V. Stepanov et al.
1-(2-fluoro-4-(2-oxopyrrolidin-1-yl)phenyl)-5-[11C]methoxy-3-(1-
phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-9) (Figure 1)
[
11C]KIT-9 was synthesized from 1-(2-fluoro-4-(2-oxopyrrolidin-1-yl)
phenyl)-5-hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one and
purified using acetonitrile/aq. triethylamine 0.1% 370:630 v/v as mobile
phase at a flow of 6 ml/min. Radioactivity yield was 2445 645 MBq
and radiochemical purity >99%. The analysis was performed using
acetonitrile/aq. phosphoric acid 0.05 M 400:600 v/v. Specific radioactivity
was 501 121 GBq/μmol (n = 2).
1-(4-(3,5-dimethylisoxazol-4-yl)-2-fluorophenyl)-5-[11C]methoxy-
3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-12) (Figure 1)
[
11C]KIT-12 was synthesized from 1-(4-(3,5-dimethylisoxazol-4-yl)-2-
fluorophenyl)-5-hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one
and purified using acetonitrile/aq. triethylamine 0.1% 470:530 v/v as
mobile phase at a flow of 6 ml/min. Radioactivity yield was 1613 196 MBq
and radiochemical purity >99%. The analysis was performed using
acetonitrile/aq. phosphoric acid 0.05 M 450:550 v/v. Specific radioactivity
was 375 303 GBq/μmol (n = 2).
Figure 1. Summary of labeling procedure for [11C]KIT-1, [11C]KIT-3, [11C]KIT-5, [11C]
KIT-6, [11C]KIT-7, [11C]KIT-9, and [11C]KIT-12.
PET measurements in NHPs
1-(4-(3,3-dimethyl-2-oxopyrrolidin-1-yl)-2-fluorophenyl)-5-[11C]
methoxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-3)
(Figure 1)
A total of 14 PET measurements were performed with three female
rhesus monkeys (Macaca mulatta), with each of the seven radioligands
evaluated in two different monkeys. The monkeys were housed in the
Astrid Fagraeus Laboratory of the Swedish Institue for Infectious Disease
Control, Solna, Sweden. The study was approved by the Animal Ethics
Committee of the Swedish Animal Welfare Agency and was performed
according to ‘Guidelines for planning, conducting and documentic
experimental research’ (Dnr 4820706-600) of the Karolinska Institutet
and international guidelines.24 Anesthesia of the monkeys was induced
by intramuscular injection of ketamine hydrochloride (~10 mg/kg,
Ketaminol vet.; Intervet, Sollentuna, Sweden) and maintained by the
administration of a mixture of sevoflurane (2–8%, Sevoflurane®; Abbott
Scandinavia AB, Solna, Sweden), oxygen, and medical air after
endotracheal intubation. The head was immobilized with a fixation
device.25 Body temperature was maintained by a Bair Hugger device
(model 505; Arizant Health Care, MN, USA) and monitored by an oral
thermometer. Electrocardiogram, heart rate, respiratory rate, oxygen
saturation, and arterial blood pressure were continuously monitored
throughout the experiment. PET measurements were conducted using
the High Resolution Research Tomograph system (Siemens Molecular
Imaging, TN, USA). A six-minute transmission scan using a single 137Cs
source was obtained immediately before the radioligand injection. List-
mode data were acquired for 123 min. PET images were reconstructed
with a series of frames of increasing duration (9 × 20, 3 × 60, 5 × 180,
and 17 × 360 s) using the ordinary Poisson three-dimensional ordered-
subset expectation maximization algorithm, with 10 iterations and 16
subsets, including modeling of the point spread function, after correction
for attenuation, random, and scatter. The in-plane resolution of the
reconstructed images was approximately 1.5 mm.26
Venous blood sampling (1–2 ml each) was performed at À5 min (for
protein binding) and 4, 15, 30, 60, 90, and 120 min (for radiometabolite
analysis) after the radioligand injection.
Regions of interest (ROI) for the whole brain was delineated manually
on the coregistered magnetic resonance imaging (MRI)/PET images for all
seven PET radioligands. The time activity curves of the ROIs were
generated by applying the ROI to the dynamic PET data. The data were
expressed as % injected dose (%ID), which is the total uptake (MBq) in
the region divided by the injected radioactivity (MBq) × 100.
For the evaluation of regional brain uptake, the ROIs were delineated
manually on the putamen, caudate, frontal cortex, temporal cortex, and
cerebellum on the coregistered MRI images. The time radioactivity curves
of the ROIs were generated by applying the ROI to the dynamic PET data.
[
11C]KIT-3 was synthesized from 1-(4-(3,3-dimethyl-2-oxopyrrolidin-1-yl)-
2-fluorophenyl)-5-hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-
one and purified using acetonitrile/aq. triethylamine 0.1% 470:530 v/v
as mobile phase at a flow of 6 ml/min. Radioactivity yield was 3170 300
MBq, and radiochemical purity >99%. The analysis was performed using
acetonitrile/aq. phosphoric acid 0.05 M 500:500 v/v. Specific radioactivity
was 517 42 GBq/μmol (n = 2).
1-(4-(3,3-difluoroazetidin-1-yl)-2-fluorophenyl)-5-[11C]methoxy-3-
(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-5) (Figure 1)
[
11C]KIT-5 was synthesized from 1-(4-(3,3-difluoroazetidin-1-yl)-2-
fluorophenyl)-5-hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one
and purified using acetonitrile/aq. triethylamine 0.1% 500:500 v/v as
mobile phase at a flow of 6 ml/min. Radioactivity yield was 2960 380
MBq, and radiochemical purity >99.8%. The analysis was performed
using acetonitrile/aq. phosphoric acid 0.05 M 530:470 v/v. Specific
radioactivity was 775 399 GBq/μmol (n=2).
1-(2-fluoro-4-(tetrahydro-2H-pyran-4-yl)phenyl)-5-[11C]methoxy-3-
(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-6) (Figure 1)
[
11C]KIT-6 was synthesized from 1-(2-fluoro-4-(tetrahydro-2H-pyran-4-yl)
phenyl)-5-hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one and
purified using acetonitrile/aq. triethylamine 0.1% 440:560 v/v as mobile
phase at a flow of 6 ml/min. Radioactivity yield was 2828 351 MBq
and radiochemical purity >99.5%. The analysis was performed using
acetonitrile/aq. phosphoric acid 0.05 M 460:540 v/v. Specific radioactivity
was 1643 377 GBq/μmol (n = 6).
1-(2-fluoro-4-morpholinophenyl)-5-[11C]methoxy-3-(1-phenyl-1H-
pyrazol-5-yl)pyridazin-4(1H)-one ([11C]KIT-7) (Figure 1)
[
11C]KIT-7 was synthesized from 1-(2-fluoro-4-morpholinophenyl)-5-
hydroxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one and purified
using acetonitrile/aq. triethylamine 0.1% 410:590 v/v as mobile phase at
a
flow of 6 ml/min. Radioactivity yield was 2585 170 MBq and
radiochemical purity >99.5%. The analysis was performed using The data were expressed as % standard uptake value (%SUV), which is
acetonitrile/aq. phosphoric acid 0.05 M 400:600 v/v. Specific radioactivity
was 106 34 GBq/μmol (n = 2).
regional uptake (MBq/cc)/injected radioactivity (MBq) × body weight
(g) × 100.
Copyright © 2015 John Wiley & Sons, Ltd.
J. Label Compd. Radiopharm 2015, 58 202–208