Design of Molecular Ligands for Nuclear Imaging

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1 Design of Molecular Ligands for Nuclear Imaging Michaela Katja Möllmann JASS

2 Outline (RP) II. III. IV. Ligands as Radiopharmaceuticals (RP) Design of RP Molecular Ligands Conclusion -2-

3 Definition of Radiopharmaceuticals: Radiopharmaceuticals are radioactive agents used in the field of nuclear medicine as tracers for nuclear imaging. What are the objectives? diagnosis therapy -3-

4 Nuclides for Nuclear Imaging Technetium 99m Tc Iodine 123 I / 125 I Indium 111 In Gadolinium 67 Ga Thallium 201 Tl Krypton 81m Kr Dosage Fluorine 18 F Carbon 11 C Nitrogen 15 N Rhenium 188 Re Yttrium 90 Y Lutetium 177 Lu 1 Bq (Becquerel) = one decay event per second 1 Bq = Ci 5 µci 35 mci Considerations allergy, pregnancy, breast-feeding, age, intake of other medicine, other medical problems -4-

5 Definition of Ligand: In biology a ligand is an extracellular substance which binds in a highly specific manner to its receptor. Structure Characteristics Used Molecules Detected Diseases Definition of Receptor: In biology a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to its ligand and initiates the cellular response to the ligand

6 Structure Characteristics Used Molecules bioactive molecule receptor target Detected Diseases -6-

7 Binding to pathologically occuring molecules No uptake in non-target organs/tissue Rapid localization at target Rapid blood-pool clearance Uptake ~ strength of disease Accessibility from the outside of the cell Easy to radiolabel Storage in kit with long shelf-life Cheap Reasonable dosiometry Minimal immunological response Structure Characteristics Used Molecules Detected Diseases -7-

8 Peptide-based molecules antibodies Fab-fragments scfv-fragments affibodies peptides Non-peptidic synthetic peptidomimetics Fab white blood cells scfv Structure Characteristics Used Molecules Detected Diseases

9 Tumors Infections Inflammations Neurological diseases Blood vessel diseases Red blood cell diseases Bone and bone marrow diseases Diseases of several organs... Structure Characteristics Used Molecules Detected Diseases -9-

10 Tumor-induced angiogenesis -10- αvβ3- antagonists Haubner and Wester 2004

11 αvβ3 Integrin Antagonists Aim: lead structure is needed RGD-peptide - D Val 5 Phe 4 hydrophobic Asp 3 Gly 2 Arg 1 R D G -11-

12 Iodine-Labeling 125 I D-Phe 4 D-Tyr 4 Asp 3 Val 5 Arg 1 Val 5 Tyr 5 Gly Haubner and Wester 2004

13 Fluorine-Labeling 18 F a) No-carrier-added via prosthetic groups Val 5 Lys 5 FBA FBA = N-succinimidyl 4- [ 18 F]-fluorobenzoate -13- Haubner and Wester 2004

14 Fluorine-Labeling 18 F b) Carrier-added via [ 18 F]AcOF AcOF = 18 F-Acetylhypofluoride CH 3 CO 2 18 F -14- Haubner and Wester 2004

15 Aim: Bioavailability Solubility Resistance Glucose D-Phe 4 D-Tyr 4 Glucose-based sugar amino acid Val 5 Lys Haubner and Wester 2004

16 Galactose Val 5 Lys Galactosebased sugar

17 Receptor specific tumor visualization via galactose-based RGD-peptide D-Phe HN Asp CONH Gly HO HO O CO Arg O NH Lys OH H N 18 F O ROI-ratio -17-

18 Aim: Positive effect of hydrophilicity on pharmacokinetic Use of D-amino acids allows in vivo fine tuning GABA-(D-Asp) GABA- (D-Ser) 3 Val 5 Lys 5 Haubner and Wester 2004

19 111 In Indium-labeling via DTPA Val 5 Lys InDTPA DTPA = diethylenetriaminepentaacetic acid -19- Haubner and Wester 2004

20 99m Tc-, 188 Re- and 90 Y-labeling via tetrapeptide or DOTA H-Asp-Lys-Cys-Lys-OH Val 5 Lys 5 DOTA DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetra acetic acid -20- Haubner and Wester 2004

21 Cys 9 Phe 8 Cys 7 HYNIC Cys 1 Asp 2 Cys 3 Asp 6 Gly 5 Arg 4 HYNIC = hydrazinonicotinamide Important: check influence of radiolabeling and modification on affinity -21- Haubner and Wester 2004

22 Aim: tumor accumulation 18 F-labeling -22- H-Lys-Pro-Gln-Val-Thr-Arg-Gly-Asp-Val-Phe- Phe-Glu-Gly-NH 2 99m Tc-labeling H-Arg-Gly-Asp-Ser-Cys-Arg-Gly-Asp-Ser- Tyr-OH Increased affinity by introducing two RGD motifs

23 Aim: Oral bioavailability GBHO derivatives Iodine Fluorine GBHO = guanidinobenzoyl hydrazino oxopentanoic acid -23-

24 Cyclo RGD Comparison Peptidomimetic -24- Haubner and Wester 2004

25 Quinolone core-based Indazole core-based -25- Haubner and Wester 2004

26 Heterogenous Dimer Aim: tumor accumulation DTPA moiety octreotate cyclo(-arg 1 -Gly 2 -Asp 3 -DTyr 4 -Glu 5 -) DTPA = diethylenetriamine-pentaacetic acid -26- Haubner and Wester 2004

27 Homogenous Dimer Aim: improvement of targeting by cooperative receptor-ligand binding glutamic acid cyclo(-arg 1 -Gly 2 -Asp 3 -DPhe 4 -Lys 5 -) DOTA M = 111 In, 90 Y, 177 Lu HYNIC -27- Haubner and Wester 2004

28 Homogenous Multimer Monomer Diaminopropionic acid aminooxyacetate modified heptaethylen glycol linker cyclo(-arg 1 -Gly 2 -Asp 3 - DPhe 4 -Glu 5 -) -28- Haubner and Wester 2004

29 Homogenous Multimer Dimer Lysine-branching cyclo(-arg 1 -Gly 2 -Asp 3 -DPhe 4 -Glu 5 -) -29- Haubner and Wester 2004

30 Homogenous Multimer Tetramer -30- Haubner and Wester 2004

31 Requirement of Lead Structure Direct Labeling easy, but uptake of lipophilic structures by liver Modification with Carbohydrates: no more uptake in liver Modification with hydrophilic tetrapeptide: good tumor-to-background ratios Radiometal-Labeling: Uptake in kidney Non-peptidic Substances with high affinities Multimerization can improve tumor uptake No gold standard -31-

32 Acknowledgements Prof. Dr. Horst Kessler Franz Hagn Everybody who helped organizing JASS

33 References Kessler, H. et al. several articles Haubner, R. and Wester, H.J., Radiolabeled Tracer for Imaging of Tumor Angiogenesis and Eavaluation of Anti-Angiogenic Therapies, Current Pharmaceutical Design, 2004, Vol. 10, Johannsen, B. and Pietzsch, H.J., Development of technetium-99m-based CNS receptor ligands: have there been any advances?,springer-verlag, 2001 Kumar, V., Radiolabeled white blood cells and direct targeting of microorganisms for infection imaging, Q J Nucl Med Mol Imaging, 2005, Vol. 49, Maecke, H.R., et al., 68Ga-Labeled Peptides in Tumor Imaging, The Journal of Nuclear Medicine, 2005, Vol. 46 Steffen, A.C. et al., Affibody-mediated tumour of HER-2 expressing xenografts in mice, Springer-Verlag, 2005 Young-Seung, K. et al., A Novel Ternary Ligand System Useful for Preparation of Cationic 99mTc-Diazenido Complexes and 99mTc-Labeling of Small Biomolecules, Bioconjugate Cem, 2006, Vol. 17,

34 Thanks for your attention -34-

Design of Molecular Ligands for (Nuclear) Imaging

Design of Molecular Ligands for (Nuclear) Imaging Michaela Katja Möllmann March 2006 Abstract There is a keen interest in methods which allow non-invasive monitoring of molecular targets involved in several pathological processes such as cancer. The most