Preclinical imaging and therapy Marion de Jong Content - PowerPoint PPT Presentation

Preclinical imaging and therapy Marion de Jong

Content Introduction to raise awareness about problems related to translation of animal studies Preclinical Imaging Preclinical Therapy Radiopharmaceuticals (radiopeptides, targeted imaging and therapy) Radionuclides

Animals models and studies in translational reseach

Consensus on why and how? Quotes about animal studies: “ Animal research seldom applies to humans ” “ Dump animal research in favor of non-invasive methods” “ Animal studies are still done only because people can make money from it ”

Translational research: crossing the valley of death § Nature 453 , 840-842, 2008 § NIH: § Lack of translation of § basic research §

Translational research In vivo molecular imaging in small animals is a bridge between in vitro data and translation to clinical application, but … .

Be aware of differences in men vs mice § Mice and humans are > 95% identical at the genomic level, their respective phenotypes are very different: § Size, metabolism, hear beat rate, etc

Important differences § Size § Limitations for max volume injected or max volume of blood samples (about 200 µ l/ mouse) § Specific activity radiopharmaceuticals should be high, esp. in processes with low capacity, e.g. receptor binding. § Heartbeat § The heartbeat rate of a mouse : 600 beats/min § Physiological processes occur faster § Small animals can tolerate larger doses as they § - clear most chemicals from their bodies much faster § - given dose will lead to lower concentrations

Important differences § Anaesthetics § are known to alter animal physiology dramatically, § cause changes in respiration, heart rate, blood pressure, and temperature. §

J Nucl Med 2006; 47:999–1006, Fueger et al.

Study to determine optimal imaging conditions FDG IV iso IV awake IP iso IV awake 60min IV no fasting Fasted Yes Yes Yes No No Preheating 30° Yes Yes Yes No Yes Injection IV (iso) IV (awake) IP (iso) IV (awake) IV (iso) Method Cannula Needle Needle Needle Cannula peritoneal tail vein tail vein tail vein tail vein Awake after injection No No No 60’ No Scantime 90’ 90’ 90’ 30’ 90’ MIP ¡(@ ¡180°) ¡ ¡ White-­‑Black: ¡ 0-­‑15% ¡max ¡Bq/ml ¡ ¡ ∑ ¡90” ¡scans ¡shown ¡

Performing animal imaging NanoSPECT/CT • Equipped with heated rat- and mouse beds • Connection for isoflurane anesthesia Heating Isoflurane NanoSPECT/CT system

Content Introduction Preclinical Imaging Preclinical Therapy Radiopharmaceuticals (radiopeptides, targeted imaging and therapy) Radionuclides

Targeted imaging and therapy Targets on tumor cells: extracellular and intracellular Extracellular Transporters Neurotransmitter receptors Hormone receptors Neuropeptide receptors Growth Factor receptors Antibody Epitopes Intracellular Metabolic pathways DNA/RNA Other organelles Courtesy Steve Mather

Targeted Imaging & Therapy: What are we trying to achieve? § Selective imaging contrast and/or radiation dose: § é as high as possible on the tumour § ê as low as possible on normal tissues

How can we achieve this? § Choose the best target § Produce the best ligand § Obtain the best tumor uptake/binding § Treat the best patients: theranostics

Example: Regulatory peptides used/tested in the clinic as radiopeptides: • Somatostatin  neuroendocrine tumors • CCK-B, gastrin  MTC, SCLC • GRP, Bombesin  prostate, breast • Neurotensin  exocrine pancreatic tumors • Substance P  glioblastoma, astrocytoma • RGD  Newly formed blood vessels • GLP-1  insulinomas, SCLC, carcinoid

Somatostatin analogues binding NE tumours Peptide Linker O HOOC C D-Phe - Cys - Tyr N S D-Trp N N H S Lys N N Thr- Cys -Thr HOOC COOH 90 Y Residualizing 111 In 67/8 Ga radionuclides 177 Lu

Diagnosis and Therapy 1. Diagnosis + 2. Therapy Theranostics

Diagnostic Radionuclides Gamma ( γ ) / positron ( β + ) emitting radiometals for diagnostic radiopeptides Radiometal Half-life: t 1/2 (h) Decay mode E γ /E β + (keV) Production 99m Tc 6.0 IT (100%) 141 99 Mo/ 99m Tc generator 111 In 67.2 Auger, EC (100%) 172,247 cyclotron 67 Ga 78.1 Auger, EC (100%) 91,93,185,296,38 cyclotron 8 68 Ga 1.1 β + (90%) EC (10%) 820,1895 68 Ge/ 68 Ga generator 64 Cu 12.9 β + (19%) β - (40%) EC 654 cyclotron, reactor (41%) 86 Y 14.7 β + (33%) EC (66%) 1043,1248,1603, cyclotron 2019,2335 EC: electron capture, IT: isomeric transition

Therapeutic Radionuclides Beta ( β - ) emitting radiometals used for preparing therapeutic radiopeptides Decay mode Radiometal Half-life, t 1/2 Range (mm) Production max β - (MeV) γ (keV) 188 Re 17 h 2.12 155 2.4 188 W/ 188 Re generator 186 Re 90.6 h 1.07 137 0.7 reactor 90 Y 64.1 h 2.27 none 2.8 90 Sr/ 90 Y generator 177 Lu 6.7 d 0.5 (79%) 208, 113 0.6 reactor 67 Cu 61.9 h 0.58 (20%) 91,93,185, 0.6 accelerator 395,484,577

The Theranostic Approach : YouTube Movie Action BM0607, raise interest of the public Feel free to ask for the movie for eductional purposes

Content Introduction Preclinical Imaging Preclinical Therapy Radiopharmaceuticals (radiopeptides, targeted imaging and therapy) Radionuclides

Small animal imaging Scaling problems Volume: factor 1000 - 4000 Length: factor 10 - 16

AMIE Facility

Preclinical PET versus SPECT Advantages of PET: PET SPECT • higher sensitivity Resolution 2 mm <1 mm • use of physiol. tracers Sensitivity pmol nmol • better quantification Quantification ++ + • less noise hr’s, days Tracer half-lives sec’s, hr’s Tracers Physiologic Modified Advantages of SPECT tracers: Modified Physiologic • have longer half-lives Early kin. (min) +++ + • are cheaper Late kin. (days) +/- ++ • more widely available • higher resolution • dual isotope studies

MicroSPECT and microPET in Erasmus MC U-SPECT/CT Inveon Vector NanoSPECT/CT

Small animal PET/SPECT/CT imaging in oncological research Ø Pharmacokinetics and dosimetry (imaging, therapy) Ø Detection of metastases Ø Microdosimetry (kidneys, tumors) Ø Tumor response over time Ø Normal organ function over time

Biodistribution study Courtesy: Dr. T. Maina-Nock

Dynamic NanoSPECT/CT radiobombesin Time activity curve

Imaging of lung metastases, rat, Lu-octreotate + Rad001

Post therapy imaging: longitudinal Different tracers in one animal 278 MBq 50 MBq 50 MBq [ 177 Lu-DOTA]octreotate [ 111 In-DTPA]octreotide [ 99m Tc]DMSA 5 days after therapy 4h after injection 3h after injection (injection radiopeptide) 28 days after therapy 120 days after therapy

PC3 xenografts ( 111 In-bombesin) microdosimetry Sagittal Coronal Transversal Inhomogeneous tumour uptake of the radiopeptide: Receptor expression or perfusion?

Dynamic Contrast Enhanced-MRI § Measure change in tissue relaxivity after injection of contrast agent § Perfusion of contrast agent provides info on functional vessels

Maximum signal enhancement Overlay of maximum signal enhancement in tumor Contrast agent does not reach all areas of the tumor

DCE - SPECT SPECT MRI

Imaging § 1) pharmacokinetics and dosimetry (imaging,therapy) § 2) microdosimetry (kidneys, tumors) § 3) effectiveness of e.g. kidney uptake reduction § 4) tumor response over time § 5) normal organ function over time

Peptide Receptor Imaging in small animals § SPECT § - Rel. low sensitivity: § - specific act. should be high, radiochemical limitations! § - high ligand amount: (partial) saturation of the receptor § - high radioactivity dose Longitudinal studies ! § PET § - spatial resolution Melis et al., J Nucl Med 51:973-7, 2010

177 Lu-production Conventional: 176 Lu +n/ γ è 177 Lu NCA: 176 Yb +n/ γ è 177 Yb (T ½ =1.9 h) è 177 Lu

177 Lu production Conventional: 176 Lu +n/ γ è 177 Lu • J in medium and low flux reactors • L only 20% is converted è relatively low specific activity • L 0.04 % of long-lived 177m Lu (T ½ =160 days) is produced NCA: 176 Yb +n/ γ è 177 Yb (T ½ =1.9 h) è 177 Lu + β - • J 100% yield è high specific activity achievable • L high flux reactor • L separation procedures

PRRT in CA20948 tumour-bearing rats Treatment None 278 MBq conventional 177 Lu-octreotate (11 µ g) 278 MBq NCA 177 Lu-octreotate (2.1 µ g) Monitoring 3x / week for 50 d p.t.: • Tumour size (calliper) SPECT/CT day 1, 2, 4 and 8 p.t. • Quantification of tumour uptake/volume • Clearance rate and dosimetry

SPECT/CT day 1 p.t. Lu-octreotate Conv. 177 Lu-octreotate, 11 µ g NCA 177 Lu-octreotate, 2 µ g adrenals tumour tumour

Acknowledgements: Preclinical groups Nuclear Medicine/Radiology