Achilles Tendon Tissue Turnover Before and Immediately After an Acute Rupture.

BACKGROUND: An Achilles tendon rupture (ATR) is a frequent injury and results in the activation of tendon cells and collagen expression, but it is unknown to what extent turnover of the tendon matrix is altered before or after a rupture. PURPOSE/HYPOTHESIS: The purpose of this study was to characterize tendon tissue turnover before and immediately after an acute rupture in patients. It was hypothesized that a rupture would result in pronounced collagen synthesis in the early phase (first 2 weeks) after the injury. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: The study included patients (N = 18) eligible for surgery after an ATR. At the time of inclusion, the patients ingested deuterium oxide (2H2O) orally, and on the day of surgery (within 14 days of the injury), they received a 3-hour flood-primed infusion of an 15N-proline tracer. During surgery, the patients had 1 biopsy specimen taken from the ruptured part of the Achilles tendon and 1 that was 3 to 5 cm proximal to the rupture as a control. The biopsy specimens were analyzed for carbon-14 (14C) levels in the tissue to calculate long-term turnover (years), incorporation of 2H-alanine (from 2H2O) into the tissue to calculate the fractional synthesis rate (FSR) of proteins in the short term (days), and incorporation of 15N-proline into the tissue to calculate the acute FSR (hours). RESULTS: Both the rupture and the control samples showed consistently lower levels of 14C compared with the predicted level of 14C in a healthy tendon, which indicated increased tendon turnover in a fraction (48% newly synthesized) of the Achilles tendon already for a prolonged period before the rupture. Over the first days after the rupture, the synthesis rate for collagen was relatively constant, and the average synthesis rate on the day of surgery (2-14 days after the rupture) was 0.025% per hour, irrespective of the length of time after a rupture and the site of sampling (rupture vs control). No differences were found in the FSR between the rupture and control samples in the days after the rupture. CONCLUSION: Higher than normal tissue turnover in the Achilles tendon before a rupture indicated that changes in the tendon tissue preceded the injury. In addition, we observed no increase in tendon collagen tissue turnover in the first 2 weeks after an ATR. This favors the view that an increase in the formation of new tendon collagen is not an immediate phenomenon during the regeneration of ruptured tendons in patients. REGISTRATION: NCT03931486 (ClinicalTrials.gov identifier).

Visualizing reactive astrocyte-neuron interaction in Alzheimer's disease using 11C-acetate and 18F-FDG.

Reactive astrogliosis is a hallmark of Alzheimer's disease (AD). However, a clinically validated neuroimaging probe to visualize the reactive astrogliosis is yet to be discovered. Here, we show that PET imaging with 11C-acetate and 18F-fluorodeoxyglucose (18F-FDG) functionally visualizes the reactive astrocyte-mediated neuronal hypometabolism in the brains with neuroinflammation and AD. To investigate the alterations of acetate and glucose metabolism in the diseased brains and their impact on the AD pathology, we adopted multifaceted approaches including microPET imaging, autoradiography, immunohistochemistry, metabolomics, and electrophysiology. Two AD rodent models, APP/PS1 and 5xFAD transgenic mice, one adenovirus-induced rat model of reactive astrogliosis, and post-mortem human brain tissues were used in this study. We further curated a proof-of-concept human study that included 11C-acetate and 18F-FDG PET imaging analyses along with neuropsychological assessments from 11 AD patients and 10 healthy control subjects. We demonstrate that reactive astrocytes excessively absorb acetate through elevated monocarboxylate transporter-1 (MCT1) in rodent models of both reactive astrogliosis and AD. The elevated acetate uptake is associated with reactive astrogliosis and boosts the aberrant astrocytic GABA synthesis when amyloid-ß is present. The excessive astrocytic GABA subsequently suppresses neuronal activity, which could lead to glucose uptake through decreased glucose transporter-3 in the diseased brains. We further demonstrate that 11C-acetate uptake was significantly increased in the entorhinal cortex, hippocampus and temporo-parietal neocortex of the AD patients compared to the healthy controls, while 18F-FDG uptake was significantly reduced in the same regions. Additionally, we discover a strong correlation between the patients' cognitive function and the PET signals of both 11C-acetate and 18F-FDG. We demonstrate the potential value of PET imaging with 11C-acetate and 18F-FDG by visualizing reactive astrogliosis and the associated neuronal glucose hypometablosim for AD patients. Our findings further suggest that the acetate-boosted reactive astrocyte-neuron interaction could contribute to the cognitive decline in AD.

The role of optimal cut-off diagnosis in 11C-methionine PET for differentiation of intracranial brain tumor from non-neoplastic lesions before treatment.

PURPOSE: Amino acid positron emission tomography (PET) may provide additional information to computed tomography and magnetic resonance imaging for detecting the pretreatment diagnosis of intracranial lesions. The purpose of this study was to investigate the role of cutoff values of 11C-METPET, an amino acid PET tracer, in the differentiation of pretreatment brain tumors from non-neoplastic lesions. METHODS: This retrospective cohort study analyzed 101 pretreatment patients with a definitive diagnosis out of a total of 425 consecutive 11C-METPET imaging studies. The standardized uptake values (SUV) and the ratios of lesion to contralateral normal frontal-lobe gray matter uptake (L/N ratios) were measured. Cutoff values for the differential diagnosis of brain tumors from non-neoplastic lesions were determined using receiver operating characteristics curve (ROC) analysis. RESULTS: Based on the ROC analyses, the cutoffs were 3.33 for maximum SUV, 2.54 for mean SUV, 2.33 for peak SUV, 2.04 for Lmax/Nmean, and 2.23 for Lmax/Nmax. The sensitivity and specificity of these cutoffs were 69.2% and 82.6%, respectively, for maximum SUV, 64.1% and 91.3% for mean SUV, 69.2% and 91.3% for peak SUV, 70.5% and 91.3% for Lmax/Nmax and 75.6% and 82.6% for Lmax/Nmean. CONCLUSION: In differentiating intracranial brain tumor from non-neoplastic lesion with 11C-METPET, the use of optimal cutoff values indicates the high specificity, which means that positive result indicates the high likelihood of brain tumor. Considering the high specificity of 11C-METPET, more invasive examinations such as biopsy may be considered in positive cases.

Effect of soak and smear on [14C]-hydrocortisone in vitro human skin percutaneous penetration.

INTRODUCTION: 'Soak and smear' method, water soaking to induce skin hydration followed by topical corticoids application suggests effectiveness in clinical dermatological practice. We investigate one possible mechanism of soaking times effect on drug partitioning and diffusion rates in skin and its proposed efficacy. METHODS: Utilizing an in vitro flow-through diffusion system to evaluate efficacy of the 'soak and smear' method following 0.5, 8, and 20 min water soaking and [14C]-hydrocortisone topical application on human skin to probe the possibility of percutaneous penetration enhancement. RESULTS: In water-soak groups, more [14C]-hydrocortisone was absorbed and retained in stratum corneum and epidermis, whereas, in the control (no soak) more was in the deep skin-dermis and receptor fluid. These differences between water-soak groups and the control are statistically significant (p < .05). CONCLUSION: Effect of 'soak and smear' on skin absorption and penetration depends on interaction of individual drug's physicochemical property, stratum corneum hydration, and stratum corneum-epidermoid barrier status. Water soaking (≤ 20 min) induced skin hydration increases [14C]-hydrocortisone absorption and retention into the upper skin layer but not deep layers. This could support the proposed hypothesis of clinical dermatological treatment of hydrocortisone to local skin inflammations should the epidermis be found to be a key target for atopic dermatitis therapy.

Neuroprotective effects of minocycline and KML29, a potent inhibitor of monoacylglycerol lipase, in an experimental stroke model: a small-animal positron emission tomography study.

Hypoxia caused by ischemia induces acidosis and neuroexcitotoxicity, resulting in neuronal death in the central nervous system (CNS). Monoacylglycerol lipase (MAGL) is a modulator of 2-arachidonoylglycerol (2-AG), which is involved in retrograde inhibition of glutamate release in the endocannabinoid system. In the present study, we used positron emission tomography (PET) to monitor MAGL-positive neurons and neuroinflammation in the brains of ischemic rats. Additionally, we performed PET imaging to evaluate the neuroprotective effects of an MAGL inhibitor in an ischemic injury model. Methods: Ischemic-injury rat models were induced by intraluminal right middle cerebral artery occlusion (MCAO). PET studies of the brains of the ischemic rats were performed at several experimental time points (pre-occlusion, days 2, 4, and 7 after the MCAO surgery) using [11C]SAR127303 for MAGL and [18F]FEBMP for 18 kDa translocator protein (TSPO, a hall-mark of neuroinflammation). Medication using minocycline (a well-known neuroprotective agent) or KML29 (a potent MAGL inhibitor) was given immediately after the MCAO surgery and then daily over the subsequent three days. Results: PET imaging of the ischemic rats using [11C]SAR127303 showed an acute decline of radioactive accumulation in the ipsilateral side at two days after MCAO surgery (ratio of the area under the curve between the ipsilateral and contralateral sides: 0.49 ± 0.04 in the cortex and 0.73 ± 0.02 in the striatum). PET imaging with [18F]FEBMP, however, showed a moderate increase in accumulation of radioactivity in the ipsilateral hemisphere on day 2 (1.36 ± 0.11), and further increases on day 4 (1.72 ± 0.15) and day 7 (1.99 ± 0.06). Treatment with minocycline or KML29 eased the decline in radioactive accumulation of [11C]SAR127303 for MAGL (minocycline-treated group: 0.82 ± 0.06 in the cortex and 0.81 ± 0.05 in the striatum; KML29-treated group: 0.72 ± 0.07 in the cortex and 0.88 ± 0.04 in the striatum) and increased uptake of [18F]FEBMP for TSPO (minocycline-treated group: 1.52 ± 0.21 in the cortex and 1.56 ± 0.11 in the striatum; KML29-treated group: 1.63 ± 0.09 in the cortex and 1.50 ± 0.17 in the striatum). In MCAO rats, minocycline treatment showed a neuroprotective effect in the sensorimotor cortex suffering from severe hypoxic injury, whereas KML29 treatment saved neurons in the striatum, including bundles of myelinated axons. Conclusions: PET imaging allowed visualization of the different neuroprotective effects of minocycline and KML29, and indicated that combination pharmacotherapy using these drugs may be an effective therapy in acute ischemia.

Clinical evaluation of neuroinflammation in child-onset focal epilepsy: a translocator protein PET study.

BACKGROUND: Neuroinflammation is associated with various chronic neurological diseases, including epilepsy; however, neuroimaging approaches for visualizing neuroinflammation have not been used in the clinical routine yet. In this study, we used the translocator protein positron emission tomography (PET) with [11C] DPA713 to investigate neuroinflammation in the epileptogenic zone in patients with child-onset focal epilepsy. METHODS: Patients with intractable focal epilepsy were recruited at the Epilepsy Center of Osaka University; those who were taking any immunosuppressants or steroids were excluded. PET images were acquired for 60 min after intravenous administration of [11C] DPA713. The PET image of [11C] DPA713 was co-registered to individual's magnetic resonance imaging (MRI), and the standardized uptake value ratio (SUVr) in regions of interest, which were created in non-lesions and lesions, was calculated using the cerebellum as a pseudo-reference region. In the case of epilepsy surgery, the correlation between SUVr in lesions and pathological findings was analyzed. RESULTS: Twenty-seven patients (mean age: 11.3 ± 6.2 years, male/female: 17/10) were included in this study. Of these, 85.1% showed increased uptake of [11C] DPA713 in the focal epileptic lesion. Three patients showed epileptic spasms, suggesting partial seizure onset, and all 18 patients with abnormal lesions on MRI were similarly highlighted by significant uptake of [11C] DPA713. DPA713-positive patients had a broad range of etiologies, including focal cortical dysplasia, tumors, infarction, and hippocampal sclerosis. Five out of nine MRI-negative patients showed abnormal [11C] DPA713 uptake. The SUVr of [11C] DPA713 in lesions was significantly higher than that in non-lesions. In seven patients who underwent epilepsy surgery, increased [11C] DPA713 uptake was associated with microglial activation. CONCLUSIONS: This study indicates that [11C] DPA713 uptake has valuable sensitivity in the identification of epileptic foci in child-onset focal epilepsy, and inflammation is implicated in the pathophysiology in the epileptic foci caused by various etiologies. Further research is required to establish diagnostic tools for identifying focal epileptogenic zones.

Final Results of the Prospective Biomarker Trial PETra: [11C]-MET-Accumulation in Postoperative PET/MRI Predicts Outcome after Radiochemotherapy in Glioblastoma.

PURPOSE: This prospective trial investigates the association of time to recurrence (TTR) in glioblastoma with [11C]methionine (MET) tracer uptake before postoperative radiochemotherapy (RCT) aiming to guide radiotherapy boost regions. EXPERIMENTAL DESIGN: Between 2013 and 2016, 102 patients with glioblastoma were recruited. RCT was performed with concurrent and adjuvant temozolomide to a total dose of 60 Gy. Tumor residues in postresection PET and MRI were together defined as gross tumor volumes for radiotherapy treatment planning. [11C]methionine (MET)-PET/MRI was performed before RCT and at each follow-up. RESULTS: The primary hypothesis of a longer TTR for patients without increased tracer accumulation in postoperative MET-PET was confirmed in 89 patients. With 18.9 months (95% confidence interval, 9.3-28.5 months), median TTR was significantly (P < 0.001) longer for patients without (n = 29, 32.6%) as compared with 6.3 months (3.6-8.9) for patients with MET accumulation (n = 60, 67.4%) in pre-RCT PET. Although MRI often did not detect all PET-positive regions, an unfavorable impact of residual tumor in postsurgical MRI (n = 38, 42.7%) on TTR was observed [4.6 (4.2-5.1) vs. 15.5 months (6.0-24.9), P < 0.001]. Significant multivariable predictors for TTR were MRI positivity, PET-positive volume, and O6-methylguanine DNA methyltransferase (MGMT) hypermethylation. CONCLUSIONS: Postsurgical amino acid PET has prognostic value for TTR after RCT in glioblastoma. Because of the added value of the metabolic beyond the pure structural information, it should complement MRI in radiotherapy planning if available with reasonable effort, at least in the context of maximal therapy. Furthermore, the spatial correlation of regions of recurrence with PET-positive volumes could provide a bioimaging basis for further trials, for example, testing local radiation dose escalation.

Complete inhibition of ABCB1 and ABCG2 at the blood-brain barrier by co-infusion of erlotinib and tariquidar to improve brain delivery of the model ABCB1/ABCG2 substrate [11C]erlotinib.

P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) restrict at the blood-brain barrier (BBB) the brain distribution of the majority of currently known molecularly targeted anticancer drugs. To improve brain delivery of dual ABCB1/ABCG2 substrates, both ABCB1 and ABCG2 need to be inhibited simultaneously at the BBB. We examined the feasibility of simultaneous ABCB1/ABCG2 inhibition with i.v. co-infusion of erlotinib and tariquidar by studying brain distribution of the model ABCB1/ABCG2 substrate [11C]erlotinib in mice and rhesus macaques with PET. Tolerability of the erlotinib/tariquidar combination was assessed in human embryonic stem cell-derived cerebral organoids. In mice and macaques, baseline brain distribution of [11C]erlotinib was low (brain distribution volume, VT,brain < 0.3 mL/cm3). Co-infusion of erlotinib and tariquidar increased VT,brain in mice by 3.0-fold and in macaques by 3.4- to 5.0-fold, while infusion of erlotinib alone or tariquidar alone led to less pronounced VT,brain increases in both species. Treatment of cerebral organoids with erlotinib/tariquidar led to an induction of Caspase-3-dependent apoptosis. Co-infusion of erlotinib/tariquidar may potentially allow for complete ABCB1/ABCG2 inhibition at the BBB, while simultaneously achieving brain-targeted EGFR inhibition. Our protocol may be applicable to enhance brain delivery of molecularly targeted anticancer drugs for a more effective treatment of brain tumors.

Functional imaging with 11C-metomidate PET for subtype diagnosis in primary aldosteronism.

OBJECTIVE: Endocrine Society guidelines recommend adrenal venous sampling (AVS) in primary aldosteronism (PA) if adrenalectomy is considered. We tested whether functional imaging of adrenal cortex with 11C-metomidate (11C-MTO) could offer a noninvasive alternative to AVS in the subtype classification of PA. DESIGN: We prospectively recruited 58 patients with confirmed PA who were eligible for adrenal surgery. METHODS: Subjects underwent AVS and 11C-MTO-PET without dexamethasone pretreatment in random order. The lateralization of 11C-MTO-PET and adrenal CT were compared with AVS in all subjects and in a prespecified adrenalectomy subgroup in which the diagnosis was confirmed with immunohistochemical staining for CYP11B2. RESULTS: In the whole study population, the concordance of AVS and 11C-MTO-PET was 51% and did not differ from that of AVS and adrenal CT (53%). The concordance of AVS and 11C-MTO-PET was 55% in unilateral and 44% in bilateral PA. In receiver operating characteristics analysis, the maximum standardized uptake value ratio of 1.16 in 11C-MTO-PET had an AUC of 0.507 (P = n.s.) to predict allocation to adrenalectomy or medical therapy with sensitivity of 55% and specificity of 44%. In the prespecified adrenalectomy subgroup, AVS and 11C-MTO-PET were concordant in 10 of 19 subjects with CYP11B2-positive adenoma and in 6 of 10 with CYP11B2-positivity without an adenoma. CONCLUSIONS: The concordance of 11C-MTO-PET with AVS was clinically suboptimal, and did not outperform adrenal CT. In a subgroup with CYP11B2-positive adenoma, 11C-MTO-PET identified 53% of cases. 11C-MTO-PET appeared to be inferior to AVS for subtype classification of PA.

An original radio-biomimetic approach to synthesize radiometabolites for PET imaging.

To fully exploit the potential of positron emission tomography (PET) imaging to assess drug distribution and pharmacokinetics in the central nervous system, the contribution of radiometabolites to the PET signal has to be determined for correct interpretation of data. However, radiosynthesis and extensive study of radiometabolites are rarely investigated and very challenging for complex drugs. Therefore, an original radio-biomimetic (RBM) approach was developed to rapidly synthesize radiometabolites and non-invasively investigate their kinetics with PET imaging. This method enabled the challenging radiosynthesis of [11C]nor-buprenorphine ([11C]nor-BUP), the main metabolite of buprenorphine (BUP) which has been identified as a substrate of the P-glycoprotein (P-gp) transport function at the blood-brain barrier (BBB). Biomimetic conditions using cytochromes P450 3A4 to convert BUP into nor-BUP were optimized taking into account the short half-life of carbon-11 (t1/2 = 20.4 min). Those conditions afforded 32% of conversion within 20 min and were applied to the biomimetic radiosynthesis of [11C]nor-BUP from [11C]BUP. Automated radiosynthesis of [11C]BUP according to a procedure described in the literature followed by optimized RBM conditions afforded [11C]nor-BUP in 1.5% decay-corrected radiochemical yield within 90 min and 90 ± 15 GBq/µmol molar activity. HPLC quality control showed chemical and radiochemical purities above 98%. To demonstrate the applicability of the RBM approach to preclinical studies, brain PET images in rats showed a drastic lower uptake of [11C]nor-BUP (0.067 ± 0.023%ID/cm-3) compared to [11C]BUP (0.436 ± 0.054%ID/cm-3). P-gp inhibition using Tariquidar increased the brain uptake of [11C]nor-BUP (0.557 ± 0.077%ID/cm-3).

Synthesis, Biodistribution, and Radiation Dosimetry of a Novel mGluR5 Radioligand: 18F-AZD9272.

The metabotropic glutamate receptor subtype mGluR5 has been proposed as a potential drug target for CNS disorders such as anxiety, depression, Parkinson's disease, and epilepsy. The AstraZeneca compound AZD9272 has previously been labeled with carbon-11 and used as a PET radioligand for mGluR5 receptor binding. The molecular structure of AZD9272 allows one to label the molecule with fluorine-18 without altering the structure. The aim of this study was to develop a fluorine-18 analogue of AZD9272 and to examine its binding distribution in the nonhuman primate brain in vivo as well as to obtain whole body radiation dosimetry. 18F-AZD9272 was successfully synthesized from a nitro precursor. The radioligand was stable, with a radiochemical purity of >99% at 2 h after formulation in a sterile phosphate buffered solution (pH = 7.4). After injection of 18F-AZD9272 in two cynomolgus monkeys, the maximum whole brain radioactivity concentration was 4.9-6.7% of the injected dose (n = 2) and PET images showed a pattern of regional radioactivity consistent with that previously obtained for 11C-AZD9272. The percentage of parent radioligand in plasma was 59 and 64% (n = 2) at 120 min after injection of 18F-AZD9272, consistent with high metabolic stability. Two whole body PET scans were performed in nonhuman primates for a total of 231 min after injection of 18F-AZD9272. Highest uptakes were seen in liver and small intestine, followed by brain and kidney. The estimated effective dose was around 0.017 mSv/MBq. 18F-AZD9272 shows suitable properties as a PET radioligand for in vivo imaging of binding in the primate brain. 18F-labeled AZD9272 offers advantages over 11C-AZD9272 in terms of higher image resolution, combined with a longer half-life. Moreover, based on the distribution and the estimated radiation burden, imaging of 18F-AZD9272 could be used as an improved tool for quantitative assessment and characterization of AZD9272 binding sites in the human brain by using PET.

Pioglitazone Increases Blood-Brain Barrier Expression of Fatty Acid-Binding Protein 5 and Docosahexaenoic Acid Trafficking into the Brain.

Brain levels of docosahexaenoic acid (DHA), an essential cognitively beneficial fatty acid, are reduced in Alzheimer's disease (AD). We have demonstrated in an AD mouse model that this is associated with reduced blood-brain barrier (BBB) transport of DHA and lower expression of the key DHA-trafficking protein, fatty acid-binding protein 5 (FABP5). This study focused on assessing the impact of activating peroxisome proliferator-activated receptor (PPAR) isoforms on FABP5 expression and function at the BBB. Using immortalized human brain endothelial (hCMEC/D3) cells, a 72 h treatment with the PPARα agonist clofibrate (100 µM), and PPARß/δ agonists GW0742 (1 µM) and GW501506 (0.5 µM), did not affect FABP5 protein expression. In contrast, the PPARγ agonists rosiglitazone (5 µM), pioglitazone (25 µM), and troglitazone (1 µM) increased FABP5 protein expression by 1.15-, 1.18-, and 1.24-fold in hCMEC/D3 cells, respectively, with rosiglitazone and pioglitazone also increasing mRNA expression of FABP5. In line with an increase in FABP5 expression, pioglitazone increased 14C-DHA uptake into hCMEC/D3 cells 1.20- to 1.33-fold over a 2 min period, and this was not associated with increased expression of membrane transporters involved in DHA uptake. Furthermore, treating male C57BL/6J mice with pioglitazone (40 mg/kg/day for 7 days) led to a 1.79-fold increase in BBB transport of 14C-DHA over 1 min, using an in situ transcardiac perfusion technique, which was associated with a 1.82-fold increase in brain microvascular FABP5 protein expression. Overall, this study demonstrated that PPARγ can regulate FABP5 at the BBB and facilitate DHA transport across the BBB, important in restoring brain levels of DHA in AD.

Evaluation of absorption, distribution, metabolism, and excretion of [14C]-rucaparib, a poly(ADP-ribose) polymerase inhibitor, in patients with advanced solid tumors.

Rucaparib, a poly(ADP-ribose) polymerase inhibitor, is licensed for use in recurrent ovarian, fallopian tube, or primary peritoneal cancer. We characterized the absorption, distribution, metabolism, and elimination of rucaparib in 6 patients with advanced solid tumors following a single oral dose of [14C]-rucaparib 600 mg (≈140 µCi). Total radioactivity (TRA) in blood, plasma, urine, and feces was measured using liquid scintillation counting. Unchanged rucaparib concentrations in plasma were determined using validated liquid chromatography with tandem mass spectrometry. Maximum concentration (Cmax) of TRA and unchanged rucaparib in plasma was 880 ng Eq/mL and 428 ng/mL, respectively, at approximately 4 h post dose; terminal half-life was >25 h for both TRA and rucaparib. The plasma TRA-time profile was parallel to yet higher than that of rucaparib, suggesting the presence of metabolites in plasma. Mean blood:plasma ratio of radioactivity was 1.0 for Cmax and 0.8 for area under the concentration-time curve from time zero to infinity. Mean postdose recovery of TRA was 89.3% over 12 days (71.9% in feces; 17.4% in urine). Unchanged rucaparib and M324 (oxidative metabolite) were the major components in plasma, contributing to 64.0% and 18.6% of plasma radioactivity, respectively. Rucaparib and M324 were the major rucaparib-related components (each ≈7.6% of dose) in urine, whereas rucaparib was the predominant component (63.9% of dose) in feces. The high fecal recovery of unchanged rucaparib could be attributed to hepatic excretion and/or incomplete oral absorption. Overall, these data suggest that rucaparib is eliminated through multiple pathways, including metabolism and renal and biliary excretion.

Feasibility study of finalizing the extended adjuvant temozolomide based on methionine positron emission tomography (Met-PET) findings in patients with glioblastoma.

In the management of patients with newly diagnosed glioblastoma, there is no standard duration for adjuvant temozolomide treatment. This study aimed to assess the feasibility of finalizing adjuvant temozolomide treatment on the basis of methionine uptake in methionine positron emission tomography (Met-PET). We conducted a retrospective review of glioblastoma patients who underwent more than twelve cycles of temozolomide (extended temozolomide) treatment after resection and concomitant chemoradiotherapy with no evidence of recurrence on MRI. In addition to the methionine uptake value at the completion of extended temozolomide, local and distant recurrence and progression-free survival were also analyzed. Forty-four patients completed the extended temozolomide treatment. Among these, 18 experienced some type of tumor recurrence within one year. A Tmax/Nave value of 2.0 was the optimal cut-off value indicating progression. More than 80% of the patients with low methionine uptake completed the temozolomide treatment, and subsequent basic MRI observations showed no recurrence within one year after Met-PET. Subgroups with high uptake (≥2.0), even with continuation of temozolomide treatment, showed more frequent tumor progression than patients with low uptake (<2.0) who completed the extended temozolomide treatment (p < 0.001, odds ratio 14.7, 95% CI 3.46-62.3). The tumor recurrence rate increased in stepwise manner according to methionine uptake. Finalization of the extended temozolomide treatment on the basis of low uptake value was feasible with a low recurrence rate. Compared to MRI, Met-PET shows better ability to predict tumor progression in long-term glioblastoma survivors with extended temozolomide use.

Measurement of PET isotope production cross sections for protons and carbon ions on carbon and oxygen targets for applications in particle therapy range verification.

Measured cross sections for the production of the PET isotopes [Formula: see text], [Formula: see text] and [Formula: see text] from carbon and oxygen targets induced by protons (40-220 [Formula: see text]) and carbon ions (65-430 [Formula: see text]) are presented. These data were obtained via activation measurements of irradiated graphite and beryllium oxide targets using a set of three scintillators coupled by a coincidence logic. The measured cross sections are relevant for the PET particle range verification method where accurate predictions of the [Formula: see text] emitter distribution produced by therapeutic beams in the patient tissue are required. The presented dataset is useful for validation and optimization of the nuclear reaction models within Monte Carlo transport codes. For protons the agreement of a radiation transport calculation using the measured cross sections with a thick target PET measurement is demonstrated.

A Phase 1 Mass Balance Study of 14 C-Labeled Talazoparib in Patients With Advanced Solid Tumors.

This paper describes the pharmacokinetics (PK), mass balance, metabolic profiling, and safety of talazoparib after a single oral dose of 14 C-talazoparib in 6 patients with advanced solid tumors. Patients were aged ≥18 years, with a histologically confirmed advanced solid tumor at screening. A single 1-mg dose of talazoparib oral solution supplemented with 100 µCi of 14 C-labeled talazoparib was administered. Blood, urine, and feces samples were collected at various time points and analyzed for talazoparib and 14 C radioactivity. Metabolic profiling and identification were also carried out. Mean recovery of 14 C radioactivity was 68.7% in urine and 19.7% in feces. Talazoparib was minimally metabolized. Renal excretion of unchanged talazoparib was a major route of elimination, with mean recovery of 54.6% of the administered dose, whereas fecal excretion of talazoparib was limited, with mean recovery of 13.6% of the administered dose. No major metabolites of talazoparib were identified in plasma, and no metabolites that individually represented more than 10% of the administered dose were recovered in urine or feces. The concentration-time profiles of unchanged talazoparib, total 14 C radioactivity in plasma, and total 14 C radioactivity in whole blood were similar, with a median time at peak concentrations of 30 minutes and mean half-life of 89.8, 96.2, and 77.6 hours, respectively. Talazoparib was minimally metabolized, and renal excretion of unchanged talazoparib was the major route of elimination.

Apalutamide Absorption, Metabolism, and Excretion in Healthy Men, and Enzyme Reaction in Human Hepatocytes.

In this phase 1 study, the absolute bioavailability and absorption, metabolism, and excretion (AME) of apalutamide, a competitive inhibitor of the androgen receptor, were evaluated in 12 healthy men. Subjects received 240 mg of apalutamide orally plus a 15-minute intravenous infusion of 100 µg of apalutamide containing 9.25 kBq (250 nCi) of 14C-apalutamide (2 hours postdose) for absolute bioavailability assessment or plus one 400-µg capsule containing 37 kBq (1000 nCi) of 14C-apalutamide for AME assessment. Content of 14C and metabolite profiling for whole blood, plasma, urine, feces, and expired air samples were analyzed using accelerator mass spectrometry. Apalutamide absolute oral bioavailability was ≈100%. After oral administration, apalutamide, its N-desmethyl metabolite (M3), and an inactive carboxylic acid metabolite (M4) accounted for most 14C in plasma (45%, 44%, and 3%, respectively). Apalutamide elimination was slow, with a mean plasma half-life of 151-178 hours. The mean cumulative recovery of total 14C over 70 days postdose was 64.6% in urine and 24.3% in feces. The urinary excretion of apalutamide, M3, and M4 was 1.2%, 2.7%, and 31.1% of dose, respectively. Fecal excretion of apalutamide, M3, and M4 was 1.5%, 2.0%, and 2.4% of dose, respectively. Seventeen apalutamide metabolites and six main metabolic clearance pathways were identified. In vitro studies confirmed CYP2C8 and CYP3A4 roles in apalutamide metabolism.

Use of Isotope Tracers to Assess Lipid Absorption in Conscious Lymph Fistula Mice.

This protocol provides a comprehensive reference for the evolution of the lymph fistula model, the mechanism of lipid absorption, the detailed procedure for studying lipid absorption using the lymph fistula model, the interpretation of the results, and consideration of the experimental design. The lymph fistula model is an approach to assess the concentration and rate of a range of molecules transported by the lymph by cannulating lymph duct in animals. In this protocol, mice first undergo surgery with the implantation of cannulae in the duodenum and mesenteric lymph duct and are allowed to recover overnight in Bollman restraining cages housed in a temperature-regulated environment. To study in vivo lipid absorption, a lipid emulsion is prepared with labeled tracers, including [3 H]-triolein and [14 C]-cholesterol. On the day of the experiment, mice are continuously infused with lipid emulsion via the duodenum for 6 hr, and lymph is usually collected hourly. At the end of the study, gastrointestinal segments and their luminal contents are collected separately for determination of the digestion, uptake, and transport of exogenous lipids. © 2019 by John Wiley & Sons, Inc.

Improved radiosynthesis and preliminary in vivo evaluation of the 11C-labeled tetrazine [11C]AE-1 for pretargeted PET imaging.

Pretargeted nuclear imaging based on the ligation between tetrazines and nano-sized targeting agents functionalized with trans-cyclooctene (TCO) has recently been shown to improve both imaging contrast and dosimetry in nuclear imaging of nanomedicines. Herein, we describe the improved radiosynthesis of a 11C-labeled tetrazine ([11C]AE-1) and its preliminary evaluation in both mice and pigs. Pretargeted imaging in mice was carried out using both a new TCO-functionalized polyglutamic acid and a previously reported TCO-functionalized bisphosphonate system as targeting agents. Unfortunately, pretargeted imaging was not successful using these targeting agents in pair with [11C]AE-1. However, brain imaging in pig indicated that the tracer crossed the blood-brain-barrier. Hence, we suggest that this tetrazine scaffold could be used as a starting point for the development of pretargeted brain imaging, which has so far been a challenging task.

Brain glial activation in fibromyalgia - A multi-site positron emission tomography investigation.

Fibromyalgia (FM) is a poorly understood chronic condition characterized by widespread musculoskeletal pain, fatigue, and cognitive difficulties. While mounting evidence suggests a role for neuroinflammation, no study has directly provided evidence of brain glial activation in FM. In this study, we conducted a Positron Emission Tomography (PET) study using [11C]PBR28, which binds to the translocator protein (TSPO), a protein upregulated in activated microglia and astrocytes. To enhance statistical power and generalizability, we combined datasets collected independently at two separate institutions (Massachusetts General Hospital [MGH] and Karolinska Institutet [KI]). In an attempt to disentangle the contributions of different glial cell types to FM, a smaller sample was scanned at KI with [11C]-L-deprenyl-D2 PET, thought to primarily reflect astrocytic (but not microglial) signal. Thirty-one FM patients and 27 healthy controls (HC) were examined using [11C]PBR28 PET. 11 FM patients and 11 HC were scanned using [11C]-L-deprenyl-D2 PET. Standardized uptake values normalized by occipital cortex signal (SUVR) and distribution volume (VT) were computed from the [11C]PBR28 data. [11C]-L-deprenyl-D2 was quantified using λ k3. PET imaging metrics were compared across groups, and when differing across groups, against clinical variables. Compared to HC, FM patients demonstrated widespread cortical elevations, and no decreases, in [11C]PBR28 VT and SUVR, most pronounced in the medial and lateral walls of the frontal and parietal lobes. No regions showed significant group differences in [11C]-L-deprenyl-D2 signal, including those demonstrating elevated [11C]PBR28 signal in patients (p's ≥ 0.53, uncorrected). The elevations in [11C]PBR28 VT and SUVR were correlated both spatially (i.e., were observed in overlapping regions) and, in several areas, also in terms of magnitude. In exploratory, uncorrected analyses, higher subjective ratings of fatigue in FM patients were associated with higher [11C]PBR28 SUVR in the anterior and posterior middle cingulate cortices (p's < 0.03). SUVR was not significantly associated with any other clinical variable. Our work provides the first in vivo evidence supporting a role for glial activation in FM pathophysiology. Given that the elevations in [11C]PBR28 signal were not also accompanied by increased [11C]-L-deprenyl-D2 signal, our data suggests that microglia, but not astrocytes, may be driving the TSPO elevation in these regions. Although [11C]-L-deprenyl-D2 signal was not found to be increased in FM patients, larger studies are needed to further assess the role of possible astrocytic contributions in FM. Overall, our data support glial modulation as a potential therapeutic strategy for FM.