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

Preclinical imaging and therapy

Marion de Jong

Content

Introduction Preclinical Imaging Preclinical Therapy Radiopharmaceuticals

(radiopeptides, targeted imaging and therapy)

Radionuclides

to raise awareness about problems related to translation of animal studies

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 µl/ 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

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

Important differences

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

Study to determine

• ptimal imaging conditions

MIP ¡(@ ¡180°) ¡ ¡ White-­‑Black: ¡ 0-­‑15% ¡max ¡Bq/ml ¡ ¡ ∑ ¡90” ¡scans ¡shown ¡

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 tail vein Needle tail vein Needle peritoneal Needle tail vein Cannula tail vein Awake after injection No No No 60’ No Scantime 90’ 90’ 90’ 30’ 90’

Performing animal imaging

NanoSPECT/CT system Heating Isoflurane

NanoSPECT/CT

• Equipped with heated rat- and mouse beds
• Connection for isoflurane anesthesia

Content

Introduction Preclinical Imaging Preclinical Therapy Radiopharmaceuticals

(radiopeptides, targeted imaging and therapy)

Radionuclides

Targeted imaging and therapy Targets on tumor cells: extracellular and intracellular

Courtesy Steve Mather

Extracellular Transporters Neurotransmitter receptors Hormone receptors Neuropeptide receptors Growth Factor receptors Antibody Epitopes Intracellular Metabolic pathways DNA/RNA Other organelles

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

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

Example: Regulatory peptides

Somatostatin analogues binding NE tumours

Linker Peptide

O N N N N COOH HOOC HOOC C

D-Phe - Cys - Tyr

N H

Lys

• Thr

Cys Thr- D-Trp

S S

90Y 111In 67/8Ga 177Lu

Residualizing radionuclides

• 1. Diagnosis
• 2. Therapy

Diagnosis and Therapy

+

Theranostics

Diagnostic Radionuclides

Radiometal Half-life: t1/2 (h) Decay mode Eγ/Eβ+ (keV) Production

99mTc

6.0 IT (100%) 141

99Mo/99mTc

generator

111In

67.2 Auger, EC (100%) 172,247 cyclotron

67Ga

78.1 Auger, EC (100%) 91,93,185,296,38 8 cyclotron

68Ga

1.1 β+ (90%) EC (10%) 820,1895

68Ge/68Ga

generator

64Cu

12.9 β+ (19%) β- (40%) EC (41%) 654 cyclotron, reactor

86Y

14.7 β+ (33%) EC (66%) 1043,1248,1603, 2019,2335 cyclotron

EC: electron capture, IT: isomeric transition

Gamma (γ) / positron (β+) emitting radiometals for diagnostic radiopeptides

Therapeutic Radionuclides

Beta (β-) emitting radiometals used for preparing therapeutic radiopeptides

Radiometal Half-life, t1/2 Decay mode Range (mm) Production max β- (MeV) γ (keV)

188Re

17 h 2.12 155 2.4

188W/188Re generator 186Re

90.6 h 1.07 137 0.7 reactor

90Y

64.1 h 2.27 none 2.8

90Sr/90Y generator 177Lu

6.7 d 0.5 (79%) 208, 113 0.6 reactor

67Cu

61.9 h 0.58 (20%) 91,93,185, 395,484,577 0.6 accelerator

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:

• higher sensitivity
• use of physiol. tracers
• better quantification
• less noise

Advantages of SPECT tracers:

• have longer half-lives
• are cheaper
• more widely available
• higher resolution
• dual isotope studies

PET SPECT Resolution 2 mm <1 mm Sensitivity pmol nmol Quantification ++ + Tracer half-lives sec’s, hr’s hr’s, days Tracers Physiologic Modified Modified Physiologic Early kin. (min) +++ + Late kin. (days) +/- ++

MicroSPECT and microPET in Erasmus MC

Inveon NanoSPECT/CT U-SPECT/CT Vector

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

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

Post therapy imaging: longitudinal

PC3 xenografts (111In-bombesin) microdosimetry

Sagittal Coronal Transversal

Inhomogeneous tumour uptake

• f 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 § PET § - spatial resolution

Melis et al., J Nucl Med 51:973-7, 2010

Longitudinal studies !

177Lu-production

Conventional:

176Lu +n/γ è 177Lu

NCA:

176Yb +n/γ è177Yb (T½=1.9 h)

è177Lu

177Lu production

Conventional: 176Lu +n/γ è 177Lu

• J in medium and low flux reactors
• L only 20% is converted è relatively low specific activity
• L 0.04 % of long-lived 177mLu (T½=160 days) is produced

NCA: 176Yb +n/γ è 177Yb (T½=1.9 h) è177Lu + β-

• J 100% yield è high specific activity achievable
• L high flux reactor
• L separation procedures

Treatment None 278 MBq conventional 177Lu-octreotate (11 µg) 278 MBq NCA 177Lu-octreotate (2.1 µg)

PRRT in CA20948 tumour-bearing rats

SPECT/CT day 1, 2, 4 and 8 p.t.

• Quantification of tumour uptake/volume
• Clearance rate and dosimetry

Monitoring 3x / week for 50 d p.t.:

• Tumour size (calliper)

SPECT/CT day 1 p.t. Lu-octreotate

NCA 177Lu-octreotate, 2 µg

• Conv. 177Lu-octreotate, 11 µg

adrenals tumour tumour

Acknowledgements: Preclinical groups Nuclear Medicine/Radiology