High Affinity and FAP-Targeted Radiotracers: A Potential Design Strategy to Improve the Pharmacokinetics and Tumor Uptake for FAP Inhibitors.

Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts, making it an attractive target for both imaging and therapy of malignancy. This study presents a range of novel FAP inhibitors derived from amino derivatives of UAMC1110, incorporating polyethylene glycol and bulky groups containing bifunctional DOTA chelators. The compounds labeled with gallium-68 were developed and characterized to study biodistribution properties and tumor-targeting performance in nude mice bearing U87MG tumor xenografts. Several tracers of interest were screened due to the advantages in imaging and tumor-specific uptake. Positron emission tomography scans revealed that polyethylene glycol-modified 68Ga-3-3 had a rapid penetration within the neoplastic tissue and excellent tumor-to-background contrast. In a comparative biodistribution study, naphthalene-modified 68Ga-6-3 exhibited more significant tumor uptake (∼50% ID/g, 1 h p.i.) than 68Ga-3-3 and 10-fold higher than 68Ga-FAPI-04 under the same conditions. Remarkably, 68Ga-8-1, combining the two structural design strategies, obtains superior imaging performance.

The effects of novel macrocyclic chelates on the targeting properties of the 68Ga-labeled Gastrin releasing peptide receptor antagonist RM2.

BACKGROUND: The gastrin-releasing peptide receptor (GRPr) is a molecular target for the visualization of prostate cancer. Bombesin (BN) analogs are short peptides with a high affinity for GRPr. RM2 is a bombesin-based antagonist. It has been demonstrated that RM2 have superior in vivo biodistribution and targeting properties than high-affinity receptor agonists. This study developed new RM2-like antagonists by introducing the novel bifunctional chelators AAZTA5 and DATA5m to RM2. RESULTS: The effects of different macrocyclic chelating groups on drug targeting properties and the possibility of preparing 68Ga-radiopharmaceuticals in a kit-based protocol were investigated using 68Ga-labeled entities. Both new RM2 variants were labelled with 68Ga3+ resulting in high yields, stability, and low molarity of the ligand. DATA5m-RM2 and AAZTA5-RM2 incorporated 68Ga3+ nearly quantitatively at room temperature within 3-5 min, and the labelling yield for 68Ga-DOTA-RM2 was approximately 10% under the same conditions. 68Ga-AAZTA5-RM2 showed stronger hydrophilicity according to partition coefficient. Although the maximal cellular uptake values of the three compounds were similar, 68Ga-AAZTA5-RM2 and 68Ga-DATA5m-RM2 peaked more rapidly. Biodistribution studies showed high and specific tumor uptake, with a maximum of 9.12 ± 0.81 percentage injected activity per gram of tissue (%ID/g) for 68Ga-DATA5m-RM2 and 7.82 ± 0.61%ID/g for 68Ga-AAZTA5-RM2 at 30 min after injection. CONCLUSIONS: The conditions for complexation of DATA5m-RM2 and AAZTA5-RM2 with gallium-68 are milder, faster and require less amount of precursors than DOTA-RM2. Chelators had an evident influence on the pharmacokinetics and targeting properties of 68Ga-X-RM2 derivatives. Positively charged 68Ga-DATA5m-RM2 provided a high tumor uptake, high image contrast and good capability of targeting GRPr.

Predictors of As-Needed Ranibizumab Injection Frequency in Patients With Macular Edema Following Retinal Vein Occlusion.

PURPOSE: To evaluate spectral-domain optical coherence tomography (SD-OCT) biomarkers associated with ranibizumab injection frequency after 7 monthly doses in the prospective, multicenter SHORE study for macular edema due to retinal vein occlusion (RVO). DESIGN: Prospective phase IV clinical trial data. METHODS: Post hoc analysis of 95 patients who received 7 monthly doses of ranibizumab followed by either pro re nata (PRN) or nonrandomized monthly injections from months 7-15 in eyes with macular edema secondary to RVO. Baseline SD-OCT biomarkers assessed include central subfield thickness (CST), epiretinal membrane presence, intraretinal and subretinal fluid, hyperreflective foci, disorganization of retinal inner layers (DRIL), and disruption of the external limiting membrane, ellipsoid zone, or interdigitation zone. Univariate and multivariable regression analyses evaluated the association between SD-OCT biomarkers and ranibizumab injection frequency. RESULTS: Mean age of patients was 65.3 (SD, 12.7) years. Overall, 57.9% had BRVO/HRVO and 42.1% of eyes had CRVO. Mean BCVA improved (+17.5 [SD, 1.2] Early Treatment of Diabetic Retinopathy Study [ETDRS] letters) during the 7-month fixed dosing period, remaining stable from baseline (+20.1 [SD, 1.5] ETDRS letters) during the PRN phase from months 7-15. The mean number of PRN injections was 4.32 (SD, 2.35). On multivariate regression, greater baseline DRIL (ß = 0.021, P = .0275) and higher CST at month 3 (ß = 0.01, P < .001) were associated with a higher total number of PRN injections. CONCLUSION: Greater baseline DRIL and higher CST at 3 months after starting ranibizumab treatment are associated with more frequent ranibizumab injections in PRN-treated patients with macular edema due to RVO.

Improve the Biodistribution with Bulky and Lipophilic Modification Strategies on Lys-Urea-Glu-Based PSMA-Targeting Radiotracers.

Since prostate-specific membrane antigen (PSMA) is upregulated in nearly all stages of prostate cancer (PCa), PSMA can be considered a viable diagnostic biomarker and treatment target in PCa. In this study, we have developed five 68Ga-labeled PSMA-targeted tracers, 68Ga-Flu-1, 68Ga-Flu-2, 68Ga-9-Ant, 68Ga-1-Nal, and 68Ga-1-Noi, to investigate the effect of lipophilic bulky groups on the pharmacokinetics of PSMA inhibitors compared to 68Ga-PSMA-11 and then explore their in vitro and in vivo properties. 68Ga-labeled PSMA inhibitors were obtained in 88.53-99.98% radiochemical purity and at the highest specific activity of up to 20 MBq/µg. These compounds revealed a highly efficient uptake and internalization into LNCaP cells and increased over time. PET imaging and biodistribution studies were performed in mice bearing PSMA expressing LNCaP prostate cancer xenografts. All tracers enabled clear visualization of tumors in PET images with excellent tumor-to-background contrast. The biodistribution studies showed that all these radioligands were excreted mainly via the renal pathway. The in vivo biodistribution of 68Ga-Flu-1 revealed higher tumor uptake (40.11 ± 9.24 %ID/g at 2 h p.i.) compared to 68Ga-PSMA-11 (28.10 ± 5.96 %ID/g at 2 h p.i.). Both in vitro and in vivo experiments showed that chemical modification of the lysine fragment significantly impacts tumor-targeting and pharmacokinetic properties. Great potential to serve as new PET tracers for prostate cancer has been revealed with these radiotracers─68Ga-Flu-1 in particular.

LncRNA FTX promotes the malignant progression of colorectal cancer by regulating the miR-214-5p-JAG1 axis.

BACKGROUND: Long non-coding RNAs (lncRNAs) have recently been found to be vital regulators of various cancers, including colorectal cancer (CRC). It has been previously reported that the dysregulated expression of lncRNA Five prime to Xist (FTX) is involved in carcinogenesis. However, the role of lncRNA FTX in the progression of CRC is still unclear. METHODS: Fluorescence in situ hybridization (FISH) was used to detect the expression of lncRNA FTX and miR-214-5p in CRC tissues. Cell Counting Kit-8 assay, transwell assay, wound-healing assay, and proliferation assay were used to explore the function of lncRNA FTX in CRC cells. Quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and luciferase reporter assay were used to confirm the relationship between lncRNA FTX and miR-214-5p-jagged canonical Notch ligand 1 (JAG1). We further explored the role of lncRNA FTX in vivo using xenograft tumor assay. RESULTS: lncRNA FTX was found to be upregulated in CRC tissues by FISH. The downregulation of endogenous lncRNA FTX expression inhibited CRC cell proliferation, migration, and invasion. Mechanistically, lncRNA FTX sequestered miR-214-5p and thus released its repression on JAG1, driving the malignant progression of CRC. CONCLUSIONS: These findings give rise to a new perspective, the lncRNA FTX-miR-214-5p-JAG1 regulatory axis, in exploring the cancer-promoting mechanism of lncRNA FTX in CRC.

In vitro and in vivo comparative study of a novel 68Ga-labeled PSMA-targeted inhibitor and 68Ga-PSMA-11.

68Ga-radiolabeled small molecules that specifically target prostate-specific membrane antigen (PSMA) have been extensively investigated, and some of these tracers have been used in the diagnosis of prostate cancer via 68Ga-positron emission tomography (68Ga-PET). Nevertheless, current 68Ga-labeled radiotracers show only fair detection rates for metastatic prostate cancer lesions, especially those with lower levels of prostate specific antigen (PSA), which often occurs in the biochemical recurrence of prostate cancer. The goal of this study was to design and synthesize a new PSMA-targeted radiotracer, 68Ga-SC691, with high affinity for prostate cancer cells and excellent pharmacokinetics. To this end, structural optimization was carried out on the bifunctional group, target motif, and linker while the high affinity targeting scaffold remained. To explore its potential in the clinic, a comparative study was further performed in vitro and in vivo between 68Ga-SC691 and 68Ga-PSMA-11, a clinically approved tracer for PSMA-positive prostate cancer. SC691 was radiolabeled to provide 68Ga-SC691 in 99% radiolabeling yield under mild conditions. High uptake and a high internalization ratio into LNCaP cells were observed in in vitro studies. In vivo studies showed that 68Ga-SC691 had favorable biodistribution properties and could specifically accumulate on PSMA-positive LNCaP xenografts visualized by micro-PET/CT. This radiotracer showed excellent PET imaging quality and comparable, if not higher, uptake in LNCaP xenografts than 68Ga-PSMA-11.

Quantitative Fundus Autofluorescence in Rhesus Macaques in Aging and Age-Related Drusen.

Purpose: To employ quantitative fundus autofluorescence (qAF) imaging in rhesus macaques to noninvasively assess retinal pigment epithelial (RPE) lipofuscin in nonhuman primates (NHPs) as a model of aging and age-related macular degeneration (AMD). Methods: The qAF imaging was performed on eyes of 26 rhesus macaques (mean age 18.8 ± 8.2 years, range 4-27 years) with normal-appearing fundus or with age-related soft drusen using a confocal scanning laser ophthalmoscope with 488 nm excitation and an internal fluorescence reference. Eyes with soft drusen also underwent spectral-domain optical coherence tomography imaging to measure drusen volume and height of individual drusen lesions. The qAF levels were measured from the perifoveal annular ring (quantitative autofluorescence 8 [qAF8]) using the Delori grid, as well as focally over individual drusen lesions in this region. The association between qAF levels and age, sex, and drusen presence and volume were determined using multivariable regression analysis. Results: Mean qAF levels increased with age (P < 0.001) and were higher in females (P = 0.047). Eyes with soft drusen exhibited reduced mean qAF compared with age-matched normal eyes (P = 0.003), with greater drusen volume showing a trend toward decreased qAF levels. However, qAF levels are focally increased over most individual drusen (P < 0.001), with larger drusen appearing more hyperautofluorescent (R2 = 0.391, P < 0.001). Conclusions: In rhesus macaques, qAF levels are increased with age and female sex, but decreased in eyes with soft drusen, similar to human AMD. However, drusen lesions appear hyperautofluorescent unlike those in humans, suggesting similarities and differences in RPE lipofuscin between humans and NHPs that may provide insight into drusen biogenesis and AMD pathogenesis.

Long-term Evolution and Remodeling of Soft Drusen in Rhesus Macaques.

Purpose: To characterize the evolution and structure of soft drusen in aged rhesus macaques using in vivo multimodal retinal imaging and ex vivo histologic and ultrastructural analyses as a nonhuman primate model of early age-related macular degeneration (AMD). Methods: Multimodal imaging including fundus photography, spectral domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF) were used to characterize and track individual drusen lesions in 20 aged rhesus macaques (mean age 23.3 ± 2.7 years) with drusenoid lesions over 2 years, followed by semithin histologic analysis and transmission electron microscopy (TEM). Results: Although most drusen gradually increased in size, a portion spontaneously regressed or collapsed over 2 years. Histologic analyses showed that soft drusen exhibit hypertrophy and dysmorphia of overlying retinal pigment epithelium (RPE), as seen in early and intermediate AMD, but do not exhibit RPE atrophy, RPE migration, or photoreceptor degeneration characteristic of advanced AMD. Ultrastructure of soft drusen showed abundant lipid particles within Bruch's membrane and AMD-related basal linear deposits (BlinD) resembling those in human drusen. Conclusions: The dynamic remodeling, histologic findings, and ultrastructural features of soft drusen in aged rhesus macaques support nonhuman primates as an animal model of early AMD and reveal important insights into drusen biogenesis and AMD development.

Spectral-Domain OCT Predictors of Visual Outcomes after Ranibizumab Treatment for Macular Edema Resulting from Retinal Vein Occlusion.

PURPOSE: To evaluate spectral-domain (SD)-OCT features associated with baseline vision and visual outcomes in the prospective, multicenter Study Evaluating Dosing Regimens for Treatment with Intravitreal Ranibizumab Injections in Subjects with Macular Edema following Retinal Vein Occlusion (SHORE). DESIGN: Post hoc analysis of prospective clinical trial data. PARTICIPANTS: Two hundred two participants in the 15-month, phase 4 SHORE study comparing monthly versus pro re nata ranibizumab after 7 monthly doses in eyes with retinal vein occlusion (RVO) with macular edema. METHODS: Baseline SD-OCT images were assessed for (1) central subfield thickness (CST); (2) presence of vitreomacular adhesion, vitreomacular traction, or epiretinal membrane; (3) presence, location, and amount of intraretinal fluid or subretinal fluid (SRF); (4) presence, location, and amount of hyperreflective foci (HF); (5) disorganization of retinal inner layers (DRIL); and (6) disruption of external limiting membrane (ELM), ellipsoid zone (EZ), and interdigitation zone (IZ). Univariate and multivariate regression analyses were performed to evaluate the association of these features with baseline best-corrected visual acuity (BCVA) and change in BCVA after 7 monthly ranibizumab injections. MAIN OUTCOME MEASURES: Association of SD-OCT features with baseline BCVA and change in BCVA after 7 monthly ranibizumab injections. RESULTS: Before therapy, worse baseline BCVA was associated with ERM presence (P = 0.0045), thicker SRF (P = 0.0006), larger intraretinal cysts (P = 0.0015), and higher percentage of DRIL (P < 0.0001), percentage of ELM disruption (P < 0.0001), percentage of EZ disruption (P = 0.0003), and percentage of IZ disruption (P = 0.0018). In multivariate models, only percentage of ELM disruption independently impacted baseline BCVA (P < 0.0001). After 7 monthly ranibizumab injections, mean BCVA improved by 18.3±12.6 Early Treatment Diabetic Retinopathy Study letters in treated eyes. The only factors independently associated with BCVA gain after 7 monthly ranibizumab treatments were younger age (P < 0.0001) and worse baseline BCVA (P < 0.0001). CONCLUSIONS: Although SD-OCT features may be associated with presenting vision in eyes with macular edema and RVO, most eyes treated with ranibizumab achieve substantial vision gains, and only older age and better baseline BCVA limited visual improvements.