The emerging role of radioimmunotherapy in haematological malignancies

Principles of Immunotherapy: Implications for Treatment Strategies in Cancer and Infectious Diseases

The advances in cancer biology and pathogenesis during the past two decades, have resulted in immunotherapeutic strategies that have revolutionized the treatment of malignancies, from relatively non-selective toxic agents to specific, mechanism-based therapies. Despite extensive global efforts, infectious diseases remain a leading cause of morbidity and mortality worldwide, necessitating novel, innovative therapeutics that address the current challenges of increasing antimicrobial resistance. Similar to cancer pathogenesis, infectious pathogens successfully fashion a hospitable environment within the host and modulate host metabolic functions to support their nutritional requirements, while suppressing host defenses by altering regulatory mechanisms. These parallels, and the advances made in targeted therapy in cancer, may inform the rational development of therapeutic interventions for infectious diseases. Although "immunotherapy" is habitually associated with the treatment of cancer, this review accentuates the evolving role of key targeted immune interventions that are approved, as well as those in development, for various cancers and infectious diseases. The general features of adoptive therapies, those that enhance T cell effector function, and ligand-based therapies, that neutralize or eliminate diseased cells, are discussed in the context of specific diseases that, to date, lack appropriate remedial treatment; cancer, HIV, TB, and drug-resistant bacterial and fungal infections. The remarkable diversity and versatility that distinguishes immunotherapy is emphasized, consequently establishing this approach within the armory of curative therapeutics, applicable across the disease spectrum.

Targeted α-therapy for control of micrometastatic prostate cancer

Carcinoma of the prostate is the second most common cancer in men. In spite of the most aggressive therapies, the control of metastatic prostate cancer remains an elusive objective and many patients die of secondary disease. Targeted alpha-therapy is an emerging therapeutic modality whereby a labeled protein selectively targets cancer cells and delivers a lethal payload, which can kill cancer cells in transit or preangiogenic cell clusters. Recent studies show that targeted alpha-therapy is highly cytotoxic to prostate cancer cells in vitro and can inhibit tumor growth in animal models. This review will consider alpha-emitting radionuclides and current in vitro and in vivo studies with alpha-radioconjugates, and will focus on cell-surface target antigens and targeting vectors for the treatment of prostate cancer.

Radioimmunotherapy: strategies for the future in indolent and aggressive lymphoma

The conjugation of radioisotopes to monoclonal antibodies, or radioimmunotherapy (RIT), is a highly active treatment in non-Hodgkin's lymphoma. RIT has demonstrated high response rates and durable remissions in extensively pretreated patients and has proved highly effective as consolidation after induction chemotherapy in the first-line therapy of follicular lymphoma. Early-phase clinical trials have shown highly promising results using RIT as part of conditioning regimens in patients who are to undergo transplantation and as consolidation after chemotherapy in patients with aggressive lymphomas. Recent data suggest that integrating RIT with immunochemotherapy and transplant conditioning regimens may further improve outcomes for patients.

New insights into the mechanisms of action of radioimmunotherapy in lymphoma

The exquisite sensitivity of haematological malignancies to targeted radiation alongside the impressive results achieved by the pioneers in this field suggests that radioimmunotherapy is likely to be a productive area for future clinical research. Recent experimental work has demonstrated that the combination of targeted radiation and antibody effector mechanisms are critical to long-term clearance of tumour. This review provides the background of clinical and biological insights into the mechanisms of action of radioimmunotherapy.

131I-chTNT Radioimmunotherapy of 43 Patients with Advanced Lung Cancer

The treatment of advanced lung cancer remains a major challenge in clinical medicine, justifying an urgent need for new therapeutic approaches. In a rather unique international collaboration, 43 patients with advanced lung cancer were treated using iodine-131-labeled tumor necrosis therapy chimeric antibody (131I-chTNT).

METHODS

Patients were treated either with intravenous (i.v.) infusion (n = 22), intratumoral injection using a computer tomography (CT)-guided catheter (n = 16), or combination i.v. and intratumoral infusion (n = 5). All patients, regardless of route of administration, received 2 doses of 131I-chTNT on days 1 and 14.

RESULTS

The results showed that of those patients receiving i.v. injection alone, 2 achieved partial response (PR) (9%), 16 had stable disease (73%), and 4 progressed (18%). Of those patients receiving intratumoral injection only, 1 had a complete response (CR) (6%), 8 achieved PR (50%), 7 had stable disease (44%), and none (0%) progressed. Finally, of those patients receiving both i.v. and intratumoral administration, 1 had a CR (20%), 1 achieved PR (20%), 2 had stable disease (40%), and 1 (20%) showed progression.

CONCLUSIONS

These promising results demonstrate that sufficient doses of radiolabeled antibody can be safely delivered to tumors to cause significant therapeutic effects in advanced lung cancer.

In vivo molecular targeted radiotherapy

Unsealed radionuclides have been in clinical therapeutic use for well over half a century. Following the early inappropriate clinical administrations of radium salts in the early 20th century, the first real clinical benefits became evident with the use of ¹³¹I-sodium iodide for the treatment of hypothyroidism and differentiated thyroid carcinoma and ³²P-sodium phosphate for the treatment of polycythaemia vera. In recent years the use of bone seeking agents ⁸⁹Sr, ¹⁵³Sm and ¹⁸⁶Re for the palliation of bone pain have become widespread and considerable progress has been evident with the use of ¹³¹I-MIBG and ⁹⁰Y-somatostatin receptor binding agents. Although the use of monoclonal antibody based therapeutic products has been slow to evolve, the start of the 21st century has witnessed the first licensed therapeutic antibody conjugates based on ⁹⁰Y and ¹³¹I for the treatment of non-Hodgkin's lymphoma. The future clinical utility of this form of therapy will depend upon the development of radiopharmaceutical conjugates capable of selective binding to molecular targets. The availability of some therapeutic radionuclides such as ¹⁸⁸Re produced from the tungsten generator system which can produce activity as required over many months, may make this type of therapy more widely available in some remote and developing countries.

Future products will involve cytotoxic radionuclides with appropriate potency, but with physical characteristics that will enable the administration of therapeutic doses with the minimal need for patient isolation. Further developments are likely to involve molecular constructs such as aptamers arising from new developments in biotechnology.

Patient trials are still underway and are now examining new methods of administration, dose fractionation and the clinical introduction of alpha emitting radiopharmaceutical conjugates. This review outlines the history, development and future potential of these forms of therapy.

Pivotal study of iodine-131-labeled chimeric tumor necrosis treatment radioimmunotherapy in patients with advanced lung cancer

PURPOSE

Tumor necrosis treatment (TNT) uses degenerating tumor cells and necrotic regions of tumors as targets for radioimmunotherapy. Previous studies in animal tumor models and clinical trials have demonstrated that when linked to the therapeutic radionuclide iodine-131, recombinant chimeric TNT antibody ((131)I-chTNT) can deliver therapeutic doses to tumors regardless of the location or type of malignancy. Therapeutic efficacy and toxicity of (131)I-chTNT in advanced lung cancer patients were studied in this pivotal registration trial.

PATIENTS AND METHODS

Patients with advanced lung cancer were treated with systemic or intratumoral injection of (131)I-chTNT in eight oncology centers in China. The objective response rate (ORR) was assessed as the primary end point.

RESULTS

All 107 patients who were entered onto the study and completed therapy had experienced treatment failure after prior radiotherapy or chemotherapy a mean of three times. The results showed an ORR of 34.6% (complete response, 3.7%; partial response, 30.8%; no change, 55.1%; and progressive disease, 10.3%) in all patients and 33% in 97 non-small-cell lung cancer patients. A biodistribution study demonstrated excellent localization of the radioactivity in tumors in both systemically and intratumorally injected patients. The most obvious adverse side effect was mild and reversible bone marrow suppression.

CONCLUSION

Radioimmunotherapy with (131)I-chTNT was well tolerated and can be used systemically or locally to treat refractory tumors of the lung.

Monoclonal antibody therapy of B cell lymphoma

Studies in the early 1980s with anti-idiotype mAbs provided clinical proof that mAbs could be safe and effective antilymphoma agents; however, mAb therapy of lymphoma did not become practical until the chimaeric anti-CD20 mAb rituximab was developed. As a single agent, rituximab is well-tolerated and has clinical efficacy in select patient populations. A number of mechanisms of action have been identified that appear to contribute to the observed antilymphoma effects of mAb. Growing evidence suggests that multiple interacting mechanisms are likely to be involved. Anti-CD20-based radioimmunotherapy and combinations of mAb and chemotherapy are showing promise. mAbs that recognise other target antigens and immunotoxins have been evaluated clinically. It remains unclear whether these other mAbs provide value added beyond rituximab. Research geared towards understanding mAb mechanisms of action and the rational design of the next generation of mAb-based regimens will allow us to take full advantage of this exciting new mode of therapy.

Rituximab and other emerging monoclonal antibody therapies for lymphoma

The recent approval of rituximab, gemtuzumab ozogamicin, alemtuzumab and ibritumomab tiuxetan by the FDA in the US revealed clear evidence that monoclonal antibodies (mAbs) have significant roles in the current treatment of haematologic malignancies. Among the mAbs under clinical development, anti-CD20 mAbs have been most extensively investigated and have shown definitive clinical efficacy. Rituximab is a genetically engineered chimeric anti-CD20 mAb, with mouse variable and human constant regions. Consecutive clinical trials conducted in the US, Europe and Japan have revealed that rituximab is a highly effective agent with acceptable toxicities against indolent and aggressive B cell non-Hodgkin's lymphomas (B-NHLs) as a single agent and in combination with cytotoxic drugs. A recent French Phase III study in elderly patients with untreated aggressive B-NHL suggested that the addition of rituximab to standard CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy increases the complete response rate and prolongs event-free and overall survival. Lymphoma cells are inherently sensitive to radiation. The aim of radioimmunotherapy is to use the mAb to target radiation to lymphoma tissue while minimising toxicity to normal cells. The clinical trials of 90Y ibritumomab tiuxetan and (131)I tositumomab showed they have definitive efficacy in relapsed indolent B-NHL with acceptable toxicities. A recent comparative study in relapsed indolent B-NHL showed that 90Y ibritumomab tiuxetan produces higher response rates than rituximab. In addition, BL22, a recombinant anti-CD22 immunotoxin, showed significant efficacy in patients with chemotherapy-resistant hairy cell leukaemia. MAbs will have significant roles in the treatment of lymphoid malignancies in the future.

Adult acute myeloid leukaemia

The curability of acute myeloid leukaemia (AML) in a fraction of adult patients was demonstrated a long time ago. Currently, the probability of cure is consistently above fifty per cent in patients with de novo disease expressing favourable-risk associated cytogenetic features. Even better, the cure rate exceeds 75% in the acute promyelocytic subtype since the introduction of retinoic acid-containing regimens. In the meantime, continuing progress in supportive care systems and stem cell transplant procedures is making myeloablative therapies, when needed, somewhat less toxic-and thereby more effective-than in the recent past. Therefore, evidence is accumulating to indicate an improved therapeutic trend over the years, with the notable exception of older (>55 years) patients with adverse-risk chromosomal aberrations and/or leukemia secondary to myelodysplasia or prior cancer-related chemotherapy and/or radiotherapy. This review conveys the many facets of this progress, focusing on diagnostic subsets, risk classes, newer biological issues and conventional as well as innovative therapeutic interventions with or without autologous/allogeneic stem cell transplantation.

Educating patients about radioimmunotherapy with yttrium 90 ibritumomab tiuxetan (Zevalin)

OBJECTIVES

To present the relevant information for the education of patients with B-cell non-Hodgkin's lymphoma (NHL) who are about to undergo radioimmunotherapy (RIT) with yttrium 90 (90Y) ibritumomab tiuxetan.

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on radioimmunotherapy and NHL.

CONCLUSION

RIT is an emerging therapeutic option for patients with B-cell NHL and promises to become more prevalent in clinical use. Patients need to understand the rationale for and schedule of treatments with this regimen and the necessary ongoing laboratory tests for monitoring myelosuppression, as well as possible adverse events that might occur after treatment.

IMPLICATIONS FOR NURSING PRACTICE

Nursing professionals should be aware of the logistics of the ibritumomab tiuxetan regimen and with the data associated with it to educate patients and facilitate patient understanding and expectations.

Antibody-induced intracellular signaling works in combination with radiation to eradicate lymphoma in radioimmunotherapy

Radioimmunotherapy (RIT) has emerged as an effective treatment for lymphoma, however the underlying mechanisms are poorly understood. We therefore investigated the relative contributions of antibody and targeted radiation to the clearance of tumor in vivo, using 2 different syngeneic murine B-cell lymphoma models. Although RIT with 131I–anti–major histocompatibility complex class II (MHCII) was effective in targeting radiation to tumor, no improvement in survival was seen by escalating the radiation dose alone and there were no long-term survivors. In contrast, using the combination of 131I anti-MHCII in the presence of unlabeled anti-idiotype (anti-Id), 100% prolonged disease-free survival was seen in both B-cell lymphoma models at the higher radiation dose. Using in vivo tracking we show that treatment with radiation plus anti-Id monoclonal antibody (mAb) results in a substantially greater reduction of splenic tumor cells than with either treatment alone. Prolonged survival could also be achieved using 131I anti-MHCII plus the signaling anti-CD19 mAb. Furthermore, the ability of these anti–B-cell mAbs to improve survival with targeted radiotherapy appeared to correlate with their ability to initiate intracellular signal transduction. Together these data illustrate that using 1 mAb to target radiation to tumor and a second to induce cell signaling is an effective new strategy in RIT.

The rationale for and background of radioimmunotherapy: an emerging therapy for B-cell non-hodgkin’s lymphoma

OBJECTIVES

To present the rationale for and development of radioimmunotherapy (RIT) for non-Hodgkin's lymphoma (NHL), which culminated in the FDA's approval of yttrium 90 (90Y) ibritumomab tiuxetan in February 2002.

DATA SOURCES

Published clinical trials of 90Y ibritumomab tiuxetan and secondary literature on immunotherapy, RIT, and NHL.

CONCLUSION

Monoclonal antibodies to the CD20 antigen have become an accepted therapy for NHL. Factors such as the poor vascularization of some tumors and the variable expression of the antigen can mitigate the efficacy of monoclonal antibodies, which prompted the development of a new strategy, RIT.

IMPLICATIONS FOR NURSING PRACTICE

Knowledge of the background and development of RIT is essential for nurses to educate and manage patients with NHL.

Advances in pretargeting biotechnology

A major focus of current drug research is to improve drug targeting to internal target sites such as to solid tumors or specific organs. The objective of drug targeting, especially for cancer chemotherapy and radioimmunotherapy, is to enhance the effectiveness of the drug by concentrating it at the target site and minimizing its effects in nontarget sites. Although tumor targeting has been obtained with large long-circulating radiolabeled antibody molecules, normal organ activity, especially in the blood kidneys, liver, and bone marrow is a significant problem. Over the last 20 years, studies to improve the therapeutic use of antibodies have included the use of antibody fragments, chase molecules, metabolizable linkers, antibody-directed enzyme prodrugs (ADEPT), local delivery, and pretargeting. Here, we will review the most interesting recent advances in pretargeting biotechnology.

Imaging and dosing in radioimmunotherapy with Yttrium 90 ibritumomab tiuxetan (Zevalin)

Yttrium 90 ibritumomab tiuxetan consists of the murine monoclonal antibody ibritumomab securely bound to the second-generation chelator tiuxetan, which attaches the high-energy pure beta emitter (90)Y, for therapy, or the gamma emitter indium 111, for imaging. The biodistribution of the therapeutic dose of (90)Y ibritumomab tiuxetan can be predicted by using an imaging dose of the antibody labeled with (111)In. Calculation of the therapeutic dose is simple and is based on patient weight and baseline platelet count: for patients with a platelet count of 150 x 10(9)/L or greater the dose of is 0.4 mCi/kg; for patients with mild thrombocytopenia (platelet count 100 x 10(9)/L to 149 x 10(9)/L) the dose is reduced to 0.3 mCi/kg; and the total dose should not exceed 32 mCi. Patients with platelet counts of less than 100 x 10(9)/L should not be treated with (90)Y ibritumomab tiuxetan. Imaging with (111)In ibritumomab tiuxetan is performed only to assess biodistribution of the radioimmunoconjugate. Uptake in sites of pathologic adenopathy, as well as other areas of lymphomatous involvement, is frequently seen on the images, but visualization of tumor uptake is not required to proceed with the therapeutic dose of (90)Y ibritumomab tiuxetan.

131I-Anti CD20 Radioimmunotherapy of Relapsed or Refractory Non-Hodgkins Lymphoma: A Phase II Clinical Trial of a Nonmyeloablative Dose Regimen of Chimeric Rituximab Radiolabeled in a Hospital

In order to increase the availability and affordability of radioimmunotherapy of refractory or relapsed non-Hodgkins lymphoma, we developed and evaluated radioiodinated rituximab in an ongoing physician-sponsored Phase II Clinical Trial. The chimeric 1gG(1) anti CD 20 monoclonal antibody rituximab was radiolabeled with iodine-131 using a modified Chloramine T method with high radiochemical purity (98% +/- 0.82) and preservation of immunoreactivity. All patients received therapeutic loading doses of unlabeled rituximab (375 mg/m(2)) immediately prior to administration of tracer (200 MBq (131)I) or therapy (1.7-4.3 GBq (131)I) activities of (131)I-rituximab to provide additive immunotherapy and enhance tumor uptake of the radiolabeled antibody. Objective response rate (ORR) was 71% in 35 patients with a median follow-up of 14 months (range 4-28 months). Complete remission (CR) was achieved in 54% of patients, with median duration 20 months. Toxicity evaluation included an additional 7 patients followed for at least 3 months. Tracer dosimetry studies were performed in each patient and the whole body radiation absorbed dose was limited to a mean prescribed dose (MPD) of 0.75 Gy. Myelosuppression was reversible and in only 2 of 42 patients was grade IV hematological toxicity observed. No hemopoietic support was required in any patient. There was no instance of hemorrhage or infection in this group of patients in each of whom individual prospective dosimetry was performed prior to (131)I rituximab radioimmunotherapy for relapsed or refractory non-Hodgkins lymphoma.

Radioimmunotherapy for non-Hodgkin's lymphoma with yttrium 90 ibritumomab tiuxetan

The increasing incidence of non-Hodgkin's lymphoma (NHL), coupled with the lack of optimal treatment options, has prompted the development of novel treatments. Of these, radioimmunotherapy is one of the most promising. Two of the radiolabeled monoclonal antibody therapies being studied in the treatment of NHL are yttrium 90 (90Y) ibritumomab tiuxetan and iodine 131 (131I) tositumomab. The radionuclides 90Y and 131I emit beta radiation; 131I also emits gamma radiation, thus requiring more elaborate precautionary measures to limit radiation exposure. The monoclonal antibody portions of the drugs target the CD20 surface antigen that is present on the majority of B-cell lymphomas, resulting in direct radiation to the targeted cells, as well as indirect targeting of adjacent cells (known as the crossfire effect). Clinical trials of 90Y ibritumomab tiuxetan in patients with NHL have produced promising results. The safe and effective use of radioimmunotherapy requires a multidisciplinary team approach in which nurses play a central role.

Selective activation of anticancer prodrugs by monoclonal antibody-enzyme conjugates

A great deal of interest has surrounded the activities of monoclonal antibodies (mAbs), and mAb-drug, toxin and radionuclide conjugates for the treatment of human cancers. In the last few years, a number of new mAb-based reagents have been clinically approved (Rituxan, Herceptin, and Panorex), and several others are now in advanced clinical trials. Successful therapeutic treatment of solid tumors with drug conjugates of such macromolecules must overcome the barriers to penetration within tumor masses, antigen heterogeneity, conjugated drug potency, and efficient drug release from the mAbs inside tumor cells. An alternative strategy for drug delivery involves a two-step approach to cancer therapy in which mAbs are used to localize enzymes to tumor cell surface antigens. Once the conjugate binds to the cancer cells and clears from the systemic circulation, antitumor prodrugs are administered that are catalytically converted to active drugs by the targeted enzyme. The drugs thus released are capable of penetrating within the tumor mass and eliminating both cells that have and have not bound the mAb-enzyme conjugate. Significant therapeutic effects have been obtained using a broad range of enzymes along with prodrugs that are derived from both approved anticancer drugs and highly potent experimental agents. This review focuses on the activities of several mAb-enzyme/prodrug combinations, with an emphasis on those that have provided mechanistic insight, clinical activity, novel protein constructs, and the potential for reduced immunogenicity.

Antibody therapy of lymphoma

The availability of rituximab and the possible imminent availability of two new radiolabelled monoclonal anti-CD20 antibodies (Yttrium-90 (90Y)-ibritumomab and Iodine-131(131I)-tositumomab) have captured much attention in the treatment of lymphoma. The chimeric monoclonal anti-CD20 antibody, rituximab has truly heralded a new era for the treatment of lymphoma and human malignancies. The full potential of antibody-based therapy to improve the outcome in patients with B-cell non-Hodgkin's lymphoma has yet to be defined, but recent data suggests that the combination of chemotherapy plus rituximab may significantly improve outcome for patients with aggressive lymphoma over chemotherapy alone. Highly promising data are also emerging for the use of rituximab in combination with chemotherapy in other types of lymphoma. New advances in antibody therapy, driven by new technologies and defining novel antigen targets, offer the promise of more effective tumour specific therapies. Combinations of antibodies, either conjugated with radioisotopes or unlabelled, used with chemotherapy are likely to provide definitive advances in the treatment of lymphoma in the immediate future.