- Section snippets
- INTRODUCTION
- Materials
- Radiosynthesis
- Study Design
- Quality Control (QC) of the Radiopharmaceutical
- DISCUSSION
- LIMITATIONS
- CONCLUSION
- Leadership Roles
- Data Statement
- Funding
- Declaration of Competing Interest
- Therapeutic potential of [177Lu]Lu-DOTAGA-FAPi dimers in metastatic breast cancer patients with limited treatment options: efficacy and safety assessment
- Abstract
- Similar articles
- Cited by
- References
- MeSH terms
- Substances
- LinkOut — more resources
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- Medical
- Miscellaneous
- Abstract
- MATERIALS AND METHODS
- Preparation of Radiolabeled sdAbs
- Animal Models
- Biodistribution of Radiolabeled sdAbs
- Toxicity Assessment of Therapeutic [131I]I-GMIB-4AH29 and [225Ac]Ac-DOTA-4AH29
- Therapeutic Efficacy of [131I]I-GMIB-4AH29 and [225Ac]Ac-DOTA-4AH29
- Statistical Analysis
- RESULTS
- Generation and In Vitro and In Vivo Screening of Anti-FAP sdAbs
- Conjugation and Radiolabeling of sdAbs
- Cell Binding and Immunoreactivity
- Imaging, Biodistribution, and Dosimetry
- Toxicity Assessment
- Therapeutic Efficacy
- DISCUSSION
- DISCLOSURE
- KEY POINTS
- ACKNOWLEDGMENTS
- Footnotes
- REFERENCES
- Fibroblast Activation Protein Targeting Probe with Gly-Pro Sequence for PET of Glioblastoma
- Abstract
- Similar articles
- Cited by
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- LinkOut — more resources
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Section snippets
INTRODUCTION
18F-FDG PET-CT is the standard-of-care in the diagnosis, staging and response assessment of many malignancies. The glucose analog is an excellent metabolic marker that assists the imaging of over-expression of GLUT receptors within the tumor, which is a well-acknowledged hallmark of cancer (1). However, in view of it’s limitations in certain malignancies, there’s a growing emphasis on radiopharmaceuticals targeting molecular pathways such as tumor cell proliferation, angiogenesis, hypoxia and
Materials
SA.FAPi, Hydrochloric acid (HCl) (Merck), Sodium Acetate (Sigma Aldrich), Sodium Citrate (Advanced Biochemical Compounds), Ethanol (Laboratory grade, Honeywell, Riedel-de-Haen™), 0.9% Saline (Otsuka, India), C18 catridge (Sep-Pak), 0.22 µm filter (Millex ® -GV), silica-coated Instant Thin Layer Chromatography (ITLC) strips (Sigma Aldrich), Whatmann Paper III strips (Sigma Aldrich), Acetonitrile (Sigma Aldrich), High Purity Liquid Chromatography (HPLC) Water (Merck), Fluid Thioglycollate Medium
Radiosynthesis
Study Design
This prospective study was duly approved by the Institutional Ethics Committee (IEC INT/IEC/2021/SPL-500). 25 diagnosed/suspected cases of localized or metastatic ACC, GB Ca and Breast Ca were recruited for FDG and 68Ga-SA.FAPi PET for disease evaluation and comparative analysis. All the patients were above 18 years of age. Patients who refused to provide a written informed consent, pregnant and lactating females, or facing difficulty to undergo two scans due to other serious illness were
Quality Control (QC) of the Radiopharmaceutical
The radiochemical yield (RCY) for 68Ga-SA.FAPi was 98.06 ± 1.4%. The half-life measured using the dose calibrator was 69 ± 1.2 min. The gamma ray spectrum of the radiolabelled product showed a prominent peak corresponding to photon energy of 511 keV and a small sum peak corresponding to 1022 keV. No peak was observed in the gamma ray spectrum at 24 and 48 h. Based upon gamma spectrum and half-life measurement, the RNP of the radiolabelled product was > 99%. The RCP of the labeled product
DISCUSSION
FDG plays a pivotal role in numerous oncological and non-oncological applications. The era of personalized medicine has caused a paradigm shift focusing towards CAF’s in the TME characterized by increased FAP expression 3, 4, 5, 6, 7, 8, 9, 10, 13. Quinoline-based FAP inhibitors have shown promise in clinical studies 27, 28. While 68Ga-SA.FAPi displayed strong pre-clinical results, multi-centric studies are essential for global clinical validation. This prospective study assessed the diagnostic
LIMITATIONS
Our study features a small sample size, heterogenous cohort with both FDG-avid and non-avid malignancies. Multi-centric studies with homogenous patient population are required to establish the diagnostic performance of 68Ga-SA.FAPi for incorporation into routine clinical practice.
Not all nodal and metastatic lesions in the comparative analysis have confirmed metastasis through biopsy. Ethically, obtaining pathological confirmation for all analyzed lesions solely to validate the PET/CT results
CONCLUSION
68Ga-SA.FAPi consistently matched the standard-of-care FDG in detection of local disease and distant metastases in liver, bones, adrenals and peritoneum with discordant findings were noted in lung nodules and lymph nodes. Significantly higher 68Ga-SA.FAPi tracer avidity was noted in local disease and distant metastases with comparable TBR. These findings emphasize the selective expression of 68Ga-SA.FAPi in various cancers and add value to existing knowledge on FAP inhibitor molecular imaging.
Leadership Roles
All authors actively contributed in the study conception and design. The DOTA.SA.FAPi molecule was provided by Prof. Frank Roesch and Dr. Euy Sung Moon. The patients were referred by Prof. Ajay Duseja, Dr. Rama Walia, and Dr. Santhosh Irrinki. The study was performed by Ms. Sejal Chopra under the supervision of Dr. Jaya Shukla, Prof. Bhagwant Rai Mittal and Dr. Harmandeep Singh. The acquisition was performed by Dr. Nivedita Rana. The patient images were interpreted by Dr.Yamini Mathur and Dr.
Data Statement
The author(s) declare(s) that they had full access to all of the data in this study and the author(s) take(s) complete responsibility for the integrity of the data and the accuracy of the data analysis.
Funding
The authors would like to acknowledge Postgraduate Institute of Medical Education and Research, Chandigarh (Project ID:9719–126) for providing financial support to conduct the study.
Declaration of Competing Interest
Epub 2023 Nov 7.
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37932560
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10.1007/s00259-023-06482-z
Therapeutic potential of [177Lu]Lu-DOTAGA-FAPi dimers in metastatic breast cancer patients with limited treatment options: efficacy and safety assessment
Madhav P Yadav
Eur J Nucl Med Mol Imaging
Abstract
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Basic Science Investigation
, , , , , Melissa Miranda Lucero, Ana Rita Pombo Antunes, , Jo A. Van Ginderachter, and
Journal of Nuclear Medicine
Abstract
Fibroblast activation protein α (FAP) is overexpressed on cancer-associated fibroblasts in various carcinomas, contributing to tumor growth, metastasis, and immunosuppression (8). Breast, colon, and pancreatic tumors often show strong desmoplastic reactions, which result in a dominant presence of stromal cells. In particular cases, cancer cells express FAP as well, such as in sarcomas, melanomas, or glioblastomas. FAP targeting is gaining attention for molecular imaging and TRT. Quinoline-based FAP inhibitors (FAPIs) have shown potential in cancer imaging, but their prognostic value remains uncertain. Some FAPI molecules have been labeled with therapeutic radionuclides and evaluated in preclinical and clinical studies, although clinical evidence is limited and shows mixed responses to anti-FAP TRT. Challenges include small patient cohorts, heterogeneity, and optimizing FAPI tumor retention (9).
Here we describe the generation, selection, and characterization of a lead sdAb with excellent binding characteristics for FAP. We assessed its PET and SPECT imaging potential, as well as its use for TRT.
MATERIALS AND METHODS
The methodologies for sdAb generation (10,11), lead compound selection and biochemical characterization, cell culture conditions, radiochemical procedures, radioligand binding studies, and dosimetry calculations can be found in the supplemental materials (supplemental materials are available at http://jnm.snmjournals.org).
Preparation of Radiolabeled sdAbs
Animal Models
Female CRL:ν-FoxN1nu mice (Charles River) received subcutaneous neck injections of 2 × 106 U87-MG cells. Tumors were allowed to grow to 100–250 mm3 for biodistribution and therapy studies. We monitored animal welfare by measuring weights and tumor volumes, applying a humane endpoint of body weight loss of more than 20% or tumor volume of more than 1,500 mm3. Tumor dimensions were calculated using a digital caliper. Dose-escalation studies were performed on female C57BL/6 mice (Charles River). Ethical approval was granted by Vrije Universiteit Brussel’s ethical committee.
Biodistribution of Radiolabeled sdAbs
Toxicity Assessment of Therapeutic [131I]I-GMIB-4AH29 and [225Ac]Ac-DOTA-4AH29
Therapeutic Efficacy of [131I]I-GMIB-4AH29 and [225Ac]Ac-DOTA-4AH29
Statistical Analysis
Kaplan–Meier curves that show the time to reach humane endpoints were statistically analyzed using the log-rank (Mantel–Cox) test. Student t testing or 1-way ANOVA were performed for all other results.
RESULTS
Generation and In Vitro and In Vivo Screening of Anti-FAP sdAbs
Kinetic Binding Analysis of sdAbs to Biotinylated hFAP or mFAP Protein
Influence of Equimolar Concentration of SdAbs and Small-Molecule Inhibitors Talabostat and FAPI-4 on hFAP Enzymatic Activity
Conjugation and Radiolabeling of sdAbs
Cell Binding and Immunoreactivity
Imaging, Biodistribution, and Dosimetry
Toxicity Assessment
Therapeutic Efficacy
DISCUSSION
FAP is highly expressed on cancer-associated fibroblasts of carcinomas. Breast, colon, and pancreatic tumors often show strong desmoplastic reactions, which result in a dominant presence of stromal cells. FAP has low expression or is undetectable in most normal adult tissues (8). Various FAPIs have been used as tools to image FAP expression. Some have also been labeled with therapeutic radionuclides, and although significant efforts were made to optimize the tumor half-life of FAPI compounds, it seems that limited tumor retention still poses a challenge (9).
A few strategies to reduce the retention of cytotoxic radiation in the kidneys after peptide- or small-protein–based TRT have been explored. SdAbs are excreted via the kidneys’ glomerulus with moderate retention, making kidneys the dose-limiting organ of sdAb-mediated TRT. A pretargeting approach could circumvent the limitations imposed by kidneys for sdAb-mediated TRT, as was demonstrated successfully for a 177Lu-labeled Affibody molecule (Affibody AB) (24). Other possible avenues are modulation of the sdAb protein sequence, cleavable linkers, and coupling methods to avoid a high radiation burden on the kidneys (25).
DISCLOSURE
This work is supported by a subsidy from La Région de Bruxelles-Capitale–Innoviris to Precirix. Yana Dekempeneer, Sam Massa, Francis Santens, Laurent Navarro, Marion Berdal, Melissa Lucero, Ana Antunes, and Matthias D’Huyvetter are employees, and Nick Devoogdt and Tony Lahoutte are consultants, of Precirix NV; all hold ownership interest (including patents) in sdAb radiotherapeutics. No other potential conflict of interest relevant to this article was reported.
KEY POINTS
QUESTION: Is radiolabeled sdAb 4AH29 a relevant radiotheranostic tool for FAP-positive cancers?
IMPLICATIONS FOR PATIENT CARE: The results presented herein underline the radiotheranostic potential of radiolabeled sdAb 4AH29 for FAP-positive cancers, which warrants clinical testing. SdAbs might benefit patients with breast, colon, and pancreatic tumors, which often show a dominant presence of stromal cells.
ACKNOWLEDGMENTS
We thank Claudia Mebis, Marijse Hulsbosch, Jos Eersels, Lina Saadah, Labiba Mahmud, Jonatan Dewulf, and Aleksandra Kotwicka for technical assistance and Peter Covens for assistance with dosimetry.
Footnotes
- © 2023 by the Society of Nuclear Medicine and Molecular Imaging.
REFERENCES
- Received for publication July 17, 2023.
- September 27, 2023.
Fibroblast Activation Protein Targeting Probe with Gly-Pro Sequence for PET of Glioblastoma
Abstract
Keywords:
FAPI; PET imaging; fibroblast activation protein; glioblastoma.
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