Ibritumomab tiuxetan radioimmunotherapy for patients with relapsed or refractory non-Hodgkin lymphoma and mild thrombocytopenia: a phase II multicenter trial

Real-world data from yttrium-90 ibritumomab tiuxetan treatment of relapsed or refractory indolent B-cell non-Hodgkin's lymphoma: J3Zi Study

Yttrium-90 ibritumomab tiuxetan (90YIT) is a radioimmunotherapy agent in which the radioisotope yttrium-90 is bound to ibritumomab via tiuxetan as a chelating agent, and is used for relapsed or refractory low-grade B-cell non-Hodgkin's lymphoma (rr-B-NHL). We conducted a joint study to evaluate the clinical outcome of 90YIT. The J3Zi study is composed of data from patients receiving 90YIT for rr-B-NHL from the top three institutions with 10 years of 90YIT treatment experience from October 2008 to May 2018 in Japan. The efficacy, prognostic factors and safety of 90YIT were retrospectively evaluated. Data from 316 patients were analyzed; the mean age was 64.6 years and the median number of prior treatments was 2. The median PFS was 3.0 years, the final OS rate was over 60%, and the median OS was not reached during the study period. Significant factors influencing PFS were sIL-2R ≤ 500 (U/mL) and no disease progression within 24 months of first treatment. Significant factors influencing OS were number of prior treatments ≤ 2 and sIL-2R ≤ 500 (U/mL). The PFS and OS rates were found to be significantly higher in the late half era (2013 to 2018) than in the early half era (2008 to 2013) during the study period. Prognosis following 90YIT treatment was improved in the late half era compared to the early half era. As treatment using 90YIT increased, administration of 90YIT shifted to the earlier treatment line. This may have contributed to the improvement of prognosis found in the late era. (UMIN000037105).

Treatment of drug-induced immune thrombocytopenias

Several therapeutic agents can cause thrombocytopenia by either immune-mediated or non-immune-mediated mechanisms. Non-immune-mediated thrombocytopenia is due to direct toxicity of drug molecules to platelets or megakaryocytes. Immune-mediated thrombocytopenia, on the other hand, involves the formation of antibodies that react to platelet-specific glycoprotein complexes, as in classic drug-induced immune thrombocytopenia (DITP), or to platelet factor 4, as in heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombotic thrombocytopenia (VITT). Clinical signs include a rapid drop in platelet count, bleeding or thrombosis. Since the patient's condition can deteriorate rapidly, prompt diagnosis and management are critical. However, the necessary diagnostic tests are only available in specialized laboratories. Therefore, the most demanding step in treatment is to identify the agent responsible for thrombocytopenia, which often proves difficult because many patients are taking multiple medications and have comorbidities that can themselves also cause thrombocytopenia. While DITP is commonly associated with an increased risk of bleeding, HIT and VITT have a high mortality rate due to the high incidence of thromboembolic complications. A structured approach to drug-associated thrombocytopenia/thrombosis can lead to successful treatment and a lower mortality rate. In addition to describing the treatment of DITP, HIT, VITT, and vaccine-associated immune thrombocytopenia, this review also provides the pathophysiological and clinical information necessary for correct patient management.

Treatment of chemotherapy-induced thrombocytopenia in patients with non-hematologic malignancies

Chemotherapy-induced thrombocytopenia (CIT) is a common complication of the treatment of non-hematologic malignancies. Many patient-related variables (e.g., age, tumor type, number of prior chemotherapy cycles, amount of bone marrow tumor involvement) determine the extent of CIT. CIT is related to the type and dose of chemotherapy, with regimens containing gemcitabine, platinum, or temozolomide producing it most commonly. Bleeding and the need for platelet transfusions in CIT are rather uncommon except in patients with platelet counts below 25x10⁹/L in whom bleeding rates increase significantly and platelet transfusions are the only treatment. Nonetheless, platelet counts below 70x10⁹/L present a challenge. In patients with such counts, it is important to exclude other causes of thrombocytopenia (medications, infection, thrombotic microangiopathy, post-transfusion purpura, coagulopathy and immune thrombocytopenia). If these are not present, the common approach is to reduce chemotherapy dose intensity or switch to other agents. Unfortunately decreasing relative dose intensity is associated with reduced tumor response and remission rates. Thrombopoietic growth factors (recombinant human thrombopoietin, pegylated human megakaryocyte growth and development factor, romiplostim, eltrombopag, avatrombopag and hetrombopag) improve pretreatment and nadir platelet counts, reduce the need for platelet transfusions, and enable chemotherapy dose intensity to be maintained. National Comprehensive Cancer Network guidelines permit their use but their widespread adoption awaits adequate phase III randomized, placebo-controlled studies demonstrating maintenance of relative dose intensity, reduction of platelet transfusions and bleeding, and possibly improved survival. Their potential appropriate use also depends on consensus by the oncology community as to what constitutes an appropriate pretreatment platelet count as well as identification of patient-related and treatment variables that might predict bleeding.

Radiolabeled Antibodies for Cancer Imaging and Therapy

Simple Summary

Monoclonal antibodies (mAbs) have the ability to specifically target tumor-cell antigens. This unique property has led to their use in the delivery of radioisotopes to tumor sites (scintigraphic imaging and radioimmunotherapy (RIT)). The choice of the radionuclide depends on its unique physical properties and intended use. Using radiolabeled mAbs with imaging techniques provides critical data that are essential for predicting side effects and determining an optimal antibody dose and treatment schedule. While RIT has been successful in the management of hematological malignancies, the treatment of solid tumors remains challenging. Various strategies are being investigated to improve the efficacy of RIT in solid tumors.

Abstract

Radioimmunoconjugates consist of a monoclonal antibody (mAb) linked to a radionuclide. Radioimmunoconjugates as theranostics tools have been in development with success, particularly in hematological malignancies, leading to approval by the US Food and Drug Administration (FDA) for the treatment of non-Hodgkin’s lymphoma. Radioimmunotherapy (RIT) allows for reduced toxicity compared to conventional radiation therapy and enhances the efficacy of mAbs. In addition, using radiolabeled mAbs with imaging methods provides critical information on the pharmacokinetics and pharmacodynamics of therapeutic agents with direct relevance to the optimization of the dose and dosing schedule, real-time antigen quantitation, antigen heterogeneity, and dynamic antigen changes. All of these parameters are critical in predicting treatment responses and identifying patients who are most likely to benefit from treatment. Historically, RITs have been less effective in solid tumors; however, several strategies are being investigated to improve their therapeutic index, including targeting patients with minimal disease burden; using pre-targeting strategies, newer radionuclides, and improved labeling techniques; and using combined modalities and locoregional application. This review provides an overview of the radiolabeled intact antibodies currently in clinical use and those in development.

Combination radionuclide therapy: A new paradigm

Targeted molecular radionuclide therapy (MRT) has shown its potential for the treatment of cancers of multiple origins. A combination therapy strategy employing two or more distinct therapeutic approaches in cancer management is aimed at circumventing tumor resistance by simultaneously targeting compensatory signaling pathways or bypassing survival selection mutations acquired in response to individual monotherapies. Combination radionuclide therapy (CRT) is a newer application of the concept, utilizing a combination of radiolabeled molecular targeting agents with chemotherapy and beam radiation therapy for enhanced therapeutic index. Encouraging results are reported with chemotherapeutic agents in combination with radiolabeled targeting molecules for cancer therapy. With increasing awareness of the various survival and stress response pathways activated after radionuclide therapy, different holistic combinations of MRT agents with radiosensitizers targeting such pathways have also been explored. MRT has also been studied in combination with beam radiotherapy modalities such as external beam radiation therapy and carbon ion radiation therapy to enhance the anti-tumor response. Nanotechnology aids in CRT by bringing together multiple monotherapies on a single nanostructure platform for treating cancers in a more precise or personalized way. CRT will be a key player in managing cancers if correctly tailored to the individual patient profile. The success of CRT lies in an in-depth understanding of the radiobiological principles and pathways activated in response.

Hydrogen deuterium exchange mass spectrometry identifies the dominant paratope in CD20 antigen binding to the NCD1.2 monoclonal antibody

A comparative canine–human therapeutics model is being developed in B-cell lymphoma through the generation of a hybridoma cell that produces a murine monoclonal antibody specific for canine CD20. The hybridoma cell produces two light chains, light chain-3, and light chain-7. However, the contribution of either light chain to the authentic full-length hybridoma derived IgG is undefined. Mass spectrometry was used to identify only one of the two light chains, light chain-7, as predominating in the full-length IgG. Gene synthesis created a recombinant murine–canine chimeric monoclonal antibody expressing light chain-7 that reconstituted the IgG binding to CD20. Using light chain-7 as a reference sequence, hydrogen deuterium exchange mass spectrometry was used to identify the dominant CDR region implicated in CD20 antigen binding. Early in the deuteration reaction, the CD20 antigen suppressed deuteration at CDR3 (V_H). In later time points, deuterium suppression occurred at CDR2 (V_H) and CDR2 (V_L), with the maintenance of the CDR3 (V_H) interaction. These data suggest that CDR3 (V_H) functions as the dominant antigen docking motif and that antibody aggregation is induced at later time points after antigen binding. These approaches define a methodology for fine mapping of CDR contacts using nested enzymatic reactions and hydrogen deuterium exchange mass spectrometry. These data support the further development of an engineered, synthetic canine–murine monoclonal antibody, focused on CDR3 (V_H), for use as a canine lymphoma therapeutic that mimics the human–murine chimeric anti-CD20 antibody Rituximab.

Cell Surface GRP94 as a Novel Emerging Therapeutic Target for Monoclonal Antibody Cancer Therapy

Glucose-regulated protein 94 (GRP94) is an endoplasmic reticulum (ER)-resident member of the heat shock protein 90 (HSP90) family. In physiological conditions, it plays a vital role in regulating biological functions, including chaperoning cellular proteins in the ER lumen, maintaining calcium homeostasis, and modulating immune system function. Recently, several reports have shown the functional role and clinical relevance of GRP94 overexpression in the progression and metastasis of several cancers. Therefore, the current review highlights GRP94’s physiological and pathophysiological roles in normal and cancer cells. Additionally, the unmet medical needs of small chemical inhibitors and the current development status of monoclonal antibodies specifically targeting GRP94 will be discussed to emphasize the importance of cell surface GRP94 as an emerging therapeutic target in monoclonal antibody therapy for cancer.

Phase I trial of docetaxel plus lutetium-177-labeled anti-prostate-specific membrane antigen monoclonal antibody J591 (177Lu-J591) for metastatic castration-resistant prostate cancer

BACKGROUND

Docetaxel remains a standard of care for metatsatic castration resistant porstate cancer (mCRPC) and has radiosensitizing properties. The dose limiting toxicity (DLT) of radioimmunotherapy is myelosuppression; dose fractionation of ¹⁷⁷Lu-J591 allows similar administered doses with less toxicity. This study (NCT00916123) was designed to determine the safety, DLT, and maximum tolerated dose of fractionated ¹⁷⁷Lu-J591 administered concurrently with standard docetaxel.

METHODS

Men with progressive mCRPC received docetaxel 75 mg/m² every 3 weeks with escalating 2 fractionated doses of ¹⁷⁷Lu-J591 (1.48 GBq/m² up to max of 2.96 GBq/m²) with cycle 3. Cycle 4 of docetaxel was planned 6 weeks after cycle 3 to allow for recovery from ¹⁷⁷Lu-J591-associated hematologic toxicity. DLT was defined as delay in docetaxel >3 weeks, prolonged myelosuppression or need for >2 platelet transfusions, febrile neutropenia, or grade ≥3 nonhematological toxicity following ¹⁷⁷Lu-J591. PSA was assessed prior to each cycle and serial computed tomography (CT) and bone scan were performed.

RESULTS

Fifteen men with progressive mCRPC received dose-escalated targeted radionuclide therapy in 4 cohorts up to the highest planned dose (2.96 GBq/m²). No DLT was seen at any dose level. Grade 4 neutropenia without fever occurred in 8 (53.5%) and thromboytopenia in 2 (13.3%), with 2 receiving prophylactic platelet transfusion. No grade ≥3 nonhematological toxicity was observed. 11 (73.3%) had >50% PSA decline, with 78.6% having favorable circulating tumor cell counts after ¹⁷⁷Lu-J591. All patients had targeting of known sites of disease by planar ¹⁷⁷Lu-J591 imaging.

CONCLUSION

The combination of ¹⁷⁷Lu-J591 delivered as a single fractionated cycle with docetaxel/prednisone is feasible in patients with mCRPC. Without preselection for prostate-specific membrane antigen, accurate targeting of known sites of disease and a strong preliminary efficacy signal was observed.

Radioimmunotherapy in Non-Hodgkin's Lymphoma: Retrospective Adverse Event Profiling of Zevalin and Bexxar

The development of monoclonal antibodies has dramatically changed the outcome of patients with non-Hodgkin’s lymphoma (NHL), the most common hematological malignancy. However, despite the satisfying results of monoclonal antibody treatment, only few NHL patients are permanently cured with single-agent therapies. In this context, radioimmunotherapy, the administration of radionuclides conjugated to monoclonal antibodies, is aimed to augment the single-agent efficacy of immunotherapy in order to deliver targeted radiation to tumors, particularly CD20+ B-cell lymphomas. Based on evidence from several trials in NHL, the radiolabeled antibodies ⁹⁰Y-ibritumomab tiuxetan (Zevalin, Spectrum Pharmaceuticals) and ¹³¹I-tositumomab (Bexxar, GlaxoSmithKline) received FDA approval in 2002 and 2003, respectively. However, none of the two radioimmunotherapeutic agents has been broadly applied in clinical practice. The main reason for the under-utilization of radioimmunotherapy includes economic and logistic considerations. However, concerns about potential side effects have also been raised. Driven by these developments, we performed retrospective analysis of adverse events reporting Zevalin or Bexxar, extracted from the FDA’s Adverse Event Reporting System (FAERS) and the World Health Organization’s VigiBase repository. Our results indicate that the two radioimmunotherapeutic agents have both related and distinct side effect profiles and confirm their known toxicological considerations. Our work also suggests that computational analysis of real-world post-marketing data can provide informative clinical insights. While more prospective studies are necessary to fully characterize the efficacy and safety of radioimmunotherapy, we expect that it has not yet reached its full therapeutic potential in modern hematological oncology.

Current Development of Monoclonal Antibodies in Cancer Therapy

Exploiting the unique specificity of monoclonal antibodies has revolutionized the treatment and diagnosis of haematological and solid organ malignancies; bringing benefit to millions of patients over the past decades. Recent achievements include conjugating antibodies with toxic payloads resulting in superior efficacy and/or reduced toxicity, development of molecular imaging techniques targeting specific antigens for use as predictive and prognostic biomarkers, the development of novel bi- and tri-specific antibodies to enhance therapeutic benefit and abrogate resistance and the success of immunotherapy agents. In this chapter, we review an overview of antibody structure and function relevant to cancer therapy and provide an overview of pivotal clinical trials which have led to regulatory approval of monoclonal antibodies in cancer treatment. We further discuss resistance mechanisms and the unique side effects of each class of antibody and provide an overview of emerging therapeutic agents.

Multicenter, Open-Label, Phase II Study of Bendamustine and Rituximab Followed by 90-Yttrium (Y) Ibritumomab Tiuxetan for Untreated Follicular Lymphoma (Fol-BRITe)

PURPOSE

Bendamustine and rituximab (BR) has been established as a superior frontline therapy over R-CHOP in the treatment of follicular lymphoma (FL). Yttrium-90 Ibritumomab tiuxetan (⁹⁰YIT) is an effective consolidation strategy after chemotherapy induction. This prospective, single-arm, multicenter, phase II trial evaluated the response rate, progression-free survival (PFS), and tolerability of BR followed by consolidation with ⁹⁰YIT in patients with untreated FL.

PATIENTS AND METHODS

The study included grade 1 to 3a FL patients aged ≥18 years, chemotherapy-naïve, and requiring treatment for stage II-IV disease. Study treatment included an initial rituximab treatment, followed by four cycles of BR. Patients were eligible for consolidation with ⁹⁰YIT, 6 to 12 weeks after BR, if they obtained at least a partial response after induction had adequate count recovery and bone marrow infiltration < 25%.

RESULTS

Thirty-nine patients were treated. Eighty-two percent had an intermediate or high-risk Follicular Lymphoma International Prognostic Index score, and 6 of 39 (15%) were grade 3a. The response rate was 94.8%, and the complete response(CR)/CR unconfirmed (CRu) rate was 77% in the intention-to-treat analysis. The conversion rate from PR to CR/Cru after ⁹⁰YIT was 81%. After median follow-up of 45 months, the PFS was 0.71 (95% confidence interval, 0.57-0.89).

CONCLUSIONS

This report demonstrates that four cycles of BR followed by consolidation with ⁹⁰YIT achieve high response rates that are durable. In addition, consolidation with ⁹⁰YIT results in a high conversion rate of PR to CR/CRu. A short course of BR followed by ⁹⁰YIT is a safe and effective regimen for frontline treatment of FL.

Kutane Lymphome

Kutane Lymphome (cutaneous lymphomas: CL) umfassen die Gruppe der kutanen T-Zell-Lymphome (cutaneous T-cell lymphomas: CTCL), kutanen B-Zell-Lymphome (cutaneous B-cell lymphomas: CBCL) und die sog. hämatodermischen Neoplasien (HN). CL gehören zur Gruppe der Non-Hodgkin-Lymphome (NHL) und stellen in der Subgruppe der extranodalen NHL die zweithäufigste Gruppe hinter den gastrointestinalen Lymphomen dar (Jaffe et al. 2009). Man unterscheidet zwischen primären und sekundären CL. Primäre CL haben ihren Ursprung in der Haut und bleiben in der Regel darauf auch längere Zeit beschränkt, während sekundäre CL kutane Manifestationen von primär nodalen oder extranodalen Lymphomen darstellen (Willemze 2005). Die primären CL unterscheiden sich hinsichtlich klinischem Verlauf, Therapieoptionen und Prognose erheblich von nodalen und extrakutanen Lymphomen. So zeigen z. B. die primär kutanen CD30+-T-Zell-Lymphome einen gutartigen Verlauf, wogegen die nodalen Varianten als aggressiv eingestuft werden. Da die CL zumeist weniger aggressiv sind, werden sie auch weniger aggressiv behandelt.

Therapeutic monoclonal antibodies and clinical laboratory tests: When, why, and what is expected?

BACKGROUND

We herein provide an overview of the clinical laboratory tests that should be performed before, during and after using therapeutic monoclonal antibodies (mAbs) and the clinical laboratory tests that may be affected by mAbs.

METHODS

The labels of FDA-approved therapeutic mAbs were downloaded from DailyMed (the official website for drug labels) and were used as the sources of data for this review.

RESULTS

It was found that most of the labels provided information relevant to the clinical laboratory tests, including the tests needed before mAbs treatment to check the patients' background status and to identify potentially sensitive patients, the tests needed during or after the treatment to evaluate the patients' response, and the mAbs that may lead to false positive or negative results for clinical laboratory tests.

CONCLUSIONS

The present findings will be of interest to physicians, laboratory scientists, those involved in drug development and surveillance and individuals making health care policy.

Efficacy and safety evaluation of fludarabine-based chemotherapy regimen for patients with non-Hodgkin lymphoma: A meta-analysis

This meta-analysis was performed to evaluate the efficacy and safety of fludarabine (F)-based regimen for the treatment of non-Hodgkin lymphoma (NHL) compared with other regimens with no F contained.PubMed, Embase, Cochrane Library, Wanfang, VIP, and CNKI databases were searched to identify eligible literatures. R software version 3.12 was used for statistical analysis. Odds ratio (OR) with 95% confidence interval (CI) were utilized to express the complete response, overall response and adverse events outcomes. Egger test was carried out to examine the publication bias and sensitivity analysis was performed to evaluate the stability of our results.Twelve eligible literatures consisting of 1587 patients were included in this study. Greater complete response (OR = 1.66, 95% CI: 0.98-2.80) and overall response (OR = 1.38, 95% CI: 0.85-2.24) were found for patients who received F-based regimen than those received other regimens, although the results were not statistically significant. In addition, F-based regimen was associated with significantly lower risk of adverse events compared with other regimens (OR = 0.46, 95% CI: 0.28-0.74). Results of subgroup analysis showed that significantly lower incidence was presented only for constipation among the 7 specific adverse events (OR = 0.03, 95% CI: 0.01-0.14).F-based chemotherapy regimen was an effective and well-tolerated treatment for patients with NHL.

Priming radioimmunotherapy with external beam radiation in patients with relapsed low grade non-Hodgkin lymphoma

BACKGROUND

The aim of this study was to evaluate the outcomes of priming salvage radioimmunotherapy (RIT) with a low dose of external beam radiotherapy (EBRT) in patients with relapsed low grade non-Hodgkin lymphoma (LG-NHL).

METHODS

Patients who received salvage RIT with or without 2 × 2 Gy EBRT between March 2009 and February 2013 were retrospectively reviewed at a single institution. Planning target volume (PTV) for EBRT was created by adding a 1-2 cm expansion to the gross tumor volume depending on the anatomical location. Kaplan-Meier method via log-rank was employed to analyze the endpoints freedom from progression (FFP) and overall survival (OS).

RESULTS

We identified 22 patients who received salvage RIT without chemotherapy with a median follow up of 34 months. Of these, 9 (41%) patients were treated with EBRT immediately prior to RIT, and 13 (59%) received salvage RIT alone. Median FFP was not reached in patients who underwent combination treatment, while it was 9 months for patients treated with RIT alone (p = 0.02). OS for all patients at 36 months was 80.3% with no significant difference between the two groups (p = 0.88). On univariate analysis, the addition of EBRT was associated with improved FFP [hazard ratio (HR) = 4.17; 95% confidence interval (CI), 1.24-19.1; p = 0.02)]. No long term toxicities were reported in both groups.

CONCLUSIONS

RIT outcomes and effects were improved with addition of low-dose EBRT immediately prior to it, in the treatment of relapsed LG-NHL with no additional toxicity. This study is hypothesis-generating and the findings should be validated in prospective studies.

Outcome Comparison of Allogeneic versus Autologous Stem Cell Transplantation in Transformed Low-Grade Lymphoid Malignancies: A Systematic Review and Pooled Analysis of Comparative Studies

BACKGROUND

Some patients with low-grade lymphoid malignancies develop transformed disease, requiring stem cell transplantation (SCT). SCT outcomes in transformed low-grade lymphoid malignancies may differ from those of nontransformed disease or other aggressive non-Hodgkin lymphomas. We conducted a pooled analysis of the clinical outcomes of allogeneic versus high-dose therapy (HDT) with autologous SCT in adult patients with transformed low-grade lymphoid malignancies.

METHODS

A PubMed, EMBASE, and Cochrane search yielded 4 comparative studies reporting allogeneic versus HDT with autologous SCT outcomes in adults (age ≥18) with transformed low-grade lymphoid malignancies, including follicular, chronic/small lymphocytic, and marginal zone lymphoma. Risk ratio (RR) and 95% CI were calculated using random-effects models.

RESULTS

Rates for overall survival (OS) were 51.0 versus 69.5% (RR = 1.55, 95% CI 1.19-2.02, p = 0.001), rates of relapse were 37.3 versus 35.3% (RR = 1.04, 95% CI 0.70-1.55, p = 0.84), and rates of transplant-related mortality (TRM) were 33.3 versus 7.2% (RR = 4.52, 95% CI 2.75-7.43, p < 0.00001) for allogeneic versus autologous SCT. Previous rituximab treatment, reduced intensity conditioning regimen prior to SCT, or original pathology had no prognostic impact.

CONCLUSION

HDT followed by autologous SCT was associated with lower TRM and a better OS, but there was no difference in relapse versus allogeneic SCT. Autologous SCT may be the better therapeutic option, considering the second chance of allogeneic SCT in the case of relapse.

Radioimmunotherapy for non-Hodgkin's lymphoma; positioning, safety, and efficacy of 90Y-Ibritumomab. 10 years of experience and follow-up

INTRODUCTION

Radioimmunotherapy (RIT) is one of the therapies directed against molecular targets in non-Hodgkin's lymphoma (NHL).

OBJECTIVE

To evaluate the positioning, safety, and effectiveness of RIT with 90Y-Ibritumomab in NHL patients.

METHOD

A retrospective study was conducted on patients with NHL who received RIT with 90Y-Ibritumomab. An evaluation was made of the concordance with clinical guidelines, toxicity as rated by the Common Terminology Criteria for Adverse Events (CTCAE), and effectiveness was assessed based on response to treatment, overall survival (OS), and progression-free survival (PFS).

RESULTS

RIT was requested in 26 patients, of whom 21 (11 women, mean age 56±10 years) were included in the study, with the following distribution: Follicular NHL, 67%, Mantle NHL, 14%, Diffuse large B-cell NHL, 9.5%, and Transformed NHL 9.5%. Twelve patients with refractory NHL, 7 for consolidation response, and 2 transplant conditioning, were treated. Adverse effects were observed in 71% of patients, which were usually manageable and transient, and with the most common being thrombocytopenia. At 3-4 months, overall response rate was 76.2% (71.4% complete and 4.8% partial response), and 19% had progression of disease. With a median follow up of 70 months, the OS was 96±8 months, and the PFS was 54±11 months.

CONCLUSION

RIT showed a moderate correlation with clinical guidelines, and is probably underused. Adverse effects were common, mild, and manageable. The data show a high complete response rate and an increase in the OS and PFS.

90-yttrium-ibritumomab tiuxetan consolidation of fludarabine, mitoxantrone, rituximab in intermediate/high-risk follicular lymphoma: updated long-term results after a median follow-up of 7 years

Radioimmunotherapy (RIT) after an induction phase with conventional chemoimmunotherapy became an attractive strategy of consolidation for patients with advanced follicular lymphoma: in particular, in many studies RIT was represented by yttrium-90-ibritumomab tiuxetan ((90) Y-IT). Independently by the different front-line treatment, updates on the long-term follow-up of these studies are needed because the disease course of follicular lymphoma is characterised by multiple relapses and progressively shorter durations of response. We report updated long-term efficacy and toxicity results of a multicenter phase II study on sequential treatment with four cycles of fludarabine, mitoxantrone, and rituximab followed by (90) Y-IT as front-line therapy for untreated patients with intermediate/high-risk follicular lymphoma. With a median follow-up of 84 months, only 19/49 (38.8%) complete response patients relapsed, yielding an estimated long-term disease-free survival of 62.6%. The 7-year overall survival was 72.7%. Four (7.3%) second acute myeloid leukemia occurred, with a median time following RIT of 42 months. A relevant patients' responsiveness to subsequent therapies occurred: approximately 65% of relapsed patients obtained a good clinical response after the second-line treatment. These data represented the first evidence of a real role even in the long period of 90Y-IT after a fludarabine-containing regimen plus rituximab in the treatment of high-risk follicular lymphoma.

Short duration immunochemotherapy followed by radioimmunotherapy consolidation is effective and well tolerated in relapsed follicular lymphoma: 5-year results from a UK National Cancer Research Institute Lymphoma Group study

We report a phase II study to evaluate the efficacy and toxicity of abbreviated immunochemotherapy followed by (90) Y Ibritumomab tiuxetan ((90) Y-IT) in patients with recurrent follicular lymphoma. Of the 52 patients enrolled, 50 were treated with three cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) or R-CVP (rituximab, cyclophosphamide, vincristine, prednisolone), followed by (90) Y-IT regimen (15 MBq/kg, maximum 1200 MBq) preceded by two infusions of 250 mg/m(2) rituximab. The overall response rate was 98% with complete response (CR) 30% and partial response (PR) 68%. 18 patients with a PR following chemotherapy improved to a CR following (90) Y-IT: a conversion rate of 40%. Seven patients with PR following (90) Y-IT subsequently improved to a CR 12-18 months later, leading to an overall CR rate of 44%. With a median follow-up of 5 years, median progression-free survival was 23·1 months and overall survival was 77·5% at 5 years. High trough serum rituximab levels (median 112 μg/ml; range 52-241) were attained after four doses of rituximab, prior to (90) Y-IT; this was not found to influence response rates. The treatment was well tolerated with few (13·5%) grade 3 or 4 infective episodes and manageable haematological toxicity. Abbreviated immunochemotherapy followed by (90) Y-IT is an effective and well-tolerated treatment in recurrent follicular lymphoma patients previously exposed to rituximab.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT00637832.

The Development of a Recombinant scFv Monoclonal Antibody Targeting Canine CD20 for Use in Comparative Medicine

Monoclonal antibodies are leading agents for therapeutic treatment of human diseases, but are limited in use by the paucity of clinically relevant models for validation. Sporadic canine tumours mimic the features of some human equivalents. Developing canine immunotherapeutics can be an approach for modeling human disease responses. Rituximab is a pioneering agent used to treat human hematological malignancies. Biologic mimics that target canine CD20 are just being developed by the biotechnology industry. Towards a comparative canine-human model system, we have developed a novel anti-CD20 monoclonal antibody (NCD1.2) that binds both human and canine CD20. NCD1.2 has a sub-nanomolar K_d as defined by an octet red binding assay. Using FACS, NCD1.2 binds to clinically derived canine cells including B-cells in peripheral blood and in different histotypes of B-cell lymphoma. Immunohistochemical staining of canine tissues indicates that the NCD1.2 binds to membrane localized cells in Diffuse Large B-cell lymphoma, Marginal Zone Lymphoma, and other canine B-cell lymphomas. We cloned the heavy and light chains of NCD1.2 from hybridomas to determine whether active scaffolds can be acquired as future biologics tools. The V_H and V_L genes from the hybridomas were cloned using degenerate primers and packaged as single chains (scFv) into a phage-display library. Surprisingly, we identified two scFv (scFv-3 and scFv-7) isolated from the hybridoma with bioactivity towards CD20. The two scFv had identical V_H genes but different V_L genes and identical CDR3s, indicating that at least two light chain mRNAs are encoded by NCD1.2 hybridoma cells. Both scFv-3 and scFv-7 were cloned into mammalian vectors for secretion in CHO cells and the antibodies were bioactive towards recombinant CD20 protein or peptide. The scFv-3 and scFv-7 were cloned into an ADEPT-CPG2 bioconjugate vector where bioactivity was retained when expressed in bacterial systems. These data identify a recombinant anti-CD20 scFv that might form a useful tool for evaluation in bioconjugate-directed anti-CD20 immunotherapies in comparative medicine.

Allogeneic hematopoietic cell transplantation as curative therapy for non-transformed follicular lymphomas

Allogeneic hematopoietic cell transplantation (HCT) offers the chance of cure for patients with non-transformed follicular lymphoma (FL), but is associated with the risk of non-relapse mortality (NRM). The aim of this study was to identify subgroups of FL patients who benefit from HCT. The European Society for Blood and Marrow Transplantation (EBMT) Minimum-Essential-A Data of 146 consecutive patients who received HCT for FL between 1998 and 2008 were extracted from the database of the German Registry 'DRST'. Diagnosis of FL was verified by contact with the reference pathologists. Estimated 1-, 2- and 5-year overall survivals (OS) were 67%, 60% and 53%, respectively. Day 100 NRM was 15%. Thirteen out of 33 patients (40%) with treatment-refractory disease (RD) at the time of transplantation survived long term. Univariate statistical analysis suggested limited chronic GvHD, donor age ⩽42 years and TBI-based conditioning in treatment refractory patients to correlate with favorable OS. Independent prognostic factors for OS were treatment-sensitive disease and limited chronic GvHD for the whole cohort, and additionally TBI-based conditioning for the treatment refractory subgroup. In contrast, patient age ⩾55 years had no impact on outcome. Thus, HCT for FL is associated with acceptable NRM, and offers a substantial chance of cure for patients with RD or advanced age. Donors ⩽42 years should be preferred if available.

Antibody-mediated delivery of therapeutics for cancer therapy

INTRODUCTION

Antibody-conjugated therapies (ACTs) combine the specificity of monoclonal antibodies to target cancer cells directly with highly potent payloads, often resulting in superior efficacy and/or reduced toxicity. This represents a new approach to the treatment of cancer. There have been highly promising clinical trial results using this approach with improvements in linker and payload technology. The breadth of current trials examining ACTs in haematological malignancies and solid tumours indicate the potential for clinical impact.

AREAS COVERED

This review will provide an overview of ACTs currently in clinical development as well as the principles of antibody delivery and types of payloads used, including cytotoxic drugs, radiolabelled isotopes, nanoparticle-based siRNA particles and immunotoxins.

EXPERT OPINION

The focus of much of the clinical activity in ACTs has, understandably, been on their use as a monotherapy or in combination with standard of care drugs. This will continue, as will the search for better targets, linkers and payloads. Increasingly, as these drugs enter routine clinical care, important questions will arise regarding how to optimise ACT treatment approaches, including investigation of resistance mechanisms, biomarker and patient selection strategies, understanding of the unique toxicities of these drugs, and combinatorial approaches with standard therapies as well as emerging therapeutic agents like immunotherapy.

90Y-ibritumomab tiuxetan therapy in allogeneic transplantation in B-cell lymphoma with extensive marrow involvement and chronic lymphocytic leukemia: utility of pretransplantation biodistribution

BACKGROUND

Biodistribution data to date using In-ibritumomab tiuxetan have been initially obtained in patients with less than 25% lymphomatous bone marrow involvement and adequate hematopoietic synthetic function. In this article we present the results of an analysis of the biodistribution data obtained from a cohort of patients with extensive bone marrow involvement, baseline cytopenias, and chronic lymphocytic leukemia (CLL).

MATERIALS AND METHODS

Thirty-nine patients with a diagnosis of B-cell lymphoma or CLL expressing the CD20 antigen, who had failed at least one prior regimen, and had evidence of persistent disease were included in this analysis; however, only 38 of them completed the treatment. Semiquantitative analysis of the biodistribution was performed using regions of interest over the liver, lungs, kidneys, spleen, and sacrum. The observed interpatient variability including higher liver uptake in four patients is discussed.

RESULTS

No severe solid organ toxicity was observed at the maximum administered activity of 1184 MBq (32 mCi) Y-ibritumomab tiuxetan. After accounting for differences in marrow involvement, patients with CLL exhibit comparable biodistributions to those with B-NHL. We found that the estimated sacral marrow uptake on 48 h images in patients with bone marrow involvement may be an indicator of bone marrow involvement. There was no correlation between tumor visualization and response to treatment.

CONCLUSION

These data suggest that the imaging step is not critical when the administered activity is below 1184 MBq (32 mCi). However, our analysis confirms that the semiquantitative imaging data can be used to identify patients at risk for liver toxicity when higher doses of Y-ibritumomab tiuxetan are used. Patients with CLL can have excellent targeting of disease by In-ibritumomab tiuxetan, indicating potential efficacy in this patient population.

Chemotherapy-induced peripheral neurotoxicity (CIPN): what we need and what we know

Chemotherapy-induced peripheral neurotoxicity (CIPN) is one of the most frequent and severe long-term side effects of cancer chemotherapy. Preclinical and clinical studies have extensively investigated CIPN searching for effective strategies to limit its severity or to treat CIPN-related impairment, but the results have been disappointing. Among the reasons for this failure are methodological flaws in both preclinical and clinical investigations. Their successful resolution might provide a brighter perspective for future studies. Among the several neurotoxic chemotherapy drugs, oxaliplatin may offer a clear example of a methodological approach eventually leading to successful clinical trials. However, the same considerations apply to the other neurotoxic agents and, although frequently neglected, also to the new "targeted" agents.

Current therapeutic strategies and new treatment paradigms for follicular lymphoma

Follicular lymphoma (FL) is an indolent non-Hodgkin's lymphoma that remains an incurable disease for most patients. It is responsive to a variety of different treatments, however it follows a pattern of relapsing and remitting disease. Traditional therapeutic options for patients with untreated FL include expectant observation for asymptomatic and low tumor burden and multiagent cytotoxic chemotherapy for symptomatic and/or high tumor burden. Biologics have become an integral part of therapy with agents that target B lymphocytes, including monoclonal anti-CD20 antibodies and radiolabeled anti-CD20 antibodies. Treatment response to cytotoxic and biologic therapy is high initially; however, with subsequent treatments, response rate and remission duration typically decline and cumulative toxicities increase. The identification of novel targeted agents, use of stem cell transplantation, and new treatment combinations provide the opportunity to enhance patient outcomes. In this review, we critically examine standard treatment strategies for patients with newly diagnosed and relapsed or refractory FL and discuss established and emerging novel therapeutic approaches.

Does tumoral (111)In-ibritumomab accumulation correlate with therapeutic effect and outcome in relapsed or refractory low-grade B-cell lymphoma patients undergoing (90)Y-ibritumomab radioimmunotherapy?

OBJECTIVES

The aim of this study was to determine whether tumoral (111)In-ibritumomab accumulation on pre-treatment imaging correlates with therapeutic responses and progression-free survival (PFS) in patients with non-Hodgkin's lymphoma (NHL) undergoing (90)Y-ibritumomab radioimmunotherapy (RIT).

METHODS

This was a retrospective study of 39 patients with low-grade B-cell NHL treated with RIT. We classified the patients into positive and negative groups according to the presence or absence of tumoral (111)In-ibritumomab accumulation on pre-treatment (111)In-ibritumomab examinations. We then determined the correlation between the (111)In-ibritumomab imaging findings and the patients' therapeutic responses and PFS.

RESULTS

Tumoral (111)In-ibritumomab accumulation was positive in 64.1% and negative in 35.9% of the patients. The (111)In-positive patients had a significantly higher overall response rate (ORR) compared to the (111)In-negative patients (100.0% vs. 78.6%, p = 0.02). The (111)In-negative patients with advanced disease (stages III/IV) had a significantly lower ORR (40%) and a significantly higher rate of progressive disease (40.0%) compared to those of the (111)In-negative patients with limited disease (stages I/II) (100% and 0%, p = 0.009 each). However, these two groups had similar 2-year PFS rates (65.0% vs. 50.0%, p = 0.80).

CONCLUSIONS

(111)In-ibritumomab imaging findings seem to correlate with ORR and the progressive disease rate after RIT, but not with PFS.

KEY POINTS

All 39 NHL patients had tumoral accumulation on pretreatment FDG-PET/CT. 64.1% of NHL patients had tumoral accumulation on a pretreatment (111) In-ibritumomab examination. (90) Y-ibritumomab RIT resulted in high overall response and complete remission rates. (111) In-ibritumomab avidity of lymphoma lesions could predict a strong therapeutic effect. (111) In-ibritumomab imaging findings did not correlate with progression-free survival.

Toxicity of targeted therapeutic agents in lymphoma and management: part 1: monoclonal antibodies and radioimmunotherapy

SUMMARY This two-part review strives to comprehensively characterize common toxicities associated with targeted therapies in lymphoma and their management. Current targeted therapies for lymphoma include monoclonal antibodies, radioimmunotherapy and histone deacteylase inhibitors. New drugs that are expected to significantly alter the therapeutic landscape include PI3K, Bruton’s tyrosine kinase and BCL2 inhibitors. This manuscript focuses on the toxicities and associated management recommendations of monoclonal antibodies and radioimmunotherapy. In the second part of this review, we will focus on the toxicities and management pertaining to targeted therapeutic agents including histone deacteylase, PI3K/AKT and Bruton’s tyrosine kinase and BCL2 inhibitors.

Fractionated 90Y-Ibritumomab Tiuxetan Radioimmunotherapy As an Initial Therapy of Follicular Lymphoma: An International Phase II Study in Patients Requiring Treatment According to GELF/BNLI Criteria

Purpose

We report an international, multicenter phase II trial to evaluate the efficacy and toxicity of fractionated 90Y-ibritumomab tiuxetan (90Y-IT) as initial therapy of follicular lymphoma (FL).

Patients and Methods

A total of 74 patients, with a median age of 61 years (range, 28 to 80 years), were recruited requiring initial therapy by Groupe d'Etude des Lymphomes Folliculaires (GELF)/British National Lymphoma Investigation (BNLI) criteria. Among them, 78% had stage III-IV disease, 32% intermediate, and 44% high-risk (according to FL International Prognostic Index). Treatment consisted of two doses of 90Y-IT (11.1 MBq/kg) administered 8 to 12 weeks apart. Patients with more than 20% lymphoma infiltration of bone marrow (BM) received one infusion per week for 4 consecutive weeks of rituximab (375 mg/m2) and proceeded to fractionated radioimmunotherapy (RIT) only if a repeat BM biopsy demonstrated clearing of lymphoma to less than 20% involvement. The primary end point was end of treatment response of the intention-to-treat population. Secondary objectives were safety and progression-free survival (PFS).

Results

Initial overall response rate (ORR) was 94.4% (68 of 72 patients) with combined complete response (CR/CRu) of 58.3% (42 of 72 patients). Nine patients subsequently improved response making an ORR of 95.8% (69 of 72 patients) and CR/CRu of 69.4% (50 of 72 patients). At a median follow-up of 3.1 years (range, 0.2 to 5.2 years) estimated 3-year PFS is 58%, treatment-free survival 66%, and overall survival 95%. Median PFS is 40.2 months. Thirty patients have experienced disease progression and 24 have required further treatment. The treatment was well tolerated with few (2.8%) grade 3 or 4 infectious episodes or adverse events and manageable hematologic toxicity.

Conclusion

Fractionated RIT using 90Y-IT is an effective initial treatment for advanced-stage FL in patients with higher tumor burden requiring treatment.

Kutane Lymphome

Kutane Lymphome (cutaneous lymphomas: CL) umfassen die Gruppe der kutanen T-Zell-Lymphome (cutaneous T-cell lymphomas: CTCL), kutanen B-Zell-Lymphome (cutaneous B-cell lymphomas: CBCL) und die sog. hämatodermischen Neoplasien (HN). CL gehören zur Gruppe der Non-Hodgkin-Lymphome (NHL) und stellen in der Subgruppe der extranodalen NHL die zweithäufigste Gruppe hinter den gastrointestinalen Lymphomen dar (Jaffe et al. 2009). Man unterscheidet zwischen primären und sekundären CL. Primäre CL haben ihren Ursprung in der Haut und bleiben in der Regel darauf auch längere Zeit beschränkt, während sekundäre LymphomekutaneCL kutane Manifestationen von primär nodalen oder extranodalen Lymphomen darstellen (Willemze 2005). Die primären CL unterscheiden sich hinsichtlich klinischem Verlauf, Therapieoptionen und Prognose erheblich von nodalen und extrakutanen Lymphomen. So zeigen z. B. die primär kutanen CD30⁺ Lymphome einen gutartigen Verlauf, wogegen die nodalen Varianten als aggressiv eingestuft werden. Da die CL zumeist weniger aggressiv sind, werden sie weniger aggressiv behandelt.

Polyclonal and monoclonal antibodies in clinic

Immunoglobulins (Ig) or antibodies are heavy plasma proteins, with sugar chains added to amino-acid residues by N-linked glycosylation and occasionally by O-linked glycosylation. The versatility of antibodies is demonstrated by the various functions that they mediate such as neutralization, agglutination, fixation with activation of complement and activation of effector cells. Naturally occurring antibodies protect the organism against harmful pathogens, viruses and infections. In addition, almost any organic chemical induces antibody production of antibodies that would bind specifically to the chemical. These antibodies are often produced from multiple B cell clones and referred to as polyclonal antibodies. In recent years, scientists have exploited the highly evolved machinery of the immune system to produce structurally and functionally complex molecules such as antibodies from a single B clone, heralding the era of monoclonal antibodies. Most of the antibodies currently in the clinic, target components of the immune system, are not curative and seek to alleviate symptoms rather than cure disease. Our group used a novel strategy to identify reparative human monoclonal antibodies distinct from conventional antibodies. In this chapter, we discuss the therapeutic relevance of both polyclonal and monoclonal antibodies in clinic.

Molecular imaging and carbonic anhydrase IX-targeted radioimmunotherapy in clear cell renal cell carcinoma

Conventional imaging is suboptimal at evaluating disease status in renal cell carcinoma (RCC) because of poor sensitivity. Furthermore, there is an unmet need for the treatment of metastatic RCC, both in terms of improvement of progression-free survival and limitation of toxicity. For this reason, radionuclide imaging and radionuclide therapy are extensively investigated. This review provides an overview of the current progress in molecular imaging and radionuclide therapy in clear cell RCC and will focus on promising detection and therapy strategies targeting the carbonic anhydrase IX antigen, which is expressed in clear cell RCC.

Development of an imaging-guided CEA-pretargeted radionuclide treatment of advanced colorectal cancer: first clinical results

Background:

Radiolabelled antibody targeting of cancer is limited by slow blood clearance. Pretargeting with a non-radiolabelled bispecific monoclonal antibody (bsMAb) followed by a rapidly clearing radiolabelled hapten peptide improves tumour localisation. The primary goals of this first pretargeting study in patients with the anti-CEACAM5 × anti-hapten (HSG) bsMAb, TF2, and the radiolabelled hapten-peptide, IMP288, were to assess optimal pretargeting conditions and safety in patients with metastatic colorectal cancer (CRC).

Methods:

Different dose schedules were studied in four cohorts of five patients: (1) shortening the interval between the bsMAb and peptide administration (5 days vs 1 day), (2) escalating the TF2 dose (from 75 to 150 mg), and (3) reducing the peptide dose (from 100 to 25 μg). After confirmation of tumour targeting by ¹¹¹In-IMP288, patients were treated with a bsMAb/¹⁷⁷Lu-IMP288 cycle.

Results:

Rapid and selective tumour targeting of the radiolabelled peptide was visualised within 1 h, with high tumour-to-tissue ratios (>20 at 24 h). Improved tumour targeting was achieved with a 1-day interval between the administration of the bsMAb and the peptide and with the 25-μg peptide dose. High ¹⁷⁷Lu-IMP288 doses (2.5–7.4 GBq) were well tolerated, with some manageable TF2 infusion reactions, and transient grades 3–4 thrombocytopaenia in 10% of the patients who received ¹⁷⁷Lu-IMP288.

Conclusion:

This phase I study demonstrates for the first time that pretargeting with bsMAb TF2 and radiolabelled IMP288 in patients with CEA-expressing CRC is feasible and safe. With this pretargeting method, tumours are specifically and rapidly targeted.

90Yttrium-Ibritumomab Tiuxetan Consolidation of First Remission in Advanced-Stage Follicular Non-Hodgkin Lymphoma: Updated Results After a Median Follow-Up of 7.3 Years From the International, Randomized, Phase III First-Line Indolent Trial

Purpose

Updated results are presented after a median follow-up of 7.3 years from the phase III First-Line Indolent Trial of yttrium-90 (90Y) –ibritumomab tiuxetan in advanced-stage follicular lymphoma (FL) in first remission.

Patients and Methods

Patients with CD20+stage III or IV FL with complete response (CR), unconfirmed CR (CRu), or partial response (PR) after first-line induction treatment were randomly assigned to90Y-ibritumomab consolidation therapy (rituximab 250 mg/m2days −7 and 0, then90Y-ibritumomab 14.8 MBq/kg day 0; maximum 1,184 MBq) or no further treatment (control). Primary end point was progression-free survival (PFS) from date of random assignment.

Results

For 409 patients available for analysis (90Y-ibritumomab, n = 207; control, n = 202), estimated 8-year overall PFS was 41% with90Y-ibritumomab versus 22% for control (hazard ratio [HR], 0.47; P < .001). For patients in CR/CRu after induction, 8-year PFS with90Y-ibritumomab was 48% versus 32% for control (HR, 0.61; P = .008), and for PR patients, it was 33% versus 10% (HR, 0.38; P < .001). For90Y-ibritumomab consolidation, median PFS was 4.1 years (v 1.1 years for control; P < .001). Median time to next treatment (TTNT) was 8.1 years for90Y-ibritumomab versus 3.0 years for control (P < .001) with approximately 80% response rates to second-line therapy in either arm, including autologous stem-cell transplantation. No unexpected toxicities emerged during long-term follow-up. Estimated between-group 8-year overall survival rates were similar. Annualized incidence rate of myelodysplastic syndrome/acute myeloblastic leukemia was 0.50% versus 0.07% in90Y-ibritumomab and control groups, respectively (P = .042).

Conclusion

90Y-ibritumomab consolidation after achieving PR or CR/CRu to induction confers 3-year benefit in median PFS with durable 19% PFS advantage at 8 years and improves TTNT by 5.1 years for patients with advanced FL.

An update on radioimmunotherapy for lymphoma

SUMMARY Radioimmunotherapy is a promising treatment for B-cell lymphoma. 90Y-ibritumomab tiuxetan (Zevalin®) and 131I-tositumomab (Bexxar®) combine the potent antilymphoma effect of radiation with the specificity of antibody targeting. They have shown efficacy in follicular lymphoma in the setting of relapsed or refractory disease as consolidation regimens after first-line therapy, and in the front-line setting as single agents. Given their tolerability, they are actively being investigated as therapies or adjuncts for elderly patients with relapsed or high-risk diffuse large B-cell lymphoma. They have been added to autologous and allogeneic stem cell transplant preparatory regimens in early clinical trials with acceptable safety and efficacy. Early concerns over excess rates of treatment-related myelodysplastic syndrome and acute myelogenous leukemia have not come to fruition, but these questions remain to be fully answered. Ultimately, these are promising treatments for a variety of B-cell lymphomas. They are also models for the development of new radioimmunotherapies.

Phase I study of a modified regimen of ⁹⁰Yttrium-ibritumomab tiuxetan for relapsed or refractory follicular or transformed CD20+ non-Hodgkin lymphoma

Radioimmunotherapy capitalizes on the radiosensitivity of non-Hodgkin lymphoma (NHL) and the targeted nature of monoclonal antibodies. In an attempt to reverse bone marrow infiltration with B-cells and optimize the biodistribution of Yttrium-90 (⁹⁰Y)-ibritumomab tiuxetan, we conducted a phase I study combining a single course of ⁹⁰Y-ibritumomab tiuxetan after a 4-weekly course of rituximab in relapsed or refractory low-grade or transformed CD20+ B-cell NHLs with <25% marrow involvement. The 0.4 mCi/kg dose was associated with 80% grade-4 cytopenias. Dose escalation was held, and 6 patients were enrolled at a 0.3 mCi/kg cohort. As the 0.3 mCi/kg dose was well tolerated, the 0.4 mCi/kg cohort was expanded to 6 additional patients. In the expansion cohort, grade-4 cytopenia developed in 33%. Further dose escalation was held, and the maximum tolerated dose was determined at 0.4 mCi/kg. With this regimen, marrow involvement decreased in all patients with complete clearance in 50%. The overall response rate was 82%. With a median follow-up of 31.7 months, the median progression-free survival and time to next treatment were 12.3 and 10.9 months, respectively. Although this regimen was associated with a high response rate, the hematologic toxicity was higher than with the standard ⁹⁰Y-ibritumomab tiuxetan regimen.

Epitope interactions of monoclonal antibodies targeting CD20 and their relationship to functional properties

Several novel anti-CD20 monoclonal antibodies are currently in development with the aim of improving the treatment of B cell malignancies. Mutagenesis and epitope mapping studies have revealed differences between the CD20 epitopes recognized by these antibodies. Recently, X-ray crystallography studies confirmed that the Type I CD20 antibody rituximab and the Type II CD20 antibody obinutuzumab (GA101) differ fundamentally in their interaction with CD20 despite recognizing a partially overlapping epitope on CD20. The Type I CD20 antibodies rituximab and ofatumumab are known to bind to different epitopes. The differences suggest that the biological properties of these antibodies are not solely determined by their core epitope sequences, but also depend on other factors, such as the elbow hinge angle, the orientation of the bound antibody and differential effects mediated by the Fc region of the antibody. Taken together, these factors may explain differences in the preclinical properties and clinical efficacy of anti-CD20 antibodies.

Radioimmunotherapy for B-cell non-hodgkin lymphomas

BACKGROUND

Radioimmunotherapy (RIT) is a safe and effective therapeutic option for patients with indolent B-cell non-Hodgkin lymphomas (NHL), in both up-front and relapsed/refractory settings. Two approved agents (90Y-ibritumomab tiuxetan and 131I-tositumomab) are available in the United States. Both target CD20 with similar clinical outcomes but with unique clinical considerations and radiation precautions due to the use of varying radioisotopes.

METHODS

This paper reviews the available evidence for these approved RIT agents and examines the recently published and ongoing clinical trials of potential novel indications for aggressive B-cell NHL.

RESULTS

A pretreatment biodistribution evaluation required before administering the 90Y-ibritumomab tiuxetan therapeutic dose has been removed, which once limited its usage. The potential clinical applications of RIT include relapsed/refractory indolent B-cell NHL, diffuse large B-cell lymphoma, indolent lymphoma in the front-line setting, and mantle cell lymphoma. Multiple novel RIT agents are in preclinical and clinical development, and the addition of radiosensitizers or external-beam radiotherapy may act in synergy with RIT for both indolent and aggressive lymphomas. The risk of treatment-related myelodysplastic syndrome does not appear to be higher in patients treated with RIT over those receiving chemotherapy alone.

CONCLUSIONS

RIT is a safe, effective, and significantly underutilized therapy for patients with B-cell NHL, and many studies have demonstrated the efficacy of 90Y-ibritumomab tiuxetan and 131I-tositumomab for relapsed/refractory indolent B-cell lymphomas. Continued research to establish its efficacy for other lymphoma subtypes is warranted.