Pu Zhang1, Mengxin Xu1, Jie Ding2, Junyi Chen1, Taiping Zhang3, Li Huo4, Zhibo Liu5,6. 1. Radiochemistry and Radiation Chemistry Key Laboratory of Fundamental Science, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, 100871, Beijing, China. 2. Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing, 100730, China. 3. Department of General Surgery, Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing, 100730, China. 4. Department of Nuclear Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Science & Peking Union Medical College, Beijing, 100730, China. huoli@pumch.cn. 5. Radiochemistry and Radiation Chemistry Key Laboratory of Fundamental Science, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, 100871, Beijing, China. zbliu@pku.edu.cn. 6. Peking University-Tsinghua University Center for Life Sciences, Beijing, 100871, China. zbliu@pku.edu.cn.
Abstract
INTRODUCTION: Radiopharmaceuticals that target cancer-associated fibroblasts (CAFs) have become an increasingly attractive strategy for cancer theranostics. Recently, a series of fibroblast activation protein inhibitor (FAPI)-based radiopharmaceuticals have been successfully applied to the diagnosis of a variety of cancers and exhibited excellent tumor selectivity. Nevertheless, CAF-targeted radionuclide therapy encounters difficulties in cancer treatment, as the tumor uptake and retention of FAPIs are insufficient. To meet this challenge, we tried to conjugate albumin-binding moiety to FAPI molecule for prolonged circulation that may increase the accumulation and retention of radiopharmaceuticals in tumor. METHODS: Two fatty acids, lauric acid (C12) and palmitic acid (C16), were conjugated to FAPI-04 to give two albumin-binding FAPI radiopharmaceuticals, denoted as FAPI-C12 and FAPI-C16, respectively. They had been radiolabeled with gallium-68, yttrium-86, and lutecium-177 for stability study, binding affinity assay, PET and SPECT imaging, biodistribution, and radionuclide therapy study to systematically evaluate their potential for CAF-targeted radionuclide therapy. RESULTS: FAPI-C12 and FAPI-C16 showed high binding affinity to FAP with the IC50 of 6.80 ± 0.58 nM and 5.06 ± 0.69 nM, respectively. They were stable in both saline and plasma. The tumor uptake of [68Ga]Ga-FAPI-04 decreased by 56.9% until 30 h after treated with FAPI-C16 before, and the uptakes of [86Y]Y-FAPI-C12 and [86Y]Y-FAPI-C16 in HT-1080-FAP tumor were both much higher than that of HT-1080-Vehicle tumor which identified the high FAP specific of these two radiopharmaceuticals. Both FAPI-C12 and FAPI-C16 showed notably longer circulation and significantly enhanced tumor uptake than those of FAPI-04. [177Lu]Lu-FAPI-C16 had the higher tumor uptake at both 24 h (11.22 ± 1.18%IA/g) and 72 h (6.50 ± 1.19%IA/g) than that of [177Lu]Lu-FAPI-C12 (24 h, 7.54 ± 0.97%IA/g; 72 h, 2.62 ± 0.65%IA/g); both of them were much higher than [177Lu]Lu-FAPI-04 with the value of 1.24 ± 0.54%IA/g at 24 h after injection. Significant tumor volume inhibition of [177Lu]Lu-FAPI-C16 at the high activity of 29.6 MBq was observed, and the median survival was 28 days which was much longer than that of the [177Lu]Lu-FAPI-04 treated group of which the median survival was only 10 days. CONCLUSION: This proof-of-concept study validates the hypothesis that conjugation of albumin binders may shift the pharmacokinetics and enhance the tumor uptake of FAPI-based radiopharmaceuticals. This could be a general strategy to transform the diagnostic FAP-targeted radiopharmaceuticals into their therapeutic pairs.
INTRODUCTION: Radiopharmaceuticals that target cancer-associated fibroblasts (CAFs) have become an increasingly attractive strategy for cancer theranostics. Recently, a series of fibroblast activation protein inhibitor (FAPI)-based radiopharmaceuticals have been successfully applied to the diagnosis of a variety of cancers and exhibited excellent tumor selectivity. Nevertheless, CAF-targeted radionuclide therapy encounters difficulties in cancer treatment, as the tumor uptake and retention of FAPIs are insufficient. To meet this challenge, we tried to conjugate albumin-binding moiety to FAPI molecule for prolonged circulation that may increase the accumulation and retention of radiopharmaceuticals in tumor. METHODS: Two fatty acids, lauric acid (C12) and palmitic acid (C16), were conjugated to FAPI-04 to give two albumin-binding FAPI radiopharmaceuticals, denoted as FAPI-C12 and FAPI-C16, respectively. They had been radiolabeled with gallium-68, yttrium-86, and lutecium-177 for stability study, binding affinity assay, PET and SPECT imaging, biodistribution, and radionuclide therapy study to systematically evaluate their potential for CAF-targeted radionuclide therapy. RESULTS: FAPI-C12 and FAPI-C16 showed high binding affinity to FAP with the IC50 of 6.80 ± 0.58 nM and 5.06 ± 0.69 nM, respectively. They were stable in both saline and plasma. The tumor uptake of [68Ga]Ga-FAPI-04 decreased by 56.9% until 30 h after treated with FAPI-C16 before, and the uptakes of [86Y]Y-FAPI-C12 and [86Y]Y-FAPI-C16 in HT-1080-FAP tumor were both much higher than that of HT-1080-Vehicle tumor which identified the high FAP specific of these two radiopharmaceuticals. Both FAPI-C12 and FAPI-C16 showed notably longer circulation and significantly enhanced tumor uptake than those of FAPI-04. [177Lu]Lu-FAPI-C16 had the higher tumor uptake at both 24 h (11.22 ± 1.18%IA/g) and 72 h (6.50 ± 1.19%IA/g) than that of [177Lu]Lu-FAPI-C12 (24 h, 7.54 ± 0.97%IA/g; 72 h, 2.62 ± 0.65%IA/g); both of them were much higher than [177Lu]Lu-FAPI-04 with the value of 1.24 ± 0.54%IA/g at 24 h after injection. Significant tumor volume inhibition of [177Lu]Lu-FAPI-C16 at the high activity of 29.6 MBq was observed, and the median survival was 28 days which was much longer than that of the [177Lu]Lu-FAPI-04 treated group of which the median survival was only 10 days. CONCLUSION: This proof-of-concept study validates the hypothesis that conjugation of albumin binders may shift the pharmacokinetics and enhance the tumor uptake of FAPI-based radiopharmaceuticals. This could be a general strategy to transform the diagnostic FAP-targeted radiopharmaceuticals into their therapeutic pairs.
Authors: Thomas Lindner; Anastasia Loktev; Annette Altmann; Frederik Giesel; Clemens Kratochwil; Jürgen Debus; Dirk Jäger; Walter Mier; Uwe Haberkorn Journal: J Nucl Med Date: 2018-04-06 Impact factor: 10.057
Authors: Anastasia Loktev; Thomas Lindner; Walter Mier; Jürgen Debus; Annette Altmann; Dirk Jäger; Frederik Giesel; Clemens Kratochwil; Philippe Barthe; Christian Roumestand; Uwe Haberkorn Journal: J Nucl Med Date: 2018-04-06 Impact factor: 10.057
Authors: Sofia Koustoulidou; Mark W H Hoorens; Simone U Dalm; Shweta Mahajan; Reno Debets; Yann Seimbille; Marion de Jong Journal: Cancers (Basel) Date: 2021-03-04 Impact factor: 6.639
Authors: Kornelis S M van der Geest; Maria Sandovici; Pieter H Nienhuis; Riemer H J A Slart; Peter Heeringa; Elisabeth Brouwer; William F Jiemy Journal: Front Med (Lausanne) Date: 2022-06-06