an egfr targeting probodytm t cell bispecific induces tumor regressions while … · 2017. 12....
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© 2017 CytomX Therapeutics, Inc.
An EGFR Targeting ProbodyTM T cell Bispecific
Induces Tumor Regressions While Reducing On-target
Toxicities in Preclinical Studies
Leila Boustany, Ph.D.
Sr. Scientist1
PROBODY is a trademark of CytomX Therapeutics, Inc.
Antibody Engineering and Therapeutics
12/14/17
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• Bring cytotoxic T cells and cancer cells together
• Highly potent, but toxic modality
• Challenging to use for solid tumors: unforgiving for target expression on normal tissue
• Poor exposure
T-cell Engaging
Bispecific
Antibodies
• Potent anti-tumor activity
• Less systemic toxicity by avoiding T cell engagement outside of tumor
• Better exposure
• Expanded utility, especially for solid tumor targets
Potential
advantages of
T-cell Engaging
Probody
Bispecific
Therapeutics
T-Cell Engaging
Bispecifics
Target Cell
T Cell
Nature Biotechnology 23, 1065 - 1072 (2005)
T Cell Engaging Bispecific (TCB) Therapeutics:
Highly Potent, but Associated with Safety Liabilities
2
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Probody Therapeutics are Antibody Prodrugs Designed
to be Activated in the Tumor Microenvironment
3
ANTI-CANCER
ANTIBODY
CLEAVABLE LINKER
MASKING PEPTIDE
PROTEASES
HEALTHY TISSUE TUMOR TISSUE
Probody Therapeutics:
• “Masked” to limit binding to normal tissue
• “Un-masked” by tumor-associated
proteases
• Linkers designed to be cleaved by
multiple proteases for utility across tumor
types
• Validated targets:
➢ Improve therapeutic window
• Difficult to drug targets:
➢ Create therapeutic window
• Applicable to all immunoglobulin formats
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Normal Colon Primary Colon Cancer Metastatic Colon Cancer
IMAGING OF ACTIVE PROTEASE2
Activated Proteases are Prevalent in Tumors
But Not in Healthy Tissues
• Upregulated protease
activity is a hallmark of all
cancers
• Protease activity is tightly
controlled in healthy tissues
4
1. Sevenich, et. Al. Gene & Dev., 2014; 2. Matriptase: LeBeau, et al., PNAS 2012
PRIMARY TUMOR METASTASIS1
ANGIOGENESIS
INFLAMMATION
INTRAVASATIONINVASION
PROLIFERATION
AND SURVIVAL
EXTRAVASATION
COLONIZATION
AND OUTGROWTH
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Preclinical Proof of Concept Achieved for Multiple
Antibody Modalities & Targets
5
Antibody
Drug Conjugates
T-Cell
Bispecifics
(TCBs)
CARs
Immune
Modulators/
Checkpoint
Inhibitors
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EGFR as a Target for Probody TCB Modality
• Prevalent EGFR expression
– EGFR Probody TCB expected to be potent against both high and low
expressing cancers
• Expression in immunogenic indications
– Opportunity to combine with IO agents
• Unlock EGFR potential
– M.O.A. does not rely on EGFR signaling blockade
– Less concern with acquired resistance, e.g., activating mutations in NSCLC,
KRAS/BRAF mutations in CRC
6
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CytomX Probody T Cell-engaging Bispecific (Pb-TCB)
• Full IgG bispecific format to maximize half-life, improve expression
• Fc-effector impaired to minimize cross-linking by FcR-bearing cells
• Format optimized for a-CD3 affinity, mask strength and cleavable substrates
a-EGFR
a-CD3
a-EGFR
a-CD3
Activated Bispecific (act-TCB)
masks
Protease
substrate
Fc effector
mutant
Probody Bispecific (Pb-TCB)
Cleavage by tumor
associated proteases
7
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1 0 -3 1 0 -2 1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4
0
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
C D 3 B in d in g (J u rk a t)
[A c t/P b -T C B ] n M
MF
I (c
orre
cte
d)
P b -T C B
a c t-T C B
1 0 -3 1 0 -2 1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4
0
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
3 0 0 0 0
3 5 0 0 0
4 0 0 0 0
E G F R B in d in g (H T 2 9 )
[A c t/P b -T C B ] n M
MF
I (c
orre
cte
d)
P b -T C B
a c t-T C B
Pb-TCB Demonstrates Reduced Antigen Binding in vitro
8
Masking reduces binding to EGFR and CD3 on cells
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Pb-TCB Attenuates Cytotoxicity and T cell Activation in vitro
9
1 0 -4 1 0 -3 1 0 -2 1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 5 1 0 6
0
2 0
4 0
6 0
8 0
1 0 0
H T 2 9 C y to to x ic ity
[A c t/P b -T C B ] p M%
Cy
to
to
xic
ity
P b -T C B
n o n E G F R b in d in g P b -T C B
a c t-T C B
• Pb-TCB protects >5 orders of magnitude in vitro
• High target density not required for potent cytotoxicity
• Masking shifts T cell activation curve
1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 5 1 0 6 1 0 7
0
2 0
4 0
6 0
8 0
C D 8 T c e ll A c t iv a t io n
[A c t/P b -T C B ] p M
CD
69
(%
po
sit
ive
)
P b -T C B
a c t-T C B
UT
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10
20X mag
NSUB* Pb-TCB2Pb-TCB1 Act-TCB
Increasing Pb-TCB Protease Sensitivity Enhances Tumor
T cell Infiltration and Efficacy
PBS
T cell infiltration 7 days after 1 mpk dose
• Tumor T cell infiltration is associated with efficacy
• More TILs observed in tumors treated with
Pb-TCB2
Weekly dosing
0.3 mpk
(Brown staining is CD3+ cells)
(Substrate Cleavability: Pb-TCB2> Pb-TCB1> NSUB*)
*NSUB is a Pb-TCB devoid of a cleavable substrate0 5 1 0 1 5 2 0
0
2 0 0
4 0 0
6 0 0
H T 2 9 X e n o g ra f t
S tu d y D ay
Tu
mo
r V
olu
me
(m
m3)
N S U B *
P b -T C B 2
P B S
a c t- T C B
P b -T C B 1
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EGFR-CD3 Pb-TCB Regresses Established Tumors In
KRAS or BRAF Mutated Xenograft Models
Human PBMCs engrafted into HT29 and HCT116 Tumor-bearing NSG mice
HT29 Xenograft HCT116 Xenograft
11
Dosed weekly: days 1, 8, 15
0 5 1 0 1 5 2 0 2 5
0
2 0 0
4 0 0
6 0 0
8 0 0
S tu d y D a y
Tu
mo
r V
olu
me
(m
m3
+ S
EM
)
P B S
P b -T C B 1 .5 m p k
P b -T C B 0 .5 m p k
0 5 1 0 1 5 2 0 2 5
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
1 2 0 0
S tu d y D ay
Tu
mo
r V
olu
me
(m
m3
+ S
EM
)
P b -T C B , 0 .3 m p k
P b -T C B , 1 m p k
P B S
a c t-T C B , 0 .3 m p k
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EGFR-CD3 Pb-TCB Protects against Acute Toxicities and
Increases MTD in Non-Human Primates
12
• Observations at MTD include transient, mild to moderate T cell-mediated toxicities
• Pb-TCB is well tolerated in cynomolgus monkeys up to MTD of 4 mg/kg
• Masking enables >60 fold increase in MTD relative to the unmasked TCB
IL-6 @ 8 hrs IFNg @ 8 hrs T cell Proliferation @ 72 hrs AST @ 48 hrs
0 .0 1 0 .1 1 1 0
0
1 0 0 0 0 0
2 0 0 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
D o s e (m g /k g )
pg
/m
l
a c t-T C B
P b -T C B
0 .0 1 0 .1 1 1 0
0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
D o s e (m g /k g )
pg
/m
l
0 .0 1 0 .1 1 1 0
0
2 0
4 0
6 0
8 0
D o s e (m g /k g )
% K
i-6
7+
CD
4+
0 .0 1 0 .1 1 1 0
0
2 0 0
4 0 0
6 0 0
8 0 0
D o s e (m g /k g )
U/L
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Observed Cyno Activity is Largely Dependent on EGFR Binding
EGFR-Independent Activity of the Pb-TCB is Undetectable in Cynos at 2 mg/kg
13
Pre
do
se
1 h
r
4 h
r
8 h
r
24 h
r
0
2 0 0
4 0 0
6 0 0
8 0 0
1 0 0 0
IL -6
IL-6
(p
g/m
L)
Pre
do
se
72 h
r
7 d
ays
0
2 0
4 0
6 0
8 0
1 0 0
T c e ll a c tiv a tio n
% P
D-1
+C
D4
+
n o n E G F R b in d in g P b -T C B
P b -T C B
Pre
Day 3
Day 8
0 .0
0 .2
0 .4
0 .6
T o ta l B ili
mg
/dL
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EGFR-CD3 Pb-TCB Extends PK in Non-Human Primates
14
Masking markedly extends PK of the Pb-TCB relative to the unmasked TCB
0 2 4 4 8 7 2 9 6 1 2 0 1 4 4 1 6 8 1 9 2
0 .0 1
0 .1
1
1 0
1 0 0
1 0 0 0
P la s m a C o n c e n tra tio n
H o u rs P o s t-D o s e
nM
a c t-T C B , 0 .1 8 m p k
a c t-T C B , 0 .0 6 m p k
P b -T C B , 2 m p k
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EGFR-CD3 Pb-TCB Preclinical Summary
• Efficacy: Potent anti-tumor activity despite strong masking
– Greatly attenuates target binding and T cell mediated cytotoxicity in vitro
– Is highly effective in vivo, regressing established tumors in KRAS and BRAF
mutant xenograft models
• Safety: Increased tolerability in cynos despite much higher
exposure
– Probody TCB MTD is >60 times that of the corresponding unmasked TCB
– Tolerated Probody TCB serum concentration is significantly greater than that of
the unmasked TCB
15
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Acknowledgements
16
Laurie Wong Hong Lu
Clayton White Shouchun Liu
Linnea Diep Jennifer Richardson
Yuanhui Huang Bryan Irving
Sherry La Porte Michael Kavanaugh