Selected abstracts from the World Molecular Imaging Congress 2025 meeting of the World Molecular Imaging Society.

WMIC 2025, Anchorage, Alaska, September 29th-October 3rd

Sponsorship: Publication of this supplement was funded by the World Molecular Imaging Society. All content was reviewed and approved by the 2025 WMIC Program Committee, which held full responsibility for the abstract selections. Presenting authors are bolded in the contributor lists.

GA101- Immunomodulatory Photoacoustic Nanoparticle-engineered Macrophages for Solid Cancer Immunotherapy and Longitudinal Monitoring

Seoyoon Song 1, Melissa Cadena1, Myeongsoo Kim1, Stanislav Emelianov1

1Georgia Institute of Technology, Atlanta, GA

Background: Reinforcing antitumor functions of macrophages, phagocytosis of cancer cells and secretion of inflammatory cytokines, can be a potent approach to treat solid tumors. Several strategies including CAR-macrophages and phagocytosis-enhanced macrophages (engineered via anti-CD47 antibody treatment) have been recently reported and have shown promise in preclinical models [1, 2]. However, these approaches lack mechanisms for monitoring transferred macrophages and assessing their therapeutic efficacy against tumors, limiting the ability to implement longitudinal therapeutic interventions throughout the treatment. Integrating imaging and contrast agents offers a possibility for real-time and non-invasive tracking of macrophages within the tumor microenvironment. Specifically, labeling macrophages with imaging contrast agents allows for longitudinal visualization of their migration, infiltration, and persistence in tumors, which could serve as an indicator of therapeutic response. Photoacoustic (PA) imaging is a technique that combines ultrasound and optical imaging by leveraging the light-to-sound conversion under laser irradiation of optical absorbers with high-intensity nanosecond laser pulses. PA imaging offers a powerful tool for real-time and noninvasive tracking of adoptively transferred cells.

Here, we propose a macrophage engineering strategy for PA image-guided cancer immunotherapy. A nanoparticle formulation with both PA contrast and immunomodulatory effects is synthesized. Macrophages labeled with the formulated nanoparticles demonstrated strong antitumoral phenotypes and allowed longitudinal PA imaging. Our work provides perspectives on engineering macrophages for image-guided cancer immunotherapy.

Methods: Macrophages were derived from murine bone marrow cells. Bone marrow cells were extracted from the femur and the tibia from 5 - 8 weeks old mice. The cells were cultured with 20 ng/mL M-CSF for differentiation into macrophages. The hyperbranched gold nanoconstructs (HBGNCs) were synthesized via surface-blocker assisted seeded growth. Briefly, the surface of 35 nm-sized gold nanospheres was partially blocked during the seeded growth to yield the hyperbranched structure with a construct dimension of 100 nm.

For PA imaging, macrophages were labeled with HBGNCs. Afterwards, cells were washed with PBS and collected. The cell solution was embedded in gelatin phantom. The phantom was submerged in water and imaged under Vevo2100/LAZR imaging system.

The effect of particle labeling on key cellular functions, such as viability, migration, and antitumoral functions (CD80, CD87, MHCII, and CD206 expression), was investigated by confocal microscopy and flow cytometry.

Results: Photostable HBGNCs with high optical absorption efficiency, ~90% in the near-infrared I (NIR I) region, were synthesized. The enhanced optical absorption was attributed to the hyper-branched structure. Due to the enhanced optical responses at NIR I region, the HBGNCs produced robust photoacoustic (PA) responses at corresponding wavelengths, offering high sensitivity in PA imaging. When macrophages were labeled with HBGNCs, the size and the granularity of the cells increased as the particles were internalized. The labeling did not affect the viability of the cells. HBGNC-labeled macrophages embedded in tissue-mimicking phantoms yielded high PA signal.

The migration ability of the labeled macrophages was evaluated. Compared to IFNg-primed macrophages that are known to migrate at a high rate, macrophages labeled with either HBGNCs or HBGNC-Gs displayed a superior migration ability.

The phenotype of macrophages became more strongly anti-tumoral when labeled with IFNg-conjugated HBGNCs (HBGNC-Gs) compared to HBGNC and IFNg alone. This was supported by the increased expression of costimulatory receptors CD80 and CD86, MHCII, and the decreased expression of pro-tumoral marker CD206.

Conclusion: In the current study, a new strategy of macrophage engineering for cancer immunotherapy was introduced. Labeling macrophages with HBGNC-Gs have enabled PA imaging of macrophages and, at the same time, enhanced their migration ability and antitumoral phenotype. Results suggest that HBGNC labeling approach can provide insights into developing strategies for macrophage-based cancer immunotherapy.

Disclosures: The authors have no conflicts of interest to disclose.

1. Klichinsky, M. et al. Human chimeric antigen receptor macrophages for cancer immunotherapy. Nat Biotechnol 38, 947–953 (2020) 2. Dooling, L.J. et al. Cooperative phagocytosis of solid tumors by macrophages triggers durable anti-tumor responses. Nat. Biomed. Eng 7, 1081–1096 (2023).

3. Kubelick, K.P. et al. In Vivo Ultrasound and Photoacoustic Imaging of Nanoparticle-Engineered T Cells and Post-Treatment Assessment to Guide Adoptive Cell Immunotherapy. ACS Nano 19(6), 6079–6094 (2025)

4. Kim, M. et al. Hyper-Branched Gold Nanoconstructs for Photoacoustic Imaging in the Near-Infrared Optical Window. Nano Lett 23(20) 9257–9265 (2023)

GA105- Deuterium Metabolic Imaging Interrogates the Histone H3K27M Mutation and Provides an Early Readout of Response to Therapy in Diffuse Midline Gliomas

Georgios Batsios 1, Celine Taglang1, Suresh Udutha1, Anne Marie Gillespie1, Simon Robinson2, Timothy Phoenix3, Sabine Mueller1, Sriram Venneti4, Carl Koschmann4, Pavithra Viswanath1

1University of California, San Francisco, CA, 2The Institute of Cancer Research, United Kingdom, 3University of Cincinnati, 4University of Michigan Medical School

Background: Diffuse midline gliomas (DMGs) are lethal primary brain tumors in children that are driven by recurrent lysine 27 to methionine mutations in histone H3 (H3K27M). Long-term survival still remains <1 year after diagnosis. Radiation is the standard of care, but overall survival remains <1 year after initial diagnosis1–4. The imipridones ONC201 and ONC2065,6 have emerged as promising therapies for DMG patients. Although magnetic resonance imaging (MRI) is the mainstay for patient management, it does not reliably assess response to therapy7. Deuterium metabolic imaging (DMI) has emerged as a clinically translatable method of monitoring metabolic fluxes in vivo. DMI of [6,6’-2H]-glucose metabolism has been used to quantify flux to lactate and glutamate and/or glutamine in preclinical models and adult glioblastoma patients8–11. Therefore, the goal of this study was to identify metabolic alterations induced by H3K27M that can be leveraged for non-invasive metabolic imaging of DMGs.

Methods: Cell models: Patient derived (BT245, SF8628, DIPG-6, DIPG-XIII, QCTB-R059) and murine syngeneic (24-B7, 24-C2) cell lines were cultured as described previously12–16. 2H-MRS in live cells: Cells were incubated with media containing 25mM [6,6’-2H]-glucose for 72h17. Cells were treated with sgRNA against H3K27 mutation, irradiation (10Gy), ONC201 (10μΜ) or ONC206 (500nΜ). 2H-MR spectra were acquired from a live cell suspension on a 600MHz NMR spectrometer. Data analysis was performed using MestReNova17.

Intracranial tumor implantation: DMG cells were intracranially injected into the cortex or pons of SCID mice or nude rats17,18. Animals were randomized and treated with vehicle or ONC206 (25mg/kg, twice daily) via intraperitoneal injection or irradiation (2Gy/day).

In vivo 2H-MRS: Data was acquired using a 16mm 2H surface coil on a 3T or 9.4T Bruker scanner17. Following intravenous (2gr/kg) or intraperitoneal (2.5gr/kg) administration of [6,6’-2H]-glucose, 2H-MR spectra were acquired with a two-dimensional chemical shift imaging (CSI) sequence with a temporal resolution of 8 minutes 30 seconds (3T) or 5min 13s (9.4T). Data were analyzed using in-house Matlab code17.

Statistical analysis: All results are expressed as mean ± standard deviation. Unpaired two-tailed Welch's t-test was used to assess the statistical significance of differences (p<0.05 considered significant).

Results: DMI-detectable lactate production from [6,6’- 2H]-glucose is linked to the H3K27M mutation and provides a readout of response to therapy in vitro: [6,6’-2H]-glucose was able to detect reduction in 2H-lactate production in patient-derived H3K27M mutant cells and differentiate syngeneic isogenic cells differing only on the H3K27M mutation (wild type: 24-D3 vs mutant: 24-B7) (Panel A-C). Furthermore, 2H-lactate production was significantly reduced in patient-derived H3K27M mutant cells after targeted therapy or radiotherapy (Panel D-F).

DMI enables visualization of the metabolically active tumor lesion in preclinical DMG models: Lactate SNR was elevated in the tumor relative to the normal brain (Panel G-H).

Lactate is a quantitative imaging biomarker of response to chemotherapy in preclinical DMG models: As shown in Panel I, lactate production from [6,6’-2H]-glucose in the pontine tumor was reduced at day 7 of treatment with ONC206. Furthermore, spatial mapping of [6,6’-2H]-glucose metabolism by 2D CSI at 3T showed reduced 2H-lactate production in mice bearing cortical tumor after 3 days of irradiation compared to untreated controls (Panel J).

Conclusion: Collectively, our studies link the H3K27M mutation with elevated glycolysis and identify [6,6’-2H]-glucose as a novel contrast agent for visualizing the metabolically active lesion and for imaging early response to therapy in DMGs in vivo. Clinical translation of our studies will provide physicians with a much-needed tool to determine whether DMG patients are responding to standard and experimental therapies under development.

ACKNOWLEDGEMENTS: This study was supported by ChadTough Defeat DIPG Foundation Game Changer grant P056774, Violet Foundation for Pediatric Brain Cancer and National Institutes of Health grants R21CA289565 and R01CA292674. The authors would like to acknowledge the support of National Institutes of Health grant S10OD030256.

Disclosures: The authors have no conflicts of interest to disclose.

1. Fangusaro J, Bandopadhayay P. Advances in the classification and treatment of pediatric brain tumors. Curr Opin Pediatr. 2021; 33(1):26–32.

2. Fangusaro J. Pediatric high grade glioma: a review and update on tumor clinical characteristics and biology. Frontiers in oncology. 2012; 2:105.

3. Gallitto M, Lazarev S, Wasserman I, et al. Role of Radiation Therapy in the Management of Diffuse Intrinsic Pontine Glioma: A Systematic Review. Adv Radiat Oncol. 2019; 4(3):520–531.

4. Jovanovich N, Habib A, Head J, Hameed F, Agnihotri S, Zinn PO. Pediatric diffuse midline glioma: Understanding the mechanisms and assessing the next generation of personalized therapeutics. Neuro-Oncology Advances. 2023; 5(1):vdad040.

5. Allen JE, Kline CL, Prabhu VV, et al. Discovery and clinical introduction of first-in-class imipridone ONC201. Oncotarget. 2016; 7(45):74380–74392.

6. Bonner ER, Waszak SM, Grotzer MA, Mueller S, Nazarian J. Mechanisms of imipridones in targeting mitochondrial metabolism in cancer cells. Neuro Oncol. 2021; 23(4):542–556.

7. Cooney TM, Cohen KJ, Guimaraes CV, et al. Response assessment in diffuse intrinsic pontine glioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group. Lancet Oncol. 2020; 21(6):e330-e336.

8. Taglang C, Batsios G, Mukherjee J, et al. Deuterium magnetic resonance spectroscopy enables noninvasive metabolic imaging of tumor burden and response to therapy in low-grade gliomas. Neuro Oncol. 2022; 24(7):1101-1112.

9. De Feyter HM, Behar KL, Corbin ZA, et al. Deuterium metabolic imaging (DMI) for MRI-based 3D mapping of metabolism in vivo. Sci Adv. 2018; 4(8):eaat7314.

10. Bøgh N, Vaeggemose M, Schulte RF, Hansen ESS, Laustsen C. Repeatability of deuterium metabolic imaging of healthy volunteers at 3 T. Eur Radiol Exp. 2024; 8(1):44.

11. Khan AS, Peterson KA, Vittay OI, et al. Deuterium Metabolic Imaging of Alzheimer Disease at 3-T Magnetic Field Strength: A Pilot Case-Control Study. Radiology. 2024; 312(1):e232407.

12. Hashizume R, Smirnov I, Liu S, et al. Characterization of a diffuse intrinsic pontine glioma cell line: implications for future investigations and treatment. J Neurooncol. 2012; 110(3):305–313.

13. Green AL, Ramkissoon SH, McCauley D, et al. Preclinical antitumor efficacy of selective exportin 1 inhibitors in glioblastoma. Neuro-Oncology. 2015; 17(5):697–707.

14. Krug B, De Jay N, Harutyunyan AS, et al. Pervasive H3K27 Acetylation Leads to ERV Expression and a Therapeutic Vulnerability in H3K27M Gliomas. Cancer Cell. 2019; 35(5):782–797.e788.

15. Patel SK, Hartley RM, Wei X, et al. Generation of diffuse intrinsic pontine glioma mouse models by brainstem-targeted in utero electroporation. Neuro Oncol. 2020; 22(3):381–392.

16. du Chatinier A, Meel MH, Das AI, et al. Generation of immunocompetent syngeneic allograft mouse models for pediatric diffuse midline glioma. Neurooncol Adv. 2022; 4(1):vdac079.

17. Batsios G, Taglang C, Tran M, et al. Deuterium Metabolic Imaging Reports on TERT Expression and Early Response to Therapy in Cancer. Clin Cancer Res. 2022; 28(16):3526-3536.

18. Batsios G, Viswanath P, Subramani E, et al. PI3K/mTOR inhibition of IDH1 mutant glioma leads to reduced 2HG production that is associated with increased survival. Sci Rep. 2019; 9(1):10521.

GA106- Pharmacological Evaluation of Anti-PSMA [89Zr-DFO]5D3 Antibody-theranostic Conjugates by PET-CT and PET-MRI

Sudath Hapuarachchige 1, Santosh K. Yadav1, Catherine Foss1, Cyril Barinka2, Dmitri Artemov1

1Johns Hopkins University, Baltimore, MD, 2Institute of Biotechnology of the Czech Academy of Sciences, Vestec, Czech Republic

Category: New Chemistry, Materials & Probes

Background: Antibody-drug conjugates (ADCs) can be integrated with optical, nuclear, and MR imaging agents and used as antibody-theranostic conjugates (ATCs). This strategy provides non-invasive imaging information essential in optimizing, diagnosing, and measuring treatment response for drug development and therapy. 5D3-DM1 and 5D3-MLN8237 ADCs have shown enhanced therapeutic efficacy in PSMA (+) PC using preclinical animal models. [2–4] Anti-PSMA and centrosome targeting 5D3 mAb directly delivers anti-tubulin agent, DM1, or Aurora A kinase inhibitor, MLN8237, to centrosomes where these targeted proteins are primarily active. In this study, we radiolabeled these 5D3-DM1 and 5D3-MLN8237 ADCs with 89Zr to develop [89Zr-DFO]5D3-DM1 (Figure 1A-a) and [89Zr-DFO]5D3-MLN8237 (Figure 1A-b) and conducted an image-guided pharmacological evaluation study using a PET-CT and hybrid PET-MRI. We hypothesized that [89Zr-DFO]5D3-DM1 and [89Zr-DFO]5D3-MLN8237 provide unchanged therapeutic properties upon radiolabeling and can be used for the non-invasive pharmacological evaluation by PET-CT and PET-MRI imaging techniques (Figure 1B).

Methods: For radiolabeling, ADCs were first conjugated with deferoxamine (DFO) ligand and labeled with 89Zr using 89Zr oxalate, 89Zr(C2O4)2– (t1/2 = 78.4 h) to obtain [89Zr-DFO]5D3-DM1 and [89Zr-DFO]5D3-MLN8237, respectively (Figure 1A). The preclinical pharmacological evaluation was conducted in PSMA (+/-) bilateral dual tumor xenograft mouse models (n=5). Mice were administered with [89Zr-DFO]5D3-DM1 or [89Zr-DFO]5D3-MLN8237 (250 μCi, 10 mg/kg total protein dose in 200 μL of sterile saline, ∼1 mCi/mg specific activity) on day 1. PET-CT or PET-MRI imaging experiments were conducted at 4, 24, 48, 72, 96, and 144 h post-injection time points (Figure 1C). In the DCE-MRI study, mice were injected with Gd-DTPA (0.1 mg/kg) on days 1 and 6, and the DCE-MRI study was performed by measuring the T1 contrast enhancement and area under the curve (AUC). Animals in ex vivo biodistribution (BD) study groups were euthanized on days 3 and 6. Tumor tissues and vital organs were excised, and g-activity was measured using a Perkin Elmer g-counter. Organ and tissue samples were evaluated for necrosis, toxicological effects, and morphological changes after H&E staining.

Results: We successfully radiolabeled 5D3-DM1 and MLN-8237 and synthesized [89Zr-DFO]5D3-DM1 and [89Zr-DFO]5D3-MLN8237 for this theranostic study. The whole-body PET-CT images of mice treated with [89Zr-DFO]5D3-DM1 show significantly higher targeted tumor uptake in PSMA (+) tumors compared to the PSMA (-) tumors at post-injection time-points day 3 and 6 (Figure 1D-a). The ex vivo BD study (Figure 1D-b) confirmed this significant uptake in PSMA (+) tumors at day 3 (58%) and day 6 (59%) compared to the PSMA (-) tumors (*p<0.005). PET-MRI fused images demonstrated significantly higher tumor-specific uptake of [89Zr-DFO]5D3-MLN8237 at day 3 and day 6 post-injection time points by PSMA (+) tumors than PSMA (-) tumors (Figure 1E-a). In the same ex vivo BD study, [89Zr-DFO]5D3-MLN8237 also showed a significantly higher uptake by PSMA (+) tumors at day 3 (53%) and day 6 (46%), confirming the tumor specificity and enhanced therapeutic efficacy in PSMA (+) tumors (Figure 1E-b). At Day 6, higher necrosis and cell death in the tumor mass was confirmed by DCE-MRI in PSMA(+) tumors in mice treated with [89Zr-DFO]5D3-MLN8237 with 75% T1 enhancement (DT1) and 72% change in AUC (DAUC) in PSMA(+) tumors compared to the PSMA(-) control tumors with 59% (DT1) and 56% (DAUC), confirming higher necrosis in PSMA(+) tumors compared to PSMA(-) tumors upon treatment (Figure P1).

Conclusion: Radiolabeled anti-PSMA ATCs, [89Zr-DFO]5D3-DM1 and [89Zr-DFO]5D3-MLN8237, can be effectively utilized for image-guided pharmacological evaluations through non-invasive, translational, and clinically relevant PET-CT or PET-MRI techniques. These approaches can also be applied to other solid cancer therapies and drug delivery systems.

Disclosures: The authors have no conflicts of interest to disclose.

1. Ojha T, et al. Image-guided drug delivery: preclinical applications and clinical translation. Expert Opin Drug Deliv. 2015;12(8):1203-1207.

2. Huang CT, et al. Development of 5D3-DM1: A Novel Anti-Prostate-Specific Membrane Antigen Antibody-Drug Conjugate for PSMA-Positive Prostate Cancer Therapy. Mol Pharm. 2020; 7(9): 3392-3402.

3. Nováková Z, et al. Novel Monoclonal Antibodies Recognizing Human Prostate-Specific Membrane Antigen (PSMA) as Research and Theranostic Tools. The Prostate 2017; 77(7): 749–764.

4. Liatsou I, et al. Development and therapeutic evaluation of 5D3(CC-MLN8237)3.2 antibody-theranostic conjugates for PSMA-positive prostate cancer therapy. Front Pharmacol. 2024; 1;15:1385598.

GA108- Dynamic Functional MRI of Adipose Tissues Based on Endogenous Molecular CEST Contrasts

Kejia Cai1, Mehran Shaghaghi1

1University of Illinois Chicago, Chicago, IL

Category: Bioengineering, Synthetic Biology and Basic Biology

Background: Obesity prevalence has markedly increased worldwide in recent decades. Brown adipose tissue (BAT), when activated, induces thermogenesis that may counteract metabolic syndrome and obesity . However, a sensitive and non-invasive imaging method for in vivo mapping of BAT activity in both rodents and humans is lacking. In this study, we are developing a non-invasive dynamic molecular MRI approach based on the chemical exchange saturation transfer (CEST) contrasts to assess in vivo BAT activity.

Methods: The fat signal is conventionally treated as an artifact to be removed in CEST MRI research. We are taking an opposite and innovative route to utilize the fat signal in CEST Z-spectra. Rat and human Z-spectral MRI data were acquired on a 7T small-bore MRI and 3T whole-body MRI scanner, respectively by a CEST sequence with a pre-saturation pulse of 1.0 μT lasting 3 s, at a frequency range within ±10ppm plus a +300ppm reference, followed by a RARE (Rapid Acquisition with Relaxation Enhancement) readout. Z-spectral data were fitted to a multi-Lorentzian model to separately quantify the fat, water, creatine CEST (CrCEST at 2ppm), amide proton transfer (APT at 3.5ppm), and the semi-solid magnetic transfer (MT) effect from tissues. Both dynamic CrCEST and PET/CT imaging were used to visualize the dynamic changes in BAT activity in rats for up to 120 mins post the administration of CL 316, 243 (CL, a specific drug for BAT adrenergic activation, 1.0mg/kg, i.p.), as well as in humans after 2 hours of cold exposure.

Results: We have successfully extracted the molecular CEST contrasts from the Z-spectra of adipose tissues, including the CrCEST and APT (Fig. 1A). In rats, a single dose of CL 316, 243 triggered a robust elevation of CrCEST signal by dynamic CrCEST MRI (Fig. 1B-D), consistent with the 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and 1H-nuclear magnetic resonance (1H-NMR) measurements of creatine concentration in BAT (data not shown). Finally, CrCEST MRI detected cold-stimulated BAT activation in human subjects at a 3T clinical scanner, showing consistent findings with 18F-FDG PET/CT (data not shown).

Conclusion: Creatine promotes the release of a molar excess of ADP from mitochondria, which in turn promotes ATP regeneration through direct phosphorylation of ADP to drive substrate oxidation and thermogenesis. The results of this study supported CEST MRI as a promising endogenous, non-invasive, and radiation-free method for in vivo mapping of the metabolic function of adipose tissues. Dynamic CrCEST MRI may serve as a diagnostic and treatment-monitoring tool for functional MRI of metabolic diseases.

Disclosures: The authors have no conflicts of interest to disclose.

1. J. Wu et al., Beige adipocytes are a distinct type of thermogenic fat cell in mouse and human. Cell, vol. 150, no. 2, pp. 366-76, Jul 20 2012.

2. E. T. Chouchani, L. Kazak, and B. M. Spiegelman, New Advances in Adaptive Thermogenesis: UCP1 and Beyond. Cell Metab, vol. 29, no. 1, pp. 27–37, Jan 8 2019.

GA116- Proton Exchange Rate (kₑₓ) Increase Due to Reactive Oxygen Species Can Be Detected with Chemical Exchange Saturation Transfer (CEST) MRI

Mehran Shaghaghi 1, Kejia Cai1

1University of Illinois Chicago, Chicago, IL

Category: New Chemistry, Materials & Probes

Background: Our goal is to develop an endogenous MRI contrast method for molecular imaging of tissue reactive oxygen species (ROS), key biomarkers of oxidative stress and diseases such as inflammation, cancer, and diabetes. Endogenous MRI techniques for detecting ROS have valuable applications in both research and clinical settings. Previous studies have shown that ROS can increase the proton exchange rate (kₑₓ) in CEST experiments via an oxidation-catalyzed mechanism, as demonstrated in vitro and in a rotenone-treated mouse model. Earlier experiments revealed that hydroxyl radicals generated through Fenton reactions in H₂O₂-treated egg white phantoms increased kₑₓ and reduced relaxation times, particularly T₁. To further validate the effect of ROS on proton exchange, we investigated whether ROS affects the exchange rate of a small molecule with known CEST contrast, such as creatine.

Methods: Creatine samples were mixed with H₂O₂ at 0, 0.025, 0.10, and 0.25 v/v% (0, 8.1, 32.4, and 80.9 mM). The Fenton reaction (Fe²⁺ + H₂O₂ → Fe³⁺ + OH⁻ + ·OH) was initiated by adding a small amount of egg white, which contains natural iron, to generate hydroxyl radicals (the ROS species under study). Samples were scanned at 9.4 Tesla using CEST MRI at 20°C, with 1 μT saturation power and 4 s saturation time. T₁ and T₂ maps, as well as CEST Z-spectra, were acquired within one hour of H₂O₂ addition. To assess ROS effects on CEST contrast, we quantified the linewidth of the creatine CEST peak by fitting Z-spectra to Lorentzian functions. Given that CEST peak linewidth is affected by exchange rate, relaxation times, and saturation parameters, we examined linewidth variations in relation to ROS levels.

Results: We hypothesized that ROS enhances proton exchange via an oxidation-catalyzed mechanism, independent of the base-catalyzed route, by promoting proton abstraction from metabolites exchanging with water (Fig. A). An in vivo mouse brain MRI study, conducted before and after rotenone treatment, showed increased kₑₓ due to ROS overproduction (Fig. B). In our phantom study, increased ROS levels led to creatine CEST peak broadening. An inverted Z-spectrum comparing 8.1 and 80.9 mM H₂O₂-treated phantoms shows peak broadening (Fig. C). Increasing H₂O₂ concentrations correlated with reductions in T₁ (from 3.0 to 2.6 s) and T₂ (from 0.25 to 0.11 s), while CEST linewidth increased from 309 to 435 Hz (Fig. D). Numerical simulations using two-pool Bloch-McConnell models showed that increasing T₁, T₂, or kₑₓ independently broadens the CEST peak. However, since experimental T₁ and T₂ values decreased, we concluded that the linewidth broadening was primarily due to increased exchange rate, supporting our hypothesis.

Conclusion: Confirming earlier findings that ROS promotes proton exchange in egg white samples, this study further demonstrates that ROS enhances exchange in a small-molecule metabolite, as observed through CEST peak broadening. These results support the use of endogenous CEST MRI to non-invasively detect ROS and oxidative stress in tissues, offering potential in both preclinical and clinical applications. Acknowledgement: The research is supported by the National Institutes of Health (NIH) under award numbers R01DK135722 and R01CA283548.

Disclosures: The authors have no conflicts of interest to disclose.

1. Tain RW, Scotti AM, Cai K. J Magn Reson Imaging. 2019;50(2):583–91.

2. Tain RW, Scotti AM, Li W, Zhou XJ, Cai K. J Magn Reson Imaging. 2018;47(1):222–9.

3. Goerke S, Zaiss M, Bachert P. NMR Biomed. 2014;27(5):507–18.

4. Cai K, Singh A, Poptani H, et al. NMR Biomed. 2015;28(1):1–8.

5. Zaiss M, Jin T, Kim SG, Gochberg DF. NMR Biomed. 2022;35(11):e4789.

GA120- A Novel Research Platform Based on PET/MRI-Guided Focused Ultrasound for BBB Guiding and Opening

Fernando Lopez-Berenguer1, Andrea Gonzalez-Montoro1, Marta Freire1, Stuart S. Berr2, Mark Williams2, Natasha Sheybani2, Antonio J. Gonzalez1

1Institute for Instrumentation in Molecular Imaging, Valencia, Spain, 2University of Virginia, Charlottesville, VA

Category: Instrumentation

Background: Combining Positron Emission Tomography (PET) with Magnetic Resonance Imaging (MRI) and Focused Ultrasound (FUS) has emerged as a promising hybrid technique in the medical imaging field. Despite the potential benefits of using simultaneous PET and MRI acquisitions to monitor therapeutic effects and ensure precision and safety during FUS applications, neither commercial or academic PET/MRI-guided FUS system exists. This work presents the design, integration and evaluation of a preclinical PET insert for simultaneous operation with MRI and FUS systems.

Methods: The PET insert is based on monolithic LYSO crystals that define inner and outer diameters of 72 mm and 114 mm, respectively, with an axial length of 67 mm. The system performance was evaluated according to the NEMA protocol. The compatibility with MRI and FUS systems was done with both custom and commercial high-performance devices. A low-field 72 mT MRI and a custom transducer were tested in combination with the PET at the hospital La Fe in Valencia. The compatibility tests were done with a gelatin-based phantom, mixed with copper sulfate and FDG.

The PET was moved to the University of Virginia and tested with the high-field 9.4 T MRI (Bruker) and the RK-300 FUS device. Preliminary in-vivo mouse experiments on the opening of the brain blood barrier are also provided.

Results: The PET insert achieves a uniform spatial resolution of ~0.9 mm along the whole Field of View when enabling Depth of Interaction capabilities. Moreover, we found a sensitivity peak of 3.8% for an energy window of 250–750 keV and a peak noise equivalent count rate peak of 80 kcps at an activity of 19 MBq. The Recovery Coefficients, uniformity and Spill-Over-Ratios were obtained using the NEMA Image Quality phantom and found to be 0.31–0.89.31.89 (1 – 5 mm rods), 4.8% and, 11 – 22 (for air and water), respectively. These values are in good agreement with the ones reported by state-of-the-art preclinical PET systems. Moreover, the reconstructed images from a micro-Derenzo phantom resolved rods down to a size of 0.9 mm. The FUS sonication on the gelatin clearly showed the melting of this and the displacement of the FDG.

With the mouse tests, we observed 64Cu-DOTA radiotracer uptake increase at the FUS sonicated regions.

Conclusion: The compatibility of the PET insert with both low- and high-field MRI systems, as well as with custom and commercially available FUS devices, was studied using phantoms and in vivo experiments, respectively. The results of the trimodal tests have proven that the PET insert works simultaneously with both MRI and FUS systems. This is the first experimental validation of simultaneous molecular imaging (PET), combined with precise MR images and guided focused ultrasounds.

This platform allows for multiple new research scenarios, such as controlled opening of the brain blood barrier and drug delivery.

Disclosures: The authors have no conflicts of interest to disclose.

GA121- Biologic Dosing of Anti-EGFR Antibody Using a Preclinical Mouse Model Reveals Divergence of Plasma and Tumor Tissue Concentrations

Aviva S. Mattingly 1, Hidenori Tanaka1, Syeda Maria Ahmad Zaidi1, Michael Topf1, Eben L. Rosenthal1

1Vanderbilt University Medical Center, Nashville, TN

Background: Antibody dosing for human studies have been designed based on plasma levels or maximally tolerated dose – neither one of which are based on the molecular activity of the agent1,2. We leveraged the imaging properties of an optically labeled anti-EGFR antibody3 to investigate therapeutic dosing by studying the relationship between systemic dosing and tumor uptake of the drug in preclinical models. We expect that at sub-saturating doses, tumor concentration would correlate with plasma drug concentration, but hypothesized that there would be a threshold at which tissue concentration no longer increases despite increasing circulating plasma levels.

Methods: Panitumumab-IRDye800 (Pan800) was injected into FaDu and Cal27 xenograft models at escalating doses. FaDu tumors were harvested 3–9 days after injection and plasma was collected at the time of tumor removal; Cal27 tumors were all harvested at 3 days post injection based on maximum fluorescence timing. We evaluated macroscopic drug saturation in vivo and ex vivo using near-infrared (NIR) fluorescence. Plasma drug concentration and tumor tissue drug concentration was measured using fluorescence intensity of homogenized samples with a standard curve.

Results: Among FaDu xenograft models, the highest in vivo and ex vivo tumor fluorescence was measured 3 days after Pan800 injection. Mean fluorescence intensity (MFI) increased from 0.4 in the lowest dose group (10ug Pan800) to 6.2 in the highest dose group (200ug) at 3 days. At low doses, both tumor and plasma drug concentration increased with escalating doses, with tumor ranging from 0.04 ng/uL (10ug dose) to 0.27 ng/uL (200ug dose). Plasma increased from 1.3 ng/uL to 18.1 ng/uL, respectively. Plasma concentration was overall much higher than tissue concentrations in both FaDu and Cal27 models, and there was a strong correlation between plasma and tissue concentrations over the range of study doses (FaDu: r=0.95, p<0.0001, Cal27 r=0.94, p<0.0001). Despite this general correlation, there was a notable divergence in the trend of plasma concentration increase vs tumor concentration increase at the highest dose groups (100ug- 200ug). On day 3 when fluorescence was maximized, plasma revealed a predictable linear trend dependent on injected dose (r2=0.99) however tumor tissue showed a much weaker trend (Figure 1), driven by a plateau in values at the highest range (r2=0.84); this is represented by a significant difference in slope comparing both trends (P<0.0001). This pattern of plasma and tissue divergence remained true in Cal27 xenograft models at the same time point.

Conclusion: At low doses, plasma and tumor concentration of Pan800 show a similar pattern of increase with increasing injection dose. However, above 100ug dose, this trend diverges, with plasma continuing a strong linear curve with maximum dosing, while tissue concentration plateaus. This pattern was consistent across two HNSCC cell lines in mice and across varied timepoints 3–9 days post-infusion. Future dosing paradigms should consider this relationship especially at maximum tolerated doses that may not be proportionally increasing drug concentration in the targeted tumor.

Disclosures: The authors have no conflicts of interest to disclose.

1. Thall PF, Garrett-Mayer E, Wages NA, Halabi S, Cheung YK. Current issues in dose-finding designs: A response to the US Food and Drug Administration’s Oncology Center of Excellence Project Optimus. Clin Trials. Jun 2024;21(3):267–272. doi:10.1177/17407745241234652

2. Shah M, Rahman A, Theoret MR, Pazdur R. The Drug-Dosing Conundrum in Oncology - When Less Is More. N Engl J Med. Oct 14 2021;385(16):1445-1447. doi:10.1056/NEJMp2109826

3. Lee YJ, Krishnan G, Nishio N, et al. Intraoperative Fluorescence-Guided Surgery in Head and Neck Squamous Cell Carcinoma. Laryngoscope. Mar 2021;131(3):529–534. doi:10.1002/lary.28822

GA125- Sensitivity and Specificity of Detecting Premalignant Pancreatic Lesions In Vivo by Hyperpolarized Magnetic Resonance Imaging

Jose S. Enriquez 1, Rian Howell1, Olivereen Le Roux1, Shivanand Pudakalakatti1, Paytience Smith1, Muxin Wang1, Julia R. Zickus1, Prasanta Dutta1, Florencia McAllister1, Pratip Bhattacharya1

1University of Texas MD Anderson Cancer Center, Houston, TX

Background: Pancreatic cancer is one of the most difficult cancers to detect due to its asymptomatic presentation at early stages. Therefore, there is an unmet need for non-invasive imaging markers that identify the aggressive sub-type(s) of pancreatic lesions at an early time point in pancreatic cancer. One commonly used imaging biomarker is the conversion of hyperpolarized (HP) pyruvate to lactate.1 It has been previously demonstrated that at early timepoints of pancreatic cancer the Warburg effect sets in and promotes conversion to lactate. With metabolic HP-MR imaging, the conversion will be monitored between different premalignant models to determine the sensitivity of the imaging technique. Concurrently, the specificity of HP-MR for detecting premalignant lesions will be determined by imaging pancreatitis induced mice at different timepoints.

Methods: Hyperpolarized 1-13C Pyruvate MR was employed to study the metabolic processes in tamoxifen inducible genetically engineered mouse (GEM) models (P48CreERT2;LSL-KrasG12D (iKC)) with pre-invasive pancreatic intraepithelial neoplasia (PanIN) lesions, invasive pancreatic cancer model (P48CreERT2;LSL-KrasG12D; LSL-p53R172H (iKPC)) and control animals (P48CreERT2 (iC)). Similarly, inducible GEM model (p48-Cre; LSL-KrasG12D; Rosa26R-LSL-rtTA-TetO-GnasR201C) that develop premalignant cystic lesions (IPMN) that progresses to pancreatic cancer were placed on doxycycline diet (Dox+) for 15 weeks, a group of mice were given normal diet (Dox-) as control. Dissolution DNP (HyperSense, Oxford Instruments, UK) operating at 3T was utilized to hyperpolarize 1-13C pyruvate. The 13C MR spectra of hyperpolarized 1-13C pyruvate were acquired with the 7T Bruker MRI scanner (Figure 1)2 and lactate-to-pyruvate (Lac/Pyr) ratios were calculated. The PanIN mice were imaged at different time points in their lifespan, before tamoxifen induction, 10-, and 20-weeks post induction. The IPMN mice were imaged after 15 weeks of (Dox±) treatment. Simultaneously, wildtype, iC and iKC mice were treated with caerulein for three weeks for the development of pancreatitis and imaged 24 hours after the last caerulein injection.

Results: The Lac/Pyr ratio increased in the pancreatic cancer models (iKC and iKPC) compared to the control model. In the iKPC mouse model, at the 20-week post induction imaging a significant increase of the Lac/Pyr ratio (0.28±0.04) compared to the 10-week time point after induction (0.22±0.03) was observed. The 20-week iKPC time point ratio compared to the iKC and control mouse models was significantly higher, (0.28±0.04 compared to 0.23±0.03 and 0.22±0.02 respectively) indicating the invasive nature of the cancer. Even in the iKC model there is a slight increase of the lactate-to-pyruvate ratio at 20-weeks post induction (0.23±0.03) compared to both previous time points, pre-induction (0.21±0.02) and 10-week (0.22±0.03). (Figure 2) At the same time, mice that were treated with caerulein developed pancreatitis as demonstrated by tissue histology. Surprisingly, the lactate-to-pyruvate ratio remained constant in both iC and iKC mice that developed pancreatitis, around 0.15±0.03 for both groups, even with an inflamed pancreas. (Figure 3) In the wildtype mice with pancreatitis, the ratio did not increase compared to control mice with no pancreatitis, 0.16±0.01 and 0.19±0.05 respectively. Compared with mice developing premalignant lesions, the pancreatitis models exhibit lower ratios, indicating that the only factor increasing the ratio is the progression towards pancreatic cancer. These results suggest that 1-13C Pyruvate HP-MR metabolic imaging can specifically determine pancreatic cancer progression and is not influenced by known confounders such as pancreatitis. IPMN mice feed with doxycycline showed increase lactate-to-pyruvate ratio (0.43±0.05) compared to mice on normal diet (0.24±0.05).3

Conclusion: 1-13C Pyruvate HP-MR can detect metabolic shift to lactate in two different models of pancreatic cancer premalignancy representing two different pathways of pancreatic cancer progression. This finding can be potentially translated to the clinic for detection of pancreatic premalignant lesion in high-risk populations and assist physicians determine malignant lesions before progression to pancreatic cancer.

Disclosures: The authors have no conflicts of interest to disclose.

1. Dutta, P., Pando, S. C., Mascaro, M., et al. Early Detection of Pancreatic Intraepithelial Neoplasias (PanINs) in Transgenic Mouse Model by Hyperpolarized 13C Metabolic Magnetic Resonance Spectroscopy. International Journal of Molecular Sciences. 2020; 21(10), 3722.

2. Pudakalakatti, S., Raj, P., Salzillo, T. C., Enriquez, J. S., et al. Metabolic Imaging Using Hyperpolarization for Assessment of Premalignancy. In Cancer Immunoprevention. 2022; 169–180. Humana, New York, NY.

3. Makino, Y., Rajapakshe, K. I., Selvanesan, B. C., Okumura, T., Date, K., Dutta, P., ... Enriquez, J.S., et al. Metabolic reprogramming by mutant GNAS creates an actionable dependency in intraductal papillary mucinous neoplasms of the pancreas. Gut. 2025; 74(1), 75–88.

GA129- Multimodal Interrogation of Alzheimer's Disease by Hyperpolarized Metabolic Imaging in the Brain and Optical Imaging in the Retina

Julia R. Zickus 1, José Enriquez1, Bill Sun1, Muxin Wang1, Xudong Qiu1, Morgan McReynolds1, David Piwnica-Worms1, Seth T. Gammon1, Jim Ray1, Pratip Bhattacharya1

1The University of Texas MD Anderson Cancer Center, Houston, TX

Background: The progression of Alzheimer’s Disease (AD) can be broken down into three general stages: preclinical, mild cognitive impairment, and dementia1. Recent research into the metabolic changes in AD has revealed glycolytic hypo metabolism as a pre-symptomatic biomarker in the earlier stages of dementia pathology. AD is characterized by decreases in cerebral metabolic uptake of glucose correlated with diminished cognitive function, as well as a reduction of the amount of total cerebral lactate2–6. Furthermore, the retina has begun to emerge as a target for noninvasive diagnosis and tracking of disease progression of AD. Recent studies of the retina of AD patients have shown amyloid beta plaques and tau isoforms residing in the retina while also decreasing blood flow and causing inflammation7. Tau accumulation has been seen to promote anterograde axonal transport impairment and precedes retinal ganglion cell death in the retina of patients with AD. Recently published data also suggests that retinal ganglion cell–inner plexiform layer thickness metabolic profiles may inform mortality and common disease risks8, providing a distinctive insight into the retina as a window to systemic health. Together, these studies have led to the understanding that metabolic biomarkers (e.g., altered glucose metabolism) and axonal transport impairments may be utilized for early diagnosis and assessing AD progression.

Methods: Early diagnosis and monitoring of disease progression is dependent on reliable non-invasive imaging tools to assess glucose metabolism and axonal transport. Hyperpolarized Magnetic Resonance (HP-MR) is a non-invasive imaging technique that can quantify real-time metabolism in vivo. HP-MR of 1-13C Pyruvate was employed in the 5xFAD amyloid-beta and rTg4510 tau AD mouse models for in vivo imaging at multiple different time points that encompass all the stages of AD progression. These experiments were performed to determine the stages in disease progression characterized by detectable metabolic changes. The results were validated by ex-vivo NMR metabolomics and immunohistochemical analysis of AD pathology in brain tissues at the imaging time points. To assess axonal transport, non-invasive optical imaging was performed on the AD mouse models at different ages that encompass all stages of disease progression. This was conducted prior to a peptide probe injection of dTat488, 4 hours, and 24 hours after injection.

Results: The lactate-to-pyruvate ratio is decreased in the AD model mice, indicating decreased glycolytic activity. This decrease is also observed as the mice age. This ratio decreases from 10 to 16 months in the males, and 8 to 10 months in the females, in both the control and 5xFAD mice. This provides an interesting aging component to this study. Preliminary Nuclear Magnetic Resonance (NMR) metabolomics data of the brain indicates significant differences in the concentrations of total choline, creatine, malate, glutamate, and N-acetyl aspartate (NAA) all being decreased in 16-month-old male 5xFAD mice, with trending decreases in taurine and glutamine. Similarly, in 8-month-old Tau males, there were significant decreases in the concentrations of taurine, malate, glutamate, and NAA in the brain. Preliminary optical imaging data shows decreased autofluorescence in the retina of AD mice from 3 to 8 months old, whereas this is not observed in the control mice.

Conclusion: 1-13C pyruvate HP-MR can detect metabolic shift to lactate in this Alzheimer’s Disease mouse model at multiple different ages, and therefore at different stages in disease progression. Eyes can be the window to the general health of the body, given that the retina is the only part of our central nerve system that can be directly observed from outside via convenient, cost saving optical imaging. Given that AD is emerging as a disease of metabolic and inflammatory dysregulation, this research may provide a novel method to interrogate this disease.

Disclosures: Author Seth Gammon would like to disclose that he receives financial or material support from Radiopharm Ventures. All other authors have no conflicts of interest to disclose.

1. Rasmussen, J.; Langerman, H., Alzheimer's Disease - Why We Need Early Diagnosis. Degener Neurol Neuromuscul Dis 2019, 9, 123–130. 2. https://www.abstractsonline.com/pp8/#!/7883/presentation/63350.

3. Wu, L.; Zhang, X.; Zhao, L., Human ApoE Isoforms Differentially Modulate Brain Glucose and Ketone Body Metabolism: Implications for Alzheimer's Disease Risk Reduction and Early Intervention. The Journal of Neuroscience 2018, 38 (30), 6665.

4. https://www.abstractsonline.com/pp8/#!/7883/presentation/63347.

5. An, Y.; Varma, V. R.; Varma, S.; Casanova, R.; Dammer, E.; Pletnikova, O.; Chia, C. W.; Egan, J. M.; Ferrucci, L.; Troncoso, J.; Levey, A. I.; Lah, J.; Seyfried, N. T.; Legido-Quigley, C.; O'Brien, R.; Thambisetty, M., Evidence for brain glucose dysregulation in Alzheimer's disease. Alzheimer’s Dement 2018, 14 (3), 318–329.

6. Zhang, M.; Cheng, X.; Dang, R.; Zhang, W.; Zhang, J.; Yao, Z., Lactate Deficit in an Alzheimer Disease Mouse Model: The Relationship With Neuronal Damage. Journal of Neuropathology & Experimental Neurology 2018, 77, 1163 1176.

7. Koronyo Y, Biggs D, Barron E, Boyer DS, Pearlman JA, Au WJ, Kile SJ, Blanco A, Fuchs DT, Ashfaq A, Frautschy S, Cole GM, Miller CA, Hinton DR, Verdooner SR, Black KL, Koronyo-Hamaoui M. Retinal amyloid pathology and proof-of-concept imaging trial in Alzheimer's disease. JCI Insight. 2017, 12(16), e93621.

8. Chiasseu M, Alarcon-Martinez L, Belforte N, Quintero H, Dotigny F, Destroismaisons L, Vande Velde C, Panayi F, Louis C, Di Polo A. Tau accumulation in the retina promotes early neuronal dysfunction and precedes brain pathology in a mouse model of Alzheimer's disease. Mol Neurodegener. 2017, 12(1), 58.

GA130- Photo-controllable Bioorthogonal Reactions for in Situ Labeling of Bio-targets

1Nanjing University, Nanjing, China

Category: New Chemistry, Materials & Probes

Background: Biocompatible reactions controlled by photoirradiation are highly in demand in optochemical biology. Commonly used bioorthogonal cycloaddition reactions, including Cu(I)- catalyzed or strain-promoted azide−alkyne cycloaddition, Staudinger ligation, or the cycloaddition of alkenes with tetrazines, have greatly facilitated the labeling of various biomacromolecules, but not in a temporally and spatially resolved manner. Light irradiation is an ideal way to realize temporal and spatial control. Photoclick chemistry using UV light to in situ generate reactive nitrile imine, quinonemethide or strained alkyne has provided the possibility to control the following cycloaddition reaction with temporal or spatial resolution. However, nucleophilic thiol or water additions to the highly reactive nitrile imine or quinomethide intermediates can be quite competitive with the cycloaddition reaction in complex biological environments. It is desirable, then, to develop a photoinduced bioorthogonal reaction via new reactive species with reasonable reactivity to cycloaddition and resistance to nucleophilic thiol or water additions.

Methods: 9,10- phenanthrenequinone (PQ) that has an absorption shoulder peak in the visible region was used to develop photo-controllable bioorthogonal cycloaddition. Under biocompatible conditions, the excited PQ* reacted rapidly and selectively with the electron-rich vinyl ether (VE) functionality and generated fluorogenic [4+2] cycloadducts with the phenanthrodioxine (PDO) framework. This reaction was optimized through series of susbtrate development and further employed for various biological applications.

Results: The visible-light driven bioorthogonal DVPC reaction of the PQ with vinyl ether derivatives was established.1 Based on DVPC reaction, spatial-temporal labeling of biotargets on live cells was achieved. Furthermore, the first anionic cycloaddend-promoted bioorthogonal cycloaddition reaction, the DFC reaction, with the water-mediated formation of the highly electron-rich anionic cycloaddend from furan-2(3H)-one derivatives to proceed fast [4+2] cycloaddition reaction with ground state PQ was established.2 Moreover, the combination of NIR probe with bioorthogonal functionality demonstrated great potential to expand the application scope in multifunctional molecular imaging in vivo.3 NIR triggered activation of PROTAC in living animals using smart molecular design was also realized.4 The combination of upconversion nanoparticle with photo-responsive moieties provides a way to use longer wavelength light to modulate smart functional molecules in situ.

Conclusion: A light-triggered, catalyst- free bioorthogonal reaction was developed. The reaction was initiated by the excitation of PQ functionality that has a strong shoulder absorption peak in the visible region. The excited PQ* reacted rapidly and selectively with an electron-rich alkene, VE. Utilizing this new photo-controlled bioorthogonal reaction together with other biocompatible photo-transducers or bond-cleavage reactions, we achieved concurrent and orthogonal labeling or regulation of different biomolecular targets.

Disclosures: The authors have no conflicts of interest to disclose.

1. Li, J.; Kong, H.; Huang, L.; Cheng, B.; Qin, K.; Zheng M.; Yan, Z.; Zhang, Y. J. Am. Chem. Soc. 2018, 140, 14542–14546.

2. Xi, Z.; Kong, H.; Chen, Y.; Deng, J.; Xu,W.; Liang, Y.; Zhang, Y. Angew. Chem. Int. Ed. 2022, e202200239.

3. Wang, Y.; Weng, J.; Lin, J.; Ye, D.; Zhang, Y. J. Am. Chem. Soc. 2020, 142, 2787-2794.

4. Wang, W.; Zhu, C.; Zhang, B.; Feng, Y.; Zhang, Y.; Li, J. J. Am. Chem. Soc. 2023, 145, 16642–16649.

GA136- Evaluation of Trop2 Expression using Radiolabeled ADC Fragment in Gastric Cancer

Jessica C. Hsu 1, Wenpeng Huang2, Jonathan W. Engle1, Lei Kang2, Weibo Cai1

1University of Wisconsin-Madison, Madison, WI, 2Peking University First Hospital, Beijing, China

Background: Overexpression of Trop2 drives tumor cell proliferation, growth, and metastasis. The Trop2-targeting antibody–drug conjugate, sacituzumab govitecan-hziy (Trodelvy), has shown remarkable efficacy in patients with metastatic triple-negative breast cancer. ImmunoPET imaging offers a noninvasive method to visualize the in vivo expression and distribution of target antigens. However, imaging agents derived from intact antibodies are often hindered by prolonged circulation half-life and limited tumor penetration, resulting in delayed peak tumor uptake several days post-injection. In this study, we developed Trodelvy-F(ab')2 fragments for immunoPET imaging to assess Trop2 expression in gastric cancer models, aiming to expedite the imaging process.

Methods: Trodelvy-F(ab')2 were prepared using the IdeS protease kit and purified with Magne® Protein A beads and MagneHisTM Ni Particles. The resulting products were characterized through non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (non-reducing SDS-PAGE) and high-performance liquid chromatography (HPLC). Trodelvy-F(ab')2 was subsequently conjugat