Purpose: Fibroblast activation protein (FAP) is a promising target for tumor treatment. In this study, we aimed to investigate the safety and efficacy of the albumin binder-conjugated FAP-targeted radiopharmaceutical, 177Lu-EB-FAPI (177Lu-LNC1004), in patients with metastatic radioiodine-refractory thyroid cancer (mRAIR-TC). Patients and Methods: This open-label, non-randomized, first-in-human, dose-escalation, investigator-initiated trial had a 3+3 design and involved a 6-week 177Lu-LNC1004 treatment cycle in patients with mRAIR-TC at 2.22 GBq initially, with subsequent cohorts receiving an incremental 50% dose increase until dose-limiting toxicity (DLT) was observed. Results: 177Lu-LNC1004 administration was well tolerated, with no life-threatening adverse events observed. No patients experienced DLT in Group A (2.22 GBq/cycle). One patient experienced grade 4 thrombocytopenia in Group B (3.33 GBq/cycle); hence, another three patients were enrolled, none of whom experienced DLT. Two patients experienced grade 3 and 4 hematotoxicity in Group C (4.99 GBq/cycle). The mean whole-body effective dose was 0.17 ± 0.04 mSv/MBq. Intense 177Lu-LNC1004 uptake and prolonged tumor retention resulted in high mean absorbed tumor doses (8.50 ± 12.36 Gy/GBq). The mean effective half-lives for the whole-body and tumor lesions were 90.20 ± 7.68 and 92.46 ± 9.66 hours, respectively. According to RECIST, partial response, stable disease, and progressive disease were observed in 3 (25%), 7 (58%), and 2 (17%) patients, respectively. The objective response and disease control rates were 25% and 83%, respectively. Conclusions: FAP-targeted radioligand therapy with 177Lu-LNC1004 at 3.33 GBq/cycle was well tolerated in patients with advanced mRAIR-TC, with high radiation dose delivery to the tumor lesions, encouraging therapeutic efficacy, and acceptable side effects.

To enhance tumor uptake and retention, we designed and developed bi-specific heterodimeric radiotracers targeting both FAP and αvβ3, [⁶⁸Ga]Ga-FAPI-RGD. The present study aimed to evaluate the specificity, pharmacokinetics, and dosimetry of [⁶⁸Ga]Ga-FAPI-RGD by preclinical and preliminary clinical studies.

Peptide receptor radionuclide therapy (PRRT) has over the last two decades emerged as a very promising approach to treat neuroendocrine tumors (NETs) with rapidly expanding clinical applications. By chelating a radiometal to a somatostatin receptor (SSTR) ligand, radiation can be delivered to cancer cells with high precision. Unlike conventional external beam radiotherapy, PRRT utilizes primarily β or α radiation derived from nuclear decay, which causes damage to cancer cells in the immediate proximity by irreversible direct or indirect ionization of the cells’ DNA, which induces apoptosis. In addition, to avoid damage to surrounding normal cells, PRRT privileges the use of radionuclides that have little penetrating and more energetic (and thus more ionizing) radiations. To date, the most frequently radioisotopes are β^– emitters, particularly Yttrium-90 (⁹⁰Y) and Lutetium-177 (¹⁷⁷Lu), labeled SSTR agonists. Current development of SSTR-targeting is triggering the shift from using SSTR agonists to antagonists for PRRT. Furthermore, targeted α-particle therapy (TAT), has attracted special attention for the treatment of tumors and offers an improved therapeutic option for patients resistant to conventional treatments or even beta-irradiation treatment. Due to its short range and high linear energy transfer (LET), α-particles significantly damage the targeted cancer cells while causing minimal cytotoxicity toward surrounding normal tissue. Actinium-225 (²²⁵Ac) has been developed into potent targeting drug constructs including somatostatin-receptor-based radiopharmaceuticals and is in early clinical use against multiple neuroendocrine tumor types. In this article, we give a review of preclinical and clinical applications of ²²⁵Ac-PRRT in NETs, discuss the strengths and challenges of ²²⁵Ac complexes being used in PRRT; and envision the prospect of ²²⁵Ac-PRRT as a future alternative in the treatment of NETs.

Purpose: Fibroblast activation protein (FAP) is highly expressed in cancer-associated fibroblasts and certain tumor cells, making it a promising therapeutic target for various malignancies. This study evaluated the efficacy and safety of 177Lu-Evans blue–FAP inhibitor (177Lu-LNC1004) radioligand therapy (RLT) for treating end-stage metastatic tumors. Patients and Methods: This single-arm, single-center, phase II trial included 28 patients with progressive metastatic malignancies (11 types) and high FAP expression (defined as a maximum standardized uptake value ≥10 in >50% of tumors) who had exhausted all approved therapies, screened between June 2022 and April 2024. Patients were scheduled to receive four 177Lu-LNC1004 RLT cycles at 3.33 GBq/cycle every 6 weeks. The primary endpoint was post-RLT radiologic response. The secondary endpoints were progression-free survival (PFS), overall survival (OS), dosimetry, and safety. Results: Eastern Cooperative Oncology Group scores >2 were observed in 68% of patients. Overall, 63 177Lu-LNC1004 RLT cycles were performed, with 19 (68%) patients undergoing ≥2 cycles. Disease control was achieved in 13 (13/28, 46%) patients, with 4 and 9 patients demonstrating partial response and stable disease, respectively, and associated with improved PFS and OS (P < 0.001). The mean absorbed dose in tumors was 4.69 ± 3.83 Gy/GBq (1.18–25.03 Gy/GBq). Treatment-related grade 3/4 hematotoxicity was observed in six (21%) patients, with thrombocytopenia, leukopenia, and neutropenia most prevalent. No grade 3/4 hepatotoxicity or nephrotoxicity was observed. Conclusions: FAP-directed RLT using 177Lu-LNC1004 at 3.33 GBq/cycle was well tolerated with an acceptable toxicity profile. Nearly half of patients achieved disease control, which was associated with prolonged PFS and OS.