Purpose Angiogenesis plays an important role in the growth and metastatic spread of solid tumours and is characterised by the expression of integrins on the cell surface of endothelial cells. Radiolabelled RGD peptides specifically target angiogenesis-related α v β 3 integrins, expressed on the activated endothelial cells of sprouting blood vessels. Here, we validated the feasibility of 68 Ga[Ga]-DOTA-E-[c(RGDfK)] 2 ( 68 Ga-RGD) PET/CT to visualise angiogenesis in patients with oral squamous cell carcinoma (OSCC). Methods Ten patients with OSCC and scheduled for surgical resection including elective neck dissection received an intravenously administration of 68 Ga-RGD (42 ± 8 μg; 214 ± 9 MBq). All patients subsequently underwent dynamic ( n = 5) or static PET/CT imaging ( n = 5) for 60 min or for 4 min/bed position at 30, 60 and 90 min after injection, respectively. Quantitative tracer uptake in tumour lesions was expressed as standardised uptake values (SUV). Additionally, tumour tissue was immunohistochemically stained for α v β 3 integrin to assess the expression pattern. Results 68 Ga-RGD tumour accumulation was observed in all patients. At 60 min post injection, tumour SUV max ranged between 4.0 and 12.7. Tracer accumulation in tumour tissue plateaued at 10 min after injection. Uptake in background tissue did not change over time, resulting in tumour-to-muscle tissue of 6.4 ± 0.7 at 60 min post injection. Conclusions 68 Ga-RGD PET/CT of α v β 3 integrin expression in OSCC patients is feasible with adequate tumour-to-background ratios. It will provide more insight in angiogenesis as a hallmark of the head and neck squamous cell carcinomas’ tumour microenvironment. Trial registration https://eudract.ema.europa.eu no. 2015-000917-31

Ziel/Aim There is increasing evidence for residual, dysfunctional beta cells in patients with type 1 diabetes (T1D), but research is hampered by the lack of methods to quantify beta cell mass (BCM) in vivo in humans. Image-based quantification of BCM using radiolabeled exendin-4 might provide such a method.

The aim was to compare the prostate-specific membrane antigen (PSMA)-targeting characteristics of PSMA-11, radiolabeled on the basis of chelation of 18F-AlF, with those of 68Ga-PSMA-11 to image PSMA-expressing xenografts. Methods: Labeling of 18F-AlF-PSMA-11 via 18F-AlF-complexation was performed as described by Boschi et al. and Malik et al. with minor modifications. Several conditions for the quality control of the labeling of 18F-AlF-PSMA-11 via 18F-AlF-complexation were evaluated to characterize the influence of ethanol, acetonitrile, and trifluoroacetic acid on the stability of the labeled product. Internalization kinetics of 18F-AlF-PSMA-11 were compared with those of 68Ga-PSMA-11 using PSMA-expressing LNCaP tumor cells. Biodistribution of 18F-AlF-PSMA-11 (0.26 nmol/mouse, 8-9 MBq/mouse) in male BALB/c nude mice with PSMA-expressing subcutaneous LS174T-PSMA tumors was compared with that of 68Ga-PSMA-11 at 1 and 2 h after injection. In addition, 18F-AlF-PSMA-11 PET/CT and 68Ga-PSMA-11 PET/CT imaging were performed at 1 and 2 h after injection. Results: In contrast to 68Ga-PSMA-11, 18F-AlF-PSMA-11 was not stable in water (radiochemical purity was 64.5% immediately after purification and 52.7% at 120 min after purification). 18F-AlF-PSMA-11 remained relatively stable in 25 mM NH4OAc, pH 6.9, and radiochemical purity decreased from 98.5% at purification to 96.3%, 94.7%, and 92.5% at 60, 120, and 180 min after purification. In vitro, the 18F- and 68Ga-labeled compounds showed rapid internalization in LS174T-PSMA cells. The highest tumor uptake (percentage injected dose [%ID]) was observed at 2 h after injection (10.8 ± 2.3 %ID/g and 7.9 ± 1.3 %ID/g for 18F-AlF-PSMA-11 and 68Ga-PSMA-11, respectively [P > 0.05]). Renal tracer uptake peaked at 2 h after injection (43.5 ± 5.7 %ID/g and 105.8 ± 13.8 %ID/g for 18F-AlF-PSMA-11 and 68Ga-PSMA-11, respectively, P < 0.05). Bone uptake of 18F-AlF-PSMA-11 was 3.3 ± 0.6 at 1 h after injection and 5.0 ± 0.6 %ID/g at 2 h after injection and was dependent on the radiochemical purity at the time of injection. Bone uptake of 68Ga-PSMA-11 reached 0.1 ± 0.0 %ID/g at 1 and 2 h after injection. PSMA-expressing xenografts could be visualized using both 68Ga-PSMA-11- and 18F-AlF-PSMA-11 PET/CT. Conclusion: 18F-AlF-PSMA-11 using direct labeling with aluminum fluoride can be produced in NH4OAc, pH 6.9; shows a high internalization rate; and visualizes PSMA-expressing tumors with similar tumor uptake. Lower kidney uptake than with 68Ga-PSMA-11 may be advantageous for tumor detection. However, the limited instability and consequent Al18F uptake in bone might hamper the visualization of small PCa bone metastases.

Background Rheumatoid arthritis (RA) synovial tissue has been demonstrated to express high levels of fibroblast activation protein (FAP) using anti-FAP-antibody 28H1. In addition, RA patients show elevated levels of IL-22 and IL-22-producing T helper cells that correlate to erosive disease, suggesting a role for this cytokine in the pathogenesis of RA. Objectives The purpose of this study was to determine the feasibility of 111In-28H1 SPECT/CT imaging of FAP-expressing synovium to monitor the therapeutic potential of neutralizing IL-22 during experimental arthritis. Methods Collagen-induced arthritis (CIA) was induced in male DBA/1J mice. Mice were treated 3 times per week with anti-IL-22 antibodies (8 mg/kg), while the control group received rat IgG1 isotype control antibodies. To monitor the therapeutic effect after 2 weeks of treatment, SPECT/CT images were acquired 24 h after injection of 111In-labeled DTPA-conjugated anti-FAP antibody, 28H1. After image acquisition, mice were euthanized and dissected. Imaging results were compared with the macroscopic arthritis scores and radiographic bone damage scores acquired by X-ray. Results Blocking IL-22 during CIA was a potent approach to prevent arthritis development, reaching a disease incidence of only 50%, versus 100% in the control group. SPECT/CT imaging using indium-labeled anti-FAP antibodies showed that joint uptake of the tracer was reduced highly significant (p=0.002) in anti-IL-22-treated mice (4.3 ± 3.4%ID/g) compared to the isotype control group (12.7 ± 3.7%ID/g) (See figure). This was confirmed by the corresponding macroscopic arthritis scores and radiographic bone damage scores that were significantly (p=0.047 and p=0.017 respectively) lower in the anti-IL-22-treated group. Besides its sensitivity, the in vivo FAP-based SPECT/CT had the great advantage to visualize sites of inflammation that were overlooked during clinical scoring, like in knee, hip, elbow and shoulder (See figure). Conclusions These findings demonstrate that IL-22 plays an important role in the development of experimental arthritis, and targeting this cytokine seems an attractive new strategy in RA treatment. Most importantly, SPECT/CT imaging of the inflamed synovium using the labeled anti-FAP antibody 111In-DTPA-28H1 can be used to specifically monitor response to therapy in an objective and quantitative way, and is potentially more sensitive in disease monitoring compared to the standard method of clinical arthritis scoring by macroscopic inspection. Disclosure of Interest D. Roeleveld: None declared, T. van der Geest: None declared, T. Nayak Employee of: Roche, C. Klein Employee of: Roche, B. Walgreen: None declared, M. Helsen: None declared, M. Hegen Employee of: Pfizer, P. Laverman: None declared, O. Boerman: None declared, M. Koenders: None declared

1203 Objectives Despite improvements in diagnosis and therapy, prostate cancer remains a significant health problem in the Western world. Targeted photodynamic therapy (tPDT) potentially is a highly selective cancer treatment based on targeting molecules conjugated to photosensitizers, aiming at inducing cell death upon exposure to near-infrared (NIR) light following specific targeting of a fluorophore to the tumor cells. Here, the development and in vivo characterization of the triple-modality anti-PSMA targeting agent 111In-DTPA-D2B-IRDye700DX is described for both pre- and intra-operative tumor localization, image-guided surgery as well as for eradication of residual tumor tissue by tPDT. Methods The anti-PSMA monoclonal antibody, D2B, was conjugated with IRDye700DX and DTPA and subsequently radiolabeled with 111In. To determine the optimal dose and time point of NIR light irradiation, BALB/c nude mice with s.c. LS174T-PSMA xenografts received 3, 10, or 30 µg of the conjugate intravenously (8 MBq/mouse, n=5 per group), followed by µSPECT/CT and NIR fluorescence imaging at 24, 48, 72, and 168 h p.i. to assess the localization of the IRDye700DX conjugate in the tumor. Tumor growth and overall survival of 3 mice injected with 30 µg of the conjugate followed by 30 min of NIR light irradiation at 72 h p.i. was compared to mice that did not receive any treatment. Results Localization of the D2B-700DX conjugate in the PSMA-expressing tumors was clearly visualized both with SPECT/CT and NIR fluorescence imaging. Highest tumor accumulation of the conjugate was observed in mice that received 30 µg at 72 h p.i., which was confirmed by quantitative analysis of the SPECT data (73 ± 10% ID/g) and biodistribution studies at 168 h p.i. (52 ± 16% ID/g). tPDT with 30 µg of the tracer and irradiation at 72 h p.i. caused significant tumor growth inhibition compared to the tumor growth in control mice. Median survival in the treatment group was significantly improved from 12.6 to 23.3 days (p = 0.0339). Tumor lesions could be resected with image-guidance using intraoperative NIR fluorescence imaging. Conclusions This study provided proof-of-principle that 111In-DTPA-D2B-IRDye700DX enables pre- and intra-operative visualization of PSMA+ tumors with radionuclide and fluorescence imaging, image-guided surgery and PSMA-targeted PDT. Optimal tumor destruction was achieved at a conjugate dose of 30 µg and a NIR-light irradiation at 72 h after injection of the conjugate.

Background and objectives Monitoring response to therapy in arthritis is usually carried out by clinical assessment, ultrasonography, conventional radiography or MRI. Molecular imaging could be used to more specifically monitor therapy response, thus enabling tailored therapy regimens and enhancing therapeutic outcome. Here, we hypothesised that response to etanercept could be monitored by radionuclide imaging in arthritic mice. We tested three different targets namely fibroblast activation protein (FAP), F4/80-expressing macrophages, and integrin αvβ3. Materials and methods Male DBA/1J mice with collagen-induced arthritis were treated with etanercept. SPECT/CT (Single photon emission computed tomography/ X-ray computed tomography) scans were acquired at 1, 24 and 48 h after injecting 111In-RGD2 (integrin αvβ3), 111In-anti-F4/80-A3–1 (anti-murine macrophage antibody), or 111In-28H1 (anti-FAP antibody), respectively, with nonspecific controls included. Mice were dissected after the last scan and scans were analysed quantitatively and were correlated with macroscopic scoring. Results Experimental arthritis in DBA-1J mice was imaged with 111In-28H1 (anti-FAP), 111In-anti-F4/80-A3–1, and 111In-RGD2. Tracer uptake in joints correlated signifianty with arthritis score. Treatment decreased joint uptake of tracers; it decreased from 23 ± 15%ID/g, 8 ± 4%ID/g, 2 ± 1%ID/g to 11 ± 11%ID/g (p < 0.001), 4 ± 4%ID/g (p < 0.001), 1 ± 0.2%ID/g (p < 0.01) for 111In-28H1, 111In-anti-F4/80-A3–1, and 111In-RGD2, respectively. Arthritis-to-blood ratios (in mice with established arthritis) were higher for 111In-28H1 (5.5 ± 1), 111In-anti-F4/80-A3–1 (10.4 ± 4), and 111In-RGD2 (7.2 ± 1)than for control 111In-DP47GS (0.7 ± 0.5; p = 0.002), 111In-rat IgG2b (0.5 ± 0.2; p = 0.002), or co-injection of excess RGD2, (3.5), indicating specific uptake of all tracers in arthritic joints. Conclusions In conclusion, 111In-28H1, 111In-anti-F4/80-A3–1, and 111In-RGD2 can be used to specifically monitor therapy response in experimental arthritis at the molecular level. Not only does this highlight the originality of the studies carried out here, by targeting integrins, macrophages or FAP in preclinical models of arthritis, but also the novelty of assessing these tracers as tools to monitor therapy response. Further studies need to be carried out to determine whether these tracers could be used for early diagnosis of arthritis as well as whether they can be used to monitor response to other types of therapies.