Direct labeling of monoclonal antibodies with technetium-99m by photoactivation

Direct radiolabeling methods currently rely on the addition of exogenous chemical reagents to create the necessary binding sites for 99mTc binding to monoclonal antibodies (MAbs). This work describes the use of ultraviolet (UV) light to facilitate photoactivation of MAbs for 99mTc radiolabeling.

METHODS

The parameters of exposure wavelength and solution composition were investigated to provide a basis for further development. Based on these results, various murine MAbs and a chimeric MAb were photoactivated using a 300-nm (nominal) wavelength, eight-lamp (3.9 W each) photochemical reactor providing exposure for defined time periods. The MAb preparations were stored frozen and subsequently labeled by the addition of pertechnetate. For MAb-170, the photoactivated preparation was compared to a stannous ion reduced preparation by radiochemical (radiolabeling yield, serum stability cysteine challenge), biochemical (SDS-PAGE, IEF, SE-HPLC) and immunochemical (immunoreactivity) assays and biodistribution studies in mice.

RESULTS

Photoactivation produced high radiolabeling yields for all the MAbs studied and MAb-170 produced comparable in vitro quality control profiles and in vivo biodistribution data.

CONCLUSION

The use of this relatively simple, short and easily controlled photoactivation process for MAbs facilitates facile radiolabeling with 99mTc and provides an alternative to the direct chemical radiolabeling procedures.

[Intraoperative localization of metastases with a hand-held gamma probe]

A 50-y-old male patient with prostate cancer showed two suspicious lesions in bone scintigrams. They were assessed to be bone metastases by biopsy of the os ilium. After i.v. injection of 99mTc-HMDP a probe-guided localization permitted optimal surgical treatment. A bone metastasis in the os ilium was confirmed. The intraoperative detection with a hand-held gamma probe permitted accurate and complete excision of the tumour; the bone defect could thus be reduced to a minimum.

Validation of a dual-isotope technique using 123I-MIBG and 201Tl in the assessment of sympathetic reinnervation following heart transplantation: phantom and patient studies

Dual-isotope studies using 123I and 201Tl allow the assessment of sympathetic reinnervation in patients following heart transplantation. 123I-meta-iodobenzyl guanidine (123I-MIBG) serves as a tracer of the integrity of the sympathetic nervous system. 201Tl is used for landmarking to allow better delineation of the myocardium due to faint 123I-MIBG accumulation in heart transplants. The aim of this study was to evaluate the influence of parameters such as crossover, attenuation and the 123I/201TI activity ratio on the assessment of the myocardial 123I-MIBG uptake ratio using phantom and patient studies. Crossover was calculated using the ratio: 201TI counts in the 123I energy window/201Tl counts in the 201Tl window. Phantom studies were performed using a rectangular phantom (RP) and a cardiac phantom (CP). The mean crossover from the 201Tl to the 123I energy window was 11.48% (RP) and 11.13% (CP). Depending on attenuation in water (depth of water 0-5 cm), crossover increased from 10.92 to 15.85% (RP) and from 11.05 to 15.79% (CP). In order to confirm that the experimental crossover results were equivalent to those obtained in patient studies, 15 patients underwent myocardial scintigraphy. After injection of 201Tl, a simultaneous dual-window acquisition was performed to assess crossover from the 201Tl to the 123I window. The mean crossover was 15.35%, as high as the crossover assessed in phantom studies, taking into account attenuation and scatter caused by the chest wall. In order to reduce 201Tl crossover, the 123I activities were six times as high as the 201Tl activities.(ABSTRACT TRUNCATED AT 250 WORDS)

[Value of SPECT-immunoscintigraphy in radiation treatment planning for patients with squamous cell carcinomas in the head and neck area]

PURPOSE

Introduction of monoclonal antibodies (immunoscintigraphy) has significantly extended the diagnostic spectrum of nuclear medicine in oncology. The detection rate of this new method in patients bearing squamous cell carcinoma of head and neck is better compared to computed tomography and magnetic resonance imaging. In a prospective study, we examined whether immunoscintigraphy in addition to other imaging procedures is able to provide additional diagnostic information for radiation treatment planning.

Antiidiotype induction therapy: evidence for the induction of immune response through the idiotype network in patients with ovarian cancer after administration of anti-CA125 murine monoclonal antibody B43.13

The immune status of ovarian cancer patients receiving anti-CA125 murine monoclonal antibody B43.13 was evaluated by measuring antiidiotypic antibodies (Ab2), antiantiidiotypic antibodies (Ab3), antiisotypic human antimouse antibodies (HAMA), interferon-gamma, and CA125 levels in the serum. A specific assay was developed for the determination of Ab2 antibodies using chimeric MAb B43.13. Of the 50 patients studied, 26 had elevated levels of Ab2. Eleven of these 26 patients also had high titer of antiantiidiotypic (Ab3) antibodies. Eight of the 22 patients analyzed had increased interferon-gamma levels. A tentative correlation was found between survival of these patients' antiidiotype induction.

Semiquantitative SPECT tumor uptake of technetium-99m-labeled anti-CEA monoclonal antibody in colorectal tumor

Technetium-99m-BW431/26 images were compared to images of resected tumor specimens to evaluate the efficacy and accuracy of SPECT imaging of colorectal carcinoma.

METHODS

Immunoscintigraphy with 99mTc-BW431/26 was performed on seven patients with colorectal carcinoma and one patient with a benign colorectal tumor. Accumulation of 99mTc-BW431/26 in the tumor was expressed as the tumor-to-normal tissue count ratio (SPECT T/N ratio) calculated by a region of interest method on the SPECT images obtained 24 hr after administration of 99mTc-BW431/26. All patients underwent research of the tumor immediately after 24-hr imaging, and the radioactivity in tumor specimen and normal tissue was measured to calculate the tissue T/N ratio.

RESULTS

SPECT demonstrated definite increased tracer uptake by the tumor in all colorectal cancer patients. The benign lesion showed tracer uptake to a lesser extent. SPECT, however, failed to visualize a 10-mm lesion in a patient with familial adenomatous polyposis despite a tissue T/N ratio of 4.8, while autoradiography showed radioactivity uptake in the polyps.

CONCLUSION

Although SPECT has limitations in detecting small lesions because of its limited spatial resolution, T/N ratios could be measured exactly by SPECT if the lesion is of a certain volume. SPECT imaging with 99mTc-BW431/26 can precisely evaluate tracer uptake in tumors and predict the efficacy of radioimmunotherapy in patients with colorectal cancer.

A pharmacokinetic comparison of murine and chimeric forms of the 99mTc-labelled 174H.64 monoclonal antibody

The monoclonal antibody (MoAb) 174H.64 (Truscint SQ, Biomira Inc.) is a murine-derived MoAb reacting with an extracellular surface component of the cytoskeletal matrix ectopically expressed on squamous-cell carcinoma cell-surface membranes. A chimeric form of this MoAb has also been produced by genetically modifying the Fc portion of the MoAb by the insertion of a human Fc fragment. During this process the isotype was altered from an IgG1 (murine) to an IgG3 (chimeric). Pilot and phase I/II clinical trials of the murine and chimeric 99mTc-labelled 174H.64 MoAbs have been undertaken at selected European and North American sites. As part of this evaluation serum, urine and image data were collected at specific time intervals and used to obtain a kinetic model to describe the in vivo distribution of the MoAbs. A two-compartment model of the form: C(t) = C1 e-lambda 1t + Cz e-lambda zt was found to best describe the serum distribution of radioactivity of both the murine and chimeric MoAbs. The initial distribution half-lives were 2.9 +/- 0.7 hours and 2.7 +/- 0.2 hours, and the terminal elimination half-lives were 17.6 +/- 3.8 hours and 22.5 +/- 1.3 hours for the murine and chimeric MoAbs, respectively. No significant difference was found between the kinetic model parameters of two MoAbs at the 95% level. Assuming a similar clinical efficacy, these MoAbs could then be used interchangeably, with the chimeric MoAb offering potential advantages in reducing HAMA response.

[Immunoscintigraphy of carcinomas in the area of the head-neck with technetium-99m marked monoclonal antibody 174H.64. A new diagnostic procedure]

Twenty-one patients with squamous cell carcinomas of the head and neck were studied by immunoscintigraphy and immunoemission, computed tomography (ECT) using monoclonal antibody 174H.64 (Biomira Edminton) labelled with 99Tcm (Schwartz Method). Immunoscintigraphic results were compared with routine clinical assessments, including CT and ultrasonography, and were controlled by histopathological examination after surgery. All primary localizations (pT1 = 3, pT2 = 3, pT3 = 7, pT4 = 5; oropharynx 7, larynx 5, hypopharynx 3, oral cavity 3, lymph nodes 3) could be visualized, while 15 out of 18 neck lesions from tumor metastases could also be visualized (pN1 = 8, pN2 = 8, pN3 = 2). In one case with micrometastases in lymph nodes that could not be demonstrated by other methods, staging was upgraded by the immunoscintigraphic results. Three other micrometastases in lymph nodes could not be visualized. Distant metastases were suspected in 5 cases, three of which were confirmed either histologically or by radiography. Two of the cases with distant metastases were detected by the immunoscintigraphy. The present results indicate that immunoscintigraphy in combination with immuno-ECT can improve preoperative staging of head and neck carcinomas, especially with regard to metastatic neck disease, tumor recurrences and some cases of distant metastases.

Immunoscintigraphy of human mammary carcinoma xenografts using monoclonal antibodies 12H12 and BM-2 labeled with 99mTc and radioiodine

For immunoscintigraphic localization of human breast cancer two monoclonal antibodies (mabs) 12H12 (immunoglobulin G1) and BM-2 (immunoglobulin G3) were developed. The mabs, directed against two different epitopes on the mucin glycoprotein TAG-12, showed reactivity with 96% of all primary mammary carcinomas. The antibodies were labeled with either 125I or 131I. In addition, 12H12 was directly labeled with 99mTc according to the method of Schwarz and Steinsträsser (A. Schwarz and A. Steinsträsser, J. Nucl. Med., 28:721, 1987). Biodistribution was measured in female nude mice bearing the human mammary carcinoma SF-15. Both radioiodinated mabs showed similar biodistribution with fast tumor uptake (8.5% injected dose/g at 6 h postinjection), which increased to 10-11% injected dose/g at 24 h and subsequently remained constant up to 120 h. 99mTc-Labeling of the mab 12H12 led to an enhanced tumor uptake of 10.5 and 14% injected dose/g at 6 and 24 h postinjection, respectively, and to significantly accelerated blood clearance of radioactivity. Similar results were obtained with a second mammary tumor (AR-1), while an endometrial tumor (EK-3) showed a 3-fold lower accumulation of radioactivity and no difference in uptake of radio-iodinated and 99mTc-labeled 12H12. Scintigraphic imaging of tumor-bearing nude mice with the 99mTc 12H12 at 24 h postinjection clearly demonstrated a diagnostic potential of the new mab for tumor localization and staging.

[Intestinal accumulation of 99mTc-HMDP: an unusual finding in bone scintigraphy]

In a 61-year old female with a history of breast cancer the whole-body scan (4 h p.i.) after intravenous injection of 576 MBq 99mTc-HMDP showed an accumulation of activity in the stomach and the whole intestines. The reason was an oral urine intake ("uropotia") taking place between the injection and the whole-body bone scan.

Initial clinical results with technetium-99m-labeled LL2 monoclonal antibody fragment in the radioimmunodetection of B-cell lymphomas

BACKGROUND

Various monoclonal antibodies (MoAb) labeled with Iodine-131 or Indium-111 (In-111) have been investigated for radioimmunodetection of Hodgkin's and non-Hodgkin's lymphomas. Successful radioimmunotherapy also has been reported. The purpose of this pilot study was to stage non-Hodgkin's B-cell lymphomas (NHL) using whole body scintigraphy with technetium-99m (Tc-99m)-labeled murine monoclonal antibody LL2 (EPB-2) Fab' (Immunomedics, Morris Plains, NJ). Others have shown this MoAb to have specific binding to B-cell lymphomas by flow cytometry and immunofluorescence. Initial clinical studies by others have demonstrated targeting of NHL with the Tc-99m-labeled LL2-Fab'.

METHODS

One milligram of the antibody was injected intravenously after being radiolabeled with 30 mCi Tc-99m. Fifteen patients with high (n = 6), low (n = 2), and intermediate (n = 7) grade NHL were studied. No adverse effects were noted. Planar whole body imaging and single-photon emission computed tomography were performed at 2-6 h and 20-24 h postinjection. Human anti-mouse antibody levels were determined before injection and at 2 and 6 weeks.

RESULTS

In 4 of 15 patients (27%), the disease stage was altered in response to the scintigraphic findings. The physiologic biodistribution of the antibody demonstrated splenic uptake caused by antibody targeting of the white pulp and of normal B-cells, and renal uptake caused by urinary excretion. Lymph node and bone marrow involvement of known tumor sites were clearly seen. A number of previously unknown tumor sites were revealed by LL2-radioimmunodetection despite normal morphologic imaging results. Long-term follow-up of these patients is required to verify these findings. No human anti-mouse antibody elevations or adverse reactions were found in the patients studied.

CONCLUSION

These preliminary data suggest that Tc-99m-labeled LL2 Fab' yields useful clinical results, especially for the staging of patients with NHL before initial therapy or for the detection of early disease recurrence.

Activating anti-idiotypic human anti-mouse antibodies for immunotherapy of ovarian carcinoma

Human anti-mouse antibodies (HAMA) are observed frequently after immunoscintigraphy with monoclonal antibodies (MoAb) directed against CA-125. As the authors have shown previously, HAMA can cause false-positive CA-125 values in routine CA-125 immunoradiometric assay (IRMA) tumor-marker assays (in one case, up to 900 days after immunoscintigraphy). In 32 patients, the authors found a HAMA frequency of 34% (11/32: 3/7 after the first administration, 6/13 after the second, and 2/2 after the third). Ten patients developed extremely high CA-125 levels after undergoing the CIS IRMA assay (up to 80,000 U/ml) in parallel to a significant HAMA increase. The use of different assays, or HAMA removal before in vitro testing, can solve this problem. After a new CA-125 assay containing antibodies that recognize different epitopes on the CA-125 antigen (Biomira Tru-Quant OV) was applied, only mildly increased assay results or normal levels were measured. Most of HAMA-positive patients demonstrated a predominantly anti-idiotypic response, determined with two different HAMA assays. Seven patients with anti-idiotypic HAMA responses after OC-125 immunoscintigraphy remained free of tumor or had stable disease (2-42 or more months), contrary to their poor prognoses that had been made based on the underlying stages of their tumors. All of these patients are currently doing well (Karnofsky Index > 70%) and show no significant tumor progression. In light of their extremely poor prognoses (5-year survival rates of 3-5% in recurrent International Federation of Gynecology and Obstetrics III/IV stages), without further chemotherapy, these courses are extremely unusual. Preliminary in vitro experiments lead to the postulation that anti-idiotypic HAMA may trigger an antitumor effect either by suppressing the growth of CA-125-expressing cancer cells directly, or by activating the patient's immune response via induction of Ab3. Similar results are observed after immunoscintigraphy with a technetium-99m-labeled anti-CA-125 monoclonal antibody (B43.13), which the authors now also use for immunotherapy of ovarian cancer patients by repeated injections, hoping that induction of anti-idiotypic HAMA will be beneficial for prolonged survival of patients with ovarian carcinoma.

[Diagnosis of thrombosis with a murine anti-thrombocyte antibody (99mTc-BW 4): initial clinical results]

The high incidence of deep venous thrombosis requires for successful therapy a timely and accurate diagnosis. We report early clinical results with a 99mTc-labelled anti-platelet antibody (BW 4) for the diagnosis of thrombosis or for studying platelet kinetics. 10 patients were studied of whom 7 were imaged for the detection of thrombi. 3 deep venous thromboses were diagnosed. 3 patients were sent for diagnosing pathological platelet kinetics; 2 demonstrated a markedly changed platelet biodistribution (increased spleen uptake compared to thrombosis patients). The simple and safe handling of the labelling kit enables early studies (within 30 min). The short physical half-life of 99mTc allows a favourable target (thrombus) to non-target (blood-pool) ratio for diagnosis within 2-6 h after injection. Human anti-mouse antibodies were not found in the serum of 4 patients (blood drawn until 4 weeks after administration). There were no side effects.

[Immunoscintigraphy in inflammatory and malignant diseases. anti-leukocyte and anti-tumor antibodies]

Antibody-labelled granulocytes, antigranulocyte antibodies and radiolabelled immunoglobulin can reliably visualize foci of infection; their use in urologic inflammatory disorders is rare. In the diagnosis of urologic tumours anti-CEA immunoscintigraphy of urinary bladder cancer seems to be superior to conventional imaging techniques in sensitivity and specificity. Experience with immunoscintigraphy in non-seminomatous germ cell tumours and prostate cancer are limited; immunoscintigraphy of renal cell cancer is still in the experimental stage in clinical medicine.

[Follow-up after kidney transplantation. Sequential functional scintigraphy with technetium-99m-DTPA or technetium-99m-MAG3]

Complications following renal transplantation are associated with transplant dysfunction; their frequency and the nonspecificity of clinical symptoms underscore the importance of choosing the correct diagnostic procedure. Sequential function scintigraphy with technetium-99m-MAG3 is noninvasive and facilitates the diagnosis of different types of organ rejection, of drug-induced malfunction and of surgical complications.

A novel technetium-99m labeled monoclonal antibody (174H.64) for staging head and neck cancer by immuno-SPECT

A novel murine monoclonal antibody (MAb 174H.64) was labeled with 99mTc by a direct method. MAb 174H.64 detects a cytokeratin-associated antigen which is expressed by over 90% of all squamous cell carcinomas. Panendoscopy, sonography and computerized tomography scan were performed in all cases as well as magnetic resonance imaging (in selected patients). Pre-operative immunoscintigraphy was performed in 21 patients with histologically proven primary carcinomas (18 with remaining primary tumors and 3 with lymph node recurrences). Scintigraphic images were obtained 4-6 h after injection of 1.1 GBq of the 99mTc-labeled antibody (2 mg). Late images were acquired 18 to 24 h after injection. Single-Photon-Emission-Computed Tomography (SPECT) of the head and thorax was performed in all patients. The primary tumors were immunoscintigraphically visualized in all 18 patients with remaining primary tumor. Fifteen of 18 loco-regional lymph node metastases were visualized by immunoscintigraphy (the smallest lesions had a diameter of < 1 cm), in one patient lymph node metastases were detected by immunoscan only. Two metastatically involved lymph nodes were identified by histology only (micrometastases). Distant metastases were present in 3 patients, of which two were identified by immunoscintigraphy. Immuno-SPECT according to this method was a sensitive and specific imaging modality for preoperative staging of patients with squamous cell carcinoma of the head and neck and detected lymph node metastases with higher accuracy than conventional clinical and imaging modalities.

Immunoscintigraphic localization of renal tumours in an extracorporeal perfusion model with a monoclonal antibody against gamma-glutamyltransferase

Monoclonal antibody 138H11 against human gamma-glutamyltransferase has been shown to react immunohistochemically with 98% of all tested clear-cell type and chromophilic renal cell carcinomas, but not with renal chromophobic carcinomas, Duct-Bellini carcinomas or oncocytomas. In normal kidney the target epitopes of mAb 138H11 are located in the luminal brush-border membrane of proximal tubule cells, whereas in renal carcinomas the epitopes are found surrounding the whole tumour cells. These results form the basis of the present immunoscintigraphic study designed to evaluate mAb 138H11 in an extracorporeal perfusion model. Immediately after nephrectomy, human tumour-bearing kidneys were perfused with 99mTc-labelled mAb 138H11 in Euro-Collins solution. High specific uptake in 4/4 renal clear cell carcinomas could be demonstrated by planar immunoscintigraphy and single-photon-emission computed tomography, "regions of interest" investigation and immunohistochemistry. In contrast, a perfused oncocytoma showed up as an unlabelled lesion. The results indicate a possible use for mAb 138H11 in immunoscintigraphy or even therapy, provided high tumour uptake can be confirmed in patients.

Subcutaneous gonadotropin therapy in male patients with hypogonadotropic hypogonadism

OBJECTIVE

The response to subcutaneous (SC) gonadotropin replacement therapy, using human chorionic gonadotropin (hCG) and human menopausal gonadotropin (hMG) or hCG alone, was evaluated in male hypothalamic hypogonadism.

DESIGN

Sixteen patients with hypothalamic hypogonadism were treated with gonadotropins for induction of puberty and normalization of spermatogenesis. The results were analyzed retrospectively.

SETTING

The study was carried out in a clinical endocrinology department providing tertiary care and in private practices of endocrinology.

PATIENTS

Eight patients with idiopathic hypogonadotropic hypogonadism and eight patients with Kallmann's syndrome in prepubertal or early pubertal stages.

INTERVENTIONS

Human chorionic gonadotropin and hMG were administered SC in individual dosages.

MAIN OUTCOME MEASURES

Increase of serum testosterone (T), testicular volume, semen volume, and sperm count were evaluated.

RESULTS

Normalization of serum T and complete sexual maturation was achieved in all patients. Spermatogenesis was induced in all but two patients. Seven patients showed normal findings in semen volume and sperm count, and two patients had semen quality close to normal. In five patients sperm count remained less than 10 x 10(6)/mL.

CONCLUSIONS

The results obtained by SC gonadotropin replacement prove this mode of administration to be effective in stimulating steroidogenesis and spermatogenesis in hypogonadotropic males.

[Experiences with the application of monoclonal Indium-111 antimyosin scintigraphy in the diagnosis of rejection episodes following orthotopic heart transplantation]

Indium-111-labeled Fab fragment imaging using a murine antimyosin monoclonal antibody (Myoscint, Centocor, Leiden) was evaluated for efficacy in detecting cardiac allograft rejection. Diagnosis of rejection was made by endomyocardial biopsy with four to five samples taken for each procedure. Eighty-one studies were performed in 25 patients (21 men, four women, mean age 50 +/- 9 years) from 2 weeks to 45 months after cardiac transplantation. 0.5 mg of the monoclonal antibody labeled with 60 MBq Indium-111 (Antimyosin-Fab-DTPA) was administered i.v. Planar scintigraphic images were obtained in LAO 45 and anterior projections as well as "half-body-scintigrams" 48 h after injection. Using the regions-of-interest-(ROI)technique the relative uptake over the lung and the heart was determined and an index of In-111 uptake was calculated. A heart-to-lung ratio of 1.5 or higher was considered indicative for moderate to severe rejection. Specificity was 86% (nine false-positive In-111 studies in 68 negative biopsy studies), sensitivity was 85% (two false-negative In-111 studies in 13 pathological biopsy studies). It is concluded that the In-111 method has a high sensitivity and specificity in detecting heart transplant rejection and may be useful in the monitoring of patients in the chronic phase after heart transplantation. The 48-h delay in establishing the diagnosis limits the applicability in acute severe rejection.

[Immunoscintigraphy in stomach neoplasms with anti-CEA BW 431/26 monoclonal antibodies marked with Tc 99 m]

A 57 year old female had a tubular gastric adenocarcinoma confirmed by endoscopy and radiologic studies. Echotomography of the abdomen revealed multiple adenopathies. Immunoscintigraphy with 99mTc labeled anti-CEA BW 431/26 monoclonal antibody was performed. Images obtained at 6 and 24 h showed a significant uptake at the primary lesion and at periaortic adenopathies both in conventional gamma-camera and single emission photon tomography. This immuno-scintigraphic technique may be helpful in the management of patients with gastric cancer.