Phase I study of intravenous Lu-labeled CC49 murine monoclonal antibody in patients with advanced adenocarcinoma

CC49, a murine monoclonal antibody that recognizes the tumor-associated glycoprotein 72, was conjugated to the chemical chelate 1,4,7,10-tetraaza-1-(1-carboxy-3-(4-aminophenyl) propyl)-tris-4,7,10- ((carboxy)methyl)cyclododecane that had been labeled with a beta emitter, Lu. Preclinical studies had shown that Lu-labeled CC49 caused regression of human colon adenocarcinoma xenografts in nude mice. Patients with advanced adenocarcinoma who had failed standard treatment and whose tumors expressed the tumor-associated glycoprotein 72 antigen were eligible for treatment to determine the maximum tolerated dose of Lu-labeled CC49. The starting dose of Lu was 10 mCi/m2 given i.v. with the dose of CC49 held constant at 20 mg. Pharmacokinetic sampling and immunoscintigraphy were performed over the ensuing 3 weeks. The dose of radioactive Lu was escalated by 15 mCi/m2 for each successive dose level. Unexpected bone marrow toxicity developed in patients treated at the second dose level with 25 mCi/m2 Lu; two patients developed grade 4 thrombocytopenia, while the third patient developed grade 3 thrombocytopenia. Pharmacokinetic studies showed that the plasma half-life of the immunoconjugate was 67 h; whole-body retention, however, was prolonged with a biological half-life of 258 h. Serial gamma camera imaging localized known tumor in all patients, and also demonstrated prolonged Lu retention in the reticuloendothelial system (RES). Bone marrow dosimetry estimates ranged from 4 to 5 REMS/mCi Lu based on imaging and biopsy data. Analysis of bone marrow biopsies demonstrated that most of the Lu was localized in the cellular compartment and not in the bone. No antitumor responses were observed. Intravenous administration of 15 mCi/m2 Lu-labeled CC49 to previously treated advanced cancer patients was associated with acceptable hematological toxicity and was the maximum tolerated dose. However, prolonged retention of Lu in the RES, including the bone marrow, was observed and limited the dose of Lu that could be given. Additional studies are indicated to reduce RES uptake and retention of this immunoconjugate.     

Intraoperative detection of occult colon cancer micrometastases using 125 I-radiolabled monoclonal antibody CC49

BACKGROUND: The detection of locally-disseminated disease is one of the principal goals of oncologic surgery. For this study, a hand-held, gamma-detecting probe was used intraoperatively to assess the extent of colorectal carcinoma in patients previously injected with radiolabeled antibody to the TAG-72 antigen (CC49); this technique is known as Radioimmunoguided Surgery (RIGS) (Neoprobe Corporation, Dublin, OH). RIGS-positive areas (i.e. those with increased signal over background) have previously been shown to contain carcinoma in a high proportion of cases. However, some RIGS-positive areas had no tumor detectable by clinical examination or routine histopathologic analysis. This study was undertaken to determine if the presence of occult metastases might account for this disparity. METHODS: A total of 57 regional lymph nodes (LN), resected from 16 patients with primary (9) or recurrent (7) colorectal carcinoma, were studied. The patients were injected with 125I labeled CC49 murine monoclonal antibody approximately 3 weeks prior to surgery. After routine histologic evaluation, the LN were analyzed for occult metastases; paraffin sections were cut at 5 levels (50 micron apart) and were examined by histology (hematoxylin and eosin stain [H & E]) and by immunohistochemistry (IHC) with a cocktail of monoclonal antibodies to cytokeratins. RESULTS: Fifty-seven LN were included in this study; 17 were H & E-positive (i.e., contained tumor by routine histologic examination [overt tumor]), while 40 LN were H & E-negative (i.e., no evidence of tumor after routine histologic examination). Thirty-nine LN were RIGS-positive, but only 14 of these were H & E-positive. Of the 25 RIGS-positive/H & E-negative LN, 10 (40%) demonstrated the presence of occult metastases after serial section/IHC analysis. Thus, a total of 27 LN contained metastatic carcinoma (17 overt, 10 occult); routine histologic analysis was able to identify tumor in only 17 of these 27 LN (63%), while the probe signaled the presence of tumor in 24 of these LN (89%). None of the RIGS-negative/H & E-negative LN were found to have occult metastases (0/15). Specific immunoreactivity with CC49 antibody was observed in 5 of 15 RIGS-positive/H & E-negative LN in which no tumor could be identified by any method (histopathology or IHC. CC49 immunoreactivity was not observed in 15 RIGS-negative/H & E-negative LN. CONCLUSIONS: The finding of a RIGS-positive LN had a significant association with the presence of tumor cells (P < 0.05). In this study, the RIGS procedure was more sensitive than clinical or histopathologic examination in detecting the regional spread of a tumor. Furthermore, in LN that showed no evidence of tumor by routine histopathologic examination, a positive RIGS reading was significantly associated with the presence of occult LN metastases (P < 0.01). This study is the first to demonstrate the detection of histologically occult tumor by a remote imaging device. RIGS assessment is a highly sensitive method for detecting occult tumor deposits, and may guide therapeutic intervention in patients with colorectal carcinoma.     

Interferon-gamma and monoclonal antibody 131I-labeled CC49: outcomes in patients with androgen-independent prostate cancer

To assess the tumor targeting, safety, and efficacy of monoclonal antibody 131I-labeled CC49 in patients with androgen-independent prostate cancer, 16 patients received 75 mCi/m2 of the radiolabeled antibody after 7 days of IFN-gamma pretreatment. Sequential tumor biopsies in three patients showed a median 5-fold (range, 2-6-fold) increase in the proportion of cells staining positively for the TAG-72 antigen, whereas one showed a decrease in staining. Fourteen patients received 131I-labeled CC49, whereas 2 showed a disease-related decrease in performance status, precluding antibody treatment. The antibody localized to sites of metastatic androgen-independent prostate cancer in 86% (12 of 14; 95% confidence interval, 57-95%) of cases. Both osseous and extraosseous sites were visualized, and in six (42%) patients, more areas were visible when the radioimmunoconjugate was used than were apparent when conventional scanning techniques were used. The localization of the conjugate in the marrow cavity was usually a site not visualized by the radionuclide bone scan, in which the isotope localizes primarily to the tumor-bone interface. The dose-limiting toxicity was thrombocytopenia because five (36%) patients showed grade IV and seven (50%) showed grade III effects. In addition, six (42%) patients, four of whom were hospitalized, showed a flare in baseline pain, and four showed a decrease in pain. No patient showed a >50% decline in prostate-specific antigen, although radionuclide bone scans remained stable in four cases for a median of 4 months. The results are consistent with dosimetry estimates showing that the delivered dose to tumor was subtherapeutic and suggest that approaches that exclusively target the bone tumor interface or the marrow stroma may be unable to completely eradicate disease in the marrow cavity. For CC49, improving outcomes would require repetitive dosing, which was precluded by the rapid development of a human antimouse antibody response.     

The effects of local hyperthermia on the catabolism of a radioiodinated chimeric monoclonal antibody

Local hyperthermia has been shown to increase the tumor uptake and tumor:normal tissue ratios of radiolabeled monoclonal antibodies (mAbs) in athymic mouse xenograft models. The current study was undertaken to determine whether this behavior was related in part to alterations in mAb catabolism by local hyperthermia. Human/mouse chimeric 81C6 mAb reactive with tenascin and a nonspecific control mAb were labeled with 125I using Iodo-Gen and given to separate groups of athymic mice bearing s.c. D-54 MG human glioma xenografts. Half of the animals were then subjected to 4-h tumor-localized hyperthermia at 41.8 degrees C, a protocol previously shown to enhance the specific tumor uptake of the mAb in this xenograft model. The tumor, serum, liver, kidney, and urine were collected from heated as well as control animals 4 and 24 h after injection of the mAb and analyzed by SDS-PAGE and trichloroacetic acid precipitation. At 24 h, a significantly higher percentage of 81C6 was present as intact mAb in the tumors harvested from heated animals compared with those from controls. Unexpectedly, intact mAb was found in the urine of mice immediately after hyperthermia, but not in unheated control animals. We conclude that local hyperthermia decreases the catabolism of the mAb in the tumor and increases the urinary excretion of the mAb through a transient increase in glomerular permeability.     

Rapid analytical tryptic mapping of a recombinant chimeric monoclonal antibody and method validation challenges

A rapid and reproducible analytical tryptic mapping method was developed as an identity test for a recombinant chimeric monoclonal antibody for lot release testing. The unfolding, reduction, carboxymethylation, trypsin digestion, and reversed-phase (RP) HPLC steps were optimized to provide a reproducible method. The optimized method requires 30 min for unfolding the protein, 30 min for carboxymethylation, 4 h for digestion with TPCK-trypsin and 140 min for RPHPLC analysis. The total time required is less than 8 h compared to conventional procedures, which must be performed over several days. The optimized method was validated for its precision, recovery, specificity, and robustness. The precision of the method was determined by repeatability and intermediate precision experiments. Relative standard deviation (RSD) values were < or = 10% for the relative peak areas of marker peaks. The mean recovery of these marker peaks was 88.4%. The specificity was demonstrated by the unique tryptic mapping patterns obtained compared with several other monoclonal antibodies. Robustness was demonstrated by the relative insensitivity of the tryptic map to small deliberate changes in key method parameters. Excessive relative peak area variability observed for one peak (RSD 52%) was traced to adsorption to glass autosampler vials. This variability was substantially reduced (RSD 11%) by substituting polypropylene autosampler vials. The data demonstrate that this method may be applicable to a wide range of pharmaceutically relevant monoclonal antibodies.     

Radioimmunotherapy of orthotopically transplanted pancreatic cancer with 131I-labeled chimeric monoclonal antibody Nd2

Recent study demonstrated high susceptibility of plasma LDL to lipid peroxidative modification in patients with variant angina. Oxidized stress state, especially oxidized LDL, may induce coronary artery spasm by its impairing effect of endothelium-dependent arterial relaxation, but precise mechanisms remain unclear. Study subjects included 93 patients who underwent coronary angiographic examination: 12 patients with coronary artery spasm provoked by ergonovine without organic stenosis (group I), 11 patients who did not demonstrate coronary artery spasm or organic stenosis (group II) and 70 patients with organic coronary artery stenosis (group III). Levels of plasma HDL-cholesterol and apoA-I in group I were similar to those in III but were significantly lower than those in II, although the other plasma lipid parameters were not different among the three groups. The levels of TBARS in plasma and HDL were significantly higher in group I than in II or III (2.94+/-1.56 vs. 1.91+/-0.35 or 2.23+/-0.89 nmol MDA/ml and 1.23+/-1.00 vs. 0.54+/-0.37 or 0.70+/-0.63 nmol MDA/mg protein; P < 0.05), although the levels of TBARS in LDL were not significantly different. In the monitoring curve of diene production during copper-induced lipid peroxidation of HDL, its propagation slope was steeper and levels of maximum diene absorbance was higher in group I as compared with that in II or III, but not found in those of LDL. These results suggested that high susceptibility of HDL to lipid peroxidative modification in group I may contribute to the genesis of coronary artery spasm, and oxidized HDL rather than oxidized LDL is more likely to be related to coronary artery spasm.     

Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20

Murine monoclonal antibody 2B8 specifically recognizes the CD20 phosphoprotein expressed on the surface of normal B lymphocytes and B-cell lymphomas. The light- and heavy-chain variable regions of 2B8 were cloned, after amplification by the polymerase chain reaction, into a cDNA expression vector that contained human IgG1 heavy chain and human kappa-light chain constant regions. High-level expression of chimeric-2B8 antibody (C2B8) was obtained in Chinese hamster ovary cells. Purified C2B8 exhibited antigen binding affinity and human-tissue reactivity similar to the native murine antibody. In vitro studies showed the ability of C2B8 to bind human C1q, mediate complement-dependent cell lysis of human B-lymphoid cell lines, and lyse human target cells through antibody-dependent cellular cytotoxicity. Infusion of macaque cynomolgus monkeys with doses ranging from 1.6 mg/kg to 6.4 mg/kg resulted in greater than 98% depletion of peripheral blood (PB) B cells and 40% to 70% depletion of lymph node B cells. Recovery of PB B cells usually started at 2 weeks after treatment and required 60 to greater than 90 days to reach normal levels. As much as 95% depletion of B cells in peripheral lymph nodes and bone marrow was observed following weekly injections of 16.8 mg/kg antibody. No toxicity was observed in any of the animals. These results offer the possibility of using an "immunologically active" chimeric anti-CD20 antibody as an alternative approach in the treatment of B-cell lymphoma.     

Characterization of two monoclonal antibodies against the RON tyrosine kinase receptor

An anthropometric assessment was conducted at 238 !Kung San hunter-gatherers aged between 18 and 65 years (mean = 30.8 years), 156 Kavango horticultural pastoralists aged between 18 and 61 years (mean = 29.2 years) and for 87 urbanized Kavango people aged between 18 and 61 years (mean = 29.3 years) living as wage earning employees in northern Namibia. Weight status was estimated by using body mass index categories according to the recommendations of the WHO. As is typical for human populations, men were taller and heavier than women within the same ethnic groups. An interethnic comparison showed that both !Kung San women and men were lighter than Kavango women and men. The mean BMI of !Kung San women was 19.1 and of !Kung San men 19.4 kg/m2. Kavango people exhibited higher average BMI values, 19.4 for women, 20.3 kg/m2 for men. With the exception of the male urban Kavango people a high percentage (more than 30%) of the subjects were thin and underweight, as shown by a BMI of < 18.5 kg/m2. This was especially true of the !Kung San of both sexes and the rural Kavango men. Nearly 25% of !Kung San women met the criterion of weight depletion (BMI < 17.0). The cultural transition from nomadic hunter gatherer subsistence to a more sedentary life style over the last 20 years can be interpreted as an environmental stress which affected male as well as female nutritional status. The hard economic situation of the rural Kavango people may also be a stress factor which negatively influenced their nutritional status, especially of the men. The significantly better nutritional status of the urban Kavango men may be the result of the opportunities for work as wage earners or as soldiers.     

In vitro and in vivo behavior of radiolabeled chimeric anti-EGFRvIII monoclonal antibody: comparison with its murine parent

The mutant version of the epidermal growth factor receptor EGFRvIII has been found on gliomas and other tumors, but not on normal tissues. Radioiodinated murine (mu) L8A4 monoclonal antibody (MAb) specifically targets EGFRvIII xenografts in vivo when labeled using N-succinimidyl 5-iodo-3-pyridinecarboxylate (SIPC). A chimeric (ch) MAb consisting of the variable region of muL8A4 and the constant domains of human IgG2 has been developed that has an affinity and radioiodinated immunoreactive fraction comparable to muL8A4. In vitro, both MAbs were internalized and processed by EGFRvIII expressing cell lines (U87MG delta EGFR or NR6M) at similar rates (maximum intracellular retention, 35-40%). In paired-label tissue distribution studies in athymic mice bearing U87MG delta EGFR tumor xenografts, the ch:mu L8A4 uptake ratio in normal tissues rose to greater than 2:1, whereas in tumor, the ratio remained 1:1 throughout the experiment. These results indicate that chL8A4 exhibits similar binding and internalization properties as its murine parent, but suggest different intracellular processing and/or deposition of catabolites in normal tissues for chL8A4.     

Definition of essential amino acid residues in the recognition of a peptide by a mouse monoclonal antibody

A mouse monoclonal antibody reacting in ELISA with a synthetic peptide representing a linear amino acid stretch of the protein antigen was tested on all overlapping 5-mer to 9-mer fragments of the peptide, as prepared by multi-pin synthesis. Analysis of the binding data suggests that several residues in the peptide might be relatively unrelevant for recognition, while few others seem to play a critical role as key residues. On the basis of such observations, we attempted to reconstruct an alternative essential epitope by introducing multiple amino acid substitutions in the 9-mer peptide exhibiting the best binding activity, and then tested its ability to be recognized by the monoclonal antibody.     

Dose escalation trial of indium-111-labeled anti-carcinoembryonic antigen chimeric monoclonal antibody (chimeric T84.66) in presurgical colorectal cancer patients

Chimeric T84.66 (cT84.66) is a high-affinity (1.16x10(11) M(-1)) IgG1 monoclonal antibody against carcinoembryonic antigen (CEA). The purpose of this pilot trial was to evaluate the tumor-targeting properties, biodistribution, pharmacokinetics and immunogenicity of 111In-labeled cT84.66 as a function of administered antibody protein dose. METHODS: Patients with CEA-producing colorectal cancers with localized disease or limited metastatic disease who were scheduled to undergo definitive surgical resection were each administered a single intravenous dose of 5 mg of isothiocyanatobenzyl diethylenetriaminepentaacetic acid-cT84.66, labeled with 5 mCi of 111In. Before receiving the radiolabeled antibody, patients received unlabeled diethylenetriaminepentaacetic acid-cT84.66. The amount of unlabeled antibody was 0, 20 or 100 mg, with five patients at each level. Serial blood samples, 24-hr urine collections and nuclear images were collected until 7 days postinfusion. Human antichimeric antibody response was assessed up to 6 mo postinfusion. RESULTS: Imaging of at least one known tumor site was performed in all 15 patients. Fifty-two lesions were analyzed, with an imaging sensitivity rate of 50.0% and a positive predictive value of 76.9%. The antibody detected tumors that were not detected by conventional means in three patients, resulting in a modification of surgical management. Interpatient variations in serum clearance rates were observed and were secondary to differences in clearance and metabolic rates of antibody and antibody:antigen complexes by the liver. Antibody uptake in primary tumors, metastatic sites and regional metastatic lymph nodes ranged from 0.4% to 134% injected dose/kg, resulting in estimated 90Y-cT84.66 radiation doses ranging from 0.3 to 193 cGy/mCi. Thirteen patients were evaluated 1-6 mo after infusion for human antichimeric antibody, and none developed a response. No major differences in tumor imaging, tumor uptake, pharmacokinetics or organ biodistribution were observed with increasing protein doses, although a trend toward increasing blood uptake and decreasing liver uptake was observed with increasing protein dose. CONCLUSION: Chimeric T84.66 demonstrated tumor targeting comparable to other radiolabeled intact anti-CEA monoclonal antibodies. Its immunogenicity after single administration was lower than murine monoclonal antibodies. These properties make 111In-cT84.66, or a lower molecular weight derivative, attractive for further evaluation as an imaging agent. Yttrium-90 dosimetry estimates predict potentially cytotoxic radiation doses to select tumor sites, which makes 90Y-cT84.66 also appropriate for further evaluation in Phase I radioimmunotherapy trials. Although clinically important changes in biodistribution, pharmacokinetics and tumor targeting with increasing protein doses of 111In-cT84.66 were not demonstrated, the results do suggest that antibody clearance from the blood is driven by hepatic uptake and metabolism, with more rapid blood clearance seen in patients with liver metastases. These patients with rapid clearance and potentially unfavorable biodistribution for imaging and therapy may, therefore, be a more appropriate subset in which to evaluate the role of administering higher protein doses. This underscores the need to further identify, characterize and understand those factors that influence the biodistribution and clearance of radiolabeled anti-CEA antibodies, to allow for better selection of patients for therapy and rational planning of radioimmunotherapy.     

A novel monoclonal antibody permitting recognition of NKT cells in various mouse strains

OBJECTIVES: The purpose of this study was to determine whether restrictive left ventricular (LV) filling patterns are associated with diastolic ventricular interaction in patients with chronic heart failure. BACKGROUND: We recently demonstrated a diastolic ventricular interaction in approximately 50% of a series of patients with chronic heart failure, as evidenced by paradoxic increases in LV end-diastolic volume despite reductions in right ventricular end-diastolic volume during volume unloading achieved by lower body negative pressure (LBNP). We reasoned that such an interaction would impede LV filling in mid and late diastole, but would be minimal in early diastole, resulting in a restrictive LV filling pattern. METHODS: Transmitral flow was assessed using pulsed wave Doppler echocardiography in 30 patients with chronic heart failure and an LV ejection fraction < or = 35%. Peak early (E) and atrial (A) filling velocities and E wave deceleration time were measured. Left ventricular end-diastolic volume was measured using radionuclide ventriculography before and during -30-mm Hg LBNP. RESULTS: Nine of the 11 patients with and 2 of the 16 patients without restrictive LV filling patterns (E/A > 2 or E/A 1 to 2 and E wave deceleration time < or = 140 ms) increased LV end-diastolic volume during LBNP (p = 0.001). The change in LV end-diastolic volume during LBNP was correlated with the baseline A wave velocity (r = -0.52, p = 0.005) and E/A ratio (r = 0.50, p = 0.01). CONCLUSIONS: Restrictive LV filling patterns are associated with diastolic ventricular interaction in patients with chronic heart failure. Volume unloading in the setting of diastolic ventricular interaction allows for increased LV filling. Identifying patients with chronic heart failure and restrictive filling patterns may therefore indicate a group likely to benefit from additional vasodilator therapy.     

Use of conformationally constrained peptides for a topographical analysis of the combing site of a monoclonal anti-substance P antibody

We studied the trends from 1969 to the mid-1980s in the incidence and mortality of acute myocardial infarction and stroke in Swedish women residing in the Uppsala Health Care Region. We used data from the Inpatient Care and Causes of Death registers to obtain total first event incidence and mortality rates. In our population, there were 20,182 acute myocardial infarctions and 30,462 stroke events, and 17,359 and 21,336 deaths, respectively. We found an average overall annual increase of 1.3% in the age-standardized incidence of acute myocardial infarction during the 1970s, followed by decreasing rates during the early 1980s. Mortality was virtually unchanged. Notably, among women 45-49 years of age, we observed a rising trend during the whole period, whereas in the oldest age groups, the increase slowed and reversed in the latter years. Both the incidence and mortality for stroke declined steadily: the age-standardized incidence fell by an average of 2.1% per year for all stroke and 7.8% for intracerebral hemorrhage. The falling rate of stroke was best explained by birth cohort effects, with a 30% reduction in women born in 1920 and later as compared with those born in 1890. We conclude that important changes in Swedish women's cardiovascular health have taken place and that increasing cigarette smoking and hypertensive treatment are major determinants.     

Rituximab chimeric anti-CD20 monoclonal antibody therapy for relapsed indolent lymphoma: half of patients respond to a four-dose treatment program

PURPOSE: The CD20 antigen is expressed on more than 90% of B-cell lymphomas. It is appealing for targeted therapy, because it does not shed or modulate. A chimeric monoclonal antibody more effectively mediates host effector functions and is itself less immunogenic than are murine antibodies. PATIENTS AND METHODS: This was a multiinstitutional trial of the chimeric anti-CD20 antibody, IDEC-C2B8. Patients with relapsed low grade or follicular lymphoma received an outpatient treatment course of IDEC-C2B8 375 mg/m2 intravenously weekly for four doses. RESULTS: From 31 centers, 166 patients were entered. Of this intent-to-treat group, 48% responded. With a median follow-up duration of 11.8 months, the projected median time to progression for responders is 13.0 months. Serum antibody levels were sustained longer after the fourth infusion than after the first, and were higher in responders and in patients with lower tumor burden. The majority of adverse events occurred during the first infusion and were grade 1 or 2; fever and chills were the most common events. Only 12% of patients had grade 3 and 3% grade 4 toxicities. A human antichimeric antibody was detected in only one patient. CONCLUSION: The response rate of 48% with IDEC-C2B8 is comparable to results with single-agent cytotoxic chemotherapy. Toxicity was mild. Attention needs to be paid to the rate of antibody infusion, with titration according to toxicity. Further investigation of this agent is warranted, including its use in conjunction with standard chemotherapy.     

Radioimmunotherapy with a 64Cu-labeled monoclonal antibody: a comparison with 67Cu

67Cu (t1/2 = 62 h) has demonstrated potential as a radionuclide for radioimmunotherapy, but limited availability severely restricts its widespread use. 64Cu (t1/2 = 12.8 h) has been shown to have comparable effectiveness in vitro and in vivo. The present study was undertaken to examine the therapeutic potential of 64Cu- and 67Cu-bromoacetamidobenzyl-1,4,8,11-tetraazacyclotetradeca ne-N, N',N",N"'-tetraacetic acid (BAT)-2-iminothiolane (2IT)-1A3 (1A3 is a mouse anti-human colorectal cancer mAb) for treatment of GW39 human colon carcinoma carried in hamster thighs. Hamsters were injected with 64Cu- or 67Cu-BAT-2IT-1A3 or Cu-labeled nonspecific IgG (MOPC) or saline. Hamsters were killed 6-7 months after therapy or when tumors were > or = 10 g. Of the hamsters with small tumors (mean weight 0.43 +/- 0.25 g), 87.5% were disease-free 7 months after treatment with 2 mCi (1 Ci = 37 GBq) of 64Cu-BAT-2IT-1A3 or 0.4 MCi of 67Cu-BAT-2IT-1A3. The mean tumor doses at these activities of 64Cu- and 67Cu-BAT-2IT-1A3 were 586 and 1269 rad (1 rad = 0.01 Gy), respectively. In contrast, 76% of hamsters treated with 2 mCi of 64Cu-BAT-2IT-MOPC or 0.4 mCi of 67Cu-BAT-2IT-MOPC had to be killed before 6 months because of tumor regrowth. When hamsters with larger tumors (mean weight 0.66 +/- 0.11 g) were treated with 64Cu- or 67Cu-BAT-2IT-1A3, survival was extended compared with controls, but only one animal remained tumor-free to 6 months. These results demonstrate that 64Cu- and 67Cu-BAT-2IT-1A3 given in a single administered dose can eradicate small tumors without significant host toxicity, but additional strategies to deliver higher tumor doses will be needed for larger tumors.     

Thrombolytic and pharmacokinetic properties of a recombinant chimeric plasminogen activator consisting of a fibrin fragment D-dimer specific humanized monoclonal antibody and a truncated single-chain urokinase

A recombinant chimeric plasminogen activator consisting of a humanized monoclonal antibody specific for cross-linked human fibrin (MA-15C5Hu) and a 32 kDa single-chain urokinase-type plasminogen activator (scu-PA-32k) comprising amino acids Leu144-Leu411, MA-15C5Hu/scu-PA-32k, was previously found to have a 12-fold higher fibrinolytic potency than recombinant scu-PA-32k towards a human plasma clot in a human plasma milieu in vitro (Vandamme et al., Eur J Biochem 1992; 205: 139-46). Therefore, the thrombolytic and pharmacokinetic properties of MA-15C5Hu/scu-PA-32k were compared with those of recombinant single-chain urokinase-type plasminogen activator (scu-PA) in 3 different venous thrombosis models in vivo. In hamsters with a pulmonary embolus consisting of a human plasma clot, the thrombolytic potency (% lysis per dose in mg/kg administered) of MA-15C5Hu/scu-PA-32k was 23-fold higher than that of scu-PA (p less than 0.0005). In rabbits with a jugular vein clot prepared from human plasma, the thrombolytic potency of MA-15C5Hu/scu-PA-32k was 11-fold higher than that of scu-PA (p = 0.012). In baboons with an autologous whole blood clot in the femoral vein, the chimera had a 5-fold higher thrombolytic potency than scu-PA. In all three animal species, the clearance of the chimera was 10- to 27-fold reduced as compared to scu-PA. The specific thrombolytic activity (% lysis per micrograms/ml steady-state plasma u-PA antigen) was increased up to 7-fold with MA-15C5Hu/scu-PA-32k as compared with scu-PA, which is indicative of targeting of the chimera to the clot. No fibrinogen breakdown or alpha 2-antiplasmin depletion was observed during thrombolysis with the chimera. Thus, MA-15C5Hu/scu-PA-32k constitutes a recombinant chimeric plasminogen activator with a significantly enhanced thrombolytic potency in 3 different animal models of venous thrombosis.     

Inhibition of interleukin-5 with a monoclonal antibody attenuates allergic inflammation

IL-5 is a prominent and perhaps an essential element in the induction of allergic inflammation in human asthma and other allergic diseases. Despite the strong biochemical and clinical correlates between lung eosinophilia and asthma, there is no clear understanding of how eosinophils exacerbate asthma. Antigen administration to sensitized animals produces eosinophilic infiltration that is very similar to that in man, and is prevented by administration of a neutralizing monoclonal antibody against IL-5. Mice in which the IL-5 gene is absent are unable to mount eosinophilic responses to antigen and do not sustain lung damage, but otherwise develop normally. The study of the biology of IL-5 has not only clarified the links between eosinophilia and airway hyperreactivity, but also strongly suggests that anti-IL-5 therapy may be an effective, safe, and novel way of treating human asthma and perhaps other eosinophilic diseases. There are many different potential approaches to the inhibition of IL-5, but the one most likely to provide "proof of principle" in "asthma in the wild" in man is a monoclonal antibody against IL-5.     

Dosimetric analysis of chimeric monoclonal antibody cMOv18 IgG in ovarian carcinoma patients after intraperitoneal and intravenous administration

In this study the potential of intraperitoneal (i.p.) and intravenous (i.v.) administration of chimeric iodine-131-labelled MOv18 IgG for radioimmunotherapy was determined. The dosimetry associated with both routes of administration of cMOv18 IgG was studied in patients. Eight patients suspected of having ovarian carcinoma received 150 MBq 131I-cMOv18 IgG i.p. Blood and urine were collected and serial gamma camera images were acquired. Another group of four patients received 7.5 MBq 131I-cMOv18 IgG i.v. For all patients, tissue biopsies were obtained at surgery. Activity in the blood after i.p. administration was described by a bi-exponential curve with a mean uptake and elimination half-life of 6.9+/-3.2 h and 160+/-45 h, respectively. For i.v. infusion the mean half-life for the elimination phase was 103+/-12 h. Cumulative excretion in the urine was 17%+/-3% ID and 21%+/-7% ID in 96 h for i.p. and i.v. administration, respectively. Scintigraphic images after i.p. administration showed accumulation in ovarian cancer lesions, while all other tissues showed decreasing activity with time. Tumour uptake determined in the ovarian cancer tissue specimens ranged from 3.4% to 12.3% ID/kg for i.p. administration and from 3.6% to 5.4% ID/kg for i.v. administration. Dosimetric analysis of the data indicated that 1.7-4.3 mGy/MBq and 1.7-2.2 mGy/MBq can be guided to solid or ascites cells after i.p. and i.v. administration, respectively. Assuming that an absorbed dose to the bone marrow of 2 Gy will be dose limiting, a total activity of 4.1 GBq 131I-cMOv18 IgG can be administered safely via the i.p. route and 3.5 GBq via the i.v. route. At this maximal tolerated dose, a maximum absorbed dose to 1-g tumours in the peritoneal cavity of 18 and 8 Gy can be reached after i.p. and i.v. administration, respectively. For the i. p. route of administration, dose estimates for the tumour are even higher when the electron dose of the peritoneal activity is also taken into account: total doses to the tumour of 30 Gy and 22 Gy will be absorbed at the tumour surface and at 0.2 mm depth, respectively. In conclusion, therapeutic tumour doses can be achieved with 131I-cMOv18 IgG in patients with intraperitoneal ovarian cancer lesions with no normal organ toxicity. The i.p. route of administration seems to be preferable to i.v. administration.