Abstract 2768: Non-invasive detection of pancreatic adenocarcinoma using Ga-68 labelled epha2 targeting peptide
Authors: Sharma Ajay Kumar , Gupta Kuldeep , Mishra Akhilesh , Chen Sophia , Lofland Gabriela , Armstrong Todd , Gabrielson Edward , Zheng Lei , Jaffee Elizabeth M. , Nimmagadda Sridhar 
Published: April 2023

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease and early diagnosis is paramount for effective treatment. Molecular imaging techniques such as positron emission tomography (PET) could provide an early diagnosis of PDAC to potentially improve survival. EphA2, a member of Erythropoietin-producing hepatocellular (Eph) receptors, is a desirable target for PDAC detection as it is pro-oncogenic and expressed in &gt; 90% of PDACs. Here, we report the development of a peptide-based PET imaging agent, [68Ga]AJ201, evaluation of its pharmacokinetics, and its potential to non-invasively detect variable EphA2 expression in moue models of PDAC.

Methods: A bicyclic peptide, AJ201, was synthesized and its binding affinity for EphA2 was determined by surface plasmon resonance (SPR). AJ201 was labelled with Gallium-68 in high radiochemical yields and purity. In vitro uptake of the resulting [68Ga]AJ201 was carried out in different PDAC cell lines with variable EphA2 expression (Panc1, CFPAC1, Hs766T, and SU8686) and Jurkat cell line as a negative control. In vivo pharmacokinetic properties of [68Ga]AJ201 were evaluated by PET-MR imaging and ex vivo biodistribution studies in different subcutaneous PDAC xenografts and in Panc1 orthotopic model (n=4-5/tumor). [68Ga]AJ201 in vivo specificity for EphA2 was confirmed by cross-correlative immunohistochemistry of xenografts and by co-injection of a blocking dose of non-radioactive AJ201 (1 mg/kg).

Results: AJ201 binds human EphA2 with high affinity (KD ~ 0.2 nM). Flow cytometry analysis confirmed variable EphA2 expression in all the PDAC cell lines tested with Panc1 and CFPAC cell lines exhibiting highest and lowest expression, respectively. In vitro binding assays showed variable [68Ga]AJ201 uptake in all the PDAC cells and almost no uptake in the presence of 1 µM non-radioactive AJ201 and in negative control Jurkat cells. In vivo dynamic PET-MR imaging revealed high and specific uptake of [68Ga]AJ201 in Panc1 tumor xenografts within 5 min and retained for at least 90 min. In contrast, [68Ga]AJ201 exhibited fast clearance from normal tissues resulting in high contrast images at 60 minutes and a high tumor-to-muscle ratio of 25.8 ± 6.7. [68Ga]AJ201 uptake in tumors was reduced by &gt; 80 % in mice receiving blocking dose, confirming the specificity of the radiotracer. Also, [68Ga]AJ201 PET provided high contrast images of orthotopic Panc1 tumors. Furthermore, [68Ga]AJ201 PET showed variable and expression dependent uptake in all the PDAC xenografts tested that was corroborated by EphA2 expression detected by IHC.

Conclusion: [68Ga]AJ201 is an EphA2 specific high affinity peptide-based PET imaging agent that detects orthotopic PDAC in mouse models at 60 minutes and demonstrates potential to non-invasively detect PDAC in patients.

Citation Format: Ajay Kumar Sharma, Kuldeep Gupta, Akhilesh Mishra, Sophia Chen, Gabriela Lofland, Todd Armstrong, Edward Gabrielson, Lei Zheng, Elizabeth M. Jaffee, Sridhar Nimmagadda. Non-invasive detection of pancreatic adenocarcinoma using Ga-68 labelled epha2 targeting peptide [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2768.