Safety and efficacy of 188-rhenium-labeled antibody to melanin in patients with metastatic melanoma.

There is a need for effective "broad spectrum" therapies for metastatic melanoma which would be suitable for all patients. The objectives of Phase Ia/Ib studies were to evaluate the safety, pharmacokinetics, dosimetry, and antitumor activity of (188)Re-6D2, a 188-Rhenium-labeled antibody to melanin. Stage IIIC/IV metastatic melanoma (MM) patients who failed standard therapies were enrolled in both studies. In Phase Ia, 10 mCi (188)Re-6D2 were given while unlabeled antibody preload was escalated. In Phase Ib, the dose of (188)Re-6D2 was escalated to 54 mCi. SPECT/CT revealed (188)Re-6D2 uptake in melanoma metastases. The mean effective half-life of (188)Re-6D2 was 12.4 h. Transient HAMA was observed in 9 patients. Six patients met the RECIST criteria for stable disease at 6 weeks. Two patients had durable disease stabilization for 14 weeks and one for 22 weeks. Median overall survival was 13 months with no dose-limiting toxicities. The data demonstrate that (188)Re-6D2 was well tolerated, localized in melanoma metastases, and had antitumor activity, thus warranting its further investigation in patients with metastatic melanoma.

Molecular specific and cell selective cytotoxicity induced by a novel synthetic HLA-DR antibody mimic for lymphoma and leukemia.

Like rituximab, monoclonal antibodies reactive with human leukocyte antigen have potent antilymphoma activity. However, size limits their vascular and tissue penetration. To mimic monoclonal antibody binding, nanomolecules have been synthesized, shown specific for the beta subunit of HLA-DR10, and selective for cells expressing this protein. Selective high affinity ligands (SHALs) containing the 3-(2-([3-chloro-5-trifluoromethyl)-2-pyridinyl]oxy)-anilino)-3-oxopropanionic acid (Ct) ligand residualized and had antilymphoma activity against expressing cells. Herein, we show the extraordinary potency in mice with human lymphoma xenografts of a tridentate SHAL containing this ligand. After titrating antilymphoma activity in cell culture, a randomized preclinical study of a tridentate SHAL containing the Ct ligand was conducted in mice with established and aggressive human lymphoma xenografts. Mice having HLA-DR10 expressing Raji B- or Jurkat's T-lymphoma xenografts were randomly assigned to receive either treatment with SHAL at a dose of 100 ng i.p. weekly for 3 consecutive weeks, or to be untreated. Primary end-points were cure, overall response rates and survival. Toxicity was also evaluated in these mice, and a USFDA general safety study was conducted in healthy Balb/c mice. In Raji cell culture, the threshold and IC50 concentrations for cytotoxic activity were 0.7 and 2.5 nmol (pm/ml media), respectively. When compared to treated Jurkat's xenografts or untreated xenografts, Raji xenografts treated with the SHAL showed an 85% reduction in hazard of death (P=0.014; 95% confidence interval 32-95% reduction). There was no evidence for toxicity even after i.p. doses 2000 times greater than the treatment dose associated with cure of a majority of the mice with Raji xenografts. When compared with control groups, treatment selectively improved response rates and survival in mice with HLA-DR10 expressing human lymphoma xenografts at doses not associated with adverse events and readily achievable in patients.

Pre-clinical evaluation and efficacy studies of a melanin-binding IgM antibody labeled with 188Re against experimental human metastatic melanoma in nude mice.

PURPOSE: Currently there is no satisfactory treatment for metastatic melanoma. Radioimmunotherapy (RIT) uses the antigen-antibody interaction to deliver lethal radiation to target cells. Recently we established the feasibility of targeting melanin in tumors with 188-Rhenium ((188)Re)-labeled 6D2 mAb to melanin. Here we carried out pre-clinical development of (188)Re-6D2 to accrue information necessary for a Phase I trial in patients with metastatic melanoma. RESULTS: TCEP proved to be effective in generating a sufficient number of -SH groups on 6D2 to ensure high radiolabeling yields with (188)Re and preserved its structural integrity. (188)Re-6D2 was quickly cleared from the blood with the half-life of approximately 5 hrs and from the body--with the half-life of 10 hr. The doses of 0.5, 1.0 and 1.5 mCi significantly (p < 0.05) slowed down A2058 tumor growth in nude mice, also causing release of melanin into the extracellular space which could provide additional target for repeated treatments. Transient effects of RIT on WBC and platelet counts resolved by Day 14 post-treatment. EXPERIMENTAL DESIGN: Tris(2-Carboxyethyl) Phosphine Hydrochloride (TCEP) was evaluated as potential agent for generation of -SH groups on 6D2 mAb. TCEP-treated 6D2 mAb was radiolabeled with (188)Re and its radiochemical purity and stability was measured by ITLC and HPLC and its immunoreactivity--by melanin-binding ELISA. The pharmacokinetics, therapeutic efficacy and acute hematologic toxicity studies were performed in nude mice bearing lightly pigmented A2058 human metastatic melanoma tumors. CONCLUSIONS: We have developed radiolabeling and quality control procedures for melanin-binding (188)Re-6D2 mAb which made possible currently an on-going Phase I clinical trial in patients with metastatic melanoma.

NanoFerrite particle based radioimmunonanoparticles: binding affinity and in vivo pharmacokinetics.

Dextran and PEG-coated iron oxide nanoparticles (NP), when suitably modified to enable conjugation with molecular targeting agents, provide opportunities to target cancer cells. Monoclonal antibodies, scFv, and peptides conjugated to 20 nm NP have been reported to target cancer for imaging and alternating magnetic field (AMF) therapy. The physical characteristics of NPs can affect their in vivo performance. Surface morphology, surface charge density, and particle size are considered important factors that determine pharmacokinetics, toxicity, and biodistribution. New NanoFerrite (NF) particles having improved specific AMF absorption rates and diameters of 30 and 100 nm were studied to evaluate the variation in their in vitro and in vivo characteristics in comparison to the previously studied 20 nm superparamagnetic iron oxide (SPIO) NP. SPIO NP 20 nm and NF NP 30 and 100 nm were conjugated to (111)In-DOTA-ChL6, a radioimmunoconjugate. Radioimmunoconjugates were conjugated to NPs using 25 microg of RIC/mg of NP by carbodiimide chemistry. The radioimmunonanoparticles (RINP) were purified and characterized by PAGE, cellulose acetate electrophoresis (CAE), live cell binding assays, and pharmacokinetics in athymic mice bearing human breast cancer (HBT 3477) xenografts. RINP (2.2 mg) were injected iv and whole body; blood and tissue data were collected at 4, 24, and 48 h. The preparations used for animal study were >90% monomeric by PAGE and CAE. The immunoreactivity of the RINP was 40-60% compared to (111)In-ChL6. Specific activities of the doses were 20-25 microCi/2.2 mg and 6-11 microg of mAb/2.2 mg of NP. Mean tumor uptakes (% ID/g +/- SD) of each SPIO 20 nm, NF 30 nm, and 100 nm RINP at 48 h were 9.00 +/- 0.8 (20 nm), 3.0 +/- 0.3 (30 nm), and 4.5 +/- 0.8 (100 nm), respectively; the ranges of tissue uptakes were liver (16-32 +/- 1-8), kidney (7.0-15 +/- 1), spleen (8-17 +/- 3-8), lymph nodes 5-6 +/- 1-2), and lung (2.0-4 +/- 0.1-2). In conclusion, this study demonstrated that 100 nm NF NP could be conjugated to (111)In-mAb so that the resulting RINP had characteristics suitable for AMF therapy. Although 100 nm RINP targeted tumor less than 20 nm SPIO RINP, their heating capacity is typically 6 times greater, suggesting the 100 nm NF RINP could still deliver better therapy with AMF.

Development of anti-MUC1 di-scFvs for molecular targeting of epithelial cancers, such as breast and prostate cancers.

Pretargeted radioimmunotherapy (RIT) is a promising approach to increase the therapeutic index of RIT for malignant solid tumors. For pretargeted RIT of epithelial cancers, such as breast and prostate, mucin 1 (MUC1), the epithelial mucin, was chosen as a target antigen (Ag). Overexpression, hypoglycosylation and loss of apical distribution on the cellular membrane distinguish the tumor associated MUC1 from normal MUC1. These characteristics of MUC1, best known in breast cancer, were validated in prostate cancer. The multivalent bispecific MUC1 pretargeting molecule under development consists of a tumor binding module and a radioactive hapten capturing module. The building blocks of each module were chosen as single chain antibody fragments (scFv) to be covalently attached to a multifunctional polyethylene glycol (PEG) scaffold. PEGylation studies with scFvs selected from anti-MUC1 libraries and engineered with a free thiol for site-specific conjugation showed that highest reaction yields were obtained with short monofunctional PEG molecules. To accommodate the use of a bifunctional PEG for covalent assembly of binding and capturing modules, the MUC1 binding module was developed into a di-scFv-SH format and optimized for linker length and location of the free thiol in respect to Ag binding and site-specific conjugation. Approaches under study to improve PEGylation yields with bifunctional PEG molecules include alkyne-azide cycloaddition. Assembly efficiencies, through PEGylation, of the binding and capturing modules and pharmacokinetics will influence the final valency of the MUC1 pretargeting molecule: anti-MUC1 di-scFv-PEG- anti-radioactive hapten scFv or di-scFv-PEG-anti-radioactive hapten di-scFv.

MINERVA: a multi-modality plugin-based radiation therapy treatment planning system.

Researchers at the INEEL, MSU, LLNL and UCD have undertaken development of MINERVA, a patient-centric, multi-modal, radiation treatment planning system, which can be used for planning and analysing several radiotherapy modalities, either singly or combined, using common treatment planning tools. It employs an integrated, lightweight plugin architecture to accommodate multi-modal treatment planning using standard interface components. The design also facilitates the future integration of improved planning technologies. The code is being developed with the Java programming language for interoperability. The MINERVA design includes the image processing, model definition and data analysis modules with a central module to coordinate communication and data transfer. Dose calculation is performed by source and transport plugin modules, which communicate either directly through the database or through MINERVA's openly published, extensible markup language (XML)-based application programmer's interface (API). All internal data are managed by a database management system and can be exported to other applications or new installations through the API data formats. A full computation path has been established for molecular-targeted radiotherapy treatment planning, with additional treatment modalities presently under development.

A review of human anti-globulin antibody (HAGA, HAMA, HACA, HAHA) responses to monoclonal antibodies. Not four letter words.

The United States Food and Drug Administration (FDA) has approved unconjugated monoclonal antibodies (MAbs) for immunotherapy (IT) of B-cell lymphoma, breast cancer and acute myeloid leukemia. More recently, approval has been given for conjugated ZevalinTM ((90)yttrium ibritumomab tiuxetan, IDEC-Y2B8, Biogen Idec, Cambridge, MA) and BexxarTM ((131)I-tositumomab, Corixa, Corp., Seattle, WA and GlaxoSmithKline, Philadelphia, PA) anti-CD20 MAbs for use in radioimmunotherapy (RIT) of non-Hodgkin's lymphoma (NHL), thus redefining the standard care of cancer patients. Because of, and despite a lack of basis for concern about allergic reactions due to human antibody responses to these foreign proteins, assays were developed to determine HAGA (human anti-globulin antibody) levels that developed in patient sera following treatment with MAbs. Strategies were also devised to ''humanize'' MAbs and to temporarily block patient immune function with drugs in order to decrease the seroconversion rates, with considerable success. On the other hand, a survival advantage has been observed in some patients who developed a HAGA following treatment. This correlates with development of an anti-idiotype antibody cascade directed toward the MAbs used to treat these patients. What follows is a selective review of HAGA and its effect on cancer treatment over the past 2 decades.

Radiolabeled anti-lymphoma antibodies.

This promises to be an era of remarkable change for patients afflicted with NHL. Although the cause of NHL remains unknown, there is greater understanding of 'these diseases' at the molecular level. Insights into genetic aberrations that interrupt apoptosis or that promote proliferation have profound implications for the future management of NHL (and other malignancies). Ongoing trials of immunotherapy and RIT continue to show excellent response rates in patients with relapsed or refractory NHL and remarkably favorable safety and toxicity profiles. More drug approvals can be anticipated. As antibody engineering progresses, formerly theoretical questions regarding optimized targeting and antibody affinity, take on relevance and practicality [65]. The ability to generate new constructs, such as bivalent antibodies, or fusion proteins incorporating two disparate functional proteins, presents exciting opportunities for radiopharmaceutical development. The role of bifunctional antibodies in tumor targeting is likely to increase in importance, both as a means of targeting, and as a technique for increasing MAb specificity [66,67]. Pretargeting approaches are in development as a way of decreasing the amount of time that the radionuclide circulates in the blood (radiating normal tissues) thereby allowing the administration of higher doses of radionuclide (radioactivity and radiation) [67-69].

Metabolite production in patients with lymphoma after radiometal-labeled antibody administration.

UNLABELLED: Radiometal-labeled monoclonal antibodies are retained longer in tumors than iodinated antibodies, leading to their increased use for radioimmunotherapy. Dissociation of radioiodine from the antibody during metabolism has been documented. We now report metabolites in the plasma of lymphoma patients given 111In- and 90Y-2-iminothiolane-2-[p-(bromoacetamido)benzyl]-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid-Lym-1 (111In/90Y-2IT-BAD-Lym-1). METHODS: Nineteen patients with non-Hodgkin's lymphoma (NHL) received 111In- and 90Y-2IT-BAD-Lym-1; 111In was used as a surrogate tracer for 90Y, which emits no gamma-photon. Plasma was obtained up to 7 d and analyzed by high-performance liquid chromatography to determine the fraction of radiolabel associated with monomeric antibody, metabolites, and complexed antibody. Planar images of conjugate views were acquired up to 7 d and used to quantitate 111In in organs and tumors. RESULTS: Metabolites and complexes were observed in the plasma of every patient who received 111In-2IT-BAD-Lym-1. At 3 d, the mean percentages of 111In in the patients' plasma in monomeric, metabolite, and complexed forms were 54%, 36%, and 10%, respectively. Metabolites of 90Y-2IT-BAD-Lym-1 were formed to a similar extent. In comparison, in groups of breast and prostate cancer patients who received the radioimmunoconjugate 111In-2IT-BAD-m170, 91% and 94% of 111In in the patients' plasma were in monomeric form, respectively. Metabolites and complexes of 111In-2IT-BAD-Lym-1 contributed a mean 10% of the total area under the time-activity curve (AUC) for blood. Little formation of metabolites and complexes occurred in vitro in NHL patient or volunteer plasma or in Raji cell culture. The clinical and in vitro data supported the processing of 111In/90Y-2IT-BAD-Lym-1 in the hepatocytes as the dominant mechanism for the production of metabolites. CONCLUSION: Metabolites of 111In/90Y-2IT-BAD-Lym-1 accounted for 10% of blood AUC in patients. The therapeutic index was adversely affected by metabolism of 111In/90Y-2IT-BAD-Lym-1 to the extent that the tumor specificity of the radioactive metabolites was lost.

Apoptosis-related gene and protein expression in human lymphoma xenografts (Raji) after low dose rate radiation using 67Cu-2IT-BAT-Lym-1 radioimmunotherapy.

Despite low radiation dose rates, radioimmunotherapy (RIT) has proven particularly effective in the treatment of malignancies, such as lymphoma. Apoptosis has been suggested to be a major mechanism for cell death from continuous low-dose rate radiation from radioimmunotherapy. The goal of this study was to examine Raji lymphoma xenografts for induction of apoptosis and modulation of apoptosis-related gene and protein expression in response to 67Cu-2IT-BAT-Lym-1 RIT. In preclinical and clinical trials, 67Cu-2IT-BAT-Lym-1 has shown an exceptionally long tumor residence time associated with substantial cumulated radiation doses. The Raji model mirrors human lymphomas that have mutant p53 and increased BCL2 expression. Untreated athymic BALB/c nu/nu mice and mice treated with 400 micrograms Lym-1, or 335-500 microCi 67Cu on less than 400 micrograms Lym-1 antibody, were observed for toxicity and response over 84 days. Subgroups of 4-5 mice were sacrificed at 3, 6 and 24 h after therapy so that tumors could be examined for poly(ADP-ribose) polymerase (PARP) and DNA ladder evidence for apoptosis and for BCL2, p53, p21, GADD45, TGF-beta 1 and c-MYC gene and protein expression. Untreated tumors had little evidence of apoptosis and Lym-1 had no effect on apoptosis or gene expression. 67Cu-2IT-BAT-Lym-1 RIT induced an overall response rate of 50% with tolerable toxicity, and 29% of the tumors were cured at cumulated tumor radiation doses of about 1800 cGy. Apoptosis was greatly increased in the RIT treated Raji xenografts as evidenced by cleavage of PARP to the characteristic 85 kD fragment at 3 and 6 h and by the DNA cleavage pattern. BCL2 gene and protein expression were substantially decreased at 3 and 24 h, respectively, after 67Cu-2IT-BAT-Lym-1 RIT despite only modest cumulated radiation doses (56 cGy at 3 h). Evidence for apoptosis preceded tumor regression by 4-6 days. In these therapy-resistant, human lymphoma tumors treated with 67Cu-2IT-BAT-Lym-1, apoptosis was convincingly demonstrated to be a major mechanism for the effectiveness of RIT and occurred by p53-independent mechanisms.

Radioimmunotherapy with (111)In/(90)Y-2IT-BAD-m170 for metastatic prostate cancer.

PURPOSE: Over 31,000 Americans die of androgen-independent metastatic prostate cancer each year. New strategies that do not involve hormonal manipulation but instead recognize the biochemical and molecular characteristics of prostate cancer are needed. Radioimmunotherapy (RIT) uses a tumor-specific monoclonal antibody to deliver systemic, targeted radiation to cancer. The objectives of this Phase I study of (111)In-2IT-BAD-m170 (for imaging) and (90)Y-2IT-BAD-m170 (for therapy) were to determine the toxicity and maximum tolerated dose (MTD), the specificity for targeting metastatic prostate cancer, and the efficacy for palliation of pain. EXPERIMENTAL DESIGN: M170 is a mouse monoclonal antibody that targets adenocarcinomas. Patients with adequate renal and liver function, rising prostate-specific antigen, and androgen-independent metastatic prostate cancer were eligible. After estimation of dosimetry and pharmacokinetics with (111)In-2IT-BAD-m170, a single dose of (90)Y-2IT-BAD-m170 (0.185, 0.370, 0.555, or 0.740 GBq/m(2)) was administered to cohorts of three patients. Pain was assessed objectively by questionnaires before and for 8 weeks after RIT; weekly prostate-specific antigen levels were obtained for 2 months after RIT. RESULTS: The MTD of (90)Y-2IT-BAD-m170 was 0.740 GBq/m(2) for patients that had up to 10% of the axial skeleton involved with prostate cancer. Toxicity was almost exclusively confined to reversible myelosuppression. Metastatic prostate cancer was targeted by (111)In-2IT-BAD-m170 in all 17 patients. The mean radiation dose delivered to 39 bone and 18 nodal metastases by (90)Y-2IT-BAD-m170 was 10.5 Gy/GBq (range 2.8-25.1). Thirteen of 17 patients reported pain before (90)Y-2IT-BAD-m170; 7 of these 13 had a partial or complete resolution of pain that lasted an average of 4.3 weeks. CONCLUSIONS: This study determined the MTD of (111)In/(90)Y-2IT-BAD-m170 in patients with metastatic prostate cancer. The drugs were well tolerated, targeted metastases, and temporarily palliated pain.

Role of radiation dosimetry in radioimmunotherapy planning and treatment dosing.

Cancer-seeking antibodies (Abs) carrying radionuclides can be powerful drugs for delivering radiotherapy to cancer. As with all radiotherapy, undesired radiation dose to critical organs is the limiting factor. It has been proposed that optimization of radioimmunotherapy (RIT), that is, maximization of therapeutic efficacy and minimization of normal tissue toxicity, depends on a foreknowledge of the radiation dose distributions to be expected. The necessary data can be acquired by established tracer techniques, in individual patients, using quantitative radionuclide imaging. Object-oriented software systems for estimating internal emitter radiation doses to the tissues of individual patients (patient-specific radiation dosimetry), using computer modules, are available for RIT, as well as for other radionuclide therapies. There is general agreement that radiation dosimetry (radiation absorbed dose distribution, cGy) should be utilized to establish the safety of RIT with a specific radiolabeled Ab in the early stages (i.e. phase I or II) of drug evaluation. However, it is less well established that radiation dose should be used to determine the radionuclide dose (amount of radioactivity, GBq) to be administered to a specific patient (i.e. radiation dose-based therapy). Although treatment planning for individual patients based upon tracer radiation dosimetry is an attractive concept and opportunity, particularly for multimodality RIT with intent to cure, practical considerations may dictate simpler solutions under some circumstances.

Anti-HLA-DR/anti-DOTA diabody construction in a modular gene design platform: bispecific antibodies for pretargeted radioimmunotherapy.

Recombinant immunoglobulin libraries of single chain molecules (sc) from the variable domains of antibody light and heavy chains (Fv), have great promise for new approaches to radioimmunotherapy (RIT). However, creating and evaluating scFv from diverse sources is time consuming and differences in molecular format can influence in vitro and in vivo characteristics. Furthermore, scFv do not have optimal characteristics for targeting therapy to tumor because of their small size and univalent binding. Diabody molecules at least twice the size of scFv are better for RIT because bivalent and bispecific molecules can be constructed. A polymerase chain reaction (PCR) based primer system was created to easily convert scFv genes into a diabody gene format, once they have been placed into pCANTAB 5E, a readily available vector. The primer system for this diabody gene platform was developed and tested by constructing an anti-lymphoma/anti-chelate, bispecific diabody (anti-HLA-DR/anti-DOTA). Two mouse scFv libraries were screened for reactive clones using recombinant phage display techniques. Selected mouse anti-HLA-DR and anti-DOTA scFv genes were combined, ligated into the pCANTAB 5E vector that co-expressed these self-assembling scFv in E. coli as two mismatched nonlinked pairs (VHA-link-VLB; VHB-link-VLA). The diabody protein that was purified from periplasm had the expected molecular characteristics when analyzed by sequencing, chromatography, electrophoresis and Western blot. This modular gene design platform provides methodology for easy and rapid creation of diabody molecules from diverse scFv libraries. Diabodies from various scFv can easily be produced, thereby facilitating comparative preclinical studies en route to development of new tumor targeting molecules.

Antibody phage display applications for nuclear medicine imaging and therapy.

Antibody-based constructs genetically engineered from genes of diverse origin provide a remarkable opportunity to develop functional molecular imaging techniques and specific molecular targeted radionuclide therapies. Phage display libraries of antibody fragment genes can be used to select antibody-based constructs that bind any chosen epitope. A large naive human antibody-based library was used to illustrate binding of antibody constructs to a variety of common and unique antigens. Antibody-based libraries from hybridoma cells, lymphocytes from immunized humans or from mice and human antibody repertoires produced in transgenic mice have also been described. Several orders of magnitude of affinity enhancement can be achieved by random or site specific mutations of the selected binding peptide domains of the scFv. Affinities (Kd) as high as 10(-11) M (10 pM) for affinity-matured scFv have been documented. Such gene libraries thus offer an almost limitless variety of antibody-based molecular binding peptide modules that can be used in creative ways for the construction of new targeting agents for functional or molecular imaging and therapy.

Efficacy and toxicity of radioimmunotherapy with (90)Y-DOTA-peptide-ChL6 for PC3-tumored mice.

BACKGROUND: Radioimmunotherapy (RIT) is a new therapeutic modality capable of systemic delivery of radionuclides specifically to sites of metastatic cancer. The L6 monoclonal antibody has been shown to target prostate cancer in preclinical studies and, along with chimeric L6 (ChL6), has been used for RIT in breast cancer patients. METHODS: Pharmacokinetics, blood counts, body weight, and antitumor activity of RIT with (90)yttrium-((90)Y)-DOTA-peptide-ChL6 (75-260 microCi) were determined in nude mice bearing human prostate cancer (PC3) xenografts. RESULTS: RIT produced durable, dose-dependent antitumor effects with a 100% response rate using 112 microCi and 150 microCi (the maximum tolerated dose) of (90)Y-DOTA-peptide-ChL6. Myelotoxicity was reversible, dose-limiting, and dose-related. RIT was associated with improved survival (P = 0.05). All 5 mice in the 150-microCi group survived the 84-day study period vs. 1/8 (13%) for untreated, tumored control mice. CONCLUSIONS: (90)Y-DOTA-peptide-ChL6 targets PC3 human prostate cancer xenografts in nude mice and has an antitumor effect. These results provide a basis for future RIT trials for patients with metastatic prostate cancer.

Radiation dosimetry for 90Y-2IT-BAD-Lym-1 extrapolated from pharmacokinetics using 111In-2IT-BAD-Lym-1 in patients with non-Hodgkin's lymphoma.

UNLABELLED: Several monoclonal antibodies, including Lym-1, have proven effective for treatment of hematologic malignancies. Lym-1, which preferentially targets malignant lymphocytes, has induced therapeutic responses and prolonged survival in patients with non-Hodgkin's lymphoma (NHL) when labeled with 131. Because radiometal-labeled monoclonal antibodies provide higher tumor radiation doses than corresponding 131I-labeled monoclonal antibodies, the radiation dosimetry of 90Y-2-iminothiolane-2-[p-(bromoacetamido)benzyl]-1,4,7,10-tetraazacyc lododecane-N,N',N",N"'-tetraacetic acid-Lym-1 (90Y-21T-BAD-Lym-1) is of importance because of its potential for radioimmunotherapy. Although 90Y has attractive properties for therapy, its secondary bremsstrahlung is less suitable for imaging and pharmacokinetic studies in patients. Thus, the pharmacokinetic data obtained for 111In-21T-BAD-Lym-1 in patients with NHL were used to calculate dosimetry for 90SY-21T-BAD-Lym-1. METHODS: Thirteen patients with advanced-stage NHLwere given a preload dose of unmodified Lym-1 followed by an imaging dose of 111In-21T-BAD-Lym-1. Sequential imaging and blood and urine samples obtained for up to 10 d after infusion were used to assess pharmacokinetics. Using 111In pharmacokinetic data and 90Y physical constants, radiation dosimetry for 90Y-21T-BAD-Lym-1 was determined. RESULTS: The uptake of 111In-21T-BAD-Lym-1 in tumors was greater than uptakes in the lung and kidney but similar to uptakes in the liver and spleen. The biologic half-time in tumors was greater than in lungs. The mean radiation dose to tumors was 6.57 +/- 3.18 Gy/GBq. The mean tumor-to-marrow (from blood) radiation ratio was 66:1, tumor-to-total body was 13:1, and tumor-to-liver was 1:1. Images of 111In were of excellent quality; tumors and normal organs were readily identified. Mild and transient Lym-1 toxicity occurred in 3 patients. CONCLUSION: Because of the long residence time of 111In-2IT-BAD-Lym-1 in tumors, high 90Y therapeutic ratios (tumor-to-tissue radiation dose) were achieved for some tissues, but the liver also showed high uptake and retention of the radiometal.

Neovascular targeting with cyclic RGD peptide (cRGDf-ACHA) to enhance delivery of radioimmunotherapy.

Radioimmunotherapy (RIT) has been hampered by delivery of only a small fraction of the administered dose of radiolabeled MAb to tumor. A strategy for creating and controlling tumor vascular permeability would enable more effective RIT. The alpha v beta 3 integrin receptor is an appealing target for strategies designed to enhance permeability of tumor vessels because it is highly and preferentially expressed in most tumors. In human tumor mouse models, apoptosis of neovascular endothelial cells has been demonstrated after treatment with alpha v beta 3 antagonists. Since this apoptotic effect could transiently increase permeability of tumor blood vessels, radiolabeled antibodies (MAb) circulating during this period would have increased access to extravascular tumor. To determine if this hypothesis was correct, a pharmacokinetic study of an immunospecific MAb given after an alpha v beta 3 antagonist was performed in nude mice bearing human breast cancer xenografts. The alpha v beta 3 antagonist, cyclic RGD pentapeptide (c-RGDf-ACHA; cyclo arginine glycine aspartic acid D-phenylalanine -1 amino cyclohexane carboxylic acid), inhibits alpha v beta 3 binding to its vitronectin ligand at nanomolar levels. Cyclic RGD peptide (250 micrograms i.p.) given 1 hour before 111In-ChL6 MAb resulted in a 40-50% increase in tumor uptake (concentration), when compared to the control tumor uptake, of MAb 24 hours after administration. When cyclic RGD peptide was given as a continuous infusion (17.5 micrograms/hr) for 1 or 24 hours before 111In-ChL6, tumor uptake of 111In-ChL6 was increased less, and, these data were not statistically different from the control data. There were no differences for any of the groups in the groups in the concentrations of 111In-ChL6 in normal organs or blood when compared to the control group. The results suggest that cyclic RGD peptide provided a temporary, selective increase in tumor vascular permeability, that allowed a larger fraction of the 111In-ChL6 to accumulate in the tumor.

131I-Lym-1 in mice implanted with human Burkitt's lymphoma (Raji) tumors: loss of tumor specificity due to radiolysis.

UNLABELLED: Preliminary evaluations of 125I-labeled Lym-1, an anti-lymphoma mouse IgG2a monoclonal antibody, demonstrated favorable tumor uptake in mice bearing human Burkitt's lymphoma (Raji) tumors. In this study, the pharmacokinetics of 125I- and 131I-Lym-1, and the dosimetry, efficacy, and toxicity of 131I-Lym-1 in Raji-tumored mice were evaluated. METHODS: Lym-1 was radioiodinated by the chloramine-T method and analyzed for monomeric fraction and immunoreactivity (antigen cell binding, relative to unmodified Lym-1). Nude mice bearing Raji tumors (20-500 mm3) received 1.5 MBq (40 microCi) 125I-Lym-1, or 1.5, 7.4, 14.8, or 18.5 MBq (40, 200, 400, or 500 microCi) 131I-Lym-1. Pharmacokinetic data (total body and blood clearance and biodistribution) were used to estimate radiation dosimetry. Mini-thermoluminescent dosimetry (TLD) was also used to measure radiation dosimetry directly for 7 days after injection of 131I-Lym-1. Tumor size, survival, body weight, and blood counts were monitored for 60 days to evaluate therapeutic efficacy and toxicity of 131I-Lym-1. RESULTS: At the time of injection, the mean quality assurance (QA) values for 125I-Lym-1 were 100% monomer and 100% relative immunoreactivity; the corresponding values for 131I-Lym-1 were 73% and 66%, indicating that radiolysis had occurred during the interval between radiolabeling and injection. 125I-Lym-1 exhibited high and sustained concentration in tumors relative to normal organs, whereas 131I-Lym-1 did not. Assuming identical pharmacokinetic behavior to 125I-Lym-1, 131I-Lym-1 would deliver radiation doses of 3.45, 0.83, 1.03, 0.34, and 0.56 Gy per MBq injected (12.8, 3.1, 3.8, 1.3, and 2.1 rad/microCi), to tumor, liver, lungs, total body, and marrow, respectively. When the actual pharmacokinetic data for 131I-Lym-1 (1.5 MBq) were used to estimate dosimetry, corresponding values of 0.51, 0.72, 0.49, 0.31, and 0.41 Gy/MBq (1.9, 2.7, 1.8, 1.1, and 1.5 rad/microCi) were obtained. Similar values were obtained for mice receiving 7.4 or 14.8 MBq of 131I-Lym-1. Similarly, TLD data indicated little preferential radiation dosimetry to tumor. Response rates (cure + CR + PR) for mice receiving 0, 7.4, 14.8, and 18.5 MBq of 131I-Lym-1 were 8%, 7%, 21%, and 45%, respectively. The LD50/30 dose of 131I-Lym-1 was 12.7 MBq (343 microCi). CONCLUSIONS: 125I-Lym-1 exhibited high and sustained concentration in Raji tumors in mice, indicating excellent therapeutic potential for 131I-Lym-1. However, in vitro QA results for 131I-Lym-1 indicated that radiolysis had occurred, and 131I-Lym-1 demonstrated little accumulation in tumor, or preferential radiation dosimetry to tumor in the same model.

A phase I study of 90Y-2IT-BAD-Lym-1 in patients with non-Hodgkin's lymphoma.

BACKGROUND: Prior clinical trials proved that all histologic grades of chemotherapy-resistant B-cell non-Hodgkin's lymphoma (NHL) could respond to radio-immunotherapy (RIT) with 131I-Lym-1 and 67Cu-2IT-BAT-Lym-1. This Phase I study was conducted to determine the safety and maximum tolerated dose (MTD) of 90Y-2IT-BAD-Lym-1. METHODS: Lym-1 is a mouse monoclonal antibody that preferentially targets malignant B-lymphocytes. 90Y has beta emissions suitable for therapy but no gamma emissions, therefore, 111In-2IT-BAD-Lym-1 is used for imaging. The macrocyclic chelator, DOTA, bound 90Y tightly to form a stable drug. Patients with chemotherapy-resistant NHL received 90Y-2IT-BAD-Lym-1 at administered doses of: 0.185, 0.278, or 0.370 GBq/m2. RESULTS: Myelotoxicity, especially thrombocytopenia, was dose-limiting. No significant non-hematologic toxicity occurred. Human anti-mouse antibody (HAMA) developed in 3/8 patients. The mean radiation dose to the 33 imaged tumors was 7.0 Gy/GBq. Lung, kidney and liver received mean radiation doses of 1.3, 2.4, and 6.4 Gy/GBq, respectively from 90Y-2IT-BAD-Lym-1. The tumor: body and tumor:bone marrow (by imaging) ratios were 16.4:1 and 5.8:1, respectively. In this Phase I study, 5/8 patients that failed prior chemotherapy had a partial response or stabilization of NHL after RIT. CONCLUSION: The safety and toxicity of 90Y-2IT-BAD-Lym-1 were determined and the MTD was 0.370 GBq/m2, a dose used in 4 patients. 90Y-2IT-BAD-Lym-1 may be useful for future clinical trials because 90Y is readily available and can deliver potent beta emissions to NHL. Bone marrow support however, will be required for further dose escalation.