Abstract 5551: SGN-2FF: A small-molecule inhibitor of fucosylation modulates immune cell activity in preclinical models and demonstrates pharmacodynamic activity in early phase 1 analysis

Abstract

Abstract SGN-2FF, an orally bioavailable small molecule inhibitor of glycoprotein fucosylation, demonstrates encouraging preclinical antitumor activity in mouse models with suggested multiple mechanisms of action, including direct and indirect effects on immune cells, tumor cells, and the tumor microenvironment. The effects of SGN-2FF were evaluated on tumors implanted in multiple strains of mice to determine how differences in the immune repertoire affect the antitumor activity. SGN-2FF treatment of nude mice, which maintain functional B cells and antibody production, resulted in a delay in LS174T tumor growth compared with untreated mice, while LS174T tumors in SCID mice, which lack B cells, were unaffected by SGN-2FF. These data suggest that activity of SGN-2FF in nude mice may be dependent on residual B cells and circulating antibodies. The antitumor effect of SGN-2FF in syngeneic mouse models with intact immune systems also appears to be dependent on T cell activity. Transfer of T cells isolated from SGN-2FF-treated tumor-bearing mice to naïve tumor-bearing mice was sufficient to delay tumor growth. T cells isolated from untreated tumor-bearing mice did not have the same effect. These results demonstrate that afucosylated immune cells play a key role in the preclinical activity of SGN-2FF. Various preclinical assays were used to detect SGN-2FF-mediated changes in cellular and IgG fucosylation important for biological activity. These assays are being applied in evaluating patient samples in the ongoing phase 1, multicenter, dose-escalation study investigating the safety, tolerability, PK, and biomarkers of antitumor activity of SGN-2FF administered orally to adult patients with advanced solid tumors (NCT# 02952989). Changes in peripheral IgG fucosylation, absolute neutrophil count, and immune cell surface fucosylation were identified as initial biomarkers for proof of pharmacodynamic activity. Preliminary data following daily doses of SGN-2FF demonstrate that cell surface fucosylation on granulocytes was significantly reduced and neutrophil count was significantly increased in 6 of 7 treated subjects; additionally, IgG fucosylation was significantly decreased in 7 of 7 subjects. PK have been characterized, and preliminary results are within the expected range as predicted from preclinical studies. Following daily administration of SGN-2FF, accumulation of the active metabolite, GDP-2FF, was observed intracellularly, while no accumulation of SGN-2FF was observed in plasma. Collectively, these data demonstrate robust biological effects of SGN-2FF. The pharmacodynamic biomarkers and PK analysis are informing next steps in identifying an optimal dose and dosing schedule for SGN-2FF. Citation Format: Nicole M. Okeley, Ryan A. Heiser, Weiping Zeng, Shawna Mae Hengel, Jason Wall, Peter C. Haughney, Timothy Anthony Yap, Francisco Robert, Rachel E. Sanborn, Howard Burris, Laura Q. Chow, Khanh T. Do, Martin Gutierrez, Karen Reckamp, Amy Weise, D Ross Camidge, John Strickler, Conor Steuer, Zejing Wang, Megan M. O'Meara, Stephen C. Alley, Shyra J. Gardai. SGN-2FF: A small-molecule inhibitor of fucosylation modulates immune cell activity in preclinical models and demonstrates pharmacodynamic activity in early phase 1 analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5551.