Floretyrosine F 18

CAS 178433-03-9

FormulaC₁₁H₁₄[¹⁸F]NO₃

Molecular Weight226.23 g/mol

FDA UNII1326R5J1IA

FDA 2026, APPROVALS 2026, Pixclara, TELIX PHARMACEUTICALS, GLIOMA, CANCER, TLX101-CDx, TLX101-Px, 1326R5J1IA, L-(18F)FET, O-(2-((18)F)fluoroethyl)-L-tyrosine

(2S)-2-amino-3-[4-(2-[¹⁸F]fluoroethoxy)phenyl]propanoic acid, (2S)-2-amino-3-[4-(2-(¹⁸F)fluoroethoxy)phenyl]propanoic acid

To use with positron emission tomography to differentiate recurrent or progressive glioma from treatment-related change in conjunction with other diagnostic evaluations

Floretyrosine F 18 (brand name Pixclara®, also known as 18F-FET) is a newly FDA-approved radiopharmaceutical imaging drug used in positron emission tomography (PET) scans for patients with glioma (brain cancer). Developed by Telix Pharmaceuticals, it received formal U.S. Food and Drug Administration (FDA) approval on September 14, 2026, making it the first and only approved FET-PET diagnostic tracer for brain tumors in the United States.

Primary Clinical Indication

Pixclara is indicated for use in both adult and pediatric patients (1 month of age and older).

Its primary clinical purpose is to differentiate recurrent or progressive glioma from treatment-related changes (such as radiation necrosis or inflammation). Following chemotherapy or radiation, traditional MRI scans often show areas that “light up,” making it incredibly difficult for neuro-oncologists to tell whether a tumor is growing back or if the brain is simply healing from harsh treatments. Pixclara solves this diagnostic dilemma by providing metabolic clarity.

How It Works (Mechanism of Action)

• Targeted Delivery: Floretyrosine F 18 is a synthetic amino acid analogue labeled with the radioactive isotope fluorine-18. [1, 2]
• Cellular Uptake: Once injected intravenously, it specifically targets and binds to L-type amino acid transporters 1 and 2 (LAT1 and LAT2). These transporters are heavily overexpressed on the membranes of active glioma cells compared to healthy brain tissue.
• PET Detection: The tumor cells rapidly absorb the tracer, and the energy emissions from the fluorine-18 isotope are captured by a PET scanner, creating a highly accurate metabolic map of the tumor.

Strategic & Future Impact

The approval aligns U.S. practice with international clinical guidelines—such as the National Comprehensive Cancer Network (NCCN) Guidelines®—which already recommend FET-PET imaging for brain tumor management. Furthermore, Telix Pharmaceuticals is currently conducting a Phase 3 registrational study to expand Pixclara’s indication to include the diagnosis and characterization of brain metastases (cancers that have spread to the brain from other parts of the body)

Fluoroethyl-l-tyrosine (¹⁸F), commonly known as [¹⁸F]FET, is a radiopharmaceutical tracer used in positron emission tomography (PET) imaging. This synthetic amino acid, labeled with the radioactive isotope fluorine-18, is a valuable radiopharmaceutical tracer for use in neuro-oncology for diagnosing, planning treatment, and following up on brain tumors such as gliomas. The tracer’s ability to provide detailed metabolic imaging of tumors makes it an essential tool in the clinical management of brain cancer patients. Continued advancements in PET imaging technology and the development of more efficient synthesis methods are expected to further enhance the clinical utility of [¹⁸F]FET.^[2]

Radiosynthesis

There are two common pathways for the radiosynthesis of [¹⁸F]FET. The first one utilizes a nucleophilic ¹⁸F-fluorination of ethyleneglycol-1,2-ditosylate with a subsequent ¹⁸F-fluoroethylation of a precursor di-sodium salt of L-tyrosine. This sequence requires two purification steps, two different precursors and a dual-reactor synthesis module which is not widely available in research or commercial centers.^[3][4][5] The schematic for this pathway is:^[6]

The second route of radiosynthesis is a direct nucleophilic ¹⁸F-fluorination a TET (O-(2-tosyloxy-ethyl)-N-trityl-L-tyrosine tert-butyl ester) protected precursor followed by acidic hydrolysis of protecting groups.^[3][4][7] The schematic for this pathway is:^[6]

REF

• Fluorinated phenylalanines: synthesis and pharmaceutical applicationsPublication Name:Beilstein Journal of Organic ChemistryPublication Date:2020-05-15PMCID:PMC7237815PMID:32509033DOI:10.3762/bjoc.16.91
• Solid-Phase Synthesis of O-(2-[18F]-Fluoro-ethyl)-l-tyrosinePublication Name:SynfactsPublication Date:2013-03-15DOI:10.1055/s-0032-1318420
• Investigations into the synthesis, radiofluorination and conjugation of a new [18F]fluorocyclobutyl prosthetic group and its in vitro stability using a tyrosine model systemPublication Name:Bioorganic & Medicinal ChemistryPublication Date:2013-02-01PMID:23290251DOI:10.1016/j.bmc.2012.11.049
• Microfluidic technology: An economical and versatile approach for the synthesis of O-(2-[18F]fluoroethyl)-l-tyrosine ([18F]FET)Publication Name:Bioorganic & Medicinal Chemistry LettersPublication Date:2012-03-15PMID:22342141DOI:10.1016/j.bmcl.2012.01.083
• Synthesis and biological evaluation of novel F-18 labeled pyrazolo[1,5-a]pyrimidine derivatives: Potential PET imaging agents for tumor detectionPublication Name:Bioorganic & Medicinal Chemistry LettersPublication Date:2011-08-15PMID:21752641DOI:10.1016/j.bmcl.2011.06.072
• (18)F Labeled benzimidazole derivatives as potential radiotracer for positron emission tomography (PET) tumor imagingPublication Name:Bioorganic & Medicinal ChemistryPublication Date:2010-04-01PMID:20303769DOI:10.1016/j.bmc.2010.02.060
• No carrier added synthesis of O-(2′-[18F]fluoroethyl)-l-tyrosine via a novel type of chiral enantiomerically pure precursor, NiII complex of a (S)-tyrosine Schiff basePublication Name:Bioorganic & Medicinal ChemistryPublication Date:2008-05-01PMID:18378460DOI:10.1016/j.bmc.2008.03.040
• Solid-Phase Synthesis of O-(2-[18F]-Fluoro-ethyl)-l-tyrosine, DOI:10.1055/s-0032-1318420, Publication Date:2013, Publication Name:Synfacts

SYN

US20190223814/US249082034

https://patentscope.wipo.int/search/en/detail.jsf;jsessionid=7C55DB9EE5B2E59D667F3571B796AE12.wapp1nB?docId=US249082034&_cid=P11-MU3HKD-32540-1

PAT

 US20120189546

https://patentscope.wipo.int/search/en/detail.jsf?docId=US73636763&_cid=P11-MU3HO5-37901-1

PAT

US20140235861

https://patentscope.wipo.int/search/en/detail.jsf?docId=US107206441&_cid=P11-MU3HO5-37901-1

Another example of an ¹⁸F-fluoroalkylation reaction to obtain a PET tracer is the reaction described by Wang et al (2006 J Radioanalyt Nuc Chem; 270(2): 439-43) used to obtain the ¹⁸F-labeled amino acid O-(2-[ ¹⁸F]fluoroethyl)-L-tyrosine ([ ¹⁸F]FET):

  [ ¹⁸F]Fluoroethyl tosylate was prepared in step (i) by displacement of a tosyl group from 1,2-bistosyloxyethane by reaction with K ¹⁸F/Kryptofix 2.2.2 in acetonitrile at 90° C. for 10 minutes. The purified [ ¹⁸F]fluoroethyl tosylate was then reacted in step (ii) with a solution of L-tyrosine and 10% aqueous NaOH in DMSO (or di-Na-salt of L-tyrosine in DMSO) 20 minutes at 90° C. to obtain [ ¹⁸F]FET. In contrast to the method for preparation of ¹⁸F-labelled S-fluoroalkyl diarylguanidines as reported by Robins et al (supra), this method for preparation of [ ¹⁸F]FET uses a soluble base in the alkylation reaction. However, the reaction is still not ideal for carrying out on an automated synthesis device that uses a cassette due to the fact that and additional vial is required for the base used for the subsequent fluoroalkylation step.

PAT

Radiation radiation detector with position tracking system and its use in medical systems and proceduresPublication Number:

JP-2004512502-APriority Date:2000-08-21

• Novel imaging agents and precursors and methods of preparation thereofPublication Number:CN-1234680-CPriority Date:2001-06-04Grant Date:2006-01-04
• Radioactive emission detector equipped with a position tracking system and utilization thereof with medical systems and in medical proceduresPublication Number:US-2005055174-A1Priority Date:2000-08-21
• Radioactive emission detector equipped with a position tracking system and utilization thereof with medical systems and in medical proceduresPublication Number:US-7826889-B2Priority Date:2000-08-21Grant Date:2010-11-02
• Radioactive emission detector equipped with a position tracking system and utilization thereof with medical systems and in medical proceduresPublication Number:US-2004015075-A1Priority Date:2000-08-21
• Radioactive emission detector equipped with a position tracking systemPublication Number:US-2014249402-A1Priority Date:2000-08-21
• Tumor imaging compoundsPublication Number:CA-2479514-CPriority Date:2002-04-30Grant Date:2011-07-26
• Protected tyrosine derivatives, method for the production thereof and use of the same for producing o-(2-[18f]-fluoroethyl)-l-tyrosinePublication Number:WO-02102765-A3Priority Date:2001-06-05
• Protected tyrosine derivatives, method for the production thereof and use of the same for producing o-(2-[18f]-fluoroethyl)-l-tyrosinePublication Number:US-2004192954-A1Priority Date:2001-06-05
• PROTECTED TYROSINE DERIVATIVES, METHOD FOR THE PRODUCTION THEREOF AND THEIR USE FOR THE PRODUCTION OF O-(2-?18 F)-FLUORETHYL)-L-TYROSINEPublication Number:AT-E289992-T1Priority Date:2001-06-05Grant Date:2005-03-15
• Imaging agents, precursors thereof and methods of manufacturePublication Number:US-2003124059-A1Priority Date:2001-06-04
• Radioactively labelled amino acid analogues, their preparation and usePublication Number:US-2006127306-A1Priority Date:2002-08-02
• Radioactively labelled amino acid analogues, their preparation and usePublication Number:EP-1539250-A1Priority Date:2002-08-02
• Tumor imaging compoundsPublication Number:US-7989649-B2Priority Date:2002-04-30Grant Date:2011-08-02
• Tumor imaging compoundsPublication Number:US-2009240041-A1Priority Date:2002-04-30
• Tumor imaging compoundsPublication Number:US-7544715-B2Priority Date:2002-04-30Grant Date:2009-06-09

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References

1.  CID 54255856 from PubChem
2.  Treglia G, Muoio B, Giovanella L (2020). “¹⁸F-FET”. In Calabria F, Schillaci O (eds.). Radiopharmaceuticals: A Guide to PET/CT and PET/MRI. Cham: Springer International Publishing. pp. 83–88. doi:10.1007/978-3-030-27779-6_4. ISBN 978-3-030-27778-9.
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6.  Wang M, Glick-Wilson BE, Zheng QH (December 2019). “Facile fully automated radiosynthesis and quality control of O-(2-[¹⁸F]fluoroethyl)-l-tyrosine ([¹⁸F]FET) for human brain tumor imaging”. Applied Radiation and Isotopes. 154 108852. Bibcode:2019AppRI.15408852W. doi:10.1016/j.apradiso.2019.108852. PMID 31442794.
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Clinical data
Other names	18F-FET; O-(2-(18F)fluoroethyl)-l-tyrosine, O-(2-Fluorethyl)-l-thyrosine, l-(18F)FET[1]
Routes of administration	Intravenous
ATC code	V09IX10 (WHO)
Identifiers
IUPAC name
CAS Number	178433-03-9
PubChem CID	9834479
ChemSpider	8010200
UNII	1326R5J1IA
CompTox Dashboard (EPA)	DTXSID601045942
Chemical and physical data
Formula	C11H14FNO3
Molar mass	227.235 g·mol−1
3D model (JSmol)	Interactive image
SMILES
InChI

///////////floretyrosine F 18, anax labs, FDA 2026, APPROVALS 2026, Pixclara, TELIX PHARMACEUTICALS, GLIOMA, CANCER, TLX101-CDx, TLX101-Px, 1326R5J1IA, L-(18F)FET, O-(2-((18)F)fluoroethyl)-L-tyrosine

#floretyrosine F 18, #anax labs, #FDA 2026, #APPROVALS 2026, #Pixclara, #TELIX PHARMACEUTICALS, #GLIOMA, #CANCER, #TLX101-CDx, #TLX101-Px, #1326R5J1IA, #L-(18F)FET, #O-(2-((18)F)fluoroethyl)-L-tyrosine