[18F]FDG and [18F]FES PET/CT Imaging as a Biomarker for Therapy Effect in Patients with Metastatic ER+ Breast Cancer Undergoing Treatment with Rintodestrant.

PURPOSE: PET with 16α-[18F]-fluoro-17ß-estradiol ([18F]FES) allows assessment of whole body estrogen receptor (ER) expression. The aim of this study was to investigate [18F]-fluorodeoxyglucose ([18F]FDG) and [18F]FES PET/CT imaging for response prediction and monitoring of drug activity in patients with metastatic ER-positive breast cancer undergoing treatment with the selective estrogen receptor downregulator (SERD) rintodestrant. EXPERIMENTAL DESIGN: In this trial (NCT03455270), PET/CT imaging was performed at baseline ([18F]FDG and [18F]FES), during treatment and at time of progression (only [18F]FES). Visual, quantitative, and mutational analysis was performed to derive a heterogeneity score (HS) and assess tracer uptake in lesions, in relation to the mutation profile. The primary outcome was progression-free survival (PFS). RESULTS: The HS and PFS in the entire group did not correlate (n = 16, Spearman's rho, P = 0.06), but patients with a low HS (< 25.0%, n = 4) had a PFS of > 5 months whereas patients with no [18F]FES uptake (HS 100.0%, n = 3) had a PFS of < 2 months. [18F]FES uptake was not affected by estrogen receptor 1 (ESR1) mutations. On-treatment [18F]FES PET/CT scans showed no [18F]FES uptake in any of the baseline [18F]FES-positive lesions. At progression, [18F]FES uptake remained blocked in patients scanned ≤ 1-2 half-lives of rintodestrant whereas it restored in patients scanned ≥ 5 days after end of treatment. CONCLUSIONS: Absence of ER expression on [18F]FES PET is a predictor for no response to rintodestrant. [18F]FES uptake during treatment and at time of progression is useful to monitor the (reversible) effect of therapy and continued mode of action of SERDs. See related commentary by Linden and Mankoff, p. 2015.

Biodistribution of 18F-FES in Patients with Metastatic ER+ Breast Cancer Undergoing Treatment with Rintodestrant (G1T48), a Novel Selective ER Degrader.

16α-18F-fluoro-17ß-estradiol (18F-FES) is a PET tracer characterizing the expression of the estrogen receptor (ER). Because therapy can interfere with the kinetics and biodistribution of 18F-FES, the aim of this study was to describe the biodistribution of 18F-FES in patients with metastatic ER-positive (ER+) breast cancer undergoing treatment with rintodestrant (G1T48), a novel selective ER degrader. Methods: Eight patients underwent 18F-FES PET/CT imaging at baseline, 4-6 wk during treatment with rintodestrant (interim), and after treatment. After intravenous administration of 200 MBq (±10%) of 18F-FES, a 50-min dynamic PET/CT scan of the thorax was obtained, followed by a whole-body PET/CT scan 60 min after injection. Blood samples were drawn for measuring whole blood and plasma activity concentration and the parent fraction of 18F-FES. Volumes of interest were placed in the aorta ascendens and in healthy tissues on both dynamic and whole-body PET scans. SUVs and target-to-blood ratios (TBRs) were calculated. Areas under the curve (AUCs) of input functions and time-activity curves were calculated as a measure of uptake in different regions. Results:18F-FES concentration in whole blood (and plasma) significantly (P < 0.05) increased at interim with median AUCs of 96.6, 116.6, and 110.3 at baseline, interim, and after treatment, respectively. In ER-expressing tissues, that is, the uterus and the pituitary gland, both SUV and TBR showed high 18F-FES uptake at baseline, followed by a decrease in uptake at interim (uterus: SUV -50.6% and TBR -58.5%; pituitary gland: SUV -39.0% and TBR -48.3%), which tended to return to baseline values after treatment (uterus: SUV -21.5% and TBR -37.9%; pituitary gland: SUV -14.2% and TBR -26.0%, compared with baseline). In other healthy tissues, tracer uptake remained stable over the 3 time points. Conclusion: The biodistribution of 18F-FES is altered in blood and in ER-expressing healthy tissues during therapy with rintodestrant. This indicates that rintodestrant alters the kinetics of the tracer, possibly affecting interpretation and quantification of 18F-FES uptake. Of note, 6 d or more after treatment with rintodestrant ended, the biodistribution returned to baseline values, consistent with recovery of ER availability after washout of the drug.

Diagnostic Performance of [18F]FDG PET in Staging Grade 1-2, Estrogen Receptor Positive Breast Cancer.

Positron emission tomography using [18F]fluorodeoxyglucose (FDG PET) potentially underperforms for staging of patients with grade 1-2 estrogen receptor positive (ER+) breast cancer. The aim of this study was to retrospectively investigate the diagnostic accuracy of FDG PET in this patient population. Suspect tumor lesions detected on conventional imaging and FDG PET were confirmed with pathology or follow up. PET-positive lesions were (semi)quantified with standardized uptake values (SUV) and these were correlated with various pathological features, including the histological subtype. Pre-operative imaging detected 155 pathologically verified lesions (in 74 patients). A total of 115/155 (74.2%) lesions identified on FDG PET were classified as true positive, i.e., malignant (in 67 patients) and 17/155 (10.8%) lesions as false positive, i.e., benign (in 9 patients); 7/155 (4.5%) as false negative (in 7 patients) and 16/155 (10.3%) as true negative (in 14 patients). FDG PET incorrectly staged 16/70 (22.9%) patients. The FDG uptake correlated with histological subtype, showing higher uptake in ductal carcinoma, compared to lobular carcinoma (p < 0.05). Conclusion: Within this study, FDG PET inadequately staged 22.9% of grade 1-2, ER + BC cases. Incorrect staging can lead to inappropriate treatment choices, potentially affecting survival and quality of life. Prospective studies investigating novel radiotracers are urgently needed.

Design and development of letrozole nanoemulsion: A comparative evaluation of brain targeted nanoemulsion with free letrozole against status epilepticus and neurodegeneration in mice.

The target of the current study is to formulate letrozole loaded nanoemulsion (LET-NE) for the direct nose to brain delivery to reduce peripheral effects of letrozole (LET). LET-NE is compared against intraperitoneally administered free LET in kainic acid (KA) induced status epilepticus (SE) in mice. LET loaded nanoemulsion (LET-NE) was prepared by aqueous microtitration method using Triacetin, Tween 80 and PEG-400 as the oil phase, surfactant, and co-surfactant. Nanoemulsion was studied for droplet size, polydispersity index (PDI), zeta potential, percentage transmittance, drug content, surface morphology. TEM images of developed formulation demonstrated spherical droplets with a mean diameter of 95.59 ±â€¯2.34 nm, PDI of 0.162 ±â€¯0.012 and zeta potential of -7.12 ±â€¯0.12 mV respectively. In in-vitro and ex-vivo drug release, LET-NE showed prolonged drug release profile as compared to suspension. SE was induced by KA (10 mg/kg, i.p.) in Swiss albino mice. Behavioral seizure monitoring, biochemical estimations, and histopathological examination were performed. The onset time of SE was significantly enhanced and % incidence of SE was reduced by intranasal administration of LET-NE as compared to KA and LET administered intraperitoneally. Biochemical estimations revealed that LET-NE effectively decreased levels of 17-ß estradiol while the levels of 5α-Dihydrotestosterone (5α-DHT) and 3α-androstanediol (3α-Diol) were significantly increased in the hippocampus. In cresyl violet staining LET-NE showed better protection of the hippocampus from neurotoxicity induced by KA as compared to LET. Also, in gamma scintigraphy of mouse brain, intranasal administration of nanoemulsion exhibited the presence of high concentration of LET. The study demonstrates the anticonvulsant and neuroprotective effect of LET-NE probably by inhibition of aromatization of testosterone into 17-ß estradiol, proconvulsant, and diverting the pathway into the synthesis of testosterone metabolites, 3α-Diol with known anticonvulsant and neuroprotective action. Brain targeting of LET-NE showed better anticonvulsant and neuroprotective action than LET.

Effect of escitalopram and carbidopa on bone markers in Wistar rats: a preliminary experimental study.

In view of the opposite effects of gut and brain serotonin in bone, the key role of Wnt ß/catenin pathway in osteoblastic proliferation and the controversial bony effects of selective serotonin reuptake inhibitors antidepressants, the present study investigated the effects of escitalopram alone and in combination with carbidopa (to block gut-derived serotonin) on markers of bone turnover and Wnt signaling and micro-CT in male Wistar rats. Escitalopram (2.0 mg/kg, p.o.) and carbidopa (10 mg/kg, p.o.) were administered daily for 40 days following which indicators of reduced (dickkopf-1, sclerostin), and increased (alkaline phosphatase) bone formation and bone resorption markers (receptor activator of nuclear factor κB ligand, tartrate-resistant acid phosphatase 5b) were determined. Our results indicated that escitalopram adversely affected bone as indicated by reduced bone formation and enhanced bone resorption. Further, the effects of escitalopram on bone formation were possibly mediated through gut serotonin while the mechanisms responsible for effects on resorption seem unrelated to gut serotonin. The promising effects of carbidopa on bone formation, as observed in our study, open up exciting possibilities for this drug requiring further investigations.

Pitavastatin ameliorates myocardial damage by preventing inflammation and collagen deposition via reduced free radical generation in isoproterenol-induced cardiomyopathy.

Pitavastatin inhibits 3 hydroxy 3 methyl glutaryl coenzyme A (HMGCoA) reductase enzyme, preventing cholesterol synthesis along with elevating high density apolipoprotein A1 (Apo-A1). The present study was designed to evaluate cardioprotective potential of pitavastatin at 1 mg/kg/day and 3 mg/kg/day dose for 14 days in low dose isoproterenol (ISO) (5 mg/kg/day for 7 consecutive days) induced myocardial damage. ISO administration induced significant reduction in endogenous antioxidant enzymes like reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and raised thiobarbituric acid reactive substances (TBARS) indicating activated lipid peroxidation. Along with this, a significant increase in level of cardiac injury biomarkers vie, creatine kinase (CK-MB), lactate dehydrogenase (LDH), aspartate amino transferase (AST), tumor necrosis factor (TNF-α) and transforming growth factor (TGF-ß) as well as brain natriuretic peptide (BNP). Histological examination also revealed marked myocardial tissue damage in ISO treated rats. However, pretreatment with pitavastatin (3 mg/kg/day) significantly maintained nearly normal levels of cardiac biomarkers and oxidant antioxidant status as well as lipid peroxidation in ISO induced MI rats. Cardiac histological assessment and infarct size assessment also showed marked reduction in myocardial architecture alteration including infarct size as well as collagen deposition by pitavastatin that strongly supported biochemical findings. These observations strongly corroborate that pitavastatin prevents myocardial damages via up regulation of endogenous oxidants along with its hypocholesterolemic activity.

Aromatase inhibition by letrozole attenuates kainic acid-induced seizures but not neurotoxicity in mice.

Evidence shows neurosteroids play a key role in regulating epileptogenesis. Neurosteroids such as testosterone modulate seizure susceptibility through its transformation to metabolites which show proconvulsant and anticonvulsant effects, respectively. Reduction of testosterone by aromatase generates proconvulsant 17-ß estradiol. Alternatively, testosterone is metabolized into 5α-dihydrotestosterone (5α-DHT) by 5α-reductase, which is then reduced by 3α-hydroxysteroid oxidoreductase enzyme (3α-HSOR) to form anticonvulsant metabolite 3α-androstanediol (3α-Diol), a potent GABAA receptor modulating neurosteroid. The present study evaluated whether inhibition of aromatase inhibitor letrozole protects against seizures and neuronal degeneration induced by kainic acid (KA) (10 mg/kg, i.p.) in Swiss albino mice. Letrozole (1 mg/kg, i.p.) administered one hour prior to KA significantly increased the onset time of seizures and reduced the% incidence of seizures. Pretreatment with finasteride, a selective inhibitor of 5α-reductase and indomethacin, a selective inhibitor of 3α-hydroxysteroid oxidoreductase enzyme (3α-HSOR), reversed the protective effects of letrozole in KA-induced seizures in mice. Microscopic examination using cresyl violet staining revealed that letrozole did not modify KA-induced neurotoxicity in the CA1, CA3 and DG region of the hippocampus. Letrozole treatment resulted in the reduced levels of 17-ß estradiol and elevated the levels of 5α-dihydrotestosterone (DHT) and 3α-Diol in the hippocampus. Finasteride and indomethacin attenuated letrozole-induced elevations of 5α-DHT and 3α-Diol. Our results indicate the potential anticonvulsant effects of letrozole against KA-induced seizures in mice that might be mediated by inhibiting aromatization of testosterone to 17ß-estradiol, a proconvulsant hormone and by redirecting the synthesis to anticonvulsant metabolites, 5α-DHT and 3α-Diol. Acute aromatase inhibition, thus, might be used as an adjuvant in the treatment of status epilepticus and can be pursued further.

Design, synthesis and evaluation of newer 5,6-dihydropyrimidine-2(1H)-thiones as GABA-AT inhibitors for anticonvulsant potential.

Several new 5,6-dihydropyrimidine-2(1H)-thione derivatives have been prepared and investigated for their potencies for anticonvulsant activity against maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) test in mice. The acute neurotoxicity was measured by rotarod test. Compounds 3c and 3l were found active in both of the animal models. Further, in vitro GABA-AT enzyme activity assay was carried out to investigate the possible mechanism of action through GABA-AT inhibition. The most potent compounds 3c and 3l showed inhibitory potency (IC50) of 18.42µM and 19.23µM, respectively. The molecular modeling was performed for all the synthesized compounds. The docking results were found in concordant with the observed animal studies.

Multiparametric Analysis of the Relationship Between Tumor Hypoxia and Perfusion with ¹8F-Fluoroazomycin Arabinoside and ¹5O-H2O PET.

UNLABELLED: (18)F-fluoroazomycin arabinoside ((18)F-FAZA) is a PET tracer of tumor hypoxia. However, as hypoxia often is associated with decreased perfusion, the delivery of (18)F-FAZA may be compromised, potentially disturbing the association between tissue hypoxia and (18)F-FAZA uptake. The aim of this study was to gain insight into the relationship between tumor perfusion and (18)F-FAZA uptake. METHODS: Ten patients diagnosed with advanced non-small cell lung cancer underwent subsequent dynamic (15)O-H2O and (18)F-FAZA PET scans with arterial sampling. Parametric images of both (15)O-H2O-derived perfusion (tumor blood flow [TBF]) and volume of distribution (V(T)) of (18)F-FAZA were generated. Next, multiparametric classification was performed using lesional and global thresholds. Voxels were classified as low or high TBF and (18)F-FAZA V(T), respectively. Finally, by combining these initial classifications, voxels were allocated to 4 categories: lowTBF-lowV(T), lowTBF-highV(T), highTBF-lowV(T), and highTBF-highV(T). RESULTS: A total of 13 malignant lesions were identified in the 10 patients. The TBF and (18)F-FAZA V(T) values (average ± SD) across all lesions were 0.45 ± 0.20 mL·cm(-3)·min(-1) and 0.94 ± 0.31 mL·cm(-3), respectively. The averages of all lesional median values for TBF and (18)F-FAZA V(T) were 0.37 ± 0.15 mL·cm(-3)·min(-1) and 0.85 ± 0.18 mL·cm(-3), respectively. Multiparametric analysis showed that classified voxels were clustered rather than randomly distributed. Several intralesion areas were identified where (18)F-FAZA V(T) was inversely related to TBF. On the other hand, there were also distinct areas where TBF as well as (18)F-FAZA V(T) were decreased or increased. CONCLUSION: The present data indicate that spatial variation of (18)F-FAZA uptake is not necessarily inversely related to TBF. This suggests that decreased TBF may result in flow-limited delivery of (18)F-FAZA. Areas with both high (18)F-FAZA uptake and high TBF values suggest that high (18)F-FAZA uptake, possibly suggesting hypoxia, may occur despite high TBF values. In conclusion, multiparametric evaluation of the spatial distributions of both TBF and (18)F-FAZA uptake may be helpful for understanding the (18)F-FAZA signal.