and Purpose: Human epidermal growth factor receptor 2 (HER2) is overexpressed in several cancers including breast cancer. In the treatment of HER2 positive breast cancer, patients have shown significant improvements with trastuzumab therapy. Radioimmunotherapy (RIT) utilizes an antibody targeted to a receptor overexpressed on tumors to deliver radiation to the target. RIT utilizing trastuzumab could provide an additional treatment option for HER2+ breast cancer patients. We have produced the theranostic pair [64Cu]Cu-MeCOSar-trastuzumab, for PET imaging, and [67Cu]Cu-MeCOSar-trastuzumab, for therapy via beta emission, to evaluate this Targeted Copper Theranostic (TCT) approach as an effective radioimmunotherapy. The MeCOSar chelator was conjugated to trastuzumab and subsequently radiolabeled with either copper-64 (Cu-64) or copper-67 (Cu-67). Proof of concept studies were performed using SKOV-3 tumor bearing mice, injected with one dose of [64Cu]Cu-MeCOSar-trastuzumab or [67Cu]Cu-MeCOSar-trastuzumab to compare biodistribution of the theranostic pair. Tumor uptake was assessed using PET/CT imaging and/or ex vivo biodistribution studies. In therapy studies, a single dose of saline, MeCOSar-trastuzumab, or [67Cu]Cu-MeCOSar-trastuzumab was administered and endpoints assessed. [64Cu]Cu-MeCOSar-trastuzumab and [67Cu]Cu-MeCOSar-trastuzumab showed comparable high tumor-specific uptake in biodistribution studies, with tumor uptake at 48 hours of 61 ± 6 % IA/g for [64Cu]Cu-MeCOSar-trastuzumab and 59 ± 7 % IA/g for [67Cu]Cu-MeCOSar-trastuzumab. Mice treated with [67Cu]Cu-MeCOSar-trastuzumab tolerated the treatment well with limited side effects or AEs. Treated mice also showed significant tumor growth inhibition and extended survival in a dose dependent manner compared with the control groups. The median survival was 32 days in the control groups and 102 days in the 9 MBq group. These results show high tumor uptake for [64Cu]Cu-MeCOSar-trastuzumab and [67Cu]Cu-MeCOSar-trastuzumab with very similar biodistribution profiles at 48 hours in SKOV-3 xenograft model. [67Cu]Cu-MeCOSar-trastuzumab demonstrated significant tumor growth inhibition compared to the control groups and effectively increased the survival of the treated group. This study demonstrates the potential of [67Cu]Cu-MeCOSar-trastuzumab for clinical translation. Stacey E. Rudd, Jessica Van Zuylekom, Benjamin Blyth, Matthew Harris, Paul S. Donnelly. Radioimmunotherapy using 64/67copper labelled trastuzumab in mice bearing HER2-positve xenografts as a model for breast cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 573.

and Purpose: Immune checkpoint therapy (ICT) has revolutionized cancer treatment; however, efficacy remains poor for some cancers, including small cell lung cancer (SCLC). Strategies to enhance immune responses include combining ICT with other existing cancer therapies. Targeted radioligand therapy uses a radiolabeled cancer-targeting vector, allowing for specific delivery of radiation to all tumor sites while minimizing radiation exposure to healthy tissues. Targeted Copper Theranostics (TCTs) is a targeted radioligand platform utilizing copper-64/67. We evaluated [67Cu]Cu-SARTATE in combination with ICT in a murine animal model using RP116 tumor cells. We administrated ∼5 MBq [64Cu]Cu-SARTATE to RP116 (a murine SCLC cell line expressing SSTR2) tumor-bearing immunocompetent C57BL/6 mice and assessed biodistribution and tumor uptake via PET imaging at 1, 4 and 24 h post IV injection. After completion of a dose escalation study, an efficacy study using [67Cu]Cu-SARTATE, mouse ICT analogues and the combination of [67Cu]Cu-SARTATE and ICT treatment groups in the same animal model was performed to evaluate therapeutic efficacy of copper-67-based TCT. Tumor uptake of [64Cu]Cu-SARTATE was visualized by PET imaging over the first 24 h post-injection with high tumor uptake, consistent with multiple studies previously published showing uptake in human xenograft models with the same product. Tumor uptake of [67Cu]Cu-SARTATE was confirmed by ex vivo biodistribution and Cherenkov imaging, with no significant radiotoxicity observed via body condition and body weight measurements in mice receiving injected activities up to the maximum tested dose of 30 MBq. The combination of 30 MBq [67Cu]Cu-SARTATE, with both anti-PD-L1 and anti-CTLA4, improved median survival by 3, 7, or 13 days, compared to ICT-only (anti-PD-L1 plus anti-CTLA4), [67Cu]Cu-SARTATE-only or saline-only treated groups respectively. Biodistribution studies demonstrated high tumor-specific uptake for [64Cu]- and [67Cu]-Cu-SARTATE in this mouse syngeneic SCLC model. A dose escalation study demonstrated copper-67-based TCT could be used to effectively inhibit tumor growth with minimal radiotoxicity. The combination of TCT with ICTs improved overall survival compared to single-treatment control groups. Collectively, our results demonstrate that [67Cu]Cu-SARTATE in combination with ICTs improves overall survival. [67Cu]Cu-SARTATE may prime immunologically “cold” SCLC tumors to improve responsiveness to ICTs through a synergistic response. Tumor biomarkers are being investigated to understand how immune infiltration differs depending on treatment regime. Jaclyn L. Lange, Lachlan E. Mclnnes, Kurt R. Gehlsen, Jessica Van Zuylekom, Benjamin Blyth, Stacey E. Rudd, Paul S. Donnelly, Matthew Harris. Copper-67 based targeted radioligand therapy to the somatostatin receptor 2 (SSTR2) provides added efficacy and may prime small cell lung cancer for immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2149.

Co-culture assays + human PBMC data

PDL1 expression + STM3006 pharmacokinetic studies

Epidemiological studies of Japanese atomic bomb survivors indicate that the risk of cancer from radiation exposure is higher in individuals who are relatively young at the time of exposure, with women facing a more significant risk compared to men. However, this type of data is limited for other radiation types, such as particle radiations. Low linear energy transfer (LET) carbon ions are a type of particle radiation to which humans may be exposed as cosmic radiation during long-duration space missions and as radiation passing through healthy tissue during carbon ion radiotherapy. This raises concerns about the risk of late complications, including cancer development. To address these issues, we examined the lifespan of mice after exposure to γ rays or low-LET carbon-ion beams, assessed the effects of sex and age at the time of exposure, and calculated the RBE. Male and female B6C3F1 mice of various ages (embryonic days 3, 13, and 17, and postnatal weeks 1, 3, 7, and 15) were whole-body irradiated a single time with 137Cs γ rays (662 keV) or 290-MeV/u monoenergetic carbon ions (LET, ~ 13 keV/µm), and their lifespan was analyzed. For both γ rays and carbon ions, the hazard ratio for mortality increased in a dose-dependent manner, was higher for females than for males, and peaked at 1 week of age at the time of exposure. The RBE of low-LET carbon ions for lifespan shortening was 0.9-1.8 for females and 1.2-2.0 for males, regardless of the age at exposure. Thus, the risk associated with low-LET carbon ion exposure varied with age and sex, but RBE did not. These findings provide essential data for assessing the impacts of low-LET carbon ion exposure.

Fibroblast Activation Protein (FAP), a membrane-bound enzyme and cell surface protein, is up-regulated in cancer-associated fibroblasts and is present in the tumor microenvironment across numerous cancers. There is low to no expression of FAP in healthy tissue. Targeted Copper Theranostics (TCTs) are radiopharmaceuticals that utilize copper-64 (Cu-64) for PET imaging and copper-67 (Cu-67) for therapy. Herein, we report preclinical evaluation of a mono- and bis-FAP targeting agent using Cu-64 in two FAP-positive tumor xenograft models. These agents enable the visualization of FAP as a potential pan-cancer imaging agent and therapy. We evaluated the imaging characteristics of SAR-FAP and a dimer, SAR-bisFAP, which utilize the FAP inhibitor (UAMC1110) conjugated to a sarcophagine chelator (SAR). We tested the compounds in two xenograft models which have high expression levels of FAP: NSG mice bearing a SK-MEL-187 xenograft (a human-derived metastatic cell line); or athymic nude mice bearing a U87MG xenograft (a human-derived glioblastoma cell line). The mice were administered ∼5 MBq of [64Cu]Cu-SAR-FAP or [64Cu]Cu-SAR-bisFAP and the biodistribution and tumor uptake assessed via microPET/CT imaging and ex vivo biodistribution at 1, 4 and 24 h post i.v. injection. A comparison study with [68Ga]Ga-FAPi-46 along with blocking studies with FAPi-46 (an industry standard) were also completed. Imaging and an ex-vivo biodistribution study of the SK-MEL-187 xenograft NSG mice showed that both SAR-FAP tracers have specific binding to FAP-positive SK-MEL-187 tumors and higher uptake compared to 68Ga-FAPi-46 at 1 h. Additionally, both SAR-FAP tracers show FAPi-46 blockable uptake, confirming the tracer is binding specifically to FAP. Overall, the [64Cu]Cu-SAR-bisFAP has better retention at 24 h. In the U87MG xenografted athymic nude mice, the tumor uptake, as measured via ex vivo biodistribution for the [64Cu]Cu-SAR-FAP tracer was consistent over 4 hours (4.8% IA/g) which thereafter decreased to 0.8% IA/g at 24 hours. We were again able to observe higher uptake and long retention in the tumor after 24 hours (6.2% IA/g) for the [64Cu]Cu-SAR-bisFAP. Imaging and biodistribution studies demonstrated high tumor-specific uptake for [64Cu]Cu-SAR-FAP and [64Cu]Cu-SAR-bisFAP tracers in the SK-MEL-187 and U87MG tumor xenograft mouse models. The uptake and 24-hour retention of the [64Cu]Cu-SAR-bisFAP is very encouraging and indicates potential for therapeutic benefit with this tracer. Efficacy studies are underway to ascertain the therapeutic potential of [67Cu]Cu-SAR-bisFAP as a TCT. Jaclyn L. Lange, Lachlan E. Mclnnes, Jessica Van Zuylekom, Benjamin Blyth, Stacey E. Rudd, Paul S. Donnelly, Aidan Ingham, Jason S. Lewis, Matthew Harris. Development of a targeted copper theranostic to fibroblast activation protein (FAP) which shows high uptake and long-term retention at the tumor site [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 572.

Abstract Background and Purpose: Immune checkpoint therapy (ICT) has revolutionized cancer treatment; however, efficacy remains poor for some cancers, including small cell lung cancer (SCLC). Strategies to enhance immune responses include combining ICT with other existing cancer therapies. Targeted radioligand therapy uses a radiolabeled cancer-targeting vector, allowing for specific delivery of radiation to all tumor sites while minimizing radiation exposure to healthy tissues. Targeted Copper Theranostics (TCTs) is a targeted radioligand platform utilizing copper-64/67. We evaluated [67Cu]Cu-SARTATE in combination with ICT in a murine animal model using RP116 tumor cells. Methods: We administrated ∼5 MBq [64Cu]Cu-SARTATE to RP116 (a murine SCLC cell line expressing SSTR2) tumor- bearing immunocompetent C57BL/6 mice and assessed biodistribution and tumor uptake via PET imaging at 1, 4 and 24 h post IV injection. After completion of a dose escalation study, an efficacy study using [67Cu]Cu-SARTATE, mouse ICT analogues and the combination of [67Cu]Cu-SARTATE and ICT treatment groups in the same animal model was performed to evaluate therapeutic efficacy of copper-67-based TCT. Results: Tumor uptake of [64Cu]Cu-SARTATE was visualized by PET imaging over the first 24 h post-injection with high tumor uptake, consistent with multiple studies previously published showing uptake in human xenograft models with the same product. Tumor uptake of [67Cu]Cu-SARTATE was confirmed by ex vivo biodistribution and Cherenkov imaging, with no significant radiotoxicity observed via body condition and body weight measurements in mice receiving injected activities up to the maximum tested dose of 30 MBq. The combination of 30 MBq [67Cu]Cu-SARTATE, with both anti-PD-L1 and anti-CTLA4, improved median survival by 3, 7, or 13 days, compared to ICT-only (anti-PD-L1 plus anti-CTLA4), [67Cu]Cu-SARTATE-only or saline-only treated groups respectively. Conclusion: Biodistribution studies demonstrated high tumor-specific uptake for [64Cu]- and [67Cu]-Cu-SARTATE in this mouse syngeneic SCLC model. A dose escalation study demonstrated copper-67-based TCT could be used to effectively inhibit tumor growth with minimal radiotoxicity. The combination of TCT with ICTs improved overall survival compared to single-treatment control groups. Collectively, our results demonstrate that [67Cu]Cu-SARTATE in combination with ICTs improves overall survival. [67Cu]Cu-SARTATE may prime immunologically “cold” SCLC tumors to improve responsiveness to ICTs through a synergistic response. Tumor biomarkers are being investigated to understand how immune infiltration differs depending on treatment regime. Citation Format: Jaclyn L. Lange, Kurt R. Gehlsen, Lachlan E. McInnes, Jessica Van Zuylekom, Benjamin Blyth, Stacey E. Rudd, Paul S. Donnelly, Matt Harris. Copper-67 based targeted radioligand therapy to the somatostatin receptor 2 (SSTR2) provides added efficacy and may prime small cell lung cancer for immunotherapy. [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Targeted Therapies in Combination with Radiotherapy; 2025 Jan 26-29; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(2_Suppl):Abstract nr B005.

Supplemental figures and associated legends.

Targeting MYST acetyltransferases is an exciting therapeutic opportunity in acute myeloid leukemia (AML). In this study, we define the individual and combined contribution of KAT6A, KAT6B, and KAT7 in a range of AML models, showing that although KAT6A/B inhibition is efficacious in some preclinical models, simultaneous targeting of KAT7, with the novel inhibitor PF-9363, markedly increases efficacy. KAT7 interacts with menin and the mixed lineage leukemia (MLL) complex and is colocalized at chromatin to coregulate oncogenic transcriptional programs. Focusing on MLL fusion oncoprotein (MLL-FP) AML, we show that inhibition of KAT6/KAT7 provides an orthogonal route to targeting menin to disable the transcriptional activity of the MLL-FP. Combined inhibition rapidly evicts the MLL-FP from chromatin, potently represses oncogenic transcription, and overcomes primary resistance to menin inhibitors. Notably, KAT7 remains an important targetable dependency in acquired genetic/nongenetic resistance to menin inhibition, providing the molecular rationale for rapid clinical translation of combination therapy, particularly in MLL-FP AML. SIGNIFICANCE:This study provides the molecular rationale for combined targeting of KAT6/7 and menin in MLL leukemia. It reveals that combination therapy results in a rapid and profound repression of the MLL transcriptional program leading to marked differentiation and loss of leukemia-initiating capacity, setting the platform for clinical translation.

Primer + shRNA + Taqman probe sequences

Over-expression of Human Epidermal Growth Factor Receptor 2 (HER2) is associated with a significant proportion of breast cancers. Targeting HER2 is possible with a monoclonal antibody called trastuzumab but metastatic HER2 positive tumours can develop resistance to this treatment. One approach to develop more potent therapeutic agents which retain the selectivity of trastuzumab is to attach a β- emitting radionuclide, such as copper-67, to the antibody for radioimmunotherapy. It is also possible to attach β+ emitting copper-64 to antibodies for diagnostic imaging with positron emission tomography (PET). In this work, a cage amine sarcophagine (Sar) chelator is conjugated to trastuzumab to give Sar-trastuzumab which can be radiolabelled with either copper-64 or copper-67 at room temperature in minutes to give [64Cu]CuSar-trastuzumab and [67Cu]CuSar-trastuzumab respectively. The diagnostic imaging potential of [64Cu]CuSar-trastuzumab was evaluated in mice bearing HER2+ SKOV-3 tumours showing that the tracer has very high tumour uptake and retention 48 hours after injection. The copper-67 variant, [67Cu]CuSar-trastuzumab, was highly therapeutically efficacious in the same tumour model with no signs of radiotoxicity. The combination of diagnostic PET imaging with [64Cu]CuSar-trastuzumab to guide radionuclide therapy with [67Cu]CuSar-trastzumab has significant potential for theranostic treatment of breast cancer and other HER2+ disease that has become resistant to conventional immunotherapy.

Abstract Melanoma, a highly metastatic skin cancer, exhibits variations in prognosis and response to therapy based on the site of metastasis. Despite the success of immunotherapy and targeted therapies in melanoma, over half of metastatic melanoma patients will experience disease progression due to therapy resistance. The heterogeneity and plasticity of melanoma cells contribute to metastatic dissemination and therapy resistance. Our aim is to determine whether distinct clones and/or their transcriptional cell states can predict the formation of tumors in various organs and assess how these clones change over time. To identify melanoma clones across different metastatic sites, NOD scid gamma (NSG) mice and C57BL/6 mice were injected subcutaneously, intravenously or intracranially with the same pool of cells of barcoded luciferase expressing YUMMER1.7 murine melanoma cells. Transduction conditions ensured that one DNA barcode integrated into cell genomes at one barcode per cell, serving as a lineage tag. Bioluminescence imaging was performed once a week to monitor tumor growth of mice injected intravenously and intracranially. Subcutaneous tumors were measured by calliper. Mice were euthanized at different time points; day 8, 15, 22, 29 post-implantation and at ethical endpoints. Tumors were harvested and DNA sequencing was performed to identify barcodes expressed by the tumor cells. All mice developed tumors, with 100% penetrance in NSG mice. However, in C57BL/6 mice, 10% of mice intravenously injected and 27% of subcutaneously implanted mice showed complete lesion regression, suggesting that the immune system may be responsible for tumor regression. Analysis of barcodes allowed us to assess the heterogeneity of melanoma tumors at different metastatic sites and their evolution over time. Lineage tracing and clonal heterogeneity will be evaluated using the state of art technology, SPLINTR (Single-cell Profiling and LINeage Tracing), enabling us to match a cells evolution with changes in transcriptional states. Barcode analysis performed before implanting the cells and, at different timepoints in subcutaneous and lung tumors showed that dominant subclones at the baseline were also dominant in subcutaneous and lung tumors in immunocompromised mice. In contrast, dominant subclones in immunocompetent mice was those present in lower proportion at baseline. Additionally, greater variability of subclones was observed especially in lung and brain tumors, across immunocompetent mice, likely as a mechanism of resistance, enabling these tumors to overcome immunoediting. Understanding the variability of clonality between different metastatic sites and over time will improve our comprehension of the role of different subclones in organ- specific metastasis and their transcriptional cell states. Citation Format: Veronica L. Aedo Lopez, Reem Saleh, Benjamin Blyth, Xin Du, Dane Vassiliadis, Katie Fennell, Davide Moi, Roberta Mazzieri, Riccardo Dolcetti, Karen E. Sheppard, Grant A. McArthur. Intra- and inter-tumoral heterogeneity of melanoma across different metastatic sites [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr B001.

Peptides are ideal for theranostic development as they afford rapid target accumulation, fast clearance from background tissue, and exhibit good tissue penetration. Previously, we developed a novel series of peptides that presented discreet folding propensity leading to an optimal candidate [68Ga]Ga-DOTA-GA1 ([D-Glu]6-Ala-Tyr-NMeGly-Trp-NMeNle-Asp-Nal-NH2) with 50 pM binding affinity against cholecystokinin-2 receptors (CCK2R). However, we were confronted with challenges of unfavorably high renal uptake. Methods: A structure activity relationship study was undertaken of the lead theranostic candidate. Prudent structural modifications were made to the peptide scaffold to evaluate the contributions of specific N -terminal residues to the overall biological activity. Optimal candidates were then evaluated in nude mice bearing transfected A431-CCK2 tumors, and their biodistribution was quantitated ex vivo. Results: We identified and confirmed that D-Glu3 to D-Ala3 substitution produced 2 optimal candidates, [68Ga]Ga-DOTA-GA12 and [68Ga]Ga-DOTA-GA13. These radiopeptides presented with high target/background ratios, enhanced tumor retention, excellent metabolic stability in plasma and mice organ homogenates, and a 4 -fold reduction in renal uptake, significantly outperforming their non-alanine counterparts. Conclusions: Our study identified novel radiopharmaceutical candidates that target the CCK2R. Their high tumor uptake and reduced renal accumulation warrant clinical translation.

Abstract Although immune checkpoint inhibitors (ICIs) have revolutionized melanoma treatment, many individuals either show no response or eventually develop acquired resistance. This variability could be linked to differences in the tumor immune microenvironment, pre-existing drug-resistant cells or treatment induced changes in melanoma cell states. Using single cell RNA sequencing (scRNA-seq) coupled with heritable barcodes, this study aims to lineage trace changes in melanoma transcriptional cell states and map changes in the tumor immune microenvironment to uncover if preexisting and/or therapy-induced melanoma transcriptional cell states lead to resistance to ICIs. In this study, we used YUMMER1.7 mouse melanoma cells which were transduced with barcodes under conditions that allow delivery of a single unique barcode to each cell, this served as a cell lineage tag. Each barcode is heritable and stably transcribed into RNA molecules so that individual barcoded cells can be matched with a gene expression profile from scRNA-seq outputs. The barcoded cells were subcutaneously injected into C57BL/6 mice, and once tumors were established, mice were treated with 3 cycles of anti-PD-1 and anti-CTLA-4 therapy. Lineage tracing and scRNA-seq analyses were performed on tumors harvested prior to treatment, early on treatment (Day 6), during minimal residual disease (Day 13) and upon relapse. Early on treatment (Day 6)- two tumour groups were harvested, those that responded well and others that only partially responded. Our results showed that during the early on treatment phase (Day 6) tumors that responded well and those that only partially responded displayed distinct barcodes. Additionally, prevalent barcoded cells identified at the minimal residual disease phase were also dominant upon relapse. Analysis of the transcriptional states is underway to determine if ICI therapy induces transcriptional heterogeneity in sensitive and tolerant cells and if a particular or several transcriptional states lead to relapse. This study will potentially identify predictive response biomarkers and vulnerabilities of ICI naïve and resistant cells that could be targeted to improve outcomes for melanoma patients. We will also identify neoadjuvant approaches, to remove the inherent heterogeneity within the tumor cell population, facilitating a more uniform sensitivity to ICIs. Citation Format: Reem Saleh, Riyaben Patel, Dane Vassiliadis, Fayrouz Hammal, Benjamin Blyth, Xin Du, Katie Fennell, Mark A. Dawson, Grant A. McArthur, Karen Sheppard. Single cell RNA-sequencing coupled with lineage tracing identifies novel clonal populations associated with immunotherapy resistance [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C044.

[177Lu]Lu-PSMA 177 Lu]Lu-PSMA is an effective class of therapy for patients with metastatic castration-resistant prostate cancer (mCRPC); however, progression is inevitable. The limited durability of response may be partially explained by the presence of micrometastatic deposits, which are energy-sheltered and receive low absorbed radiation with 177 Lu due to the approximately 0.7-mm mean pathlength. 161 Tb has abundant emission of Auger and conversion electrons that deposit a higher concentration of radiation over a shorter path, particularly to single tumor cells and micrometastases. 161 Tb has shown in vitro and in vivo efficacy superior to that of 177 Lu. We aim to demonstrate that [161Tb]Tb-PSMA-I&T 161 Tb]Tb-PSMA-I&T will deliver effective radiation to sites of metastatic prostate cancer with an acceptable safety profile. Methods: This single-center, single-arm, phase I/II trial will recruit 30 patients with mCRPC. Key eligibility criteria include a diagnosis of mCRPC with progression after at least one line of taxane chemotherapy (unless medically unsuitable) and androgen receptor pathway inhibitor; prostate-specific membrane antigen-positive disease on [68Ga]Ga- 68 Ga]Ga- PSMA-11 or [18F]DCFPyL 18 F]DCFPyL PET/CT (SUVmax max >= 20); no sites of discordance on [18F]FDG 18 F]FDG PET/CT; adequate bone marrow, hepatic, and renal function; an Eastern Cooperative Oncology Group performance status of no more than 2, and no prior treatment with another radioisotope. The dose escalation is a 3 1 3 design to establish the safety of 3 pre- specified activities of [161Tb]Tb-PSMA-I&T 161 Tb]Tb-PSMA-I&T (4.4, 5.5, and 7.4 GBq). The maximum tolerated dose will be defined as the highest activity level at which a dose-limiting toxicity occurs in fewer than 2 of 6 participants. The dose expansion will include 24 participants at the maximum tolerated dose. Up to 6 cycles of [161Tb]Tb-PSMA-I&T 161 Tb]Tb-PSMA-I&T will be administered intravenously every 6 wk, with each subsequent activity reduced by 0.4 GBq. The coprimary objectives are to establish the maximum tolerated dose and safety profile (Common Terminology Criteria for Adverse Events version 5.0) of [161Tb]Tb-PSMA-I&T. 161 Tb]Tb-PSMA-I&T. Secondary objectives include measuring absorbed radiation dose (Gy), evaluating antitumor activity (prostate-specific antigen 50% response rate, radiographic and prostate-specific antigen progression-free survival, overall survival, objective response rate), and evaluating pain (Brief Pain Inventory- Short Form) and health-related quality of life (Functional Assessment of Cancer Therapy-Prostate and Functional Assessment of Cancer Therapy-Radionuclide Therapy). Conclusion: Enrollment was completed in February 2024. Patients are still receiving [161Tb]Tb-PSMA-I&T. 161 Tb]Tb-PSMA-I&T.

Understanding the molecular pathogenesis of MLL fusion oncoprotein (MLL-FP) leukaemia has spawned epigenetic therapies that have improved clinical outcomes in this often-incurable disease. Using genetic and pharmacological approaches, we define the individual and combined contribution of KAT6A, KAT6B and KAT7, in MLL-FP leukaemia. Whilst inhibition of KAT6A/B is efficacious in some pre-clinical models, simultaneous targeting of KAT7, with the novel inhibitor PF-9363, increases the therapeutic efficacy. KAT7 interacts with Menin and the MLL complex and is co-localised at chromatin to co-regulate the MLL-FP transcriptional program. Inhibition of KAT6/KAT7 provides an orthogonal route to targeting Menin to disable the transcriptional activity of MLL-FP. Consequently, combined inhibition rapidly evicts the MLL-FP from chromatin, potently represses oncogenic transcription and overcomes primary resistance to Menin inhibitors. Moreover, PF-9363 or genetic depletion of KAT7 can also overcome acquired genetic/non-genetic resistance to Menin inhibition. These data provide the molecular rationale for rapid clinical translation of combination therapy in MLL-FP leukaemia.

Peptide receptor radionuclide therapy (PRRT) using 177Lutetium-DOTA-octreotate (LuTate) for neuroendocrine tumours (NET) is now an approved treatment available in many countries, though primary or secondary resistance continue to limit its effectiveness or durability. We hypothesised that a genome-wide CRISPR/Cas9 screen would identify key mediators of response to LuTate and gene targets that might offer opportunities for novel combination therapies for NET patients.Methods: We utilised a genome-wide CRISPR-Cas9 screen in LuTate-treated cells to identify genes that impact on the sensitivity or resistance of cells to LuTate. Hits were validated through single-gene knockout. LuTate-resistant cells were assessed to confirm LuTate uptake and retention, and persistence of somatostatin receptor 2 (SSTR2) expression. Gene knockouts conferring LuTate sensitivity were further characterised by pharmacological sensitisation using specific inhibitors and in vivo analysis of the efficacy of these inhibitors in combination with LuTate.Results: The CRISPR-Cas9 screen identified several potential targets for both resistance and sensitivity to PRRT. Two gene knockouts which conferred LuTate resistance in vitro, ARRB2 and MVP, have potential mechanisms related to LuTate binding and retention, and modulation of DNA-damage repair (DDR) pathways, respectively. The screen showed that sensitivity to LuTate treatment in vitro can be conferred by the loss of a variety of genes involved in DDR pathways, with loss of genes involved in Non-Homologous End-Joining (NHEJ) being the most lethal. Loss of the key NHEJ gene, PRKDC (DNA-PK), either by gene loss or inhibition by two different inhibitors, resulted in significantly reduced cell survival upon exposure of cells to LuTate. In SSTR2-positive xenograft-bearing mice, the combination of nedisertib (a DNA-PK specific inhibitor) and LuTate produced a more robust control of tumour growth and increased survival compared to LuTate alone.Conclusions: DDR pathways are critical for sensing and repairing radiation-induced DNA damage, and our study shows that regulation of DDR pathways may be involved in both resistance and sensitivity to PRRT. Additionally, the use of a DNA-PK inhibitor in combination with LuTate PRRT significantly improves the efficacy of the treatment in pre-clinical models, providing further evidence for the clinical efficacy of this combination.