Agonist by Means of an Antibody-Drug Conjugate Induces ...€¦ · Marc Damelin, Ph.D. Innate...
Transcript of Agonist by Means of an Antibody-Drug Conjugate Induces ...€¦ · Marc Damelin, Ph.D. Innate...
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Tumor Targeting of a STING Agonist by Means of an
Antibody-Drug Conjugate Induces Potent Anti-Tumor
Immune Responses
Marc Damelin, Ph.D.
Innate Immunity Stimulating Therapies Summit Digital Event – July 22, 2020
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Innovative and Highly Differentiated ADC Technologies and Platforms
2DAR = Drug-to-antibody ratioSTING = Stimulator of Interferon Genes
Efficacy without severe neutropenia,
neuropathy, or ocular toxicity
DolaLock Dolaflexin
Improved therapeutic index vs. other
platforms
Dolasynthen
Homogenous & Customizable Platform
Immunosynthen
Systemic administration with targeted immuno-stimulatory effect
• Controlled bystander effect
• Selectively toxic to rapidly dividing cells
• Not a PgP substrate
• Induces immunogenic cell death
• DolaLock payload
• Polymer scaffold
• DAR ~10-12
• Excellent drug like properties
• DolaLock payload
• Synthetic scaffold
• Site-specific
• Precise DAR (2-24)
• Novel STING agonist
• Complete regression with one dose in multiple preclinical models
• Limited effect on systemic cytokines
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• Preclinical evidence that STING activation induces prolonged anti-tumor activity and generates immune memory• Other agonists, including TLR7/8, have not shown similar activity in reported studies
• STING activation is more specific to potent Type I interferon gene activation, while TLR activation is associated with general inflammation
• Emerging clinical evidence that STING agonists (intratumoral injection) activate the pathway and do not have significant tolerability concerns
• STING agonists are highly compatible with bioconjugation through the platform technology as they have favorable physicochemical properties
• Oligonucleotides are less compatible (i.e. TLR9, RIG-1)
• Mersana has focused on non-CDN agonists
Why We Invested in STING over other Innate Immunity Pathways
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ADCs are suited to overcome limitations of free agonist (intratumoral or IV)
– Targeted delivery reduces toxicity liabilities • Minimize toxicity to T and B cells by selective targeting of ADCs (T cell intrinsic function)• Minimize systemic inflammation
– Improved pharmacokinetics
– Accessibility to metastatic sites
– No restriction on tumor type, location or size
Strong Rationale for a STING ADC Approach
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Holistic Approach to Build the Optimal STING ADC
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1. Platform• Payload• Linker• Scaffold• Drug-to-Antibody Ratio (DAR)
2. Target and Antibody• Immune cell antigens• Tumor cell antigens• Tumor-associated antigens
Payload molecule
Drug load per scaffold
Charge balance
Aqueous solubilityBioconjugationAntibody
Evaluation included:• Analytical• In vitro characterization• In vivo characterization• Developability
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• The target cell is not necessarily a tumor cell– Potential for new mechanisms for payload delivery– Implications for choice of targets and antibodies
• Optimal payload requirements are not known– Potency– Membrane permeability & efflux properties– Metabolism rate (once released)
• Special considerations for I-O in vivo studies– Xenograft models are grown in immune-compromised mice– Syngeneic models are not compatible with certain targets and antibodies
Immunostimulatory ADC Platform Development Cannot Be Based Solely on Cytotoxic ADC Experience
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Platform Development
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• Identified novel compounds representing multiple series– Compounds have a range of biological activity & diverse physicochemical properties
• Leveraged structure-based drug design (SBDD) and crystallography– Crystal structure solved with novel ligand bound to STING
• Filed IP
Novel STING Agonists Designed for ADCs
*Ligand has been removed from structure 8
0.01 1 100 100000
10000
20000
30000
40000
Log Drug Conc. (nM)
Benchmark1C3176C3165
IRF3
Act
ivat
ion
Examples ofnovelMersanapayloads
Payload 2
Payload 1
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Leveraging Our ADC Expertise and Proprietary Technologies
10.0 12.5 15.0 17.5 20.0 2
ADCmAb
Aggregation
12.5 15.0 17.5 20.0 22
ADC (mAb #1)ADC (mAb #2)
Optimization
Aggregation in Initial STING ADCNo Aggregation after Optimization
(STING ADCs from 2 different mAbs)
Modular Synthemer Approach Enables ADC Optimization
Payload molecule
Drug load per scaffold
Charge balance
Aqueous solubilityBioconjugationAntibody
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Summary of Exploratory Toxicology in NHP
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• Evaluated ADCs based on 3 antibodies• Dosed up to 9 mg/kg antibody (~0.3 mg/kg STING agonist)• Repeat-dose and single-dose cohorts• Clinical observations
• All animals appeared normal throughout study• No changes in body temperature• No mortality or unscheduled euthanasia
• Toxicokinetics• High exposure after both administrations; dose dependent; overall profile similar to non-STING ADCs• ADC highly stable in circulation; minimal free payload in plasma
• Serum Cytokines• Transient, modest elevation of 5 cytokines out of 24 tested; similar to results in mouse
• No adverse changes in hematology or clinical chemistry• No adverse findings in histopathology
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Targets and Antibodies
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Comprehensive Approach to Target Validation and Selection
12Image based on DOI: 10.5772/intechopen.72648
Cell Types in the Tumor Microenvironment
Macrophages
Dendritic cellsTumor Cell and Tumor-associatedAntigens
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STING Agonist ADCs with Complementary Therapeutic Rationales Based on Antigens and Target Cells
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PotentialActivation
Activation
Delivery to 2 Cell Types
Target Category Rationale
Immune Cell • Direct activation of immune cells
Tumor Cell• Delivery to tumor and immune cells• Tumor-targeted delivery
Tumor-Associated• Proximity of antigen to immune cells• Tumor-targeted delivery
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0.01 0.1 1 10 100 10000
10000
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30000
40000
Agonist [nM]
Luci
fera
se A
ctiv
ity
0.01 0.1 1 10 100 10000
50000
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Agonist [nM]
Luci
fera
se A
ctiv
ity
Targeted ADC Targeted ADC – Fc MutantControl ADCFree Payload
AntigenAntigenAntigen
FcγR
Antibody variantsTargetedAntigen and
FcγR binding
ControlNo antigen binding
Fc mutantNo FcγR binding
X X
Co-culture assay
Immune CellIRF3 reporter(Luciferase)
Cancer Cell
Recombinant antigen assay
Immune CellIRF3 reporter(Luciferase)
Antigen-coated plate
Tumor-Targeted ADC Activates STING in Immune Cells
FcγRFcγR
Legend
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Tumor-Targeted STING Agonist ADC Induces Killing of Cancer Cells by PBMCs
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Vehicle
Targeted ADC
Control ADC
Free payload
1
10100
100
10
100
10
Agonist [nM]
- Cancer cells have stable expression of a red fluorescent protein in the nucleus
- These cancer cells have minimal STING activity
PBMCs
Co-culture:Cancer cells & PBMCs
100-Fold Increased Potency of ADC over Free Agonist
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T Cells are Dispensable for Cancer Cell KillingSupports the hypothesized mechanism of action
PBMCs
CD3
CD
14
CD3+50%
Enriched Monocytes (CD14+CD16+)
CD3+4%
CD16-depleted Monocytes(CD14+CD16-)
CD3+2%
Control
Payload-4 nM
ADC-4 nM
Payload-20 nM
ADC-20 nM
PBMCs + Cancer cells
Control
Payload-4 nM
ADC-4 nM
Payload-20 nM
ADC-20 nM
Enriched Monocytes + Cancer cells Control
Payload-4 nM
ADC-4 nM
Payload-20 nM
ADC-20 nM
CD16-depleted Monocytes+ Cancer cells
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Sustained Tumor Regressions Induced by a Single Administration of STING ADC
0 7 14 21 28 35 42 49 56 63-20
-10
0
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20Body Weights
Days on Study
Bod
y W
eigh
t Cha
nge
(%)
Mea
n +/
- SEM0 7 14 21 28 35 42 49 56 63
0
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1000Tumor Growth Inhibition
Days on study
Mea
n Tu
mor
Vol
ume
(mm
3 )±SE
M
diABZI I.V. agonist (0 / 5 mg/kg)
Control ADC (1 / 0.04 mg/kg)Control ADC (3 / 0.12 mg/kg)
Targeted ADC (1 / 0.03 mg/kg)Targeted ADC (3 / 0.09 mg/kg)
Unconjugated Antibody (3 / 0 mg/kg)
• All groups dosed IV• Doses in (mAb [mg/kg] / Payload [mg/kg])
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Vehicle
Legend
10 / 10 Tumor Free
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Target-Dependent Immune Cell Infiltration and Cytokine Induction in Tumors
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Murine cytokine expression(qPCR on FFPE samples)
• ADC single dose• Tumors harvested 12 or 72 hrs post dose
Vehicle
12 hrs.
72 hrs.
Targeted ADC Control ADC
CD45 Immunohistochemistry
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12 H 12 H 12 H 72 H72 H72 H
VehicleTargeted ADCControl ADC
mCXCL10 mIL-6mIFNβ
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Dramatically Lower Induction of Serum Cytokines in Mice by STING ADC Compared to Free STING Agonist
CXCL10 IL-6 CXCL1 MIG (CXCL9)
RANTES (CCL5)
pg/m
L
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Hours
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MIP-1a (CCL3)TNF-α IFNγ
pg/m
L
Luminex assay
0 5 10 1510
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Plasma Concentration
Time (Days)
Con
cent
ratio
n [n
g/m
l]M
ean
+/- S
D
Total AntibodyConjugated Drug
STING ADC Yields Extended Exposure
Vehicle control
Targeted ADC (0.09 mg/kg payload = dose for complete tumor regression)
Control ADC (0.09 mg/kg payload)
STING diABZI I.V. agonist (5 mg/kg payload = maximum tolerated dose; 37% tumor growth inhibition) 19
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Another Target and Tumor Model:STING Agonist ADC Inhibits Tumor Growth After a Single Dose
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0 7 14 21 28 35 42 49 56 63 70 77 840
300
600
900
1200Tumor Growth Inhibition
Days on Study
Mea
n Tu
mor
Vol
ume
(mm
3 )±SE
M
Control ADC (3 / 0.1 mg/kg)Targeted ADC (3 / 0.1 mg/kg)• All groups dosed IV• Doses in (mAb [mg/kg] / Payload [mg/kg])
Vehicle
Legend
0 7 14 21 28 35 42 49 56 63 70 77 84-20
-10
0
10
20
Body Weights
Days on study
Bod
y W
eigh
t Cha
nge
(%)
Mea
n±
SEM
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Sustained Tumor Regressions After a Single Dose in a Syngeneic Model
0 7 14 21 28 350
500
1000
1500Tumor Growth - Group Means
Days on study
Mea
n Tu
mor
Vol
ume
(mm
3 )±SE
M
21
6/9 Tumor-free
2/10Tumor-free
Dose: mAb / payload (mg/kg)
0 7 14 21 28 35-20
-10
0
10
20Body Weight
Days on studyB
ody
Wei
ght C
hang
e (%
)M
ean±
SEM
0 7 14 21 28 35 42 490
500
1000
1500
2000
Targeted ADC (0.88 / 0.04 mg/kg)
Days on Study
Tum
or V
olum
e (m
m3 )
0 7 14 21 28 35 42 490
500
1000
1500
2000
Control ADC (1.09 / 0.04 mg/kg)
Days on studyTu
mor
Vol
ume
(mm
3 )0 7 14 21 28 35 42 49
0
500
1000
1500
2000Vehicle
Days on study
Tum
or V
olum
e (m
m3 )
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Immunological Memory Induced by STING Agonist ADC
220 7 14 21 28
0
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1600Non-targeted tumor
Days post re-challenge
Mea
n Tu
mor
Vol
ume
(mm
3 )±SE
M UntreatedControls
6/6Tumors
• Tumor free mice re-implanted with:• Original targeted tumor on the opposite flank
(blue), and• Non-targeted tumor on the other flank (red).
• Untreated age matched mice also implanted as a control (black line).
Efficacy Study Rechallenge Study (Dual Flank)
0 7 14 21 280
50
100
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250
Targeted tumor
Days post re-challenge
Mea
n Tu
mor
Vol
ume
(mm
3 )±SE
M
UntreatedControls
6/6Tumor-free
Dose: mAb/ payload mg/kg)
0 7 14 21 28 35 42 490
500
1000
1500
2000
Targeted ADC (0.88 / 0.04 mg/kg)
Days on Study
Tum
or V
olum
e (m
m3 )
6/9 Tumor-free
Re-challenge
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Conclusions
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1. STING agonist ADC platform• Novel agonist payload optimized for ADC
• Linker & scaffold designed to maximize therapeutic index
• Well-tolerated in non-human primates
2. In vivo activity in multiple targets, tumor models and mouse strains
3. Differentiation from IV agonist: activity and tolerability
4. Immunological memory
5. On track to nominate 1st Development Candidate in 2020
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Mersana’s STING ADC Research Team
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Discovery ChemistryJeremy DuvallJosh ThomasKeith BentleyBrian JonesEoin KelleherLiping YangRadha IyengarDorin Toader
BiologyRaghida Bukhalid Naniye CetinbasChen-Ni ChinScott CollinsTimothy EitasWinnie LeeTravis MonnellMarina ProtopopovaLiuLiang Qin Kelly SlocumMarc Damelin
Analytical & BioanalyticalKenneth AvocetienStephen BradleyTyler CarterSusan ClardyMark NazzaroElena Ter-OvanseyanLing XuJeffrey ZuritaDavid Lee
Translational MedicinePamela ShawRebecca Mosher
Chief Science & Technology OfficerTimothy B. Lowinger
BioconjugationKalli CatcottBingfan DuCheri StevensonAlex UttardAnouk DirksenDorin Toader