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Trastuzumab-Dolaflexin, a Highly Potent Fleximer-Based Antibody-Drug Conjugate, Demonstrates
a Favorable Therapeutic Index in Exploratory Toxicology Studies in Multiple Species
Natalya Bodyak, Alex Yurkovetskiy, Peter U. Park, Dmitry R. Gumerov, Michael DeVit, Mao Yin, Joshua D. Thomas, LiuLiang Qin, Timothy B. Lowinger, Donald A. Bergstrom
Mersana Therapeutics Inc., 840 Memorial Drive, Cambridge, MA 02139
232 µg/m2
600
696 µg/m2
T-dolaflexin 2.68 mg/kg
Range of T-DM1 values*
1392 µg/m2
4 females/dose cohort
Dosing Day 1; Day 3 terminal necropsy (N=2);
Day 22 recovery necropsy (N=2)
Trastuzumab-dolaflexin 0.67 mg/kg
• T-dolaflexin has excellent PK and is well tolerated (MTD > 30
mg/kg) in mouse
-2X
GGT
6 mg/kg
T-dolaflexin 1.34 mg/kg
0X
Bilirubin
3 mg/kg
T-dolaflexin 0.67 mg/kg
+2X
ALT
30 mg/kg
6120 µg/m 2
• T-dolaflexin is efficacious at a single dose of 0.67 mg/kg in JIMT1 (HER2 2+) model that is insensitive to ado-trastuzumab
emtansine while three weekly doses lead to tumor free survivors
+4X
ALP
10 mg/kg
2040 µg/m2
ADCETRIS NHP TOX
(BLA REVIEW)
• T-dolaflexin achieved a therapeutic index >40 in mouse
* Range of clinical pathology values
reported on Day 3 for 3, 10 and 30 mg/kg
T-DM1 doses (Poon et al., 2013)
400
0
10
20
30
40
50
60
70
Days Post Dose
1200
Mean tumor volume (mm3)
3 mg/kg
612 µg/m2
Discussion and Conclusions
+8X
AST
1 mg/kg
Trastuzumab-dolaflexin 2 mg/kg
Dolaflexin ADC Structure and Drug Release
Day 3 Clinical Pathology Comparable to T-DM1
TRASTUZUMABDOLAFLEXIN
NHP TOX
Neutrophils
800
0
Pharmacokinetics of T-dolaflexin in the range of dose level tested was linear,
with excelent conjugated drug stability and minimal exposure to free payload.
Exposure based TI observed in cynomolgus monkey was calculated as 3.
2400 µg/m 2
Lymphocytes
Kadcyla 20 mg/kg
200
There was no evidence of myelosuppression. Microscopic pathology findings
were limited, with no test-article related findings in HER2-expressing organs
including heart, lungs and GI tract. All doses were considered well-tolerated.
2.68 mg/kg
1200 µg/m 2
KADCYLA NHP TOX
(POON 2013)
Vehicle
Endpoint
1000
1.4
1.2
1
0.8
0.6
0.4
0.2
0
600
2
0.5
T-dolaflexin
2.68 mg/kg
8
15
0
-6
22
Trastuzumab-dolaflexin 0.67 mg/kg qwk x 3
Trastuzumab-dolaflexin 2 mg/kg qd x 1
0
0
10
20
30
40
50
8
15
22
T-dolaflexin
2.68 mg/kg
(N=1)
1
15
GGT
1
8
15
22
Liver function
labs
4
T-dolaflexin
0.67 mg/kg
3
Bilirubin
T-dolaflexin
1.34 mg/kg
10
T-dolaflexin
1.34 mg/kg
2
Albumin
5
T-dolaflexin
2.68 mg/kg
(N=1)
0
8
AST
15
T-dolaflexin
2.68 mg/kg
1
ALT
T-dolaflexin
0.67 mg/kg
0
-6
Liver injury
labs transaminases
-6
20
2
Reversible liver injury in one animal
at 2.68 mg/kg dose
AST
3
0.5
60
1
absolute neutrophil count
1.5
200
T-dolaflexin
1.34 mg/kg
1
T-dolaflexin
1.34 mg/kg
1
T-dolaflexin
0.67 mg/kg
1.5
2.5
400
140
120
100
80
60
40
20
0
2.5
T-dolaflexin
0.67 mg/kg
-6
Vehicle
800
Dose-dependent, reversible
transaminase elevations ALT
Key hematology parameters - platelets
Fold Relative to Vehicle
In cynomolgus monkeys treated with a single dose of vehicle or T-dolaflexin
at 0.67, 1.34 or 2.68 mg/kg all animals survived until scheduled necropsy with
limited body weight loss. There were no test-article related findings on gross
pathology. Most notable clinical pathology findings were transaminase
elevations (primarily AST), and decreased platelet counts at Day 8.
1.34 mg/kg
600 µg/m2
Endpoint
1000
In mouse the 20 and 30 mg/kg doses were well-tolerated based on body
weight loss and mortality and achieved a therapeutic index (TI) >40.
0.67 mg/kg
Day 3 Fold Change Compared to Vehicle
Mean tumor volume (mm3)
1200
Fold Relative to Vehicle
Fleximer® ADCs utilize a polymer-based conjugation platform to enable high
drug-antibody ratios (DAR) and significantly greater anti-tumor potency
compared to ADCs with DAR 3-4. T-dolaflexin is efficacious at a single dose
of 0.67 mg/kg in mouse xenograft models, and achieves prolonged tumorfree survival after a single 2 mg/kg dose in HER2 2+ expressing model that is
insensitive to ado-trastuzumab emtansine (T-DM1).
NHP Study Design
HER2 2+ JIMT-1 breast cancer xenograft model
~79,000 antigens/cell
Reticulocytes
Trastuzumab-dolaflexin ADC MED <0.67 mg/kg
Summary
AACR 2015
Platelets
#641
-6
22
1
8
15
1
Prothrombin
Time
-6
Study Day (Dosing Day 1)
Study Day (Dosing Day 1)
1
8
15
• Adverse effects in cyno are very comparable to adverse findings
described for T-DM1
• The lack of neutropenia differentiates T-dolaflexin from ADCs with
similar payload class (vc-MMAE)
• T-dolaflexin demonstrates good stability of drug conjugate in
plasma and very low exposure to free drug.
Acknowledgements
0
22
• T-dolaflexin is well tolerated in cynomolgus monkeys at all tested
doses including the highest 2.68 mg/kg. No test-article related
findings in HER2-expressing organs - heart, lungs and GI tract
22
Study Day (Dosing Day 1)
We gratefully acknowledge the contribution to the
characterization of this novel ADC by our collaborators at
Charles River Discovery Research Services (Morrisville, NC
and Wilmington MA), and SNBL (Everett, WA)
Days Post Dose
Mouse
100,000
10
80
70
60
1 died, 1euthanized Day 17
100
1000
Trastuzumab
T-dolaflexin
3.53
5.37
130
Vehicle
2.5mg/kg
5mg/kg
10mg/kg
120
110
100
90
80
70
60
1 euthanized Day 13
100
10
Conjugated Drug
Total mAb
1. Poon KA1, Flagella K, Beyer J, Tibbitts J, Kaur S, Saad O, Yi
JH, Girish S, Dybdal N, Reynolds T. Preclinical safety profile
of trastuzumab emtansine (T-DM1): mechanism of action of its
cytotoxic component retained with improved tolerability.
Toxicol Appl Pharmacol. 2013. 273(2):298-313.
1,000
100
10
1
0
100
200
300
400
Time, hr
500
600
700
0
100
200
400
500
16
19
300
Time, hr
ay
ay
Conjugated Drug
Total Antibody
Free drug (AF‐HPA)
Free drug >1,000x lower than
conjugated drug
0.10
D
D
7
13
ay
D
4
1
10
ay
D
ay
D
D
ay
References
ADC Dose 2.68 mg/kg
10,000
Free drug was not detected in mouse plasma (LLOQ = 0.5 ng/mL)
D
ay
19
16
ay
ay
D
D
7
13
10
ay
ay
D
ay
D
D
4
D
ay
1,000
1
50
1
Kd
50
1
90
Days Post Treatment
100
0.1
100
D
ay
Median Fluorescence
Trastuzumab
T-dolaflexin
0.01
110
50
JIMT-1
150
0
0.001
Vehicle
20mg/kg
30mg/kg
40mg/kg
120
Rat STD10>5 mg/kg
Average % Body Weight
130
Dolaflexin conjugation does not adversely affect ADC target binding
200
Concentration, ng/mL
Mouse MTD=30 mg/kg
Green = mAb, Blue = Fleximer polymer;
Red = XMT-1267 (AF-HPA payload)
Auristatin F-HPA
Concentration, ng/mL
10,000
Average % Body Weight
Intracellular
Drug Release
Cyno
100,000
ADC Dose 0.67 mg/kg
Trastuzumab-dolaflexin ADC well tolerated
n1 ≈ 2
n2 = 4-6
n5 = 3-4
Plasma PK
Days Post Treatment
Trastuzumab-dolaflexin ADC achieved a therapeutic
index (TI) >40
Species
Dose
Level
(mg/kg)
Plasma
Exposure AUC0-504
(ug*hr/mL)
Cyno
2.68
158
Mouse
0.67
53
Calculated
TI
3
Plasma half-life T1/2 (dose range average, days)
Conjugated Drug*
Total Antibody**
4.1+/-0.8
4.2+/-0.5
>30
6.4 +/-1.0
19.9 +/-4.8
9.4+/-1.1
Ab Concentration (nM)
*) Conjugated Toxin BioA by LC/MS/MS; **) Total mAb analysis by ELISA
Drug Release
600
2. Yurkovetskiy A, Bodyak N, Mao Yin, Thomas JD, Conlon P,
Stevenson C, Uttard A, Liu Qin, Gumerov D, Ter-Ovanesyan
E, Gurijula VR, McGillicudy D, Glynn RE, DeVit M, Poling LP,
Park PU, Lowinger TB. Advantages of Polyacetal PolymerBased Antibody Drug Conjugates: application to low
expression targets. 2014 Annual AACR Meeting (San Diego,
CA), Abstract #2645