Pretargeted radioimmunoscintigraphy in patients with primary colorectal cancer using a bispecific anticarcinoembryonic antigen CEA X anti-di-diethylenetriaminepentaacetic acid F(ab')2 antibody.

BACKGROUND: Antibody-based imaging agents are available commercially, but their success has been limited, mainly because of low contrast and the emergence of 2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) scanning. In pretargeting, administration of the radionuclide is separated from the antibody, thereby enhancing image contrast and allowing detection at earlier time points after injection. METHODS: The authors conducted an open-label, single-arm trial that assessed a pretargeting procedure in which an anticarcinoembryonic antigen x (anti-CEA x) anti-diethylenetriaminepentaacetic acid (anti-DTPA)-indum (In) antibody was used in combination with a (111)In-labeled di-DTPA peptide for the diagnostic imaging of CEA-expressing colorectal cancer. Three patients received the (111)In peptide alone to investigate tumor targeting, organ distribution, and clearance of the peptide. Thereafter, 11 patients received the bispecific antibody (bsAb) (5 mg) to pretarget the tumor. After 3 to 5 days, patients were injected with 185 megabecquerels of (111)In-labeled peptide to assess the optimal interval for best image quality. RESULTS: Fourteen patients with primary colorectal cancer were enrolled. One of 3 patients who received (111)In peptide alone had low-level tumor uptake. In 9 of 11 other patients, tumors were observed. In 1 patient, FDG-PET-positive lymph nodes were observed clearly with pretargeted immunoscintigraphy. Peptide pharmacokinetics revealed enhanced circulating levels of (111)In-labeled peptide in patients in the 3-day interval cohort compared with the other cohorts. Tumor-to-background ratios ranged from 3.5 to 6.4 in the 3-day interval group, from 5.1 to 14.2 in the 4-day interval group, and from 3.5 to 3.9 in the 5-day interval group. The best images were acquired with a 4-day interval at 24 hours after injection of the radiolabeled peptide. Grade 1 adverse events were observed in 2 patients. CONCLUSIONS: Imaging of colorectal cancer using a 2-step, pretargeting system produced the best imaging results 24 hours after peptide administration using a 4-day interval between injection of the bsAb and the peptide.

Radioimmunoimaging with longer-lived positron-emitting radionuclides: potentials and challenges.

Radioimmunoimaging and therapy has been an area of interest for several decades. Steady progress has been made toward clinical translation of radiolabeled monoclonal antibodies for diagnosis and treatment of diseases. Tremendous advances have been made in imaging technologies such as positron emission tomography (PET). However, these advances have so far eluded routine translation into clinical radioimmunoimaging applications due to the mismatch between the short half-lives of routinely used positron-emitting radionuclides such as (18)F versus the pharmacokinetics of most intact monoclonal antibodies of interest. The lack of suitable positron-emitting radionuclides that match the pharmacokinetics of intact antibodies has generated interest in exploring the use of longer-lived positron emitters that are more suitable for radioimmunoimaging and dosimetry applications with intact monoclonal antibodies. In this review, we examine the opportunities and challenges of radioimmunoimaging with select longer-lived positron-emitting radionuclides such as (124)I, (89)Zr, and (86)Y with respect to radionuclide production, ease of radiolabeling intact antibodies, imaging characteristics, radiation dosimetry, and clinical translation potential.

Radioimmunoscintigraphy and radioimmunotherapy in cancer: principles and application.

Radioimmunoscintigraphy (RIS) and radioimmunotherapy (RIT) are recent approaches in the diagnosis and treatment of cancer. They take advantage of the antibody specificity of tumor surface antigens and of the emitted radiation from suitable radioisotopes, as a means of imaging (RIS) or therapy (RIT). Research into RIS and RIT radiolabelled agents remains an ongoing process. Principles governing the choice of radionuclides, labelling protocols, antibody suitability, and optimization of "tumor to normal tissue ratios" are the same for both RIS and RIT. The investigational stages of the labelled product, prior to clinical application, are also the same. These stages include radiochemical and radiobiological evaluation as well as determination of immunoreactivity. Furthermore, RIS may be considered as the first stage in development, before progressing on to RIT. Differences between RIS and RIT are associated with the application of each technique, that is, the type of radiation emitted by the isotope, dosage regimens, haematopoetic toxicity and the appearance of human antimurine antibody response (HAMA). RIS has found widespread clinical application, detecting a variety of tumors. However, its potential lies in patient management and in detecting metastases. On the other hand RIT is still in its infancy. It appears promising, and for the moment is used as a complementary technique to surgery and/or chemotherapy in clinical trials on cancer treatment. Finally, incorporation of these basic principles arising from past experiences, into the design of RIT trials improve responses.

Radioimmunodiagnosis and therapy.

Although promising results with radioimmunotherapy and radioimmunodiagnosis in haematological diseases, have been reported, they are less encouraging results in solid tumours. Experimental mathematical models suggest that optimization of antibody-based therapy and diagnosis is possible and that further research towards improvement is warranted. In this review, the major problems of radioimmunotherapy and diagnosis are discussed. Particular items adressed include tumour uptake of antibodies and antibody-fragments, the target/non-target ratio, immunogenicity and the selection of radionuclides.

Jod-Basedow syndrome following oral iodine and radioiodinated-antibody administration.

This is a case of thyrotoxicosis, presumably due to Jod-Basedow syndrome, after stable iodine ingestion for thyroid blockade in a patient with ovarian carcinoma having 131I-labeled monoclonal antibody imaging. With the increased use of radioiodinated antibodies, for therapy and imaging, this possible side effect of excess stable iodine administration should be noted, especially in patients with pre-existing goiter.

Assessment of disseminated pancreatic cancer: a comparison of traditional exploratory laparotomy and radioimmunoguided surgery.

BACKGROUND: After curative resection for pancreatic cancer, only 10% of patients survive disease for 5 years. These dismal results suggest the presence of occult tumor at the time of initial operation. This phase I/II study was conducted to compare traditional exploratory laparotomy with radioimmunoguided surgery (RIGS) in the assessment of disseminated pancreatic cancer. METHODS: Ten patients with the diagnosis of adenocarcinoma of the pancreas were injected intravenously with 1 mg CC49 monoclonal antibody radiolabeled with 2 mCi iodine 125. All patients were evaluated by a standard abdominal exploration followed by RIGS. Tumor identified by each technique was documented and categorized as neoplasm disseminated to viscera or lymphatics. RESULTS: There were 25 visceral sites of disease that were traditionally discovered at the time of exploration including pancreas, omentum, small bowel, pelvis, liver, and other. All 25 sites of disease were positive by RIGS plus an additional four sites of visceral tumor for a total of 29 RIGS positive sites of disease. Six lymphatic sites of disease were discovered by traditional examination; however, 44 sites of lymphatic sites were documented by RIGS (p < 0.001). In addition, nine traditionally and pathologically negative/RIGS positive nodes were subjected to cytokeratin and MOC 31 immunohistochemistry. Six of nine nodes were positive by cytokeratin immunohistochemistry, and five of the six cytokeratin positive nodes were MOC 31 positive. CONCLUSIONS: These data suggest that the RIGS technique detected significantly more foci of visceral spread of tumor than traditional exploratory laparotomy and significantly more sites of lymphatic dissemination were identified by RIGS than by standard exploration.

Yttrium-90/indium-111-DOTA-peptide-chimeric L6: pharmacokinetics, dosimetry and initial results in patients with incurable breast cancer.

BACKGROUND: Radioimmunotherapy (RIT) using 131I-Chimeric L6 (ChL6) antibody has shown therapeutic promise for patients with breast cancer. To enhance this potential, a novel immunoconjugate was developed that targets adenocarcinomas like breast cancer and tightly binds yttrium-90 (90Y) for therapy and indium-111 (111In) for imaging. The radioimmunoconjugate consists of a macrocyclic chelator (DOTA) linked to ChL6 by a catabolizable peptide. 90Y-DOTA-peptide-ChL6 was designed to minimize the radiation dose to critical normal tissues, thereby improving the therapeutic index. MATERIALS AND METHODS: Three patients with incurable metastatic breast cancer received 90Y/111In-DOTA-peptide-ChL6 for 5 pharmacokinetics/dosimetry studies and one of these patients also received 2 therapy doses. Quantitative imaging of 111In and in vitro assay of 90Y and 111In in blood urine and bone marrow samples were obtained. RESULTS: 90Y/111In-DOTA-peptide-ChL6 was prepared at high purity and was stable in vivo. Assays of bone marrow revealed no evidence for escape of 90Y or 111In from the chelate. 111In imaging of tumors was excellent, providing a therapeutic index for tumor to marrow radiation as high as 229 to 1. 90Y and 111In provided comparable pharmacokinetics, as did tracer and therapeutic doses of radioimmunoconjugates. One patients that received 2 therapeutic doses of 90Y-DOTA-peptide-ChL6 showed regression of tumors and tumor markers. Toxicities were relatively minor and no anti-globulin response developed despite 5 immunoconjugate infusions. CONCLUSIONS: This first study in patients of radioimmunoconjugates with a catabolizable linker between the metal chelator and the antibody confirmed that these novel 90Y/111In-DOTA-peptide-ChL6 radioimmunoconjugates have significant potential. Tracer doses of 111In-DOTA-peptide-ChL6 for imaging predicted the behavior of therapeutic doses of 90Y-DOTA-peptide-ChL6. The latter radioimmunoconjugate induced regression of tumors and tumor markers without significant toxicity. When compared to earlier 131I-ChL6 dosimetry, 90Y-DOTA-peptide-ChL6 provided a therapeutic index several times better.

Hematologic side effects of radiolabeled immunoglobulin therapy.

Radiolabeled immunoglobulin therapy (RIT) is a new cancer treatment that is more selective than its predecessors. Its dose-limiting normal tissue side effect is bone marrow toxicity, and hematopoietic stem cell damage appears to be its most significant mechanism. Platelet consumption in irradiated normal liver tissues and apoptosis of circulating peripheral blood lymphocytes are other, less important, hematologic side effects. 131I and 90Y are the radioisotopes most commonly used for RIT; in addition, animal toxicology and initial clinical studies of chelate immunoglobulins radiolabeled with 111In (for diagnosis) or 90Y (for therapy) are reviewed. The bone-seeking properties of free 90Y are not considered to be a major component of the hematologic damage caused by yttrium-labeled immunoglobulins. The microenvironment of the bone marrow system is not significantly damaged by current RIT protocols. Moreover, granulocyte colony-stimulating factor (G-CSF) can open the blood-marrow barrier. Bone marrow toxicity after RIT can be corrected by bone marrow transplantation, growth factors, blood products, or fractionation of RIT. Selection of the appropriate corrective regimen depends on the severity of the bone marrow damage and will further enhance the therapeutic ratio of RIT.

Immunotechnological trends in radioimmunotargeting: from 'magic bullet' to 'smart bomb'.

The impact of recent advances in the chemical and genetic engineering manipulations of antibodies on radioimmunotargeting is reviewed both in relation to radioimmunoscintigraphy and radioimmunotherapy. The resulting trends are: (1) the linking of parts of the mouse/rat and human antibody molecule; (2) the creation of molecules with dual antigen or multiple antigen recognition capabilities; (3) the making of smaller and smaller antigen recognition molecules; and (4) the development of molecules with dual capabilities, e.g. antigen recognition and enzyme activity. The various methods of creating antibodies in vitro are reviewed with reference to bacteria, using phage selection and a combinatorial library, mammalian cells, yeast cells and, finally, mice containing giant yeast artificial chromosomes. The advantages and disadvantages of smaller fragments as well as of the human anti-mouse antibody (HAMA) reaction are discussed and the need for early clinical evaluation and widespread availability of the newer antibodies is emphasized. It is envisaged that these immunotechnological advances will permit the large-scale production of precisely engineered humanized antibodies, and the specificity and affinity rate constant of these antibodies can be optimized using in vitro phage selection as well as by computer modelling where the stereo chemistry of the antigen is known precisely.

[Anti-melanoma immunoscintigraphy]. / Imunocintigrafia anti-melanoma.

Nuclear Medicine has always contributed to the study of oncologic diseases. Immunoscintigraphy, one of its more recent developments, consists of the evaluation of the biodistribution of antibodies, directed against tumoral antigens and labelled with radionuclides. This technique, which has proven of special interest in some neoplasias, was used for the first time in 1983 in malignant melanoma of the skin. The antibody that has been more frequently used and which is used in the Instituto de Medicina Nuclear (IMN) of the Faculdade de Medicina de Lisboa, is antibody 225.28S, an IgG2a directed against a high molecular weight antigen present in the melanoma cell. In the IMN, we started immunoscintigraphy anti-melanoma in February 1992. During these two years, we have performed 67 exams, 44 on patients with malignant melanoma of the skin and 23 on uveal melanoma. We have obtained true positive rates and true negative ones, respectively, of 87.5% and 90% in melanoma of the skin, and 94% and 83% in uveal melanoma. It has been shown that the main clinical contribution of immunoscintigraphy for malignant melanoma of the skin is the study of loco-regional and distant metastases, namely those clinically unsuspected, as well as in the differential diagnosis of a lesion already known. In uveal melanoma, it is accepted that immunoscintigraphy may be useful in the evaluation of the primary lesion, namely in the differential diagnosis with other intra-ocular lesions.

Radioimmunoscintigraphy with 111indium labeled CYT-356 for the detection of occult prostate cancer recurrence.

We assessed the safety and ability of the 111indium labeled immunoconjugate 7E11-C5.3-glycyl-tyrosyl-(N,e-diethylenetriaminepentaacetic acid)-lysine (CYT-356) to detect sites of occult prostate cancer in 27 subjects who had undergone radical prostatectomy and whose only evidence of recurrent disease was an increasing (0.8 ng./ml. or greater) serum prostate specific antigen (PSA). All subjects underwent whole body scintigraphy between 2 and 4 days following the radiopharmaceutical injection. Routine blood work and human anti-mouse antibody titers were monitored. Scintigraphic findings were compared with clinical parameters, prostatic fossa biopsy results and conventional imaging techniques. Except for transient hypotension in 1 subject following the second infusion, no side effects or human anti-mouse antibody titers were detected. In 22 subjects 1 or more lesions were detected, of which 11 (50%) were confirmed by biopsy, computerized tomography or magnetic resonance imaging. Of 14 subjects with lesions in the prostatic fossa 13 had biopsies performed, 8 (62%) of which were positive. Magnetic resonance imaging confirmed tumor in the spine and chest computerized tomography findings were compatible with lesions seen in the mediastinum in 1 subject each. There was a statistically significant relationship between detecting a scan abnormality and the initial pathological stage of disease but not with the serum PSA. These data provide preliminary evidence that 111indium labeled CYT-356 can be safely administered and readministered, and it detects sites of occult prostate cancer recurrence in subjects whose PSA is increasing following radical prostatectomy.

New developments in monoclonal antibodies for cancer detection and therapy.

Monoclonal antibodies have provided clinicians with an intriguing, target-specific approach to cancer management. Used alone or conjugated with drugs, toxins, or radionuclides, monoclonal antibodies have been shown to be useful in the detection and/or treatment of several cancers. Recent advances, such as the development of "humanized" antibodies, promise to increase their effectiveness even more. This article summarizes the status of the in vivo use of monoclonal antibodies for cancer detection and therapy.

Pitfalls in antibody imaging in colorectal cancer.

Monoclonal antibodies against tumor-associated antigens can be conjugated to radionuclides and used to localize tumors in vivo. This technique may be useful in identifying recurrent disease that cannot be demonstrated using conventional studies such as computerized tomography. The literature suggests that the use of antibody fragments and SPECT imaging will increase the diagnostic yield. The choice of radionuclide may vary depending on the region of interest. Factors that influence the success of imaging include the experience of individuals interpreting the scan and the level of tissue antigen expression. Antibodies of murine origin may produce a human antimouse antibody response after imaging, causing allergic responses, interference with subsequent imaging or results of standard in vitro laboratory tests. Finally, false-positive images occur in more than 10% of patients. Current studies in patients with colorectal cancer should focus on determining if changes in management resulting from antibody imaging have a positive effect on either patient survival or quality of life.

Antibody localization in human renal cell carcinoma: a phase I study of monoclonal antibody G250.

PURPOSE: To define the imaging and biodistribution characteristics of iodine 131-labeled monoclonal antibody (mAb) G250 (131I-mAbG250), which recognizes a cell-surface antigen expressed by human renal cell carcinoma (RCC). PATIENTS AND METHODS: G250 is a cell-surface antigen recognized by mAbG250 expressed by RCC but not detected in normal kidney. Clear-cell RCC, the most frequent form of RCC, shows homogeneous expression of G250, whereas non-clear-cell RCC and cancers derived from other organs generally do not express G250. Expression in normal tissues is highly restricted and limited to large bile ducts and gastric epithelium. 131I-mAbG250 was administered intravenously (IV) to 16 patients with RCC 7 to 8 days before surgery at five dose levels, with at least three patients entered at each dose level. RESULTS: Clear tumor images were observed in 12 patients with G250-positive tumors and in one of three patients with G250-negative tumors. Imaged lesions in the peritoneal cavity were confirmed at surgery. The smallest lesion visualized was 8 mm in diameter. The specificity of 131I-mAbG250 localization to tumor tissue was established by radioactivity measurements, autoradiography, and immunohistochemistry of biopsied tissues, and technetium 99-human serum albumin blood-flow studies. The fraction of the injected 131I-mAbG250 dose per gram tumor (%ID/g tumor) localized in G250-positive tumors showed a broad range, but reached levels as high as 0.02% to 0.12%. CONCLUSION: 131I-mAbG250 localized specifically to G250 antigen-positive RCC and seems to have considerable potential as an imaging agent in RCC patients. 131I-mAbG250 uptake in the tumors, relative as well as absolute, are among the highest reported for tumor biopsies obtained 8 days after IV mAb administration. Based on the specific localization and high accumulation, mAb G250 may have therapeutic potential.

Multicenter clinical trials of monoclonal antibody B72.3-GYK-DTPA 111In (111In-CYT-103; OncoScint CR103) in patients with colorectal carcinoma.

The results of this clinical trial involving 23 sites indicated that 111In-CYT-103 immunoscintigraphy identified 70% of all patients with surgically confirmed disease when interpreted by the on-site physician. The sensitivity of 111In-CYT-103 imaging was slightly lower when interpreted retrospectively by the blinded readers in the absence of any patient-specific information. 111In-CYT-103 imaging sensitivity was similar in patients with primary and recurrent disease, but lower for liver metastases than for extrahepatic disease. Thirty-three previously unknown lesions were visualized by immunoscintigraphy; tissue confirmation was available for only five lesions, and all were found to be free of tumor. Only one of the lesions evaluated was TAG-72 positive. Twenty-eight lesions were outside the surgical field or not biopsied. Although no tissue confirmation was available, seven (25%) of these lesions were identified as consistent with metastatic disease by other conventional modalities. Importantly, antibody scans detected occult tumor lesions in 11 of the 92 patients with surgically confirmed adenocarcinoma, and accurately diagnosed 7 of 10 patients with elevated serum CEA levels and negative conventional workup. Surgery confirmed the presence of tumor identified only by 111In-CYT-103 in three patients, while four patients with negative scans had no evidence of recurrent disease at surgery. Antibody scans confirmed the absence of additional disease in 18 of 22 patients with isolated hepatic or pelvic recurrences in whom curative surgery was contemplated. The results of this multicenter trial suggest that CYT-103 immunoscintigraphy can provide information that is complementary to that derived from standard diagnostic techniques. During the workup of patients with primary colorectal carcinoma, this modality assesses the entire body and allows for the identification of multiple lesions at various locations simultaneously. It can then redirect attention and further workup to those areas not originally surveyed. Of special interest in this regard is the identification of occult lesions in five patients with primary colorectal cancer. 111In-CYT-103 imaging was found superior to CT in the localization of primary colorectal cancer, but neither modality could adequately assess the extent of tumor penetration through the bowel wall (the T stage in the TNM system) or the N status. The limitations of CT in evaluating T and N are well documented, and the limitations of 111In-based immunoscintigraphy for these same lesions have recently been described. Another limitation of 111In-CYT-103 immunoscintigraphy is in the identification of liver metastases.(ABSTRACT TRUNCATED AT 400 WORDS)

Second antibody for improvement of antibody imaging: liposome-entrapped and free preparations in animal and human studies.

When anti-tumour antibodies are given systematically for tumour imaging or therapy, second antibody directed against the first (anti-tumour) antibody can be used to accelerate clearance of first antibody, thus improving discrimination between tumour and normal tissues. Liposome-entrapped, and free second antibodies (LESA and FSA, respectively) have been compared in an animal tumour model system and in patients with cancer. Nude mice bearing xenografts of human colon carcinoma were given goat antibody to carcino-embryonic antigen (CEA) as first antibody and horse anti-goat second antibody. Patients with gastrointestinal carcinomas received i.v. 131I-labelled goat anti-CEA or mouse monoclonal 17-1A first antibody and unlabelled horse angi-goat or rabbit anti-mouse second antibody, respectively. Antibody distribution was studied by serial gamma camera imaging. The effectiveness of LESA and FSA depended on dose. Tumour-to-blood ratios were increased up to eight-fold by either method in animals. Tumour imaging was enhanced among 15 patients with gastrointestinal cancer and tumour was correctly identified at five sites where it was not seen by a background subtraction method. No significant toxicity occurred in patients nor in rabbits studied for evidence of immune complex mediated disease. LESA and FSA appear to be equally effective.