Dosimetric analysis of 177Lu-DOTA-rituximab in patients with relapsed/refractory non-Hodgkin's lymphoma

The Rebirth of Radioimmunotherapy of Non-Hodgkin Lymphoma: The Phoenix of Nuclear Medicine?

In Greek mythology, The Phoenix is an immortal bird that dies, but then achieves new life by rising from the ashes of its predecessor. Radioimmunotherapy (RIT) of B-cell Non-Hodgkin lymphoma (NHL) is a field which once began to fly high-with FDA approval of the anti-CD20 RITs Zevalin® and Bexxar® in 2002 and 2003 respectively, as safe and effective therapies of NHL. However, despite their therapeutic efficacy, Bexxar® was withdrawn from the market by the manufacturer in 2014 due to limited commercial demand and Zevalin® has had very limited to no availability of late. I-131 rituximab is used to a limited extent in Australia, India and other countries, as well. But has RIT of NHL been (perhaps prematurely) left for dead by many? Given the current great clinical and commercial interest in radiopharmaceutical therapies of cancer, notably PSMA and SSTR targeting agents in prostate and neuroendocrine cancers, can radioimmunotherapy of NHL-like the mythical Phoenix-now rise from its ashes in an even better form to fly higher, faster, farther and longer than before?

Internal dosimetry and biodistribution of indigenously prepared 177Lu-DOTA-rituximab in lymphoma and other hematological malignancies treated with rituximab

OBJECTIVE

The aim of this study was to evaluate the biodistribution and dosimetry of lutetium-177-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (177Lu-DOTA)-rituximab in CD20+ non-Hodgkin's lymphoma and other hematological malignancies treated with rituximab.

METHODS

The standard dosimetry protocol was used, with cold rituximab infusion, then a diagnostic activity of 177Lu-DOTA-rituximab. Planar images were acquired at multiple time points. Normal organs and tumor dosimetry were performed by using organ and tumor-specific regions of interest and whole-body counts were obtained serially after pixel matched, background, scatter, and attenuation correction. The mean radiation absorbed doses were obtained from OLINDA/EXM v2.1.1 and ORIGIN software.

RESULTS

A total of 22 patients were included in this study. Prolonged blood pool clearance of 177Lu-DOTA-rituximab with long residence time in the blood pool and normal organs were observed. The whole body effective half-life was 104.5 ± 22 h. The mean total body radiation absorbed dose was 0.208 ± 0.03 mGy/MBq and the mean total body effective dose was 0.196 ± 0.05 mGy/MBq of 177Lu-DOTA-rituximab. The mean radiation absorbed doses of 0.613 ± 0.21, 1.68 ± 2, 1.01 ± 0.42, and 0.136 ± 0.02mGy/MBq were seen for the liver, spleen, kidneys, and bone marrow, respectively. Tumor lesion uptake was noticed in two patients with tumor radiation absorbed doses were 0.842 mGy/MBq in one and 9.9 mGy/MBq in the other patient. A strong correlation was obtained between the cumulative activities of radiation-absorbed doses derived from ORIGIN and OLINDA software methods at a significant P value less than 0.001.

CONCLUSION

The results of our study demonstrated favorable biodistribution and dosimetry of indigenously produced 177Lu-DOTA-rituximab in patients with CD20+ lymphoma. These results can be used for future studies of radioimmunotherapy employing 177Lu-DOTA-rituximab.

Intricacies in the Preparation of Patient Doses of [177Lu]Lu-Rituximab and [177Lu]Lu-Trastuzumab Using Low Specific Activity [177Lu]LuCl3: Methodological Aspects

The development of humanized monoclonal antibodies (MAbs) with Lutetium-177 ([177Lu]Lu3+) has brought a paradigm shift in the arena of targeted therapy of various cancers. [177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab have gained prominence due to their improved therapeutic efficacy in the treatment of lymphoma and breast cancer. The clinical dose formulation of these radiolabeled MAbs, using low specific activity [177Lu]LuCl3, requires extensive optimization of the radiolabeling protocol. The present study merits the development of a single protocol which has been optimized for conjugation of Rituximab and Trastuzumab with p-NCS-benzyl-DOTA and further radiolabeling these immunoconjugates (ICs) with low specific activity [177Lu]LuCl3. Herein, we report a consistent and reproducible protocol for clinical dose formulations of [177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab (~9.25 GBq each, equivalent to ~2 patient doses) with radiochemical yield (RCY) between 84 and 86% and radiochemical purities (RCP) >99%. The in vitro stabilities of both these radioimmunoconjugates (RICs) were retained up to 120 h post-radiolabeling, upon storage with L-ascorbic acid as stabilizer (concentration: ~ 220-240 μg/37MBq) at -20 °C. The ready-to-use formulation of clinical doses[177Lu]Lu-DOTA-Rituximab and [177Lu]Lu-DOTA-Trastuzumab has been successfully achieved by employing a single optimized protocol. While [177Lu]Lu-DOTA-Rituximab has exhibited a high degree of localization in retroperitoneal nodal mass of refractory lymphoma patient, high uptake of [177Lu]Lu-DOTA-Trastuzumab has been observed in metastatic breast carcinoma patient with multiple skeletal metastases.

Radioimmunotherapy in Oncology: Overview of the Last Decade Clinical Trials

Simple Summary

Monoclonal antibody-bearing radionuclides have been under clinical investigation over the last two decades for their use in theranostic (diagnostic and therapeutic) applications in cancer. However, despite the numerous trials that have been conducted, only two radioimmunotherapies (RIT) have been approved by the FDA for the targeted therapy of hematologic tumors expressing CD20 antigens. Moreover, RIT applications for solid cancers faced major issues—such as radiotoxicity due to low antibodies penetrance requiring substantial curative dose—where new discoveries concerning antibody engineering or radionuclides are trying to overcome. Here, we performed an overview of the last 11-year clinical trials involving RIT for solid and non-solid cancers conducted either with full antibodies or antibody fragments. We discussed the low-to-moderate efficiency of RIT compared to conventional therapies and described the last advances in clinic for antibodies carriers (F(ab′)₂, Fab′, ScFv). Finally, we discussed about the complexity of RIT as a therapy and depicted both the issues and the prospects of such a strategy.

Abstract

The specific irradiation of tumors with selective radiolabeled antibodies constitutes an attractive therapeutic approach. Consequent preclinical research has been conducted by both biologists to identify pertinent targets and to select corresponding antibodies (mAb) and by radiochemists to radiolabel mAbs. These numerous preclinical investigations have ascertained the therapeutic interest of radioimmunotherapy (RIT) protocols in mice models. Here, we summarize the clinical studies that have been performed the last decade, including clinical trials (phases I, II, and III), prospective and retrospective studies, and cases series. We thereby reported 92 clinical studies. Among them, 62 concern the treatment of hematological malignancies, and 30 concern solid tumors. For hematologic diseases, the analysis was complex due to the high discrepancy of therapeutic strategies (first-line therapy, consolidation, stem cell transplantation conditioning) as well as the high variety of malignancies that were treated. The clinical studies from the last decade failed to expand anti-CD20 RIT indications but confirmed that RIT using radiolabeled anti-CD20 remains a pertinent choice for patients with relapse follicular lymphomas. For solid tumors, the positive benefit of RIT is more mitigated, apart for few malignancies that can be treated locally. Clinical trials also demonstrated the potential of some antibody formats, such as F(ab′)₂, which has already been approved by the China State FDA under the trend name Licartin®. Despite disparate results, mAb fragments are an interesting prospect for the improvement of RIT efficiency as well as for pretargeted strategies that delay the injection of radioactive treatments from the mAb ones.