Fully automated dual-run manufacturing of [11C]PIB on FASTlab.

This report describes an updated, fully automated method for the production of [11C]PIB on a cassette-based automated synthesis module. The method allows for two separate productions of [11C]PIB, both of which meet all specification for use in clinical studies. The GE FASTlab developer system was used to create the cassette design as well as the controlling tracer package. The method takes 16 min from the delivery of [11C]MeOTf to the FASTlab, or 35 min from the End of Bombardment; and reliably produces 3547 ± 586 MBq of [11C]PIB in high radiochemical purity (> 98 %). This methodology increases the production capacity of radiopharmaceutical facilities for [11C]PIB, and can easily produce 4 batches in a single day with limited infrastructure footprint.

Fully automated radiosynthesis of [68Ga]Ga-FAPI-46 with cyclotron produced gallium.

BACKGROUND: Radiopharmaceuticals capable of targeting the fibroblast activation protein have become widely utilized in the research realm as well as show great promise to be commercialized; with [68Ga]Ga-FAPI-46 being one of the most widely utilized. Until now the synthesis has relied on generator-produced gallium-68. Here we present a developed method to utilize liquid-target cyclotron-produced gallium-68 to prepare [68Ga]Ga-FAPI-46. RESULTS: A fully-automated manufacturing process for [68Ga]Ga-FAPI-46 was developed starting with the 68Zn[p,n]68Ga cyclotron bombardment to provide [68Ga]GaCl3, automated purification of the [68Ga]GaCl3, chelation with the precursor, and final formulation/purification. The activity levels produced were sufficient for multiple clinical research doses, and the final product met all release criteria. Furthermore, the process consistently provides < 2% of Ga-66 and Ga-67 at the 4-h expiry, meeting the Ph. Eur. CONCLUSIONS: The automated radiosynthesis on the GE FASTlab 2 module purifies the cyclotron output into [68Ga]GaCl3, performs the labeling, formulates the product, and sterilizes the product while transferring to the final vial. Production of > 40 mCi (> 1480 MBq) of [68Ga]Ga-FAPI-46 in excellent radiochemical yield was achieved with all batches meeting release criteria.

Treatment of immune thrombocytopenia in Australian adults: A multicenter retrospective observational study.

Background: In Australia, prescribing restrictions limit access to internationally recommended second-line therapies such as rituximab and thrombopoietin agonists (TPO-A) (eltrombopag and romiplostim). Subsequent lines of therapy include an array of immunosuppressive and immune-modulating agents directed by drug availability and physician and patient preference. Objectives: The objective of the study was to describe the use of first and subsequent lines of treatment for adult immune thrombocytopenia (ITP) in Australia and to assess their effectiveness and tolerability. Patients/Methods: A retrospective review of medical records was conducted of 322 patients treated for ITP at eight participating centers in Australia between 2013 and 2020. Data were analyzed by descriptive statistics and frequency distribution using pivot tables, and comparisons between centers were assessed using paired t tests. Results: Mean age at diagnosis of ITP was 48.8 years (standard deviation [SD], 22.6) and 58.3% were women. Primary ITP was observed in 72% and secondary ITP in 28% of the patients; 95% of patients received first-line treatment with prednisolone (76%), dexamethasone (15%), or intravenous immunoglobulin (48%) alone or in combination. Individuals with secondary ITP were less steroid dependent (72% vs. 76%) and required less treatment with a second-line agent (47% vs. 58%) in the study sample. Over half (56%) of the cohort received treatment with one or more second-line agents. The mean number of second-line agents used for each patient was 1.9 (SD, 1.2). The most used second-line therapy was rituximab, followed by etrombopag and splenectomy. These also generated the highest rates of complete response (60.3%, 72.1%, and 71.8% respectively). The most unfavorable side effect profiles were seen in long-term corticosteroids and splenectomy. Conclusion: A wide range of "second-line" agents were used across centers with variable response rates and side effect profiles. Findings suggest greater effectiveness of rituximab and TPO-A, supporting their use earlier in the treatment course of patients with ITP across Australia.

Longitudinal Consumption of Ergothioneine Reduces Oxidative Stress and Amyloid Plaques and Restores Glucose Metabolism in the 5XFAD Mouse Model of Alzheimer's Disease.

Background: Ergothioneine (ERGO) is a unique antioxidant and a rare amino acid available in fungi and various bacteria but not in higher plants or animals. Substantial research data indicate that ERGO is a physiological antioxidant cytoprotectant. Different from other antioxidants that need to breach the blood-brain barrier to enter the brain parenchyma, a specialized transporter called OCTN1 has been identified for transporting ERGO to the brain. Purpose: To assess whether consumption of ERGO can prevent the progress of Alzheimer's disease (AD) on young (4-month-old) 5XFAD mice. Methods and materials: Three cohorts of mice were tested in this study, including ERGO-treated 5XFAD, non-treated 5XFAD, and WT mice. After the therapy, the animals went through various behavioral experiments to assess cognition. Then, mice were scanned with PET imaging to evaluate the biomarkers associated with AD using [11C]PIB, [11C]ERGO, and [18F]FDG radioligands. At the end of imaging, the animals went through cardiac perfusion, and the brains were isolated for immunohistology. Results: Young (4-month-old) 5XFAD mice did not show a cognitive deficit, and thus, we observed modest improvement in the treated counterparts. In contrast, the response to therapy was clearly detected at the molecular level. Treating 5XFAD mice with ERGO resulted in reduced amyloid plaques, oxidative stress, and rescued glucose metabolism. Conclusions: Consumption of high amounts of ERGO benefits the brain. ERGO has the potential to prevent AD. This work also demonstrates the power of imaging technology to assess response during therapy.

Automated synthesis of (R)-[18 F]MH.MZ on the iPhase Flexlab reaction platform.

(R)-[18 F]MH.MZ ([18 F]MH.MZ) is a promising positron emission tomography (PET) radiotracer for in vivo study of the 5-HT2A receptor. To facilitate clinical trials, a fully automated radiosynthesis procedure for [18 F]MH.MZ was developed using commercially available materials on the iPhase Flexlab module. The overall synthesis time was 100 min with a radiochemical yield of 7 ± 0.9% (n = 3). The radiochemical purity was greater than 99% for [18 F]MH.MZ with a molar activity of 361 ± 57 GBq/µmol (n = 3). The protocol described herein reliably provides [18 F]MH.MZ that meets all relevant release criteria for a GMP radiopharmaceutical.

Improved synthesis of an ergothioneine PET radioligand for imaging oxidative stress in Alzheimer's disease.

L-ergothioneine (ERGO) is a potent antioxidant with cytoprotective effects. To study ERGO biodistribution and detect oxidative stress in vivo, we report an efficient and reproducible preparation of [11 C]-labeled ERGO PET radioligand based on protecting the histidine carboxylic group with a methyl ester. Overall, this new protection approach using methyl ester improved the chemical yield of a 4-step reaction from 14% to 24% compared to the previous report using t-butyl ester. The [11 C]CH3 methylation of the precursor provided the desired product with 55 ± 10% radiochemical purity and a molar activity of 450 ± 200 TBq·mmol-1 . The [11 C]ERGO radioligand was able to detect threshold levels of oxidative stress in a preclinical animal model of Alzheimer's disease.

The effectiveness of using the perioscope as an adjunct to non-surgical periodontal therapy: Clinical and radiographic results.

BACKGROUND: It is well known that following root surface debridement (RSD) residual deposits remain. Periodontal endoscopy has provided a method of directly visualizing root surfaces during periodontal debridement in an intact pocket without the need for surgical incision. The aim of this study was to determine if periodontal debridement using endoscopic visualization was more effective in improving clinical and radiographic parameters as compared to RSD. METHODS: Thirty-eight subjects were randomized into RSD with perioscope (n = 19) or RSD only (n = 19) groups. A full-mouth evaluation included probing pocket depths (PPDs), clinical attachment levels (CAL), bleeding on probing (BOP) and plaque scores (PI) recorded at baseline, 3 and 12 months and compared among groups. Radiographs were taken at sites with deepest pockets at baseline and 12-month and the change in radiographic bone levels (RBL) compared. An independent samples T-test was used to assess statistical significance. RESULTS: Both groups had significant improvements in clinical outcomes. The test (T) group had a significantly lower percentage of PPDs 7 to 9 mm at three (0.72 ± 1.2%) and 12 months (0.5 ± 1.0%) as compared with the control (C) group (2.25 ± 2.9%; 1.84 ± 2.3%). At 12 months, the test group recorded a significantly lower mean PPD (T: 2.70 + 0.2 mm; C: 2.98 ± 0.4 mm), BOP% (T: 4.3 ± 3.2%; C: 11.95 ± 7.1%), PI% (T: 25.61 ± 3.9%; C: 30.11 ± 6.3%) and less change in gingival recession (T: -0.13 ± 0.2 mm; C: -0.50 ± 0.6 mm) (P < 0.05). More radiographic bone gain was observed in the test group (0.69 ± 0.3 mm) as compared with the control group (0.49 ± 0.2 mm). This was also observed around multi-rooted teeth (T: 0.83 ± 0.45 mm; C: 0.46 ± 0.36 mm). CONCLUSION: The adjunctive use of the perioscope provided a slight benefit to the outcomes of non-surgical therapy particularly at deeper probing depths.

Point-of-Care Ultrasound Training in Pediatric Residency: A National Needs Assessment.

BACKGROUND AND OBJECTIVES: As point-of-care ultrasound (POCUS) evolves into a standard tool for the care of children, pediatric residency programs need to develop POCUS training programs. Few POCUS training resources exist for pediatric residents, and little is known about POCUS training in pediatric residencies. We aim to describe pediatric residency leadership perspectives regarding the value of POCUS and to elucidate the current state of POCUS training in pediatric residency programs. METHODS: A group of pediatric educators and POCUS experts developed a novel survey followed by cognitive interviews to establish response-process validity. The survey was administered electronically to pediatric residency associate program directors between December 2019 and April 2020. Program characteristics, including region, setting, and size, were used to perform poststratification for analyses. We performed comparative analyses using program and respondent characteristics. RESULTS: We achieved a 30% (58 of 196) survey response rate. Although only a minority of respondents (26%) used POCUS in clinical practice, a majority (56%) indicated that all pediatric residents should be trained in POCUS. A majority of respondents also considered 8 of 10 POCUS applications important for pediatric residents. Only 37% of programs reported any POCUS training for residents, primarily informal bedside education. Most respondents (94%) cited a lack of qualified instructors as a barrier to POCUS training. CONCLUSIONS: Most pediatric residency programs do not provide residents with POCUS training despite its perceived value and importance. Numerous POCUS applications are considered important for pediatric residents to learn. Future curricular and faculty development efforts should address the lack of qualified POCUS instructors.

A novel antioxidant ergothioneine PET radioligand for in vivo imaging applications.

Ergothioneine (ERGO) is a rare amino acid mostly found in fungi, including mushrooms, with recognized antioxidant activity to protect tissues from damage by reactive oxygen species (ROS) components. Prior to this publication, the biodistribution of ERGO has been performed solely in vitro using extracted tissues. The aim of this study was to develop a feasible chemistry for the synthesis of an ERGO PET radioligand, [11C]ERGO, to facilitate in vivo study. The radioligand probe was synthesized with identical structure to ERGO by employing an orthogonal protection/deprotection approach. [11C]methylation of the precursor was performed via [11C]CH3OTf to provide [11C]ERGO radioligand. The [11C]ERGO was isolated by RP-HPLC with a molar activity of 690 TBq/mmol. To demonstrate the biodistribution of the radioligand, we administered approximately 37 MBq/0.1 mL in 5XFAD mice, a mouse model of Alzheimer's disease via the tail vein. The distribution of ERGO in the brain was monitored using 90-min dynamic PET scans. The delivery and specific retention of [11C]ERGO in an LPS-mediated neuroinflammation mouse model was also demonstrated. For the pharmacokinetic study, the concentration of the compound in the serum started to decrease 10 min after injection while starting to distribute in other peripheral tissues. In particular, a significant amount of the compound was found in the eyes and small intestine. The radioligand was also distributed in several regions of the brain of 5XFAD mice, and the signal remained strong 30 min post-injection. This is the first time the biodistribution of this antioxidant and rare amino acid has been demonstrated in a preclinical mouse model in a highly sensitive and non-invasive manner.

Design, Synthesis, and Validation of a Novel [11C]Promethazine PET Probe for Imaging Abeta Using Autoradiography.

Promethazine, an antihistamine drug used in the clinical treatment of nausea, has been demonstrated the ability to bind Abeta in a transgenic mouse model of Alzheimer's disease. However, so far, all of the studies were performed in vitro using extracted tissues. In this work, we report the design and synthesis of a novel [11C]promethazine PET radioligand for future in vivo studies. The [11C]promethazine was isolated by RP-HPLC with radiochemical purity >95% and molar activity of 48 TBq/mmol. The specificity of the probe was demonstrated using human hippocampal tissues via autoradiography.

Effect of blood transfusions on cognitive development in very low birth weight infants.

OBJECTIVE: Preterm infants frequently receive red cell transfusions; however, the effect of transfusions on cognition is unclear. We evaluated the relationship between transfusions and cognitive outcomes in preterm infants enrolled in a randomized trial of erythropoiesis stimulating agents (ESAs). STUDY DESIGN: Preterm infants were randomized to ESAs or placebo during initial hospitalization, and transfusions recorded. Children were evaluated using standard developmental tests of cognition at 18-22 months (56 ESA, 24 placebo) and 3.5-4 years (39 ESA, 14 placebo). RESULTS: Cognitive scores at 18-22 months were inversely correlated with transfusion volume (p = 0.02). Among those receiving ≥1 transfusion, cognitive scores were significantly higher in the ESA-treated group (p = 0.003). At 3.5-4 years, transfusions were not correlated with cognitive scores. CONCLUSIONS: In the placebo group, transfused children had lower cognitive scores than did non-transfused children at 18-22 months. In the ESA group, cognitive scores did not differ by transfusion status, suggesting ESAs might provide neuroprotection.

Shared Mental Models Among Clinical Competency Committees in the Context of Time-Variable, Competency-Based Advancement to Residency.

PURPOSE: To evaluate response process validity evidence for clinical competency committee (CCC) assessments of first-year residents on a subset of General Pediatrics Entrustable Professional Activities (EPAs) and milestones in the context of a national pilot of competency-based, time-variable (CBTV) advancement from undergraduate to graduate medical education. METHOD: Assessments of 2 EPAs and 8 milestones made by the trainees' actual CCCs and 2 different blinded "virtual" CCCs for 48 first-year pediatrics residents at 4 residency programs between 2016 and 2018 were compared. Residents had 3 different training paths from medical school to residency: time-variable graduation at the same institution as their residency, time-fixed graduation at the same institution, or time-fixed graduation from a different institution. Assessments were compared using ordinal mixed-effects models. RESULTS: Actual CCCs assigned residents higher scores than virtual CCCs on milestones and one EPA's supervision levels. Residents who graduated from a different institution than their residency received lower milestone ratings than either group from the same institution; CBTV residents received higher ratings on one milestone (ICS4) and similar ratings on all others compared with non-CBTV residents who completed medical school at the same institution. CONCLUSIONS: First-year residents who graduated from CBTV medical school programs were assessed as having the same level of competence as residents who graduated from traditional medical school programs, but response process evidence suggests that members of CCCs may also draw on undocumented personal knowledge of the learner to draw conclusions about resident competence.

Narrative Performance Level Assignments at Initial Entrustment and Graduation: Integrating EPAs and Milestones to Improve Learner Assessment.

PURPOSE: To determine which narrative performance level for each general pediatrics entrustable professional activity (EPA) reflects the minimum level clinical competency committees (CCCs) felt should be associated with graduation as well as initial entrustment and compare expected narrative performance levels (ENPLs) for each EPA with actual narrative performance levels (ANPLs) assigned to residents at initial entrustment. METHOD: A series of 5 narratives, corresponding to the 5 milestone performance levels, were developed for each of the 17 general pediatrics EPAs. In academic year (AY) 2015-2016, the CCCs at 22 Association of Pediatric Program Directors Longitudinal Educational Assessment Research Network member sites reported ENPLs for initial entrustment and at time of graduation. From AYs 2015-2016 to 2017-2018, programs reported ANPLs for initial entrustment decisions. ENPLs and ANPLs were compared using a logistic mixed effects model. RESULTS: ENPLs for graduation and entrustment were most often level 3 (competent) followed by level 4 (proficient). For 8 EPAs, the ENPLs for graduation and entrustment were the same. For the remaining 9, some programs would entrust residents before graduation or graduate them before entrusting them. There were 4,266 supervision level reports for initial entrustment for which an ANPL was provided. ANPLs that were lower than the ENPLs were significantly more likely to be assigned to the medical home-well child (OR = 0.39; 95% CI: 0.26-0.57), transition to adult care (OR = 0.43; 95% CI: 0.19-0.95), behavioral or mental health (OR = 0.36; 95% CI: 0.18-0.71), make referrals (OR = 0.31; 95% CI: 0.17-0.55), lead a team (OR = 0.34; 95% CI: 0.22-0.52), and handovers (OR = 0.18; 95% CI: 0.09-0.36) EPAs. CONCLUSIONS: CCCs reported lower ENPLs for graduation than for entrustment for 5 EPAs, possibly indicating curricular gaps that milestones and EPAs could help identify.

A Structured Neonatal Parenting Elective: An Approach for Parenting Leave During Residency.

OBJECTIVE: Pregnancy is common during residency, yet the duration of allowed paid leave is inadequate and utilizing unpaid family medical leave act (FMLA) time has financial and professional consequences. We evaluated the effectiveness of a novel parenting elective, consistent with educational goals for pediatric residents, on resident parents' financial, academic, and family outcomes. METHODS: In 2010, a 2-4 week structured at-home elective of outpatient neonatal care with full pay was implemented. Data were collected from all new parents in a large academic pediatric residency from 2002 to 2018, including duration of leave, on-time graduation, choice to pursue postresidency training, and unpaid FMLA leave. Data were compared from before/after implementation and by parent type (mothers or resident partners of mothers). RESULTS: Twenty-two pregnancies occurred prior to implementation and 42 afterward. In mothers, leave duration was similar (7.9 ± 3.5 weeks before, 8.0 ± 0.3 after, P = .50) but the minimum time increased from 2 to 6 weeks and those taking ≥7 weeks increased (54% vs 96%, P = .002). Mothers using unpaid FMLA time decreased (38% vs 7%, P = .04) although on-time graduation (69% vs 93%, P = .13) and postresidency training rates were similar. Among partners, leave duration increased (0.8 ± 0.4 weeks vs 4.0 ± 1.7, P < .001) and 79% took ≥4 weeks, compared to 0% pre-elective (P < .001). In partners, postresidency training, FMLA, or on-time graduation rates did not change. CONCLUSIONS: Parenting a neonate provides learning opportunities for pediatric residents that can be encompassed in an elective consistent with training requirements. This elective improved outcomes for mothers and partners and is generalizable to any training program.

NICU Discharge Feeding Bundle Improves Accuracy of Postdischarge Feeding Preparation and Potentially Prevents Readmission.

BACKGROUND: Hospitalized infants often need fortified human milk and formulas for growth in the neonatal intensive care unit and postdischarge. Parents must learn how to properly mix infant feedings.At the initial Children's Hospital Colorado follow-up visit, baseline data revealed a 50% rate of mixing inaccuracy of discharge feeding recipes and identified the readmission of 2 infants with life-threatening hypernatremia. A gap in discharge teaching was identified. A quality improvement project was implemented at 2 affiliated neonatal intensive care units. PURPOSE/AIM: The aim of this study was to improve parental comfort and efficacy in infant feeding preparation during hospitalization, reduce mixing inaccuracy postdischarge, and prevent readmission. The primary aim was to improve the accuracy rate at follow-up to 75% within 12 months and the sustain mixing accuracy rate at follow-up to above 95% for an additional 24 months. METHODS/INTERVENTIONS: A literature review was conducted; potential barriers were identified and strategies developed to recognize the relationships between the aim and the changes to be tested. Implementation of standardized teaching focused on the teach-back technique. Education included mixing demonstration and written instructions. Parents were expected to correctly mix the recipe 3 times before discharge. RESULTS: Mixing accuracy at the initial clinic follow-up visit improved to 97%. No readmissions were reported from inaccurately prepared feedings. IMPLICATIONS FOR PRACTICE: Collaborative quality improvement project with standardized teaching provided improved feeding safety and parental comfort with accuracy of discharge instructions. Primary care providers need to be aware of the importance of accurate formula or fortified human milk preparation and verify accuracy of the specific discharge recipes at the initial visit.

Syntheses and in vitro biological evaluation of S1PR1 ligands and PET studies of four F-18 labeled radiotracers in the brain of nonhuman primates.

A series of seventeen hydroxyl-containing sphingosine 1-phosphate receptor 1 (S1PR1) ligands were designed and synthesized. Their in vitro binding potencies were determined using [32P]S1P competitive binding assays. Compounds 10a, 17a, 17b, and 24 exhibited high S1PR1 binding potencies with IC50 values ranging from 3.9 to 15.4 nM and also displayed high selectivity for S1PR1 over other S1P receptor subtypes (IC50 > 1000 nM for S1PR2-5). The most potent compounds 10a, 17a, 17b, and 24 were subsequently radiolabeled with F-18 in high yields and purities. MicroPET studies in cynomolgus macaque showed that [18F]10a, [18F]17a, and [18F]17b but not [18F]24 crossed the blood brain barrier and had high initial brain uptake. Further validation of [18F]10a, [18F]17a, and [18F]17b in preclinical models of neuroinflammation is warranted to identify a suitable PET radioligand to quantify S1PR1 expression in vivo as a metric of an inflammatory response.

Automated radiosynthesis of 5-[11C]l-glutamine, an important tracer for glutamine utilization.

INTRODUCTION: The natural amino acid l-Glutamine (Gln) is essential for both cell growth and proliferation. In addition to glucose, cancer cells utilize Gln as a carbon source for ATP production, biosynthesis, and as a defense against reactive oxygen species. The utilization of [11C]Gln has been previously reported as a biomarker for tissues with an elevated demand for Gln, however, the previous reports for the preparation of [11C]Gln were found to be lacking several crucial aspects necessary for transition to human production. Namely, the presence of unreacted precursor and the use of non-commercialized, custom built, reaction platforms. Herein, we report the development and utilization of methodology for the automated production of [11C]Gln that meets institutional criteria for human use. METHODS: The preparation of [11C]Gln was carried out on the GE FX2N platform. Briefly, after trapping of [11C]HCN with a solution of CsHCO3 in DMF, the [11C]CsCN was reacted with a commercially available precursor. This intermediate was then purified by HPLC and deprotected/hydrolyzed under acidic conditions. Following pH adjustment, the product was filtered to give the desired [11C]Gln as a sterile injectable. The resulting product was then analyzed for quality assurance. RESULTS: Automated production by this method reliably provides over 3.7 GBq (100 mCi) of [11C]Gln. The resulting final drug product was found to have a >99% radiochemical purity, <5% of D-Gln present, no detectable impurities, and the total preparation time was roughly 45 min from the end-of-bombardment. CONCLUSIONS: A fast, reliable and efficient automated radiosynthesis was developed using a commercially available module. Purifications used throughout allow for both a radiochemically and chemically pure final product solution of [11C]Gln.

Syntheses and in vitro evaluation of new S1PR1 compounds and initial evaluation of a lead F-18 radiotracer in rodents.

Thirteen new sphingosine-1-phosphate receptor 1 (S1PR1) ligands were designed and synthesized by replacing azetidine-3-carboxylic acid moiety of compound 4 with new polar groups. The in vitro binding potency of these new analogs toward S1PR1 was determined. Out of 13 new compounds, four compounds 9a, 10c, 12b, and 16b displayed high S1PR1 binding potency with IC50 values of 13.2 ±â€¯3.2, 14.7 ±â€¯1.7, 9.7 ±â€¯1.6, and 6.3 ±â€¯1.3 nM, respectively; further binding studies of these four ligands toward S1PR2-5 suggested they are highly selective for S1PR1 over other S1PRs. The radiosynthesis of the lead radiotracer [18F]12b was achieved with good radiochemical yield (∼14.1%), high radiochemical purity (>98%), and good specific activity (∼54.1 GBq/µmol, decay corrected to the end of synthesis, EOS). Ex vivo autoradiography and initial biodistribution studies in rodents were performed, suggesting that [18F]12b was able to penetrate the blood-brain barrier (BBB) with high brain uptake (0.71% ID/g at 60 min post-injection) and no defluorination was observed. In vitro autoradiography study in brain slices of lipopolysaccharides (LPS)-induced neuroinflammation mice indicated that SEW2871, a specific S1PR1 ligand was able to reduce the uptake of [18F]12b, suggesting [18F]12b has S1PR1 specific binding. These initial results suggested that [18F]12b has potential to be an F-18 labeled radiotracer for imaging S1PR1 in the brain of the animal in vivo.

A promising carbon-11-labeled sphingosine-1-phosphate receptor 1-specific PET tracer for imaging vascular injury.

BACKGROUND: Sphingosine-1-phosphate receptor 1 (S1PR1) is highly expressed in vascular smooth muscle cells from intimal lesions. PET imaging using S1PR1 as a biomarker would increase our understanding of its role in vascular pathologies including in-stent restenosis. METHODS: The S1PR1 compound TZ3321 was synthesized for in vitro characterization and labeled with Carbon-11 for in vivo studies. The biodistribution of [11C]TZ3321 was evaluated in normal mice; microPET and immunohistochemistry (IHC) studies were performed using a murine femoral artery wire-injury model of restenosis. RESULTS: The high potency of TZ3321 for S1PR1 (IC 50 = 2.13 ± 1.63 nM), and high selectivity (>1000 nM) for S1PR1 over S1PR2 and S1PR3 were confirmed. Biodistribution data revealed prolonged retention of [11C]TZ3321 in S1PR1-enriched tissues. MicroPET imaging of [11C]TZ3321 showed higher uptake in the wire-injured arteries of ApoE-/- mice than in injured arteries of wild-type mice (SUV 0.40 ± 0.06 vs 0.28 ± 0.04, n = 6, P < .001); FDG-PET showed no difference (SUV 0.98 ± 0.04 vs 0.94 ± 0.01, n = 6, P > .05). Post-PET autoradiography showed >4-fold higher [11C]TZ3321 retention in the injured artery of ApoE-/- mice than in wild-type mice. Subsequent IHC staining confirmed higher expression of S1PR1 in the neointima of the injured artery of ApoE-/- mice than in wild-type mice. CONCLUSIONS: This preliminary study supports the potential use of PET for quantification of the S1PR1 expression as a biomarker of neointimal hyperplasia.

Design, Synthesis, and In Vitro and In Vivo Evaluation of an (18)F-Labeled Sphingosine 1-Phosphate Receptor 1 (S1P1) PET Tracer.

Sphingosine 1-phosphate receptor 1 (S1P1) plays a pivotal signaling role in inflammatory response; because S1P1 modulation has been identified as a therapeutic target for various diseases, a PET tracer for S1P1 would be a useful tool. Fourteen fluorine-containing analogues of S1P ligands were synthesized and their in vitro binding potency measured; four had high potency and selectivity for S1P1 (S1P1 IC50 < 10 nM, >100-fold selectivity for S1P1 over S1P2 and S1P3). The most potent ligand, 28c (IC50 = 2.63 nM for S1P1) was (18)F-labeled and evaluated in a mouse model of LPS-induced acute liver injury to determine its S1P1-binding specificity. The results from biodistribution, autoradiography, and microPET imaging showed higher [(18)F]28c accumulation in the liver of LPS-treated mice than controls. Increased expression of S1P1 in the LPS model was confirmed by immunohistochemical analysis (IHC). These data suggest that [(18)F]28c is a S1P1 PET tracer with high potential for imaging S1P1 in vivo.