Radiosynthesis and in Vivo Evaluation of [11C]MPC-6827, the First Brain Penetrant Microtubule PET Ligand

Article abstract of DOI:10.1021/acs.jmedchem.8b00028

Abnormalities of microtubules (MTs) are implicated in the pathogenesis of many CNS diseases. Despite the potential of an MT imaging agents, no PET ligand is currently available for in vivo imaging of MTs in the brain. We radiolabeled [¹¹C]MPC-6

Full text of DOI:10.1021/acs.jmedchem.8b00028

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Brief Article
Radiosynthesis and in vivo evaluation of [11C]MPC-6827,
the first brain penetrant microtubule PET ligand
J. S. Dileep Kumar, Kiran Kumar Solingapuram Sai, Jaya Prabhakaran, Hakeem R Oufkir,
Gayathri Ramanathan, Christopher T Whitlow, Hima Dileep, Akiva Mintz, and J John Mann
J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.8b00028 • Publication Date (Web): 19 Feb 2018
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Radiosynthesis and in vivo evaluation of [11C]MPC-6827, the first
brain penetrant microtubule PET ligand
J. S. Dileep Kumar†,‡ *, Kiran Kumar Solingapuram Sai Î,‡, Jaya Prabhakaran†,§, Hakeem R. Oufkir Î,
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Gayathri Ramanathan Î, Christopher T. Whitlow Î, Hima Dileep†,§, Akiva Mintz Î,II, and J. John Mann†,§
†Molecular Imaging and Neuropathology Division, New York State Psychiatric Institute, 1051 Riverside Drive, New York
10032, USA; ÎDepartment of Radiology, Wake Forest Medical Center, Winston Salem, NC 27157; §Department of Psychia-
try, Columbia University medical Center, New York 10032, USA; IINow at Department of Radiology, Columbia University
medical Center, New York 10032, USA
KEYWORDS: PET, microtubule, radiotracer, cytoskeleton
ABSTRACT: Abnormalities of microtubules (MTs) are implicated in the pathogenesis of many CNS diseases. Despite the poten-
tial of an MT imaging agents, no PET ligand is currently available for in vivo imaging of MTs in the brain. We radiolabeled
[11C]MPC-6827, a high affinity MTA, demonstrated its specific binding in rat and mice brain using PET imaging. Our experiments
show that [11C]MPC-6827 has specific binding to MT in brain, and it is the first MT-binding PET ligand.
INTRODUCTION. MTs are a major component of cytoskeletal
polymers and comprise repeating, non-covalently bound α and β-
tubulin heterodimers.1,2 A major function of MT is to serve as
cellular conveyer belt ferrying vesicles, granules, and organelles
like mitochondria and chromosomes throughout cells. Mutations
associated with MT dynamics, lead to an imbalance between cell
divisions, causing reduced or excessive cell proliferation that can
result in cancer, birth disorders and brain diseases.3-5 MT-
targeting agents (MTA) are among the most successful in anti-
cancer therapy and many MT-related drugs are in various stages
of clinical development. Three classes of ligands (eg. vinca alka-
loids, paclitaxel and derivatives and colchicine) are currently
marketed for the treatment of several malignancies and other dis-
eases.6,8 However, these drugs have several limitations preventing
their clinical applications, such as high level of neurological and
bone marrow toxicity, emergence of drug-resistant tumor cells
due to the overproduction of multidrug resistance protein 1
(MDR1), permeability glycoprotein (P-gp), and breast cancer
resistance protein (BCRP), and overexpression of different tubu-
lins or tubulin mutations. To overcome these hurdles, several new
generation MTAs exhibiting promising results are in clinical trials
for cancer and tauopathies.5, 8-10
dendrites is also associated with normal aging and neuropsychiat-
ric diseases.5, 18, 19 MTs, specifically the βIII-tubulin isoform, are
over-abundant in high-grade gliomas, particularly in glioblastoma
multiform (GBM).20-22 Most older MT-binding drugs did not
show benefits in the context of GBM or brain malignancies, de-
spite efficacy in non CNS cancers. The lack of a MT binding im-
aging agent hampers drug development for brain diseases involv-
ing MTs. A BBB penetrating PET ligand that can quantify MTs
noninvasively would permit imaging a variety of CNS disorders
including brain malignancies and the conduct of target occupancy
studies of potential therapeutic drugs.
[11C]Paclitaxel, [18F]fluoropaclitaxel and [11C]docetaxel are the
successful radiotracers reported so far for MT imaging.23 Of the
three tracers, [18F]fluoropaclitaxel and [11C]docetaxel have been
assessed in preclinical and clinical studies. Since docetaxel and
paclitaxel are well-characterized substrates of efflux transporters
(P-gp, MDR1, BCRP), they have little uptake brain and are not
suitable for brain imaging.23-25 [11C]colchicine, another MT bind-
ing drug (IC50 = 3 µM), has been radiolabeled it does not show
binding in rodent brain.26,27 Radiosynthesis of [18F]fluoro and
[11C]analogues of 2-methoxyestradiol, (an active in vivo metabo-
lite of estrogen), a weak MT ligand, hypoxia inducible factor 1
(HIF-1) and G-protein coupled estrogen receptor (GPER) agonist
and [18F] derivative of chelidonine, another weak MT ligand have
also been reported.28-30 However, no in vivo data are reported for
these potential radiotracers. In summary, hitherto there is no suc-
cessful PET radiotracer available for imaging MTs in brain. Our
screen of MT ligands identified MPC-6827 as a candidate ligand.
MPC-6827 (verubulin aka Azixa, IC50 = 1.5 nM to MT) was se-
lected based on its high MT affinity, selectivity, optimal pharma-
cokinetics, pharmacodynamics, and in vivo preclinical and clini-
cal information available from literature.31-36 Furthermore, for-
mation of the O-demethylated compound MPI-0440627 (4), is
likely the major metabolic pathway for MPC-6827 in rodents and
human subjects.34-36 Therefore, radiolabeling of the methoxy
group resulting in [11C]MPC-6827, via radiomethylation of MPI-
0440627 (desmethyl-MPC-6827) is the most suitable strategy
MTs in mammalian brain comprise approximately 20% of total
brain protein compared with 3%-4% of total protein in somatic
tissues.5 In brain, MTs act as a quantum computer involving a
complex cascade of biological processes that include mitotic divi-
sion, relocation of migrating neurons and the extension of dendrit-
ic and axonal processes. Disruption of the structural integrity of
the MT network and interruption of MT function contribute to the
pathophysiology of central nervous system (CNS) disorders such
as Alzheimer’s Disease (AD).5, 11 MT loss is also reported in Par-
kinson’s disease (PD), progressive supranuclear palsy (PSP) and
corticobasal degeneration (CBD), amyotrophic lateral sclerosis
(ALS), hereditary spastic paraplegia (HSP), multiple sclerosis
(MS), Huntington’s disease (HD), traumatic brain injury (TBI),
chronic traumatic encephalopathy (CTE) and spinal cord injury
(SCI).4, 5, 12-18 MT loss or reduction in MT mass from axons and
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because of the possibility of nonradioactive metabolite formation.
receptors; EP: prostanoid receptors: GABA: gamma-amino butyr-
ic acid; H: histamine; hERG: human ether-a-go-go; KA: Kainate;
KOR: kappa opioid receptors; M: muscarinic; MDR: multidrug
resistance; MOR: mu opioid receptor; mGluR: metabotropic glu-
tamate receptors; NMDA: N-methyl-D-aspartic acid; NK: neuro-
kinin; NET: norepinephrine transporter; NT: neurotrophin; PKC:
Protein kinase C; SERT: serotonin transporter; V: vasopressin;
VMAT: vesicular monoamine transporter
This may be an advantage of [11C]MPC-6827 for in vivo applica-
tions due to the absence of other competing radioactive metabo-
lites via O-demethylation pathway. Herein, we describe the radio-
synthesis and in vivo evaluation of O-[11C]MPC-6827 aka
[11C]MPC-6827 in rodents.
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RESULTS. Synthesis of MPC-6827 (3) was accomplished via
modifications of a previously reported method.37 Binding affinity
and cross selectivity of MPC-6827 to a large panel of brain targets
was assessed through NIMH-PDSP. Except for histamine-4 recep-
tor (H4R, Ki = 155 nM) and sigma-1 receptor (σ1R, Ki =426 nM),
MPC-6827 did not show significant affinity (Ki =>10,000 µM)
for all other tested biogenic brain receptors, transporters, enzymes
and protein targets. Both H4R and σ1 are comparatively low abun-
dance relative to MTs and therefore are unlikely to interfere with
the PET imaging MT quantification by [11C]MPC-6827.
Desmethyl-MPC-6827 (4), was synthesized by O-demethyla-
tion of MPC-6827 with BBr3 in 85% yield (Scheme 1). The
desmethyl product 4, synthesized via demethylation of the parent
molecule, usually contains a very small amount of MPC-6827
(<1%, not detectable by NMR but visible by HPLC) and therefore
may interference with the estimation of specific activity of
[11C]MPC-6827. To avoid this situation, we synthesized the radio-
labeling precursor 4 via an alternate route by coupling compound
1 with 4-(methylamino)phenol (5) in 80% yield (Scheme 1).
Radiosynthesis of [11C]MPC-6827 was performed and validated
in a GE-FX2MeI/FX2M module by reacting precursor 4 with
[11C]CH3I in presence of sodium hydroxide as base (Scheme 1).
[11C]MPC-6827 was produced with a radiochemical yield (RCY)
of 40+5% (n =20), in >99% radiochemical purity and a specific
activity of 2+0.5 Ci/µmol (corrected to end of synthesis (EOS)) in
100% success rate. [11C]MPC-6827 was stable in 5% ethanol-
saline formulation under sterile conditions for 4 h (n=4) and the
logPoct/wat was estimated as 3.8 by shake flask method (n=4).38
After reliably successful radiosyntheses and stability meas-
urements, we examined the in vivo binding of [11C]MPC-6827 in
white male mice by ex vivo biodistribution experiments at 5, 15,
30 and 60 minutes after tracer tail vein administration, in tripli-
cate. [11C]MPC-6827 penetrated the BBB and was retained in
brain (Figure 1A).
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Scheme 1. Synthesis of MPC-6827 and radiosynthesis of
[11C]MPC-6827.
O
OH
Cl
N
N
O
Isopropanol
HCl
BBr3, DCM
N
+
N
N
N
H
N
N
N
4, (85%)
1
3 (MPC-6827, 75%)
2
O
11CH3
Cl
OH
[
11C]CH3I
N
N
Isopropanol
HCl
N
4
+
N
N
H
N
(80%)
1
5
[
11C]3 ([11C]MPC-6827), 40% (EOS)
Table 1. Affinity of MPC-6827 to brain targets.
Targets
Affinity (nM) Targets
Affinity (nM)
>10,000
>10,000
>10,000
>10,000
>10,000
>10000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
6,479
12
1.531, 32
5-HT1A-1E
5 min
MT
15 min
5-HT2A-2C
5-HT2A-2C
5-HT3-7
α2A-2C
AMPA
>10,000
>10,000
>10,000
>10,000
>10,000
5-HT3-7
A
9
6
3
0
30 min
60 min
α1A-1C
β1-3
BZP
Ca+ channel >10,000
CB1, CB2
DAT
D1-D5
DOR
H2
>10,000
>10,000
155
H1
H3, H4
GABA
I
HERG
ΕP
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
>10,000
Figure 1A. Baseline biodistribition of [11C]MPC-6827 in
male white mice (n=3).
ΚΟR
M
KA
12
mGluR
MOR
NK
30 min baseline
MDR1
NET
30 min Blocking
9
>10,000
>10,000
>10,000
>10,000
426
NMDA
NT
NOP
6
3
0
Oxytocin
PKC
PBR
SERT
Sigma 2
Smoothened
Sigma1
Na+Channel >10,000
VMAT 1,2 >10,000
MT: microtubule; 5-HT: 5-hydroxytryptamin; A: adenosine; α:
alpha; β: beta; BZP: benzodiazepine; AMPA: R-amino-3-
hydroxy-5-methyl-4-isoxazolepropionic acid; CB: cannabinoid;
D: dopamine; DAT: dopamine transporters; DOR: delta opioid
Figure 1B. Blocking biodistriution of [11C]MPC-6827 in
mice at 30 minute (n=3).
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The time course of [11C]MPC-6827 in brain indicated a peak at
one step from commercially available precursor chemicals in
good yield. The radioligand exhibited BBB penetration in mice
and rats and was retained in brain consistent with higher affinity
specific binding. The brain uptake of [11C]MPC-6827 was
blocked with cold ligand MPC-6827, confirming specific binding.
Abundant specific binding of [11C]MP-6827 was also observed in
muscle, however, the ratio of specific to nonspecific binding in
brain is 10 times higher than in muscle (Figure 1B). [11C]MPC-
6827 activity in brain was peaked at 5 minute followed by a grad-
ual washout indicating favorable kinetics for tracer quantification
in mouse brain (Figure 1A). We did not find blockade of radiolig-
and binding in heart. In blood there is high plasma binding
(98.2%) of parent ligand in rodents.36 Kidney and liver show high
accumulation of activity in mice and the binding was not dis-
placed with cold MPC-6827 in blocking experiments. This uptake
may be related to metabolism and excretion of the tracer and its
metabolites. Therefore, [11C]MPC-6827 may not be a good PET
radiotracer for imaging tumors in lower thorax or abdomen in
mice. To the best of our knowledge, [11C]MPC-6827 is the first
MT radioligand that penetrates the BBB and specific binding in
vivo in rodents. [11C]MPC-6827 may be a viable radiotracer for
the in vivo imaging of normal MT functions and animal models
with altered brain functions with MT pathology due to its specific
binding and favorable kinetics.
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5 minutes followed by a gradual washout (Figure 1A). We select-
ed to perform blocking experiments at 30 minutes based on time
activity curves of [11C]MPC-6827 in baseline experiments (Figure
1A).At 30 minutes of the biodistribution experiments, 70% specif-
ic binding is observed in brain, after the administration of MPC-
6827 (5 mg/kg, i.v.) 20 minutes prior to the radioligand admin-
istration (n=3, Figure 1B). Apart from brain, muscles, spleen and
lungs showed 60%, 42% and 30% specific binding respectively.
Pancreas and heart show 20% and 16%, specific binding and no
significant specific binding was found in the rest of the tested
regions. Therefore, binding in liver and kidney may be attributed
to nonspecific binding of [11C]MPC-6827 or its metabolites.
Next, we examined the in vivo binding of [11C]MPC-6827 in
athymic nude male mice (n=3) using microPET. As evident from
microPET images (Figure 2), [11C]MPC-6827 penetrates the
BBB and shows excellent retention in mouse brain. Brain activity
was substantially blocked by the i.v. administration of 5 mg/kg
unlabeled MPC-6827, indicating specific binding of [11C]MPC-
6827 to brain MT (n=3). Of note, radioligand binding in thyroid
or salivary gland, is also displaced during the blocking experi-
ments (Figure 2). MicroPET experiments in male Sprague-
Dawley rats indicate BBB penetration and excellent retention of
[11C]MPC-6827 in brain (n=2) (Figure 3).
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CONCLUSIONS. In summary, we developed an automated syn-
thesis of [11C]MPC-6827, a high affinity and selective MT ligand,
in high yield, purity and specific activity. In vivo studies in ro-
dents indicated BBB penetration and binding of the radiotracer in
brain and other organs or tissues. Specificity of [11C]MPC-6827
binding was demonstrated by blocking studies with cold ligand
MPC-6827. Combination of rapid washout and robust specific
binding with excellent brain uptake may make [11C]MPC-6827 a
suitable PET ligand for the in vivo quantification of MT inside
and outside the brain.
EXPERIMENTAL SECTION
Figure 2. Sum of 0-60 minute microPET sagittal images of
[11C]MPC-6827 in a representative mouse brain (left: baseline;
right: blocking with 5 mg/kg MPC-6827; cross lines represent
center of brain).
General Considerations. Solvents are of reagent grade or higher
purity. All reagents were purchased from commercial vendors in
>95% purity and used as received. 1H NMR spectra were recorded
on a Bruker PPX 400-MHz spectrometer. Spectra were recorded
in CD3OD and chemical shifts (δ) are reported in parts per mil-
lion (ppm) relative to tetramethylsilane. The mass spectra were
recorded on a JKS-HX 11UHF/HX110 HF Tandem Mass Spec-
trometer in the fast atom bombardment (EI+) mode. Thin-layer
chromatography was performed using silica gel 60 F254 plates
from E. Merck (Aston, PA). High-performance liquid chromatog-
raphy (HPLC) analyses were performed using a Waters 1525
HPLC system (Milford, MA) and Flash column chromatography
was performed on silica gel (Fisher 200–400 mesh) using the
solvent system indicated in the experimental procedure for each
compound. Chemical purities of biologically tested compounds
MPC-6827 and desmethyl-MPC-6827 were >95% based on re-
verse phase HPLC (RP-HPC) analyses using UV detector at 254
nM. The purities (chemical and radiochemical) and stability of
[11C]MPC-6827 were determined by RP-HPLC (Torrance, CA)
with photodiode array and sodium iodide detectors. Lipophilicity
(expressed as logPoct/water) of [11C]MPC-6827 was estimated by
determining the partition coefficient between 1-octanol and fresh-
ly prepared phosphate buffer using a standard shake flask method
as described elsewhere.38 Biodistribution studies were performed
in male white mice and radioactivity counts were measured using
a Wallac 1480 Wizard Gamma Counter, Perkin Elmer, Turku,
Finland.39 microPET studies were performed in Sprague-Dawley
rats and athymic male nude mice Trifoil PET/CT scanner under
anesthetic condition.40 All animal experiments were carried out
with the approval of the Institutional Animal Care and Use Com-
mittee of Wake Forest University Medical Center.
22.5
0.01
Figure 3. Sum of 0-60 minute microPET sagittal images of
[11C]MPC-6827 in rat brain (left: transverse; middle: coronal;
right: sagittal; cross lines represent center of brain).
DISCUSSION. MPC-6827 is a high affinity, selective MTA (IC50
= 1.5 nM) that demonstrated suppression of tumor growth in a
variety of cancer animal models, proven safe to use in human
subjects, undergone multiple clinical trials for treatment of glio-
blastoma (GBM) and a variety of advanced cancers.31-36 MPC-
6827 is proven to be safe in over 100 cancer patients including
GBM.34-36 Although clinical outcome suggests that the drug as
single agent or combination may have limited success in cancer
therapy, the BBB penetration, lack of MDR resistance, selective
on-target specific binding, facile labeling site and lack of possible
radioactive metabolite and safe use in human subjects are the
merits of [11C]MPC-6827 as a potential CNS PET imaging agent
for the MT target. Reliability of the automated radiosynthesis of
[11C]MPC-6827 was demonstrated by a 100% success rate. Syn-
thesis of MPC-6827 and desmethyl-6827 were accomplished in
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Desmethyl-MPC-6827 (4). 2 mL anhydrous dichloro-methane
were performed at 30 minute post radiotracer injection. All ex-
periments were performed in triplicate.
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4
5
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(DCM) was added to an argon charged reaction vessel containing
o
MPC-6827 (85 mg, 0.3 mmol) at 0 C. 1M solution of BBr3 in
microPET imaging of [11C]MPC-6827 in mice and rats. mi-
croPET imaging of [11C]MPC-6827 was performed as described
previously.40 In brief, microPET experiments were performed in
anesthetized white male mice (n=3) or Sprague-Dawey rats (n=2)
using Trifoil PET/CT scanner. After the transmission scans,
[11C]MPC-6827 (50+10 µCi for mice and 100+20 µCi for rats)
was injected into the tail vein and initiated camera acquisition for
60 minutes and reconstructed using attenuation correction and
Fourier rebinning. Blocking microPET imaging were performed
in white male mice (n=3) 20 prior to the injection of MPC-6827
(5 mg/kg, i. v). The dynamic images were reconstructed using a
filtered back-projection algorithm (microPET Manager).
o
DCM (1 mL) was added dropwise to it at 0 C. The solution was
stirred for 1 h at room temperature. An aliquot of reaction mixture
was quenched with methanol, performed analytical HPLC and
conformed complete conversion of MPC-6827. The reaction was
quenched by dropwise addition of methanol (1 mL) at 0 oC, dilut-
ed with water (5 mL), extracted with 50 mL of DCM (2x25 mL)
followed by 50 mL of ethyl acetate (2 x25 mL). The combined
organic extracts were washed with brine, dried over anhydrous
MgSO4. Solvent was evaporated under reduced pressure and the
residue obtained was washed with ice cold hexane to obtain com-
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1
pound 4 (70 mg, 85%) as a yellow solid. 4: H NMR (400 MHz,
CD3OD) δ: 2.7 (s, 3H), 3.7 (s, 3H), 6.8 (m, 3H), 7.1 (m, 3H), 7.6
(m, 2H); HRMS (EI+) calculated for: C16H16N3O: 266.1293;
Found: 266.1294.
Supporting Information
Molecular formula strings of key chemicals are available as sup-
porting information (CSV). The Supporting Information is availa-
ble free of charge on the ACS Publications website.
Alternative synthesis of compound 4. To a solution of 4-chloro-
2-methylquinazoline (1, 90 mg, 0.5 mmol) and 4-(methylamino)-
phenol (5, 70 mg, 5.75 mmol) in 2 mL of anhydrous isopropanol
(IPA) added 2 drops of concentrated HCl and the reaction mixture
was stirred at room temperature overnight. The yellow precipitate
was collected by filtration, washed with cold isopropanol, and
dried under vacuum to afford compound 4 (105 mg, 80%) as yel-
low solid. Analytical data of compound 4 is identical with the
product obtained using previous method.
AUTHOR INFORMATION
Corresponding Author
*Corresponding author
Fax: 646-774-7521; Tel: 646-774-7522;
E.mail: kmardi@ nyspi.columbia.edu
Radiosynthesis of [11C]MPC-6827. [11C]MeI from FX2MeI
module was bubbled to the reaction vial placed in FX2M module
containing precursor 4 (~0.5 -0.8 mg) in anhydrous DMF (0.6
mL) and 5N NaOH aqueous solution (10.0 µL) for ~5 min at
room temperature. After the complete transfer of radioactivity, the
sealed reaction vial was then heated at 80 °C for 5 min. The reac-
tion mixture was quenched with HPLC mobile phase (1.0 mL)
and injected onto a reverse-phase semi-preparative C18 Phenom-
enex ODS (250 ×10 mm, 10 µ) HPLC column to purify
[11C]MPC-6827. The isocratic HPLC mobile phase solution con-
sisted of 60% acetonitrile, 40% 0.1 M aqueous ammonium for-
mate buffer solution (pH 6.0–6.5) with UV λ @ 254 nm and a
flow rate of 7.0 mL/min. The product [11C]MPC-6827 (Rt = 9.0-
11.0 min) was collected and diluted with 100 mL deionized water,
and passed through C18 SepPak cartridge (WAT036800, Waters,
Milford, MA) to trap the radioactive product. [11C]MPC-6827 was
then directly eluted from the cartridge with absolute ethanol (1.0
mL) and formulated with saline (10% ethanol in saline) into a
sterile vial through a sterile 0.22 µm pyrogen-free filter for further
ORCID
J. S. Dileep kumar 0000-0001-6688-3991
Author Contributions
‡ These authors contributed equally to this work.
Funding Sources
This work was supported by Diane Goldberg Foundation (CUMC/
NYSPI) and Translational Imaging Program (TIP) of the Wake
Forest CTSA (UL1TR001420).
ACKNOWLEDGMENT
We thank NIMH-PDSP for competitive binding assay of MPC-
6827.
ABBREVIATIONS USED
AD: Alzheimer’s Disease; ALS: Amyotrophic lateral sclerosis;
BBB: Blood brain barrier; BCRP: Breast cancer resistance pro-
tein; CTE: Chronic traumatic encephalopathy; CNS: Central
Nervous System; CBD: Corticobasal degeneration; EOS: End of
synthesis; GBM: Glioblastoma multiform; GPER: G-protein cou-
pled estrogen receptor:; HSP: Hereditary spastic paraplegia; H4R:
Histamine-4 receptor ; HD: Huntington’s disease: HIF-1: Hypoxia
inducible factor 1; MT: Microtubule; MTA: Microtubule Target-
ting Agent; MDR1: Multidrug resistance protein 1; MS: Multiple
sclerosis; PD: Parkinson’s disease; P-gp: Permeability glycopro-
tein; PET: Positron Emission Tomography; PSP: Progressive
supranuclear palsy; RCY: Radiochemical yield: RCY; σ1R: Sig-
ma 1 receptor; SCI: Spinal cord injury; TBI: Traumatic brain
injury
animal studies and quality control analysis.
[11C]MPC-6827
purity was assessed using an analytical Phenomenex C18 HPLC
column (250 × 4.6 mm, 5 µ) and with UV λ @ 254 nm. The mo-
bile phase (1.0 mL/min) consisted of 60% acetonitrile and 40%
0.1M aqueous ammonium formate pH 6.0-6.5 solution.
[11C]MPC-6827 showed a retention at 7.1 min, and authentication
of the product was performed with co-injection of the non-
radioactive standard MPC-6827, which demonstrated a similar
retention times.
Biodistribution of [11C]MPC-6827 in mice. Biodistribution ex-
periments were performed as described previously.39 Briefly,
100+20 µCi of [11C]MPC-6827 were administered to male white
mice in 10% ethanol-saline (100 µL per 100 g body weight)
through tail vein injection without anesthesia. Uptake of radio-
tracer in different organs such as brain, heart, lungs, liver, kidney,
spleen, pancreas, muscles and blood were calculated as percent-
ages of injected dose per gram of tissue (%ID/g tissue). Tracer
uptakes in the tissues were measured using a γ-counter and ex-
pressed in %ID/g tissue. Specific binding were demonstrated by
performing blocking studies cold ligand MPC-6827 (5 mg/kg, i.
v), 20 minute prior to radiotracer administration and dissections
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SYNOPSIS TOC
Radiosynthesis and in vivo evaluation of [11C]MPC-6827, the first brain penetrant microtubule PET ligand. J. S. Dileep Ku-
mar*, Kiran Kumar Solingapuram Sai, Jaya Prabhakaran, Hakeem R. Oufkir, Gayathri Ramanathan, Christopher T. Whit-
low, Hima Dileep, Akiva Mintz and J. John Mann
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N
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[11C]MPC-6827 ([11C]3)
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SYNOPSIS TOC
Radiosynthesis and in vivo evaluation of [11C]MPC-6827, the first brain penetrant microtubule PET ligand. J. S. Dileep Ku-
mar*, Kiran Kumar Solingapuram Sai, Jaya Prabhakaran, Hakeem R. Oufkir, Gayathri Ramanathan, Christo-pher T. Whit-
low, Hima Dileep, Akiva Mintz and J. John Mann
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11CH3
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[11C]MPC-6827 ([11C]3)
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