Survey of methods for measuring human anti-mouse antibodies

Naptumomab estafenatox: a new immunoconjugate

IMPORTANCE OF THE FIELD

New agents that specifically engage the immune system are being tested in a variety of malignancies. This review provides an overview of naptumomab, an immunotoxin, with encouraging clinical activity in Phase I trials.

AREAS COVERED IN THIS REVIEW

This review examines the preclinical and the published clinical data with regards to naptumomab.

WHAT THE READER WILL GAIN

This review provides the reader with an understanding of the mechanism of action, immunology, pharmacokinetics and clinical activity of this agent.

TAKE HOME MESSAGE

Naptumomab has a unique mechanism of action and appears to be an active agent in the treatment of refractory solid tumors such as renal cell carcinoma.

Prevalence of human anti-mouse antibodies (HAMAs) in routine examinations

BACKGROUND

Circulating heterophilic antibodies interfere with immunological assays in laboratory examinations; however, their rate of incidence is currently questionable. We developed an enzyme-linked immunosorbent assay (ELISA) to detect human anti-mouse antibodies (HAMAs) in routine examinations.

METHODS

The study samples were comprised of serum samples obtained from 290 inpatients and outpatients at our hospital. Mouse immunoglobulin G1 (mIgG1), mIgG2a, and mIgG2b were used as the antigens and horseradish peroxidase (HRP)-conjugated anti-human IgG and IgM were used to identify the HAMA isotype.

RESULTS

HAMAs were detected in 11.7% (34/290) of the samples. We observed 18 and 20 samples positive for IgG- and IgM-type HAMAs, respectively. Four samples contained both IgG- and IgM-type HAMAs. HAMAs against mIgG1, mIgG2a, and mIgG2b were found in 21, 14, and 13 samples, respectively. Existence of HAMAs was confirmed by western blotting using mIgG's as the antigens and HAMAs as the primary antibodies. Heterophilic blocking reagent (HBR) was also used to block the heterophilic interactions. Unexpectedly, a low HBR concentration rather enhanced the interactions instead of blocking them.

CONCLUSIONS

A considerable number of HAMA-positive samples, reacting with the heavy chain of mIg, were found in routine examinations. A sufficient amount of HBR should be used for blocking the heterophilic interactions.

Immunogenicity of Iodine 131 chimeric tumor necrosis therapy monoclonal antibody in advanced lung cancer patients

PURPOSE

Iodine-131 radiolabeled chimeric tumor necrosis therapy monoclonal antibody ((131)I-TNT) has been approved for the treatment of advanced lung cancer in China. In the present study, the immunogenicity of TNT was studied in advanced lung cancer patients using BIACORE and enzyme linked immunosorbent assay (ELISA) methods.

EXPERIMENTAL DESIGN

Serum samples from 78 advanced lung cancer patients were analyzed for antibody development to TNT after systemic or intratumoral administration of two doses of (131)I-TNT. Patients' sera were obtained before, and 2 weeks and 2 months after (131)I-TNT radioimmunotherapy.

RESULTS

Four of 78 lung cancer patients (4/78 or 5.13%) developed antibodies to TNT as measured by ELISA method, and 7 of 78 patients (8.97%) development anti-TNT antibody as measured by BIACORE biosensor after 2 doses of (131)I-TNT administration (P > 0.05). All the 4 ELISA-positive patients were also BIACORE-positive. Among the 7 BIACORE-positive patients, 5 (of 42, 11.9%) patients receiving intravenous TNT injection developed antibodies to TNT, and 2 (of 36, 5.56%) patients, receiving intratumoral therapy developed antibodies to TNT. The route of administration of the radiolabeled TNT antibody was not a statistically significant factor in the incidence of anti-TNT antibody. Detailed BIACORE serological analysis showed that the induced antibodies were mostly of the IgG1 subclass.

CONCLUSIONS

(131)I-TNT was immunogenic in only a small minority of advanced lung cancer patients (8.97%). The route of administration did not statistically influence the incidence of anti-TNT antibody after TNT radioimmunotherapy in lung cancer patients.

A phase II study of a 5T4 oncofoetal antigen tumour-targeted superantigen (ABR-214936) therapy in patients with advanced renal cell carcinoma

In a phase II study, 43 renal cell carcinoma patients were treated with individualised doses of ABR-214936; a fusion of a Fab recognising the antigen 5T4, and Staphylococcal enterotoxin A. Drug was given intravenously on 4 consecutive days, treatment was repeated 1 month later. Treatment was associated with moderate fever and nausea, but well tolerated. Of 40 evaluable patients, 28 had disease control at 2 months, and at 4 months, one patient showed partial response (PR) and 16 patients stable disease. Median survival, with minimum follow-up of 26 months was 19.7 months with 13 patients alive to date. Stratification by the Motzer's prognostic criteria highlights prolonged survival compared to published expectation. Patients receiving higher drug exposure had greater disease control and lived almost twice as long as expected, whereas the low-exposure patients survived as expected. Sustained interleukin-2 (IL-2) production after a repeated injection appears to be a biomarker for clinical effect, as the induced-IL-2 level on the day 2 of treatment correlated with survival. The high degree of disease control and the prolonged survival suggest that this treatment can be effective. These findings will be used in the trial design for the next generation of drug, with reduced antigenicity and toxicity.

Human anti-mouse antibodies

Human anti-mouse antibodies (HAMA) are human immunoglobulins with specificity for mouse immunoglobulins. This topic currently is of interest because of the increased use of monoclonal mouse antibodies as diagnostic reagents both for in vitro laboratory measurements and for in vivo imaging studies. Monoclonal mouse antibodies also are being used therapeutically. This short article reviews the production of HAMA in patients receiving monoclonal antibodies and illustrates the potential ways that HAMA can interfere with immunoassay measurements. Methods for measuring and neutralizing HAMA also are discussed.

Human anti-murine antibodies interfere with CPR assays performed with commercial kits

Quantitation of C-peptide is important for the assessment of insulin secretion, in particular in patients receiving insulin therapy. Since the CPR levels become much higher than the concentration of C-peptide for several reasons, such as the high concentration of proinsulin, CPR values sometimes need to be assessed carefully. We have had two diabetic patients whose CPR values were abnormally high when determined with a Daiichi C-peptide kit III (method 1). CPR values determined by other methods were from two to ten times lower, indicating considerable interference when method 1 was used. Since method 1 uses mouse monoclonal antibodies (mmab) for detection antibodies, we suspected that human anti-murine antibodies (HAMA) were responsible for the interference. HAMA were detected in serum from both patients (45 and 460 ng/ml in case 1 and case 2 (at peak), respectively). Removal of HAMA from serum eliminated the interference. Modification of method 1 to exclude mmab from the assay system removed all interference. HAMA were, therefore, considered to be the cause of the interference. In case 2, the peak concentration of HAMA was recorded 16 months earlier than the maximum of interference. Further analysis revealed that HAMA with high affinities were responsible for the interference.

An illustration of the clinical relevance of detecting human antimouse antibody interference by affinity chromatography

Elevated Cancer antigen 125 (CA 125) serum concentrations (up to 221 kU/1) were measured in a 39 year old woman with a positive family history of breast cancer. The serum determinations were performed with the automated Immulite OM-MA chemiluminescent enzyme immunoassay system (Diagnostic Products). Laparoscopic evaluation of the ovaries did not reveal any abnormalities. CA 125 measurements in the same patient using the automated IMx immunoassay system (Abbott) demonstrated normal serum levels. Using a previously reported chromatography procedure IgG type human antimouse antibody activity was found to be present in the serum samples explaining the falsely elevated levels. To prevent this interference the manufacturer modified the assay system by replacing the monoclonal M11 detection antibody with a rabbit polyclonal antibody. Using the modified OM-MA CA 125 assay results were comparable with the IMx values.

Human Anti-Animal Antibody Interferences in Immunological Assays

Purpose: The scope and significance of human anti-animal antibody interference in immunological assays is reviewed with an emphasis on human anti-animal immunoglobulins, particularly human anti-mouse antibodies (HAMAs).

Issues: Anti-animal antibodies (IgG, IgA, IgM, IgE class, anti-isotype, and anti-idiotype specificity) arise as a result of iatrogenic and noniatrogenic causes and include human anti-mouse, -rabbit, -goat, -sheep, -cow, -pig, -rat, and -horse antibodies and antibodies with mixed specificity. Circulating antibodies can reach gram per liter concentrations and may persist for years. Prevalence estimates for anti-animal antibodies in the general population vary widely and range from <1% to 80%. Human anti-animal antibodies cause interferences in immunological assays. The most common human anti-animal antibody interferent is HAMA, which causes both positive and negative interferences in two-site mouse monoclonal antibody-based assays. Strategies to prevent the development of human anti-animal antibody responses include immunosuppressant therapy and the use of humanized, polyethylene glycolylated, or Fab fragments of antibody agents. Sample pretreatment or assay redesign can eliminate immunoassay interferences caused by anti-animal antibodies. Enzyme immunoassays, immunoradiometric assays, immunofluorescence, and HPLC assays have been designed to detect HAMA and other anti-animal antibodies, but intermethod comparability is complicated by differences in assay specificity and lack of standardization.

Conclusions: Human anti-animal antibodies often go unnoticed, to the detriment of patient care. A heightened awareness on the part of laboratory staff and clinicians of the problems caused by this type of interference in routine immunoassay tests is desirable. Efforts should be directed at improving methods for identifying and eliminating this type of analytical interference.

Minor human antibody response to a mouse and chimeric monoclonal antibody after a single i.v. infusion in ovarian carcinoma patients: a comparison of five assays

The human anti-(mouse Ig) antibody (HAMA) response was measured in serum of 52 patients suspected of having ovarian carcinoma who had received an i.v. injection of either the murine monoclonal antibody (mAb) OV-TL 3 F(ab')2 (n = 28, 1 mg) or the chimeric mouse/human mAb MOv18 (cMOv18; n = 24, 3 mg). Serum samples were taken before injection and 2-3 and 6-14 weeks after administration. A double-antigen or bridging assay was developed to detect responses against both murine as well as chimeric antibodies. In addition, an indirect enzyme-linked immunosorbent assay (ELISA) as well as three commercially available assays were used to study antibody response against the murine antibody OV-TL 3. With both the double-antigen (bridging) assay and the indirect ELISA 1 of the 28 patients (4%) injected with murine OV-TL 3 F(ab')2 showed a HAMA reaction 6 weeks after injection, which was demonstrated to be a mixed anti-isotypic and anti-idiotypic response. None of the 24 patients injected with the chimeric MOv18 showed an anti-chimeric antibody response. The various commercially available assays demonstrated conflicting results. The double-antigen- or bridging assay is a reliable method to detect anti-murine and anti-chimeric antibodies. The assay can be easily adapted for use with human antibodies. The immunogenicity of OV-TL 3 F(ab')2 and cMOv18 in patients is low, making both antibodies candidates for immunotherapy.