1845-1923

1. 1845-1923

2. High Spatial ResolutionCT, MRI, Optical, & US • MRI Imaging • High Density, Internalizing Receptors • Transferrin receptor w. Transferrin MION • Optical Imaging • Physiologic measurements • Volume, flow, Hb O2 • Fluorescent-labeled ligands • Ultrasound Imaging • Physiologic measurements • Targeting with a single, site-directed bubble.

3. The Advantage of Radionuclides for Targeted Imaging, especially Low Density Sites (<20 nM)

4. George Charles de Hevesy • The first to identify the radioisotope tracer principle. • In 1923, he used 10.6 hour lead-212 to study the uptake of solutions in bean plants, noninvasively. Used small, non-toxic amounts given the sensitivity of the radioactivity techniques. • The first experiment in animals used Bi-210 to label and follow the circulation of Bi-containing antisyphilitic drugs in rabbits. • In a later book with Fritz Paneth, the tracer method was introduced as the use of radioelements as indicators.

5. The first practical application of a radioisotope was made by George de Hevesy in 1911. • He suspected that meals that appeared regularly might be made from leftovers. • To confirm these suspicions de Hevesy put a small amount of radioactive material into the remains of a meal. • When the same meal was served, it was radioactive! History has forgotten the landlady, but George de Hevesy went on to win the Nobel prize in 1943 and the Atoms for Peace award in 1959.

6. Imaging the In Vivo Distribution of a Gamma Emitting Radioisotope

7. Unprecedented Progress • 1937 Discovery of the element Tc • 1947 Isolation of Tc-99 • 1958 Technetium Generator • 1970 Instant DTPA, HSA, & RBC Kits • 1978 Crystal structures of potential Tc radiopharmaceuticals • 2002-present • Smaller, neutral, more polar inert chelates • Maximal effective specific activity • Tc labeled molecules ~300 MW

8. 1934 photo of Livingston and Lawrence with the 27” cyclotron at LBL

9. In 1938, Glenn Seaborg and Emilio Segre discovered Technetium-99m.

10. Walter Tucker Powell Richards

11. Mechanism: TcO4- + stannous ion = reduced Tc + chelating agent or particle = final product Kit components = stannous salt (reducing agent) & chelating agent or particle

12. RS-[123I]IQNB on 5/11/83

13. Market Analysis and Future Prospects • U.S. sales of diagnostic radiopharmaceuticals reached $1.53 billion in 2004 and are expected to rise to $3.20 billion by 2010. • This growth will be based on introduction of new products, strong demand for cardiology procedures and increased sales of oncology products, particularly FDG for PET imaging. • Nuclear cardiology sales of $1.06 billion in 2004 will increase to $1.89 billion by 2010. • FDG sales for oncology as well as cardiology and neurology will increase from $249 million in 2004 to $522 million by 2010. • In addition, new PET radiopharmaceuticals in the pipeline for specialized applications should add to these sales estimates.

14. Market Analysis and Future Prospects • U.S. sales of therapeutic radiopharmaceuticals were still on the threshold in 2005, with total sales of $57 million. • Rapid growth is anticipated over the next 5-6 years. By 2012, therapeutic product sales should reach $1.9 billion, with high continuing growth beyond that time. • This will be based on the introduction of new therapeutic radiopharmaceuticals for treating lymphoma, colon cancer, lung cancer, prostate cancer, bone cancer and other persistent cancers. These agents will be used in conjunction with traditional therapies, enhancing their effectiveness, with better specificity and reduced side effects. Individualized Medicine!

15. DEVELOPMENT OF Enzyme/Receptor Targeting in humans DATE PET SPECT 1977 [18F]FDG 1983 [11C]N-MeSpip [123I]IQNB 1984* [18F]Cyclofoxy 1985 [11C]Raclopride [99mTc]NGA 1985 [11C]Carfentanil 1985 [11C]Flumazenil How many radiotracers have changed clinical care? How many have been used in combination with pharmaceuticals?

16. The Principle of PET: Coincidence Detection of Two 511 KeV Gamma Rays is Used to Determine the Position

17. PET RADIONUCLIDE PRODUCTION T1/2 (min) E+ (kev) Nuclear Reaction 82Rb 1.3 3350 82Sr generator 11C 20 960 14N (p,)w. 6 ppm O2 13N 10 1190 16O (p,) 15O 2.05 1720 14N (d,n) w. 2% O2 18F 109.6 635 20Ne (d,) w. 0.5%F2 18F 109.6 635 18O (p,n) 76Br 966 3980 75As (a,3n) 64Cu 762 571 64Ni (p,n) 124I 5976 2134 124Te (p,n)

18. FDG:1976 to 2002

19. Imaging Saturable Sites with MRI • Relatively High Capacity, Internalizing Sites. • Mion-Transferrin • Substrates For Enzymes. • FDG • High Capacity, Non-internalizing Binding Sites. • A Gd complex of polyDTPA polyneogalactosyl dextran. • Low Capacity, Non-internalizing Binding Sites. • Gd antibodies targeted to solid tumors. • Gd labeled antibodies targeted to endothelial sites.

20. In Vivo MR Imaging: MR image of a mouse with TfR+ and TfR- flank tumors (a) The T1-weighted coronal SE image (3.5 min; 0.3x0.3x3 mm3 resolution). TfR- tumors (right arrowhead) and TfR+ tumors (left arrowhead) have similar signal intensity. (b) Corresponding T2-weighted gradient echo image showing significant difference (8 min; same resolution). TfR-mediated cellular accumulation of the superparamagnetic probe decreases signal intensity as expected using T2- and T2*-weighted imaging pulse sequences on cellular internalization. (c) Composite of a T1-weighted spin echo image obtained for anatomic detail with superimposed R2 changes after Tf-MION administration displayed in a color map.

21. Other Imaging Modalities for desialylated glycoproteins binding to the high capacity (~500 nM) hepatic binding protein [Gd]DTPA-galactosyl-Dextran Post-injection: 3.8 min Liver: 66 % Enhancement

22. How can targeted imaging accelerate drug discovery? William C Eckelman PhD Bethesda MD

23. Definitions: Molecular Imaging • The term molecular imaging can be broadly defined as the in vivo characterization and measurement of biologic processes at the cellular and molecular level. [Weissleder & Mahmood, Radiology 2001]. • MI techniques directly or indirectly monitor and record the spatiotemporal distribution of molecular or cellular processes for biochemical, biologic, diagnostic, or therapeutic applications [Thakur & Lentle, Radiology 2005].

24. Targeting ProteinsThe Magic Bullet Paul Ehrlich used the English expression “magic bullet” for the first time in his Harben Lectures. The German word “Zauberkugel” appears earlier in his thoughts and publications, based on his view of “sidechains”, the precursor of our concept of receptors, and on the desirable property of drugs that must not harm the host, but attach the parasitic invader. Royal Institute of Public Health (London:Lewis, 1908), Experimental Researches on Specific therapy. On immunity with special references to the relationship between distribution and action of antigens, 107.

25. The Magic Bullet • Ehrlich’s first magic bullet was Salvarsan or arsphenamine, discovered in 1909, which provided the only cure for syphilis. • Ehrlich also thought of attaching toxins to antibodies whereby the antibody would carry the deadly freight to the site of the invading parasite. His idea lives on in the development of immunotoxins.

26. Both the lock and the key are necessary in Targeted Imaging • 99mTcDTPA or GdDTPA in GFR measurements is a key without a specific target (lock). GFR is a nontargeted process. • [18F]FP-TZTP is a M2 muscarinic agonist, which is transported non specifically across the BBB, but binds specifically to the M2 receptor (the lock). • Doxorubicin in liposomes is not a targeted drug although the therapeutic effect is increased by improvement in liver tox profile. Emil Fischer, 1894

27. Imaging & “Molecular Targeting” • Interactions between a probe and a protein target using pre-genomic techniques. • “Biochemical probes” such as iodide (~50 years), receptor binding radiotracers and monoclonal antibodies (~25 years) from autopsy, linkage and drug efficacy, etc. • Interactions between a probe and a protein target using post-genomic techniques. • Molecular biology, proteomics, genomics, antisense, reporter genes, protein-protein interactions. More targets (500 2000-3000)

28. Why is Targeted Imaging becoming more important in Drug Development? • As the pharmaceutical industry turns to targeted drugs, targeted imaging is well positioned to “biomark” the drug potential. • Target identification is dependent upon clinical research, i.e., “humanomics” should be the study of choice. Lindsay MA. Finding new drug targets in the 21st century. DDT 2005: 23/24: 1683.

29. The Druggable genome Nucl Horm R Russ & Lampel. The Druggable genone: an update. DDT 2005: 23/24: 1607.

30. Measuring Targeting with Imaging for targets of differing density In Vitro B/F = Bmax/Ki Imaging requires B/F ratio ~5, Drugs do not

31. Measuring the In Vivo Binding Parameters of [18F]-Fallypride in Monkeys Using a PET Multiple-Injection Protocol. Mukherjee 2005

32. Measuring occupancywith Imaging for a successful treatment

33. Specific binding of [18F]Cyclofoxy was lower by 29 to 32% in Methadone Maintained Patients. Normal Control Methadone Maintained Patient Thalamus 32  ± 15 Amygdala 24  ± 30 Caudate 24  ± 19 Ant. cingulate cortex 29  ± 20 Kling et al., J Pharm Exp Therap, 295: 1070-1076, 2000

34. Measuring Occupancywith Imaging for Multi-target drugs • A single target drug with a multi-target radiotracer. • A multi-target drug with a single target radiotracer.

35. M100907 as measured using [11C]NMSP PET in humans • Measure possible 5-HT2A receptor occupancy by measuring frontal cortex to cerebellum ratio. • Measure possible D2 receptor occupancy by measuring striatum to cerebellum ratio. • Is the Occupancy related to plasma concentration? • Is the Occupancy time course related to plasma concentration?

36. [11C]NMSP Binding at 5-HT2A & D2 receptors

37. Schizophrenia and Antipsychotic Drugs • M100907 (aka MDL 100907) is a potent and selective 5-HT2A receptor antagonist, but does not bind to the D2 receptor. • Therefore, it has the profile of an atypical antipsychotic agent. • [11C]NMSP can be used to monitor 5-HT2A and D2 receptor density changes. J Clin Pharmacol Suppl 1999

38. Sensitivity/Identifiabilityfor Drug Changes Measuring endogenous transmitter changes

39. Measuring increased dopamine.22.3% (±2.7) in schizophrenia vs. 15.5% (±1.8) in controls.Schizophrenia is associated with elevated amphetamine-induced synaptic dopamine. Breier A, Su TP, Saunders R, Carson RE, Kolachana BS, de Bartolomeis A, Weinberger DR, Weisenfeld N, Malhotra AK, Eckelman WC, Pickar D.Proc Natl Acad Sci U S A. 1997 Mar 18;94(6):2569-74.

40. Measuring increased acetylcholine.[18F]FP-TZTP as a probe for AChE inhibitors such as donepezil, rivastigmine, & tacrine. Increased ACh and 15% decrease of [18F]FP-TZTP in Ctx. Control Physostigmine Carson RE, Kiesewetter DO, Jagoda E, Der MG, Herscovitch P, Eckelman WC. Muscarinic with [18F]FP-TZTP: control and competition studies. J Cereb Blood Flow Metab. 1998 Oct;18(10):1130-42.

41. Individualized Medicine

42. Metastatic pheochromocytoma (Pheo) can be detected using [123I]MIBG (or it that is not available [131I]MIBG can be used) prior to therapy with [131I]MIBG. The mechanism of localization is based on the neuroendocrine character of this disease with the the norepinephrine transporter (NET) being the key biochemical parameter. Up to 73% of PHEO cells in vitro express somatostatin receptors so patients with Pheo have been assessed with somatostatin receptor imaging (with either [123I]Tyr3-octreotide or [111In]DTPA-octreotide). Since the presence of NET and SSR appear to be inversely related and dependent on cell differentiation, imaging both pathways can be instrumental in choosing therapy. Current Individualized Medicine

43. Current Individualized Medicine • The American College of Radiology has recently set practice guidelines for [90Y]ibritumomab tiuxetan (Zevalin) and [131I]tositumomab (Bexxar), which are approved by the FDA for radioimmunotherapy of non-Hodgkin’s lymphoma. • Both antibodies are directed against the CD20 antigen, which is found on the surface of normal and malignant B lymphocytes. • The preliminary imaging studies are to determine dosimetry or assess biodistribution before the radiotherapeutic is administered. The package insert for these two radiotherapeutics has guidelines for interpreting the imaging study and these guidelines must be met before the therapy can commence.

44. Targeted Drugs Targeted Imaging • Trastuzumab for HER2 (aka ErbB2 & Neu) • A cell surface glycoprotein with TK activity • HER2 amplification/over-expression is predictive for response in breast caner. • Overexpression became an entry criteria and higher objective response was related to level of overexpression. • Imaging study was developed with Ab fragment to match the Ga-68 half life. tra STUH zoo mab; Herceptin

45. Imaging HER2 Receptor in response to HSp90 Inhibitors • 17-allylaminogeldanamycin (17-AAG) is the first Hsp90 inhibitor to be tested in a clinical trial. • Induce proteasomal degradation of HER2 by binding to Hsp90 chaperone protein. • Label the F(ab’)2 of the anti-HER2 antibody Herceptin with Ga-68. Smith-Jones et al. Nat Biotech 2004

46. MicroPET images (coronal) of mice with BT-474 tumors with Ga-68-DOTAcHF at 3 h before and 24 h after 17-AAG Tumor & kidney Taken from Smith-Jones et al. Imaging the pharmacodynamics of HER2 degradation in response to Hsp90 inhibitors. Nat Biotechnol. 2004;22:701-6

48. Targeted Drugs • Imatinib is an inhibitor of BCR-ABL TK. • The Philadelphia chromosome and BCR-ABL have prognostic significance for chronic myeloid leukemia (CML). • Also, inhibits TK of the oncogene c-KIT in GIST. • Imatinib-resistant mutants led to BMS 354825. im MA ta nib; Gleevec

49. In Vivo Proteomics:FDG: Before and after Gleevec Taken from Demetri et al.

50. Cancer is not a single gene disease, yet ….. • Imatinib (Gleevec)-effective in GIST and CML. Mutants appeared, but further TK inhibitors have high affinity for all mutants. • Trastuzumab (Herceptin)-best in high expressors of HER2. • Gefitinib (Iressa)-EGFR TK. • Shrinks tumor, but no change in survival in NSCLC. Population specific. • Erlotinib (Tarceva) & Cetuximab (Erbitux)-MAb • Angiogenesis Inhibitors DDT 2004:9:1042-1044 Golsteyn RM. DDT 2005 10(6):381.