Pre-dosing with lilotomab prior to therapy with 177Lu-lilotomab satetraxetan significantly increases the ratio of tumor to red marrow absorbed dose in non-Hodgkin lymphoma patients

Recent preclinical and clinical advances in radioimmunotherapy for non-Hodgkin's lymphoma

Radioimmunotherapy (RIT) is a therapy that combines a radioactive nucleotide with a monoclonal antibody (mAb). RIT enhances the therapeutic effect of mAb and reduces toxicity compared with conventional treatment. The purpose of this review is to summarize the current progress of RIT for treating non-Hodgkin's lymphoma (NHL) based on recent preclinical and clinical studies. The efficacy of RIT targeting the B-lymphocyte antigen cluster of differentiation 20 (CD20) has been demonstrated in clinical trials. Two radioimmunoconjugates targeting CD20, yttrium-90 (90Y)-ibritumomab-tiuxetan (Zevalin) and iodine-131 (131I)-tositumomab (Bexxar), have been approved in the USA Food and Drug Administration (FDA) for treating relapsed/refractory indolent or transformed NHL in 2002 and 2003, respectively. Although these two radioimmunoconjugates are effective and least toxic, they have not achieved popularity due to increasing access to novel therapies and the complexity of their delivery process. RIT is constantly evolving with the identification of novel targets and novel therapeutic strategies using newer radionuclides such as alpha-particle isotopes. Alpha-particles show very short path lengths and high linear energy transfer. These characteristics provide increased tumor cell-killing activities and reduced non-specific bystander responses on normal tissue. This review also discusses reviewed pre-targeted RIT (PRIT) and immuno-positron emission tomography (PET). PRIT potentially increases the dose of radionuclide delivered to tumors while toxicities to normal tissues are limited. Immuno-PET is a molecular imaging tracer that combines the high sensitivity of PET with the specific targeting capability of mAb. Immuno-PET strategies targeting CD20 and other antigens are currently being developed. The theragnostic approach by immuno-PET will be useful in monitoring the treatment response.

Clinical Advances and Perspectives in Targeted Radionuclide Therapy

Targeted radionuclide therapy has become increasingly prominent as a nuclear medicine subspecialty. For many decades, treatment with radionuclides has been mainly restricted to the use of iodine-131 in thyroid disorders. Currently, radiopharmaceuticals, consisting of a radionuclide coupled to a vector that binds to a desired biological target with high specificity, are being developed. The objective is to be as selective as possible at the tumor level, while limiting the dose received at the healthy tissue level. In recent years, a better understanding of molecular mechanisms of cancer, as well as the appearance of innovative targeting agents (antibodies, peptides, and small molecules) and the availability of new radioisotopes, have enabled considerable advances in the field of vectorized internal radiotherapy with a better therapeutic efficacy, radiation safety and personalized treatments. For instance, targeting the tumor microenvironment, instead of the cancer cells, now appears particularly attractive. Several radiopharmaceuticals for therapeutic targeting have shown clinical value in several types of tumors and have been or will soon be approved and authorized for clinical use. Following their clinical and commercial success, research in that domain is particularly growing, with the clinical pipeline appearing as a promising target. This review aims to provide an overview of current research on targeting radionuclide therapy.

Radioimmunotherapy of Non-Hodgkin B-cell Lymphoma: An update

Systemic radioimmunotherapy (RIT) is arguably the most effective and least toxic anticancer treatment for non-Hodgkin lymphoma (NHL). In treatment-naïve patients with indolent NHL, the efficacy of a single injection of RIT compares with that of multiple cycles of combination chemotherapy. However, 20 years following the approval of the first CD20-targeting radioimmunoconjugates ⁹⁰Y-Ibritumomab-tiuxetan (Zevalin) and ¹³¹I-tositumomab (Bexxar), the number of patients referred for RIT in western countries has dramatically decreased. Notwithstanding this, the development of RIT has continued. Therapeutic targets other than CD20 have been identified, new vector molecules have been produced allowing for faster delivery of RIT to the target, and innovative radionuclides with favorable physical characteristics such as alpha emitters have been more widely available. In this article, we reviewed the current status of RIT in NHL, with particular focus on recent clinical and preclinical developments.

FDG PET/CT and Dosimetric Studies of 177Lu-Lilotomab Satetraxetan in a First-in-Human Trial for Relapsed Indolent non-Hodgkin Lymphoma-Are We Hitting the Target?

Purpose

[¹⁷⁷Lu]Lu-lilotomab satetraxetan, a novel CD37 directed radioimmunotherapy (RIT), has been investigated in a first-in-human phase 1/2a study for relapsed indolent non-Hodgkin lymphoma. In this study, new methods were assessed to calculate the mean absorbed dose to the total tumor volume, with the aim of establishing potential dose–response relationships based on 2-deoxy-2-[18F]fluoro-d-glucose (FDG) positron emission tomography (PET) parameters and clinical response. Our second aim was to study if higher total tumor burden induces reduction in the ¹⁷⁷Lu-lilotomab satetraxetan accumulation in tumor.

Procedures

Fifteen patients with different pre-dosing (non-radioactive lilotomab) regimens were included and the cohort was divided into low and high non-radioactive lilotomab pre-dosing groups for some of the analyses. ¹⁷⁷Lu-lilotomab satetraxetan was administered at dosage levels of 10, 15, or 20 MBq/kg. Mean absorbed doses to the total tumor volume (tTAD) were calculated from posttreatment single-photon emission tomography (SPECT)/computed tomography (CT) acquisitions. Total values of metabolic tumor volume (tMTV), total lesion glycolysis (tTLG) and the percent change in these parameters were calculated from FDG PET/CT performed at baseline, and at 3 and 6 months after RIT. Clinical responses were evaluated at 6 months as complete remission (CR), partial remission (PR), stable disease (SD), or progressive disease (PD).

Results

Significant decreases in tMTV and tTLG were observed at 3 months for patients receiving tTAD ≥ 200 cGy compared to patients receiving tTAD < 200 cGy (p = .03 for both). All non-responders had tTAD < 200 cGy. Large variations in tTAD were observed in responders. Reduction in ¹⁷⁷Lu-lilotomab satetraxetan uptake in tumor volume was not observed in patients with higher baseline tumor burden (tTMV).

Conclusion

tTAD of ≥ 200 cGy may prove valuable to ensure clinical response, but further studies are needed to confirm this in a larger patient population. Furthermore, this work indicates that higher baseline tumor burden (up to 585 cm³) did not induce reduction in radioimmunoconjugate accumulation in tumor.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11307-022-01731-3.

89Zr-PET imaging to predict tumor uptake of 177Lu-NNV003 anti-CD37 radioimmunotherapy in mouse models of B cell lymphoma

[¹⁷⁷Lu]Lu-DOTA-NNV003, a radioimmunoconjugate targeting CD37, is developed as novel radioimmunotherapy (RIT) treatment for patients with B cell non-Hodgkin’s lymphoma (NHL). Since patients are at risk for developing hematological toxicities due to CD37 expression on normal B cells, we aimed to develop ⁸⁹Zr-labeled NNV003 for positron emission tomography (PET) imaging as a surrogate tool to predict [¹⁷⁷Lu]Lu-DOTA-NNV003 RIT whole-body distribution and tumor uptake. NNV003 antibody was first radiolabeled with ⁸⁹Zr. [⁸⁹Zr]Zr-N-sucDf-NNV003 tumor uptake was evaluated by PET imaging of mice bearing human CD37-expressing REC1 B cell NHL or RAMOS Burkitt’s lymphoma xenograft tumors followed by ex vivo analysis. Finally, CD37-targeting of [⁸⁹Zr]Zr-N-sucDf-NNV003 and [¹⁷⁷Lu]Lu-DOTA-NNV003 RIT were compared. [⁸⁹Zr]Zr-N-sucDf-NNV003 accumulated in REC1 tumors over time, which was not observed for non-specific, ¹¹¹In-labeled IgG control molecule. In RAMOS tumor-bearing mice, [⁸⁹Zr]Zr-N-sucDf-NNV003 tumor uptake was higher than [¹¹¹In]In-DTPA-IgG at all tested tracer protein doses (10 µg, 25 µg and 100 µg; P < 0.01), further confirming [⁸⁹Zr]Zr-N-sucDf-NNV003 tumor uptake is CD37-mediated. [⁸⁹Zr]Zr-N-sucDf-NNV003 and [¹⁷⁷Lu]Lu-DOTA-NNV003 RIT showed similar ex vivo biodistribution and tumor uptake in the RAMOS tumor model. In conclusion, [⁸⁹Zr]Zr-N-sucDf-NNV003 PET imaging can serve to accurately predict CD37-targeting of [¹⁷⁷Lu]Lu-DOTA-NNV003. To enable clinical implementation, we established a good manufacturing practice (GMP)-compliant production process for [⁸⁹Zr]Zr-N-sucDf-NNV003.

Myelosuppression in patients treated with 177Lutetium-lilotomab satetraxetan can be predicted with absorbed dose to the red marrow as the only variable

BACKGROUND

The aim of this study was to investigate dosimetry data and clinical variables to predict hematological toxicity in non-Hodgkin lymphoma (NHL) patients treated with [¹⁷⁷Lutetium]Lu-lilotomab satetraxetan.

MATERIAL AND METHODS

A total of 17 patients treated with [¹⁷⁷Lu]Lu-lilotomab satetraxetan in a first-in-human phase 1/2a study were included. Absorbed dose to the red marrow was explored using SPECT/CT-imaging of the lumbar vertebrae L2-L4 over multiple time points. Percentage reduction of thrombocytes and neutrophils at nadir compared to baseline (PBN) and time to nadir (TTN) were chosen as indicators of myelosuppression and included as dependent variables. Two models were applied in the analysis, a multivariate linear model and a sigmoidal description of toxicity as a function of absorbed dose. A total of 10 independent patient variables were investigated in the multivariate analysis.

RESULTS

Absorbed dose to the red marrow ranged from 1 to 4 Gy. Absorbed dose to the red marrow was found to be the only significant variable for PBN for both thrombocytes and neutrophils. The sigmoid function gave similar results in terms of accuracy when compared to the linear model.

CONCLUSION

Myelosuppression in the form of thrombocytopenia and neutropenia in patients treated with [¹⁷⁷Lu]Lu-lilotomab satetraxetan can be predicted from the SPECT/CT-derived absorbed dose estimate to the red marrow.

Radioimmunotherapy for solid tumors: spotlight on Glypican-1 as a radioimmunotherapy target

Radioimmunotherapy (i.e., the use of radiolabeled tumor targeting antibodies) is an emerging approach for the diagnosis, therapy, and monitoring of solid tumors. Often using paired agents, each targeting the same tumor molecule, but labelled with an imaging or therapeutic isotope, radioimmunotherapy has achieved promising clinical results in relatively radio-resistant solid tumors such as prostate. Several approaches to optimize therapeutic efficacy, such as dose fractionation and personalized dosimetry, have seen clinical success. The clinical use and optimization of a radioimmunotherapy approach is, in part, influenced by the targeted tumor antigen, several of which have been proposed for different solid tumors. Glypican-1 (GPC-1) is a heparan sulfate proteoglycan that is expressed in a variety of solid tumors, but whose expression is restricted in normal adult tissue. Here, we discuss the preclinical and clinical evidence for the potential of GPC-1 as a radioimmunotherapy target. We describe the current treatment paradigm for several solid tumors expressing GPC-1 and suggest the potential clinical utility of a GPC-1 directed radioimmunotherapy for these tumors.

Phase 1/2a study of 177Lu-lilotomab satetraxetan in relapsed/refractory indolent non-Hodgkin lymphoma

For patients with indolent non-Hodgkin lymphoma who fail initial anti-CD20-based immunochemotherapy or develop relapsed or refractory disease, there remains a significant unmet clinical need for new therapeutic approaches to improve outcomes and quality of life. 177Lu-lilotomab satetraxetan is a next-generation single-dose CD37-directed radioimmunotherapy (RIT) which was investigated in a phase 1/2a study in 74 patients with relapsed/refractory indolent non-Hodgkin B-cell lymphoma, including 57 patients with follicular lymphoma (FL). To improve targeting of 177Lu-lilotomab satetraxetan to tumor tissue and decrease hematologic toxicity, its administration was preceded by the anti-CD20 monoclonal antibody rituximab and the "cold" anti-CD37 antibody lilotomab. The most common adverse events (AEs) were reversible grade 3/4 neutropenia (31.6%) and thrombocytopenia (26.3%) with neutrophil and platelet count nadirs 5 to 7 weeks after RIT. The most frequent nonhematologic AE was grade 1/2 nausea (15.8%). With a single administration, the overall response rate was 61% (65% in patients with FL), including 30% complete responses. For FL with ≥2 prior therapies (n = 37), the overall response rate was 70%, including 32% complete responses. For patients with rituximab-refractory FL ≥2 prior therapies (n = 21), the overall response rate was 67%, and the complete response rate was 24%. The overall median duration of response was 13.6 months (32.0 months for patients with a complete response). 177Lu-lilotomab satetraxetan may provide a valuable alternative treatment approach in relapsed/refractory non-Hodgkin lymphoma, particularly in patients with comorbidities unsuitable for more intensive approaches. This trial was registered at www.clinicaltrials.gov as #NCT01796171.

FDG PET/CT parameters and correlations with tumor-absorbed doses in a phase 1 trial of 177Lu-lilotomab satetraxetan for treatment of relapsed non-Hodgkin lymphoma

Purpose

¹⁷⁷Lu-lilotomab satetraxetan targets the CD37 antigen and has been investigated in a first-in-human phase 1/2a study for relapsed non-Hodgkin lymphoma (NHL). Tumor dosimetry and response evaluation can be challenging after radioimmunotherapy (RIT). Changes in FDG PET/CT parameters after RIT and correlations with tumor-absorbed doses has not been examined previously in patients with lymphoma. Treatment-induced changes were measured at FDG PET/CT and ceCT to evaluate response at the lesion level after treatment, and correlations with tumor-absorbed doses were investigated.

Methods

Forty-five tumors in 16 patients, with different pre-treatment and pre-dosing regimens, were included. Dosimetry was performed based on multiple SPECT/CT images. FDG PET/CT was performed at baseline and at 3 and 6 months. SUV_max, MTV, TLG, and changes in these parameters were calculated for each tumor. Lesion response was evaluated at 3 and 6 months (PET_3months and PET_6months) based on Deauville criteria. Anatomical changes based on ceCT at baseline and at 6 and 12 months were investigated by the sum of perpendiculars (SPD).

Results

Tumor-absorbed doses ranged from 35 to 859 cGy. Intra- and interpatient variations were observed. Mean decreases in PET parameters from baseline to 3 months were ΔSUV_max-3months 61%, ΔMTV_3months 80%, and ΔTLG_3months 77%. There was no overall correlation between tumor-absorbed dose and change in FDG PET or ceCT parameters at the lesion level or significant difference in tumor-absorbed doses between metabolic responders and non-responders after treatment.

Conclusion

Our analysis does not show any correlation between tumor-absorbed doses and changes in FDG PET or ceCT parameters for the included lesions. The combination regimen, including cold antibodies, may be one of the factors precluding such a correlation. Increased intra-patient response with increased tumor-absorbed doses was observed for most patients, implying individual variations in radiation sensitivity or biology.

Trial registration

ClinicalTrials.gov Identifier (NCT01796171). Registered December 2012

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-020-05098-x.

Evaluating 225Ac and 177Lu Radioimmunoconjugates against Antibody-Drug Conjugates for Small-Cell Lung Cancer

Interest in the use of ²²⁵Ac for targeted alpha therapies has increased dramatically over the past few years, resulting in a multitude of new isotope production and translational research efforts. However, ²²⁵Ac radioimmunoconjugate (RIC) research is still in its infancy, with most prior experience in hematologic malignancies and only one reported preclinical solid tumor study using ²²⁵Ac RICs. In an effort to compare ²²⁵Ac RICs to other current antibody conjugates, a variety of RICs are tested against intractable small-cell lung cancer (SCLC). We directly compare, in vitro and in vivo, two promising candidates of each α or β^- category, ²²⁵Ac and ¹⁷⁷Lu, versus pyrrolobenzodiazepine (PBD) nonradioactive benchmarks. The monoclonal antibody constructs are targeted to either delta like 3 protein (DLL3), a recently discovered SCLC target, or CD46 as a positive control. An immunocompromised maximum tolerated dose assay is performed on NOD SCID mice, along with tumor efficacy proof-of-concept studies in vivo. We overview the conjugation techniques required to create serum-stable RICs and characterize and compare in vitro cell killing with RICs conjugated to nonspecific antibodies (huIgG1) with either native or site-specific thiol loci against tumor antigen DLL3-expressing and nonexpressing cell lines. Using patient-derived xenografts of SCLC onto NOD SCID mice, solid tumor growth was controlled throughout 3 weeks before growth appeared, in comparison to PBD conjugate controls. NOD SCID mice showed lengthened survival using ²²⁵Ac compared to ¹⁷⁷Lu RICs, and PBD dimers showed full tumor suppression with nine out of ten mice. The exploration of RICs on a variety of antibody-antigen systems is necessary to direct efforts in cancer research toward promising candidates. However, the anti-DLL3-RIC system with ²²⁵Ac and ¹⁷⁷Lu appears to be not as effective as the anti-DLL3-PBD counterpart in SCLC therapy with matched antibodies and portrays the challenges in both SCLC therapy as well as the specialized utility of RICs in cancer treatment.

Nanomedicines - Tiny particles and big challenges

After decades of research, nanotechnology has been used in a broad array of biomedical products including medical devices, drug products, drug substances, and pharmaceutical-grade excipients. But like many great achievements in science, there is a fine balance between the risks and opportunities of this new technology. Some materials and surface structures in the nanosize range can exert unexpected toxicities and merit a more detailed safety assessment. Regulatory agencies such as the United States Food and Drug Administration or the European Medicines Agency have started dealing with the potential risks posed by nanomaterials. Considering that a thorough characterization is one of the key aspects of controlling such risks this review presents the regulatory background of nanosafety assessment and provides some practical advice on how to characterize nanomaterials and drug formulations. Further, the challenges of how to maintain and monitor pharmaceutical quality through a highly complex production processes will be discussed.

Highlights of the 30th Annual Congress of the EANM, Vienna 2017: "Yes we can - make nuclear medicine great again"

The 30th Annual Congress of the European Association of Nuclear Medicine (EANM) was held in Vienna, Austria, from 21 to 25 October 2017 under the chairmanship of Professor Francesco Giammarile. As always, the Congress was a great success: more than 6,379 participants came from 90 countries from all continents. Participants were presented with an excellent programme consisting of symposia, and scientific and featured sessions, CME sessions, and plenary lectures. These lectures were devoted to nuclear medicine imaging and therapy, including hybrid imaging and molecular life sciences. Additionally, the latest technology and innovations in the field were presented, and added to the success of the Congress. This review summarizes the major scientific contributions which were selected from more than 1,900 submitted abstracts, and presented in the closing highlights session. They cover the diverse areas of nuclear medicine, with particular focus on oncology, cardiovascular science, neurology, technological innovation and novel tracers, and also other clinical sciences. A particular focus of the Congress was on targeted radionuclide-based therapies, which all show promising and great innovations. The Congress was a unique opportunity to be thoroughly updated on this research. This Highlights Lecture could only be a brief summary of the large amount of data presented and discussed during the meeting, which can be found in much greater detail in the Congress proceedings book, published as volume 44, supplement 2 of the European Journal of Nuclear Medicine and Molecular Imaging in October 2017.