Humanigen, Inc. announced it plans to support a Phase 2/3 study to evaluate lenzilumab for the early treatment of acute graft versus host disease (aGvHD) following allogeneic hematopoietic stem cell transplantation (HSCT) in collaboration with IMPACT, a world class accelerated trial network delivering innovative research for stem cell transplant patients in the UK. IMPACT delivers innovative research in partnership with the British Society of Blood and Marrow Transplantation and the University of Birmingham?s Cancer Research UK Clinical Trials Unit. The safety run-in component of the RATinG study is anticipated to be completed in 2022. The study is partially funded by IMPACT with Humanigen providing lenzilumab and the remaining funding for the study. Lenzilumab neutralizes the immune signalling protein granulocyte-macrophage colony-stimulating factor (GM-CSF), which has been shown to initiate the inflammatory cascade that drives aGvHD, a serious condition with significant unmet needs that affects 30%-50% of all patients who undergo HSCT. The RATinG study will evaluate lenzilumab in patients who have undergone allogeneic hematopoietic stem cell transplantation and been diagnosed with high-risk aGvHD. The trial will be conducted at up to 22 sites across the UK transplant network in two stages. The first stage of the study will treat 20 patients with lenzilumab before halting for an interim assessment of safety, efficacy, and futility. If an independent data monitoring committee deem the second stage to be feasible, then the trial will progress to its double-blind, randomized (1:1), second stage, which will enroll a minimum of 220 patients. A second interim analysis is planned to assess futility based upon the 28-day response rate to the first infusion in the first 150 evaluable patients. Within seven days following clinical diagnosis of aGvHD, investigators will assess patients? risk for steroid refractory aGvHD as measured by the Mount Sinai Acute GvHD International Consortium (MAGIC) biomarkers. Intermediate and high-risk groups will be treated with lenzilumab plus steroids in stage 1 and randomized to receive lenzilumab plus steroids or placebo plus steroids in stage 2. The stage 2 primary endpoint, non-relapse mortality, will be assessed once all patients have completed at least 6 months follow up. Lenzilumab is a proprietary Humaneered? first-in-class monoclonal antibody that has been proven to neutralize GM-CSF, a cytokine of critical importance in the hyperinflammatory cascade, sometimes referred to as cytokine release syndrome, or cytokine storm, associated with COVID-19 and other indications. Lenzilumab binds to and neutralizes GM-CSF, consequently improving outcomes for patients hospitalized with COVID-19. Humanigen believes that its GM-CSF neutralization has the potential to reduce the hyper-inflammatory cascade known as cytokine release syndrome common to chimeric antigen receptor T-cell (CAR-T) therapy and aGvHD.