Download Antibody Drug Conjugates

Antibody Drug Conjugates
Dr Philip W. Howard
Head of Targeted Therapeutics
Spirogen
Therapeutic Antibodies
• Many tumours express antigens that can be targeted by
antibodies
• These antibodies offer the prospect of selectively targeting
tumour cells
Key Characteristics of an ADC
Linker
Stable in in vivo circulation
Cleaved inside target cell
Stable upon storage
Antibody
Drug
High Tumour Specificity
High Potency
High Avidity
Linkable
High Antigen Expression
Water Soluble
Antigen and Antibody Requirements
for ADC
• Antigen
– tumour specific or overexpressed on tumour cells
vs. normal tissue
– antigen should be highly expressed on surface of
tumour cells
• Antibody
– affinity of the antibody for the target antigen
should not be compromised by forming an ADC
– The antigen-ADC complex must be internalized
Targeting Members of the Her Receptor
Family
Figure 15.38b The Biology of Cancer (© Garland Science 2007)
Myeloid and haematopoietic
Targets A + - *: #6@'J @'5/
From Teicher (2009) Curr Can Drug Targ 9:982
•At least 16 current targets on
non-solid cancer cells
•Epitopes are important
•Not all internalise at the same rate
IL2Ra
Epitopes are important
Not all internalize at the same rate
Fc!R1
NCAM
From Teicher (2009) Curr Can Drug Targ 9:982
A + - *: #6@'J @'5/
Targets – solid tumours
From Teicher (2009) Curr Can Drug Targ 9:982
LeY
MUC1
CA125
HER2
NCAM
Bi-specific targeting vehicles
may reduce toxicity in normal
•At least
19expressing
current only
targets
tissue
one on
of the
solid tumours
plus
some targets
two surface
antigens
not found directly on tumours
Syndecan
Endoglin
From Teicher (2009) Curr Can Drug Targ 9:982
Stromal Target
Stromal Target
Some Approved Therapeutic
Antibodies For Oncology
Antibody
Brand Name
Approv
Date
Target
Mechanism
Indication
Market ($B)
Bevacizumab
Avastin
2004
VEGF
Ligand depletion
Denosumab
Prolia; Xgeva
2010
Rank ligand
Ligand depletion
Colorectal Ca
Bone Mets
(SRE)
Ipilumumab
Yervoy
2011
CTLA-4
T-Cell upregulation
Melanoma
Alemtuzumab
Campath
2001
CD52
ADCC ± CMC
Cetuximab
Erbitux
2004
EGFr
↓EGFr signaling
CLL
Colorectal; H
& Neck Ca
3.2 (2010)
Panitumumab
2006
EGFr
↓EGFr signaling
Colorectal Ca
0.23 (2009)
Rituximab
Vectibix
Rituxin;
MabThera
1997
CD20
ADCC ± CMC
NHL; RA
6.7 (2010)
Ofatumumab
Arzerra
2009
CD20
ADCC ± CMC
CLL
Ibritumomab
Zevalin
2002
CD20
90Y-RIT
NHL
Tositumomab
Bexxar
2003
CD20
131I-RIT
NHL
HER2
↓HER2 signaling;
ADCC
Breast Ca
Trastuzumab
Herceptin
1998
6.8 (2010)
0.1 (2008)
5.5 (2010)
Do we Need ADCs?
• Unfortunately, many therapeutic antibodies
lack in vivo efficacy even when combined with
established chemotherapeutic agents.
• Even in the case of successful agents such as
Herceptin, patients relapse and the tumours
become resistant.
• Fortunately, the resistance mechanism does
not affect surface expression of Her2
Antibody Modification to Enable
Conjugation
• Reduce native disulphide
bonds and conjugate to
maleimide linker
• Functionalize lysines with
thiol containing chains
and conjugate to
maleimide linker
• Conjugate to lysines with
a succinimide linker
• Engineer new thiols at
specific positions and
conjugate to maleimide
linkers.
Conjugation to Thiols
ADC-drugs linked to
reduced inter-chain
cysteines
Non homogenous drug
load (DAR = 0-8)
Drug linked to single
engineered cysteine
Homogenous drug
load (DAR=2)
• Using engineered thiols reduces Drug Antibody Ratio
• Not a problem with potent warheads
• Too many warheads can cause aggregation and loss of specificity
Conjugation Chemistries
Maleimide Approach
Iodoacetamide Approach
Characterization DAR Determination
Hydrophobic Interaction Chromatography (HIC)
Aditya Wakankar et al, mAbs, 2011; 3;2: 164-175
Does not work for all Spirogen ADCs
Characterization DAR Determination
LC/ESI-TOF MS
Alexandru C. Lazar et al, Rapid Commun. Mass Spectrom. 2005; 19: 1806-1814
Linkers: Stability and Cleavage
• Linkers must be stable in circulation
• But readily cleaved inside the target cell
LINKER
RELEASE MECHANISM
HALF LIFE
(MOUSE SERUM)
HYDRAZONE
Designed for degradation in acidic compartments within the
cell
2 days
PEPTIDE Val-Cit
Designed for serum stability and to be enzymatically
hydrolysed ((esp. by lysosomal proteases such as cathepsin B)
30 days
PEPTIDE (Phe Lys)
Designed for serum stability and to be enzymatically
hydrolysed ((esp. by lysosomal proteases such as cathepsin B)
12days
DISULPHIDE (Non
hindered)
Designed to be cleaved through dislulfide exchange with an
intracellular thiol, such as glutathione
2 days
DISULPHIDE (Hindered)
Designed to be cleaved through disulphide exchange with an
intracellular thiol, such as glutathione
5 days
THIOETHER
Non-reducible and stable to proteolytic degradation
7 days
Mylotarg
Acute Myeloid Leukaemia
• Voluntarily withdrawn after follow-up trial:
• No survival benefit in controlled study
• Increased mortality and toxicity (myelosuppression)
• Premature release, hydrazone linker?
Trastuzumab DM1
Genentech/Immunogen
Cleavable Disulphide Linker
• Endocytic cleavage of disulphide very inefficient
• Disulphide designed to cleave under reducing conditions
• Endocytic pathway now thought to be oxidizing
• Disulphide linker unstable in circulation
• Only 11% of disulphide remaining after 7 days
Trastuzumab MCC-DM1
• MCC linker was found to be significantly more robust than the
disulphide linker
– Negligible loss of MCC-DM1 in serum after 7 days
• The MCC linker is an example of a non-cleavable linker
– The antibody is degraded by proteases leaving the drug-linker intact
• But Maytansinoid-linker molecule still active and potent
Trastuzumab MCC-DM1
Her2 Positive Breast Cancer
• Phase I
– 24 patients (median 4 prior chemotherapeutic agents)
– 73% clinical benefit rate (OR + Stable disease at 6 months)
• Phase II (Burris et al.)
– 108 patients; Her2 +ve metastatic breast cancer all received
trastuzumab
– 26% overall response rate (after 12 months)
– 4.6 months overall median progression free survival
• Phase II (TDM4450g)
– Previously untreated patients with Her2 +ve metastatic or
advanced breast cancer
– Treated patients benefited from an extra 5 months of life
compared to those treated with Herceptin + chemotherapy
Adcetris (Brentuximab)
Seattle Genetics
• Robust protease labile linker with self-immolative
spacer
Adcetris (Brentuximab)
• Adcetris brentuximab velodotin CD30 Hodgkin lymphoma data
(102 patients)
• 32% CR (duration of response 20.5 months)
–
CR= Disappearance of all evidence of disease
• 40% PR (duration of response 3.5 months)
–
PR = Regression of measurable disease and no new sites
• 73% ORR (duration of response 6.7 months)
– ORR of 30% considered a meaningful response (FDA Seattle genetics
discussions)
Approved by FDA
The ADC Field is Dependent on a
Narrow Range of Warheads
• Calicheamycin
– DNA cutting agent
– Narrow therapeutic window (1-0.1 nM)
• Maytansinoids
– Potent (picomolar)
– Tubulin binder
– PGP substrate
• Auristatin
– Potent (nanomolar – 10 pM)
– Tubulin binder
– PGP substrate
• Doxorubicin
– Insufficient potency ( M)
Name
Mylotarg
(Gemtuzumab
ozogamicin)
Ab Target
Drug
Linker
Indication
Current Phase
MA 2000
Withdrawn 2010
CD33
Calicheamicin
Hydrazone
Acute Myeloid Leukaemia
CD30
Auristatin E
Valine-citruline
Relapsed/refractory HL ALCL Approved
Post-transplant HL
August 2011
Her2
Maytansinoid
DM1
Thioether
Metastatic breast
CD22
Calicheamicin
Hydrazone
CD56
Maytansinoid
DM1
Disulphide
CD74
Doxorubicin
Thioether
GPNMB
Auristatin E
Valine-citruline
SAR-3419
CD19
Maytansinoid
DM4
SGN-75
CD70
Auristatin F
Hindered
disulphide
Maleimidocaproyl
Breast
melanoma
Relapsed/refractory
NHL
Relapsed/refractory NHL,
Renal carcinoma
IMGN-388
αv-integrin
Thioether
Solid tumours
I
MDX-1203
CD70
Valine-citruline
NHL, renal
I
MN-IC
CA9
Solid tumours
I
BIIB-015
Cripto
Hindered disulphide
Breast
I
BT-062
CD138
Hindered disulphide
Multiple myeloma
I
BAY-79-4620
MN carbonic
anhydride IX
Auristatin E
Valine-citruline
Solid tumours
I
AGS-16M8F
AGS-16
Auristatin F
Maleimidocaproyl
Renal
I
SGN-35
Brentuximab vedotin
Trastuzumab-DM1
Trastuzumab-emtansine
CMC-544
Inotuzumab ozogamicin
IMGN-901
Lorvotuzumab
mertansine
Milatuzumabdoxorubicin
CDX-011
Glembatumumab veditin
Maytansinoid
DM4
Duocarmycin
MED 2460
Auristatin
Maytansinoid
DM4
Maytansinoid
DM4
Relapsed/refractory
NHL
Multiple myeloma Solid
tumours: SCLC,
Merkel cell, ovarian
Multiple myeloma
III
III
II
II
II
II
I
Pyrrolobenzodiazepines (PBDs)
9
8
10
11
11a
N
H
A
B
7
1
N C
6
O
3
2
Naturally Occurring PBDs
OH
Me
H
OMe H
N
OMe
H
N
N
N
NH2
O
N
N
H
O
Tomaymycin
Prothracarcin
OH
N
Me
H
N
MeO
O
DC-81
H
N
O
HO
O
Porothramycin
N
MeO
NMe2
O
O
Anthramycin
HO
OMe
H
H
N
O
Me
Me
MeHN
O
O
HO
OH
H
N
Sibiromycin
OH
Mode of Action
PBDs form a covalent, aminal linkage with the N2 of guanine
in the minor groove of DNA
O
N
HN
H N
..
2
2
O
N
N
DN A
N
R'
A
H
N
R'
N C
R"
N
O
N
DN A
H
B
O
H
N
H
N
11
N
HN
R"
PBD Dimers (In Vitro Activity)
Molecule
(Control)
L428
786-O
HEL
HL-60
MCF-7
SG2057
0.001
0.001
0.000017
0.000035
0.021
SG2202
<0.0001
<0.0001
<0.0001
<0.0001
0.000016
MMAE
0.288
1.397
1.268
0.162
0.700
In Vivo Dimer Activity
SG2000
15
Solvent Control
Cisplatin 4mg/kg (i.v.; days 0,4,8)
10
SJG136 0.2mg/kg (i.v.; days 0,4,8)
5
Mean Relative Tumour
Volume
CH1:CisR
0
SG2000
20
Solvent Control
Cisplatin 4mg/kg (i.v.; days 0,4,8)
SJG136 0.2mg/kg (i.v.; days 0,4,8)
10
0
0
10
20
30
40
50
0
10
Day
20
30
40
50
Day
SG2285, LOXIMVI 3 mg/kg
SG2057, 0.075 mg/Kg
200
Mean RTV
Mean Relative Tumour
Volume
CH1
Solvent
SG 2285
150
100
50
0
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Time (days)
DNA Cross-Link – Comparison to Other
Agents
Cisplatin
SJG-136
Yondelis
SG2000 Clinical Trial Status
• Phase I Trials Complete
• SG2000 is in Phase II clinical
trials at four centres in the
U.S.A. for the treatment of
cisplatin refractory ovarian
cancer.
• A Phase II leukaemia trial is
in preparation in the UK for
Q1 2012
New PBD ADC Warheads
Compound
IC50 (pM)
X
IC50 (pM)
Y
SG-3202
4.1
3.3
SG-3192
6.4
11.4
SG-3198
9.3
7.3
SG-2963
16.1
18.5
SG-2219
10.1
27.3
SG-2962
16.4
18.5
Linking to Antibodies
Maleimide
Succinimide etc.
For Thiols, Amines
and Phenols
Self-immolative Moiety.
PAB, cinnamyl or cyclizing
Enzyme labile
Trigger.
Emphasis on
avoiding
lipophilic or
reactive groups
PBD-ADC Xenograft
Standard ADC
10 mg/Kg
PBD-ADC
1mg/Kg
Key Advantages of PBDs as ADC
Warheads
•
•
•
•
Potency in picomolar range
Alternative Mode of Action
Non-Distortive of DNA
Proven as mono-therapies in oncology
– Demonstrable Therapeutic index
•
•
•
•
Robust and scalable synthesis
Modulation of solubility
Compatible with multiple linker system chemistries
Broad intellectual property protection
Confidential
Summary
• Antigen
– Tumour specific and highly expressed
• Antibody
– Humanized
– Must be internalized
– Engineered thiols groups
• Linker
– Must be robust (i.e. Val-Cit or MCC or one of your own devising!)
• Warhead
– As potent as possible
• Conjugation
– Reproducible DAR (2-4)
• Characterisation
– Access to ESI-TOF or HIC instrumentation
Acknowledgements
•
•
•
•
•
Prof. John Hartley
Dr Mahendra Deonarian
Dr John Adair
Dr Christina von Bulow
Marina Folarin