Abstract 2477: Selective IL-21 and IFN-alpha immunocytokines engineered using the AlphaSeq platform

Abstract Although cytokine therapies have demonstrated curative effects in some cancer patients, clinical use remains limited due to undesired toxicity profiles accompanying systemic administration. Next generation cytokine approaches include conditional signaling focused on sites of interest, such as the tumor microenvironment or specific immune cell populations. Here, we share a novel approach for generating detuned cytokine therapeutic candidates using the AlphaSeq platform, which involves the re-engineering of yeast agglutination and mating to quantitatively measure protein-protein interactions at a library-on-library scale. Engineering interferon-alpha (IFNα) and interleukin-21 (IL-21), we show how AlphaSeq measures cytokine-receptor interactions and identifies cytokine variants with a broad range of affinities. A saturated mutational library was created for IFNα and IL-21and subsequently screened against a second library consisting of human IFNAR2 or human IL-21R, species orthologs and off-target receptors. AlphaSeq enabled identification of hundreds of detuned IFNα and IL-21 variants against both human and mouse receptors in parallel assays. Cytokine variants with lower affinity than parental IFNα or IL-21 were recombinantly expressed as Fc fusion proteins to orthogonally measure affinity with biolayer interferometry and characterize potency with an in vitro human PBMC phosflow assay, which showed strong correlation with AlphaSeq affinity measurements. Finally, detuned cytokine candidates were fused to anti-CD8 and other localizing antibodies to demonstrate cell population-specific signaling. Candidate molecules showed 1000-fold or greater potency in the targeted cell population than non-targeted populations. Our results show the AlphaSeq platform can accurately quantitate thousands of cytokine variant affinities simultaneously against multiple relevant receptors, enabling the selection of candidate immunocytokine antibody fusion proteins with targeted cell biased signaling. AlphaSeq’s rapid, comprehensive affinity determination is being used to develop clinically relevant IFNα and IL-21 therapeutic immunocytokines with accompanying preclinical data. Citation Format: Charles Lin, Colleen Shikany, Leah Homad, Jessica Fint, Ruchi Bansal, Davis Goodnight, Jeff Adamo, Danielle Van Citters, Ryan Swanson, Randolph Lopez. Selective IL-21 and IFN-alpha immunocytokines engineered using the AlphaSeq platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2477.