A mouse/human chimeric anti-(ganglioside GD3) antibody with enhanced antitumor activities

Application of the Antibody-Inducing Activity of Glycosphingolipids to Human Diseases

Glycosphingolipids (GSLs) are composed of a mono-, di-, or oligosaccharide and a ceramide and function as constituents of cell membranes. Various molecular species of GSLs have been identified in mammalian cells due to differences in the structures of oligosaccharides. The oligosaccharide structure can vary depending on cell lineage, differentiation stage, and pathology; this property can be used as a cell identification marker. Furthermore, GSLs are involved in various aspects of the immune response, such as cytokine production, immune signaling, migration of immune cells, and antibody production. GSLs containing certain structures exhibit strong immunogenicity in immunized animals and promote the production of anti-GSL antibodies. By exploiting this property, it is possible to generate antibodies that recognize the fine oligosaccharide structure of specific GSLs or glycoproteins. In our study using artificially synthesized GSLs (artGSLs), we found that several structural features are correlated with the antibody-inducing activity of GSLs. Based on these findings, we designed artGSLs that efficiently induce the production of antibodies accompanied by class switching and developed several antibodies that recognize not only certain glycan structures of GSLs but also those of glycoproteins. This review comprehensively introduces the immune activities of GSLs and their application as pharmaceuticals.

Safety and efficacy of the antiganglioside GD3 antibody ecromeximab (KW2871) combined with high-dose interferon-α2b in patients with metastatic melanoma

This study evaluated the safety and clinical benefit of ecromeximab (KW2871) combined with high-dose interferon-α2b (HDI) in patients with metastatic melanoma. We also carried out pharmacokinetic and immune monitoring studies of this combination. This was an open-label, phase 1/2 study of ecromeximab plus HDI in patients with measurable metastatic melanoma. Eligible patients received ecromeximab-HDI combination therapy: ecromeximab administered intravenously once every 2 weeks and HDI at a dose of 20 million units (MU)/m administered intravenously for 5 consecutive days per week for the first 4 weeks (induction phase) and then at 10 MU/m subcutaneously thrice weekly through week 14 (maintenance phase). Patients were treated with combination therapy until disease progression or limiting toxicity. Three dose-escalation cohorts (5, 10, and 20 mg/m) of ecromeximab were planned. Thirty-six evaluable patients were enrolled including six in each of cohorts 1 and 2, and 24 in cohort 3. Median progression-free survival was 2.53 months [95% confidence interval (CI):1.93-3.83] and it was 1.93 months (95% CI: 1.00-3.80) in cohort 3. The median overall survival was 10.28 months (95% CI: 6.93-16.77) and 7.78 months (95% CI: 6.03-13.97) in cohort 3. There was no significant difference in progression-free survival or overall survival by BRAF mutation status. The response rate was 5.6% (95% CI: 0.68-18.7), with two patients showing an objective response (one complete response and one partial response), and the clinical benefit rate was 78% (95% CI: 61-90). Stable disease as best response was observed in 26 (72%) patients including five in each of cohorts 1 and 2, and 16 in cohort 3. Treatment-emergent adverse events considered related to ecromeximab treatment occurred in four (66.7%) patients in cohort 1, five (83.3%) patients in cohort 2, and seven (29.2%) patients in cohort 3. Among TEAEs with a maximum severity of grade 3 or 4, those that occurred only in cohort 3 were related to pain, electrolyte imbalance, blood cell decreases, and allergic reaction. Safety and efficacies considered related to ecromeximab occurred in cohort 3 and included grade 3 hypersensitivity [one (4.2%)] and grade 2 hypotension [one (4.2%)]. Regimen-limiting toxicities occurred in two (8.3%) patients in cohort 3: hypersensitivity (with hypertension, supraventricular tachycardia, bronchospasm, chills, and dyspnea) and hypotension. One patient out of 31 examined showed a low-level transient positivity for human antichimeric antibodies against ecromeximab. Pharmacokinetic measurements by enzyme-linked immunosorbent assay determined that administration of HDI does not influence serum levels of ecromeximab at 5, 10, and 20 mg/m dose levels. Ecromeximab in combination with HDI was generally well tolerated in patients with metastatic melanoma and has shown low immunogenicity. However, the clinical activity was limited, suggesting that future development of this combination should be deprioritized and that other combinations, such as with immune checkpoint inhibitors, should be considered.

Generation and Improvement of Effector Function of a Novel Broadly Reactive and Protective Monoclonal Antibody against Pneumococcal Surface Protein A of Streptococcus pneumoniae

A proof-of-concept study evaluating the potential of Streptococcus pneumoniae Pneumococcal Surface Protein A (PspA) as a passive immunization target was conducted. We describe the generation and isolation of several broadly reactive mouse anti-PspA monoclonal antibodies (mAbs). MAb 140H1 displayed (i) 98% strain coverage, (ii) activity in complement deposition and opsonophagocytic killing (OPK) assays, which are thought to predict the in vivo efficacy of anti-pneumococcal mAbs, (iii) efficacy in mouse sepsis models both alone and in combination with standard-of-care antibiotics, and (iv) therapeutic activity in a mouse pneumonia model. Moreover, we demonstrate that antibody engineering can significantly enhance anti-PspA mAb effector function. We believe that PspA has promising potential as a target for the therapy of invasive pneumococcal disease by mAbs, which could be used alone or in conjunction with standard-of-care antibiotics.

Anti-GD3 monoclonal antibody effects on lymphocytes and antibody-dependent cellular cytotoxicity

PURPOSE

Antibodies targeting GD3 gangliosides highly expressed on melanomas mediate immune effector functions in vitro and inhibit animal model melanoma tumor growth in vivo. Because GD3 is expressed also on a subpopulation of human lymphocytes, we characterized the in vitro immune effects of murine R24 and a chimeric anti-GD3 antibody (KW-2871).

DESIGN

Anti-GD3 complement-mediated (CMC) and antibody-dependent cellular cytotoxicity (ADCC) were tested against cell line Mel-624. Antibody-mediated lymphocyte expression of interleukin (IL)-2, IL-4, IL-10, and interferon-gamma (IFN-gamma) was quantified. The effect of antibody and antibody-treated lymphocyte supernates on effector cell ADCC and Fc receptor expression were evaluated.

RESULTS

R24 and KW-2871 antibodies mediated CMC and ADCC to the Mel-624 cell line. R24 induced potent lymphocyte proliferation and enhanced lymphocyte RNA expression of IL-4 (2-4 logs), IL-10, and IFN-gamma (> 10-fold). KW-2871 induced no lymphocyte proliferation and had minimal effects on lymphokine expression (< 5-fold). Preincubation of effector cells with either antibody inhibited ADCC and reduced monocyte expression of FcgammaRI and II. Supernates of effector cells preincubated with either antibody were able to inhibit ADCC.

CONCLUSIONS

R24 and KW-2871 antibody differ in their lymphocyte proliferation and lymphokine release activity but have similar inhibition of lymphocyte ADCC and FcgammaR expression in vitro.

A Phase I Study of an Anti-GD3 Monoclonal Antibody, KW-2871, in Patients with Metastatic Melanoma

PURPOSE

KW-2871 (IgG1 kappa chimeric antibody) targets GD3, which is upregulated in melanomas. We conducted a phase I trial of KW-2871 in patients with metastatic melanoma.

METHODS

Seventeen (17) patients were enrolled and received an initial test dose (10 mg/m2) intravenously. Two 2 weeks later, patients were stratified into 4 cohorts to receive 4 doses of KW-2871 (infused over 1 hour) at 2-week intervals (20, 40, 60, and 80 mg/m2). No premedications were administered for the test or first therapeutic doses.

RESULTS

Dose-limiting toxicities were Grade 3 laryngospasm and chest tightness with the initial therapeutic infusion at doses of 80 and 60 mg/m2. The maximum tolerated dose (MTD) was established at 40 mg/m2 of KW2871. The most common side-effect was urticaria (Grades 1-3) in 16 of 16 patients during an initial therapeutic infusion without premedication. The mean terminal half-life, clearance, and area under the concentration-time curve (AUC(0-t)) at a dose of 40 mg/m2 for course 1 were 146 +/- 31 hours, 28 +/- 6 ml/hour, and 1922 +/- 491 mcg*hour/mL, respectively. Anti-human chimeric antibody was not detected. Two (2) patients in the 40 mg/m2 cohort had stable disease.

CONCLUSIONS

An MTD of 40 mg/m2 without premedication was established for KW-2871, with urticaria being the most common side-effect and dose-limiting anaphylactoid infusion reactions.

Common side effects of anti-EGFR therapy: acneform rash

OBJECTIVES

To review the general toxicity profile of EGFR-targeted therapies and the management of the most common side effect, skin toxicity.

DATA SOURCES

Research articles.

CONCLUSION

The most common side effect of anti-EGFR therapy is skin toxicity, which is generally mild to moderate, but may be severe in up to 18% of patients. Appearance of more severe rash has been correlated with better treatment outcomes. Skin toxicity is generally manageable with standard topical or systemic antibiotics and anti-inflammatory agents. Rash does not warrant treatment discontinuation; however, when using TKIs, the combination of rash and severe diarrhea may require treatment cessation.

IMPLICATIONS FOR NURSING PRACTICE

Patients and nurses need to be well informed about the expected side effects of anti-EGFR therapy and appropriate management techniques. Patient education prior to beginning therapy and proactive intervention at the first signs of skin toxicity are key to successful management.

EGFR as a Target: Rationale for Therapy

OBJECTIVES

To review the biology of the EGFR, its structure, and the associated signal transduction pathways. To provide an overview of the role of EGFR in normal physiology and the pathophysiology of malignancy. Current anti-EGFR treatments are also discussed.

DATA SOURCES

Research articles.

CONCLUSION

EGFR is a valid target in the treatment of solid tumors. EGFR abnormalities and dysfunction are involved in various aspects of carcinogenesis and tumor progression, and EGFR is overexpressed in several tumor types. The development of anti-EGFR therapies represents an important advance in cancer therapy.

IMPLICATIONS FOR NURSING PRACTICE

Anti-EGFR therapy is currently available in the clinical setting. Nurses involved in the care of patients with cancer can benefit from an increased understanding of the normal and abnormal function of EGFR in the body and the mechanisms by which anti-EGFR therapies act.

Enhancing oxaliplatin-based regimens in colorectal cancer by inhibiting the epidermal growth factor receptor pathway

In the past several years, significant advances in the treatment of colorectal cancer (CRC) have been made. With the introduction of irinotecan and oxaliplatin combined with infusional 5-fluororuracil, survival times for patients with metastatic CRC have nearly doubled. With the incorporation of biologic agents that target the vascular endothelial growth factor and epidermal growth factor (EGF) pathways, additional improvements in response, progression-free survival, and overall survival have been seen in patients with advanced, metastatic disease. This article reviews the impact of EGF receptor inhibitors on improving survival in CRC when combined with oxaliplatin-containing regimens.

Cetuximab as a single agent or in combination with chemotherapy in lung cancer

Epidermal growth factor receptor (EGFR) has become an important target in the treatment of cancer. Multiple epithelial cancers have been found to overexpress the receptor including head and neck, breast, colon, lung, prostate, kidney, ovary, brain, pancreas, and bladder. Strategies to block EGFR include development of monoclonal antibodies to EGFR, tyrosine kinase inhibitors, ligand-linked toxins, and antisense approaches. The inhibition of EGFR may lead to suppression of tumor proliferation and improve overall clinical outcome, as overexpression of the receptor has been associated with a poorer prognosis in patients with cancer. This article will focus on the monoclonal antibody cetuximab and its applications in the treatment of non-small-cell lung cancer.

Clinical issues in the administration of an anti-epidermal growth factor receptor monoclonal antibody, IMC-C225

OBJECTIVES

To review the clinical safety experience of the monoclonal antibody IMC-C225, focusing on two clinically important adverse events: acne-like rash and allergic reactions. In addition, practical administration issues are discussed.

DATA SOURCES

Research articles.

CONCLUSIONS

IMC-C225 administration is well tolerated and adverse events are mild and manageable. IMC-C225 can be safely and conveniently administered once weekly in outpatient settings.

IMPLICATIONS FOR NURSING PRACTICE

Because nurses will be involved with administration of IMC-C225 in the clinical setting, they must understand and be prepared to manage the acute and long-term adverse events associated with this agent.

The role of the epidermal growth factor receptor in the treatment of colorectal carcinoma

OBJECTIVES

To review the implications of epidermal growth factor receptor (EGFR) blockade and become familiar with the clinical experience in colorectal carcinoma to date.

DATA SOURCES

Research articles and textbooks.

CONCLUSIONS

Blockade of the EGFR results in clinically significant antitumor activities in a variety of tumors, including colorectal carcinoma. There are a variety of mechanisms by which to block the EGFR pathway. Those that have undergone extensive clinical testing include tyrosine kinase inhibitors and anti-EGFR monoclonal antibodies. In addition, biological agents have shown promise when combined with traditional cytotoxic approaches.

IMPLICATIONS FOR NURSING PRACTICE

With many targeted biological agents undergoing evaluation, it is important that nurses become familiar with early clinical experience to understand their role in the treatment of cancer.

Monoclonal antibodies to target epidermal growth factor receptor-positive tumors: a new paradigm for cancer therapy

BACKGROUND

Traditional cytotoxic approaches to tumor management are associated with efficacy and toxicity limitations. Blockade of the epidermal growth factor receptor (EGFR) and its ligands is a novel approach to the treatment of human tumors that offers a noncytotoxic alternative to cancer treatment.

METHODS

An English-language literature search was conducted to identify studies assessing the in vitro and in vivo effects of EGFR blockade with an emphasis on approaches that use monoclonal antibody therapy.

RESULTS

The EGF pathway regulates normal cellular processes and appears to be correlated with the development of malignancy. Approximately 30% of human tumors express EGFR, which has been reported to be correlated with poor prognosis and diminished disease-free and overall survival in selected tumor types. A number of anti-EGFR monoclonal antibodies have been developed, which currently are undergoing clinical trials in humans. Effective anti-EGFR monoclonal antibodies compete with endogenous ligands, primarily EGF and transforming growth factor-alpha, for receptor ligand-binding sites. Binding to EGFR blocks critical signaling pathways and interferes with the growth of tumors expressing EGFR. Anti-EGFR monoclonal antibodies that currently are under study include IMC-C225, EMD 55900, ICR 62, and ABX-EGF.

CONCLUSIONS

These antibodies have demonstrated promising results and appear to have been well tolerated. EGFR-targeted therapy addresses important, unmet needs in the treatment of human tumors, particularly EGFR-positive epithelial tumors including common malignancies of the head and neck, lung, and colon.

Epidermal growth factor receptor biology (IMC-C225)

Treatment of solid tumors despite improved techniques in detection, surgery, radiation therapy, and chemotherapy remains difficult. Therefore, strategies to improve efficacy in accord with safety are needed. Many epithelial cancers have been found to overexpress the receptor to epidermal growth factor (EGFR), including head and neck, breast, colon, lung, prostate, kidney, ovary, brain, pancreas, and bladder. Because overexpression of EGFR has been associated with an overall poor prognosis in patients with cancer, a number of strategies to block or downregulate EGFR have been developed to inhibit tumor proliferation and improve overall clinical outcome. These include monoclonal antibodies to the EGFR, tyrosine kinase inhibitors, ligand-linked toxins, and antisense approaches. Antibodies such as IMC-C225 specifically target EGF receptors, whereas tyrosine kinase inhibition by many small molecules is less specific. Ultimately, IMC-C225 may prove to become a valuable contributor in the treatment of cancer. This report will focus on IMC-C225, a novel monoclonal antibody that targets the EGFR.

Specific targeting, biodistribution, and lack of immunogenicity of chimeric anti-GD3 monoclonal antibody KM871 in patients with metastatic melanoma: results of a phase I trial

PURPOSE

KM871 is a chimeric monoclonal antibody against the ganglioside antigen GD3, which is highly expressed on melanoma cells. We conducted an open-label, dose escalation phase I trial of KM871 in patients with metastatic melanoma.

PATIENTS AND METHODS

Seventeen patients were entered onto one of five dose levels (1, 5, 10, 20, and 40 mg/m2). Patients received three infusions of KM871 at 2-week intervals, with the first infusion of KM871 trace-labeled with indium-111 (111In) to enable assessment of biodistribution in vivo. Biopsies of metastatic melanoma sites were performed on days 7 to 10.

RESULTS

Fifteen of 17 patients completed a cycle of three infusions of KM871. No dose-limiting toxicity was observed during the trial; the maximum-tolerated dose was therefore not reached. Three patients (at the 1-, 5-, and 40-mg/m2 dose levels) developed pain and/or erythema at tumor sites consistent with an inflammatory response. No normal tissue uptake of 111In-KM871 was observed, and tumor uptake of 111In-KM871 was observed in all lesions greater than 1.5 cm (tumor biopsy 111KM871 uptake results: range, 0.001% to 0.026% injected dose/g). The ratio of maximum tumor to normal tissue was 15:1. Pharmacokinetic analysis revealed a 111In-KM871 terminal half-life of 7.68 +/- 2.94 days. One patient had a clinical partial response that lasted 11 months. There was no serologic evidence of human antichimeric antibody in any patient, including one patient who received 16 infusions over a 12-month period.

CONCLUSION

This study is the first to demonstrate the biodistribution and specific targeting of an anti-GD3 antibody to metastatic melanoma in patients. The long half-life and lack of immunogenicity of KM871 makes this antibody an attractive potential therapy for patients with metastatic melanoma.

IMC-C225, an anti-epidermal growth factor receptor monoclonal antibody, for treatment of head and neck cancer

Squamous cell carcinoma (SCC) of the head and neck (H&N) remains a clinical challenge due to its high rate of locoregional disease recurrence. The importance of the epidermal growth factor receptor (EGFR) in the development and progression of many solid tumours (including SCC of the H&N) is well understood; increased expression is associated with enhanced tumour invasion, resistance to chemotherapy and decreased patient survival. Several approaches have been developed to achieve EGFR blockade as an anticancer treatment strategy, including an anti-EGFR monoclonal antibody (mAb), IMC-C225, which competitively binds to the extracellular receptor site to prevent binding by natural EGFR ligands (EGF and TGF-alpha). Preclinical studies evaluating this chimeric mAb in human cancer cell lines in vitro and human tumour xenografts in vivo have demonstrated its potent antitumour activity. The clinical efficacy of IMC-C225 appears to involve multiple anticancer mechanisms, including inhibition of cell cycle progression, induction of apoptosis, anti-angiogenesis, inhibition of metastasis and its ability to enhance the response to chemotherapy and radiation therapy. Phase I studies of IMC-C225 combined with chemotherapy or radiation for SCC of the H&N demonstrate excellent response rates in patients with recurrent or refractory disease. Phase II and III trials examining the efficacy and safety of these combinations are currently underway. To date, IMC-C225 has been well-tolerated, with skin rashes and allergic reactions being the most clinically important adverse events reported. IMC-C225 displays dose-dependent elimination characteristics and a half-life of approximately 7 days. Current recommendations for dosing include a 400 mg/m2 loading dose, followed by weekly infusions of 250 mg/m2.

Dissection and optimization of immune effector functions of humanized anti-ganglioside GM2 monoclonal antibody

A mouse/human chimeric monoclonal antibody (MAb) KM966, specific for the cell-surface tumor antigen ganglioside GM2, was humanized by the complementarity determining regions (CDRs) grafting method. Not only the amino acid residues in the CDRs but also several in the framework regions (FRs) were changed from the human to the murine residues. A humanized variant, huKM796H/Lm-28, containing eight and five amino acid alterations in variable light (VL) and variable heavy (VH) FRs, respectively, showed a 9-fold reduction in complement-dependent cytotoxicity (CDC) compared to the chimeric KM966, despite tight antigen binding and potent antibody-dependent cellular cytotoxicity (ADCC). Several additional variants were subsequently constructed to improve the CDC of the antibody. One of the variants, designated KM8969, which differs by three amino acids, exhibited a CDC within 3-fold of the chimeric KM966. In addition, humanized KM8969 bound GM2 antigen 1.25-fold more tightly than the chimeric KM966 and showed 5-fold higher ADCC than the chimeric KM966. These results clearly show that the humanized KM8969, having the optimized immune effector functions and theoretically minimal immunogenicity, is an ideal candidate to test the effectiveness of anti-GM2 MAb in human cancer therapy. Taken together, the results obtained here indicate that the ADCC and CDC of an antibody can be dissected independently via engineering of the antibody variable region.

Synthesis and HPLC analysis of enzymatically cleavable linker consisting of poly(ethylene glycol) and dipeptide for the development of immunoconjugate

A model compound of anti-tumor agent, segment B of duocarmycin derivative DU-86, was conjugated to tumor-specific antibody via a cleavable linker consisting of poly(ethylene glycol) (PEG) and dipeptide, L-alanyl-L-valine (Ala-Val), to confirm the feasibility of the linker for application to immunoconjugate. The release of segment B from the linker was evaluated by HPLC analysis. When segment B was derivatized to have an amino residue and then linked to PEG through a dipeptide, segment B was cleaved at the peptide bond by a particular enzyme, thermolysin (EC 3.4.24.4), but not by plasmin (EC 3.4.2 1.7.), indicating that certain protease specifically expressed at the tumor site would be capable of peptide-specific digestion and release of anti-tumor agent since a thermolysin-like enzyme has been reported to be expressed at many tumor cells. Furthermore, the results showing that cell extract from G361 human melanoma had an ability to digest the linker peptide while the linker was stable in normal human serum suggested the tumor-specific activation of the conjugated agent. Segment B was conjugated via the linker to murine monoclonal antibody KM641 reactive to GD3 ganglioside to form immunoconjugate and the quantitative release of segment B under the treatment with the enzyme was also confirmed. These results indicate the possibility of double targeting based on both the recognition ability of tumor specific antibody and tumor specific activation of the anti-tumor agents to enhance tumor treatment efficacy and to decrease unwanted side effects.

Antibody-dependent cytotoxicity mediated by chimeric monoclonal antibody Nd2 and experimental immunotherapy for pancreatic cancer

In a previous study, mouse monoclonal antibody (MoAb) Nd2 (m-Nd2, mouse IgG1) labeled with (131)I exhibited efficacy in in vivo radioimmunotherapy against pancreatic cancer. In this study we prepared mouse / human chimeric antibody Nd2 (c-Nd2, human IgG1) for clinical use and examined whether c-Nd2 induced antibody-dependent cell-mediated cytotoxicity (ADCC). Cytotoxicity to pancreatic cancer (PC) cell lines, including Nd2 antigen-positive (SW1990, RWP-1, Capan-1) and Nd2 antigen-negative (Panc-1, MiaPaca-2, Capan-2) lines, was evaluated by mixed human leukocyte and tumor cell culture (MLTC) at an effector cell to target cell (E / T) ratio of 50 with or without Nd2. Cytotoxicities to SW1990 with no antibody, m-Nd2 and c-Nd2 (1 microg / ml) were 26.7%, 38.0% and 55%, respectively; to RWP-1, 28%, 41% and 70%; to Capan-1, 26%, 30% and 52%; to Panc-1, 24%, 28% and 30%; to MiaPaca-2, 18%, 20% and 27% and to Capan-2, 29. 7%, 35.0% and 40.6%. Cytotoxic capacity during MLTC with c-Nd2 was significantly higher than during MLTC with m-Nd2 or with no antibody. These findings indicated that cytotoxicity to Nd2-positive PC cells during MLTC is induced by ADCC. Intraperitoneal injection of c-Nd2 inhibited the tumor growth of SW1990 xenografted subcutaneously in nude mice and prolonged the survival of nude mice in which SW1990 tumor was transplanted orthotopically at the tail of the pancreas. These findings suggested that, because of its ability to induce ADCC, c-Nd2 may be clinically useful for the immunotherapeutic treatment of pancreatic cancer.

Monoclonal antibodies in the treatment of human B-cell malignancies

Monoclonal antibody technology emerged in the 1970's and was greeted by a wave of optimism. Many believed this new form of therapy would be effective in the treatment of human cancers. Early clinical trials in B-cell lymphomas demonstrated both the potential and limitations of unlabeled murine monoclonal antibody therapy, and taught us valuable lessons regarding the importance of the antibody structure, and nature of the targeted antigen. Since that time modifications in antibody structure and careful selection of target antigen have improved the clinical efficacy of these agents. Clinical trials using humanized antibodies have demonstrated that human/mouse chimeric antibodies and humanized antibodies have enhanced anti-tumor activity, decreased immunogenicity, and a very favorable toxicity profile. Radiolabeled monoclonal antibodies can induce durable remissions in lymphoma with toxicity limited largely to bone marrow suppression. Clinical trials with immunotoxins have demonstrated anti-tumor activity but also have been associated with significant toxicity. Standard treatment options for B-cell lymphoma will soon include antibody-based therapies. Further basic and clinical research is needed so we can understand more thoroughly the mechanisms responsible for the observed anti-tumor effects, and explore more extensively the best approach to their clinical use.

Direct immobilization of gangliosides onto gold-carboxymethyldextran sensor surfaces by hydrophobic interaction: applications to antibody characterization

We describe a novel immobilization technique to investigate interactions between immobilized gangliosides (GD3, GM1, and GM2) and their respective antibodies, antibody fragments, or binding partners using an optical biosensor. Immobilization was performed by direct injection onto a carboxymethyldextran sensor chip and did not require derivatization of the sensor surface or the ganglioside. The ganglioside appeared to bind to the sensor surface by hydrophobic interaction, leaving the carbohydrate epitope available for antibody or, in the case of GM1, cholera toxin binding. The carboxyl group of the dextran chains on the sensor surface did not appear to be involved in the immobilization as evidenced by equivalent levels of immobilization following conversion of the carboxyl groups into acyl amino esters, but rather the dextran layer provided a hydrophilic coverage of the sensor chip which was essential to prevent nonspecific binding. This technique gave better reactivity and specificity for anti-ganglioside monoclonal antibodies (anti-GD3: KM871, KM641, R24; and anti-GM2: KM966) than immobilization by hydrophobic interaction onto a gold sensor surface or photoactivated cross-linking onto carboxymethydextran. This rapid immobilization procedure has facilitated detailed kinetic analysis of ganglioside/antibody interactions, with the surface remaining viable for a large number of cycles (>125). Kinetic constants were determined from the biosensor data using linear regression, nonlinear least squares and equilibrium analysis. The values of kd, ka, and KAobtained by nonlinear analysis (KAKM871 = 1.05, KM641 = 1.66, R24 = 0.14, and KM966 = 0.65 x 10(7) M-1) were essentially independent of concentration and showed good agreement with data obtained by other analytical methods.

Variable region gene segments of nine monoclonal antibodies specific to disialogangliosides (GD2, GD3) and their O-acetylated derivatives

Despite the weak immunogenicity of gangliosides, a limited number of highly specific murine monoclonal antibodies (MAbs) were elicited. This study investigated the reactivity and the structure of the VH and V kappa genes of nine hybridomas obtained from independent fusions producing antibodies against disialogangliosides GD2 and GD3 and their O-acetylated derivatives. These antibodies depended on four types of V kappa genes. They were also encoded by VH genes of the J558 family (5 out of 9) and occasionally by VH genes of the S107, 7183, and 3609 families, rearranged with a variety of DH and JH genes. The 8B6 and 7H2 MAbs specific for GD2-O-acetylated, respectively, used the VH gene of the S107 and 7183 families. The length of H chain CDR3 ranged from 8 to 11 amino acids. A set of S107 and 3609 germline genes closed from A/J murine fetal liver and matched with the VH segment of hybridomas 8B6 and 10B8 revealed somatic mutations. Although the relative number of sequences does not preclude any formal conclusions regarding the preferential use of V genes in the immune recognition of carbohydrate structures, our results clearly indicate that MAbs directed to very similar structures as GD2 and GD3 were encoded by different VH and V kappa genes.

Anti-GD3 antibodies are potent activators of human gamma/delta and alpha/beta positive T cells

The ganglioside GD3 has a variety of biological functions. These include stimulatory effects on proliferation, natural killer activity and cytokine production by freshly isolated peripheral T cells. In this study we have characterized anti-GD3 antibody (MoAb Z21) mediated effects on T cell clones. Our data indicate that alpha/beta TCR CD4+ and CD8+ as well as gamma/delta TCR positive T cells can be stimulated resulting in proliferation and cytokine production. This effect could be blocked by cyclosporin A and did not involve the LFA-3 or CD4 molecule. Apart from IFN-gamma and IL-2 production by T helper 1 and T helper 0 cells we have observed production of IL-4 and IL-10 by T helper 2 cells indicating that the GD3 molecule is not a marker for a certain functional T cell subset. In contrast to anti-CD3 mediated activation, the responsiveness of T cells to stimulation via GD3 was dependent on the cell surface expression of the molecule and could be enhanced by costimulation via CD2, CD3, CD26 or CD28. In addition, anti-GD3 antibodies delivered a potent costimulatory signal for antigen-induced proliferation of CD4+ T lymphocytes. In summary, our experiments illuminate the mechanisms of anti-GD3 antibody induced T cell activation.

Characterization and biodistribution of a mouse/human chimeric antibody directed against pancreatic cancer mucin

BACKGROUND

Nd2 is a murine monoclonal antibody (MoAb) directed against purified mucins of the human pancreatic cancer cell line SW1990. The authors previously reported promising results with Nd2 for immunotargeting pancreatic cancer. However, murine MoAbs induce human anti-mouse antibodies (HAMAs), a serious problem for clinical use. Mouse/human chimeric antibodies may be less immunogenic and therefore reduce the incidence of HAMAs. In this study, the binding affinity, tumor specificity, biodistribution, and immunoimaging of chimeric Nd2 were evaluated.

METHODS

The affinity of chimeric Nd2 was evaluated by competition radioimmunoassay and Scatchard analysis using 125I-chimeric Nd2, 125I-murine Nd2, and SW1990 mucin. Immunoreactivity against pancreatic cancer tissues was examined histochemically by the avidin-biotin peroxidase complex method. The biodistribution of the MoAbs was examined in athymic nude mice bearing SW1990 xenografts that were administered intravenous 125I-labeled chimeric or murine Nd2. 111In-chimeric Nd2 was injected into the same xenograft models, and scintigrams were obtained on day 3.

RESULTS

Affinity analysis and immunohistochemical studies showed that chimeric Nd2 had the same affinity to SW1990 mucin and the same specificity for pancreas cancer tissues as murine Nd2. Intravenous administration of 125I-chimeric Nd2 resulted in a maximum tumor accumulation of 43% of the initial dose/gram of tumor, which was almost identical to the accumulation of 125I-murine Nd2. Distinct immunoscintigrams of tumors in nude mice were obtained with 111In-chimeric Nd2.

CONCLUSION

Chimeric Nd2 may have clinical potential in the radioimmunodetection and immunotherapy of pancreatic cancer.

A new vector for the high level expression of chimeric antibodies in myeloma cells

We previously reported the expression of a mouse/human chimeric anti-ganglioside GD3 antibody, KM871 (IgG1,kappa) in mouse myeloma SP2/0 cells under the control of the ecotropic Moloney virus long terminal repeat by the co-transfection of chimeric heavy (H) and light (L) chain vectors (Shitara et al. (1993) Cancer Immunol. Immunother.). To establish an efficient and high level expression system for the chimeric antibody, we did comparative study on vector systems and host cells. An improved expression vector, named 'a tandem vector, pChi641HLGM4' was constructed, in which both of the chimeric H and L chain gene transcription units and a dihydrofolate reductase (dhfr) gene transcription unit were inserted. When two kinds of mouse myeloma cell lines, SP2/0 and P3U1, were used as host cells, frequency of the incidence of antibody-producing transfectants was markedly increased by the use of the tandem vector compared with the use of the mixture of each chimeric H vector and L chain vector. To select out appropriate host cells, transfection frequency and antibody production level were compared among SP2/0, P3U1 and rat myeloma YB2/0 cells by transfection of the tandem vector. YB2/0 cell was shown to have the highest potential in both the transfection frequency and the antibody production. Introduction of the tandem vector into YB2/0 cells and the subsequent amplification with 50-200 nM methotrexate gave rise to several clones that stably secreted 70-100 micrograms/10(6) cells per 24 h of the chimeric antibody. This productivity of the antibody is one of the highest levels which have been achieved by other investigators using transfected myeloma cells. Using this system it took only 2-3 months to establish the transfectant clones which stably produced the chimeric antibody.