Abstract CT169: A phase Ia study to evaluate RO7198457, an individualized Neoantigen Specific immunoTherapy (iNeST), in patients with locally advanced or metastatic solid tumors

Background: Neoantigens arising from somatic mutations are attractive targets for cancer immunotherapy as they may be recognized as foreign by the immune system. RO7198457 is a systemically administered RNA-Lipoplex iNeST designed to stimulate T cell responses against neoantigens. A first-in-human Phase Ia study of RO7198457 was conducted in patients with locally advanced or metastatic solid tumors. Methods: RO7198457 is manufactured on a per-patient basis and contains up to 20 patient- specific neoantigens. Nine doses of RO7198457 were administered i.v. at weekly and bi-weekly intervals during the 12-week induction stage and every 24 weeks during the maintenance stage. Results: In total, 29 patients enrolled in cohorts with doses ranging from 25-100 μg. The most common tumor types were HR+/HER2+ breast, prostate, and ovarian cancer. The median number of prior therapies was 5 (range 1-17). 34% of patients received prior immunotherapy. Most patients had low PD-L1 expression (97% patients with Conclusion: RO7198457 can be manufactured for individual patients with clinically relevant turn-around times. RO7198457 has a manageable safety profile consistent with its mechanism of action, and induced strong neoantigen-specific immune responses in patients with low and intermediate mutational load tumors types. A Ph1b study in combination with atezolizumab and a randomized Ph2 study of RO7198457 in 1L melanoma patients with pembrolizumab have been initiated, and two randomized clinical trials are planned in resected lung and CRC. Citation Format: Fadi Braiteh, Patricia LoRusso, Ani Balmanoukian, Sam Klempner, D R. Camidge, Matthew Hellmann, Michael Gordon, Johanna Bendell, Lars Mueller, Rachel Sabado, Patrick Twomey, Leila Delamarre, Jack Huang, Mahesh Yadav, Jingbin Zhang, Patrick McDonald, Felicitas Müller, Evelyna Derhovanessian, Özlem Türeci, Ugur Sahin, Lillian Siu. A phase Ia study to evaluate RO7198457, an individualized Neoantigen Specific immunoTherapy (iNeST), in patients with locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT169.