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BT5528, an EphA2-targeting Bicycle® Toxin Conjugate (BTC): Profound efficacy without bleeding and coagulation abnormalities in animal models
Gavin BennettAACR Annual Meeting 2019 Atlanta 4481
Highly constrained: high affinity, exquisite selectivity, excellent stability
Large binding footprint: disrupt protein-protein interactions
Fully synthetic: NCE classification and synthetic control
Highly flexible modality: modular building blocks retain pharmacology
Adjustable PK: excellent tissue penetration, renal elimination, tuneable T1/2
COOH
X
NH2
Linear peptide
NH2 COOH
Bicycle
Chemical modification with scaffold
Bicycles®: a new therapeutic modality
Loop 1
Loop 2
Scaffold
Bicycle AACR 2019 #44812
EphA2: Biological rationale• Erythropoietin-producing hepatocellular A2 receptor: member of
Eph subfamily of receptor tyrosine kinases
• Regulates cell migration, adhesion proliferation and differentiation
• Overexpression in human cancers, correlates with tumourprogression
• Key area for pharma companies, multiple programs in discovery, and clinical stages but…
• Development of MEDI-547 (MedImmune) in ovarian cancer was halted following on target bleeding events in phase I.
“The bleeding and coagulation events observed in humans showed similarities to those evident in rats and monkeys. In all three species, increased activated partial thromboplastin time, increased fibrinogen/fibrin degradation product, and increased fibrin D-dimer were reported. Monkeys had red/ blood discharge from the nose, mouth, gums.”
Benign Breast
Invasive ductal carcinoma
% s
amp
les
/ ca
teg
ory
Benign Breast Breast carcinoma0
20
40
60
80
100negativeweakmoderatestrong
Bicycle AACR 2019 #44813
BT5528: structure & profile
BT5528(1μM)
BT5528 affinity Human Mouse Rat NHP
FP comp (Ki, nM)1.9 ± 0.9
n=295.2 ± 1.9
n=161.9 ± 1.3
n=10
SPR (KD, nM) 0.9 ± 0.4 n=2
2.0 ± 0.8 n=2
2.7 ± 0.4 n=2
1.0n=1
Cell binding by HCS (Kb app, nM) 14.8 ± 10.5
Ligand-binding domain
%identity to hEphA2
Binding affinity (SPR, using BT5528, KD nM)
Human HumanEphA1 54 > @ 5uMEphA2 100 0.9EphA3 58 > @ 5uMEphA4 55 > @ 5uMEphA5 56 > @ 25uMEphA6 56 > @ 20uMEphA7 56 > @ 20uMEphB1 49EphB4 39 > @ 20uM
High affinity binding to EphA2 protein across species & on cells. Species cross-reactivity, high selectivity.
Bicycle AACR 2019 #44814
0 12 24 36 481
10
100
1000
Time after dosing (hr)
Anal
yte
(pm
ol/g
) Plasma MMAEPlasma BT5528
0 12 24 36 481
10
100
1000
Time after dosing (hr)
Anal
yte
(pm
ol/g
)
Tumour MMAEPlasma MMAEPlasma BT5528
PC3 tumour xenograft• High EphA2
Single dose of BT5528
• Produces high MMAE concentrations in tumour
• Stable from 2h to >48h
• Transient exposure of both BT5528 & MMAE in plasma
BT5528 PK Parameters Mouse Rat NHP
Cmax (ng/mL) 6321 4048 7643T1/2 (h) 0.4 0.3 ~0.6hVdss (L/kg) 0.18 0.33 0.21Cl (mL/min/kg) 6.2 15.5 4.9
AUC0-last (ng.h/mL) 2643 998 3516
Bicycle AACR 2019 #4481
BT5528 delivers MMAE to tumour
5
BT5528 induces mitotic arrest in tumour
PC3 tumour xenograft• High EphA2
24h1h 48h
0 12 24 36 480
5
10
15
20
25
Time after dosing (hr)
% p
HH3+
nuc
lei
Tumour pHH3
Single dose of BT5528
• Produces high MMAE concentrations in tumour
• Stable from 2h to >48h
• Transient exposure of both BT5528 & MMAE in plasma
• Induces mitotic arrest
• Measurable by pHH3 IHC within 24h
Bicycle AACR 2019 #44816
BT5528 produces tumour regression
0 7 14 210
100
200
300
400
500
Time after start of dosing (days)
Tum
our
Volu
me
(%D
0)
Vehicle i.v qwBT5528 0.5mg/kg
^ ^ ^
Weekly dosing of BT5528
• Produces high MMAE concentrations in tumour
• Stable from 2h to >48h
• Transient exposure of both BT5528 & MMAE in plasma
• Induces mitotic arrest
• Measurable by pHH3 IHC within 24h
• Induces tumour cell death
• Measurable regression by day 4
PC3 tumour xenograft• High EphA2
Bicycle AACR 2019 #44817
• BT5528 shows target-dependent efficacy
• Significant regression in a wide range of EphA2-positive tumours
• BT5528 shows equivalent efficacy with a wide range of dosing paradigms
• Bolus, 1h infusion, 24h infusion
• BT5528 efficacious with intermittent dosing
• Efficacy also shown dosing every 2 weeks
BT5528 efficacy: target-mediated, flexible dosing
0 7 14 210
500
1000
1500
2000
2500
Time after start of dosing (days)
Tum
or V
olum
e (m
m3)
VehicleBT5528 1mg/kg (bolus)BT5528 1mg/kg (1h infusion)BT5528 1mg/kg (24h infusion)
^ ^ ^
0 20000 40000 600000
50
150
200400
800
Lu-01-0486
SK-OV-3
NCI-N87
OE-21
LU-01-0251PC-3
MOLP-8
NCI-H1975NCI-H1975
MDA-MB-231
HT-1080HT-1080
Lu-01-0412
Target expression (by FACS, binding sites/ cell)
Tum
our v
olum
e(%
of b
asel
ine,
min
imum
, D14
-28)
Equilibrium
Tumour Regression
Complete Tumour Regression
Tumour Growth
EphA2 expression
Effic
acy
Cmax(ng/mL)
AUC (ng.h/mL)
3120 13251120 132555 1325
Bicycle AACR 2019 #44818
BT5528: differentiation from ADC in complex PDX models
0 7 14 210
1000
2000
3000
4000
^ ^ ^^
Vehicle i.v qwBT5528 3mg/kgADC 3mg/kg
Time after start of dosing (days)
Tum
our V
olum
e (m
m3 )
Bicycle distribution at 60 min
ADC distribution at 60 min
0 7 14 21 28 35 420
1000
2000
3000
4000Vehicle, qwBT5528 3mg/kgADC 3mg/kg
Time after start of dosing (days)
Tum
our V
olum
e (m
m3 )
^ ^ ^ ^ ^ ^
Moderate EphA2 expression
High EphA2 expression
Bicycle AACR 2019 #44819
BT5528: differentiation from ADC in bleeding/ coagulation & liver toxicology
Findings from BT5528 toxicology study
Treatment related adverse events # events (% of patients) n of total
ALT increased 3 (50) 3/6
Haemorrhage 6 (83.3) 5/6 Bleeding observed on days 3-8 following a single dose of MEDI-547
Findings from MEDI-547 Phase I study
• No bleeding events seen in either species• Dosing to toxin equivalent doses >100x dose of MEDI-547 used in patients
• No significant effect on clotting parameters• No evidence of abnormal liver function
Vehicl
e
BT5528
low dose
BT5528
high dose0
5000
10000
15000
D-d
imer
(ng/
ml)
Vehicl
e
BT5528
low dose
BT5528
high dose0
10
20
30
APT
T (s
)Veh
icle
BT5528
low dose
BT5528
high dose0
20
40
60
80
ALT
(U/L
)
Vehicl
e
BT5528
low dose
BT5528
high dose0
20
40
60
80
100
AST
(U/L
)
Bicycle AACR 2019 #448110
BT5528: a Bicycle Toxin Conjugate targeting EphA2 for the Treatment of Solid Tumours• EphA2 is highly expressed on tumour cell surface in a wide range of solid tumours
• BT5528 was developed as a BTC to target EphA2• High affinity binding• Short half-life and renal elimination• “Hit and run” delivery of toxin, minimising systemic exposure
• BT5528 shows excellent efficacy in a wide range of tumour models• Efficacy correlates with EphA2 expression
• BT5528 shows clear differentiation from previous ADC• Efficacy maintained even in large, heterogeneous PDX• No bleeding/ coagulation toxicity seen
• IND enabling studies ongoing
Bicycle AACR 2019 #448111
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