aqueux est augmentee. Dans la production de MVL, le procede consiste a dissoudre l'agent actif et un excipient osmotique facultatif dans un premier constituant aqueux encapsule a l'interieur des liposomes. Pour n'importe quelle concentration donnee de medicaments, l'osmolarite du premier constituant aqueux peut etre ajustee par augmentation ou diminution de la concentration ou de la masse moleculaire des excipients osmotiques utilis...

A process for controlling loading of a biologically active to a liposome which includes agent: (a... more A process for controlling loading of a biologically active to a liposome which includes agent: (a) load modulation of a biologically active agent into a liposome by adjusting the osmolarity of an aqueous solution which dissolves the agent, where the osmolarity of the aqueous solution is increased to decrease loading agent, or decreased to increase; and then (b) Encapsulation of the aqueous solution in the liposome.

L'invention concerne une composition pharmaceutique pour des proteines non solubles de manier... more L'invention concerne une composition pharmaceutique pour des proteines non solubles de maniere stable. La proteine est l'IL-2 et la composition preferee comprend des acides amines, des vitamines, des polymeres des acides gras ou des acides de faible masse moleculaire.

Journal of Controlled Release, 2000

A major challenge in the development of sustained-release formulations for protein and peptide dr... more A major challenge in the development of sustained-release formulations for protein and peptide drugs is to achieve high drug loading sufficient for prolonged therapeutic effect coupled with a high recovery of the protein / peptide. This challenge has been successfully met in the formulation of several peptide and protein drugs using the DepoFoamE, multivesicular lipid-based drug delivery system. DepoFoam technology consists of novel multivesicular liposomes characterized by their unique structure of multiple non-concentric aqueous chambers surrounded by a network of lipid membranes. The objective of this paper is to demonstrate that DepoFoam technology can be used to develop sustained-release formulations of therapeutic proteins and peptides with high loading. DepoFoam formulations of a protein such as insulin, and peptides such as leuprolide, enkephalin and octreotide have been developed and characterized. The data show that these formulations have high drug loading, high encapsulation efficiency, low content of free drug in the suspension, little chemical change in the drug caused by the formulation process, narrow particle size distribution, and spherical particle morphology. Drug release assays conducted in vitro in biological suspending media such as human plasma indicate that these formulations provide sustained release of encapsulated drug over a period from a few days to several weeks, and that the rate of release can be modulated. In vivo pharmacodynamic studies in rats also show a sustained therapeutic effect over a prolonged period. These results demonstrate that the DepoFoam system is capable of efficiently encapsulating therapeutic proteins and peptides and effectively providing controlled delivery of these biologically active macromolecules.

Biophysical Journal, 1986

Divalent cations are involved in the function of bacteriorhodopsin (bR) as a light-driven proton ... more Divalent cations are involved in the function of bacteriorhodopsin (bR) as a light-driven proton pump. If cations are removed from purple membranes they become blue. Divalent cations such as Ca2" or Pb2+ or trivalent ions, can be stoichiometrically titrated back on to these deionized membranes. The color transitions as a function of ion concentration for Ca2" or Pb2+ are precisely comparable and indicate that approximately three stoichiometric equivalents of cations are required to effect the color transition (Kimura et al., 1984). We found four main partially occupied binding sites for cations at a stoichiometric ratio of 3 Pb2+/bR. We localized the binding sites for Pb2+ using x-ray diffraction of membranes reconstituted with 1, 2, and 3 equivalents of Pb2+ per bR. The site of highest affinity is located on helix 7. At 2 Pb2+/bR, sites on helix 6 and between helix 2 and 3 are occupied. At 3 Pb2+/bR a fourth site above helix 3 is occupied.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1980

The uncoupler of mitochondrial oxidative phosphorylation, 2-nitro-4-azido-carbonylcyanide phenylh... more The uncoupler of mitochondrial oxidative phosphorylation, 2-nitro-4-azido-carbonylcyanide phenylhydrazone (N3CCP) which is capable of photoaffinity labeling has been used to examine the effect of uncouplers on the energy conserving membrane of Paracoccus denitrificans and Tetrahymena pyriformis. The N3CCP uncouples respiration in P. denitrificans and T. pyriformis cells with U1/2 values of 1.05 microM and 0.24 microM, respectively. Binding studies show the presence of 0.65 +/- 0.05 high affinity sites per cytochrome alpha with Kd of 0.5 +/- 0.1 microM in P. denitrificans membranes and 1.4 +/- 0.2 sites per cytochrome alpha 2 with a Kd of 0.4 +/- 0.1 microM in T. pyriformis membranes. Irradiation of [3H]-N3CCP bound to the membranes leads to a covalent linking of the radioactive uncoupler to a peptide of 10--15 kdaltons as analyzed by SDS-polyacrylamide gel electrophoresis. It is concluded that these two microbial systems contain a specific high affinity uncoupler binding site very similar to that of mammalian mitochondria (Katre, N.V. and Wilson, D.F. (1978) Arch. Biochem. Biophys. 191, 647--656).