Targeted Radionuclide Therapy Research Articles

Abstract 2828: Impact of sequencing of immune checkpoint blockade and targeted radionuclide therapy on murine tumor response

Abstract Background: Sequencing of immune checkpoint inhibitors (ICI) and external beam radiation therapy (EBRT) for cancer treatment has been studied, but the optimal sequencing has yet to be determined. While some studies have noted therapeutic advantages of priming the tumor immune microenvironment with EBRT prior to ICI, others have described the benefit of modulating the tumor infiltrating lymphocyte (TIL) population with ICI before EBRT. Targeted radionuclide therapy (TRT) approaches allow investigation of how irradiation by a tumor-targeted radionuclide and differences in emission type, linear energy transfer, and dose rate affect optimal timing of ICI administration. NM600 is an alkylphosphocholine analog selectively taken up by tumors capable of chelating numerous radionuclides for comparative studies. Objective: We use two immunologically cold tumor models, MOC2 head and neck squamous cell carcinoma and B78 melanoma, to describe the influence of dose rate on type I interferon (IFN1) signaling and the effect of ICI and 90Y-, 177Lu-, and 225Ac-NM600 TRT sequences on tumor response. Methods: 90Y, 177Lu, or 225Ac were added to culture media in activities estimated using GEANT4 Monte Carlo to deliver 12 Gy to the cell monolayer. qPCR was performed on cDNA from cells irradiated with EBRT, 90Y, 177Lu, or 225Ac, and harvested on days 1, 3, or 7. In vivo dosimetry was performed using the Monte Carlo-based RAPID platform utilizing serial PET/CT or SPECT/CT imaging and/or longitudinal biodistribution. Differences over time (days 4, 7, 14, 21, 28 after RT) in TIL and systemic immune cell populations were measured by flow cytometry following no treatment, 12 Gy EBRT, or 90Y-, 177Lu-, or 225Ac-NM600 in MOC2 tumors. Mice bearing B78 tumors received 1.5 Gy 90Y-, 177Lu-, or 225Ac-NM600, or no radiation on day 1 +/- ICI (anti-CTLA4 + anti-PDL1) on days -3/0/3 (early), 4/7/10 (middle), or 11/14/17 (late). Mice were monitored for tumor growth and survival. Results: TRT and EBRT induced IFN1 responses in MOC2 cells. MOC2 cells treated every 24h with EBRT-matched 90Y/225Ac dose rates led to upregulation of IFN1-associated Ifnb1 and Mx1, mimicking radionuclide-induced responses. Increased tumor CD8/Treg ratios and decreased Tregs were observed at day 7 following all RT forms in MOC2 tumors. Long half-life 225Ac-NM600 (90Y: 65h; 177Lu: 161h; 225Ac: 240h) induced similar TIL changes at day 21. For 1.5 Gy 90Y-, 177Lu-, and 225Ac-NM600, B78 tumor growth delay and statistically significant overall survival benefit over respective TRT monotherapy and control groups was observed with early (day -3/0/3) dual ICI administration. Conclusions: These studies demonstrate novel immunomodulatory effects of α- and β- emitting TRT and the capacity to achieve substantial antitumor responses with appropriate TRT + ICI sequencing. These results may inform clinical trial design of TRT + ICI regimens for patients with metastatic cancers. Citation Format: Caroline P. Kerr, Joseph J. Grudzinski, Carolina A. Ferreira, David Adam, Julia Sheehan-Klenk, Amber M. Bates, Won Jong Jin, Ohyun Kwon, Justin C. Jagodinsky, Maria Powers, Raghava N. Sriramaneni, Paul A. Clark, Luke Zangl, Thanh Phuong T. Nguyen, Anatoly N. Pinchuk, Cynthia Choi, Christopher F. Massey, Reinier Hernandez, Bryan Bednarz, Jamey P. Weichert, Zachary S. Morris. Impact of sequencing of immune checkpoint blockade and targeted radionuclide therapy on murine tumor response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2828.

Abstract 5039: Development of a prostate cancer PDX model radioresistant to PSMA targeted radionuclide therapy

Abstract Prostate cancer is the second most common cancer diagnosis worldwide and the fifth leading cause of cancer related death among men. Lutetium Lu 177 vivivotide tetraxetetan was recently approved by the FDA for treatment of prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer. However, not all patients respond to treatment and combination therapies may improve outcomes. One approach is to combine targeted radionuclide therapy with inhibitors targeting DNA damage response pathways such as ATM/ATR inhibitors to enhance the radiosensitivity of the cancer cells. Currently, models used to study radioresistance in prostate cancer are based on cancer cell lines or cell-line derived xenograft models, but these models do not account for the heterogenous and complex biology of the disease. To overcome this issue, we aimed at developing a radioresistant PSMA positive prostate cancer patient-derived xenograft (PDX) model based on the ST1273 model (XenoSTART). ST1273 originates from a sixty-five-year-old Hispanic male that did not receive treatment prior to sampling. The model is characterized by overexpression of androgen receptor and PSMA. Tumors were implanted in nude mice and radioresistance was induced by external beam radiation therapy (3 × 2Gy per cycle) until tumor growth was unresponsive to the treatment. Flow cytometry were applied to evaluate if altered proliferation rate or changes in the tumor microenvironment (TME) convers the resistance. Out of five initially treated tumors, one tumor re-occurred after 19 days. Repeating the treatment led to an initial decrease in tumor volume but the growth delay was reduced to 12 days. A third treatment rendered the tumor resistant as tumor growth was unaffected. Current evidence confirms that radioresistance was maintained when passaging, and PSMA expression was unaffected. Next, we tested whether the tumor would also withstand targeted radionuclide therapy. Animals implanted with parental or radioresistant ST1273 tumors were treated with Lu177-PSMA-617 (5MBq, QW x2). The treatment reduced tumor size in both tumor types, but significantly less in the resistant model. Moreover, parental tumors had a significantly slower recurrence of 45 days compared to the resistant tumors that relapsed 24 days after the first dosing. Flow cytometry analysis of control and treated tumors (parental and radioresistant) showed that the radioresistance might be attributed to alterations in the cell cycle control. Altogether, we developed a PDX prostate cancer model that is resistance to external beam radiation and PSMA targeted radionuclide therapy. This model will allow us to further characterize radioresistance and evaluate combinatorial therapy in a clinically relevant model. Citation Format: Maria Thaysen, Esben Christensen, Rikke N. Nielsen, Michael Wick, Mette M. Wessel, Lotte K. Kristensen, Sebastian Gnosa, Carsten H. Nielsen. Development of a prostate cancer PDX model radioresistant to PSMA targeted radionuclide therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5039.

Abstract 6117: Dose, dose rate, and linear energy transfer influence tumor immunologic and DNA damage response following alpha- and beta-emitting radionuclides

Abstract Background: The low response rate to immunotherapies in poorly immunogenic cancers highlights the potential for combination therapies that propagate an anti-tumor response in metastatic settings. Targeted radionuclide therapy (TRT) can deliver radiation to metastatic tumor sites. In preclinical studies, combining low dose TRT with immune checkpoint blockade augments the anti-tumor immune response, promoting the immune susceptibility of metastatic disease sites. Radionuclides differ in their physical properties such as emission type, linear energy transfer (LET), half-life, and tissue range. In this study, clinically relevant α- and β-emitting radionuclides (225Ac, 90Y, 177Lu) were compared in vitro in MOC2 head and neck squamous cell carcinoma and B78 melanoma. We hypothesized that the unique physical properties of radionuclides would differentially impact the quantity and accumulation over time of double stranded DNA breaks, mirroring the timing of effects on tumor cell immune susceptibility markers. Methods: MOC2 or B78 cells were grown in culture and treated with external beam radiation (EBRT), or culture media containing 90Y, 177Lu, or 225Ac delivering continuous radiation at activity levels using GEANT4 Monte Carlo to deliver 12 Gy (MOC2) and 4 Gy (B78) to the cell monolayer. Cells were harvested, and cDNA was isolated for RT-qPCR one, three, and seven days after the start of irradiation. Additional cells treated in this manner were fixed and stained with DAPI/γ-H2AX antibody for confocal microscopy at the same timepoints. γ-H2AX foci/cell were quantified manually using ImageJ. Results: γ-H2AX foci counts/cell increased significantly and accumulated over time following treatment with 225Ac, but not with 90Y or 177Lu. EBRT, 90Y, and 225Ac, but not 177Lu, upregulated expression of immune response associated genes (Fas, Pdl1, Mhc1) compared to non-irradiated controls. In cells treated with EBRT every 24h at doses mimicking the interval dose delivered by continuous exponential decay of 90Y and 225Ac, but not 177Lu, the time course and magnitude of Fas and Pdl1 expression phenocopied that of these radionuclides. Conclusions: DNA damage accumulation and the timing of immunomodulation are modified by the dose, dose-rate, and LET of radiation emitted from a given radionuclide. Understanding the effects of radionuclide therapies on cancer cell immunogenicity could enable rational design of clinical trials that investigate the integration of TRT and immunotherapies into the clinical care of patients with metastatic cancers. Citation Format: Julia Sheehan-Klenk, Caroline P. Kerr, Thanh P. Nguyen, Joseph J. Grudzinski, David Adam, Maria Powers, Raghava N. Sriramaneni, Paul A. Clark, Reinier Hernandez, Bryan Bednarz, Jamey P. Weichert, Zachary S. Morris. Dose, dose rate, and linear energy transfer influence tumor immunologic and DNA damage response following alpha- and beta-emitting radionuclides [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6117.

Formalism of the NanOx biophysical model for radiotherapy applications

Introduction: NanOx is a theoretical framework developed to predict cell survival to ionizing radiation in the context of radiotherapy. Based on statistical physics, NanOx takes the stochastic nature of radiation at different spatial scales fully into account. It extends concepts from microdosimetry to nanodosimetry, and considers as well the primary oxidative stress. This article presents in detail the general formalism behind NanOx.Methods: Cell death induction in NanOx is modeled through two types of biological events: the local lethal events, modeled by the inactivation of nanometric sensitive targets, and the global events, represented by the toxic accumulation of oxidative stress and sublethal lesions. The model is structured into general premises and postulates, the theoretical bases compliant with radiation physics and chemistry, and into simplifications and approximations, which are required for its practical implementation.Results: Calculations performed with NanOx showed that the energy deposited in the penumbra of ion tracks may be neglected for the low-energy ions encountered in some radiotherapy techniques, such as targeted radionuclide therapy. On the other hand, the hydroxyl radical concentration induced by ions was shown to be larger for low-LET ions and to decrease faster with time compared to photons. Starting from the general formalism of the NanOx model, an expression was derived for the cell survival to local lethal events in the track-segment approximation.Discussion: The NanOx model combines premises of existing biophysical models with fully innovative features to consider the stochastic effects of radiation at all levels in order to estimate cell survival and the relative biological effectiveness of ions. The details about the NanOx model formalism given in this paper allow anyone to implement the model and modify it by introducing different approximations and simplifications to improve it, or even adapt it to other medical applications.

Abstract 581: Peptide-based theranostics targeting ANTXR1 in cancer stroma

Abstract Background: ANTXR1 is one of the pancreatic ductal adenocarcinoma (PDAC) stroma-specific cell surface markers (Ref 1), which is also overexpressed in the stroma of various cancer types. Radiotheranostics refers to the combination of molecular imaging with targeted radionuclide therapy. Recent success of radiotheranostic agents such as 177Lu-DOTATATE and 177Lu-PSMA617 heralds the vibrant expansion of radiotheranostics. Herein, we sought to develop ANTXR1 targeting peptide as a cancer stroma-targeting radiotheranostic agent. Methods: We selected A549 and NCI-H460 as ANTXR1 positive cell lines and NCI-H1437 and NCI-H358 as negative cell lines based on a proteomics database for cancer cell lines. ANTXR1-targeting peptide (PC01) was discovered using Chemistry-based Ultra-high-throughput Screening (CUSTM) platform. PC01 was conjugated with either fluorescence dye (Cy5-PC01) or chelator (DOTA-PC01). DOTA-PC01 was labeled with 68Ga. Flow cytometry and confocal microscopy were utilized to assess specific binding of the peptide. Subcutaneous tumor-bearing mice were intravenously injected with Cy5-PC01 or 68Ga-DOTA-PC01. In vivo/ex vivo fluorescence imaging (IVIS) and positron emission tomography (PET) imaging were performed. Results: In western blot analysis, H460 and A549 demonstrated high levels of expression of ANTXR1, while H1437 and H358 showed negligible levels of expression, consistent with the proteomics database. The mean fluorescence intensity of H460 was significantly higher than that of H1437 after incubation with Cy5-PC01 in flow cytometry. In confocal microscopy, the two ANTXR1 positive cell lines demonstrated higher fluorescence signals compared to the two ANTXR1 negative cell lines, which indicates the specific binding of PC01 to ANTXR1. As for in vivo experiments, timepoints of image acquisition for both IVIS and PET were 0h, 1h, 2h, and 4h after injection of the peptide. In in vivo IVIS images, tumor uptake was more prominent in H460 tumors than in H1437 tumors. Furthermore, tumor/kidney uptake ratio and tumor/liver uptake ratio of Cy5-PC01 were significantly higher in H460 tumors compared to those of H1437 tumors (P < 0.05, P < 0.05, respectively). Radiolabeling efficiency of 68Ga-DOTA-PC01 was measured to be over 95% by thin-layer chromatography. Serial PET images of 68Ga-DOTA-PC01 demonstrated an initial intense renal uptake and subsequent fast renal clearance, which is a typical biodistribution of peptide-based radiotheranostic agents. Also, the tumor uptake was more pronounced in the H460 tumors than in the H1437 tumors. Conclusion: We developed an ANTXR1 targeting peptide conjugated with DOTA for radiotheranostics. We found that PC01 demonstrated favorable biodistribution and specific in vitro/in vivo binding to ANTXR1, which prompts us to further optimize and develop a peptide-based ANTXR1 targeting radiotheranostic agent. Ref 1. Cancer Res (2022) 82 (12_Supplement): 5007 Citation Format: Shengjun Li, Jin Yeong Choi, Hye Sook Ha, Yoo Joung Oh, Song-Gil Lee, Hongyoon Choi, Hyung-Jun Im. Peptide-based theranostics targeting ANTXR1 in cancer stroma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 581.

Abstract 5038: Evaluation of anti-tumor immunity in response to [177Lu]Lu-PSMA in a mouse model of prostate cancer

Abstract [177Lu]Lu-PSMA improves progression-free and overall survival in metastatic castration resistant prostate cancer. However, the role of immune stimulation by molecularly targeted radionuclide therapy (MRT) is poorly understood. The aim of this study was to evaluate the anti-tumor immune response induced by [177Lu]Lu-PSMA. The markers of immunogenic cell death (ICD), translocation of calreticulin (CRT) to the cell membrane, HMGB1 release and ATP release, were evaluated in the RM1 cell line (PSMA-negative murine prostate carcinoma) and its derivative, RM1-PGLS (stably transduced with human PSMA and SFG-EGFp/Luc), using flow cytometry, ELISA and a luminescence detection assay respectively. The in vivo biodistribution of [177Lu]Lu-PSMA in RM1-PGLS tumor-bearing C57BL/6 mice was investigated using microSPECT-CT imaging, and the in vivo efficacy of [177Lu]Lu-PSMA was tested in RM1-PGLS tumor growth inhibition studies. Vaccination/rechallenge experiments were performed to elucidate whether [177Lu]Lu-PSMA elicits ICD in vivo. The Nanostring Pan Cancer Immune Profiling Platform was used to assess changes in the tumor immune microenvironment (TIME) in response to [177Lu]Lu-PSMA. External radiation (EBRT; 137Cs γ-radiation; 6-10 Gy) was used as a comparator treatment in most experiments. We observed a dose-dependent increase in cell surface CRT following [177Lu]Lu-PSMA and EBRT at 24 and 72 h and of HMGB1 release in response to [177Lu]Lu-PSMA and EBRT at 96 and 144 h. At 24 h following [177Lu]Lu-PSMA (60 MBq) there was a significant increase in ATP release compared to untreated samples. Collectively these data indicate [177Lu]Lu-PSMA causes ICD. A high RM1-PGLS tumor:muscle uptake ratio (210 ± 59) was noted in biodistribution experiments confirming highly specific tumor accumulation of [177Lu]Lu-PSMA. In tumor growth inhibition studies the time for tumors to reach a volume of 400 mm3 was delayed in mice treated with [177Lu]Lu-PSMA (60 MBq) compared to no treatment (30 versus 21 days; P<0.01). We showed that a subcutaneous inoculum of [177Lu]Lu-PSMA (60 MBq)-treated RM1-PGLS cells prevents tumor growth in approximately 50% of cases on rechallenge with viable RM1-PGLS cells one week later. This indicates that [177Lu]Lu-PSMA induces ICD in vivo. We observed a significant reduction in most tumor infiltrating lymphocyte (TIL) types at 2 days after in vivo exposure to [177Lu]Lu-PSMA (80 MBq), followed by an increase in TILs by Day 7. The observed pattern is similar to that after EBRT (6 Gy). There was overlap in the top 10 differentially expressed genes (treatment versus no treatment) for the [177Lu]Lu-PSMA and EBRT groups. The gene showing the greatest level of upregulation at day 7 in [177Lu]Lu-PSMA-treated tumors, IDO1, is known to be involved in immune tolerance and radioresistance. In conclusion, [177Lu]Lu-PSMA induces ICD in vitro and in vivo and modulates the TIME. Citation Format: Gemma Dias, Sarah Able, Irini Skaripa-Koukelli, Rachel Anderson, Gracie Wilson, Katherine A. Vallis. Evaluation of anti-tumor immunity in response to [177Lu]Lu-PSMA in a mouse model of prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5038.

Abstract 5084: Targeted delivery of low-dose radiation alleviates tumor resistance to CAR-T cell therapy

Abstract Purpose: Current understanding of resistance to CAR-T cell therapy in solid tumors implicates inadequate CAR-T cell potency in the immunosuppressive tumor microenvironment (TME). We have previously developed a platform using somatostatin receptor 2 (SSTR2) as a positron emission tomography (PET) reporter to detect CAR-T cell expansion and trafficking. The current study aimed to leverage SSTR2 for low-dose targeted radionuclide therapy (177Lu-DOTATATE, Lutathera), which under dosimetry guidance might enhance antitumor immunity by reprograming the TME and promoting T-cell reinvigoration. Methods: Using intercellular adhesion molecule 1 (ICAM-1) as a model antigen, we evaluated the immunomodulatory effects of low-dose radiation in a gastric cancer animal model. NSG mice were inoculated subcutaneously with firefly luciferase-expressing Hs 746T cells (0.1 × 106 per mouse) and treated 5 days later with 10 × 106 SSTR2-expressing ICAM-1 CAR-T cells. CAR-T cell expansion was monitored weekly by PET scan using 18F-NOTA-Octreotide, a radiotracer targeting SSTR2. Three weeks post-T cell infusion, a cohort of mice were injected with 7.4 MBq of 177Lu-DOTATATE via the tail vein. SPECT imaging was performed for dosimetry analysis. Tumor growth was monitored by bioluminescence imaging and tumor size measurement. Serum cytokines were analyzed. Results: Single dose 177Lu-DOTATATE treatment (delivering 1-6 Gy to tumor) improved response of established gastric cancer tumor (>1,000 mm3) that was not responsive to CAR-T cell treatment alone and significantly prolonged survival. All mice receiving CAR-T cells plus 177Lu-DOTATATE displayed rapid tumor shrinkage, with 83% of mice achieving complete remission within 3 weeks of 177Lu-DOTATATE treatment. SPECT imaging confirmed specific delivery of 177Lu-DOTATATE by tumor-infiltrating CAR-T cells, with tumor uptake of 0.43 ± 0.24 and 0.19 ± 0.08 MBq/g at 24 and 144 hours post 177Lu-DOTATATE injection, respectively. Most radioactivity reduction over time (73%) is explained by physical decay of 177Lu, indicating persistent tumor retention of 177Lu-DOTATATE. In contrast, rapid clearance of 177Lu-DOTATATE was observed in liver and kidneys. Importantly, longitudinal CAR-T cell imaging using 18F-NOTA-Octreotide revealed increased CAR-T cell expansion induced by low-dose radiation. Furthermore, we detected high levels of IFN-γ and perforin in serum after 177Lu-DOTATATE treatment, which were >10 folds higher than that in control mice receiving CAR-T cell only, indicating activation of T cells by low-dose radiation. Conclusions: We developed a translatable radioimmunotherapy platform that incorporates a FDA-approved theranostic endoradiotherapy (Lutathera) to improve tumor response to CAR-T cell therapy. The next steps would be to explore the immunomodulatory effects of low-dose radiation systematically and elucidate the mechanism of action. Citation Format: Yanping Yang, Yago Alcaina, Yogindra Vedvyas, Maria Cristina Riascos, Edward K. Fung, Brett Vaughn, Sarah M. Cheal, Irene M. Min, Claire Vanpouille-Box, Moonsoo M. Jin. Targeted delivery of low-dose radiation alleviates tumor resistance to CAR-T cell therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5084.

131I-Labeled Anti-HER2 Nanobody for Targeted Radionuclide Therapy of HER2-Positive Breast Cancer.

The unique structure of nanobodies is advantageous for the development of radiopharmaceuticals for nuclear medicine. Nanobodies targeted to human epidermal growth factor receptor 2 (HER2) can be used as tools for the imaging and therapy of HER2-overexpressing tumors. In this study, we aimed to describe the generation of a 131I-labeled anti-HER2 nanobody as a targeted radionuclide therapy (TRNT) agent for HER2-positive breast cancer. The anti-HER2 nanobody NM-02 was labeled with 131I using the iodogen method, and its radiochemical purity and stability in vitro were assessed. The pharmacokinetic profile of 131I-NM-02 was investigated in normal mice. Tumor accumulation, biodistribution, and therapeutic potential of 131I-NM-02 were evaluated in HER2-positive SKBR3 xenografts; HER2-negative MB-MDA-231 xenografts were used as the control group. 131I-NM-02 could be readily prepared with satisfactory radiochemical purity and stability in vitro. Apparent tumor uptake was observed in HER2-positive tumor-bearing mice with rapid blood clearance and favorable biodistribution. 131I-NM-02 could significantly inhibit tumor growth and extend the life of these mice with good organ compatibility. Negligible tumor accumulation and inhibitory effects of 131I-NM-02 were observed in the negative control group. 131I-NM-02 has the potential to be explored as a novel tool for TRNT of HER2-positive breast cancer.

MP29-10 PROGNOSTIC VALUE OF NEUTROPHIL-TO-LYMPHOCYTE RATIO (NLR) IN PATIENTS WITH METASTATIC CASTRATION-RESISTANT PROSTATE CANCER (MCRPC) RECEIVING PROSTATE-SPECIFIC MEMBRANE ANTIGEN (PSMA) TARGETED RADIONUCLIDE THERAPY (TRT)

You have accessJournal of UrologyCME1 Apr 2023MP29-10 PROGNOSTIC VALUE OF NEUTROPHIL-TO-LYMPHOCYTE RATIO (NLR) IN PATIENTS WITH METASTATIC CASTRATION-RESISTANT PROSTATE CANCER (MCRPC) RECEIVING PROSTATE-SPECIFIC MEMBRANE ANTIGEN (PSMA) TARGETED RADIONUCLIDE THERAPY (TRT) Judith Stangl-Kremser, Michael Sun, Benedict Ho, Joseph Thomas, Jones Nauseef, Joseph Osborne, Ana Molina, Cora Sternberg, David Nanus, Neil Bander, and Scott Tagawa Judith Stangl-KremserJudith Stangl-Kremser More articles by this author , Michael SunMichael Sun More articles by this author , Benedict HoBenedict Ho More articles by this author , Joseph ThomasJoseph Thomas More articles by this author , Jones NauseefJones Nauseef More articles by this author , Joseph OsborneJoseph Osborne More articles by this author , Ana MolinaAna Molina More articles by this author , Cora SternbergCora Sternberg More articles by this author , David NanusDavid Nanus More articles by this author , Neil BanderNeil Bander More articles by this author , and Scott TagawaScott Tagawa More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003257.10AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: PSMA TRT is a promising therapy for patients with mCRPC. Known prognostic factors for mCRPC include CALGB (Halabi) risk group and baseline circulating tumor cell (CTC) count. Here, we report associations between NLR and PSA response and overall survival (OS) in men with mCRPC treated on sequential prospective clinical trials at a single institution. METHODS: Patients treated on prospective studies from 2000 to 2021 were included in this analysis. Variables assessed: baseline neutrophil count:lymphocyte count ratio, baseline CTC count (CellSearch, favorable vs unfavorable), CALGB risk group, and administered radioactivity level. We used a Cox proportional hazards model to investigate the association between NLR and OS and logistic regression to determine the association between NLR and >50% PSA decline (PSA50). RESULTS: 180 patients were included in this analysis. Median age 71 (IQR 66-77.5), PSA 57.3 ng/mL (21.3-294.9), 80 (44.4%) prior chemotherapy, 86 (47.7%) prior abiraterone or androgen receptor signaling inhibitor, 167 (92.8%) bone metastases, 141 (78.3%) nodal metastases, 113 (62.8%) CALGB high-risk group. 94 (52.2%) received 177Lu-J591, 51 (28.3%) 177Lu-PSMA-617, 28 (15.6%) 225Ac-J591, 7 (3.9%) 90Y-J591. Median ANC 4.1 (IQR 3.1-5.1), ALC 1 (0.75-1.5), NLR 3.75 (2.63-5.92). On univariate analysis, higher NLR was associated with worse OS (HR 1.06, 95%CI 1.02-1.09, p=0.002) and trended toward lower rates of PSA50 (HR 1.08; 95% CI 0.99-1.17, p=0.067). On multivariable analysis, after controlling for CTC count and CALGB risk group, the relationship between higher NLR and worse OS persisted (HR 1.05; 95% CI 1.003-1.11, p=0.036). Stratifying patients by low vs high NLR (relative to median NLR), patients with low NLR had longer OS (23.7 vs 15 months, p=0.024). CONCLUSIONS: For patients with mCRPC receiving PSMA TRT, NLR may have prognostic implications with higher NLR associating with lower likelihood of PSA response and shorter overall survival. Source of Funding: NIH, Department of Defense, Weill Cornell Medicine, Prostate Cancer Foundation © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e384 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Judith Stangl-Kremser More articles by this author Michael Sun More articles by this author Benedict Ho More articles by this author Joseph Thomas More articles by this author Jones Nauseef More articles by this author Joseph Osborne More articles by this author Ana Molina More articles by this author Cora Sternberg More articles by this author David Nanus More articles by this author Neil Bander More articles by this author Scott Tagawa More articles by this author Expand All Advertisement PDF downloadLoading ...

Angiogenesis Imaging of Adrenocortical Carcinoma with Ga-68-NODAGA-RGD Positron Emission Tomography: Opening New Horizons in Multimodality Imaging from Theranostic Perspective.

A 53-year-old female, with a known case of adrenocortical carcinoma (ACC), underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for initial staging, which revealed FDG avid large left suprarenal mass contiguous with hypermetabolic tumor thrombus in the inferior vena cava (IVC) through the left renal vein. Thereafter, she underwent angiogenesis imaging using Ga-68-NODAGA-RGD PET/CT, which showed similar avid tracer uptake in both primary and IVC thrombus. Demonstration of RGD avidity in ACC in this case opens a new horizon for targeted radionuclide therapy (e.g., Lu-177 RGD) in selected patients, who may have limited therapeutic options.

An Engineered Probiotic Platform for Cancer Epitope-Independent Targeted Radionuclide Therapy of Solid Tumors.

Targeted radionuclide therapy (TRT) is an emerging therapeutic modality for the treatment of various solid cancers. Current approaches rely on the presence of cancer-specific epitopes and receptors against which a radiolabeled ligand is systemically administered to specifically deliver cytotoxic doses of α and β particles to tumors. In this proof-of-concept study, tumor-colonizing Escherichia coli Nissle 1917 (EcN)is utilized to deliver a bacteria-specific radiopharmaceutical to solid tumors in a cancer-epitope independent manner. In this microbe-based pretargeted approach, the siderophore-mediated metal uptake pathway is leveraged to selectively concentrate copper radioisotopes, 64 Cu and 67 Cu, complexed to yersiniabactin (YbT) in the genetically modified bacteria. 64 Cu-YbT facilitates positron emission tomography (PET) imaging of the intratumoral bacteria, whereas 67 Cu-YbT delivers a cytotoxic dose to the surrounding cancer cells. PET imaging with 64 Cu-YbT reveals persistence and sustained growth of the bioengineered microbes in the tumor microenvironment. Survival studies with 67 Cu-YbT reveals significant attenuation of tumor growth and extends survival of both MC38and 4T1 tumor-bearing mice harboring the microbes. Tumor response to this pretargeted approach correlates with promising anti-tumor immunity, with noticeable CD8+ T:Treg cell ratio. Their strategy offers a pathway to target and ablate multiple solid tumors independent of their epitope and receptor phenotype.

Tackling Issues Observed during the Development of a Liquid Chromatography Method for Small Molecule Quantification in Antibody-Chelator Conjugate.

In the context of targeted radionuclide therapy, antibody-chelator conjugates (ACCs) are an evolving class of antibody-related drugs with promising applications as tumor-targeted pharmaceuticals. Generally, a typical ACC consists of a recombinant monoclonal antibody (mAb) coupled to radionuclide via a chelating agent. Characterizing the ACC structure represents an analytical challenge since various impurities must be constantly monitored in the presence of formulation components during the quality control (QC) process. In this contribution, a reliable method devoted to the monitoring of an ACC sample, and its small molecule-related synthesis impurities, has been developed via liquid chromatography (LC). A problem-solving approach of common analytical issues was used to highlight some major issues encountered during method development. This included separation of poorly retained impurities (issue #1); interferences from the formulation components (issue #2); analysis of impurities in presence of ACC at high concentration (issue #3); and recovery of impurities during the whole analytical procedure (issue #4). To the best of our knowledge, this is the first time that a chromatographic method for the analysis of ACC synthesis impurities is presented. In addition, the developed approach has the potential to be more widely applied to the characterization of similar ACCs and other antibody-related drugs.

Synthesis and radiolabelling of PSMA-targeted derivatives containing GYK/MVK cleavable linkers.

Targeted radionuclide therapy (TRT) is a promising strategy to treat different types of cancer. TRT relies on a targeting vector used to deliver a therapeutic radionuclide specifically to the tumour site. Several low molecular weight ligands targeting the prostate-specific membrane antigen (PSMA) have been synthesized, but their pharmacokinetic properties still need to be optimized. Hereby, we describe the synthesis of new conjugates, featuring the cleavable linkers Gly-Tyr-Lys (GYK) and Met-Val-Lys (MVK), to reduce the dose delivered to the kidneys. Compounds were synthesized by solid-phase peptide synthesis (SPPS) and obtained in greater than 95% chemical purity. Radiolabelling was performed with both In-111 and Lu-177 to validate potential use of the compounds as both imaging and therapeutic agents. Radiochemical purity greater than 80% was obtained for both nuclides, but significant radiolysis was observed for the methionine-containing analogue. The results obtained thus far with the GYK-PSMA conjugate could warrant further biological investigations.

Estimation of Human Absorbed Dose of 188Re-Hynic-Bombesin Based on Biodistribution Data in Rats.

HYNIC-Bombesin (BBN) is a potential peptide for targeted radionuclide therapy in gastrin-releasing peptide receptor (GRPr)-positive malignancies. The 188Re-HYNICBBN is a promising radiopharmaceutical for use in prostate cancer therapy. The aim of this study was to estimate the absorbed dose due to 188Re-HYNIC-BBN radio-complex in human organs based on bio-distribution data of rats. In this research, using bio-distribution data of 188Re-HYNIC-BBN in rats, its radiation absorbed dose of the adult human was calculated for different organs based on the MIRD dose calculation method. A considerable equivalent dose amount of 188Re-Hynic-BBN (0.093 mGy/MBq) was accumulated in the prostate. Moreover, all other tissues except for the kidneys and pancreas approximately received insignificant absorbed doses. Since the acceptable absorbed dose for the complex was observed in the prostate, 188Re-Hynic-Bombesin can be regarded as a new potential agent for prostate cancer therapy.

Development of a multifunctional platform for near-infrared imaging and targeted radionuclide therapy for tumors

Biotin receptor (BR) is overexpressed in several human tumor cell lines and has become an important biomarker for tumor diagnosis and treatment. Therefore, much attention has been attracted in the field of developing BR-targeting agents. In clinical practice, a multifunctional platform that can be used for both diagnosis and treatment is much desirable. In this study, to improve diagnostic and therapeutic efficacy of BR-positive tumors, we developed a multifunctional platform RT-H2 to combine with the cyanine scaffold for near infrared (NIR) imaging and the radioisotope 131I for targeted radionuclide therapy (TRT). In vitro experiments showed that RT-H2 possessed favorable NIR properties and could selectively accumulate in BR-positive HeLa cells. In vivo NIR imaging of HeLa tumor-bearing mice exhibited high accumulation and long retention time (72 h) of RT-H2 in the tumor. Furthermore, RT-H2 was also employed as a carrier to develop 131I-labeled TRT agent due to its favorable properties in vivo. The radiolabeling conditions were optimized and the optimal conditions determined to be 1.2 equiv of Idogen, reaction time 4 min and room temperature, yielding the radiotracer [131I]I-RT-H2 with the radiochemical purity (RCP) of > 95% after a simple purification by a C18 column. In vitro cell experiments indicated that [131I]I-RT-H2 could specifically target Hela cells and displayed dose-dependent antitumor effect. In vivo experiments demonstrated that [131I]I-RT-H2 obviously inhibited the tumor proliferation in HeLa tumor-bearing mice within 4 weeks. All these results indicate that RT-H2 has the potential to serve as a multifunctional platform for tumor diagnosis and treatment.

Increased utilization of prostate-specific membrane antigen (PSMA)-targeted radionuclide therapy (PSMA-TRT) in African American (AA) patients at an academic medical center.

36 Background: At Weill Cornell Medicine (WCM), we have had a research program utilizing anti-PSMA mAb J591 since the year 2000. With the addition of PSMA ligand-based therapies in 2017, we have enrolled around 300 patients on investigational PSMA-TRT clinical trials. Since the approval of 177Lu-PSMA-617 (Pluvicto; Lu-177 vipivotide tetraxetan), we began standard-of-care (SOC) treatment, co-enrolling willing patients into a research registry. Recognizing the low numbers of AA patients enrolled on therapeutic clinical trials in the U.S., we made a concerted effort to increase the number of AA patients with prostate cancer (PC) enrolled on clinical trials at WCM. We retrospectively assessed the demographic data of patients enrolled on PSMA-TRT clinical trials to determine changing patterns of enrollment, and to determine if our efforts have improved access to these novel treatments for this under-represented, but high-risk population of patients. Methods: We collected demographic data (namely race and ethnicity) on patients with PC from WCM who were included on our PSMA-TRT investigational clinical trial databases or enrolled on our SOC 177Lu-PSMA-617 research registry. We used self-reported race and, when not available (due to patient death or loss of follow-up), demographic information documented in the medical record. Patients were grouped into 5-year cohorts based on either the date of consent for trial enrollment, or the start date of PSMA-TRT treatment (based on available information). Institutional tumor registry data was used as a comparator to assess the total percentage of AA patients with PC seen at WCM. Results: The percentages of patients included on PSMA-TRT clinical trials at WCM who were identified as AA were as follows: 2000-2004: 3.1% (2/65), 2005-2009: 5.1% (3/59), 2010-2014: 6.1% (2/33), and 2015-2019: 5.9% (5/85). The percentage of AA patients on PSMA-TRT studies from 2020 through July 2022 was 18.2% (16/88, inclusive of 8/72 investigational TRT subjects and 8/16 SOC registry participants). The total percentages of AA patients seen at Cornell based upon analysis of our tumor registry data were as follows: 2000-2004: 10.5% (182/1728), 2005-2009: 6.9% (250/3607), 2010-2014: 10% (326/3255), 2015-2019: 11.5% (278/2413), and 2020: 14.1%. Tumor registry data for 2021-present were not yet available. Conclusions: The percentage of AA patients on investigational PSMA-TRT trials at our institution notably increased from 2000-2019 (3.1%-6.1%) to 2020-2022 (11.1%). Moreover, 50% of those treated with 177Lu-PSMA-617 since its FDA approval and co-enrolled on our research registry identified as AA. These data suggest that outreach and increasing access to AA patients for novel PC treatment such as PSMA-TRT can result in increased numbers of underrepresented patients enrolling on clinical trials and receiving the most modern standards of care (i.e., PSMA-TRT).

Developing a novel patient-reported outcome measure for patients with prostate cancer receiving radionuclide therapy: The FACT-RNT.

130 Background: The field of targeted radionuclide therapy (RNT) for prostate cancer (PC) is growing rapidly with recent FDA approval of the first lutetium-177-PSMA-ligand. Commonly used patient-reported outcome (PRO) measures were originally designed to assess the impacts of traditional therapies (e.g., chemotherapy, surgery). We aimed to develop the first PRO measure for PC patients receiving RNT. Methods: We used a multi-step approach based on input from experts and patients. We identified symptoms and toxicities potentially relevant in the context of RNT for PC from a literature review of published trials and interviews with PC patients who had received RNT, caregivers of RNT recipients, and clinicians. We identified items to include in the measure from the Functional Assessment of Chronic Illness Therapy (FACIT) item library. Finally, we reviewed, refined, and finalized the new measure. Results: Potentially relevant symptoms/toxicities were identified by reviewing published trials (e.g., xerostomia, nausea). Interviews with PC patients who received RNT (n=29), caregivers (n=14), and clinicians (n=11) yielded additional symptoms/toxicities (e.g., fatigue, constipation). After selecting a broad and comprehensive list of items from the FACIT item library, we refined the list based on input from 9 experts in the field of RNTs and PROs from 5 institutions. Patients who received RNT for PC (n=11) reviewed the draft measure and confirmed items were relevant to RNT recipients and comprehensible. This resulted in a brief 15-item measure deemed by key stakeholders to be relevant and useful in the context of RNT for PC. Conclusions: The FACT-RNT (Functional Assessment of Cancer Therapy – Radionuclide Therapy) is a PRO new measure for RNT recipients developed through multi-step collaboration with patients, caregivers, clinicians, and international experts. The FACT-RNT can be used in RNT clinical trials and real-world settings.

Phase I results of a phase I/II study of pembrolizumab and AR signaling inhibitor (ARSI) with 225Ac-J591.

181 Background: Only a small fraction of patients with PC respond to immunotherapy; radiation increases responses. PSMA targeted radionuclide therapy (PSMA-TRT) radiates multiple sites of disease simultaneously. ARSI can lead to radiosensitization and upregulate PSMA and PD-L1 expression. We hypothesize that the addition of potent alpha-PSMA-TRT (225Ac-J591) will lead to double-stranded DNA breaks, cell death, and subsequent release of neoantigens, thereby increasing the response proportion and duration to pembrolizumab plus ARSI. Here, we present preliminary phase I results of a phase I/II study, including an unexpected cytokine release syndrome (CRS). Methods: Eligibility: Progressive mCRPC by PCWG3 criteria (at least one ARSI, no chemotherapy in the mCRPC setting). Patients received ARSI of physician’s choice, pembrolizumab (400mg every 6 weeks), and single infusion of 225Ac-J591 at two different dose levels (65 or 80 KBq/kg). The primary endpoint for phase I is determination of 225Ac-J591 dose for phase II in a pick-the-winner design. Results: 12 patients were treated (6 at 65 KBq/kg, 6 at 80 KBq/kg). 7 (58%) received enzalutamide, 3 (25%) apalutamide, and 2 (17%) darolutamide. Median age 66.5, median PSA 7.75 ng/mL, 6 (50%) CALGB intermediate risk, 4 (33%) low risk, 11 (92%) with bone metastases, 3 (25%) with nodal metastases. 7 (58%) with prior abiraterone, 6 (50%) prior enzalutamide, 5 (42%) sip-T. All patients experienced PSA decline following therapy, 6 (50%) with >50% decline. With >6 months follow-up, 4 (33%; all at 80 KBq/kg) remain progression-free and on study. Of note, 7 (58%) developed an unexpected CRS 7-14 days following treatment characterized by morbilliform rash, fever >101F, and low blood counts. Inflammatory markers were elevated: IL-6 (2.1-7.7 pg/mL), D-Dimer (306-2378 ng/mL), ferritin (361.3-513.4 ng/mL), fibrinogen (386-461 mg/dL), ESR (16-42 mm/hr). After pausing the ARSI, this reaction improved within 1 week. Thrombocytopenia and/or neutropenia occurred during this syndrome, then typically improved before counts fell again at expected nadir 4 weeks after 225Ac-J591. Overall AEs on study include: 9 (75%) thrombocytopenia (3 with g≥3; 1 g4 with PC marrow infiltration), 7 (58%) neutropenia (none g≥3), 6 (50%) nausea, 7 (58%) g1-2 fatigue, 9 (75%) g1-2 xerostomia, 7 (58%) g1 AST. In contrast to heme AEs with unexpected initial occurrence during CRS followed by typical nadir from TRT, the described non-hematologic AEs were generally independent of CRS. 4 (33%) developed typical irAEs: 2 with rash (D60, D62) and 2 hypothyroidism (D77, D82). Conclusions: Combination therapy with alpha-PSMA-TRT, ARSI, and pembrolizumab demonstrates efficacy in the phase I run-in. A key safety signal that has emerged with triplet therapy is CRS that can be managed supportively. The randomized phase II component is accruing with additional safety visits and sample collection for cytokine analysis. Clinical trial information: NCT04946370 .

Radiobiologie de la radiothérapie interne vectorisée

With several specialities approved by EMA in the last years, targeted radionuclide therapy (TRT) is undergoing a strong development and treat more and more patients. Compared to previously approved radiopharmaceuticals (e.g. Zevalin™), treatments are now fractionated (several injections) and spread over several months. The absorbed dose and absorbed dose rate, the genetic and/or epigenetic characteristics of the tumours, but also the intercellular communications such as those involving the immune system, are becoming the key parameters to be considered in order to improve the effectiveness of the treatment while protecting healthy tissue. Radiobiology, using both preclinical models and a growing number of available clinical data, should provide rational insight into both the efficacy and toxicity of this continuous low dose rate radiotherapy form for better patient management.

Genetic profiling analysis design of well-differentiated aggressive grade 2 and 3 gastroenteropancreatic neuroendocrine tumors in the phase III randomized controlled COMPOSE trial.

TPS660 Background: Deeper comprehension of gastroenteropancreatic neuroendocrine tumor (GEP-NET) characteristics has led to development of therapeutic interventions such as targeted radionuclide therapies (TRT). In the prospective, randomized, controlled, open-label, multi-center, Phase III COMPOSE trial, the radiolabeled somatostatin analogue 177Lu-edotreotide will be compared to approved standard of care with everolimus, CAPTEM or FOLFOX in patients with well-differentiated aggressive grade 2 and 3 (Ki-67 index 15−55%), somatostatin receptor positive GEP-NETS. While TRT is advantageous, a key unmet need is to identify additional markers intended to guide patient selection for TRT. This is highly relevant as TRT is a therapy of growing interest likely to be broadly available for patients with variable phenotypes. Profiling analysis as part of COMPOSE plans to analyze the genetic signature of GEP-NETS through full exome sequencing and gene expression analysis of tumor histology and longitudinal blood samples. This analysis may guide detection of pathogenic mutations in NET patients, to potentially inform treatment and surveillance strategies. Methods: Whole exome analysis of tumor-suppressor- and proto-oncogenes included in several pan-cancer panels, upstream and downstream regulators, and novel candidate genes, will be studied. Following patient consent, historical tumor biopsy and blood samples will undergo genetic analysis. Genetic profiling analysis inclusion will not impact trial involvement or disease management. DNA will be assessed to determine the impact of different types of mutations; mRNA will be assessed to confirm and quantify these assumptions and compare gene expression at different treatment phases. Samples will be analyzed in a central pathology laboratory. The aim of this analysis is to develop software that would integrate genetic data with structural and functional imaging, histopathology and phenotype information for implementation into clinical practice. Clinical trial information: NCT04919226 .