9HD5 | pdb_00009hd5

Crystal structure of CD73 (ecto-5'-nucleotidase) in complex with the AOPCP derivative PSB19427 in the closed state

• PDB DOI: https://doi.org/10.2210/pdb9HD5/pdb

• Classification: HYDROLASE
• Organism(s): Homo sapiens
• Expression System: Homo sapiens
• Mutation(s): No 


• Deposited: 2024-11-11 Released: 2025-11-19 
• Deposition Author(s): Strater, N., Moschuetz, S., Dobelmann, C., Schmies, C.C., Jacobson, K.A., Muller, C.E., Junker, A.
• Funding Organization(s): German Research Foundation (DFG)

---

Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.91 Å
• R-Value Free: 
  0.273 (Depositor), 0.276 (DCC) 
• R-Value Work: 
  0.190 (Depositor), 0.208 (DCC) 
• R-Value Observed: 
  0.194 (Depositor) 

Starting Model: experimental

Literature

Fluorine-18-Labeled Nucleotide Analogs Targeting Ecto-5'-Nucleotidase (CD73) for Positron Emission Tomography Imaging of Solid Tumors.

Dobelmann, C., Schmies, C.C., Rolshoven, G.W., Scortichini, M., Wagner, S., Isaak, A., Idris, R.M., Dabel, J., Grey, L., Losenkova, K., Moschutz, S., Hroub, H.A., Keim, A., Hoppner, S., Sandholm, J., Bostrom, P., Hollmen, M., Strater, N., Hermann, S., Yegutkin, G.G., Jacobson, K.A., Schelhaas, S., Muller, C.E., Junker, A.

(2026) Angew Chem Int Ed Engl 65: e22758-e22758

• PubMed: 41834421 
• DOI: https://doi.org/10.1002/anie.202522758
• Primary Citation Related Structures: 
  9HD5, 9SME


• PubMed Abstract: 
  

  Ecto-5'-nucleotidase (CD73) is a potential new drug target for cancer immunotherapy. Its overexpression is associated with various aggressive cancers, including triple-negative breast cancer (TNBC) and pancreatic cancer, making it a promising target for diagnostic imaging. Besides antibodies, small-molecule CD73 inhibitors have been developed and are currently in clinical trials. This study aimed to develop and evaluate fluorine-18 labeled high-affinity CD73 inhibitors as tracers for the non-invasive positron emission tomography (PET) imaging of CD73 expression in cancer. Two CD73 inhibitors were selected for radiolabeling based on their high potency (K _i values of ca. 1 nM) and favorable pharmacokinetic properties, yielding [ ¹⁸ F]PSB-19427 ([ ¹⁸ F]1) and [ ¹⁸ F]MRS-4648 ([ ¹⁸ F]2). Ex vivo imaging studies on human breast cancer tissues indicated specific binding of both radiotracers. Subsequent in vivo studies proved [ ¹⁸ F]1 to be superior due to its long elimination half-life and its accumulation in TNBC and pancreatic cancer tissues, suggesting its potential as a versatile PET tracer for imaging of various solid tumors. Compared to [ ¹⁸ F]FDG, [ ¹⁸ F]1 was superior in visualizing TNBC, offering potential advantages over [ ¹⁸ F]FDG in terms of specificity and diagnostic accuracy. Thus, [ ¹⁸ F]1 is a PET tracer with outstanding properties suitable for broad application in cancer diagnosis and personalized medicine.

---

Organizational Affiliation: 
• European Institute for Molecular Imaging (EIMI), University of Muenster, Münster, Germany.
PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry University of Bonn, Bonn, Germany.
Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Department of Nuclear Medicine, University Hospital Muenster, Münster, Germany.
Institut Für Pharmazeutische und Medizinische Chemie, University of Muenster, Muenster, Germany.
Medicity Research Laboratory and InFLAMES Flagship, University of Turku, Turku, Finland.
Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine, Leipzig University, Leipzig, Germany.
Turku Bioscience Centre, University of Turku and Åbo Akademi University, Turku, Finland.
Department of Pathology, University of Turku and Turku University Central Hospital, Turku, Finland.
Werner Siemens Imaging Center, Eberhard Karls University of Tuebingen, Department of Preclinical Imaging and Radiopharmacy; Cluster of Excellence iFIT (EXC 2180), Image-Guided and Functionally Instructed Tumor Therapies, Tuebingen, Germany.

Biological Assembly 1  

Global Symmetry: Cyclic - C2  (Explore in 3D)
Global Stoichiometry: Homo 2-mer - A2 

Biological assembly 1 assigned by authors and generated by PISA (software)

Biological Assembly Evidence: gel filtration

Macromolecule Content 

• Total Structure Weight: 121.4 kDa 
• Atom Count: 8,195 
• Modeled Residue Count: 1,026 
• Deposited Residue Count: 1,084 
• Unique protein chains: 1

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
5'-nucleotidase	A, B	542	Homo sapiens	Mutation(s): 0  Gene Names: NT5E, NT5, NTE EC: 3.1.3.35 (PDB Primary Data), 3.1.3.5 (PDB Primary Data), 3.1.3.89 (PDB Primary Data), 3.1.3.91 (PDB Primary Data), 3.1.3.99 (PDB Primary Data)
UniProt & NIH Common Fund Data Resources
Find proteins for P21589 (Homo sapiens) Explore P21589  Go to UniProtKB:  P21589
GTEx:  ENSG00000135318

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
A1IT6 (Subject of Investigation/LOI)	E [auth A], H [auth B]	[[(2~{R},3~{S},4~{R},5~{R})-5-[2-chloranyl-6-[[4-[1-(2-fluoranylethyl)-1,2,3-triazol-4-yl]phenyl]methyl-propyl-amino]purin-9-yl]-3,4-bis(oxidanyl)oxolan-2-yl]methoxy-oxidanyl-phosphoryl]methylphosphonic acid C25 H32 Cl F N8 O9 P2 HUGOUIYDRYRLCG-UMCMBGNQSA-N
ZN	C [auth A], D [auth A], F [auth B], G [auth B]	ZINC ION Zn PTFCDOFLOPIGGS-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.91 Å
• R-Value Free:  0.273 (Depositor), 0.276 (DCC) 
• R-Value Work:  0.190 (Depositor), 0.208 (DCC) 
• R-Value Observed: 0.194 (Depositor) 

Space Group: P 2₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 92.635	α = 90
b = 233.367	β = 90
c = 54.058	γ = 90

Software Package:

Software Name	Purpose
BUSTER	refinement
XDS	data reduction
Aimless	data scaling
STARANISO	data scaling

Structure Validation

Entry History 

& Funding Information

Deposition Data

• Released Date: 2025-11-19 
Deposition Author(s): Strater, N., Moschuetz, S., Dobelmann, C., Schmies, C.C., Jacobson, K.A., Muller, C.E., Junker, A.

---

Funding Organization	Location	Grant Number
German Research Foundation (DFG)	Germany	JU 2966/2-2
German Research Foundation (DFG)	Germany	SFB 1328

Revision History  

• Version 1.0: 2025-11-19
  Type: Initial release
  
• Version 1.1: 2026-08-12
  Changes: Database references