Development of [177Lu]Lu-LNC1003 for radioligand therapy of prostate cancer with a moderate level of PSMA expression

Development of Novel Radiotheranostic Ligand with Positively Charged Unit Targeting Prostate-Specific Membrane Antigen

Prostate-specific membrane antigen (PSMA) is an ideal target of prostate cancer (PCa) for theranostics, combining diagnosis and therapy in the field of nuclear medicine. [177Lu]Lu-PSMA-617 is a gold standard in PSMA-targeting radioligands, whereas its rapid clearance from the tumor and high uptake in the kidney may compromise the efficacy of theranostics. In this study, we developed novel PSMA-targeting radioligands, [111In]In/[225Ac]Ac-PDI2 and [111In]In/[225Ac]Ac-PDI4, by introducing a positively charged diethylenetriamine (PEI2) or tetraethylenepentamine (PEI4) structure, respectively, to PSMA-617. In the biodistribution study, higher tumor retention and lower renal uptake of [111In]In-PDI2 and [111In]In-PDI4 were observed than those of [111In]In-PSMA-617, and [111In]In-PDI2 exhibited higher tumor-residualizing properties than [111In]In-PDI4. [111In]In-PDI2 and [111In]In-PDI4 clearly visualized PSMA-expressing tumors by single photon emission computed tomography/computed tomography (SPECT/CT). The administration of [225Ac]Ac-PDI2 led to a higher antitumor effect than [225Ac]Ac-PDI4 and [225Ac]Ac-PSMA-617. These findings suggest the utility of [111In]In/[225Ac]Ac-PDI2 as theranostic ligands for PCa.

Deciphering the Tumor Uptake of Heterobivalent (SST2/Albumin) [64Cu]Cu-NODAGA-cLAB-TATEs

Radioligands with albumin-binding moieties exhibit a great potential for the treatment of tumor diseases owing to the general finding of an increased integral tumor uptake compared to radioligands without such moieties. However, the reasons for this pharmacokinetic behavior are less explored. Herein, we focused on identifying potential mechanisms for our previously developed heterobivalent (SST2/albumin) [64Cu]Cu-NODAGA-cLAB-TATEs. For this purpose, we designed two novel derivatives that show either negligible binding to albumin or lack the SST2-targeting capability. Based on the in vivo results, we hypothesize that binding of the albumin-bound radioligand to SST2 in addition to that of the free radioligand causes the increased tumor uptake. This is supported by saturation binding analyses in the presence of albumin and compartment modeling considerations. Overall, the results of this study provide a first tentative explanation for the phenomenon of increased tumor uptake for albumin-binding radioligands, which may support the prospective design of such radioligands.

Development of Novel Gastrin-Releasing Peptide Receptor-Targeted Radioligand with Albumin Binder to Improve Accumulation in Tumor

Gastrin-releasing peptide receptor (GRPR) is a promising target for cancer radiotheranostics combining nuclear imaging with targeted radionuclide therapy. Improving the accumulation of radioligands in tumors by introducing an albumin binder (ALB) is useful to promote the efficacy of radiotheranostics. In this study, we designed and synthesized a novel GRPR-targeted radioligand [111In]In-AMTG-DA1 containing an ALB moiety to improve tumor accumulation. [111In]In-AMTG-DA1 showed marked binding ability to albumin, high affinity for GRPR, and high-level stability in vitro. In biodistribution studies, the tumor accumulation of [111In]In-AMTG-DA1 was much higher than that of the control ligand without an ALB moiety. The introduction of ALB increased the tumor area under the curve (AUC) value of [111In]In-AMTG-DA1 by 3.5 times. In a single-photon emission computed tomography (SPECT) study, [111In]In-AMTG-DA1 visualized a GRPR-expressing tumor clearly at 24 h postinjection. Our findings suggest the favorable pharmacokinetics of [111In]In-AMTG-DA1 as a GRPR-targeted radioligand exhibiting a high-level accumulation in tumors.

Dansylated Amino Acid-Modified Long-Acting PSMA Derivatives 68Ga/177Lu-LNC1011 as Prostate Cancer Theranostics

Prostate-specific membrane antigen (PSMA)-targeted radiopharmaceutical therapy has demonstrated promising potential for treating metastatic castration-resistant prostate cancer. Recently, albumin-binding motif-modified PSMA radioligands with prolonged blood circulation were developed to improve tumor uptake and therapeutic effectiveness, properties which, however, were associated with an increased risk of bone marrow toxicity. This study presents new PSMA-targeted radioligands incorporating dansylated amino acids as relatively weak and preferable albumin binders to achieve a fine balance between increased tumor accumulation, safety, and diagnostic efficacy, facilitating a unified approach to theranostics within a single molecular framework. Methods: Three novel PSMA ligands ([68Ga]Ga-Dan-Gly-PSMA, [68Ga]Ga-Dan-Nva-PSMA, and [68Ga]Ga-Dan-Phe-PSMA, denoted as [68Ga]Ga-LNC1011) were synthesized with dansylated amino acids and measured the albumin-binding properties with human serum albumin through ultrafiltration experiments. Binding affinity and PSMA-targeting specificity were investigated using a saturation binding assay and cell uptake in the PSMA-induced prostate cancer 3 cell line (PC3-PIP). PET imaging in PC3-PIP tumor-bearing mice was performed to evaluate the preclinical pharmacokinetics and diagnostic efficiency of 68Ga-labeled PSMA ligands. Tumor uptake of [177Lu]Lu-LNC1011 was evaluated through SPECT/CT imaging and biodistribution studies. Radiopharmaceutical therapy studies were conducted to systematically assess the therapeutic effect of the radioligand. Results: Three novel PSMA radioligands ([68Ga]Ga-Dan-Gly-PSMA, [68Ga]Ga-Dan-Nva-PSMA, and [68Ga]Ga-LNC1011) with various dansylated amino acids were successfully synthesized with a radiochemical yield greater than 97%. In the PC3-PIP xenograft tumor model, the tumor/heart, tumor/liver, tumor/kidney, and tumor/muscle ratios were 9.82 ± 2.35, 12.42 ± 3.71, 4.36 ± 0.29, and 52.88 ± 12.08 at 4 h after injection, respectively. Biodistribution studies confirmed the significantly higher tumor uptake of [177Lu]Lu-LNC1011 (127.36 ± 16.95 %ID/g) over [177Lu]Lu-PSMA-617 (17.44 ± 6.29 %ID/g) at 4 h after injection, and no decrease was measured for the [177Lu]Lu-LNC1011 at up to 72 h after injection, which was corroborated with SPECT imaging. A single injection of 9.3 MBq of [177Lu]Lu-LNC1011 achieved 89.43% inhibition of tumor growth, equivalent to 18.5 MBq of [177Lu]Lu-PSMA-617 (90.87%). [68Ga]Ga-LNC1011 PET/CT scans of patients with metastatic castration-resistant prostate cancer identified as many lesions as [68Ga]Ga-PSMA-11 did, confirming its diagnostic efficacy. Conclusion: 68Ga/177Lu-LNC1011, characterized by high tumor uptake and retention along with timely clearance from normal organs and tissues, thus emerges as a promising single-molecule theranostic radioligand.

Comparison of Radionuclide Drug Conjugates With Boron Neutron Capture Therapy: An Overview of Targeted Charged Particle Radiation Therapy

Targeted charged alpha- and beta-particle therapies are currently being used in clinical radiation treatments as newly developed methods for either killing or controlling tumor cell growth. The alpha particles can be generated either through a nuclear decay reaction or in situ by a nuclear fission reaction such as the boron neutron capture reaction. Different strategies have been employed to improve the selectivity and delivery of radiation dose to tumor cells based on the source of the clinically used alpha particles. As a result, the side effects of the treatment can be minimized. The increasing attention and research efforts on targeted alpha-particle therapy have been fueled by exciting results of both academic research and clinical trials. It is highly anticipated that alpha-particle therapy will improve the efficacy of treating malignant tumors. In this overview, we compare radionuclide drug conjugates (RDC) with boron neutron capture therapy (BNCT) to present recent developments in targeted alpha-particle therapy.

PSMA-targeted radioligand therapy with [177Lu]Lu-LNC1011 for metastatic castration-resistant prostate cancer: a pilot study

BACKGROUND

Preclinical studies have shown that the long-acting PSMA-targeting radiopharmaceutical [177Lu]Lu-LNC1011 based on dansylated amino acid modification had high tumor uptake and prolonged retention. This study aimed to explore its safety and efficacy in patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

Eight mCRPC patients who met the inclusion criteria received intravenous treatment with [177Lu]Lu-LNC1011. Treatment was repeated every 6 weeks for up to a maximum of 6 cycles. Molecular imaging and hematology markers were the main evaluation indicators. The primary endpoints were biochemical (PSA) response and molecular imaging response. Toxicity grading was assessed using the Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

Hematological toxicity was the primary side effect. In all patients, adverse events (AEs) after [177Lu]Lu-LNC1011 treatment were primarily characterized by decreased levels of hemoglobin, white blood cells and platelets. Grade 3 anemia was recorded in 1 patient, and grade 2 leukopenia and thrombocytopenia were recorded in 4 patients. The average systemic effective dose was 0.18 mSv/MBq, and the kidney was the organ with the highest absorbed dose (3.11 ± 0.26 mSv/MBq). Long half-life (71.30 ± 8.23 h) and high absorbed dose [5.77, (range 5.5-14 Gy/GBq)] were calculated in the lesions. All patients had a more than 50% decline of PSA during treatment, and one patient dropped to 0 ng/mL. According to assessment criteria adapted from the PERCIST v.1.0 criteria, complete response, partial response, and disease progression were observed in 2 (25%), 4 (50%), and 2 (25%) patients, respectively.

CONCLUSION

[177Lu]Lu-LNC1011 was well tolerated and had acceptable side effects for PSMA-targeted radioligand therapy. Tumor lesions received high radiation doses and had excellent responses to the treatment. Dose escalation studies in a larger number of patients are worth pursuing and necessary to confirm these results. URL OF REGISTRY: https://clinicaltrials.gov/study/NCT06809426?term=NCT06809 .

TRIAL REGISTRATION

NCT06809426, registration date: 2025-01-23.

Preliminary evaluation of a novel PSMA-targeting radiopharmaceutical [68Ga]Ga/[177Lu]Lu-NYM032 for theranostic use in prostate cancer

PURPOSE

A novel theranostic radiopharmaceutical targeting prostate-specific membrane antigen (PSMA), [68Ga]Ga/[177Lu]Lu-NYM032, was developed and its diagnostic and therapeutic potential in the treatment of prostate cancer (PCa) was preliminarily evaluated.

METHODS

The diagnostic efficacy of the PET tracer [68Ga]Ga-NYM032 was first evaluated in PSMA-positive xenograft-bearing models (LNCaP models), followed by evaluation in 10 PCa patients using [68Ga]Ga-PSMA617 a comparator. Finally, the therapeutic potential of [177Lu]Lu-NYM032 was evaluated in LNCaP models.

RESULTS

[68Ga]Ga/[177Lu]Lu-NYM032 was well-tolerated, and no adverse events were observed in the preclinical and clinical studies. [68Ga]Ga-NYM032 demonstrated PSMA specificity and high radioactive uptake in LNCaP tumors. [68Ga]Ga-NYM032 uptake (SUVmax) did not differ from [68Ga]Ga-PSMA617 uptake in the same in situ lesions at the same p.i. time point (median 9.40 vs. 6.85, P = 0.123, n = 8). Compared with [68Ga]Ga-PSMA617 uptake, [68Ga]Ga-NYM032 uptake was significantly higher in osseous metastases (median 5.10 vs. 3.88, P < 0.001, n = 48), and higher in lymph node metastases (median 7.81 vs. 5.46, n = 2). [177Lu]Lu-NYM032 showed high aggregation in the lesions of LNCaP models and long retention times. [177Lu]Lu-NYM032 could inhibit tumor progression in LNCaP models, and its therapeutic efficiency strengthened with increasing radio-dosage (18.5-74 MBq/mouse). The tumor volume in the high radio-dosage treatment group (74 MBq/mouse) was significantly smaller than that in the blank control group at 21 days p.i. (107.14 ± 13.68 mm3 vs. 1351.86 ± 249.98 mm3, P < 0.001, n = 7).

CONCLUSION

[68Ga]Ga/[177Lu]Lu-NYM032 has considerable potential as a novel and powerful theranostic radiopharmaceutical for PCa.

TRIAL REGISTRATION

The clinical evaluation of this study was registered at Clinicaltrial.gov (NCT06389695) on 29 Apr, 2024.

Two Targets, One Mission: Heterobivalent Metal-Based Radiopharmaceuticals for Prostate Cancer Imaging and Therapy

Prostate cancer (PCa) is a significant healthcare challenge, associated with considerable mortality and morbidity among men, particularly in developed countries. PCa mortality and morbidity are primarily related to its most advanced form, metastatic castration-resistant PCa (mCRPC), for which there is presently no cure. Therefore, novel therapeutic approaches to increase mCRPC survival are critically needed. Due to PCa tumor heterogeneity and a complex tumor microenvironment, the efficacy of single-target radiopharmaceuticals, such as the Food and Drug Administration-approved [177Lu]Lu-PSMA-617, is currently under reassessment. The design and development of PCa dual-target radiopharmaceuticals have garnered considerable attention, due to their benefits over single-target counterparts, namely increased therapeutic specificity and efficacy, as well as the ability to overcome the challenge of inconsistent tumor visualization caused by variable receptor expression across diverse lesions, thereby enabling more comprehensive imaging. Several PCa biomarkers are currently being investigated as potential targets for dual-target radiopharmaceuticals, including prostate-specific membrane antigen, gastrin-releasing peptide receptor, integrin αvβ3 receptor, fibroblast activation protein, sigma-1 receptor, as well as albumin, the radiosensitive cell nucleus, and mitochondria. This review explores recent advancements in heterobivalent metal-based radiopharmaceuticals for dual targeting in PCa, highlighting their significance in theranostic and personalized medicine.

Development of [225Ac]Ac‑LNC1011 for targeted alpha-radionuclide therapy of prostate cancer

PURPOSE

Prostate-specific membrane antigen (PSMA) radioligand therapy (PRLT) has become a promising option for treating metastatic castration-resistant prostate cancer (mCRPC). Radioligands labelled with the 68Ga/177Lu theranostic pair have been most widely used in the clinic for diagnosis and therapy, respectively. This study aims to develop a novel PSMA-targeted radioligand, LNC1011, radiolabeled with alpha-emitter 225Ac, to optimise pharmacokinetic properties and assess its potential for targeted alpha therapy (TAT) in prostate cancer treatment.

METHODS

LNC1011 (Dan-PSMA) was synthesised based on a PSMA-binding ligand with the addition of a dansylated amino acid. Systematic radiochemical analyses were conducted to confirm the successful synthesis and radiolabelling of [225Ac]Ac-LNC1011. Cell uptake and competition binding assays were performed in PSMA-positive PC3-PIP tumour cells to evaluate the binding affinity and PSMA targeting specificity. The pharmacokinetics properties and tumour uptake were characterised by biodistribution studies using healthy mice and a PC3-PIP xenograft mouse model injected with [225Ac]Ac-LNC1011. Radioligand therapy studies and maximum tolerated dose (MTD) assays were conducted to systematically evaluate the therapeutic efficacy and the safety of [225Ac]Ac-LNC1011.

RESULTS

[225Ac]Ac-LNC1011 was successfully radiolabelled with high radiochemical purity (> 97%) and high stability within 96 h (radiochemical purity > 96%). The high binding affinity of LNC1011 (IC50 = 16.28 nM) to PSMA was comparable to that of PSMA-617 (IC50 = 27.93 nM). Biodistribution studies confirmed that [225Ac]Ac-LNC1011 had moderate blood elimination half-life (T1/2z = 13.4 ± 0.57 h), which was at an optimised level between [225Ac]Ac-PSMA-617 (T1/2z = 5.19 ± 0.12 h) and [225Ac]Ac-PSMA-EB-01 (T1/2z = 25.18 ± 2.78 h). In addition, high tumour uptake of [225Ac]Ac-LNC1011 was identified to be 38.28 ± 10.04%ID/g at 1 h post-injection. The specific uptake gradually increased and peaked at 24 h (80.57 ± 3.00%ID/g) and persisted at a high level up to 72 h post-injection (50.58 ± 5.37%ID/g). Targeted alpha therapy results showed the complete inhibition of PC3-PIP tumour growth after administration of a single dose of 1 µCi and 0.5 µCi of [225Ac]Ac-LNC1011 similar to 0.5 µCi [225Ac]Ac-PSMA-617. At the 0.1 µCi dose level, partial remission was observed for [225Ac]Ac-LNC1011, as recurrence was found 20 days after administration. In contrast, mice treated with 0.1 µCi [225Ac]Ac-PSMA-617 showed incomplete tumour inhibition under the same conditions.

CONCLUSION

[225Ac]Ac-LNC1011 was successfully radiolabelled with high radiochemical purity and stability. With significantly improved tumour uptake and retention over PSMA-617, [225Ac]Ac-LNC1011 showed significantly better therapeutic efficacy than [225Ac]Ac-PSMA-617 for targeted alpha therapy of prostate cancer.

177Lu-Labeled Heterodimeric Agent with High Stability Targeting Neovascularization for Tumor Radioligand Therapy

Radiopharmaceutical theranostics holds significant promise in tumor diagnosis and treatment, but suboptimal tumor uptake and retention remain a persistent limitation. We have conjugated a unique albumin binder to our previously developed heterodimeric precursor HX01 and achieved a novel precursor L6, aiming to prolong circulation time and enhance tumor accumulation and retention. However, we observed that the NGR sequence of L6 was gradually rearranged to iso-DGR under alkaline conditions, resulting in decreased stability. In this study, we further modified the L6 to synthesize XH02, subsequently assessing their in vitro and in vivo properties following radiolabeling. Utilizing positron emission tomography (PET)/computed tomography (CT) imaging, single-photon emission computed tomography (SPECT)/CT imaging, and biodistribution study in BxPC-3 xenograft mice, we observed striking accumulation and retention of radiopharmaceutical within tumors. Two cycles of administration of 177Lu-XH02 displayed exceptional tumor growth inhibition in BxPC-3 tumors while causing minimal side effects. This promising result underscores the immense potential of this agent for further clinical translation and investigation.

Development of ibuprofen-modified fibroblast activation protein radioligands to improve cancer therapy

FAP-targeting radioligands are used in cancer diagnosis and therapy, but their effectiveness is limited by poor tumor uptake and retention. This study aimed to develop new radioligands using an optimized amino acid linker and ibuprofen for better pharmacokinetics. Three novel quinoline-based FAP ligands with an ibuprofen moiety were synthesized and radiolabeled with gallium-68 and lutetium-177. The synthesized FAP ligands FAPI-Ibu1, 2, 3 showed high binding affinity for FAP, with IC50 values of 1.17 ± 0.09, 0.29 ± 0.06, and 0.78 ± 0.12 nM, respectively. 177Lu-labeled FAP ligands showed stability in vitro and demonstrated significant binding to human plasma proteins as well as FAP specificity. PET imaging and biodistribution studies of 68Ga- or 177Lu-labeled FAPI-Ibu1, 2, 3 revealed improved tumor accumulation and retention. Dosimetry calculation showed that [177Lu]Lu-FAPI-Ibu3 delivered a 9.9-fold higher absorbed dose to tumor than [177Lu]Lu-FAPI-04, but only 2.6-fold higher absorbed dose to kidneys leading to 3.8-fold improvement in the tumor-to-kidney absorbed dose ratios. In the endoradiotherapy study, 18.5 MBq of [177Lu]Lu-FAPI-Ibu3 resulted in longer median survival than the equivalent dose of [177Lu]Lu-FAPI-04 (22 vs 16 days). Three ibuprofen-modified FAP radioligands significantly improved tumor uptake, retention, and growth suppression compared to [177Lu]Lu-FAPI-04, with [177Lu]Lu-FAPI-Ibu3 emerging as the most promising candidate for further clinical translational studies.

Safety, dosimetry, and efficacy of an optimized long-acting somatostatin analog for peptide receptor radionuclide therapy in metastatic neuroendocrine tumors: From preclinical testing to first-in-human study

Peptide receptor radionuclide therapy (PRRT) with radiolabeled SSTR2 agonists is a treatment option that is highly effective in controlling metastatic and progressive neuroendocrine tumors (NETs). Previous studies have shown that an SSTR2 agonist combined with albumin binding moiety Evans blue (denoted as 177Lu-EB-TATE) is characterized by a higher tumor uptake and residence time in preclinical models and in patients with metastatic NETs. This study aimed to enhance the in vivo stability, pharmacokinetics, and pharmacodynamics of 177Lu-EB-TATE by replacing the maleimide-thiol group with a polyethylene glycol chain, resulting in a novel EB conjugated SSTR2-targeting radiopharmaceutical, 177Lu-LNC1010, for PRRT. In preclinical studies, 177Lu-LNC1010 exhibited good stability and SSTR2-binding affinity in AR42J tumor cells and enhanced uptake and prolonged retention in AR42J tumor xenografts. Thereafter, we presented the first-in-human dose escalation study of 177Lu-LNC1010 in patients with advanced/metastatic NETs. 177Lu-LNC1010 was well-tolerated by all patients, with minor adverse effects, and exhibited significant uptake and prolonged retention in tumor lesions, with higher tumor radiation doses than those of 177Lu-EB-TATE. Preliminary PRRT efficacy results showed an 83% disease control rate and a 42% overall response rate after two 177Lu-LNC1010 treatment cycles. These encouraging findings warrant further investigations through multicenter, prospective, and randomized controlled trials.

Advances in Preclinical Research of Theranostic Radiopharmaceuticals in Nuclear Medicine

Theranostics of nuclear medicine refers to the combination of radionuclide imaging and internal irradiation therapy, which is currently a research hotspot and an important direction for the future development of nuclear medicine. Radiopharmaceutical is a vital component of nuclear medicine and serves as one of the fundamental pillars of molecular imaging and precision medicine. At present, a variety of radiopharmaceuticals have been developed for various targets such as fibroblast activation protein (FAP), prostate-specific membrane antigen (PSMA), somatostatin receptor 2 (SSTR2), C-X-C motif chemokine receptor 4 (CXCR4), human epidermal growth factor-2 (HER2), and integrin αvβ3, and some of them have been successfully applied in clinical practice. The radiopharmaceutical with theranostic function plays an important role in the diagnosis, treatment, efficacy evaluation, and prognosis prediction of cancers and is the key to realize the personalized treatment of tumors. This Review summarizes the preclinical research progress of theranostic radiopharmaceuticals toward the above targets in the field of nuclear medicine and discusses the prospects and development directions of radiopharmaceuticals in the future.

Current Status and Perspectives of Novel Radiopharmaceuticals with Heterologous Dual-targeted Functions: 2013-2023

Radiotracers provide molecular- and cellular-level information in a noninvasive manner and have become important tools for precision medicine. In particular, the successful clinical application of radioligand therapeutic (RLT) has further strengthened the role of nuclear medicine in clinical treatment. The complicated microenvironment of the lesion has rendered traditional single-targeted radiopharmaceuticals incapable of fully meeting the requirements. The design and development of dual-targeted and multitargeted radiopharmaceuticals have rapidly emerged. In recent years, significant progress has been made in the development of heterologous dual-targeted radiopharmaceuticals. This perspective aims to provide a comprehensive overview of the recent progress in these heterologous dual-targeted radiopharmaceuticals, with a special focus on the design of ligand structures, pharmacological properties, and preclinical and clinical evaluation. Furthermore, future directions are discussed from this perspective.

Development of [177Lu]Lu-LNC1010 for peptide receptor radionuclide therapy of nasopharyngeal carcinoma

PURPOSE

Somatostatin Receptor 2 (SSTR2)-targeted radiopharmaceutical [68Ga]Ga-DOTATATE has potential advantages in the diagnosis of nasopharyngeal carcinoma (NPC). This study introduces a novel long-lasting SSTR2 analogue, LNC1010, based on DOTATATE, a truncated Evans blue-binding moiety, and a polyethylene-glycol linker. We hypothesised that peptide receptor radionuclide therapy (PRRT) is more effective with [177Lu]Lu-LNC1010 than with [177Lu]Lu-DOTATATE in treating metastatic NPC.

METHODS

We assessed binding characteristics of LNC1010 in vitro using C666-1 NPC cells and in-vivo pharmacokinetics of [68Ga]Ga/[177Lu]Lu-LNC1010 in C666-1 NPC xenografts via PET and SPECT imaging, biodistribution studies, and PRRT, and compared them with [68Ga]Ga/[177Lu] Lu-labelled DOTATATE. Furthermore, a proof-of-concept approach for imaging and therapy was conducted in a patient with metastatic NPC.

RESULTS

LNC1010 exhibited strong uptake and specific affinity for SSTR2 in C666-1 NPC cells. PET and SPECT imaging demonstrated higher uptake and longer tumour retention of [68Ga]Ga/[177Lu]Lu-LNC1010 than [68Ga]Ga/[177Lu]Lu-DOTATATE in C666-1 NPC xenografts, indicating its suitability for PRRT applications in NPCs. Biodistribution studies confirmed the higher uptake and prolonged retention of [177Lu]Lu-LNC1010 than [177Lu]Lu-DOTATATE. In preclinical PRRT studies, [177Lu]Lu-LNC1010 showed greater inhibition of tumour growth in C666-1 NPC xenografts than [177Lu]Lu-DOTATATE. In a subsequent pilot clinical study, PRRT with [177Lu]Lu-LNC1010 achieved favourable therapeutic and negligible side effects in a patient with metastatic NPC.

CONCLUSION

[177Lu]Lu-LNC1010 demonstrated increased tumour uptake and prolonged retention in SSTR2-positive NPCs, with superior anti-tumour efficacy to that of [177Lu]Lu-DOTATATE in preclinical studies. These findings suggest that PRRT with [177Lu]Lu-LNC1010 is a promising treatment for advanced NPC, extending the clinical scope of PRRT beyond neuroendocrine tumours.

PSMA and Sigma-1 receptor dual-targeted peptide mediates superior radionuclide imaging and therapy of prostate cancer

Radionuclide therapy, in particular peptide receptor radionuclide therapy (PRRT), has emerged as a valuable means to combat malignant tumors. The specific affinity of ACUPA peptide toward prostate-specific membrane antigen (PSMA) renders the successful development of PRRT for prostate cancer. The clinical outcome of PRRT is, however, generally challenged by moderate tumor uptake and off-target toxicity. Here, we report on a novel design of Sigma-1 receptor and PSMA dual-receptor targeted peptide (S1R/PSMA-P) for superior radionuclide imaging and therapy of prostate cancer. S1R/PSMA-P was acquired with good purity and could efficiently be labeled with 177Lu to yield 177Lu-S1R/PSMA-P with high specific activity and radiostability. Interestingly, 177Lu-S1R/PSMA-P revealed greatly enhanced affinity to LNCaP cells over single-targeted control 177Lu-PSMA-617. The single photon emission computed tomography (SPECT) imaging demonstrated exceptional uptake and retention of 177Lu-S1R/PSMA-P in LNCaP tumor, affording about 2-fold better tumor accumulation while largely reduced uptake by most normal tissues compared to 177Lu-PSMA-617. The selective uptake in LNCaP tumor was also visualized by positron emission tomography (PET) with 68Ga-S1R/PSMA-P. In accordance, a single and low dosage of 177Lu-S1R/PSMA-P at 11.1 MBq effectively suppressed tumor growth without causing apparent side effects. This dual-targeting strategy presents an appealing radionuclide therapy for malignant tumors.

A proof-of-concept study on bioorthogonal-based pretargeting and signal amplify radiotheranostic strategy

BACKGROUND

Radiotheranostics differs from the vast majority of other cancer therapies in its capacity for simultaneous imaging and therapy, and it is becoming more widely implemented. A balance between diagnostic and treatment requirements is essential for achieving effective radiotheranostics. Herein, we propose a proof-of-concept strategy aiming to address the profound differences in the specific requirements of the diagnosis and treatment of radiotheranostics.

RESULTS

To validate the concept, we designed an s-tetrazine (Tz) conjugated prostate-specific membrane antigen (PSMA) ligand (DOTA-PSMA-Tz) for 68Ga or 177Lu radiolabeling and tumor radiotheranostics, a trans-cyclooctene (TCO) modified Pd@Au nanoplates (Pd@Au-PEG-TCO) for signal amplification, respectively. We then demonstrated this radiotheranostic strategy in the tumor-bearing mice with the following three-step procedures: (1) i.v. injection of the [68Ga]Ga-PSMA-Tz for diagnosis; (2) i.v. injection of the signal amplification module Pd@Au-PEG-TCO; (3) i.v. injection of the [177Lu]Lu-PSMA-Tz for therapy. Firstly, this strategy was demonstrated in 22Rv1 tumor-bearing mice via positron emission tomography (PET) imaging with [68Ga]Ga-PSMA-Tz. We observed significantly higher tumor uptake (11.5 ± 0.8%ID/g) with the injection of Pd@Au-PEG-TCO than with the injection [68Ga]Ga-PSMA-Tz alone (5.5 ± 0.9%ID/g). Furthermore, we validated this strategy through biodistribution studies of [177Lu]Lu-PSMA-Tz, with the injection of the signal amplification module, approximately five-fold higher tumor uptake of [177Lu]Lu-PSMA-Tz (24.33 ± 2.53% ID/g) was obtained when compared to [177Lu]Lu-PSMA-Tz alone (5.19 ± 0.26%ID/g) at 48 h post-injection.

CONCLUSION

In summary, the proposed strategy has the potential to expand the toolbox of pretargeted radiotherapy in the field of theranostics.

A phase 1 trial to determine the maximum tolerated dose and patient-specific dosimetry of [177Lu]Lu-LNC1003 in patients with metastatic castration-resistant prostate cancer

PURPOSE

This translational study aimed to determine the maximum tolerated dose (MTD), safety, dosimetry, and therapeutic efficacy of 177Lu-PSMA-EB-01 (denoted as [177Lu]Lu-LNC1003) in patients with metastatic castration-resistant prostate cancer (mCRPC).

METHODS

A total of 13 patients with mCRPC were recruited in this study. A standard 3 + 3 dose escalation protocol was performed. The following dose levels were ultimately evaluated: 1.11, 1.85, and 2.59 GBq/cycle. Patients received [177Lu]Lu-LNC1003 therapy for up to two cycles at a 6-week interval.

RESULTS

Patients received fractionated doses of [177Lu]Lu-LNC1003 ranging from 1.11 to 2.59 GBq per cycle. Myelosuppression was dose-limiting at 2.59 GBq, and 1.85 GBq was determined to be the MTD. The total-body effective dose for 177Lu-LNC1003 was 0.35 ± 0.05 mSv/MBq. The salivary glands were found to receive the highest estimated radiation dose, which was calculated to be 3.61 ± 2.83 mSv/MBq. The effective doses of kidneys and red bone marrow were 1.88 ± 0.35 and 0.22 ± 0.04 mSv/MBq, respectively. The tumor mean absorbed doses for bone and lymph node metastases were 8.52 and 9.51 mSv/MBq. Following the first treatment cycle, PSA decline was observed in 1 (33.3%), 4 (66.7%), and 2 (50.0%) patients at dose levels 1 (1.11 GBq), 2 (1.85 GBq), and 3 (2.59 GBq), respectively. Compared with the baseline serum PSA value, 1 (33.3%) at dose level 1 and 4 (66.6%) patients at dose level 2, presented a PSA decline after the second treatment cycle.

CONCLUSION

This phase 1 trial revealed that the MTD of [177Lu]Lu-LNC1003 is 1.85 GBq. The treatment with multiple cycles at the dose of 1.11 GBq /cycle and 1.85 GBq /cycle was well tolerated. [177Lu]Lu-LNC1003 has higher tumor effective doses in bone and lymph nodes metastases while the absorbed dose in the red bone marrow should be closely monitored in future treatment studies with higher doses and multiple cycles. The frequency of administration also needs to be further explored to assess the efficacy and side effects of [177Lu]Lu-LNC1003 treatment.

TRIAL REGISTRATION

177Lu-PSMA-EB-01 in patients with metastatic castration-resistant prostate cancer (NCT05613738, Registered 14 November 2022). URL of registry https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05613738.

Recent Pre-Clinical Advancements in Nuclear Medicine: Pioneering the Path to a Limitless Future

The theranostic approach in oncology holds significant importance in personalized medicine and stands as an exciting field of molecular medicine. Significant achievements have been made in this field in recent decades, particularly in treating neuroendocrine tumors using 177-Lu-radiolabeled somatostatin analogs and, more recently, in addressing prostate cancer through prostate-specific-membrane-antigen targeted radionuclide therapy. The promising clinical results obtained in these indications paved the way for the further development of this approach. With the continuous discovery of new molecular players in tumorigenesis, the development of novel radiopharmaceuticals, and the potential combination of theranostics agents with immunotherapy, nuclear medicine is poised for significant advancements. The strategy of theranostics in oncology can be categorized into (1) repurposing nuclear medicine agents for other indications, (2) improving existing radiopharmaceuticals, and (3) developing new theranostics agents for tumor-specific antigens. In this review, we provide an overview of theranostic development and shed light on its potential integration into combined treatment strategies.