Clinical development of radioimmunotherapy for B-cell non-Hodgkin's lymphoma

Special radionuclide production activities – recent developments at QST and throughout Japan

National Institutes for Quantum Science and Technology (QST), formerly known as the National Institute of Radiological Sciences (NIRS), has been engaged in work on radiopharmaceutical science using cyclotrons since 1974. Eight pioneering researchers founded the basis of this field of research at NIRS, and to the present, many researchers and technicians have accumulated both scientific and technical achievements, as well as inherited the spirit of research. Besides, in recent years, we have developed production systems with AVF-930 cyclotron for various ‘non-standard’ radioisotopes applied in both diagnosis and therapy. Here, we review the past 50 years of our activities on radioisotope and radiopharmaceutical development, as well as more recent activities.

Nuclear Medicine and Wall Street: An Evolving Relationship

Until recently, it has been challenging to engage Wall Street and large pharmaceutical companies in radiopharmaceutical opportunities. The modest economic prospects of most diagnostic radiopharmaceuticals have not attracted keen interest from the broader business community, despite the rapid advancement of diagnostic imaging capabilities and their increasingly crucial role in the therapeutic process. Similarly, compelling science supporting select radiopharmaceutical therapies in oncology has been overshadowed by the unique challenges posed by this class of drugs and historical commercial failures that serve as sobering reminders of risk. Fortunately, a few notable successes in the targeted radioligand therapeutic space are changing this dynamic, fueling a new flow of investor capital into these technologies and inciting increased merger and acquisition activity that has yielded significant value creation for investors. If the nuclear medicine industry is able to continue to effectively manage historical challenges, then there is significant opportunity for a new and promising wave of radioligand therapies to significantly change the oncology treatment paradigm and elevate the profile of the entire nuclear medicine sector.

Antibody delivery of drugs and radionuclides: factors influencing clinical pharmacology

The therapeutic rationale of antibody conjugates is the selective delivery of a cytotoxin to tumor cells via binding and internalization of the monoclonal antibodies to a specific cell-surface antigen, thereby enhancing the therapeutic index of the cytotoxin. The key structural and functional components of an antibody conjugate are the antibody, the linker and the cytotoxin (chemical or radionuclide) with each component being critical for the successful development of the conjugate. Considerable efforts have been made in understanding the pharmacokinetics, pharmacodynamics, tissue distribution, metabolism and pharmacologic effects of these complex macromolecular entities. The purpose of this article is to discuss the properties and various structural components of antibody conjugates that influence their clinical pharmacology.

Radioimmunotherapy in mantle cell lymphoma

Mantle cell lymphoma (MCL), though characterized by the chromosomal translocation t(11; 14) (q13; q32), is a heterogeneous disease. Often termed an aggressive lymphoma in the U.S., but included in indolent lymphoma trials in Europe, MCL is not curable with standard immuno-chemotherapy. There is no single standard initial therapy for this disease. Although standard lymphoma therapies yield high response rates, relapse is inevitable. Unmet needs in MCL include better induction therapy, consolidation treatments to prolong first remission and better therapeutic options for relapsed disease. In this review, we evaluate the role of radioimmunotherapy (RIT) in MCL, a novel strategy combining monoclonal antibodies with radioisotopes to deliver radiation directly to tumour tissue, both in the frontline and relapsed setting.

Definitive radiation therapy for moderately advanced laryngeal cancer: effects of accelerated hyperfractionation

OBJECTIVE

The purpose of this retrospective study was to analyze the results of accelerated hyperfractionation for patients with moderately advanced (T2 and T3) laryngeal cancer.

METHODS

Between 1998 and 2007, 9 supraglottic carcinomas (6 T2N0M0, 2 T2N2M0, 1 T3N0M0), 30 glottic carcinomas (25 T2N0M0, 5 T3N0M0), and 1 T2N0M0 subglottic carcinoma were treated with definitive radiotherapy using accelerated hyperfractionation without concurrent chemotherapy. The dose-fractionation for 35 patients was 72.8 Gy/56 fractions/5.6 weeks, and that for four patients treated between 1998 and 2001 was 72 Gy/60 fractions/6 weeks. One patient who had been treated with steroid therapy for systemic lupus erythematosus was treated by 67.8 Gy/44 fractions/4.4 weeks.

RESULTS

The local control and overall survival probabilities at 5 years for supraglottic carcinomas were 75% and 86%, respectively. Those for glottic carcinomas were 80% and 92%, respectively. The 5-year local control probabilities for T2 and T3 tumors were 85% and 56%, respectively. This excellent local control rate especially for T2 laryngeal carcinomas may be attributable to the effect of accelerated hyperfractionation. No late toxicities of grade 2 or more was noted among the 39 patients treated with 72.8 Gy/56 fractions or 72 Gy/60 fractions.

CONCLUSION

Accelerated hyperfractionation of 72.8 Gy/56 fractions/5.6 weeks using 1.3 Gy/fraction seems a safe and effective dose-fractionation for patients with moderately advanced laryngeal carcinomas.

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.

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).

Ongoing investigations and new uses of radioimmunotherapy in the treatment of non-Hodgkin's lymphoma

Studies in radiation oncology are focusing on the optimal use of systemic targeted radionuclide therapy (STaRT) in the treatment of patients with cancer. The two approved radioimmunotherapy agents, yttrium-90 ibritumomab tiuxetan and iodine-131 tositumomab, are being studied in a range of lymphoid malignancies, from low-grade to aggressive B-cell non-Hodgkin's lymphomas. Studies of standard- and escalated-dose radioimmunotherapy with or without stem cell support are reviewed, as are radioimmunotherapy with other therapeutic modalities in these settings. The results of these trials have important implications for clinical practice, and it is hoped that they will further clarify the optimal timing and dosing of these agents.