BT5528, an EphA2-targeting Bicycle® Toxin …...BT5528, an EphA2-targeting Bicycle® Toxin...

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


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.


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


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


BT5528 delivers MMAE to tumour

5

BT5528 induces mitotic arrest in tumour


24h1h 48h

0 12 24 36 480

5

10

15

20

25


% p

HH3+

nuc

lei

Tumour pHH3

Single dose of BT5528




• Induces mitotic arrest

• Measurable by pHH3 IHC within 24h


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




• Induces mitotic arrest

• Measurable by pHH3 IHC within 24h

• Induces tumour cell death

• Measurable regression by day 4



• 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


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


BT5528: differentiation from ADC in complex PDX models

0 7 14 210

1000

2000

3000

4000

^ ^ ^^

Vehicle i.v qwBT5528 3mg/kgADC 3mg/kg


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


Tum

our V

olum

e (m

m3 )

^ ^ ^ ^ ^ ^

Moderate EphA2 expression

High EphA2 expression


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

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80

ALT

(U/L

)

Vehicl

e

BT5528

low dose

BT5528

high dose0

20

40

60

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100

AST

(U/L

)


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


BT5528, an EphA2-targeting Bicycle® Toxin …...BT5528, an EphA2-targeting Bicycle® Toxin...

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