90Yttrium-labeled complementarity-determining-region-grafted monoclonal antibodies for radioimmunotherapy: radiolabeling and animal biodistribution studies

90Yttrium-labeled monoclonal antibodies (mAbs) are likely to be important to radioimmunotherapy (RAIT) of a variety of cancers. The goal of this study was to select and evaluate a form of [90Y]mAb suitable for RAIT and determine conditions for high-yield, reproducible radiolabelings. 90Y-Labelings, at 2-40 mCi levels, of cdr-grafted versions of anti-B-cell lymphoma (hLL2) and anti-CEA (hIMMU-14) mAbs were optimized to >90% incorporations using the macrocyclic chelator DOTA as the metal carrier. In in vitro challenge assays, the stability of mAbs labeled with [90Y]DOTA was better than that of the corresponding [90Y]benzyl-DTPA conjugates. The retention of [90Y]DOTA-hLL2 on Raji tumor cells in vitro was similar to that of the same mAb labeled with [90Y]benzyl-DTPA and was about twice as much as with [125I]hLL2, indicating residualization of metalated mAb. Both [90Y]hLL2 conjugates, prepared using DOTA and Bz-DTPA, had similar maximum tolerated doses of 125 muCi in BALB/c mice and showed no discernible chelator-induced immune responses. Animal biodistribution studies in nude mice bearing Ramos human B-cell lymphoma xenografts revealed similar tumor and tissue uptake over a 10 day period, with the exception of bone uptake which was up to 50% lower for [88Y]DOTA-hLL2 compared to [88Y]Bz-DTPA-hLL2 at time points beyond 24 h. With [90Y]DOTA-hLL2 fragments, in vivo animal tumor dosimetries were inferior to those for the IgG, and kidney uptake was relatively high even with D-lysine administration. The ability of [111In]DOTA-hLL2 to accurately predict [90Y]DOTA-hLL2 biodistribution was established. These preclinical findings demonstrate that [90Y]DOTA-(CDR-grafted) mAbs are suitable for examination in clinical RAIT.

Intracellular processing of 99Tcm-antibody conjugates

The catabolism of 99Tcm-antibody conjugates after internalization by B-cell lymphomas was investigated, using antibody LL1, an antibody to the MHC class II invariant chain which is internalized and catabolized very rapidly. Intact IgG antibodies were labelled with 99Tcm after mild reduction. The 99Tcm label was strongly retained within cells, similar to 'residualizing' labels such as 111In-diethylenetriamine pentaacetate (111In-DTPA), but different from a conventional iodine label. Unlike 111In-DTPA, 99Tcm was not retained in a low molecular weight form, but instead was found to be bound to a large number of different cellular proteins, and was retained in the cytoplasm rather than in lysosomes. Therefore, this form of 99Tcm represents a new paradigm of intracellular retention of a radiolabel.

Cu uptake, metabolism and elimination in fed and starved European eels (Anguilla anguilla) during adaptation to water-borne Cu exposure

64Cu accumulation and total Cu concentrations were measured in gill filaments, plasma, liver and bile of fed and starved European eels (Anguilla anguilla) during 28 days of exposure to 12 and 94 micrograms Cu l-1. Branchial Cu uptake was found to be 0.03 and 0.13 microgram Cu g gill filament-1 h-1 at 12 and 94 micrograms Cu l-1, respectively, throughout 28 days of Cu exposure. At least during exposure to 94 micrograms Cu l-1, the basolateral membrane seemed to be the rate limiting step for branchial Cu uptake. The plasma accounted for at least 70% of the 64Cu labelled Cu present in the blood at both Cu concentrations. The plasma Cu concentration was gradually increased from 0.64 to 1.92 and 2.68 micrograms ml-1 during the first 6 days of Cu exposure; it was partly normalized to 1.07 and 1.45 micrograms ml-1 after 28 days of exposure to 12 and 94 micrograms Cu l-1, respectively, despite a constant branchial Cu uptake, indicating an increased turnover of plasma Cu. The hepatic accumulation of 64Cu was similar in fed and starved eels (0.55 microgram Cu g liver-1 h-1) at both Cu concentrations during the 28 days of exposure. The hepatic total Cu concentrations were lower in the fed fish compared to the starved fish and increased only marginally from 3 to 28 days of exposure indicating a high turnover of hepatic Cu during acclimation. Hepatic Cu elimination, measured as 64Cu in the bile, was highest in the fed fish at the highest Cu concentration and was stimulated during acclimation at least in the starved fish.

Carbohydrates engineered at antibody constant domains can be used for site-specific conjugation of drugs and chelates

To improve the efficiency of site-specific conjugation of chelates and drugs to antibodies, and to minimize the incidence of immunoreactivity perturbation to the resultant immunoconjugates, Asn-linked oligosaccharide moieties were designed and engineered into the constant domains of a humanized anti-CD22 monoclonal antibody, hLL2. From 10 potential glycosylation mutants, two CH1 domain glycosylation sites, HCN1 and HCN5, were identified that were positioned favorably for glycosylation. The carbohydrate (CHO) chains attached at these sites were differentially processed so that HCN5-CHOs were physically larger than HCN1-CHOs. Although both the CH1-appended CHOs, and the LL2 Vkappa-appended CHOs conjugated efficiently with small chelates, the HCN5-CHOs, due to the structural and positional superiority, appear to be a better conjugation site for large drug complexes, such as 18 kDa doxorubicin (DOX)-dextran.

Generation of a high-producing clone of a humanized anti-B-cell lymphoma monoclonal antibody (hLL2)

BACKGROUND

LL2 is a murine immunoglobulin (Ig)G2a-kappa anti-B-cell monoclonal antibody with proven targeting and therapeutic efficacy in the management of non-Hodgkin's lymphoma (NHL). The authors had previously generated a humanized LL2 (hLL2) that demonstrated binding properties identical to those of LL2. Nevertheless, the productivity of the cell line was insufficient for large-scale production of the antibody for clinical studies. Therefore, the authors chose an amplifiable system for the generation of hLL2.

METHODS

The hLL2 sequences were ligated into the expression vector pdHL2, which has a dhfr amplifiable gene, and were incorporated into the SP2/0 cells by electroporation. A methotrexate (MTX) resistant clone producing hLL2 was identified. Stepwise increases in MTX concentrations, from 0.1 to 5 microM, and subcloning of the cells by limiting dilution were performed.

RESULTS

By amplifying the dhfr and hLL2 genes with stepwise increases in the MTX concentration, the antibody production was enhanced from its original 1.4 to 70 +/- 5 mg per liter of culture media. Subsequent subcloning further improved the productivity. Immunoreactivity of the antibody was conserved, as proven by enzyme-linked immunosorbent assay and cell-binding assays. By isoelectrofocusing, the isoelectric point (pI) of the antibody was measured at approximately 9.6. The productivity of the clone was not affected by culture conditions or storage of the cells in liquid nitrogen.

CONCLUSIONS

By means of gene amplification, the authors have generated a high-producing hLL2-IgG clone suitable for production of the quantity of antibody necessary for clinical diagnostic and therapeutic trials of NHL patients.

Chimerization of Mu-9: a colon-specific antigen-p antibody reactive with gastrointestinal carcinomas

BACKGROUND

Mu-9 is a murine monoclonal antibody that is directed against affinity-purified colon-specific antigen-p (CSAp). CSAp is a tumor-associated antigen that is present in 60% of colorectal carcinomas. Preclinical and clinical studies have shown Mu-9 to have excellent targeting abilities. However, as administration of the murine immunoglobulin G (IgG) provoked a human anti-mouse antibody response, chimerization of Mu-9 is warranted for decreasing immunogenicity.

METHODS

Polymerase chain reaction and cDNA library screening methods were used for the cloning of Mu-9 heavy and light chain variable regions for the construction of chimeric Mu-9.

RESULTS

The functional chimeric Mu-9 antibody binds to the CSAp antigen in the GW-39 extracts. It has immunochemical properties similar to that of murine Mu-9.

CONCLUSIONS

The V-region sequence information will be used for design of humanized Mu-9, which will be evaluated for targeting gastrointestinal carcinomas.

Structure determination of N-linked oligosaccharides engineered at the CH1 domain of humanized LL2

Two humanized antibody mutants, hLL2HCN1 and hLL2HCN5, engineered with CH1 domain-appended carbohydrates (CHOs) were generated to facilitate site-specific conjugation of radionuclides and anti-cancer drugs to antibodies. Such site-specific conjugation may minimize the incidence of immunoreactivity perturbation as is often observed with random conjugation. Since the compositions and structures of CHOs are important in determining the chemistry, efficiency, and extent of conjugation, the sequences of the CH1-appended CHOs were determined by exoglycosidase digestions and fluorophore-assisted CHO electrophoresis (FACE). The CHO species attached at HCN1 and HCN5 sites in hLL2HCN1 and hLL2HCN5, respectively, were distinct from each other, heterogeneous, and extensively processed. All of these CHOs were core-fucosylated complex-type oligosaccharides and contained Gal (galactose) and GlcNAc (N-acetylglucosamine) residues in the outer branches. Some of the outer branches were composed of Gal alpha1-3Galbeta1-4GlcNAc structure, also known as alpha-galactosyl epitope. Most of the CHOs were sialylated. While all HCN1-CHOs were biantennary, the majority of HCN5-CHOs (>60%) were triantennary. The CH1-appended CHOs have favorable structural characteristics suitable for site-specific conjugation. For efficient conjugation of large drug complexes, hLL2HCN5 is preferable to hLL2HCN1 because the attached CHO is larger in size and more remotely positioned from the V region. The effects of the alpha-galactosyl epitope found in these CHOs on the immunological properties of the immunoconjugates as efficient cancer diagnostics and therapeutics are being studied.

Development of a streptavidin-anti-carcinoembryonic antigen antibody, radiolabeled biotin pretargeting method for radioimmunotherapy of colorectal cancer. Studies in a human colon cancer xenograft model

Pretargeting methodologies can produce high tumor:blood ratios, but their role in cancer radioimmunotherapy (RAIT) is uncertain. A pretargeting method was developed using a streptavidin (StAv) conjugate of MN-14 IgG, an anti-carcinoembryonic antigen (CEA) murine monoclonal antibody (mab) as the primary targeting agent, an anti-idiotype antibody (WI2 IgG) as a clearing agent, and DTPA- or DOTA-conjugated biotin as the radiolabeled targeting agent. A variety of reagents and conditions were examined to optimize this method. At 3 h, 111In-DTPA-peptide-biotin tumor uptake was 3.9 +/- 0.8% per gram and tumor:blood ratios were > 11:1. By 24 h, this ratio was 178:1, but tumor accretion declined in accordance with the gradual loss of StAv-MN-14 from the tumor. Tissue retention was highest in the liver and kidneys, but their tumor:organ ratios were > 2:1. Dosimetry predicted that radiolabeled MN-14 alone would deliver higher tumor doses than this pretargeting method. Increasing the specific activity and using DOTA-biotin in place of DTPA increased tumor uptake nearly 2-fold, but analysis of StAv-MN-14's biotin-binding capacity indicated over 90% of the initial biotin-binding sites were blocked within 24 h. Animals fed a biotin-deficient diet had 2-fold higher 111In-DOTA-biotin uptake in the tumor, but higher uptake also was observed in all normal tissues. Although exceptionally adept at achieving high tumor:blood ratios rapidly, the tumor uptake of radiolabeled biotin with this pretargeting method is significantly (p < 0.0001) lower than that with a radiolabeled antibody. Endogenous biotin and enhanced liver and kidney uptake may limit the application of this method to RAIT, especially when evaluating the method in animals, but with strategies to overcome these limitations, this pretargeting method could be an effective therapeutic alternative.

Development of a streptavidin-anti-carcinoembryonic antigen antibody, radiolabeled biotin pretargeting method for radioimmunotherapy of colorectal cancer. Reagent development

With pretargeting, radioisotope delivery to tumor is decoupled from the long antibody localization process, and this can increase tumor:blood ratios dramatically. Several reagents were prepared for each step of a "two-step" pretargeting method, and their properties were investigated. For pretargeting tumor, streptavidin-monoclonal antibody (StAv-mab) conjugates were prepared by cross-linking sulfo-SMCC-derivatized streptavidin to a free thiol (SH) group on MN-14 [a high-affinity anti-carcinoembryonic antigen (CEA) mab]. Thiolated mabs were generated either by reaction of 2-iminothiolane (2-IT) with mab lysine residues or by reduction of mab disulfide bonds with (2-mercaptoethyl)amine (MEA). Both procedures gave protein-protein conjugates isolated in relatively low yields (20-25%) after preparative size-exclusion (SE) chromatography purification with conservative peak collection. Both StAv-MN-14 conjugates retained their ability to bind to CEA, to an anti-idiotypic antibody to MN-14 (WI2), and to biotin, as demonstrated by SE-HPLC. Two clearing agents, WI2 mab and a biotin-human serum albumin (biotin-HSA) conjugate, were developed to remove excess circulating StAv-MN-14 conjugates in animals. Both clearing proteins were also modified with galactose residues, introduced using an activated thioimidate derivative, to produce clearing agents which would clear rapidly and clear primary mab rapidly. At least 14 galactose residues on WI2 were required to reduce blood levels to 5.9 +/- 0.7% ID/g in 1 h. Faster blood clearance (0.7 +/- 0.2% ID/g) was observed in 1 h using 44 galactose units per WI2. For the delivery of radioisotope to tumor, several biotinylated conjugates consisting of biotin, a linker, and a chelate were prepared. Conjugates showed good in vitro and in vivo stability when D-amino acid peptides were used as linkers, biotin-peptide-DOTA-indium-111 had a slightly longer blood circulation time (0.09 +/- 0.02% ID/g in 1 h) than biotin-peptide-DTPA-indium-111 (0.05 +/- 0.03% ID/g in 1 h) in nude mice. A longer circulation time with the neutral DOTA complex might allow higher tumor uptake.

Advantage of residualizing radiolabels for an internalizing antibody against the B-cell lymphoma antigen, CD22

LL2 is an anti-CD22 pan-B-cell monoclonal antibody which, when radiolabeled, has a high sensitivity for detecting B-cell, non-Hodgkin's lymphoma (NHL), as well as an antitumor efficacy in therapeutic applications. The aim of this study was to determine whether intracellularly retained radiolabels have an advantage in the diagnosis and therapy of lymphoma with LL2. In vitro studies showed that iodinated LL2 is intracellularly catabolized, with a rapid release of the radioiodine from the cell. In contrast, residualizing radiolabels, such as radioactive metals, are retained intracellularly for substantially longer. In vivo studies were performed using LL2-labeled with radioiodine by a non-residualizing (chloramine-T) or a residualizing method (dilactitol-tyramine, DLT), or with a radioactive metal (111In). The biodistribution of a mixture of 125I (non-residualizing chloramine-T compared to residualizing DLT), 111In-labeled LL2 murine IgG2a or its fragments [F(ab')2, Fab'], as well as its humanized, CDR-grafted form, was studied in nude mice bearing the RL human B-cell NHL cell line. Radiation doses were calculated from the biodistribution data according to the Medical International Radiation Dose scheme to assess the potential advantage for therapeutic applications. At all assay times, tumor uptake was higher with the residualizing labels (i.e., 111In and DLT-125I) than with the non-residualizing iodine label. For example, tumor/blood ratios of 111In-labeled IgG were 3.2-, 3.5- and 2.8-fold higher than for non-residualizing iodinated IgG on days 3, 7 and 14, respectively. Similar results were obtained for DLT-labeled IgG and fragments with residualized radiolabels. Tumor/organ ratios also were higher with residualizing labels. No significant differences in tumor, blood and organ uptake were observed between murine and humanized LL2. The conventionally iodinated anti-CD20 antibody, 1F5, had tumor uptake values comparable to those of iodinated LL2, the uptake of both antibodies being strongly dependent on tumor size. These data suggest that, with internalizing antibodies such as LL2, labeling with intracellularly retained isotopes has an advantage over released ones, which justifies further clinical trials with residualizing 111In-labeled LL2 for diagnosis, and residualizing 131I and 90Y labels for therapy.

[Patients' perception of symptoms in colorectal cancer. A cause of delay in diagnosis and treatment]

A questionnaire was given to a series of 50 patients referred for colorectal cancer to the Department of Surgical Gastroenterology at Hvidovre Hospital, Copenhangen. The patients were asked about the length of the period from debut of symptoms to the first visit to their family doctor (patient's delay), detailed symptoms and their views and attitudes towards the significance of these symptoms. More than half of the patients first saw their own doctor more than three months after the first symptom: 17/33 (52%) with a change in bowel habits, 12/28 (43%) with rectal bleeding, 11/19 (58%) with abdominal pain and 4/6 (67%) with a palpable mass. Only 7/44 (15%) thought that cancer was the cause of their symptoms, and a similar minority was afraid of an operation or an ostomy. We conclude that the main cause of patient's delay is a lack of knowledge among the patients about the significance of bowel symptoms, rather than fear of cancer, operation or an ostomy. On this basis we recommend that an information campaign about cancer-related bowel symptoms (bleeding, change of bowel habits) should be carried out with the aim of reducing patient's delay and thereby possibly also improving the prognosis through an early diagnosis.

99Tcm-LL1: a potential new bone marrow imaging agent

LL1, a monoclonal antibody (MAb) to HLA Class-II-like antigen (li determinant) on the surface of B-lymphocytes, monocytes and histiocytes, was evaluated as an agent for bone marrow imaging. Six patients with diverse diseases (non-Hodgkin's lymphoma, n = 2; multiple myeloma, n = 1; polycythaemia vera, n = 1; lung cancer, n = 1; breast cancer, n = 1) were given low protein doses (< 1 mg) of 99Tcm (30 mCi) labelled Fab' of LL1. 99Tcm-sulphur colloid (SC) imaging was performed in three patients for comparison. Both planar and single photon emission tomographic images were acquired using Sopha gamma cameras. As early as 2 h post-MAb injection, excellent bone marrow images were achieved in all patients, demonstrating both normal or hyperproliferative marrow, as well as 'cold' bone marrow abnormalities such as radiation defects or cancer metastases. Similar to SC, relatively high uptake of LL1 was found in the liver and spleen. However, the bone marrow-to-liver and -spleen uptake ratios were approximately 19-fold higher (0.75 vs 0.04) and 6-fold higher (1.23 vs 0.22), respectively, with LL1 than with SC. The higher bone marrow uptake allowed clearly superior visualization of the thoracic spine when compared to SC. The mean T1/2 of blood and whole-body clearance were 0.4 and 66 h, respectively. The highest radiation absorbed doses (in cGy mCi-1) were observed in the spleen (0.47 +/- 0.24), kidneys (0.25 +/- 0.09) and liver (0.14 +/- 0.04). The bone marrow dose was only 0.05 +/- 0.02 cGy mCi-1. These results indicate that bone marrow imaging with 99Tcm-LL1 is feasible, and that LL1 may be a suitable alternative to SC because of better visualization of the lower thoracic spine. Potential applications include the improved detection of bone marrow metastases of solid tumours and the assessment of haematological disorders.

A German-Swedish collection of histopathological slides from 1893

A collection of 159 histopathological slides from 1893 was studied as to origin, condition and documentary value. The slides were dated in Leipzig, Germany, September 26-October 10, 1893. They had apparently been studied jointly by a Swedish veterinary surgeon (Knut August Hjalmar Dahlström) and one or several unknown German colleagues of his in Leipzig, and labelled with their diagnoses. In this paper the collection is referred to as the Leipzig collection. The majority of the slides were well preserved. They reflect part of the animal disease situation, and in some instances also human diseases. Some interesting cases are briefly presented in this paper, one of them even in this abstract, i.e. a case of embryonal nephroma in pig. Six years before Wilms in 1899 described this tumour in children, and 14 years before Day in 1907 described the first case in pig, our then colleagues failed to recognize the embryonic character of the tumour. Their diagnosis was renal adenoma. About 80 percent of the slides were diagnosed as done according to present day procedure. The quality of the slides and that of the diagnostic skill of which they bear witness certainly reflect the far-reaching progress that was made in the knowledge of the nature of diseases and their causes during the second half of the 19th century.

Characterization of retroviruses from patients with multiple sclerosis

These studies were performed to characterize retroviruses found in cell lines spontaneously developed from peripheral blood mononuclear cells (PBMNC) from 6 multiple sclerosis patients, a patient with progressive myelopathy and a healthy control. The cell lines are B-lymphoblastoid and produce Epstein-Barr virus (EBV) particles or express EBV proteins. The B-lymphoblastoid cell lines are also characterized by production of low, fluctuating amounts of retrovirus. The low productivity complicates purification and characterization, but implementation of product-enhanced reverse transcriptase (PERT) assays has provided a highly useful tool for monitoring retrovirus production. By electron microscopy, the retroviral particles appear type-C-like. Functional assays indicate the presence of Pol, Gag and Env. Indirect ELISA demonstrates a significant relation between disease activity and reactivity towards retroviral peptides. Molecular characterization is primarily based on RT-PCR, cloning, sequencing and Northern- or Southern analyses. Molecular characterization is continuing.

Clinical manifestations and molecular epidemiology of five cases of diarrhoea in children associated with Vibrio metschnikovii in Arequipa, Peru

In April 1994, Vibrio metschnikovii was isolated from five infants with watery diarrhoea in Arequipa, Peru, as part of a passive cholera surveillance system. The children ranged in age from 11 to 20 months and had acute diarrhoea, with two cases showing moderate dehydration. Two children also had traces of blood in liquid stool. The children were seen at two different hospitals, and no evidence of a common source of infection was found. No additional V. metschnikovii isolates were identified in the remaining surveillance period that covered the rest of 1994 and 1995. However, stool samples were not screened for enteric pathogens other than vibrios. V. metschnikovii strains isolated from stool samples produced opaque and translucent colonies on agar plates, suggesting capsular material. All isolates were resistant to ampicillin, erythromycin and streptomycin. Plasmid analysis revealed a common 200-kb plasmid in isolates from all cases and an additional 2.7-kb plasmid in three of the isolates. Ribotyping of each isolate after restriction with BglI and HindIII endonucleases demonstrated identical ribotyping patterns. The cases reported suggest that V. metschnikovii may be associated with diarrhoea in man by mechanisms so far unknown.

Internalization and catabolism of radiolabelled antibodies to the MHC class-II invariant chain by B-cell lymphomas

The fate of antibody (Ab) LL1, which reacts with the invariant chain (Ii) subunit of the immature MHC class-II antigen (CD74) after binding to the surface of B-cell lymphomas was investigated. This Ab was internalized and catabolized very rapidly, much faster than other Abs that are considered to be rapidly internalized, such as CD19, CD22 and anti-(transferrin receptor). Such internalization did not depend on Ab cross-linking. The capacity of this uptake process was determined in long-term experiments by increasing the Ab concentration: in 1 day, approx. 8 x 10(5) Ab molecules per cell were catabolized. This analysis was facilitated by the use of radiolabels that are trapped within cells after catabolism of the Abs to which they were conjugated. If the Ab is a reliable marker for the Ii antigen, which is likely, we can conclude that Ii directed to the cell surface appears to be sufficient, indeed more than sufficient, to account for the cell content of mature class-II molecules.

Pain control after dental surgery: a double-blind, randomised trial of lornoxicam versus morphine

Lornoxicam is a new non-steroidal anti-inflammatory drug of the oxicam class. This randomised, double-blind, placebo controlled trial compared the analgesic efficacy and tolerability of intramuscular (IM) injections of lornoxicam (4, 8, 16 and 20 mg) with morphine (10 and 20 mg) and placebo in 252 patients with mainly moderate to severe pain following surgical removal of an impacted mandibular third molar. Patients treated with lornoxicam or morphine experienced a significantly greater cumulative pain relief over the 4-h post-injection period (TOTPAR0-4) than placebo recipients. This effect appeared to be dose-dependent, with patients in the lornoxicam 4 mg or morphine 10 mg groups recording significantly lower TOTPAR0-4 scores than patients in the higher dosage groups of these drugs. No significant difference was detected between the morphine 20 mg group and the lornoxicam 8, 16 and 20 mg groups. Lornoxicam was well tolerated at all doses and was associated with a significantly lower incidence of adverse events than morphine 10 or 20 mg. Thus, the analgesic efficacy of IM lornoxicam at doses > or = 4 mg is superior to placebo, and doses > or = 8 mg are at least as effective as IM morphine 20 mg. Furthermore, lornoxicam possesses a more favourable tolerability profile than morphine and thus represents an attractive alternative for the treatment of moderate to severe acute pain.

Clinical evaluation of tumor targeting with the anticarcinoembryonic antigen murine monoclonal antibody fragment, MN-14 F(ab)2

BACKGROUND

The initial clinical experience with the second-generation, high-affinity, MN-14 immunoglobulin (IgG) anticarcinoembryonic antigen (CEA) monoclonal antibody (MoAb) in patients with CEA-producing tumors was reported previously. A bivalent fragment of this MoAb, MN-14 F(ab)2, was prepared, and its pharmacokinetics, targeting properties, dosimetry, and immunogenicity were investigated.

METHODS

MN-14 F(ab)2(0.6-29 mg) was labeled with 131I(7.7-269 millicuries and injected into 28 patients with CEA-producing cancers. External scintigraphy was used to evaluate tumor targeting. Quantitative external scintigraphy methods were used to determine the organ and tumor radiation doses.

RESULTS

The overall sensitivity of tumor targeting on a lesion basis was 86%, similar to that reported previously for MN-14 whole IgG. The biologic T1/2's for the fragment in the blood and total body (in hours) were 16.8 +/- 4.1 and 59.4 +/- 9.4, respectively, compared with 27.3 +/- 15.7 and 69.6 +/- 32.2 reported for MN-14 IgG. Depending on the protein dose given, high plasma CEA levels (>100ng/ML) resulted in a significant alteration of MoAb pharmacokinetics and organ dosimetry. Individual tumors received an average dose of 10.7 +/- 7.3 centigray [cGy]/mCi, and the tumor-to-total body, red marrow, lung, liver, and kidney dose ratios were 16.8 +/- 11.1, 5.6 +/- 3.6, 5.1 +/- 3.9, 6.0 +/- 3.8, and 3.1 +/- 2.0, respectively (mean + standard deviation [SD]). Only 9 of 18 patients (50%) injected with >4 mg (range: 4-52.1 mg) of MN-14 F(ab)2 developed significant levels of human antimouse antibodies, suggesting that the F(ab)2 may be less immunogenic than the intact IgG.

CONCLUSIONS

MN-14 F(ab)2 exhibits a similar targeting sensitivity and tumor dose as reported previously for the IgG form. The lower red marrow doses combined with lower immunogenicity expected for this agent, may make it a suitable alternative for future imaging and therapeutic applications.

Thiolations, 99mTc labelings, and animal in vivo biodistributions of divalent monoclonal antibody fragments

A number of divalent monoclonal antibody fragments have been derivatized with a bifunctional reagent containing a latent thiol group, and the conjugates were thiol-deprotected by exposure to aqueous hydroxylamine. This two-step procedure enabled convenient 99mTc labeling of thiolated MAb divalent fragments, using either performed 99mTc-glucoheptonate or [99mTc] pertechnetate and single-vial lyophilized formulations of the conjugate and tin. Nonspecific incorporation of radiolabel was negligible, if any, when using nonthiolated antibodies. In animal biodistributions, in nude mice bearing LS174T human colon carcinoma xenografts, the 99mTc-labeled MAb divalent fragments studied were found to result in a 3-fold reduction in the kidney uptake of radioactivity at 24 h, compared to a 99mTc-Fab, and also to lead to improvements in other tumor:nontumor ratios.

Development and evaluation of the specificity of a rat monoclonal anti-idiotype antibody, WN, to an anti-B-cell lymphoma monoclonal antibody, LL2

Anti-idiotype monoclonal antibodies (Mabs) to mLL2, an anti-B-cell lymphoma and CD22-specific murine IgG2a-kappa Mab, were generated by hybridoma technology from splenocytes of Copenhagen rats immunized with mLL2 F(ab')2. Mab WN, an IgG2a-kappa, was selected based on its specific binding to mLL2 and not other IgG isotypes or anti-B-cell Mabs. In a radioimmunoassay, WN was found to inhibit the binding of 125I-labeled mLL2 to Raji cells and to have no effect on the binding of other B-cell-reactive antibodies. Using high performance liquid chromatography analysis, WN was shown to complex specifically with both mLL2 and mLL2 Fab'. Meanwhile, we have constructed chimeric (cLL2) and humanized (hLL2) versions of LL2. Both cLL2 and hLL2 were demonstrated to retain the original antigen specificity and affinity of mLL2 [S.O. Leung et al., Proc. Am. Assoc. Cancer Res., 2872 (abstract), 34: 481, 1993]. The specific binding of WN to either radioiodinated or peroxidase-conjugated mLL2 was inhibited in a dose-response manner, and to a similar extent by mLL2, cLL2, and hLL2. Since the mLL2 complementarity-determining regions are the only sequences common to mLL2, cLL2, and hLL2, the result confirms that WN is specific to the antigen-binding complementarity-determining regions. A WN binding assay is currently being evaluated as a substitute for the tedious, and sometimes inconsistent, Raji cell-binding assay for the determination of LL2 immunoreactivity. In conclusion, we have developed an anti-idiotype Mab, WN, to mLL2. Its potential use as a surrogate antigen for B-cell lymphoma is under investigation.

Treatment of non-Hodgkin's lymphoma with radiolabeled murine, chimeric, or humanized LL2, an anti-CD22 monoclonal antibody

LL2 is a murine IgG2a anti-CD22 monoclonal antibody found to react with virtually all non-Hodgkin's lymphomas (NHLs). Twenty-one patients with chemotherapy-resistant NHL received nonmyeloablative doses of 131I-labeled LL2 IgG and F(ab')2 ranging from 15 to 343 mCi given in cycles of 15-50 mCi, for up to seven treatment cycles. The cumulative protein dose ranged from 1.1 mg IgG to 157 mg F(ab')2. Seventeen patients were assessable for treatment response, and antitumor effects were seen in five (one complete remission, two partial remissions, and two minor or mixed responses). In addition, one complete response was seen in a patient who received only "diagnostic" doses of 131I-LL2 IgG. Thus, a total of six patients had responses according to the defined response criteria. Three additional patients have been treated with potentially myeloablative doses of 131I-LL2 IgG at a starting dose level of 90 mCi/m2 (100 mg). Two patients were evaluable, and both had partial remissions lasting 8 and 3 months, respectively. Chimeric and complementarity-determining region-grafted LL2 have been developed. Initial clinical studies have shown that these agents have targeting properties similar to the murine LL2 and, therefore, may be suitable alternatives to murine LL2 in the treatment of NHL. LL2 is a promising agent for the treatment of lymphoma, particularly when the maximum tolerated dose is given either with or without autologous bone marrow transplantation.

Site-specific modifications of light chain glycosylated antilymphoma (LL2) and anti-carcinoembryonic antigen (hImmu-14-N) antibody divalent f1agments

Site-specific introduction of metal-chelating groups into F(ab')2 fragments of an antilymphoma antibody (LL2) possessing a natural Asn-linked light chain carbohydrate and an anti-carcinoembryonic antigen antibody (hImmu-14-N) grafted with a light chain carbohydrate site is described. For this purpose, four yttrium- (and indium)-chelating agents were used, containing a primary amino group for antibody binding and 1-(4-substituted benzyl)diethylenetriaminepentaacetic acid as the metal-chelator, separated by structurally different additional linkers. Conjugates were prepared by reacting excess chelator with oxidized carbohydrate of F(ab')2 fragments, with or without a subsequent reduction step. The conjugates, with up to an average of 5.5 chelating groups attached to a F(ab')2 fragment, were readily labeled with 90Y and 111In and were found to retain antigen-binding ability in in vitro assays. Tumor targeting was demonstrated using a 88Y-labeled hImmu-14-N F(ab')2 carbohydrate-modified conjugate. 2-Pyridyldithiopropionic hydrazide was conjugated to the carbohydrate region, and the disulfide was selectively deprotected to the thiol group, which is reactive with reduced 99mTc. These initial experiments establish that light chain carbohydrate modification of F(ab')2 is as facile as with the Fc-region carbohydrate of intact IgG, and thereby offer the possibility of designing site-specifically substituted F(ab')2 fragments with favorable pharmacokinetic properties.