Synthesis of carbon-11-labeled isonicotinamides as new potential PET agents for imaging of GSK-3 enzyme in Alzheimer’s disease

The authentic standards 2-(cyclopropanecarboxamido)-N-(4-methoxypyridin-3-yl)isonicotinamide (4a) and 2-(cyclopropanecarboxamido)-N-(4-(4-methoxyphenyl)pyridin-3-yl)isonicotinamide (7a), and their corresponding precursors 2-(cyclopropanecarboxamido)-N-(4-hydroxypyridin-3-yl)isonicotinamide (4b) and 2-(cyclopropanecarboxamido)-N-(4-(4-hydroxyphenyl)pyridin-3-yl)isonicotinamide (7b) were synthesized from methyl 2-aminoisonicotinate and cyclopropanecarbonyl chloride with overall chemical yield 47% in three steps, 22% in four steps, 40% in three steps, and 17% in four steps, respectively. The target tracers 2-(cyclopropanecarboxamido)-N-(4-[11C]methoxypyridin-3-yl)isonicotinamide ([11C]4a) and 2-(cyclopropanecarboxamido)-N-(4-(4-[11C]methoxyphenyl)pyridin-3-yl)isonicotinamide ([11C]7a) were prepared from the precursors (4b and 7b) with [11C]CH3OTf through O-[11C]methylation and isolated by HPLC combined with SPE in 40–50% radiochemical yield, based on [11C]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the specific activity (SA) at EOB was 370–1110 GBq/μmol with a total synthesis time of ∼40-min from EOB

Synthesis of [11C]MK-1064 as a new PET radioligand for imaging of orexin-2 receptor

The reference standard MK-1064 {5″-chloro-N-((5,6-dimethoxypyridin-2-yl)methyl)-[2,2′:5′,3″-terpyridine]-3′-carboxamide} was synthesized from methyl 2-chloro-5-iodonicotinate and 5-(chloropyridin-3-yl)boronic acid in 4 steps with 33% overall chemical yield. The precursor desmethyl-MK-1064 {5″-chloro-N-((5-hydroxy-6-methoxypyridin-2-yl)methyl)-[2,2′:5′,3″-terpyridine]-3′-carboxamide} for radiolabeling was synthesized from 2-bromopyridin-3-ol and 5″-chloro-[2,2′:5′,3″-terpyridine]-3′-carboxylic acid in 6 steps with 17% overall chemical yield. The target tracer [11C]MK-1064 {5″-chloro-N-((5-[11C]methoxy-6-methoxypyridin-2-yl)methyl)-[2,2′:5′,3″-terpyridine]-3′-carboxamide} was prepared by O-[11C]methylation of its corresponding precursor desmethyl-MK-1064 with [11C]CH3OTf under basic condition and isolated by a simplified solid-phase extraction (SPE) method in 50–60% decay corrected radiochemical yields based on [11C]CO2 at end of bombardment (EOB). The overall synthesis time from EOB was 23 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 185–555 GBq/μmol

Synthesis of carbon-11-labeled CK1 inhibitors as new potential PET radiotracers for imaging of Alzheimer’s disease

The reference standards methyl 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoate (5a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-methoxybenzamide (5c), and their corresponding desmethylated precursors 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoic acid (6a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-hydroxybenzamide (6b), were synthesized from 5-amino-2,2-difluoro-1,3-benzodioxole and 3-substituted benzoic acids in 5 and 6 steps with 33% and 11%, 30% and 7% overall chemical yield, respectively. Carbon-11-labeled casein kinase 1 (CK1) inhibitors, [11C]methyl 3-((2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)carbamoyl)benzoate ([11C]5a) and N-(2,2-difluoro-5H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]imidazol-6-yl)-3-[11C]methoxybenzamide ([11C]5c), were prepared from their O-desmethylated precursor 6a or 6b with [11C]CH3OTf through O-[11C]methylation and isolated by HPLC combined with SPE in 40–45% radiochemical yield, based on [11C]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the molar activity (MA) at EOB was 370–740 GBq/μmol with a total synthesis time of ∼40-min from EOB

Fully automated synthesis of [18F]T807, a PET tau tracer for Alzheimer’s disease

The authentic standard T807 and its nitro-precursor T807P as well as t-Boc-protected T807P precursor for radiolabeling were synthesized from (4-bromophenyl)boronic acid, 3-bromo-4-nitropyridine and 3-bromo-6-nitropyridine with overall chemical yield 27% in three steps, 4–7% in three to five steps, and 3–8% in four to five steps, respectively. [18F]T807 was synthesized from T807P by the nucleophilic [18F]fluorination with K[18F]F/Kryptofix 2.2.2 in DMSO at 140 °C followed by reduction with Fe powder/HCOOH through manual synthesis with 5–10% decay corrected radiochemical yield in two steps. [18F]T807 was also synthesized from t-Boc-protected T807P by a concurrent [18F]fluorination and deprotection with K[18F]F/Kryptofix 2.2.2 in DMSO at 140 °C and purified by HPLC-SPE method in a home-built automated [18F]radiosynthesis module with 20–30% decay corrected radiochemical yield in one step. The specific activity of [18F]T807 at end of bombardment (EOB) was 37–370 GBq/μmol

Synthesis of a PET tau tracer [11C]PBB3 for imaging of Alzheimer’s disease

The authentic standard PBB3 and its precursor N-desmethyl-PBB3 as well as TBS-protected N-desmethyl-PBB3 precursor for radiolabeling were synthesized from 5-bromo-2-nitropyridine, acrolein diethyl acetal, 6-methoxy-2-methylbenzothiazole, and diethylchlorophosphate with overall chemical yield 1% in six steps, 2% in five steps, and 1% in six steps, respectively. [11C]PBB3 was prepared from either desmethyl-PBB3 or TBS-protected desmethyl-PBB3 with [11C]CH3OTf through N-[11C]methylation and isolated by HPLC combined with SPE in 20–25% and 15–20% radiochemical yield, respectively, based on [11C]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the specific activity at EOB was 370–1110 GBq/μmol with a total synthesis time of ∼40-min from EOB

Synthesis of [11C]HG-10-102-01 as a new potential PET agent for imaging of LRRK2 enzyme in Parkinson’s disease

The reference standard (4-((5-chloro-4-(methylamino)pyrimidin-2-yl)amino)-3-methoxyphenyl)(morpholino)methanone (HG-10-102-01) and its precursor (4-((5-chloro-4-(methylamino)pyrimidin-2-yl)amino)-3-hydroxyphenyl)(morpholino)methanone (desmethyl-HG-10-102-01) were synthesized from 2,4,5-trichloropyrimide and 3-methoxy-4-nitrobenzoic acid with overall chemical yield 49% in four steps and 14% in five steps, respectively. The target tracer (4-((5-chloro-4-(methylamino)pyrimidin-2-yl)amino)-3-[11C]methoxyphenyl)(morpholino)methanone ([11C]HG-10-102-01) was prepared from the precursor desmethyl-HG-10-102-01 with [11C]CH3OTf through O-[11C]methylation and isolated by HPLC combined with SPE in 45–55% radiochemical yield, based on [11C]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the specific activity (SA) at EOB was 370–1110 GBq/μmol with a total synthesis time of ∼40-min from EOB

Synthesis of [11C]CX-6258 as a new PET tracer for imaging of Pim kinases in cancer

The reference standard CX-6258 {(E)-5-chloro-3-((5-(3-(4-methyl-1,4-diazepane-1-carbonyl)phenyl)furan-2-yl)methylene)indolin-2-one, 4a} and its desmethylated precursor N-desmethyl-CX-6258 {(E)-3-((5-(3-(1,4-diazepane-1-carbonyl)phenyl)furan-2-yl)methylene)-5-chloroindolin-2-one, 5} for radiolabeling were synthesized from 5-bromo-2-furaldehyde and 3-carboxybenzeneboronic acid in 3 and 4 steps with 29–49% and 24–32% overall chemical yield, respectively. The target tracer [11C]CX-6258 {(E)-5-chloro-3-((5-(3-(4-[11C]methyl-1,4-diazepane-1-carbonyl)phenyl)furan-2-yl)methylene)indolin-2-one, [11C]4a} was prepared from N-desmethyl-CX-6258 (5) with [11C]CH3OTf under basic condition (2 N NaOH) through N-[11C]methylation and isolated by HPLC combined with solid-phase extraction (SPE) in 40–50% radiochemical yield based on [11C]CO2 and decay corrected to end of bombardment (EOB) with 370–1110 GBq/μmol specific activity at EOB

Synthesis of [11C]GSK1482160 as a new PET agent for targeting P2X7 receptor

The authentic standards GSK1482160 and its isomer, as well as the radiolabeling precursors desmethyl-GSK1482160 and Boc-protected desmethyl-GSK1482160 were synthesized from l-pyroglutamic acid, methyl l-pyroglutamate and 2-chloro-3-(trifluoromethyl)benzylamine with overall chemical yield 27–28% in 3 steps, 58% in 4 steps, 76% in 1 step and 33% in 2 steps, respectively. [11C]GSK1482160 was prepared from either desmethyl-GSK1482160 or Boc-protected desmethyl-GSK1482160 with [11C]CH3OTf through N-[11C]methylation and isolated by HPLC combined with SPE in 40–50% and 30–40% radiochemical yield, respectively, based on [11C]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was >99%, and the specific activity at EOB was 370–1110 GBq/μmol with a total synthesis time of ∼40-min from EOB

Synthesis and preliminary biological evaluation of radiolabeled 5-BDBD analogs as new candidate PET radioligands for P2X4 receptor

P2X4 receptor has become an interesting molecular target for treatment and PET imaging of neuroinflammation and associated brain diseases such as Alzheimer’s disease. This study reports the first design, synthesis, radiolabeling and biological evaluation of new candidate PET P2X4 receptor radioligands using 5-BDBD, a specific P2X4 receptor antagonist, as a scaffold. 5-(3-Hydroxyphenyl)-1-[11C]methyl-1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-one (N-[11C]Me-5-BDBD analog, [11C]9) and 5-(3-Bromophenyl)-1-[11C]methyl-1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-one (N-[11C]Me-5-BDBD, [11C]8c) were prepared from their corresponding desmethylated precursors with [11C]CH3OTf through N-[11C]methylation and isolated by HPLC combined with SPE in 30–50% decay corrected radiochemical yields with 370–1110 GBq/µmol specific activity at EOB. 5-(3-[18F]Fluorophenyl)-1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-one ([18F]F-5-BDBD, [18F]5a) and 5-(3-(2-[18F]fluoroethoxy)phenyl)-1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-one ([18F]FE-5-BDBD, [18F]11) were prepared from their corresponding nitro- and tosylated precursors by nucleophilic substitution with K[18F]F/Kryptofix 2.2.2 and isolated by HPLC-SPE in 5–25% decay corrected radiochemical yields with 111–740 GBq/µmol specific activity at EOB. The preliminary biological evaluation of radiolabeled 5-BDBD analogs indicated these new radioligands have similar biological activity with their parent compound 5-BDBD

XRCC1 codon 399Gln polymorphism is associated with radiotherapy-induced acute dermatitis and mucositis in nasopharyngeal carcinoma patients

BACKGROUND: To evaluate the association between single nucleotide polymorphisms (SNPs) at the 194 and 399 codons of XRCC1, and the risk of severe acute skin and oral mucosa reactions in nasopharyngeal carcinoma patients in China. METHODS: 114 patients with nasopharyngeal carcinoma were sequentially recruited in this study. Heparinized peripheral blood samples were taken for SNPs analysis before the start of radiation treatment. SNPs in XRCC1 (194Arg/Trp and 399Arg/Gln) gene were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Dermatitis at upper neck and oral mucositis were clinically recorded according to the Common Terminology Criteria for Adverse Events v.3.0. RESULTS: The variant allele frequencies were 0.289 for XRCC1 194Trp and 0.263 for XRCC1 399Gln. Of the 114 patients, 24 experienced grade 3 acute dermatitis and 48 had grade 3 acute mucositis. The XRCC1 399Arg/Gln was significantly associated with the development of grade 3 dermatitis (Odds Ratio, 2.65; 95% CI, 1.04–6.73; p = 0.037, χ2 = 4.357). In addition, it was also associated with higher incidence of grade 3 mucositis with a borderline statistical significance (Odds Ratio, 2.11; 95% CI, 0.951–4.66; p = 0.065, χ2 = 3.411). The relationship between XRCC1 194Arg/Trp and acute dermatitis, and mucositis was not found. CONCLUSIONS: Our investigation shows, for the first time, that patients with the XRCC1 399Arg/Gln genotype were more likely to experience severe acute dermatitis and oral mucositis. With further validation, the information can be used to determine personalized radiotherapy strategy