1141. Phase 3 Trial (in progress) of the SYK Inhibitor Fostamatinib in Patients Hospitalized with COVID-19: Protocol and Study Implementation Updates

Abstract

Abstract Background Immune dysregulation associated with COVID-19 includes immune cell activation, inflammatory cytokine release, and neutrophil extracellular trap release (NETosis), which are mediated by spleen tyrosine kinase (SYK) (Fig 1). Fostamatinib, an oral spleen tyrosine kinase (SYK) inhibitor, was approved for immune thrombocytopenia (ITP) in 2018, and the Phase 3 trials showed a lower than expected rate of thrombosis.1 Clinical studies showed a reduction in IL-6 in patients with rheumatoid arthritis.2 The active metabolite of fostamatinib (R406) protected against LPS-induced acute lung injury and thrombosis in mice3,4 and reduced MUC1 in a mouse model of ALI.5 Fostamatinib demonstrated abrogation of the hyperimmune response caused by anti-spike IgG,6 including reduction in hyperactivation of platelets7 and NETosis in neutrophils8 in in vitro studies using plasma from patients with severe COVID-19. A phase 2 study (NCT04579393) evaluated fostamatinib vs. placebo (all received standard of care [SOC]) in 59 hospitalized patients with COVID-19 and demonstrated reduction in mortality, ordinal scale scores, and number of days in the intensive care unit (ICU) as well as meeting the primary endpoint of safety.9 A phase 3 clinical study (NCT04629703) of fostamatinib for the treatment of COVID-19 is underway. Figure 1.Mechanism of Disease (COVID-19) and Role of SYK inhibition Methods A Phase 3, randomized, double-blind, placebo-controlled, adaptive design, multi-center study (NCT04629703) is underway to evaluate fostamatinib in 308 adult patients hospitalized with COVID-19 and on oxygen without intubation (Fig 2). Patients will receive fostamatinib 150 mg BID or placebo for 14 days; both arms receive SOC. At baseline, the clinical status score (8-point ordinal scale) had to be 5 or 6. Patients ≥ 65 years had to have ≥ 1 risk factor for severe disease and adults < 65 had to have ≥ 3. The primary outcome is days on oxygen (Day 1 to 29). Other endpoints include change in clinical status score, days in the ICU, time to hospital discharge, all-cause mortality, oxygen-free status and safety. Fostamatinib is investigational for COVID-19. Results Blinded data from this trial in progress are as of 2 December 2021. See Fig 3. Conclusion Final results of this Phase 3 trial are anticipated in 2022. Disclosures Lucy Yan, MD, PhD, Rigel Pharmaceuticals: Employee|Rigel Pharmaceuticals: Stocks/Bonds Ziad Mallat, MD, PhD, Rigel Pharmaceuticals: Advisor/Consultant Suzana Margareth Lobo, MD, PhD, Rigel Pharmaceuticals: Grant/Research Support Anuj Malik, MD, MS, Rigel Pharmaceuticals: Grant/Research Support Wolfgang Dummer, MD, PhD, Rigel Pharmaceuticals: Employee|Rigel Pharmaceuticals: Stocks/Bonds.