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Puja Sapra

Publications and source records attributed to Puja Sapra.

10 recordsLinked to original sources
PubMed2005

Effective therapy of human lymphoma xenografts with a novel recombinant ribonuclease/anti-CD74 humanized IgG4 antibody immunotoxin.

Ranpirnase (Rap) is a cytotoxic ribonuclease (RNase) isolated from frog oocytes. Here we describe high antitumor activity of a novel immunotoxin, 2L-Rap-hLL1-gamma4P, composed of 2 Rap molecules, each fused to the N terminus of the light chain of hLL1, an internalizing anti-CD74 humanized antibody. To reduce unwanted side effects, the constant region of hLL1 was changed from gamma1 to gamma4 and further to gamma4P by replacing serine228 to proline to prevent the formation of a half immunoglobulin G (IgG) common for IgG4. In vitro, 2L-Rap-hLL1-gamma4P retained RNase activity, specific binding to CD74, and was significantly more potent against CD74+ cell lines (Daudi, Raji, and MC/CAR) than naked hLL1. In vivo, the pharmacokinetic profile of 2L-Rap-hLL1-gamma4P was similar to that of naked hLL1. The maximum tolerated dose of 2L-Rap-hLL1-gamma4P in severe combined immunodeficient mice (SCID) or BALB/c mice was 50 microg per mouse. In Raji and Daudi Burkitt lymphoma xenograft models, treatment with a single 5 to 50 microg dose of 2L-Rap-hLL1-gamma4P, given as early or delayed treatment, resulted in cures of most animals. Treatment with 2L-Rap-hLL1-gamma4P was significantly better than all controls, including saline, naked hLL1, and nonspecific immunotoxin. In conclusion, 2L-Rap-hLL1-gamma4P demonstrated excellent in vitro and in vivo efficacy and thus merits further consideration as a therapeutic for CD74+ tumors.

Animals↗
PubMed2005

Anti-CD74 antibody-doxorubicin conjugate, IMMU-110, in a human multiple myeloma xenograft and in monkeys.

PURPOSE: IMMU-110 is a drug immunoconjugate composed of doxorubicin conjugated to the humanized anti-CD74 monoclonal antibody, hLL1, at a doxorubicin/monoclonal antibody ratio of approximately 8:1 (mol/mol). CD74 is a rapidly internalizing molecule associated with HLA-DR, which has high expression by several tumor types. Here, we describe safety evaluations of IMMU-110 in mice and monkeys as well as efficacy studies in a xenograft model of the human multiple myeloma cell line, MC/CAR. EXPERIMENTAL DESIGN: In vitro binding of IMMU-110 was determined by a cell-based ELISA and cytotoxicity of IMMU-110 assayed with a tetrazolium assay. Pharmacokinetics and biodistribution of radiolabeled IMMU-110 were examined in tumor-free BALB/c mice, and the therapeutic effectiveness was evaluated in severe combined immunodeficient mice bearing MC/CAR cells. Acute toxicity of IMMU-110 was studied in CD74-positive cynomolgus monkeys (Macaca fascicularis). RESULTS: In vitro, IMMU-110 specifically binds to CD74 and is cytotoxic against MC/CAR cells. In vivo, IMMU-110 displayed a pharmacokinetic and biodistribution profile identical to that of unconjugated hLL1 monoclonal antibody, except for higher kidney uptake. Treatment with a single dose of IMMU-110 as low as 50 microg antibody/mouse (or 1.4 microg doxorubicin/mouse), 5 days postinjection of the multiple myeloma cells, resulted in cure of most mice. In mice, no host toxicity of IMMU-110 was observed at the highest protein dose tested (125 mg/kg). In cynomolgus monkeys, bone marrow toxicity was observed at 30 and 90 mg/kg doses. CONCLUSIONS: The excellent safety and efficacy profile of IMMU-110 supports clinical testing of this immunoconjugate in the treatment of CD74-positive B-cell malignancies.

Animals↗
PubMed2005

Ligand-targeted liposomes for cancer treatment.

Selective targeting of ligand-targeted liposomes containing anticancer drugs or therapeutic genes to cell surface receptors expressed on cancer cells is a recognized strategy for improving the therapeutic effectiveness of conventional chemotherapeutics or gene therapeutics. Some recent advances in the field of ligand-targeted liposomes for the treatment of cancer are summarized including: selection criteria for the receptors to be targeted, choice of targeting ligands and choice of encapsulated therapeutics. Targeting of liposomes to solid tumors, versus angiogenic endothelial cells versus vascular targets is discussed. Ligand-targeted liposomes have shown considerable promise in preclinical xenograft models and are poised for clinical development.

Animals↗
PubMed2004

Improved outcome when B-cell lymphoma is treated with combinations of immunoliposomal anticancer drugs targeted to both the CD19 and CD20 epitopes.

PURPOSE: We have reported previously that successful immunoliposomal drug therapy with liposomal doxorubicin (DXR) against xenograft B-lymphoma models required targeting against an internalizing B-cell antigen, CD19 (P. Sapra and T. M. Allen. Cancer Res 2002;62:7190-4.). Here we compare targeting of immunoliposomal formulations of DXR with vincristine (VCR) targeted against CD19 versus a noninternalizing (CD20) epitope. We also examine the effect of targeting immunoliposomes with antibody combinations in an attempt to increase the total number of binding sites (apparent antigen density) at the target cell surface. EXPERIMENTAL DESIGN: Cell association of immunoliposomes (CD19-targeted, CD20-targeted, or combinations of the two) with human B-cell lymphoma (Namalwa) cells were studied using radiolabeled liposomes. Therapeutic efficacy of the same formulations was determined in a severe combined immunodeficient murine model. RESULTS: Therapeutic results in severe combined immunodeficient mice bearing Namalwa cells administered anti-CD20-targeted liposomal DXR were barely improved over those found for nontargeted liposomal DXR or free DXR but, surprisingly, administration of anti-CD20-targeted liposomal VCR resulted in a significantly improved therapeutic outcome compared with nontargeted liposomal VCR, free VCR, or anti-CD20-targeted liposomal DXR. Treatment of murine B lymphoma with single injections of combinations of anti-CD19- and anti-CD20-targeted liposomal VCR led to cures in 70% of mice. However, mice injected with similar combinations of liposomal DXR did not have improved survival rates over anti-CD19-targeted liposomal DXR by itself. CONCLUSIONS: The success of immunoliposomal therapy in combination regimens varies with the type of encapsulated drug and the nature of the target epitopes.

Animals↗
PubMed2004

Improved therapeutic responses in a xenograft model of human B lymphoma (Namalwa) for liposomal vincristine versus liposomal doxorubicin targeted via anti-CD19 IgG2a or Fab' fragments.

PURPOSE: Monoclonal antibody-mediated targeting of liposomal anticancer drugs to surface antigens expressed on malignant B cells can be an effective strategy for treating B-cell malignancies. In a murine model of human B-cell lymphoma, we have made in vitro and in vivo comparisons of long-circulating sterically stabilized (Stealth) immunoliposome (SIL) formulations of two anticancer drugs, vincristine (VCR) and doxorubicin (DXR), with different mechanisms of action and drug release rates. EXPERIMENTAL DESIGN: SIL formulations of VCR or DXR were conjugated to the monoclonal antibody anti-CD19 (SIL[alphaCD19]) or its Fab' fragments (SIL[Fab']). Specific binding of SILs to Namalwa cells was studied using radiolabeled liposomes, and cytotoxicities of DXR- or VCR-loaded SILs were quantitated by a tetrazolium assay. Pharmacokinetic and drug leakage experiments were performed in mice using dual-labeled liposomes, and the therapeutic responses of SILs were evaluated in a Namalwa (human B lymphoma) cell xenograft model. RESULTS: SIL[alphaCD19] or SIL[Fab'] had higher association with and cytotoxicity against Namalwa cells than nontargeted liposomes. SIL[Fab'] had longer circulation times than SIL[alphaCD19], and VCR had faster release rates from the liposomes than DXR. SIL formulations of either VCR or DXR had significantly better therapeutic outcomes than nontargeted liposomes or free drugs. SILs loaded with VCR were superior to those loaded with DXR. SIL[Fab'] had better therapeutic outcomes than SIL[alphaCD19] for the drug DXR but were equally efficacious for the drug VCR. CONCLUSIONS: Treatment of a B lymphoma model with single injections of anti-CD19-targeted liposomal formulations of VCR resulted in high levels of response and long-term survivors. Responses to anti-CD19-targeted liposomal DXR were more modest, although the longer circulation times of SIL[Fab'] versus SIL[alphaCD19] led to superior therapeutics for DXR-loaded immunoliposomes.

Animals↗
PubMed2003

Doxorubicin-loaded Fab' fragments of anti-disialoganglioside immunoliposomes selectively inhibit the growth and dissemination of human neuroblastoma in nude mice.

Neuroblastoma (NB) is the most common extracranial solid tumor in children. Intensive therapeutic intervention does not prolong the overall disease-free survival rate for this tumor. NB tumor, but not normal tissues, overexpress the disialoganglioside (GD(2)) at the cell surface. Anti-GD(2) whole antibodies (aGD(2)) or their corresponding Fab' fragments were covalently coupled to Stealth immunoliposomes (aGD(2)-SIL or Fab'-SIL), and their binding to GD(2)-positive NB cells was measured. Cytotoxic effects of immunoliposomes loaded with doxorubicin (DXR) were determined. Radiolabelled immunoliposomes were used to evaluate pharmacokinetics (PK). The effectiveness of different liposomal formulations of DXR was tested against a metastatic model of human NB in nude mice. aGD(2)-SIL and Fab'-SIL showed concentration-dependent specific binding and uptake by GD(2)-positive NB cells. DXR entrapped in aGD(2)-SIL or Fab'-SIL (aGD(2)-SIL[DXR], Fab'-SIL[DXR]) showed higher cytotoxicities than nontargeted liposomes (SL[DXR]). DXR-loaded Fab'-SIL (Fab'-SIL[DXR]) also showed specific binding, uptake, and cytotoxic effects on several GD(2)-positive NB cells in vitro. PK studies showed that Fab'-SIL had long-circulating profiles in blood compared with aGD(2)-SIL, with the PK profile for Fab'-SIL being almost identical to that obtained with nontargeted Stealth liposomes. In vivo, long-term survivors were obtained in mice treated with Fab'-SIL[DXR] but not in untreated animals, or those treated with free aGD(2) Fab', Fab'-SIL (no drug), free-DXR, or nontargeted Stealth liposomes[DXR] (no antibody; P < 0.0001). Immunoliposomes containing DXR prevented the establishment and growth of the tumor in all of the organs examined. In conclusion, Fab'-SIL[DXR] formulations led to the total inhibition of metastatic growth of human NB in a nude mouse metastatic model. This formulation should receive clinical evaluation as adjuvant therapy of NB.

Animals↗
PubMed2002

Internalizing antibodies are necessary for improved therapeutic efficacy of antibody-targeted liposomal drugs.

Direct experimental proof has been sought for the hypothesis that liposomal drugs targeted against internalizing epitopes (e.g., CD19) will have higher therapeutic efficacies than those targeted against noninternalizing epitopes (e.g., CD20). Anti-CD19-targeted liposomes were rapidly internalized into human B-lymphoma (Namalwa) cells, whereas those targeted with anti-CD20 were not internalized. Similar in vitro binding and cytotoxicity were observed for anti-CD19-targeted and anti-CD20-targeted liposomal formulations of doxorubicin (DXR). Therapeutic experiments were performed in severe combined immunodeficient mice inoculated i.v. with Namalwa cells. Administration of single i.v. doses of DXR-loaded anti-CD19-targeted liposomes resulted in significantly greater survival times than either DXR-loaded anti-CD20-targeted liposomes or nontargeted liposomes. The therapeutic advantage of targeting internalizing versus noninternalizing epitopes has been directly demonstrated.

Animals↗
PubMed2002

Use of the post-insertion method for the formation of ligand-coupled liposomes.

A new technique is described for the formation of ligand-targeted liposomes that can be used with whole antibodies, antibody fragments, peptides or other ligands. The ligands are coupled to polyethylene glycol micelles and then transferred in a simple incubation step from the micelles into the outer monolayer of pre-formed, drug-loaded liposomes. This versatile method allows a combinatorial approach to the design of targeted liposomes that minimises manufacturing complexities, allowing a variety of ligands to be inserted into a variety of pre-formed liposomes containing a variety of drugs. This allows the ligand-targeted therapeutics to be tailored to the needs of individual patients.

Drug Delivery Systems↗
PubMedDate not supplied

Adventures in targeting.

An overview of our experiences in the field of immunoliposomal anticancer drugs is provided with respect to choice of ligand, and choice of model system, in order to provide some guidance as to the rational use of this new technology. Liposomes targeted by either peptide or monoclonal antibodies showed significantly higher binding to their respective target cells in vitro compared to non-targeted liposomes in all model systems examined. This higher binding led to higher cytotoxicities relative to non-targeted liposomes. For the immunoliposomes to deliver their entrapped drug to target cell in vivo, long circulations half-lives are required. We have evaluated the pharmacokinetics of liposomes prepared by several different coupling techniques, and have found significant differences in the clearance of these immunoliposomes from the circulation. Immunoliposomes prepared with whole anti-CD19 IgG coupled by the Mal-PEG-DSPE method demonstrated a short plasma half-life, which may reflect the random orientation of the MAb on the liposome surface. Coupling methods that mask or eliminate the Fc region result in immunoliposomes that have clearance rates more similar to untargeted liposomes. Insertion of peptides or antibodies into pre-formed liposomes through incubation with ligand-coupled PEG micelles resulted in immunoliposomes, termed post-insertion liposomes, that demonstrated comparable in vitro binding, pharmacokinetic profiles and in vivo therapeutic efficacy to liposomes made by conventional coupling methods. The therapeutic efficacy of liposomes, prepared by various coupling methods and targeted by different ligands, was compared in several different animal models of either haematological malignancies, pseudometastatic disease or solid tumours. In our hands, successful in vivo targeting has been obtained when the target is either small or readily accessible from the vasculature, where the liposomes have longer circulating half-lives and/or where a ligand against an internalizing epitope has been chosen. These results should aid in the rational design of applications for immunoliposomal drugs in the future.

Animals↗