Purpose
Fibroblast activation protein (FAP) is a membrane-bound protease that has limited expression in normal adult tissues but is highly expressed in the tumor microenvironment of many solid ...cancers. FAP-2286 is a FAP-binding peptide coupled to a radionuclide chelator that is currently being investigated in patients as an imaging and therapeutic agent. The potency, selectivity, and efficacy of FAP-2286 were evaluated in preclinical studies.
Methods
FAP expression analysis was performed by immunohistochemistry and autoradiography on primary human cancer specimens. FAP-2286 was assessed in biochemical and cellular assays and in
in vivo
imaging and efficacy studies, and was further evaluated against FAPI-46, a small molecule–based FAP-targeting agent.
Results
Immunohistochemistry confirmed elevated levels of FAP expression in multiple tumor types including pancreatic, breast, and sarcoma, which correlated with FAP binding by FAP-2286 autoradiography. FAP-2286 and its metal complexes demonstrated high affinity to FAP recombinant protein and cell surface FAP expressed on fibroblasts. Biodistribution studies in mice showed rapid and persistent uptake of
68
Ga-FAP-2286,
111
In-FAP-2286, and
177
Lu-FAP-2286 in FAP-positive tumors, with renal clearance and minimal uptake in normal tissues.
177
Lu-FAP-2286 exhibited antitumor activity in FAP-expressing HEK293 tumors and sarcoma patient-derived xenografts, with no significant weight loss. In addition, FAP-2286 maintained longer tumor retention and suppression in comparison to FAPI-46.
Conclusion
In preclinical models, radiolabeled FAP-2286 demonstrated high tumor uptake and retention, as well as potent efficacy in FAP-positive tumors. These results support clinical development of
68
Ga-FAP-2286 for imaging and
177
Lu-FAP-2286 for therapeutic use in a broad spectrum of FAP-positive tumors.
Fibroblast activation protein (FAP) is a promising target for diagnosis and therapy of numerous malignant tumors. FAP-2286 is the conjugate of a FAP-binding peptide, which can be labeled with ...radionuclides for theranostic applications. We present the first-in-humans results using 177Lu-FAP-2286 for peptide-targeted radionuclide therapy (PTRT). Methods: PTRT using 177Lu-FAP-2286 was performed on 11 patients with advanced adenocarcinomas of the pancreas, breast, rectum, or ovary after prior confirmation of uptake on 68Ga-FAP-2286 or 68Ga-FAPI-04 PET/CT. Results: Administration of 177Lu-FAP-2286 (5.8 ± 2.0 GBq; range, 2.4–9.9 GBq) was well tolerated, with no adverse symptoms or clinically detectable pharmacologic effects being noticed or reported in any of the patients. The whole-body effective dose was 0.07 ± 0.02 Gy/GBq (range, 0.04–0.1 Gy/GBq). The mean absorbed doses for kidneys and red marrow were 1.0 ± 0.6 Gy/GBq (range, 0.4–2.0 Gy/GBq) and 0.05 ± 0.02 Gy/GBq (range, 0.03–0.09 Gy/GBq), respectively. Significant uptake and long tumor retention of 177Lu-FAP-2286 resulted in high absorbed tumor doses, such as 3.0 ± 2.7 Gy/GBq (range, 0.5–10.6 Gy/GBq) in bone metastases. No grade 4 adverse events were observed. Grade 3 events occurred in 3 patients-1 with pancytopenia, 1 with leukocytopenia, and 1 with pain flare-up; 3 patients reported a pain response. Conclusion: 177Lu-FAP-2286 PTRT, applied in a broad spectrum of cancers, was relatively well tolerated, with acceptable side effects, and demonstrated long retention of the radiopeptide. Prospective clinical studies are warranted.
Hardly any new tracers attracted more attention in nuclear medicine in the last couple of years than radiolabeled fibroblast activation protein inhibitors (FAPi’s). Molecules targeting ...cancer-associated fibroblasts (CAFs) or disease-associated fibroblasts in benign disorders (DAFs) gave rise to a new class of radiopharmaceuticals widely applicable for imaging and with the desired use as therapeutic compounds. Despite displaying benefits in diagnostic sensitivity over FDG, most FAP-targeting compounds in today’s clinical routine continue to lack therapeutic utility due to short tumor retention. In this study, we evaluated 3BP-3940, specifically designed for achieving prolonged tumor retention and remarkably low uptake in healthy tissues. We herein present the automated manufacturing of gallium-68 (Ga-68) and lutetium-177 (Lu-177)-labeled 3BP-3940, their respective in vitro stability, validation of an automated production process, and validation of an analytical HPLC method for quality control. Finally, we give a first insight into the clinical utility of the two compounds.
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•Automated, validated processing of 3BP-3940•Development of HPLC validation for 68GaGa-3BP-3940•First in human investigation for 68GaGa-3BP-3940 and 177LuLu-3BP-3940•Long-time tumor retention of 177LuLu-3BP-3940
Nuclear medicine; Pharmaceutical quality control; Radiochemicals
Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that inhibits activated factor X (FXa) via a slow-tight binding mechanism and tissue factor-activated FVII (TF-FVIIa) via ...formation of a quaternary FXa-TFPI-TF-FVIIa complex. Inhibition of TFPI enhances coagulation in hemophilia models. Using a library approach, we selected and subsequently optimized peptides that bind TFPI and block its anticoagulant activity. One peptide (termed compound 3), bound with high affinity to the Kunitz-1 (K1) domain of TFPI (Kd ∼1 nM). We solved the crystal structure of this peptide in complex with the K1 of TFPI at 2.55-Å resolution. The structure of compound 3 can be segmented into a N-terminal anchor; an Ω-shaped loop; an intermediate segment; a tight glycine-loop; and a C-terminal α-helix that is anchored to K1 at its reactive center loop and two-stranded β-sheet. The contact surface has an overall hydrophobic character with some charged hot spots. In a model system, compound 3 blocked FXa inhibition by TFPI (EC50 = 11 nM) and inhibition of TF-FVIIa-catalyzed FX activation by TFPI (EC50 = 2 nM). The peptide prevented transition from the loose to the tight FXa-TFPI complex, but did not affect formation of the loose FXa-TFPI complex. The K1 domain of TFPI binds and inhibits FVIIa and the K2 domain similarly inhibits FXa. Because compound 3 binds to K1, our data show that K1 is not only important for FVIIa inhibition but also for FXa inhibition, i.e. for the transition of the loose to the tight FXa-TFPI complex. This mode of action translates into normalization of coagulation of hemophilia plasmas. Compound 3 thus bears potential to prevent bleeding in hemophilia patients.
The membrane protein carbonic anhydrase IX (CAIX) is highly expressed in many hypoxic or von Hippel-Lindau tumor suppressor-mutated tumor types. Its restricted expression in healthy tissues makes ...CAIX an attractive diagnostic and therapeutic target. DPI-4452 is a CAIX-targeting cyclic peptide with a DOTA cage, allowing radionuclide chelation for theranostic purposes. Here, we report CAIX expression in multiple tumor types and provide in vitro and in vivo evaluations of
Ga-labeled DPI-4452 (
GaGa-DPI-4452) and
Lu-labeled DPI-4452 (
LuLu-DPI-4452).
CAIX expression was assessed by immunohistochemistry with a panel of tumor and healthy tissues. The molecular interactions of complexed and uncomplexed DPI-4452 with CAIX were assessed by surface plasmon resonance and cell-binding assays. In vivo characterization of radiolabeled and nonradiolabeled DPI-4452 was performed in HT-29 colorectal cancer (CRC) and SK-RC-52 clear cell renal cell carcinoma (ccRCC) human xenograft mouse models and in healthy beagle dogs.
Overexpression of CAIX was shown in several tumor types, including ccRCC, CRC, and pancreatic ductal adenocarcinoma. DPI-4452 specifically and selectively bound CAIX with subnanomolar affinity. In cell-binding assays, DPI-4452 displayed comparably high affinities for human and canine CAIX but a much lower affinity for murine CAIX, demonstrating that the dog is a relevant species for biodistribution studies. DPI-4452 was rapidly eliminated from the systemic circulation of beagle dogs. The highest uptake of
GaGa-DPI-4452 and
LuLu-DPI-4452 was observed in the small intestine and stomach, 2 organs known to express CAIX. Uptake in other organs (e.g., kidneys) was remarkably low. In HT-29 and SK-RC-52 xenograft mouse models, both
GaGa-DPI-4452 and
LuLu-DPI-4452 showed tumor-selective uptake; in addition,
LuLu-DPI-4452 significantly reduced tumor growth. These results demonstrated the theranostic potential of DPI-4452.
DPI-4452 selectively targets CAIX.
GaGa-DPI-4452 and
LuLu-DPI-4452 localized to tumors and were well tolerated in mice.
LuLu-DPI-4452 demonstrated strong tumor growth inhibition in 2 xenograft mouse models. Thus, the 2 agents potentially provide a theranostic approach for selecting and treating patients with CAIX-expressing tumors such as ccRCC, CRC, and pancreatic ductal adenocarcinoma.
The membrane protein carbonic anhydrase IX (CAIX) is highly expressed in many hypoxic or von Hippel-Lindau tumor suppressor–mutated tumor types. Its restricted expression in healthy tissues makes ...CAIX an attractive diagnostic and therapeutic target. DPI-4452 is a CAIX-targeting cyclic peptide with a DOTA cage, allowing radionuclide chelation for theranostic purposes. Here, we report CAIX expression in multiple tumor types and provide in vitro and in vivo evaluations of 68Ga-labeled DPI-4452 (68GaGa-DPI-4452) and 177Lu-labeled DPI-4452 (177LuLu-DPI-4452). Methods: CAIX expression was assessed by immunohistochemistry with a panel of tumor and healthy tissues. The molecular interactions of complexed and uncomplexed DPI-4452 with CAIX were assessed by surface plasmon resonance and cell-binding assays. In vivo characterization of radiolabeled and nonradiolabeled DPI-4452 was performed in HT-29 colorectal cancer (CRC) and SK-RC-52 clear cell renal cell carcinoma (ccRCC) human xenograft mouse models and in healthy beagle dogs. Results: Overexpression of CAIX was shown in several tumor types, including ccRCC, CRC, and pancreatic ductal adenocarcinoma. DPI-4452 specifically and selectively bound CAIX with subnanomolar affinity. In cell-binding assays, DPI-4452 displayed comparably high affinities for human and canine CAIX but a much lower affinity for murine CAIX, demonstrating that the dog is a relevant species for biodistribution studies. DPI-4452 was rapidly eliminated from the systemic circulation of beagle dogs. The highest uptake of 68GaGa-DPI-4452 and 177LuLu-DPI-4452 was observed in the small intestine and stomach, 2 organs known to express CAIX. Uptake in other organs (e.g., kidneys) was remarkably low. In HT-29 and SK-RC-52 xenograft mouse models, both 68GaGa-DPI-4452 and 177LuLu-DPI-4452 showed tumor-selective uptake; in addition, 177LuLu-DPI-4452 significantly reduced tumor growth. These results demonstrated the theranostic potential of DPI-4452. Conclusion: DPI-4452 selectively targets CAIX. 68GaGa-DPI-4452 and 177LuLu-DPI-4452 localized to tumors and were well tolerated in mice. 177LuLu-DPI-4452 demonstrated strong tumor growth inhibition in 2 xenograft mouse models. Thus, the 2 agents potentially provide a theranostic approach for selecting and treating patients with CAIX-expressing tumors such as ccRCC, CRC, and pancreatic ductal adenocarcinoma.
Purpose
FAP is a membrane-bound protease under investigation as a pan-cancer target, given its high levels in tumors but limited expression in normal tissues. FAP-2286 is a radiopharmaceutical in ...clinical development for solid tumors that consists of two functional elements: a FAP-targeting peptide and a chelator used to attach radioisotopes. Preclinically, we evaluated the immune modulation and anti-tumor efficacy of FAP-2287, a murine surrogate for FAP-2286, conjugated to the radionuclide lutetium-177 (
177
Lu) as a monotherapy and in combination with a PD-1 targeting antibody.
Methods
C57BL/6 mice bearing MCA205 mouse FAP-expressing tumors (MCA205-mFAP) were treated with
177
Lu-FAP-2287, anti-PD-1, or both. Tumor uptake of
177
Lu- FAP-2287 was assessed by SPECT/CT scanning, while therapeutic efficacy was measured by tumor volume and survival. Immune profiling of tumor infiltrates was evaluated through flow cytometry, RNA expression, and immunohistochemistry analyses.
Results
177
Lu-FAP-2287 rapidly accumulated in MCA205-mFAP tumors leading to significant tumor growth inhibition (TGI) and longer survival time. Significant TGI was also observed from anti-PD-1 and the combination. In flow cytometry analysis of tumors,
177
Lu-FAP-2287 increased CD8
+
T cell infiltration which was maintained in the combination with anti-PD-1. The increase in CD8
+
T cells was accompanied by an induction of STING-mediated type I interferon response and higher levels of co-stimulatory molecules such as CD86.
Conclusion
In a preclinical model, FAP-targeted radiotherapy enhanced anti-PD-1-mediated TGI by modulating the TME and increasing the recruitment of tumor-infiltrating CD8
+
T cells. These findings provide a rationale for clinical studies of combined
177
Lu-FAP-2286 radiotherapy and immune checkpoint inhibition in FAP-positive tumors.
Abstract
Background: FAP is a membrane-bound protease with limited expression in normal tissues but high expression on cancer-associated fibroblasts abundant in the stroma of most tumors. FAP-2286 is ...a potent and selective FAP-targeted peptide linked to the chelator DOTA that allows for attachment of radionuclides for therapeutic and imaging applications. Assessing patterns of FAP expression in different tumor types and correlating expression with FAP-2286 uptake can help guide tumor selection for FAP-2286 therapy. Methods: FAP immunohistochemistry (IHC) was performed on FFPE tissue specimens from 16 tumor types using the SP325 antibody. Overall and tumor/stroma-specific H-scores were calculated using Visiopharm and HALO analysis, respectively. Autoradiography with 111In-FAP-2286 was performed on a subset of matched frozen tissue sections. Results: Gene expression analysis across The Cancer Genome Atlas data set revealed elevated FAP mRNA expression in multiple tumor types. A pan-tumor IHC screen confirmed that ≥30% of samples in various indications (eg, sarcoma, pancreatic adenocarcinoma, mesothelioma, head and neck squamous cell carcinoma) had high FAP expression (H-score ≥30). While in most tumor types FAP was predominantly localized to the stroma, FAP expression was also observed in tumor cells, especially in tumors of mesenchymal origin, eg, sarcoma and mesothelioma. High FAP expression was independent of tumor stage or grade and detected in both primary and metastatic samples. Multiple sarcoma and mesothelioma subtypes demonstrated high FAP H-scores, suggesting that FAP expression is not limited to a specific subtype. There was significant correlation between FAP expression observed by IHC and FAP-2286 binding as assessed by autoradiography in matched frozen tissues (Pearson r=0.73; p<0.01). Conclusions: Our IHC screen identified high FAP expression in various tumor types that correlated with in vitro FAP-2286 binding, suggesting that FAP is an attractive target across a broad range of tumor types for peptide-targeted radionuclide therapy. Accordingly, the phase 1/2 LuMIERE clinical trial (NCT04939610) will evaluate FAP-2286 as a therapeutic (177Lu-FAP-2286) and imaging (68Ga-FAP-2286) agent in multiple indications.
Citation Format: Tanya T. Kwan, Minh Nguyen, Dirk Zboralski, Anne Schumann, Anne Bredenbeck, Matthias Paschke, Christian Haase, Aileen Hoehne, Ulrich Reineke, Christiane Smerling, Frank Osterkamp, Jim Xiao, Andrew D. Simmons, Thomas C. Harding, Kevin L. Lin. Pan-cancer analysis of fibroblast activation protein alpha (FAP) expression to guide tumor selection for the peptide-targeted radionuclide therapy FAP-2286 abstract. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr LBA032.
Neurotensin receptor 1 (NTR1) is overexpressed in ductal pancreatic adenocarcinoma, which is still one of the deadliest cancers, with a very poor prognosis. Eligible patients were offered salvage ...radiopharmaceutical therapy with the novel NTR1 antagonist 177Lu-3BP-227. Methods: Six patients with confirmed ductal pancreatic adenocarcinoma who had exhausted all other treatment options received 177Lu-3BP-227 for evaluation of NTR1 expression in vivo. Three patients received treatment activities of 5.1–7.5 GBq. Results: Administration of 177Lu-3BP-227 was well tolerated by all patients. The kidneys were identified as the dose-limiting organ. The most severe adverse event was reversible grade 2 anemia. One patient achieved a partial response and experienced significant improvement of symptoms and quality of life. This patient survived 13 mo from diagnosis and 11 mo from the start of 177Lu-3BP-227 therapy. Conclusion: This initial report provides clinical evidence of the feasibility of treatment of ductal pancreatic adenocarcinoma using 177Lu-3BP-227.
Neurotensin receptor 1 (NTR1) is overexpressed in ductal pancreatic adenocarcinoma, which is still one of the deadliest cancers, with a very poor prognosis. Eligible patients were offered salvage ...radiopharmaceutical therapy with the novel NTR1 antagonist 177Lu-3BP-227. Methods: Six patients with confirmed ductal pancreatic adenocarcinoma who had exhausted all other treatment options received 177Lu-3BP-227 for evaluation of NTR1 expression in vivo. Three patients received treatment activities of 5.1-7.5 GBq. Results: Administration of 177Lu-3BP-227 was well tolerated by all patients. The kidneys were identified as the dose-limiting organ. The most severe adverse event was reversible grade 2 anemia. One patient achieved a partial response and experienced significant improvement of symptoms and quality of life. This patient survived 13 mo from diagnosis and 11 mo from the start of 177Lu-3BP-227 therapy. Conclusion: This initial report provides clinical evidence of the feasibility of treatment of ductal pancreatic adenocarcinoma using 177Lu-3BP-227.
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