Intraperitoneal radioimmunochemotherapy of ovarian cancer: a phase I study

CD44v6, STn & O-GD2: promising tumor associated antigens paving the way for new targeted cancer therapies

Targeted therapies are the state of the art in oncology today, and every year new Tumor-associated antigens (TAAs) are developed for preclinical research and clinical trials, but few of them really change the therapeutic scenario. Difficulties, either to find antigens that are solely expressed in tumors or the generation of good binders to these antigens, represent a major bottleneck. Specialized cellular mechanisms, such as differential splicing and glycosylation processes, are a good source of neo-antigen expression. Changes in these processes generate surface proteins that, instead of showing decreased or increased antigen expression driven by enhanced mRNA processing, are aberrant in nature and therefore more specific targets to elicit a precise anti-tumor therapy. Here, we present promising TAAs demonstrated to be potential targets for cancer monitoring, targeted therapy and the generation of new immunotherapy tools, such as recombinant antibodies and chimeric antigen receptor (CAR) T cell (CAR-T) or Chimeric Antigen Receptor-Engineered Natural Killer (CAR-NK) for specific tumor killing, in a wide variety of tumor types. Specifically, this review is a detailed update on TAAs CD44v6, STn and O-GD2, describing their origin as well as their current and potential use as disease biomarker and therapeutic target in a diversity of tumor types.

Targeting Tumor Glycans for Cancer Therapy: Successes, Limitations, and Perspectives

Simple Summary

Aberrant glycosylation is a common feature of many cancers, and it plays crucial roles in tumor development and biology. Cancer progression can be regulated by several physiopathological processes controlled by glycosylation, such as cell–cell adhesion, cell–matrix interaction, epithelial-to-mesenchymal transition, tumor proliferation, invasion, and metastasis. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs), which are suitable for selective cancer targeting, as well as novel antitumor immunotherapy approaches. This review summarizes the strategies developed in cancer immunotherapy targeting TACAs, analyzing molecular and cellular mechanisms and state-of-the-art methods in clinical oncology.

Abstract

Aberrant glycosylation is a hallmark of cancer and can lead to changes that influence tumor behavior. Glycans can serve as a source of novel clinical biomarker developments, providing a set of specific targets for therapeutic intervention. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs) suitable for selective cancer-targeting therapy. The best characterized TACAs are truncated O-glycans (Tn, TF, and sialyl-Tn antigens), gangliosides (GD2, GD3, GM2, GM3, fucosyl-GM1), globo-serie glycans (Globo-H, SSEA-3, SSEA-4), Lewis antigens, and polysialic acid. In this review, we analyze strategies for cancer immunotherapy targeting TACAs, including different antibody developments, the production of vaccines, and the generation of CAR-T cells. Some approaches have been approved for clinical use, such as anti-GD2 antibodies. Moreover, in terms of the antitumor mechanisms against different TACAs, we show results of selected clinical trials, considering the horizons that have opened up as a result of recent developments in technologies used for cancer control.

Radiopharmaceutical Switch Maintenance for Relapsed Ovarian Carcinoma

Switch maintenance, or using alternative therapeutic agents that were not administered during a prior course of cancer treatment, has emerged as an active clinical research and regulatory agency-approvable path in the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP) drug-development sequence. To better inform the design of therapeutic radiopharmaceutical trials, we reviewed academic scholarship discussing the clinical use of maintenance approaches to cancer treatment. Women with advanced-stage primary platinum-refractory or platinum-resistant ovarian carcinoma and their courses of treatment provide context for our discussion. Twenty-four (10%) out of 244 trials for women with ovarian carcinoma fit our search terms for maintenance trials. Five (2%) trials studied radiopharmaceuticals as switch maintenance. In our opinion, radiopharmaceutical switch maintenance merits further testing in prospective trials for women with advanced-stage primary platinum recurrent or refractory ovarian carcinoma.

Surgical immune interventions for solid malignancies

BACKGROUND

The purpose of this study was to systematically review clinically translatable immunotherapeutic agents that are delivered regionally for solid malignancies.

DATA SOURCES

PubMed and ClinicalTrials.gov were searched for published and registered clinical trials, respectively. The search yielded 334 relevant publications, of which 116 articles were included for review after exclusion criteria were applied.

CONCLUSIONS

There has been an increase in the regional administration of cell-based and viral vector-based clinical trials over the last 5 years. Surgical interventions have been developed for intrapleural, intracranial, intraperitoneal, and intratumoral routes of access to enhance the local delivery of these therapies. Multimodality therapies that combine regional immunotherapy with other local and systemic therapies are demonstrating continued growth as the field of immunotherapy continues to expand.

Radioactive antibodies: a historical review of selective targeting and treatment of cancer

Radioactive antibodies have served as imaging and therapeutic agents for several decades, but recent developments raise enthusiasm that a new generation of cancer therapeutics and diverse molecular imaging agents for various cancers are more likely than ever before. This article traces the development of tumor-targeting antibodies labeled with diagnostic or therapeutic radionuclides, and describes the problems encountered and the clinical advances made. We also emphasize recent attempts to improve both molecular imaging and radioimmunotherapy with multistep pretargeting methods that separate the delivery of the tumor-binding, bispecific antibody given in the first step from the radionuclide carrier, which, in the second step, will localize to the "anti-carrier" binding arm of the pretargeted bispecific antibody.

Targeted chemoradiation in metastatic colorectal cancer: a phase I trial of 131I-huA33 with concurrent capecitabine

huA33 is a humanized antibody that targets the A33 antigen, which is highly expressed in intestinal epithelium and more than 95% of human colon cancers but not other normal tissues. Previous studies have shown huA33 can target and be retained in a metastatic tumor for 6 wk but eliminated from normal colonocytes within days. This phase I study used radiolabeled huA33 in combination with capecitabine to target chemoradiation to metastatic colorectal cancer. The primary objective was safety and tolerability of the combination of capecitabine and (131)I-huA33. Pharmacokinetics, biodistribution, immunogenicity, and tumor response were also assessed.

METHODS

Eligibility included measurable metastatic colorectal cancer, adequate hematologic and biochemical function, and informed consent. An outpatient scout (131)I-huA33 dose was followed by a single-therapy infusion 1 wk later, when capecitabine was commenced. Dose escalation occurred over 5 dose levels. Patients were evaluated weekly, with tumor response assessment at the end of the 12-wk trial. Tumor targeting was assessed using a γ camera and SPECT imaging.

RESULTS

Nineteen eligible patients were enrolled. The most frequently observed toxicity included myelosuppression, gastrointestinal symptoms, and asymptomatic hyperbilirubinemia. Biodistribution analysis demonstrated excellent tumor targeting of the known tumor sites, expected transient bowel uptake, but no other normal tissue uptake. (131)I-huA33 demonstrated a mean terminal half-life and serum clearance suited to radioimmunotherapy (T1/2β, 100.24 ± 20.92 h, and clearance, 36.72 ± 8.01 mL/h). The mean total tumor dose was 13.8 ± 7.6 Gy (range, 5.1-26.9 Gy). One patient had a partial response, and 10 patients had stable disease.

CONCLUSION

(131)I-huA33 achieves specific targeting of radiotherapy to colorectal cancer metastases and can be safely combined with chemotherapy, providing an opportunity to deliver chemoradiation specifically to metastatic disease in colorectal cancer patients.

Novel therapies for recurrent ovarian cancer management

The search for novel therapies has resulted in a number of biologic agents that target cellular processes and molecules involved in ovarian carcinogenesis. These drugs include cytokines, monoclonal antibodies, vaccines, protease inhibitors and gene replacement systems. Many of these have been evaluated in Phase I/II trials and are currently being investigated in Phase III trials. This paper will review the progress of and ongoing clinical studies evaluating the potential utility of these new agents in patients affected with ovarian cancer. Further development and investigation of these agents may eventually lead to a combination of treatments that ultimately results in improved survival for patients with ovarian cancer.

Predictors of long-term outcome from intraperitoneal radioimmunotherapy for ovarian cancer

Data was analyzed from 92 patients >  5 years after intraperitoneal (IP) radionuclide therapy (RIT) with (90)Y- or (177)Lu-CC49 to determine prognostic factors. Patients had CC49 antibody-reactive ovarian cancer confined to the abdominal cavity after primary debulking and chemotherapy. The first 27 patients received IP (177)Lu-CC49 alone; the remainder received Interferon (IFN), to increase the expression of the tumor-associated glycoprotein-72 (TAG-72) antigen, +/- IP paclitaxel (25-100 mg/m(2)) 2 days before RIT. Factors assessed by univariate (and some multivariate) analysis included age, race, body size, interval between initial diagnosis and RIT, interval between 2nd look surgery and RIT, (90)Y versus (177)Lu, MBq dose, paclitaxel dose, grade of tumor, extent of initial surgery, size of disease deposits prior to RIT, intensity of TAG reactivity, the addition of unlabeled antibody, and the development of human anti-mouse antibody and/or serum sickness after murine antibody. A statistically significant improvement in progression-free survival (p ≤ 0.05) was noted for less bulky disease and younger age. Administration of paclitaxel plus IFN, an immune response, and use of (90)Y showed a favorable nonsignificant trend. Dose escalation of radionuclide did not change risk of progression; thus, this therapy may have therapeutic efficacy at modest dose levels.

Dose intensified molecular targeted radiotherapy for cancer-lymphoma as a paradigm

Although most patients with locoregional cancer are cured by surgery, radiotherapy, chemotherapy, and combinations thereof, those with distant metastases are not despite systemic chemotherapy. These patients respond to local radiotherapy but generally need systemic therapy. Non-Hodgkin's lymphoma (NHL) provides a paradigm for the role of molecular targeted radiotherapy (MTRT) because these patients have multifocal disease in most cases. Although patients with NHL achieve remissions after multiple cycles of chemotherapy, less than one half of those with aggressive NHL are cured and almost none of those with low grade NHL. Furthermore, NHL, like other cancers, becomes chemoresistant, yet remains responsive to radiotherapy. MTRT, radiation targeted by molecules, is a good strategy for the treatment of multifocal and radiosensitive cancers. Radioimmunotherapy (RIT) is an MTRT approach using MAbs, or parts thereof, to target the radionuclide that delivers radiation. Two anti-CD20 monoclonal antibodies (MAbs), one labeled with (111)In for imaging or (90)Y for therapy and a second labeled with (131)I for imaging and therapy, have proven effective and safe for MTRT for NHL patients. The importance of the radiation is demonstrated in the data from the randomized pivotal trial of (90)Y-ibritumomab; response rates were distinctly better in the (90)Y-ibritumomab arm than in the rituximab arm. Furthermore, the efficacy of (131)I-tositumomab was greater than that of the same MAb alone in another pivotal trial. Although hematologic toxicity is dose limiting for MTRT, febrile neutropenia is uncommon. MTRT is also not associated with mucositis, hair loss, or persistent nausea or vomiting, unlike chemotherapy. Randomized trials of MTRT in different strategies have not been conducted, but there is evidence of better outcomes, particularly for strategies that provide dose intensification, such as pretargeted MTRT, multiple dosing ("fractionation"), and MTRT with stem cell transplantation (SCT). Pretargeted RIT separates delivery of the targeting molecule from radionuclide delivery, provides dose escalation, and is more effective than direct one-step RIT, although more complicated to implement. Improved drugs and strategies for MTRT have documented potential for better patient outcomes. Smaller radionuclide carriers, such as those used for pretargeted MTRT, should be incorporated into the management of patients with NHL and other cancers soon after the patients have proven incurable. Expected improvements using better drugs, strategies, and combinations with other drugs seem likely to make MTRT integral in the management of many patients with cancer and likely to lead to cures of NHL.

Intraperitoneal Alpha-Radioimmunotherapy of Advanced Ovarian Cancer in Nude Mice Using Different High Specific Activities

Background

The aim of this study was to investigate the therapeutic efficacy of advanced ovarian cancer in mice, using α-radioimmunotherapy with different high specific activities. The study was performed using the monoclonal antibody (mAb) MX35 F(ab′)2 labeled with the α-particle emitter ²¹¹At.

Methods

Animals were intraperitoneally inoculated with ≥1 × 10⁷ cells of the ovarian cancer cell line NIH:OVCAR-3. Four weeks later 9 groups of animals were given 25, 50, or 400 kBq ²¹¹At-MX35 F(ab′)2 with specific activities equal to 1/80, 1/500, or 1/1200 (²¹¹At atom/number of mAbs) for every activity level respectively (n = 10 in each group). As controls, animals were given PBS or unlabeled MX35 F(ab′)2 in PBS (n = 10 in each group). Eight weeks after treatment the animals were sacrificed and the presence of macroscopic tumors was determined by meticulous ocular examination of the abdominal cavity. Cumulated activity and absorbed dose calculations on tumor cells and tumors were performed using in house developed program. Specimens for scanning electron-microscopy analysis were collected from the peritoneum at the time of dissection.

Results

Summing over the different activity levels (25, 50, and 400 kBq ²¹¹At-MX35 F(ab′)2) the number of animals with macroscopic tumors was 13, 17, and 22 (n = 30 for each group) for the specific activities equal to 1/80, 1/500, or 1/1200, respectively. Logistic-regression analysis showed a significant trend that higher specific activity means less probability for macroscopic tumors (P = 0.02).

Conclusions

Increasing the specific activity indicates a way to enhance the therapeutic outcome of advanced ovarian cancer, regarding macroscopic tumors. Further studies of the role of the specific activity are therefore justified.

Intraperitoneal alpha-radioimmunotherapy in mice using different specific activities

PURPOSE

The aim of this study was to investigate the therapeutic efficacy of the alpha-radioimmunotherapy of ovarian cancer in mice, using different specific activities. This study was performed by using the monoclonal antibody, MX35 F(ab')(2), labeled with the alpha-particle-emitter, 211At.

METHODS

Animals were intraperitoneally inoculated with approximately 1 x 10(7) cells of the cell line, NIH:OVCAR-3. Four (4) weeks later, five groups of animals were given 400 kBq of 211At-MX35 F(ab')(2) with specific activities equal to 130, 65, 32, 16, or 4 kBq/microg, respectively (n = 18 in each group). As controls, animals were given unlabeled MX35 F(ab')(2) (n = 12). Eight (8) weeks after treatment, the animals were sacrificed and the presence of macro- and microscopic tumors and ascites was determined.

RESULTS

The tumor-free fractions (TFFs) of the animals, defined as the fraction of animals with no macro- and microtumors and no ascites, were 0.67, 0.73, 0.50, 0.50, and 0.17 when treated as above. Only the TFF of 0.17, for the specific activity of 4 kBq/microg, was significantly less, compared to that of the specific activity of 130 kBq/microg. The TFF for the specific activity of 4 kBq/microg showed a significant lowering, compared to the specific activity of 130 kBq/microg (p < 0.05). Treatment with unlabeled MX35 F(ab')(2) resulted in a TFF of zero.

CONCLUSIONS

A specific activity-dependent therapeutic outcome could not be shown in the interval of 130- to 16 kBq/mug. For lower specific activities (i.e., 4 kBq/microg), the therapeutic efficacy was significantly lowered.

Biodistribution of HuCC49DeltaCH2-beta-galactosidase in colorectal cancer xenograft model

Antibody-enzyme conjugate (AbE) has been widely studied for site-specific prodrug activation in tumors. The purpose of this study is to characterize the pharmacokinetics and tissue distribution of HuCC49DeltaCH2-beta-galactosidase conjugate. HuCC49DeltaCH2 and beta-galactosidase were chemically conjugated and injected into a LS 174T colon cancer xenograft model. A colorimetric assay was developed to quantify the HuCC49DeltaCH2-beta-galactosidase levels in plasma and tissues. The HuCC49DeltaCH2-beta-galactosidase conjugate distributed into tumor tissue as early as 6h with the tumor/blood ratio of 5. This favored distribution of conjugate activity in the tumor tissue which was maintained up to 4 days post conjugate injection, while the conjugate was cleared rapidly from blood and other normal tissues (heart, spleen, lung, liver, kidney and stomach). At a high dose of 3000 U/kg, HuCC49DeltaCH2-beta-galactosidase conjugate saturated the antigen binding sites and yielded decreased tumor/normal tissue ratios compared to 1500 U/kg. These data suggest that HuCC49DeltaCH2-beta-galactosidase specifically target to the tumors to increase tumor selectivity.

Repeated Intraperitoneal alpha-Radioimmunotherapy of Ovarian Cancer in Mice

The aim of this study was to investigate the therapeutic efficacy of α-radioimmunotherapy of ovarian cancer in mice using different fractionated treatment regimens. The study was performed using the monoclonal antibody MX35 F(ab′)₂ labeled with the α-particle emitter ²¹¹At. Methods. Nude mice were intraperitoneally inoculated with ~1 × 10⁷ cells of the cell line NIH:OVCAR-3. Four weeks later 6 groups of animals were given 400 kBq ²¹¹At-MX35 F(ab′)₂ as a single or as a repeated treatment of up to 6 times (n = 18 in each group). The fractionated treatments were given every seventh day. Control animals were treated with unlabeled MX35 F(ab′)₂ (n = 12). Eight weeks posttreatment the animals were sacrificed and the presence of macro- and microscopic tumors and ascites was determined. Results. The tumor-free fractions (TFFs) of the animals, defined as the fraction of animals with no macro- and microtumors and no ascites, were 0.17, 0.11, 0.39, 0.44, 0.44, and 0.67 when treated with 400 kBq ²¹¹At-MX35 F(ab′)₂ once or 2, 3, 4, 5, or 6 times, respectively. Repeated treatment 3 times or more resulted in a significantly higher (P < .05) TFF than compared to treatment once or twice. The presence of ascites decreased from 15 out of 18 animals in the group given only one treatment to zero for the 2 groups given 5 or 6 fractions. Treatment with unlabeled MX35 F(ab′)₂ resulted in a TFF of zero. Conclusion. Weekly repeated intraperitoneal injections of tolerable amounts of activity of ²¹¹At-MX35 F(ab′)₂ of up to 6 times produced increased therapeutic efficacy without observed toxicity, indicating a potential increase of the therapeutic index.

Radiolanthanides in endoradiotherapy: an overview

Endoradiotherapy (targeted radionuclide therapy) is a systemic approach, involving a radiolabeled targeting vector with a well characterized biochemical strategy to selectively deliver a cytotoxic level of radiation to a disease site on a cellular/molecular level. The group of radiolanthanides has been considered both for imaging and therapy over many years. Some radiolanthanides have been and are increasingly applied for therapeutic purposes.

However, the clinical use of endoradiotherapeuticals containing radiolanthanides requires a complex and interdisciplinary approach. It involves, among other factors, the choice of the most suitable lanthanide radionuclide (in terms of nuclear decay parameters such as type and energy of the particles emitted, half-life, decay products etc.); the identification of the most promising production route; the determination of the relevant production parameters such as excitation functions, nuclear reaction yields, radionuclidic purities, specific activities etc.; the chemical isolation of the radiolanthanide produced from the target material (except the (n, γ) production route); the synthesis of the labelling precursor, and labelling of the precursor and the chemical purification and isolation of the labelled radiotherapeutical, ready for i.v. injection; and finally the investigation of pharmacological targeting parameters of the labelled radiotherapeutical in vitro and in vivo (animal experiments).

Therapeutic efficacy of 177Lu-CHX-A''-DTPA-hu3S193 radioimmunotherapy in prostate cancer is enhanced by EGFR inhibition or docetaxel chemotherapy

BACKGROUND

This study investigated the biodistribution and therapeutic efficacy of Lutetium-177 (177Lu) radiolabeled anti-Lewis Y monoclonal antibody hu3S193 radioimmunotherapy (RIT) in mice bearing prostate cancer xenografts. The ability of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 and docetaxel chemotherapy to enhance the efficacy of RIT was also assessed in vivo.

METHODS

The in vitro cytotoxicity of 177Lu labeled hu3S193 on Le(y) positive DU145 prostate cancer cells was assessed using proliferation assays, with induction of apoptosis measured by ELISA. The in vivo biodistribution and tumor localization of 177Lu-hu3S193 was assessed in mice bearing established DU145 tumor xenografts. The efficacy and maximum tolerated dose of 177Lu-hu3S193 RIT in vivo was determined by a dose escalation study. EGFR inhibitor AG1478 or docetaxel chemotherapy was administered at sub-therapeutic doses in conjunction with RIT in vivo.

RESULTS

177Lu-hu3S193 mediated significant induction of cytotoxicity and apoptosis in vitro. In vivo analysis of 177Lu-hu3S193 biodistribution demonstrated specific targeting of DU145 prostate cancer xenografts, with maximal tumor uptake of 33.2 +/- 3.9%ID/g observed at 120 hr post-injection. In RIT studies, 177Lu-hu3S193 caused specific and dose-dependent inhibition of prostate cancer tumor growth. A maximum tolerated dose of 350 microCi was determined for 177Lu-hu3S193. Combination of 177Lu-hu3S193 RIT with EGFR inhibitor AG1478 or docetaxel chemotherapy both significantly improved efficacy.

CONCLUSIONS

177Lu-hu3S193 RIT is effective as a single agent in the treatment of Le(y) positive prostate cancer models. The enhancement of RIT by AG1478 or docetaxel indicates the promise of combined modality strategies.

Systemic radiotherapy can cure lymphoma: a paradigm for other malignancies?

The cytocidal potency of a molecule can be augmented by conjugating a radionuclide for molecular targeted radionuclide therapy (MTRT) for cancer. Radioimmunotherapy (RIT) should be incorporated into the management of patients with B-cell non-Hodgkin's lymphoma (NHL) soon after the patients have proven incurable. Better drugs, strategies, and combinations with other drugs seem certain to make RIT integral to the management of patients with NHL and likely to lead to a cure of the currently incurable NHL. These improved drugs, strategies, and combinations thereof also offer opportunities for RIT to become part of the management of solid malignancies, including epithelial cancers. Smaller radionuclide carriers, such as those used for pretargeted strategies, provide dose intensification. The potential of pretargeted RIT to improve patient outcomes is striking.

Intracavitary radioimmunotherapy to treat solid tumors

Radioimmunotherapy (RIT) potentially is an attractive treatment for radiosensitive early-stage solid tumors and as an adjuvant to cytoreductive surgery. Topical administration of RIT may improve the efficacy because higher local concentrations are achieved. We reviewed the results of locally applied radiolabeled monoclonal antibodies for the treatment of solid tumors. Intracavitary RIT in patients with ovarian cancer and glioma showed improved targeting after local administration, as compared to the intravenous administration. In addition, various studies showed the feasibility of locally applied RIT in these patients. In studies that included patients with small-volume disease, adjuvant RIT in ovarian cancer and glioma showed to be at least as effective as standard therapy. The information about RIT for peritoneal carcinomatosis of colorectal origin is scarce, while results from preclinical data are promising. RIT may be applied for other, relatively unexplored indications. Studies on the application of radiolabeled antibodies in early urothelial cell cancer have been performed, showing that intracavitary RIT may hold a promise. Moreover, in patients with malignant pleural mesothelioma or malignant pleural effusion, RIT may play a role in the palliative treatment. Intracavitary RIT limits toxicity and improves tumor targeting. RIT is more effective in patients with small-volume disease of solid cancers. RIT may have potential for palliation in patients with malignant pleural mesothelioma or malignant pleural effusion. The future of RIT may, therefore, not only be in the inclusion in contemporary multimodality treatment, but also in the expansion to palliative treatment.

Production of 177Lu at the new research reactor FRM-II: Irradiation yield of 176Lu177Lu

Due to its physical and chemical characteristics, 177Lu is a very attractive radionuclide for use in nuclear medicine. This paper introduces a method for a precise calculation of the irradiation yield of 177Lu produced by neutron activation of 176Lu in a nuclear reactor. The calculation is based on the Westcott convention which requires the knowledge of the neutron flux parameters. In this work, the neutron flux parameters of the new research reactor FRM-II (Garching, Germany) were determined and the stability of thermal neutron flux and thermal neutron flux temperature was monitored. The comparison of theoretically calculated and experimentally determined yield for Lu176(n,gamma)Lu177 reaction is presented.

Administered activity and metastatic cure probability during radioimmunotherapy of ovarian cancer in nude mice with 211At-MX35 F(ab')2

PURPOSE

To elucidate the therapeutic efficacy of alpha-radioimmunotherapy of ovarian cancer in mice. This study: (i) estimated the minimum required activity (MRA), giving a reasonable high therapeutic efficacy; and (ii) calculated the specific energy to tumor cell nuclei and the metastatic cure probability (MCP) using various assumptions regarding monoclonal-antibody (mAb) distribution in measured tumors. The study was performed using the alpha-particle emitter Astatine-211 (211At) labeled to the mAb MX35 F(ab')2.

METHODS AND MATERIALS

Animals were inoculated intraperitoneally with approximately 1 x 10(7) cells of the cell line NIH:OVCAR-3. Four weeks later animals were treated with 25, 50, 100, or 200 kBq 211At-MX35 F(ab')2 (n = 74). Another group of animals was treated with a nonspecific mAb: 100 kBq 211At-Rituximab F(ab')2 (n = 18). Eight weeks after treatment the animals were sacrificed and presence of macro- and microscopic tumors and ascites was determined. An MCP model was developed and compared with the experimentally determined tumor-free fraction (TFF).

RESULTS

When treatment was given 4 weeks after cell inoculation, the TFFs were 25%, 22%, 50%, and 61% after treatment with 25, 50, 100, or 200 kBq (211)At-MX35 F(ab')2, respectively, the specific energy to irradiated cell nuclei varying between approximately 2 and approximately 400 Gy.

CONCLUSION

As a significant increase in the therapeutic efficacy was observed between the activity levels of 50 and 100 kBq (TFF increase from 22% to 50%), the conclusion was that the MRA is approximately 100 kBq (211)At-MX35 F(ab')2. MCP was most consistent with the TFF when assuming a diffusion depth of 30 mum of the mAbs in the tumors.

Technological advances in radioimmunotherapy

Radioimmunotherapy (RIT) is a method of selectively delivering radionuclides with toxic emissions to cancer cells, while reducing the dose to normal tissues. Although primary tumours can often be treated successfully with external beam radiotherapy or surgery, metastases often escape detection and treatment, leading to therapy failure, and these can be treated with systemic targeted therapies such as RIT. This review describes more recent developments in the field, including both technological developments from the laboratory and increasingly encouraging findings from clinical studies.

Novel radiolabeled antibody conjugates

This article reviews the development of radioimmunoconjugates as a new class of cancer therapeutics. Numerous conjugates involving different antigen targets, antibody forms, radionuclides and methods of radiochemistry have been studied in the half-century since radioactive antibodies were first used in model systems to selectively target radiation to tumors. Whereas directly conjugated antibodies, fragments and subfragments have shown promise preclinically, the same approaches have not gained success in patients except in radiosensitive hematological neoplasms, or in settings involving minimal or locoregional disease. The separation of tumor targeting from the delivery of the therapeutic radionuclide in a multistep process called pretargeting has the potential to overcome many of the limitations of conventional, or one-step, radioimmunotherapy, with initial preclinical and clinical data showing increased sensitivity, specificity and higher radiation doses delivered. Our particular focus in pretargeting is the use of bispecific, trimeric (three Fab's) constructs made by a new antibody engineering method termed 'dock-and-lock.

Combined staining of TAG-72, MUC1, and CA125 improves labeling sensitivity in ovarian cancer: antigens for multi-targeted antibody-guided therapy

Single antigen-targeted intraperitoneal radioimmunotherapy for ovarian cancer has shown limited success. Due to the heterogeneous expression of tumor antigens on cancer cells, a multi-antigen targeting approach appears logical to augment the therapeutic efficacy of antibody-guided therapy. In the interest of developing this novel approach, ovarian cancer tissue microarray slides containing cancer and benign/non-neoplastic tissue samples (n=92) were processed for single-, double-, and triple-antigen labeling using antibodies for the tumor-associated antigens TAG-72, MUC1, and CA125. Among all ovarian cancer types, 72%, 61%, and 50% of the samples showed immunolabeling for TAG-72, MUC1, and CA125, respectively. Expression level of these antigens was significantly (p<0.005) higher in advanced stage carcinomas compared with early stage. Of the 48 epithelial ovarian cancer samples, individual anti-TAG-72, MUC1, and CA125 antibody probing showed labeling in 89.5%, 87.5%, and 73.0% of the cases, respectively. In the majority of the cancer samples (>70%), a heterogeneous labeling pattern was observed (only 30-40% of the cancer cells within the sample were labeled). However, upon combining the three antigens (triple-antigen labeling), 98% of the epithelial ovarian cancer samples were labeled and >95% of the cancer cells within each sample were labeled. Our data indicate that the heterogeneous expression of cancer antigens appears to be a major obstacle in antibody-guided therapy, and this can be overcome by multiple antigen targeting. Therapeutic efficacy of antibody-guided therapy for ovarian cancer treatment will be enhanced by the combined targeting of TAG-72, MUC1, and CA125.

Construction and evaluation of the tumor imaging properties of 123I-labeled recombinant and enzymatically generated Fab fragments of the TAG-72 monoclonal antibody CC49

Tumor-associated glycoprotein-72 (TAG-72) is overexpressed in a high percentage of epithelial cancers and has proven useful as a target for imaging and targeted radiotherapy. Our goal was to express a recombinant Fab (rFab) of the TAG-72 monoclonal antibody CC49 in Pichia pastoris and directly compare its tumor and normal tissue uptake and imaging properties with enzymatically generated Fab (eFab). In this study, the genes coding for CC49 Fab were cloned from hybridoma cells and expressed in P. pastoris. Fab was purified to homogeneity and its immunoreactivity toward bovine submaxillary mucin (TAG-72) confirmed by ELISA. The tumor and normal tissue localization of (123)I-CC49 rFab and eFab were compared in athymic mice bearing s.c. LS174T colon cancer or TAG-72-negative A375 melanoma xenografts. Results showed that pure and immunoreactive rFab of CC49 was produced and labeled with (123)I. At 24 h post i.v. injection (p.i.), tumor uptake for (123)I-rFab in LS174T xenografts was 6.0% ID/g which was 18-fold higher than in A375 tumors. Tumor-to-normal tissue ratios increased between 2 and 24 h and exceeded 5:1 at 24 h p.i. of (123)I-rFab. (123)I-rFab exhibited significantly lower liver uptake at 12 h p.i. and lower kidney uptake at 2 h p.i. than (123)I-eFab. LS174T tumors were imaged as early as 2 h after administration of (123)I-rFab. We conclude that CC49 rFab can be produced in a P. pastoris host system and accumulated at comparable levels as eFab in LS174T colon cancer xenografts in mice. The lower liver uptake of (123)I-rFab as compared with eFab suggests that it may be more useful for imaging liver lesions. No major effect, except for kidneys and liver, was observed on tumor and normal tissue uptake due to introduction of hexahistidine and FLAG affinity tags or peptide linkers in the scaffold of rFab.

Cancer Imaging and Therapy with Bispecific Antibody Pretargeting

This article reviews recent preclinical and clinical advances in the use of pretargeting methods for the radioimmunodetection and radioimmunotherapy of cancer. Whereas directly-labeled antibodies, fragments, and subfragments (minibodies and other constructs) have shown promise in both imaging and therapy applications over the past 25 years, their clinical adoption has not fulfilled the original expectations due to either poor image resolution and contrast in scanning or insufficient radiation doses delivered selectively to tumors for therapy. Pretargeting involves the separation of the localization of tumor with an anticancer antibody from the subsequent delivery of the imaging or therapeutic radionuclide. This has shown improvements in both imaging and therapy by overcoming the limitations of conventional, or 1-step, radioimmunodetection or radioimmunotherapy. We focus herein on the use of bispecific antibodies followed by radiolabeled peptide haptens as a new modality of selective delivery of radionuclides for the imaging and therapy of cancer. Our particular emphasis in pretargeting is the use of bispecific trimeric (3 Fab's) recombinant constructs made by a modular method of antibody and protein engineering of fusion molecules called Dock and Lock (DNL).

Alpha v beta 3 integrin-targeting of intraperitoneally growing tumors with a radiolabeled RGD peptide

Ovarian cancer is the fourth most common cause of cancer deaths among females in the western world after cancer of the breast, colon and lung. The inability to control the disease within the peritoneal cavity is the major cause of treatment failure in patients with ovarian cancer. The majority of ovarian carcinomas express the alpha(v)beta(3) integrin. Here we studied the tumor targeting potential of an (111)In-labeled cyclic RGD peptide in athymic BALB/c mice with intraperitoneally (i.p.) growing NIH:OVCAR-3 human ovarian carcinoma tumors. The cyclic RGD peptide, c(RGDfK)E, was synthesized, conjugated with DOTA and radiolabeled with (111)In. The targeting potential of (111)In-DOTA-E-c(RGDfK) was studied in athymic mice with i.p. growing NIH:OVCAR-3 xenografts and the optimal dose of this compound was determined (0.01 microg up to 10 microg). The biodistribution at optimal peptide dose was determined at various time points (0.5 up to 72 hr). Furthermore, the therapeutic potential of (177)Lu-DOTA-E-c(RGDfK) was studied in this model. Two hours after i.p. administration, (111)In-DOTA-E-c(RGDfK) showed high and specific uptake in the i.p. growing tumors. Optimal uptake in the i.p. growing tumors was observed at a 0.03-0.1 microg dose range. Tumor uptake of (111)In-DOTA-E-c(RGDfK) peaked 4 hr p.i. [(38.8 +/- 2.7)% ID/g], gradually decreasing at later time points [(24.0 +/- 4.1)% ID/g at 48 hr p.i.]. Intraperitoneal growth of OVCAR-3 could be significantly delayed by injecting 37 MBq (177)Lu-labeled peptide i.p. Radiolabeled DOTA-E-c(RGDfK) is suitable for targeting of i.p. growing tumors and potentially can be used for peptide receptor radionuclide therapy of these tumors.

Radioimmunotherapy for non-Hodgkin's lymphoma

OBJECTIVES

To describe the rationale for radioimmunotherapy as a treatment of non-Hodgkin's lymphoma. To present the similarities and differences in the two radioimmunotherapies and the nursing implications in caring for patients receiving these agents.

DATA SOURCES

Published literature and review of published clinical trials.

CONCLUSION

Radiolabeled monoclonal antibodies bind to specific antigens and provide a means of targeting tumor cells with cytotoxic radioactivity. The infusion of radiolabeled monoclonal antibodies requires an understanding of antibody therapy, radiation therapy, and principles of time, distance, and shielding.

IMPLICATIONS FOR NURSING PRACTICE

As the use of radioimmunotherapy grows, nurses must be aware of the background for, logistics of, and follow-up required for patients receiving this form of radiation treatment.

Targeted radionuclide therapy for solid tumors: an overview

Although radioimmunotherapy (RIT) has been effective in non-Hodgkin's lymphoma (NHL) as a single agent, solid tumors have shown less clinically significant therapeutic response to RIT alone. The clinical impact of RIT or other forms of targeted radionuclide therapy for solid tumors depends on the development of a high therapeutic index (TI) for the tumor vs. normal tissue effect, and the implementation of RIT as part of synergistic combined modality therapy (CMRIT). Preclinical and clinical studies have provided a wealth of information, and new prototypes or paradigms have shed light on future possibilities in many instances. Evidence suggests that combination and sequencing of RIT in CMRIT appropriately can provide effective treatment for many solid tumors. Vascular targets provide RIT enhancement opportunities and nanoparticles may prove to be effective carriers for RIT combined with intracellular drug delivery or alternating magnetic frequency (AMF) induced thermal tumor necrosis. The sequence and timing of combined modality treatments will be of critical importance to achieve synergy for therapy while minimizing toxicity. Fortunately, the radionuclide used for RIT also provides a signal useful for nondestructive quantitation of the influence of sequence and timing of CMRIT on events in animals and patients. This can be readily accomplished clinically using quantitative high-resolution imaging (e.g., positron emission tomography [PET]).

Systemic targeted radionuclide therapy: potential new areas

Radiation oncology is entering an exciting new era with therapies being delivered in a targeted fashion through an increasing number of novel approaches. External beam radiotherapy now integrates functional and anatomic tumor imaging to guide delivery of conformal radiation to the tumor target. Systemic targeted radionuclide therapy (STaRT) adds an important new dimension by making available to the radiation oncologist biologically targeted radiation therapy. Impressive clinical results with antibody-targeted radiotherapy, leading to the Food and Drug Administration's approval of two anti-CD20 radiolabeled antibodies, highlight the potential of STaRT. Optimization strategies will further improve the efficacy of STaRT by improving delivery systems, modifying the tumor microenvironment to increase targeted dose, and maximizing dose effect. Ultimately, the greatest potential for STaRT will not be as monotherapy, but as therapy integrated into established multimodality regimens and used as adjuvant or consolidative therapy in patients with minimal or micrometastatic disease.

Fractionated radioimmunotherapy of intraperitoneally growing ovarian cancer in nude mice with 211At-MX35 F(ab')2: therapeutic efficacy and myelotoxicity

OBJECTIVE

The aim of this study was to investigate the therapeutic efficacy and myelotoxicity during fractionated radioimmunotherapy of ovarian cancer in mice. The study was performed using the monoclonal antibody MX35 F(ab')(2) labeled with the alpha-particle emitter (211)At.

METHODS

Animals were intraperitoneally inoculated with approximately 1x10(7) cells of the cell line NIH:OVCAR-3. Four weeks later, the mice were given the first treatment. Six groups of animals were intraperitoneally injected with approximately 800, 3x approximately 267, approximately 400, 3x approximately 133, approximately 50 or 3x approximately 17 kBq (211)At-MX35 F(ab')(2) (n=18 in each group). The second and third injections for Groups 2, 4 and 6 were given 4 and 8 days after the first injection, respectively. As controls, animals were treated with unlabeled MX35 F(ab')(2) (n=12). Eight weeks after the last injection, the animals were sacrificed and the presence of macro- and microscopic tumors and ascites was determined. Blood counts were determined for each mouse in Groups 1 and 2 before the first injection and 3, 7, 11, 15 and 23 days after the first injection. The calculation of the mean absorbed dose to the bone marrow was based on the ratio between the (211)At-activity concentration in bone and blood [i.e., the bone-to-blood ratio (BBLR)] as well as that between the (211)At-activity concentration in bone marrow and blood [i.e., the bone-marrow-to-blood ratio (BMBLR)] and the cumulated activity and absorbed fraction of the alpha-particles emitted by (211)At in the bone marrow.

RESULTS

The tumor-free fractions of animals were 56% and 41% when treated with approximately 800 kBq and 3x approximately 267 kBq (211)At-MX35 F(ab')(2), respectively; 39% and 28% when treated with approximately 400 kBq and 3x approximately 133 kBq (211)At-MX35 F(ab')(2), respectively; and 17% and 22% when treated with approximately 50 kBq or 3x approximately 17 kBq (211)At-MX35 F(ab')(2), respectively. The nadir of the white blood cell (WBC) counts was decreased (from 46% to 19%, compared with the baseline WBC counts) and delayed (from Day 4 to Day 11 after the first injection) during the fractionated treatment compared with the single-dose treatment. The percentage of injected activity per gram (%IA/g) for blood, bone and bone marrow all peaked 6 h after injection at 13.80+/-1.34%IA/g, 4.00+/-0.69%IA/g and 8.28+/-1.38%IA/g, respectively. The BBLR and BMBLR were 0.20+/-0.04 and 0.58+/-0.01, respectively. The mean absorbed dose to bone marrow was approximately 0.4 Gy after intraperitoneally injecting approximately 800 kBq (211)At-MX35 F(ab')(2).

CONCLUSION

No advantage was observed in the therapeutic efficacy of using a fractionated regimen compared with a single administration, with the same total amount of administered activity. Alleviation of the myelotoxicity was observed during the fractionated regimen in terms of decreased suppression and delayed nadir of the WBC counts. No thrombocytopenia was observed during either regimen.

A phase I trial of (90)Y-DOTA-anti-CEA chimeric T84.66 (cT84.66) radioimmunotherapy in patients with metastatic CEA-producing malignancies

PURPOSE/OBJECTIVE

Previous radioimmunotherapy (RIT) clinical trials at this institution with (90)Y-labeled cT84.66 anti-CEA (carcinoembryonic antigen) evaluated the antibody conjugated to diethylenetriaminepentaacetic acid (DTPA). The aim of this phase I therapy trial was to evaluate cT84.66 conjugated to the macrocyclic chelate (90)Y-DOTA and labeled with (90)Y in a comparable patient population.

EXPERIMENTAL DESIGN

Patients with metastatic CEA-producing cancers were entered in this trial. If antibody targeting to tumor was observed after the administration of (111)In-DTPA cT84.66, the patient then received the therapy infusion of (90)Y-DOTA-cT84.66 1 week later. Serial nuclear scans, blood and urine collections, and computed tomography (CT) scans were performed to assess antibody biodistribution, pharmacokinetics, toxicities, and antitumor effects.

RESULTS

Thirteen (13) patients were treated in this study. Dose-limiting hematologic toxicity was experienced at initial starting activity levels of 12 and 8 mCi/m(2). Subsequent patients received systemic Ca-DTPA at 125 mg/m(2) every 12 hours for 3 days post-therapy to allow for a dose escalation to 16 mCi/m(2), where hematologic toxicity was observed with an associated maximum tolerated dose (MTD) of 13.4 mCi/m(2). Tumor doses ranged from 4.4 to 569 cGy/mCi, which translated to 97-12,500 cGy after a single infusion of (90)Y-DOTA-cT84.66. Human anti-chimeric antibody (HACA) response developed in 8 of 13 patients and prevented additional therapy in 4 patients.

CONCLUSIONS

This study demonstrates the feasibility of using (90)Y-DOTA-cT84.66 for antibody-guided radiation therapy. Immunogenicity of the DOTA-conjugated cT84.66 antibody was not appreciably greater than that observed with (90)Y-DTPA-cT84.66 in previous trials. Dose-limiting hematopoietic toxicity with (90)Y-DOTA-cT84.66 decreased with Ca-DTPA infusions post-therapy and appears to be comparable to previously published results for (90)Y-DTPA-cT84.66. The highest antibody uptake and tumor doses were to small nodal lesions, which supports the predictions from preclinical and clinical data that RIT may be best applied in the minimal tumor burden setting.

Emerging drugs for ovarian cancer

Because most patients presenting with advanced ovarian cancer are not curable by surgery alone, chemotherapy represents an essential component of treatment. The disease may be considered as chemosensitive, as in around three-quarters of patients major (complete) responses are seen to initial treatment with the platinum-containing drugs cisplatin and carboplatin either used alone or in combination with the taxane, paclitaxel. However, only 15-20% of patients experience long-term remission as tumours often become resistant. The probability of achieving a second response depends on the duration of remission after first-line therapy: if this is < 6 months (considered as platinum resistant) second responses are uncommon and usually short-lived; if this is > 6, and especially if > 12 months (platinum sensitive), responses may be seen in about a quarter of patients, to the same drugs as used first line or to drugs such as pegylated liposomal doxorubicin, topotecan and hexamethylmelamine (all three are approved in this setting by the FDA). Gemcitabine, oral etoposide, docetaxel and oxaliplatin also show some activity either in sequential addition to existing approved of first-line therapy (as with gemcitabine) or as second-line therapy. However, there is an urgent unmet clinical need for new drugs capable of prolonging survival either by increasing long-term remission rates and/or duration as first-line treatment or to improve on outcomes of second-line treatment. Strategies currently being exploited in clinical trials include attempts to deliver more killing selectively to tumours (e.g., intraperitoneal administration of cisplatin or radiolabelled monoclonal antibodies), agents designed to target drug resistance mechanisms (e.g., TLK-286 activated by glutathione transferase), agents targeting proteins/receptors shown to be selectively expressed in the disease (e.g., monoclonal antibodies recognising CA-125 or HER1; small molecules targeting HER1 such as gefitinib) and disrupting established tumour vasculature (e.g., 5,6-dimethyl xanthenone 4-acetic acid). At the pre-clinical level, agents being developed to target the phosphatidylinositol 3 kinase/AKT/mTOR pathway, and K-Ras inhibitors, may offer efficacy in the future.

Review of clinical radioimmunotherapy

Radioimmunotherapy involves a form of biologically targeted radiopharmaceutical treatment in which a radioactive isotope (typically a short-range, high-energy beta-emitter) is chemically bound to a target-specific monoclonal antibody or fragment. Thus, these radioimmunoconjugates combine the exquisite targeting specificity of the humoral immune system with the known cancer-killing power of high-energy radiotherapy. To date, two radioimmunotherapy agents have been fully approved for commercial use: 90Yttrium ibritumomab tiuxetan and (131)Iodine tositumomab. Both compounds target the CD20 surface molecule found on normal and malignant B cells, and both are medically indicated for the treatment of indolent B-cell lymphoma and related conditions. Clinical results are excellent (20-40% complete response rates and 60-80% overall response rates) and toxicity is typically quite mild. Current research is now attempting to both explore the biology of these compounds and to expand the spectrum of CD20+ diseases that could be treated using either or both of these active agents. Concurrently, work is in progress to achieve the same excellent clinical results using antibodies specific for other, more common epithelial tumors. This work is at an earlier stage than the lymphoma work, partly due to the high innate radiosensitivity of the lymphoid system. Thus, various enhancement methodologies are being explored to increase clinical response rates for these solid tumors, and a number of solid tumor RIT agents are now in early-stage clinical trials. The most likely pattern of use for this field in the next 5 years will probably involve combination or sequential regimens incorporating both radioimmunotherapy and more conventional chemotherapy or external radiotherapy.

Antibody-guided radiation therapy of cancer

Radioimmunotherapy (RIT) using radiolabeled monoclonal antibodies (MAbs) directed against tumor-associated antigens has evolved from an appealing concept to one of the standard treatment options for patients with non-Hodgkin's lymphoma (NHL). Inefficient localization of radiolabeled MAbs to nonhematological cancers due to various tumor-related factors, however, has refrained RIT from outgrowing the experimental stage in solid tumors. Still, small volume or minimal residual disease has been recognized as a potentially suitable target for radiolabeled antibodies. Several strategies are being explored aimed at improving the targeting of radiolabeled MAbs to solid tumors thus improving their therapeutic efficacy. In this review, a historical overview of the application of RIT is given and various aspects of the application of radiolabeled MAbs as anti-cancer agents are discussed. Finally, the clinical results of RIT of NHL, colorectal cancer, ovarian cancer, breast cancer, and renal cell cancer are reviewed.

Intraperitoneal radioimmunotherapy with a humanized anti-TAG-72 (CC49) antibody with a deleted CH2 region

The application of intraperitoneal (i.p.) radioimmunotherapy to treat i.p. tumor loci has been limited by bone marrow toxicity secondary to circulating radiolabeled antibodies. The generation of novel genetically engineered monoclonal antibodies, which can achieve high tumor uptake and rapid blood clearance, should enhance the therapeutic index of i.p. radioimmunotherapy. In this regard, a novel humanized anti-TAG-72 monoclonal antibody with a deleted CH2 region (HuCC49DeltaCH2) has been described, which localized well to subcutaneous xenograft tumors and had a rapid plasma clearance. The aim of this study was to examine the characteristics of this radiolabeled reagent when administered through the i.p. route in mice bearing i.p. tumor (LS174T). The DeltaCH2 molecule and intact humanized CC49 (HuCC49) monoclonal antibody were conjugated to PA-DOTA and radiolabeled with (177)Lu. Both molecules retained high-affinity binding to TAG-72 positive LS174T tumor cells in vitro. The radiolabeled DeltaCH2 molecule had a modest decrease in tumor localization, as compared to the intact molecule when administered i.p. to tumor-bearing mice and a dramatically shorter plasma disappearance T(1/2) at 2.7 hours compared to 61.2 hours for the intact antibody. The radiolabeled DeltaCH2 molecule thus had very high tumor:blood ratios. Using an (131)I-labeled system, the maximum tolerated dose of DeltaCH2 was >3x that of intact HuCC49. Autoradiography of tumors showed low radiation dose rates at tumor centers early (1 and 4 hours), as compared to higher dose rates at tumor periphery but a more uniform distribution by 24 hours. Dose-rate distributions were similar for both reagents. Animals bearing LS174T i.p. tumors were treated with 300 microCi of (177)Lu-labeled DeltaCH2 or intact HuCC49 by i.p. route daily x 3. The (177)Lu-DeltaCH(2) molecule mediated an increase in median survival compared to controls (67.5 +/- 7.5 days versus controls of 32 +/- 3.3) while the same dose of (177)Lu-HuCC49 produced early toxic deaths. These studies suggest that i.p. radioimmunotherapy using radiolabeled HuCC49DeltaCH2 should allow higher radiation doses to be administered with less marrow toxicity and potentially improved efficacy.

Intraperitoneal pretarget radioimmunotherapy with CC49 fusion protein

PURPOSE

This study examined a pretarget radioimmunotherapy strategy for treatment of an i.p. tumor model (LS174T).

EXPERIMENTAL DESIGN

The strategy used regional administration (i.p.) of a novel targeting molecule composed of four CC49 anti-tumor-associated glycoprotein 72 (TAG-72) single-chain antibodies linked to streptavidin as a fusion protein (CC49 fusion protein); 24 hours later, a synthetic clearing agent was administered i.v. to produce hepatic clearance of unbound CC49 fusion protein/synthetic clearing agent complexes. Four hours later, a low molecular weight radiolabeled reagent composed of biotin conjugated to the chelating agent 7,10-tetra-azacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) complexed with (111)In-, (90)Y-, or (177)Lu-DOTA-biotin was injected.

RESULTS

Radiolocalization to tumor sites was superior with i.p. administration of radiolabeled DOTA-biotin as compared with i.v. administration. Imaging and biodistribution studies showed excellent tumor localization of radioactivity with (111)In- or (177)Lu-DOTA-biotin. Tumor localization of (111)In-DOTA-biotin was 43% ID/g and 44% ID/g at 4 and 24 hours with the highest normal tissue localization in the kidney with 6% ID/g at 48 and 72 hours. Therapy studies with (90)Y-DOTA-biotin at doses of 400 to 600 microCi or (177)Lu-DOTA-biotin at doses of 600 to 800 microCi produced significant prolongation of survival compared with controls (P = 0.03 and P < 0.01).

CONCLUSIONS

Pretarget radioimmunotherapy using regional administration of CC49 fusion protein and i.p. (90)Y- or (177)Lu-DOTA-biotin represents a successful therapeutic strategy in the LS174T i.p. tumor model and this strategy may be applicable to human trials in patients with i.p. ovarian cancer.

Current status of cancer therapy with radiolabeled monoclonal antibody

Molecular targeting therapy has become a relevant therapeutic strategy for cancer. There are several monoclonal antibodies used for the treatment of malignant tumors. Radioimmunoconjugate is composed of antibody and radionuclide showing a synergistic effect of radiation and immunemediated cellular toxicity and thereby enabling increased efficacy and minimizing toxicity. Radioimmunotherapy using 131I- and 90Y-labeled anti-CD20 monoclonal antibodies is now indicated for the treatment of patients with CD20 antigen-expressing relapsed or refractory, low-grade or transformed non-Hodgkin's lymphoma (NHL), including patients who are refractory to anti-CD20 monoclonal antibody (rituximab) therapy in the United States. It has been exhibiting favorable anti-tumor efficacy in patients with NHL as compared with rituximab. Myelosuppression is the main side effect associated with the radioimmunotherapy but is usually reversible, and nonhematologic adverse reactions are mild to moderate. Following the impressive results of therapy using radiolabeled monoclonal antibodies for NHL, radioimmunotherapy for solid tumors has been examined; however, the results were unfavorable and did warrant further clinical trials as a single agent. Future studies on radioimmunotherapy for solid tumors should focus on the new strategies of targeting such as locoregional administration for intraperitoneal dissemination, and combination therapy with chemotherapy or cytostatic therapy. Although radioimmunotherapy for NHL has shown excellent results comparable to aggressive chemotherapy without severe adverse effects, additional clinical trials should be performed to define the proper role of radioimmunoconjugates as a relevant strategy for cure of NHL.

Phase I trial of 177lutetium-labeled J591, a monoclonal antibody to prostate-specific membrane antigen, in patients with androgen-independent prostate cancer

PURPOSE

To determine the maximum tolerated dose (MTD), toxicity, human anti-J591 response, pharmacokinetics (PK), organ dosimetry, targeting, and biologic activity of (177)Lutetium-labeled anti-prostate-specific membrane antigen (PSMA) monoclonal antibody J591 ((177)Lu-J591) in patients with androgen-independent prostate cancer (PC).

PATIENTS AND METHODS

Thirty-five patients with progressing androgen-independent PC received (177)Lu-J591. All patients underwent (177)Lu-J591 imaging, PK, and biodistribution determinations. Patients were eligible for up to three retreatments.

RESULTS

Thirty-five patients received (177)Lu-J591, of whom 16 received up to three doses. Myelosuppression was dose limiting at 75 mCi/m(2), and the 70-mCi/m(2) dose level was determined to be the single-dose MTD. Repeat dosing at 45 to 60 mCi/m(2) was associated with dose-limiting myelosuppression; however, up to three doses of 30 mCi/m(2) could be safely administered. Nonhematologic toxicity was not dose limiting. Targeting of all known sites of bone and soft tissue metastases was seen in all 30 patients with positive bone, computed tomography, or magnetic resonance images. No patient developed a human anti-J591 antibody response to deimmunized J591 regardless of number of doses. Biologic activity was seen with four patients experiencing >or= 50% declines in prostate-specific antigen (PSA) levels lasting from 3+ to 8 months. An additional 16 patients (46%) experienced PSA stabilization for a median of 60 days (range, 1 to 21+ months).

CONCLUSION

The MTD of (177)Lu-J591 is 70 mCi/m(2). Multiple doses of 30 mCi/m(2) are well tolerated. Acceptable toxicity, excellent targeting of known sites of PC metastases, and biologic activity in patients with androgen-independent PC warrant further investigation.

Locoreginal radioimmunotherapy with Re-labeled monoclonal antibody in treating small peritoneal carcinomatosis of colon cancer in mice in comparison with I-counterpart

The efficacy of locoregional radioimmunotherapy (RIT) in treating peritoneal tumors of colon cancer of <2 mm in diameter was examined at maximum tolerated doses, focusing the comparison between 186Re and 131I labeled to an anti-colorectal cancer IgG1. Estimated radiation doses to tumors were considerably higher with 186Re-RIT than with 131I-RIT. The advantage of 186Re-RIT decreased with decreasing tumor size, but 186Re-RIT delivered 1.6-times higher radiation to tumors of 1 mm. Consequently, 186Re-RIT attained better survival of mice than 131I-RIT or chemotherapy with 5-fluorouracil did. Therefore, locoregional 186Re-RIT may be an option in an adjuvant setting of colon cancer with high risk of peritoneal dissemination.

Imaging and therapy of tumors induced to express somatostatin receptor by gene transfer using radiolabeled peptides and single chain antibody constructs

The fields of radioimmunodetection and radioimmunotherapy began with an initial paradigm that a targeting molecule (eg, antibody) carrying a radioisotope had the potential of selectively imaging and delivering a therapeutic dose of radiation to tumor sites. A second paradigm was developed in which injection of the targeting molecule was separated from injection of a short-lived radioisotope-labeled ligand (so-called "pretargeting strategy"). This strategy has improved radioisotope delivery to tumors in animal models, enhanced radioimmune imaging in man, and therapeutic trials are in an early phase. We proposed a third paradigm to achieve radioisotopic localization at tumor sites by inducing tumor cells to synthesize a membrane expressed receptor with a high affinity for infused radiolabeled ligands. The use of gene transfer technology to induce expression of high affinity membrane receptors can enhance the specificity of radioligand localization, while the use of radioisotopes with the ability to deliver radiation damage across several cell diameters will compensate for less than perfect transduction efficiency. This approach was termed "Genetic Radioisotope Targeting Strategy." Using this strategy, induction of high levels of gastrin releasing peptide receptor or human somatostatin receptor subtype 2 expression and selective tumor uptake of radiolabeled peptides was achieved. The advantages of the genetic transduction approach are (1) constitutive expression of a tumor-associated antigen/receptor is not required; (2) tumor cells are altered to express a new target receptor or increased quantities of an existing receptor at levels that may significantly improve tumor targeting of radiolabeled ligands compared with normal tissues; (3) gene transfer can be achieved by intratumoral or regional injection of gene vectors; (4) it is feasible to target adenovirus vectors to receptors overexpressed on tumor cells by modifying adenoviral tropism (binding) so that the virus will be targeted specifically to the desired tumor; and (5) it is possible to coexpress the receptor gene and a therapeutic gene, such as cytosine deaminase, for molecular prodrug therapy to produce an enhanced therapeutic effect.

Intraperitoneal chemotherapy for ovarian cancer

Intraperitoneal chemotherapy provides a means by which high concentrations of drugs and long durations of tissue exposure can be attained at the peritoneal surface. It has been studied widely in ovarian cancer, a disease in which intra-abdominal progression remains the major source of morbidity and mortality. Three large randomized trials have shown improved survival in optimally debulked patients who were treated with intraperitoneal chemotherapy as part of a front-line regimen, yet it has not become part of usual therapy. Several factors have contributed to the reluctance to adopt intraperitoneal therapy, including technical issues related to drug delivery and the fact that all of the large randomized trials employed intraperitoneal cisplatin, which has more toxicity than intravenous carboplatin, the current standard of care. Future research is needed for further definition of the clinical benefit of intraperitoneal chemotherapy, modification of existing regimens to minimize side effects, and exploration of intraperitoneal biologic, immunologic, and gene therapy techniques.

Local delivery of (131)I-MIBG to treat peritoneal neuroblastoma

Internal radiotherapy involving systemic administration of iodine-131 metaiodobenzylguanidine ((131)I-MIBG) in neural crest tumours such as neuroblastoma has shown considerable success. Although peritoneal seeding of neuroblastoma occurs less often than metastases to organs such as the liver, no effective treatments exist in this clinical setting. Previous reports have demonstrated the effectiveness of peritoneal application of chemotherapeutic drugs or radiolabelled monoclonal antibodies in several kinds of carcinomas. Local delivery of (131)I-MIBG should produce more favourable dosimetry in comparison with its systemic administration in the treatment of peritoneal neuroblastoma. In the current investigation, a peritoneal model of neuroblastoma was established in Balb/c nu/nu mice by i.p. injection of SK-N-SH neuroblastoma cells. Two weeks after cell inoculation, comparative biodistribution studies were performed following i.v. or i.p. administration of (131)I-MIBG. Mice were treated with 55.5 MBq of (131)I-MIBG administered either i.v. or i.p. at 2 weeks. Intraperitoneal injection of (131)I-MIBG produced significantly higher tumour accumulation than did i.v. injection ( P<0.01). Therapeutic ratios of i.p. injection were 4- to 14-fold higher than those of i.v. injection. Radiotherapy with i.v. administered (131)I-MIBG failed to improve the survival of mice; mean survival of untreated mice and mice treated with i.v. administration of (131)I-MIBG was 59.3+/-3.9 days and 60.6+/-2.8 days, respectively. On the other hand, radiotherapy delivered via i.p. administration of (131)I-MIBG prolonged survival of mice to 94.7+/-17.5 days ( P<0.02 vs untreated controls and mice treated with i.v. (131)I-MIBG therapy). Radiation doses absorbed by tumours at 55.5 MBq of (131)I-MIBG were estimated to be 4,140 cGy with i.p. injection and 450 cGy with i.v. injection. These results indicate the benefits of locoregional delivery of (131)I-MIBG in the treatment of peritoneal neuroblastoma.

Intraperitoneal radioimmunotherapy in treating peritoneal carcinomatosis of colon cancer in mice compared with systemic radioimmunotherapy

Peritoneal spread is one of major causes of mortality in colorectal cancer patients. In the current investigation, the efficacy of radioimmunotherapy (RIT) with i.p. administration of an anti-colorectal cancer IgG1, 131I-A7, was compared to that with i.v. administration in BALB/c female mice bearing peritoneal nodules of LS180 human colon cancer cells, at the same toxicity level. Distribution of either i.p. or i.v. administered 131I-A7 and i.p. administered irrelevant 131I-HPMS-1 was assessed. Based on the results of toxicity determination at increments of 2 MBq and estimated dosimetry, an i.p. dose of 11 MBq and an i.v. dose of 9 MBq were chosen for treatment. Mice were monitored for long-term survival: untreated mice (n = 11), mice undergoing i.p. RIT with 131I-A7 (n = 11), mice undergoing i.v. RIT with 131I-A7 (n = 11) and mice undergoing non-specific i.p. RIT with 131I-HPMS-1 (n = 5). Intraperitoneal injection of 131I-A7 produced faster and greater tumor accumulation than i.v. injection: 34.2 +/- 16.5% of the injected dose per g (% ID/g) and 11.1 +/- 3.6% ID/g at 2 h, respectively (P < 0.0001). Consequently, cumulative radioactivity in tumors was 1.73-fold higher with i.p. injection. 131I-HPMS-1 did not show specific accumulation. Non-specific RIT with 131I-HPMS-1 (mean survival, 26.0 +/- 2.5 days) did not affect the survival as compared to no treatment (26.7 +/- 1.9 days). Intravenous RIT with 131I-A7 prolonged the survival of mice to 32.8 +/- 1.8 days (P < 0.01). Intraperitoneal RIT with 131I-A7 improved the survival more significantly and attained cure in 2 of 11 mice (P < 0.05 vs. i.v. RIT). In conclusion, i.p. RIT is more beneficial in treating peritoneal carcinomatosis of colon cancer than i.v. RIT in a murine model.

Monoclonal antibody therapy for cancer

Monoclonal antibody therapy has emerged as an important therapeutic modality for cancer. Unconjugated antibodies show significant efficacy in the treatment of breast cancer, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia. Promising new targets for unconjugated antibody therapy include cellular growth factor receptors, receptors or mediators of tumor-driven angiogenesis, and B cell surface antigens other than CD20. Immunoconjugates composed of antibodies conjugated to radionuclides or toxins show efficacy in non-Hodgkin's lymphoma. One immunoconjugate containing an antibody and a chemotherapy agent exhibits clinically meaningful antitumor activity in acute myeloid leukemia. Numerous efforts to exploit the ability of antibodies to focus the activities of toxic payloads at tumor sites are under way and show early promise. The ability to create essentially human antibody structures has reduced the likelihood of host-protective immune responses that otherwise limit the duration of therapy. Antibody structures now can be readily manipulated to facilitate selective interaction with host immune effectors. Other structural manipulations that improve the selective targeting properties and rapid systemic clearance of immunoconjugates should lead to the design of effective new treatments, particularly for solid tumors.

Chemotherapy tolerance after radioimmunotherapy with 90Y-CC49 monoclonal antibody in patients with advanced non-small cell lung cancer: clinical effects and hematologic toxicity

The purpose of this retrospective analysis was to evaluate the hematologic toxicity and clinical outcome of salvage chemotherapy following (90)Y-CC49 radioimmunotherapy (RIT) in patients with non-small cell lung cancer (NSCLC). Sixteen patients from a total of 37 who were enrolled in a phase I trial of (90)Y-CC49 monoclonal therapy were treated with post-RIT salvage chemotherapy at our institution. Five patients had received chest radiation therapy prior to RIT, and seven patients had prior chemotherapy. The majority of these patients were treated with doses of (90)Y of >/= 14 mCi/m(2) (8-20 mCi/m(2)), and four of them received concurrent 96-hour taxol infusion. The maximum tolerated dose of this study was exceeded at 17 mCi/m(2), and grade 4 thrombocytopenia/neutropenia were the dose-limiting toxicities. Twelve patients received one chemotherapy regimen as salvage therapy, and four patients had more than one regimen. Four patients (25%) experienced reversible grade 4 neutropenia, but no grade 4 thrombocytopenia was observed. Five patients had stable disease. The median survival from start of salvage therapy was 5.5 months. Our data suggest that therapy with RIT did not significantly affect survival of these patients. Taking into consideration the potential clinical relevance of integration of RIT with other treatment modalities, it is important to expand this clinical experience in order to support combined modality strategies.

Comparison of biodistribution, dosimetry, and outcome from clinical trials of radionuclide-CC49 antibody therapy

CC49 is a second-generation murine antibody with anti-TAG-72 (tumor-associated antigen) reactivity. For cancer therapy, it has the advantage of being expressed on adenocarcinomas but not on most normal tissues. CC49 has been utilized in phase I and II clinical trials at multiple institutions. Therapeutic applications to date have included (131)I-, (90)Y-, and (177)Lu-CC49, with tracer amounts of (111)In-CC49 as a dosimetry surrogate for (90)Y-CC49 therapy. Dosimetry methods and details of their description vary between studies. Biodistribution to normal organs and the effective plasma T(1/2) for various radionuclides were relatively consistent among patients with different diseases and treatment at several institutions. As expected with marrow suppression being the dose-limiting toxicity, higher doses of (177)Lu-CC49 were tolerated via intraperitoneal than IV administration. The biologic response modifier interferon enhanced TAG-72 expression and resulted in a trend of increased uptake of (131)I-CC49 by tumors. Tumor dose estimates were more variable than that of normal organs. Standardization and improved dosimetry may be helpful for comparison among patients in various studies and for establishing dose/toxicity relationships that are useful for predicting safe levels of radioimmunoconjugates.