Factoring outcomes in ovarian cancer.
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Female↗
Biomedical subjects
M A Bookman
Publications and source records attributed to M A Bookman.
Carboplatin and paclitaxel in ovarian carcinoma: a phase I study of the Gynecologic Oncology Group.
PURPOSE: To develop a tolerable, dose-intense regimen of carboplatin and paclitaxel for the treatment of primary epithelial ovarian carcinoma. PATIENTS AND METHODS: Patients underwent initial surgical assessment and tumor debulking. Patients with stage III/IV disease received six cycles of chemotherapy on a planned 21-day cycle. Carboplatin dose was calculated based on projected area under the curve (AUC) for concentration over time (mg. mL-1.min) and escalated to determine the maximum-tolerated dose (MTD). Paclitaxel dose was also escalated as a 3-, 24-, or 96-hour infusion. Granulocyte colony-stimulating factors (G-CSFs) were required at selected dose levels or could be added based on hematologic toxicity. RESULTS: Thirty-nine patients were enrolled and assessable for toxicity and response. Dose-limiting toxicity (DLT) was hematologic, primarily neutropenia. Less than 2% of all cycles with paclitaxel as a 3- or 24-hour infusion were associated with either grade 4 thrombocytopenia or febrile neutropenia. The carboplatin MTD was AUC 7.5 (equivalent to a median dose of 471 mg/m2). The MTD for paclitaxel was 135 mg/m2 over 24 hours and 175 mg/m2 over 3 hours without initial G-CSF. A 96-hour infusion of paclitaxel at a dose of 120 mg/m2 was associated with excessive single-cycle and cumulative myelosuppression, and was not further evaluated. Measured carboplatin AUC agreed well with the calculated AUC. The overall complete (n = 16) and partial (n = 2) response rate among 24 patients with measurable disease was 75%, with a median progression-free survival time of 15 months. CONCLUSION: Carboplatin could be safely combined with paclitaxel using a dose formula based on projected renal clearance. The recommended outpatient regimen is carboplatin AUC 7.5 and paclitaxel 175 mg/m2 over 3 hours without initial G-CSF. This treatment safely achieved a greater dose-intensity of carboplatin than would have been achieved with conventional dosing based on body-surface area.
Adult↗
Single-chain Fv radioimmunotargeting.
The availability of engineered antibody species has catalyzed new developments in radioimmunotargeting. This chapter summarized recent studies of single-chain Fv (sFv) proteins, which are minimal antibody binding sites engineered as single polypeptide chains. The single-chain Fv can be as small as 26 kDa monomers or may be engineered as larger fusion proteins designed to self-associate into dimeric or multimeric species. They typically exhibit rapid clearance that results in high targeting specificity within a matter of hours. We have compared different modes of administration to allow further manipulation of their biodistribution and targeting properties. Results of the present study comparing intravenous (i.v.) and intraperitoneal (i.p.) administration show comparable long-term retention in circulation, but the i.v. route showed an initially high peak blood level while i.p. injection did not. As with a single sFv dose, repeated bolus injections of sFv attained high target-to-background ratios, whereas continuous sFv infusion reached a steady state level of free sFv in blood and kidney that exceeded that in tumor xenografts. We observed improved localization of radioiodinated sFv in tumor xenografts if the radioiodine label resisted dehalogenation from the protein, which was accomplished, for example, through conjugation of a para-131I-benzoyl group to Iysyl epsilon-amino groups of the protein. Modification of the sFv by genetic incorporation of a cysteinyl peptide (to form sFv') provided a chelation site for radiometals that simplified incorporation of 99mTc with the opportunity for improved diagnostic imaging in cancer and other diseases. Therapeutic applications of sFv radioimmunotargeting could rely on sFv' complexed to 186Re or 188Re. Engineering sFv of sFv' with increased antigen-binding affinity and appropriately manipulating their mode of administration should promote sustained tumor retention conducive to clinically useful therapeutic indices.
Animals↗
Targeting c-erbB-2 expressing tumors using single-chain Fv monomers and dimers.
Single-chain Fv proteins containing a COOH-terminal cysteine (sFv') were constructed by using an antidigoxin 26.10 sFv and an anti-c-erbB-2 741F8 sFv. The fully active sFv' proteins were prepared by expression in Escherichia coli as insoluble inclusion bodies, followed by in vitro refolding using glutathione redox buffers and purification. The COOH-terminal cysteines of the refolded sFv' proteins were protected by a blocking group presumed to be the glutathionyl peptide, which was easily and selectively removed by gentle reduction. Air oxidation of the reduced sFv' monomers resulted in the efficient formation of disulfide-linked sFv' homodimers, designated (sFv')2, which were stable under oxidizing conditions and relatively slow to be disrupted under reducing conditions. The (26-10-1 sFv')-(741F8-1 sFv') heterodimer was prepared and possessed dual-antigen specificity; the active bispecific (sFv')2 dimerized under native conditions, apparently as a manifestation of self-association by the 741F8 sFv' subunit. Biodistribution and imaging studies that were performed on mice bearing human SK-OV-3 tumor xenografts that express the c-erbB-2 as a cell surface antigen were reviewed. Radioiodinated 741F8-2 (sFv')2 homodimer localized to the tumors with high specificity, as evidenced by excellent tumor:normal tissue ratios. Sagittal section autoradiography of whole animals 24 h after administration of antibody species revealed that 741F8 (sFv')2 produced a stronger tumor image than comparable doses of the 741F8 Fab, monomeric sFv', and the 26-10 (sFv')2 control without the high nonspecific background distribution of the 741F8 IgG.
Amino Acid Sequence↗
Optimization of in vivo tumor targeting in SCID mice with divalent forms of 741F8 anti-c-erbB-2 single-chain Fv: effects of dose escalation and repeated i.v. administration.
Single-chain Fv molecules in monovalent (sFv) and divalent [(sFv')2] forms exhibit highly specific tumor targeting in mice as a result of their small size and rapid systemic clearance. As a consequence, there is a rapid reversal of the sFv blood/tumor gradient, resulting in diminished retention of sFv species in tumors. In this report we investigate two distinct strategies, dose escalation and repetitive intravenous (i.v.) dosing, aiming to increase the absolute selective retention of radiolabeled anti-c-erbB-2 125I-741F8 (sFv')2 in c-erbB-2-overexpressing SK-OV-3 tumors in mice with severe combined immunodeficiency (SCID). A dose-escalation strategy was applied to single i.v. injections of 125I-741F8 (sFv')2. Doses from 50 micrograms to 1000 micrograms were administered without a significant decrease in tumor targeting or specificity. High doses resulted in large increases in the absolute retention of 125I-741F8 (sFv')2. For example, raising the administered dose from 50 micrograms to 1000 micrograms increased the tumor retention 24 h after injection from 0.46 microgram/g to 9.5 micrograms/g, and resulted in a net increase of greater than 9 micrograms/g. Over the same dose range, the liver retention rose from 0.06 microgram/g to 1 microgram/g, and resulted in a net increase of less than 1 microgram/g. The retention of 9.5 micrograms/g in tumor 24 h following the 1000-micrograms dose of (sFv')2 was comparable to that seen 24 h after a 50-micrograms dose of 125I-741F8 IgG, indicating that the use of large doses of (sFv')2 may partially offset their rapid clearance. When two doses were administered by i.v. injection 24 h apart, the specificity of delivery to tumor observed after the first dose was maintained following the second injection. Tumor retention of 125I-741F8 (sFv')2 was 0.32 microgram/g at 24 h and 0.22 micrograms/g at 48 h following a single injection of 20 micrograms, while 0.04 microgram/ml and 0.03 microgram/ml were retained in blood at the same assay times. After a second 20-micrograms injection at the 24-h assay time, tumor retention increased to 0.49 micrograms/g, and blood retention was 0.06 microgram/ml, at the 48-h point. These results suggest that multiple high-dose administrations of radiolabeled 741F8 (sFv')2 may lead to the selective tumor localization of therapeutic radiation doses.
Amino Acid Sequence↗
In vitro and in vivo characterization of a human anti-c-erbB-2 single-chain Fv isolated from a filamentous phage antibody library.
BACKGROUND: Antibody-based reagents have failed to live up to their anticipated role as highly specific targeting agents for cancer therapy. Targeting with human single-chain Fv (sFv) molecules may overcome some of the limitations of murine IgG, but are difficult to produce with conventional hybridoma technology. Alternatively, phage display of antibody gene repertoires can be used to produce human sFv. OBJECTIVES: To isolate and characterize human single chain Fvs which bind to c-erbB-2, an oncogene product overexpressed by 30-50% of breast carcinomas and other adenocarcinomas. STUDY DESIGN: A non-immune human single-chain Fv phage antibody library was selected on human c-erbB extracellular domain and sFv characterized with respect to affinity, binding kinetics, and in vivo pharmacokinetics in tumor-bearing scid mice. RESULTS: A human single-chain Fv (C6.5) was isolated which binds specifically to c-erbB-2. C6.5 is entirely human in sequence, expresses at high level as native protein in E. coli, and is easily purified in high yield in two steps. C6.5 binds to immobilized c-erbB-2 extracellular domain with a Kd of 1.6 x 10(-8) M and to c-erbB-2 on SK-OV-3 cells with a Kd of 2.0 x 10(-8) M, an affinity that is similar to sFv produced against the same antigen from hybridomas. Biodistribution studies demonstrate 1.47% injected dose/g tumor 24 h after injection of 125I-C6.5 into scid mice bearing SK-OV-3 tumors. Tumor:normal organ ratios range from 8.9:1 for kidney to 283:1 for muscle. CONCLUSIONS: These results are the first in vivo biodistribution studies using an sFv isolated from a non-immune human repertoire and confirm the specificity of sFv produced in this manner. The use of phage display to produce C6.5 mutants with higher affinity and slower k(off) would permit rigorous evaluation of the role of antibody affinity and binding kinetics in tumor targeting, and could result in the production of a therapeutically useful targeting protein for radioimmunotherapy and other applications.
Amino Acid Sequence↗
Engineering disulfide-linked single-chain Fv dimers [(sFv')2] with improved solution and targeting properties: anti-digoxin 26-10 (sFv')2 and anti-c-erbB-2 741F8 (sFv')2 made by protein folding and bonded through C-terminal cysteinyl peptides.
Single-chain Fv fusions with C-terminal cysteinyl peptides (sFv') have been engineered using model sFv proteins based upon the 26-10 anti-digoxin IgG and 741F8 anti-c-erbB-2 IgG monoclonal antibodies. As part of the 741F8 sFv construction process, the PCR-amplified 741F8 VH gene was modified in an effort to correct possible primer-induced errors. Genetic replacement of the N-terminal beta-strand sequence of 741F8 VH with that from the FR1 of anti-c-erbB-2 520C9 VH resulted in a dramatic improvement of sFv folding yields. Folding in urea-glutathione redox buffers produced active sFv' with a protected C-terminal sulfhydryl, presumably as the mixed disulfide with glutathione. Disulfide-bonded (sFv')2 homodimers were made by disulfide interchange or oxidation after reductive elimination of the blocking group. Both 26-10 (sFv')2 and 741F8 (sFv')2 existed as stable dimers that were well behaved in solution, whereas 741F8 sFv and sFv' exhibited considerable self-association. The 741F8 sFv binds to the extracellular domain (ECD) of the c-erbB-2 oncogene protein, which is often overexpressed in breast cancer and other adenocarcinomas. The recombinant ECD was prepared to facilitate the analysis of 741F8 binding site properties; the cloned ECD gene, modified to encode a C-terminal Ser-Gly-His6 peptide, was transfected into Chinese hamster ovary cells using a vector that also expressed dihydrofolate reductase to facilitate methotrexate amplification. Optimized cell lines expressed ECD-His6 at high levels in a cell bioreactor; after isolation by immobilized metal affinity chromatography, final ECD yields were as high as 47 mg/l. An animal tumor model complemented physicochemical studies of 741F8 species and indicated increased tumor localization of the targeted 741F8 (sFv')2 over other monovalent 741F8 species.
Amino Acid Sequence↗
Biologic therapies for gynecologic cancer.
Recent advances in gynecologic tumor biology are discussed with an emphasis on the development of biologic therapy. Emerging knowledge regarding growth factors, regulatory cytokines, and cellular receptors offers new insight regarding tumor biology and the interaction of tumors with the host peritoneal cavity and immune system. Efforts to target ovarian cancer with antibodies directed against tumor-associated antigens have begun to take advantage of molecular engineering techniques and have also explored an expanded panel of radionuclides with improved conjugation technology. It is hoped that these efforts will translate into successful strategies to improve the long-term survival of patients in conjunction with conventional chemotherapy.
Antibodies, Monoclonal↗
Enhanced tumor specificity of 741F8-1 (sFv')2, an anti-c-erbB-2 single-chain Fv dimer, mediated by stable radioiodine conjugation.
UNLABELLED: The goal of this study was to determine if the stabilization of the radioiodine-protein bond by the N-succinimidyl p-iodobenzoate (PIB) method improved the degree and specificity of tumor localization of 125I-741F8-1 (sFv')2, an anti-c-erbB-2 sFv dimer, in an immunodeficient murine model. METHODS: Gamma camera images were acquired 21 hr after intravenous administration of 131I-741F8-1 (sFv')2 labeled by the p-iodobenzoate or chloramine T methods. The stability of the radioiodine-protein bond also was assessed in plasma samples after intravenous injection of 125I-741F8-1 (sFv')2 labeled by either the chloramine T or p-iodobenzoate methods. RESULTS: By 6 hr postinjection, 97% of the activity associated with the 125I-741F8-1 (sFv')2 labeled by the p-iodobenzoate method was protein bound compared with 61% after labeling with the chloramine-T method. These observations indicate that increasing the stability of the conjugation between the radioiodine and the sFv molecule can significantly increase the degree and specificity of tumor targeting. Significantly greater tumor retention (p < 0.005) and lower blood (p < 0.001), spleen (p < 0.001) and stomach (p < 0.005) retention were observed in biodistribution studies when the p-iodobenzoate conjugate was used. This resulted in superior tumor-to-organ ratios for all tissue samples studied. CONCLUSION: These observations may have clinical relevance for the use of radiolabeled sFv as imaging agents.
Animals↗
Precursor CTL specific for retrovirus-induced T lymphoma are found at high frequency in unprimed syngeneic mice.
The retrovirus-induced RBL5 lymphoma can be rejected by adoptive transfer of noncytolytic CD4+ Th 1 lymphocytes in normal hosts, without a requirement for transfer of specific CD8+ CTL. Therefore, we hypothesized that host precursor CTL (pCTL) might cooperate with transferred CD4+ Th1 cells to mediate tumor rejection. To evaluate this hypothesis, lymphocytes from non-immunized mice were analyzed for cytolytic activity after short-term bulk lymphocyte tumor culture (BLTC) with rIL-2 (5U/ml). BLTC induced the differentiation of anti-RBL5 CTL distinct from non-MHC-restricted LAK. These effectors were CD8+, TCR alpha/beta+, and utilized the CD3-TCR complex for MHC class I-restricted lysis. The majority of pCTL were found within the CD44/PgP-1hi population of memory/activated lymphocytes. However, there was no serologic evidence for prior exposure to RBL5-related tumor or viral Ags. CTL activity was susceptible to partial blockade with mAbs directed against CD8 and MHC class I, suggesting a relatively low-affinity Ag-TCR interaction. These data are most consistent with the recruitment of a population of Ag-specific, but cross-reactive, pCTL during BLTC.
Animals↗
Highly specific in vivo tumor targeting by monovalent and divalent forms of 741F8 anti-c-erbB-2 single-chain Fv.
The in vivo properties of monovalent and divalent single-chain Fv (sFv)-based molecules with the specificity of the anti-c-erbB-2 monoclonal antibody 741F8 were examined in scid mice bearing SK-OV-3 tumor xenografts. 741F8 sFv monomers exhibited rapid, biphasic clearance from blood, while a slightly slower clearance was observed with the divalent 741F8 (sFv')2 comprising a pair of 741F8 sFv' with a C-terminal Gly4Cys joined by a disulfide bond. Following i.v. injection, the 741F8 sFv monomer was selectively retained in c-erbB-2-overexpressing SK-OV-3 tumor, with excellent tumor:normal organ ratios uniformly exceeding 10:1 by 24 h. The specificity of this effect was demonstrated by the lack of retention of the anti-digoxin 26-10 sFv monomer, as evaluated by biodistribution studies, gamma camera imaging, and cryomacroautoradiography studies. The specificity index (741F8 sFv retention/26-10 sFv retention) of 741F8 monomer binding, measured by the percentage of injected dose per g of tissue, was 13.2:1 for tumor, and 0.8 to 2.1 for all tested normal organs, with specificity indices for tumor:organ ratios ranging from 7.0 (kidneys) to 16.7 (intestines). Comparing divalent 741F8 (sFv')2 with the 26-10 (sFv')2, similar patterns emerged, with specificity indices for retention in tumor of 16.9 for the Gly4Cys-linked (sFv')2. These data demonstrate that, following their i.v. administration, both monovalent and divalent forms of 741F8 sFv are specifically retained by SK-OV-3 tumors. This antigen-specific binding, in conjunction with the 26-10 sFv controls, precludes the possibility that passive diffusion and pooling in the tumor interstitium contributes significantly to long-term tumor localization. 741F8 (sFv')2 species with peptide spacers exhibited divalent binding and increased retention in tumors as compared with 741F8 sFv monomers. Since the blood retention of the (sFv')2 is slightly more prolonged than that of the monomer, it was necessary to demonstrate that the increased tumor localization of the peptide-linked (sFv')2 was due to its divalent nature. The significantly greater localization of the divalent bismalimidohexane-linked 741F8 (sFv')2 as compared with a monovalent 741F8 Fab fragment of approximately the same size suggests that the increased avidity of the (sFv')2 is a factor in its improved tumor retention. This is the first report of successful specific in vivo targeting of tumors by divalent forms of sFv molecules. The improved retention of specific divalent (sFv')2 by tumors may have important consequences for targeted diagnostic or therapeutic strategies.
Animals↗
Biologic therapy in the management of refractory ovarian cancer.
The success of platinum-based chemotherapy in the initial management of advanced-stage ovarian cancer has been challenged by the emergence of drug-resistant tumors in the majority of patients. Even taxol, which can achieve clinical responses in one-third of patients with platinum-resistant tumors, may fail to substantially alter long-term survival for many patients with refractory disease. Thus, there continues to be a need for alternative therapeutic strategies. Specific roles for primary or adjunctive biologic therapy in the management of refractory ovarian cancer have not yet been defined. For example, a variety of conjugated monoclonal antibodies have been evaluated for over 10 years, but have not yet been shown to be effective with acceptable levels of host toxicity. The closest candidate for standardized biologic therapy is intraperitoneal interferon for treatment of microscopic residual disease. Adjunctive hematopoietic colony stimulating factors are widely used with taxol to achieve greater dose intensity and cumulative drug delivery, although they have not yet been shown to improve response or survival. Appreciation of the complex pathways regulated by growth factors and cytokines will provide a more challenging framework for continued development of biological therapeutics in the future.
Animals↗
Future directions for paclitaxel (TAXOL) in the treatment of ovarian cancer.
Ovarian cancer is the leading cause of death from gynecologic cancers in women in the United States. Although response rates to primary platinum-based therapy are high, relapse is common. The overall survival of patients with advanced-stage disease has not changed dramatically over the last 20 years, even with the advent of effective combination chemotherapy. Paclitaxel (TAXOL) is a new chemotherapeutic agent that shows promise for the treatment of patients with advanced disease as well as those with recurrent cisplatin-refractory disease. Overall response rates have been encouraging, although there are few pathological complete remissions. In contrast to other treatments, many patients achieve prolonged stable disease over multiple cycles of therapy. However, the optimal use of paclitaxel has not yet been determined. Current studies aim to evaluate dose intensity, administration schedule, multidrug regimens, sequence of drug administration, and combinations with radiation therapy. Future studies may address adjuvant therapy of early-stage disease. Results of these trials will clarify the role of paclitaxel in the primary treatment of ovarian cancer.
Adolescent↗
High-dose carboplatin and recombinant granulocyte-macrophage colony-stimulating factor in advanced-stage recurrent ovarian cancer.
PURPOSE: We investigated whether carboplatin myelosuppression could be favorably modulated by the administration of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in patients with advanced-stage ovarian cancer. PATIENTS AND METHODS: Thirty-four patients with advanced-stage recurrent ovarian cancer were treated with high-dose carboplatin (800 mg/m2 per 35-day cycle) and rGM-CSF. rGM-CSF was administered as a daily subcutaneous injection starting 72 hours after the carboplatin dose and continuing until 7 days beyond the WBC nadir. rGM-CSF was administered in a phase I fashion. Seven patients were treated at an rGM-CSF dose of 3 micrograms/kg, 11 at 5 micrograms/kg, 10 at 10 micrograms/kg, and six at 20 micrograms/kg. RESULTS: rGM-CSF-related toxicities that were not dose-related included nonneutropenic fever, rib pain, acute hypersensitivity reaction, and pericarditis. At the rGM-CSF dose of 20 micrograms/kg, debilitating malaise was seen in four of six patients and this was the dose-limiting toxicity. Patient tolerance of the 3-micrograms/kg and 5-micrograms/kg doses was good, but tolerance was limited for the 10-micrograms/kg dose. Febrile neutropenia was seen in four of seven patients at 3 micrograms/kg, two of 11 at 5 micrograms/kg, two of 10 at 10 micrograms/kg, and one of six at 20 micrograms/kg. Cumulative carboplatin myelotoxicity was blunted only in respect to WBC count, and not for platelets or RBCs. Gastrointestinal bleeding was seen in seven patients. The administered dose-intensity of carboplatin averaged 134 mg/m2/wk for the cohort, or 670 mg/m2 per 35-day cycle. There were two clinical complete responses and eleven partial responses, for a response rate of 38%. CONCLUSION: rGM-CSF appears to be effective and tolerable at 5 micrograms/kg/d administered subcutaneously, if given with carboplatin doses up to approximately 600 mg/m2 over 35 days. The use of rGM-CSF with high-dose carboplatin is associated with a substantial response rate in poor-prognosis ovarian cancer patients.
Adult↗
Biologic and immunologic therapy of ovarian cancer.
Conventional cytotoxic chemotherapy fails to cure the majority of patients with advanced-stage ovarian cancer, in spite of encouraging initial antitumor responses. With the emergence of drug resistance in refractory tumors, new biologic and immunologic treatment strategies are needed. Small-volume residual peritoneal disease remains an attractive target for therapeutic trials; however, even in this optimal circumstance, few regimens have yet achieved a high frequency of pathologically confirmed complete remissions. Considerable progress has been made in understanding the impact of growth factors and their receptors on tumor growth regulation and modulation of response to chemotherapy. Better characterization of the antigens recognized by monoclonal antibodies, as well as sequencing of the antibodies themselves, has permitted the rational design of therapeutic reagents that take full advantage of molecular biology techniques for production and conjugation. Important limitations of preclinical models for prediction of host toxicity are recognized, and the reasons for treatment failure in situ, as well as strategies to prevent serious dose-limiting toxicities, are being explored. Further developments in cytokine biology, adoptive cellular therapy, monoclonal antibody conjugation, and molecular biology will continue to provide a growing array of reagents for critical evaluation.
Adjuvants, Immunologic↗
Biologic therapy and immunotherapy for ovarian cancer.
Ovarian cancer remains an attractive model for evaluation of biologic and immunologic therapies due to the availability of multiple reagents, the development of preclinical murine models, and the intraperitoneal pattern of clinical disease. Recent studies have focused on conjugated monoclonal antibodies, including radioconjugates, immunotoxins, and bispecific antibodies. Other preclinical and clinical studies have been conducted with recombinant cytokines and adoptive cellular immunotherapy for small-volume residual disease. Dose-limiting clinical toxicities have emerged with many of these approaches in the absence of frequent antitumor responses, and new strategies will be required to develop effective therapies in the future.
Animals↗
Clinical evaluation of intraperitoneal Pseudomonas exotoxin immunoconjugate OVB3-PE in patients with ovarian cancer.
OVB3-PE is an immunotoxin composed of a murine monoclonal antibody reactive with human ovarian cancer and conjugated to Pseudomonas exotoxin (PE). Twenty-three patients with refractory ovarian cancer were treated intraperitoneally (IP) with escalating doses of OVB3-PE to study toxicity, pharmacokinetics, antiimmunotoxin antibody formation, and antitumor response. Dose-limiting CNS toxicity occurred after repeated doses at 5 and 10 micrograms/kg. Other non-dose-limiting toxicities included transient elevation of liver enzymes, fever, and gastrointestinal toxicity. Pharmacokinetics of IP and serum OVB3-PE were determined in 16 patients. Peak peritoneal fluid levels exceeded the in vitro median effective dose at all doses tested. At doses of 1 to 2 micrograms/kg, the immunotoxin concentration in the peritoneal fluid remained constant for up to 8 hours and dropped to negligible levels after 12 hours. At the 5 and 10 micrograms/kg doses, levels remained high for up to 24 hours (greater than 100 ng/mL) and then gradually decreased and became undetectable (less than 4 ng/mL) after 72 hours. Serum levels of OVB3-PE were also analyzed in 16 patients. At doses of 1 micrograms/kg and 2 micrograms/kg, serum levels were not detectable (less than 5 ng/mL). However, after doses of 5 or 10 micrograms/kg, peak serum level occurred at 24 hours after each dose and dropped to negligible levels by 72 hours. Sera from 12 patients were analyzed for anti-PE antibodies and antibodies to mouse immunoglobulin (HAMA). All patients developed antibodies against PE within 14 days of therapy. Domain II of PE appeared to be the most immunogenic portion of the PE molecule. HAMA was detected on day 14 of therapy in nine patients, on day 21 in two, and on day 28 in one patient. No clinical antitumor responses were observed. We conclude that IP OVB3-PE at dose levels of 5 micrograms/kg (x 3) and 10 micrograms/kg (x 2) is accompanied by dose-limiting toxic encephalopathy. Neurologic toxicity is likely to be due to crossreactivity of OVB3 to normal human brain tissue, which was not appreciated during preclinical screening.
ADP Ribose Transferases↗
The immunobiology and immunotherapy of ovarian cancer.
Small volume residual peritoneal disease in patients undergoing therapy for ovarian carcinoma remains an attractive, but elusive, target for immunobiological therapy. Hypothetical advantages and disadvantages of regional peritoneal therapy are being better defined through increased clinical experience and more sophisticated animal models. Developments in cytokine biology, adoptive cellular therapy, monoclonal antibody conjugation, and molecular biology continue to provide an exciting, and nearly overwhelming, array of reagents for clinical evaluation. Ongoing and anticipated investigational trials should provide intriguing data in years to follow.
Antibodies, Monoclonal↗