68Ga-P15-041, A Novel Bone Imaging Agent for Diagnosis of Bone Metastases

Superiority of 68Ga-DOTA-FAPI-04 PET/CT to 18F-FDG PET/CT in the evaluation of different cancers with bone metastases

BACKGROUND

68Ga-DOTA-FAPI-04 is a new positron imaging agent, and its application in bone metastasis has been limited. The purpose of this retrospective study was to compare the diagnostic ability of 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT to detect bone metastases in patients with different types of cancer.

METHODS

A total of 293 patients with pathologically confirmed primary malignancies were examined with 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT within one week. Using pathological examination or follow-up CT or MRI scan as the gold standard, the diagnostic efficacy of the two methods in differentiating bone metastases was compared (p < 0.05, with statistical significance). The maximum standard uptake value (SUVmax) of the two methods for different types of bone metastasis was further compared. The SUVmax was used to compare the differences between the two methods in detecting bone metastases in different tumor types and different sites.

RESULTS

A total of 48 patients were diagnosed with bone metastasis, and 245 patients without bone metastasis. There were 376 bone metastases and 243 benign bone lesions. 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT detected 376 and 228 metastases, respectively. Sensitivity, specificity, positive and negative predictive value (PPV and NPV) and accuracy of 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT were 100.0 % vs 60.6 %, 93.8 % vs 99.2 %, 96.2 % vs 99.2 %, 100.0 % vs 62.0 % and 97.6 % vs 75.8 %, respectively. Compared with 18F-FDG, 68Ga-DOTA-FAPI-04 uptake was significantly increased in both benign bone lesions and metastases (p = 0.001). The uptake of 68Ga-DOTA-FAPI-04 for osteoblastic metastasis was also significantly higher than that of 18F-FDG (p < 0.001). In bone metastasis of lung cancer and gastric cancer, 68Ga-DOTA-FAPI-04 uptake was higher than that of 18F-FDG PET/CT (p < 0.05). Using SUVmax = 4.1 and SUVmax = 6.2 as the cutoff value by 68Ga-DOTA-FAPI-04 PET/CT and 18F-FDG PET/CT, it was possible to predict the occurrence of metastases (AUC = 0.817,95 % CI: 0.791-0.923 vs AUC =0.751,95%CI:0.626-0.875).

CONCLUSIONS

68Ga-DOTA-FAPI-04 as a novel imaging agent, can detect more bone metastases and has a higher tracer uptake level than 18F-FDG. Especially for lung and gastric cancer, 68Ga-DOTA-FAPI-04 PET/CT may be a more reliable means to detect bone metastases.

Preparation and preclinical evaluation of 68Ga-labeled alendronate analogs for diagnosis of bone metastases

Bone is one of the most common target organs for distant metastases of solid tumors, which imposes a heavy burden on society. Early diagnosis of bone metastases is of great significance and positron emission tomography (PET) imaging plays an important role in the diagnosis of bone metastases. PET tracers applied for diagnosing bone metastases are constantly being updated, but they all have certain limitations like a relatively low bone/kidney ratio or no capacity to label therapeutic radionuclides. Alendronate, a representative bisphosphonate (BP), has been usually considered the standard clinical treatment for bone related diseases. In this study, alendronate was strategically modified with different linkers in an attempt to improve target/non-target ratios and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was used as the chelator. Finally, three 68Ga-labeled tracers were successfully developed. The results showed that [68Ga]Ga-AABP1/2/3 all exhibited high radiochemical purity, biosafety, and excellent stability. In the biodistribution study of normal BALB/c mice, [68Ga]Ga-AABP3, when modified with phenylalanine and β-alanine as the linker, showed the highest bone/non-bone ratio at 1.5 h. In micro-PET/CT imaging of normal BALB/c mice, [68Ga]Ga-AABP3 showed the highest SUVmax value at the bones (2.24 ± 0.16 at 1.5 h). In micro-PET/CT imaging of the mouse model of bone metastases, compared with [68Ga]Ga-AABP1 and [68Ga]Ga-AABP2, the SUVmax in the foci after injection of [68Ga]Ga-AABP3 was the highest (2.64 ± 0.08 at 0.5 h and 2.67 ± 0.10 at 1.5 h), significantly higher than that of the contralateral normal bone. Besides, [68Ga]Ga-AABP3 showed the highest tumor/non-tumor ratio at 1.5 h. The results suggest that [68Ga]Ga-AABP3 has the potential for diagnosis of bone metastases. Furthermore, AABP3 with the chelator DOTA could also be labeled with 177Lu or 225Ac, providing possibility for further application in radioligand therapy.

First-in-human study of dosimetry, safety and efficacy for [177Lu]Lu-P15-073: a novel bisphosphonate-based radioligand therapy (RLT) agent for bone metastases

PURPOSE

Bisphosphonates are pivotal in managing bone tumors by inhibiting bone resorption. This study investigates the therapeutic potential of [177Lu]Lu-P15-073, a novel bisphosphonate, for radioligand therapy (RLT) in bone metastases.

METHODS

Ten patients (age 35 to 75) with confirmed bone metastases underwent therapy with a single dose of [177Lu]Lu-P15-073 (1,225 ± 84 MBq, or 33 ± 2 mCi). Prior to treatment, bone metastases were verified via [99mTc]Tc-MDP bone scans. Serial planar whole-body scans monitored biodistribution over a 14-day period. Dosimetry was assessed for major organs and tumor lesions, while safety was evaluated through blood biomarkers and pain scores.

RESULTS

Serial planar whole-body scans demonstrated rapid and substantial accumulation of [177Lu]Lu-P15-073 in bone metastases, with minimal uptake in blood and other organs. The absorbed dose in the critical organ, red marrow, was measured at (0.034 ± 0.010 mSv/MBq), with a notably low normalized effective dose (0.013 ± 0.005 mSv/MBq) compared to other 177Lu-labeled bisphosphonates. Persistent high uptake in bone metastases was observed, resulting in elevated tumor doses (median 3.12 Gy/GBq). Patients exhibited favorable tolerance to [177Lu]Lu-P15-073 therapy, with no new instances of side effects. Additionally, 87.5% (7/8) of patients experienced a significant reduction in pain scale (numerical rating scale, NRS, from 5.1 ± 2.3 to 3.0 ± 1.8). The tumor-background ratio (TBRmean) of [99mTc]Tc-MDP correlated significantly with [177Lu]Lu-P15-073 uptake (P < 0.01), indicating its potential for prediction of absorbed dose.

CONCLUSIONS

This study demonstrates the safety, dosimetry, and efficacy of a single therapeutic dose of [177Lu]Lu-P15-073 in bone metastases. The treatment was well-tolerated with no severe adverse events. These findings suggest that [177Lu]Lu-P15-073 holds promise as a novel RLT agent for bone metastases.

Comparison of single photon emission computed tomography-computed tomography, computed tomography and magnetic resonance imaging of medication-related osteonecrosis of jaw by new calculated parameters

BACKGROUND

This study aimed to investigate parameters for medication-related osteonecrosis of jaw (MRONJ) patients using the bone SPECT/CT, especially bone mineral-based parameters.

METHODS

Sixty-three patients with MRONJ (43 osteoporosis and 20 bone metastasises) underwent CT, MRI and SPECT/CT. A commercially available software automatically detected lesion area and calculated the quantitative SPECT/CT parameters as bone mineral-based standardized uptake value (SUV).

RESULTS

Regarding stage of MRONJ patients, bone mineral based maximum SUV of stage 3 was significantly higher than stage 1, 2 (P=0.018). Regarding duration of medication therapy, bone mineral based maximum SUV 1 year or more was significantly higher than less than 1 year (P=0.019). Regarding present of periosteal bone proliferation on CT, bone mineral based maximum SUV was significantly higher than those of absent (P=0.029). Regarding spread of soft tissue inflammation on MRI, bone mineral based maximum SUV of 2 or more was significantly higher than those of less than 2 spaces (P=0.025). Regarding blood pool phase imaging with SPECT, bone mineral based maximum SUV of intense uptake was significantly higher than those of decrease uptake (P=0.002).

CONCLUSIONS

SPECT/CT bone mineral-based parameters indicated significant difference in staging, dosing period, periosteal bone proliferation on CT, spread of soft tissue inflammation on MRI, and blood phase imaging with SPECT. Bone SPECT/CT bone mineral-based parameters are helpful for the assessment of MRONJ.

Theranostic Agent Targeting Bone Metastasis: A Novel [68Ga]Ga/[177Lu]Lu-DOTA-HBED-bisphosphonate

Bone metastasis in cancer patients is a major disease advancement for various types of cancer. Previously, [68Ga]Ga-HBED-CC-bisphosphonate ([68Ga]Ga-P15-041) showed excellent bone uptake and efficient detection of bone metastasis in patients. To accommodate different α- or β--emitting metals for radionuclide therapy, a novel DOTA-HBED-CC-bisphosphonate (P15-073, 1) was prepared and the corresponding [68Ga]Ga-1 and [177Lu]Lu-1 were successfully synthesized in high yields and purity. Gallium-68 conjugation to HBED-CC at room temperature and lutetium-177 conjugation to DOTA at 95 °C were verified in model compounds through secondary mass confirmation. These bisphosphonates, [68Ga]Ga-1 and [177Lu]Lu-1, displayed high binding affinity to hydroxyapatite in vitro. After an iv injection, it showed excellent uptake in the spine of normal mice, and micro-PET/CT imaging of nude mice model of bone metastasis showed high bone uptake in tumor tissue. The results indicated that [68Ga]Ga/[177Lu]Lu-1 holds promise as a theranostic radioligand agent for managing cancer bone metastases.

Applications and challenges in designing VHH-based bispecific antibodies: leveraging machine learning solutions

The development of bispecific antibodies that bind at least two different targets relies on bringing together multiple binding domains with different binding properties and biophysical characteristics to produce a drug-like therapeutic. These building blocks play an important role in the overall quality of the molecule and can influence many important aspects from potency and specificity to stability and half-life. Single-domain antibodies, particularly camelid-derived variable heavy domain of heavy chain (VHH) antibodies, are becoming an increasingly popular choice for bispecific construction due to their single-domain modularity, favorable biophysical properties, and potential to work in multiple antibody formats. Here, we review the use of VHH domains as building blocks in the construction of multispecific antibodies and the challenges in creating optimized molecules. In addition to exploring traditional approaches to VHH development, we review the integration of machine learning techniques at various stages of the process. Specifically, the utilization of machine learning for structural prediction, lead identification, lead optimization, and humanization of VHH antibodies.

Bisphosphonates as Radiopharmaceuticals: Spotlight on the Development and Clinical Use of DOTAZOL in Diagnostics and Palliative Radionuclide Therapy

Bisphosphonates are therapeutic agents that have been used for almost five decades in the treatment of various bone diseases, such as osteoporosis, Paget disease and prevention of osseous complications in cancer patients. In nuclear medicine, simple bisphosphonates such as 99mTc-radiolabelled oxidronate and medronate remain first-line bone scintigraphic imaging agents for both oncology and non-oncology indications. In line with the growing interest in theranostic molecules, bifunctional bisphosphonates bearing a chelating moiety capable of complexing a variety of radiometals were designed. Among them, DOTA-conjugated zoledronate (DOTAZOL) emerged as an ideal derivative for both PET imaging (when radiolabeled with 68Ga) and management of bone metastases from various types of cancer (when radiolabeled with 177Lu). In this context, this report provides an overview of the main medicinal chemistry aspects concerning bisphosphonates, discussing their roles in molecular oncology imaging and targeted radionuclide therapy with a particular focus on bifunctional bisphosphonates. Particular attention is also paid to the development of DOTAZOL, with emphasis on the radiochemistry and quality control aspects of its preparation, before outlining the preclinical and clinical data obtained so far with this radiopharmaceutical candidate.

Lu-177-Labeled Hetero-Bivalent Agents Targeting PSMA and Bone Metastases for Radionuclide Therapy

Prostate-specific membrane antigen (PSMA) is an excellent target for imaging and radionuclide therapy of prostate cancer. Recently, [177Lu]Lu-PSMA-617 (Pluvicto) was approved by the FDA for radionuclide therapy. To develop hetero-bivalent agents targeting both PSMA and bone metastasis, [177Lu]Lu-P17-079 ([177Lu]Lu-1) and [177Lu]Lu-P17-081 ([177Lu]Lu-2) were prepared. In vivo biodistribution studies of [177Lu]Lu-PSMA-617, [177Lu]Lu-1, and [177Lu]Lu-2 in mice bearing PC3-PIP (PSMA positive) tumor showed high uptake in PSMA-positive tumor (14.5, 14.7, and 11.3% ID/g at 1 h, respectively) and distinctively different bone uptakes (0.52, 6.52, and 5.82% ID/g at 1 h, respectively). PET imaging using [68Ga]Ga-P17-079 ([68Ga]Ga-1) in the same mouse model displayed excellent images confirming the expected dual-targeting to PSMA-positive tumor and bone. Results suggest that [177Lu]Lu-P17-079 ([177Lu]Lu-1) is a promising candidate for further development as a hetero-bivalent radionuclide therapy agent targeting both PSMA expression and bone metastases for the treatment of prostate cancer.

Application Progress of the Single Domain Antibody in Medicine

The camelid-derived single chain antibody (sdAb), also termed VHH or nanobody, is a unique, functional heavy (H)-chain antibody (HCAb). In contrast to conventional antibodies, sdAb is a unique antibody fragment consisting of a heavy-chain variable domain. It lacks light chains and a first constant domain (CH1). With a small molecular weight of only 12~15 kDa, sdAb has a similar antigen-binding affinity to conventional Abs but a higher solubility, which exerts unique advantages for the recognition and binding of functional, versatile, target-specific antigen fragments. In recent decades, with their unique structural and functional features, nanobodies have been considered promising agents and alternatives to traditional monoclonal antibodies. As a new generation of nano-biological tools, natural and synthetic nanobodies have been used in many fields of biomedicine, including biomolecular materials, biological research, medical diagnosis and immune therapies. This article briefly overviews the biomolecular structure, biochemical properties, immune acquisition and phage library construction of nanobodies and comprehensively reviews their applications in medical research. It is expected that this review will provide a reference for the further exploration and unveiling of nanobody properties and function, as well as a bright future for the development of drugs and therapeutic methods based on nanobodies.