FAP (fibroblast activation protein)

Of 15 synthesized FAPIs, FAPI-04 was identified as the most promising tracer for clinical application. Compared with the previously published ligand, FAPI-02, FAPI-04 showed excellent stability in human serum, higher affinity for FAP as opposed to CD26, and slower excretion in vitro. https://pubmed.ncbi.nlm.nih.gov/29626119/

In vivo, a higher SUV was reached in tumor-bearing animals, leading to larger areas under the curve as calculated from biodistribution experiments. Finally, PET/CT scans with 68Ga-FAPI-04 in 2 patients with metastasized breast cancer revealed high tracer uptake in metastases and a reduction in pain symptoms after therapy with a considerably low dose of 90Y-FAPI-04. Conclusion: FAPI-04 represents a promising tracer for both diagnostic imaging and, possibly, targeted therapy of malignant tumors with a high content of activated fibroblasts, such as breast cancer.https://pubmed.ncbi.nlm.nih.gov/29626119/

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Results: Similar to literature values for 18F-FDG, 68Ga-DOTATATE, and 68Ga-PSMA-11, an examination with 200 MBq of 68Ga-FAPI-2 or 68Ga-FAPI-4 corresponds to an equivalent dose of approximately 3-4 mSv. After a fast clearance via the kidneys, the normal organs showed a low tracer uptake with only minimal changes between 10 min and 3 h after injection. In 68Ga-FAPI-2, the tumor uptake from 1 to 3 h after injection decreased by 75%, whereas the tumor retention was prolonged with 68Ga-FAPI-4 (25% washout). Regarding tumor-to-background ratios, at 1 h after injection both 68Ga-FAPI tracers performed equally. In comparison to 18F-FDG, the tumor uptake was almost equal (average SUVmax, 7.41 for 18F-FDG and 7.37 for 68Ga-FAPI-2; not statistically significant); the background uptake in brain (11.01 vs. 0.32), liver (2.77 vs. 1.69), and oral/pharyngeal mucosa (4.88 vs. 2.57) was significantly lower with 68Ga-FAPI. Other organs did not relevantly differ between 18F-FDG and 68Ga-FAPI. Conclusion: FAPI PET/CT is a new diagnostic method in imaging cancer patients. In contrast to 18F-FDG, no diet or fasting in preparation for the examination is necessary, and image acquisition can potentially be started a few minutes after tracer application. Tumor-to-background contrast ratios were equal to or even better than those of 18F-FDG.[1]

FAPIs based on a quinoline structure were synthesized and characterized with respect to binding, internalization, and efflux in cells expressing human and murine FAP as well as CD26.https://pubmed.ncbi.nlm.nih.gov/29626119/

Preclinical pharmacokinetics were determined in tumor-bearing animals with biodistribution experiments and small-animal PET. Finally, a proof-of-concept approach toward imaging and therapy was chosen for 2 patients with metastasized breast cancer. https://pubmed.ncbi.nlm.nih.gov/29626119/

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Methods: A preliminary dosimetry estimate for 68Ga-FAPI-2 and 68Ga-FAPI-4 was based on 2 patients examined at 0.2, 1, and 3 h after tracer injection using the QDOSE dosimetry software suit. Further PET/CT scans of tumor patients were acquired 1 h after injection of either 68Ga-FAPI-2 (n = 25) or 68Ga-FAPI-4 (n = 25); for 6 patients an intraindividual related 18F-FDG scan (also acquired 1 h after injection) was available. For the normal tissue of 16 organs, a 2-cm spheric volume of interest was placed in the parenchyma; for tumor lesions, a threshold-segmented volume of interest was used to quantify SUVmean and SUVmax[1]

[1]. 68Ga-FAPI PET/CT: Biodistribution and Preliminary Dosimetry Estimate of 2 DOTA-Containing FAP-Targeting Agents in Patients with Various Cancers. J Nucl Med. 2019 Mar;60(3):386-392.

Several radiopharmaceuticals targeting fibroblast activation protein (FAP) based on the highly potent FAP inhibitor UAMC1110 are currently under investigation. Pre-clinical as well as clinical research exhibited the potential of these imaging agents. However, the monomeric small molecules seemed to have a short retention time in the tumor in combination with fast renal clearance. Therefore, our strategy was to develop homodimeric systems having two FAP inhibitors to improve residence time and tumor accumulation. The homodimers with two squaramide coupled FAP inhibitor conjugates DOTA.(SA.FAPi)2 and DOTAGA.(SA.FAPi)2 were synthesized and radiochemically evaluated with gallium-68. [68Ga]Ga-DOTAGA.(SA.FAPi)2 was tested for its in vitro stability, lipophilicity and affinity properties. In addition, human PET/CT scans were performed for [68Ga]Ga-DOTAGA.(SA.FAPi)2 with a head-to-head comparison with [68Ga]Ga-DOTA.SA.FAPi and [18F]FDG. Labeling with gallium-68 demonstrated high radiochemical yields. Inhibition measurements revealed excellent affinity and selectivity with low nanomolar IC50 values for FAP. In PET/CT human studies, significantly higher tumor uptake as well as longer tumor retention could be observed for [68Ga]Ga-DOTAGA.(SA.FAPi)2 compared to [68Ga]Ga-DOTA.SA.FAPi. Therefore, the introduction of the dimer led to an advance in human PET imaging indicated by increased tumor accumulation and prolonged retention times in vivo and thus, the use of dimeric structures could be the next step towards prolonged uptake of FAP inhibitors resulting in radiotherapeutic analogs of FAP inhibitors.[2]

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Fibroblast activation protein (FAP) is a type II membrane-bound glycoprotein which is overexpressed in cancer-associated fibroblasts and activated fibroblasts at wound healing/inflammatory sites. Since the first clinical application of quinoline-based FAP ligands in 2018, FAP inhibitor (FAPI)-based PET imaging and radiotherapy have been investigated for a wide variety of diseases, both cancerous and non-cancerous. As a consequence, promising strides have been made in particular to improve the understanding of FAPI-based PET imaging and the potential value of FAPI-based tumor radiotherapy. Herein, we present a comprehensive review of radiolabeled FAPI, including their clinical translation, in order to clarify the current and potential future role of this class of molecules in nuclear medicine. In particular, this review underlines the value of FAPI radiopharmaceuticals in the diagnosis or therapy of tumors or benign conditions. However, limitations in present studies have hampered a precise evaluation of FAPI radiopharmaceuticals. Despite this, it will likely be worthwhile to further explore the clinical value of FAPI in diagnosis and therapy through better-designed and larger-population clinical trials in the future.[3]

C42H57F3N10O12

950.96

Off-white to light yellow solid powder

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)