1128 Preclinical development of genetically modified TILs expressing HER2-targeting CAR for ovarian cancer

<h3>Background</h3> Adoptive cell therapy (ACT) using <i>ex vivo</i> expanded tumor-infiltrating lymphocytes (TILs) has repeatedly mediated durable responses in patients with metastatic melanoma,¹ even after failure of prior immunotherapies.^{2 3} However, its adaptation to other cancer types remains a key challenge. Ovarian cancer is marked by high mortality rates, primarily due to late-stage diagnosis and treatment resistance. While treatment with anti-PD1 has been approved for TMB-/MSI-high ovarian cancer, TIL-based ACT has yet to show clear clinical benefit as treatment modality in metastatic ovarian cancer.^{4 5} TILs have been successfully isolated from ovarian tumor biopsies, but limited anti-tumoral potential against autologous tumor cell lines has been demonstrated. Thus, this project aims to improve TIL function by introducing a novel combination of TILs engineered with a CAR, creating CAR-TILs with enhanced tumor-elimination and survival capacity. <h3>Methods</h3> TILs and tumor cell lines have been established from patient-derived ovarian tumor biopsies. TILs were genetically engineered to express a second-generation HER2-targeted CAR with a low-affinity scFv-based targeting domain (clone 4D5-5) linked to an intracellular CD28/CD3ζ signaling domain using lentiviral transduction. Tumor cell lines were screened for target expression, and the reactivity and cytotoxicity of the HER2-TILs and TILs towards autologous and allogenic tumor cell lines were assessed. <h3>Results</h3> To improve TIL function, we have successfully introduced a low-affinity HER2-targeting CAR in TILs with no negative impact on viability or phenotype. These HER2-TILs maintain CAR expression and phenotype even after rapid expansion thus making them readily adaptable to existing TIL-based ACT workflow. HER2-TILs show enhanced tumor reactivity and killing of autologous tumor cells. Notably, HER2-TILs were able to kill tumor cells not otherwise recognized by the endogenous TIL TCRs. <h3>Conclusions</h3> These initial findings support further development of HER2-TILs as a viable treatment modality for metastatic ovarian cancer. <h3>References</h3> Dafni U, <i>et al</i>. Efficacy of adoptive therapy with tumor-infiltrating lymphocytes and recombinant interleukin-2 in advanced cutaneous melanoma: a systematic review and meta-analysis. <i>Ann. Oncol</i>. 2019;<b>30</b>:1902–1913. Besser MJ, <i>et al</i>. Adoptive transfer of tumor-infiltrating lymphocytes in patients with metastatic melanoma: intent-to-treat analysis and efficacy after failure to prior immunotherapies.<i> Clinical cancer research</i> 2013;<b>17</b>:4792–800. Rohaan MW,<i> et al</i>. Tumor-infiltrating lymphocyte therapy or ipilimumab in advanced melanoma.<i> N. Engl. J. Med</i>. 2022;<b>387</b>:2113–2125. Kverneland AH,<i> et al</i>. Adoptive cell therapy in combination with checkpoint inhibitors in ovarian cancer. <i>Oncotarget</i> 2020;<b>11</b>:2092–2105. Pedersen M, <i>et al</i>. Adoptive cell therapy with tumor-infiltrating lymphocytes in patients with metastatic ovarian cancer: a pilot study. <i>Oncoimmunology</i> 2018;<b>7</b>.