#1572
Pharmacokinetics of the Novel Fumagillol Conjugate XMT-1107 in the Rat
Alex Yurkovetskiy, Dana L. Shkolny, Laura C. Akullian, Mao Yin, Laraine L. Meyers, Robert J. Fram, Timothy B. Lowinger
Mersana Therapeutics Inc., Cambridge, MA
XMT-1107 in vitro stability
100000
10000
Released XMT-1191
1000
Scheme 1. XMT-1191 and XMT-1201 are the major XMT1107 conjugate release products in vivo
O
Rat plasma PK of conjugated/conjugate
released XMT-1191 and free XMT-1191
MeO
H
O
O
O
l
HO
O
m
HO
HO
HO
H 3C
O
n
HO
O
O
O
NH
O
HO
OM e
HN
O
O
l
O
HO
CH3
H
O
HO
Conjugated XMT-1191
(XMT-1107)
O
O
m
HO
HO
O
HO
O
HO
k
HO
HO
O
O
O
H
O
O
NH
O
HO
O
CH3
H
OM e
Conjugated XMT-1191/XMT-1201
HN
O
O
O
HO
O
O
H
OMe
H
N
O
H
N
OH
O
O
OH
H
CH 3
H
OM e
H
N
H
C H3
O
H
N
OH
O
O
O
XMT-1191
In vivo plasma PK of conjugated XMT-1191 was monoexponential with very little to no
distribution phase and was characterized by low volume of distribution (58 mL) and slow
plasma clearance (1.9 mL/h), indicating that conjugated XMT-1191 was concentrated
primarily in the vascular compartment and had low hepatic clearance.
O
Conjugated XMT-1191 was characterized by an extended plasma exposure (AUC0-inf ~
27,000 µg*hr /mL) and plasma half-life (21.6 hours). Plasma exposure to conjugate
released XMT-1191 was low and represented not more than 0.15 % of the corresponding
conjugated XMT-1191 AUC values.
Comparison of the PK for XMT-1191 released upon dosing of XMT-1107 with the PK
obtained for XMT-1191 dosed directly as an iv bolus indicates that conjugation of XMT1191 to the PHF polymer carrier reduces Cmax and prolongs the exposure to XMT-1191 (t
½ mean values for XMT-1107 released and non-conjugated XMT-1191 were 24.1 hours
and 0.1 hours respectively) without substantial difference in overall AUC (see Table 1).
XMT-1201
The data obtained show that the slow rate of XMT-1191 release from the polymer
conjugate XMT-1107, rather than the pharmacokinetic behavior of XMT-1191 itself,
appears to be an important factor contributing to the overall PK profiles of both XMT1107 and its release product XMT-1191 in rat plasma. (see Table 1).
Released 1201
100000
10000
1000
100
Released XMT-1201
Conjugated XMT-1201
0.25
0.20
0.15
0.10
0.05
0.00
20
40
60
80
100
0
Time After Administration, hours
10
0
10
20
30
40
40
60
80
100
Time After Administration, hours
Conclusions
50
Time, hours
Figure 1. Conjugated XMT-1191, conjugate released XMT-1191 and free XMT1191 rat plasma time concentration profiles: (♦) Conjugated XMT-1107; (▲)
Release product XMT-1191; (●) XMT-1191 (after dosing XMT-1191 as iv bolus).
Data reported as XMT-1191 equivalent/mL, mean ± SD, N=4.
Table 1. PK Characteristics for Conjugated/Conjugate Released XMT-1191 and
Free XMT-1191 (mean value, N=4)
t½
20
Figure 2. Rat plasma kinetics of conjugated and released XMT-1201
after XMT-1107 iv bolus administration at 45 mg/kg dose level
(mean value, N=3).
XMT-1191 bolus
hr
T max
hr
C max
ug/ml
AUC0-48
ug*hr/ml
AUC 0-inf
ug*hr/ml
CL
mL/hr
Vd
mL
Conjugated XMT1191 (after dosing
XMT-1107)
21.6
0.083
1,091
19,236
26,692
1.9
58
XMT-1191
(released upon dosing
of XMT-1107)
24.1
0.083
1.2
21.8
29.8
n/a
n/a
XMT-1191
(dosed directly
without conjugation)
0.10
0.083
63.0
22.0
22.0
2312
188
O
n
Total Conjugate
0
100
Study
O
O
H
H
OH
O
OH
HO
O
O
NH
O
0.30
Conjugated 1201
1000000
10
O
NH
Conjugated 1191
XMT-1201 content, mol fraction
Conjugated XMT-1191
1000000
1
At physiological conditions (PBS, pH 7.4, 37oC) XMT-1107 undergoes slow hydrolytic
degradation with an overall t ½ of approximately 200 hours, releasing predominantly
XMT-1191. Under the same conditions, both free and conjugated XMT-1191 undergo pH
dependent hydrolytic transformation of spiral and aliphatic epoxy groups resulting in the
formation of the biologically inactive XMT-1201 derivatives. The rate of XMT-1191/1201
transformation is ~ 20 fold less than the rate of conjugate drug release. In rat plasma in
vitro XMT-1107 releases XMT-1191/1201 with t ½ of ~25 hours, indicating a substantial
contribution of plasma esterases to the drug release kinetics.
B. Accumulation of Conjugated and Released
XMT-1201 in Rat Plasma
10000000
Fm derivative plasma concentration, ng/ml
XMT-1107, a fumagillol-derived polymer conjugate, and XMT-1191, the in vivo XMT1107 release product, were administered to Sprague-Dawley rats intravenously (iv) as a
single bolus at 50.6 mg XMT-1191 equivalents/kg. Blood was collected over 48 hours
after administration to determine the highest concentration and extent of exposure (Cmax
and AUC), volume of distribution (Vd), clearance (CL), and elimination half-life (t ½).
The conjugated and released (free) XMT-1191 and XMT-1201 in plasma were analyzed
by LC-MS/MS. The LLOQ for free and conjugated XMT-1191/1201 determination in
rat plasma was 5 ng/mL and 25 ng/mL respectively.
XMT-1107 is a novel polymer fumagillol derivative, comprised of the small
molecule XMT-1191 conjugated to a 70 kDa biodegradable, hydrophilic
polyacetal, poly(1-hydroxymethylethylene hydroxylmethylformal) (PHF, or
Fleximer®. XMT-1191, the primary release product of XMT-1107, induces
antiangiogenic activity by irreversible inhibition of methionine aminopeptidase 2
and exhibits antiproliferative activity at nanomolar concentrations in a HUVEC
cell assay. The conjugated drug, XMT-1107, demonstrates significant
improvement in antitumor activity in tumor xenograft models compared to either
unconjugated XMT-1191 or the well-known fumagillol derivative TNP-470. In
this study we evaluated the pharmacokinetics (PK) of XMT-1107 and its
biologically active release product XMT-1191 in rat and demonstrated that the
selected polymer delivery system extends exposure to conjugated drug and the
corresponding drug release product, XMT-1191, while significantly (> 500 fold)
reducing XMT-1191 plasma Cmax.
Equivalent XMT-1191 plasma concentration,
ng/ml
Methods
Summary
A. Conjugated and Released XMT-1201 Rat PK
10000000
Rat PK of conjugated and free XMT-1201
Rat PK of conjugated and released forms of XMT-1201 followed the trends observed for
conjugated and released XMT-1191, indicating release dependent kinetics (t ½ ~ 60 hours).
The exposure to conjugated and released XMT-1201 over 96 hours (AUC 0-96) relative to
conjugated XMT-1191 was approximately 12 % and 0.003% respectively. The analysis of
time dependence of fractional composition of XMT-1107 has shown that XMT1191/XMT-1201 transformation takes place predominantly in the plasma compartment
with a rate constant of ~ 2x10-2 (h-1).
• Conjugation to the polymer carrier, PHF, provides extended exposure to
the conjugated drug XMT-1107 and the conjugate release product XMT1191, while significantly (> 500 fold) reducing XMT-1191 plasma Cmax.
• The majority of plasma exposure after XMT-1107 administration is
accounted for by conjugated XMT-1191. The exposure (AUC) to XMT1107 released XMT-1191 and XMT-1201 and conjugated XMT-1201 is
approximately 0.15%, 0.003% and 12% of conjugated XMT-1191
respectively.
• Estimated t ½ values appear generally comparable for conjugated and
conjugate released XMT-1191 and ranges from approximately 20 to 28
hours.
• The observed low CL and Vd values for conjugated XMT-1191 indicates
low hepatic extraction and distribution of the conjugate limited to the
plasma compartment.
• Rat plasma PK of conjugated and conjugate released XMT-1191 is found
to be drug release kinetics dependent with drug-conjugate linkage plasma
stability being a major contributing factor.
References
1. Yurkovetskiy, A. V.; Hiller, A.; Syed, S.; Yin, M.; Lu, X. M.; Fischman, A. J.; Papisov, M. I. Synthesis
of a macromolecular camptothecin conjugate with dual phase drug release. Mol Pharm. 2004 Sep-Oct;
1(5):375-82
2. Gibaldi, M. and Perrier, D., Pharmacokinetics, Second Ed., Marcel Dekker: New York, New York
(1982).
3. Davies, B. and Morris, T., “Physiological Parameters in Laboratory Animals and Humans”,
Pharmaceutical Research, 10(7): 1093-1095 (1993).