Learning Objectives:
Understand convection-enhanced delivery and its implication for brain tumour treatment
Understand how gold nanoparticles can be used to construct radiation nanomedicine
Learn how to evaluate the safety, toxicity, and effectiveness of radiation nanomedicines
Overview:
Glioblastoma is a devastatingly aggressive type of brain tumour with a low median, and 5-year survival that has lacked new treatment options, in part due to the inability of therapeutic agents to cross the blood-brain barrier. Convection Enhanced Delivery (CED), a clinical neurosurgical strategy has been used to locoregionally deliver various therapeutic agents within the brain. Radiotherapeutic agents, such as 177Lu-labeled gold nanoparticles (177Lu-AuNP), hold promise for treatment of glioblastoma when administered by CED. Intratumoural injections of 177Lu-AuNP administered by CED was evaluated in an orthotopic xenograft mouse model of glioblastoma. SPECT/CT and biodistribution studies were used to evaluate the fate of the 177Lu-AuNP after injection. These results were used to estimate organ radiation absorbed doses. Normal tissue toxicity was evaluated to confirm the safety of the injections. Magnetic resonance imaging and bioluminescence imaging were used to monitor tumour growth after administration of 177Lu-AuNP, and median survival was estimated.
Unit-IV; Professional Sales Representative (PSR).pptx
(March 29, 2023) Webinar: Evaluating Intracerebral Injections of Radiation Nanomedicine in a Preclinical Mouse Model of Glioblastoma
1. Evaluating Intracerebral Injections of Radiation
Nanomedicine in a Preclinical Mouse Model of
Glioblastoma
Constantine Georgiou
PhD Candidate, Department of Pharmaceutical Sciences
University of Toronto
2. Outline
1. Introduction to Glioblastoma (GBM) and treatment
2. What is radiation nanomedicine?
3. Animal models, intracerebral injections, methods
4. Biodistribution, SPECT/CT imaging, dosimetry, toxicity
5. Therapeutic evaluation
6. Future directions
2
3. Glioblastoma (GBM)
2/10 Canadians diagnosed
with any brain tumour will
survive 5 years
<1/10 Canadians
diagnosed with GBM
will survive 5 years
• GBM is the most aggressive and most common malignant brain tumour
• Classified as a high grade (IV) astrocytoma
• While rare compared to other cancers, GBM is always fatal
• GBM incidence: 3-4 per 100,000
• GBM median OS: 12-15 months
Glioblastomas
56.60%
Diffuse
astrocytomas
Glioma
malignant
Ependymal
tumors
Anaplastic
astrocytomas
Oligodendrogliomas
Pilocytic
astrocytomas
Oligoastrocytic
tumors
All others
gliomas
3
Background Rationale Results Future Directions Conclusion
Louis, D., et al. Acta Neuropathologica (2016)
5. Treatment Challenges – Residual Disease
The BBB prevents the
majority of chemotherapies
from being effective
Molecular resistance
to Temozolomide
chemotherapy
Complete resection
is impossible
Limited to 60 Gy by external
beam radiotherapy
5
Background Rationale Results Future Directions Conclusion
1. Treatment fails to eliminate residual disease
2. Recurrence occurs within 2-4 cm of the
original tumour
3. No standard treatment for recurrent
disease
What strategies are
available to solve this
problem?
6. Convection Enhanced Delivery (CED)
• Most therapeutic agents do not
reach effective concentrations
after oral or I.V. administration
• CED catheters are inserted into
the tumour region
• External infusion pump creates a
pressure gradient that infuses
the therapeutic agent
• Compatible with wide range of
therapeutic agents
6
Mehta, A.M., et al. Neurotherapeutics (2017)
Background Rationale Results Future Directions Conclusion
7. Background Rationale Results Future Directions Conclusion
Selecting a Therapeutic Agent for CED
7
AuNP Chelator Radionuclide
Radiolabeled AuNP
8. Functionalizing Gold Nanoparticles (AuNP)
• Functionalization is a key ability of AuNPs
• AuNP drug delivery alters the PK of the
therapeutic agent
• Compatible with a wide variety of
therapeutic molecules
• Radionuclides are uniquely positioned
for treating GBM residual disease
• Cancer has reduced capability to repair DNA
damage caused by ionizing radiation
• Generates a predictable therapeutic field
8
Her, S., Jaffray, D.A., Allen, C. Adv. Drug Deliv. Rev. 2017
Inside Particle
Range
Outside
Particle Range
Background Rationale Results Future Directions Conclusion
9. AuNP Functionalization – Metal Chelating Polymer
• Coat AuNP surface with di-block
metal chelating polymer (MCP)
• Section 1: PEG 2kDa
• Increases stability, reduces
aggregation and MPS uptake
• Section 2: poly-glutamine peptide
with 8 pendant DOTA
• Chelates large amounts of activity
• Section 3: poly-glutamine peptide
with 4 pendant Lipoic Acid groups
• High number of Au-S bonds
increases stability
1 2 3 Dr. Mitch Winnik
Department of
Chemistry
U of T
9
Background Rationale Results Future Directions Conclusion
10. Radiation Nanomedicine – Radionuclide
10
Pouget, J.P., et al. Nat. Rev. Clin. Oncol. (2011)
β- α
Auger Electron
Physical
Parameter
β- Particle α Particle
Auger
Electron (AE)
Energy 0.05 – 2 MeV 5 – 9 MeV <25 keV
Range in
Tissue
mm – cm
pathlength
Many cell
diameters
μm – mm
pathlength
Several cell
diameters
nm – µm
pathlength
≤ 1 cell
diameter
Linear Energy
Transfer
0.1 – 1.0
keV/µm
50 -230
keV/μm
4 – 26
keV/µm
Best Suited
For:
Small to
medium
tumours
Small volume
metastases
Single cells,
micro-
metastases
Radionuclide 177Lu 225Ac 111In
Background Rationale Results Future Directions Conclusion
11. Radiation Nanomedicine – Hypothesis
CED of AuNPs radiolabeled with 177Lu will be effective in controlling GBM recurrence
AuNP
Metal Chelating
Polymer (MCP) 177Lu 177Lu-MCP-AuNP
Intraoperative
Administration for
Residual Tumour
11
Background Rationale Results Future Directions Conclusion
12. Animal Model and Experiments
Inoculate NRG mouse
with U251-Luc Human
GBM cells (2x105
cells/mouse)
Inject with 5 µL of
177Lu-AuNP or
control
SPECT/CT +
MRI + BLI
12
Biodistribution
Toxicity
Therapy
Background Rationale Results Future Directions Conclusion
14. Biodistribution – microSPECT/CT Imaging
14
177
Lu-MCP-AuNP
177
Lu-MCP
Day 0 Day 7 Day 14 Day 21
Day 0 Day 1 Day 2 Day 3
Representative
1 MBq 177Lu
CED injection,
not decay
corrected
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
15. Biodistribution – Whole Body Retention
15
0 5 10 15 20
0
25
50
75
100
125
Whole Body Retention After Intracranial Injection
Days Post Injection
%ID
(Decay
Corrected)
177
Lu-MCP
177
Lu-AuNP
*
Background Rationale Results Future Directions Conclusion
Dose Calibrator
16. Biodistribution & Radiation Dosimetry
• Measure cumulative
radioactivity (Ã) in
critical organs from
1 h – 14 d
• Obtain published S
values
• Estimate absorbed
dose per organ using
MIRD equation
16
𝐷 = 𝐴 × 𝑆
1
2
3
4
6
7
A B
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
23. Tumour Growth – BLI
0 7 14 21
0
20
40
60
80
100
Bioluminescent Signal
Days Post Injection
Tumour
Growth
Index
Saline
Non-Radioactive AuNP
177
Lu-AuNP (1.0 MBq)
23
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
24. Tumour Growth – MRI & Histology
Saline Control
Non-Radioactive
AuNP
177Lu-AuNP
MRI 4 Weeks Post Treatment
S
a
l
i
n
e
N
o
n
-
R
a
d
i
o
a
c
t
i
v
e
A
u
N
P
1
7
7
L
u
-
A
u
N
P
(
1
.
0
M
B
q
)
0
10
20
30
40
50
60
Tumor
Volume
(mm
3
)
A B C
24
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
25. Tumour Growth – MRI & Histology
Saline Control
Non-Radioactive
AuNP
177Lu-AuNP
A B C
25
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
T: Residual Tumour
M: Tumour Margin
Contralateral (Left)
Hemisphere
26. Tumour Growth – Long Term Survival
26
Georgiou, C. et al. Mol. Pharm. (2022)
Background Rationale Results Future Directions Conclusion
0
7
1
4
2
1
2
8
3
5
4
2
4
9
5
6
6
3
7
0
7
7
8
4
9
1
9
8
0.7
0.8
0.9
1.0
1.1
1.2
1.3
Body Weight
Days Post Injection
Body
Weight
Index
(BWI)
Saline
Non-Radioactive AuNP
177
Lu-AuNP (1.0 MBq)
0 50 100 150
0
50
100
Kaplan-Meier Curve
Days Post Injection
Percent
Survival
Saline
Non-Radioactive AuNP
177
Lu-AuNP
27. Summary
• Glioblastoma remains difficult to effectively treat
• Convection enhanced delivery can be used to bypass the BBB
• Radiolabeled gold nanoparticles are uniquely suited for CED
• SPECT/CT and biodistribution can be used to track 177Lu-AuNP in vivo
• Local delivery confined to tumour with large radiation absorbed dose
• 177Lu-AuNP did not cause acute toxicity
• Molecular imaging (BLI + MRI) can be used to evaluate tumour
growth
• 177Lu-AuNP was extremely effective in controlling GBM growth
27
Background Rationale Results Future Directions Conclusion
33. Acknowledgements
Reilly Lab
Dr. Zhongli Cai
Dr. Conrad Chan
Valerie Facca
Rella Liu
Misaki Kondo
Felix Ho
Madeline Brown
Stephanie Borlase
Rutka Lab
Carlyn Figueiredo
Supervisor
Dr. Raymond Reilly
Committee Members
Dr. Christine Allen
Dr. James Rutka
Dr. Mitchell Winnik
STTARR
Teesha Komal
Deborah Scollard
CPO
Dr. Azza Al-Mahrouki
Scintica
Tonya Coulthard
33
Fastest growing and most aggressive grade of astrocytoma (WHO grade IV)
Most common glioma: 56.6%
Astrocytic tumours (including GBM) make up >75% of all gliomas
Glioblastoma incidence: approximately 3 in 100,000
Five year survival:
Pilocytic astrocytoma (I) – 94.1%
Glioblastoma (IV) – 5.6%
Surgical resection to the greatest possible extent
Depending on location within the brain
External beam radiotherapy delivered in 2 Gy fractions
TMZ given concurrently and after radiation
Surgery
While a large resection can be possible, 100% resection is impossible due to the invasive nature of GBM
Resistance
Approx 50% of GBM tumours have an epigenetic silencing that confers resistance to TMZ
Efflux transporters at the BBB block the penetration of chemotherapeutic drugs
Established and novel drugs must effectively bypass the BBB
Attempted chemotherapies have failed during clinical trials
CED is capable of injecting a wide range of therapeutics since delivery relies on convection (pressure gradient) not diffusion
Means that infusion is not correlated with molecular weight
Optical, thermal, radiation dose enhancement
Control over physical characteristics
Size, shape, surface
Useful physicochemical properties
Easily modifiable surface provides endless functionalization options
Gold-thiol conjugation chemistry
AuNPs often used as a liquid drug delivery vehicle
DNA repair pathways are usually impaired in cancer cells, additionally rapidly dividing cells expose DNA more often making them more susceptible to damage
Radionuclide does not need to enter every cell, the effective range depends on the radionuclide
MPS (mononuclear phagocyte system)
Made up of
Monocytes and macrophages (immune cells) that accumulate in the lymph nodes, spleen
Kupffer cells in the liver
Beta particle stuff
Beta particle decay occurs in neutron rich nuclei, where a neutron is converted to a proton and an electron is released
197Hg stuff
Auger electrons are released by proton rich nuclei by electron capture and or internal conversion
Electron capture
Inner shell electron is absorbed into the nucleus and combines with a proton which transforms into a neutron and releases an electron neutrino
Outer shell electron replaces the captured inner one and energy must be released, usually in the form of an xray or that energy is given to another electron and is ejected
Atomic number is reduced by 1 since the proton is lost but the mass number doesn’t change
NRG mice chosen since they are more radioresistant than NOD/SCID mice but can still receive the tumour xenograft
Carry two mutations:
Targeted knockout mutation of the recombination activating gene 1
Renders the mice B and T cell deficient
Immunodeficiency lets tumour cells be engrafted
Complete null allele of the IL2 receptor common gamma chain
Prevents cytokine signalling in multiple receptors so that NK cells are deficient
Scid backgrounds have a mutuation in the DNA repair enzyme Prkdc (DNA-dependent protein kinases) which makes them more sensitive to radiation and drugs
MIP bone scan
Representative images, data on next slide not from the same mice/experiment
Not decay corrected, loss of intensity is a combination of radioactive decay and redistribution
Learn PK models
MIRD = Medical internal radiation dose
Alanine Aminotransferase
Creatinine
Glucose
Total Protein
White blood
Red blood
Hemoglobin
Platlets
Alkaline phosphatase
Blood urea nitrogen
Hematocrit
When the radiofrequency energy is stopped, another effect is that the protons lose their in-phase spin or precession, and begin to precess out-of-phase again as shown on the left of this slide. This process is called spin-spin relaxation.
The graph at the right shows the proportion of protons exhibiting in-phase precession vs. time in msec after the radiofrequency energy is stopped. The time taken for 63% of the protons to lose their in-phase precession, or in other words, 37% of the protons retaining their in-phase precession is known as T2. This will be important to understand when I discuss T2-weighted MRI later in the lecture.
Right
177Lu-AuNP treated mouse, residual tumour identified with normal brain tissue (no radiation necrosis) outside on the margins
Contralateral side is completely normal
Ideal immune system activation against cancer
Antigens are picked up by dendritic cells and presented to T Cells for activation
Activated T cell finds tumour and recognizes the antigen
Leads to cell death
Binding of PD-1 to PD-L1 on cancer cells deactivate the T Cell and leads to immune system evasion
Tumour cells often upregulate PD-L1
Associated with increased tumour aggressiveness and lower survival
Use of anti-PD-1 antibody blocks the PD-1/PD-L1 binding and keeps the T cell activated
The immune system can attack the tumour cell