Synergism Between IL21 and Anti-PD-1 Combination Therapy is Underpinned by the Coordinated Reprogramming of the Immune Cellular Network in the Tumor Microenvironment.

T cell-stimulating cytokines and immune checkpoint inhibitors (ICI) are an ideal combination for increasing response rates of cancer immunotherapy. However, the results of clinical trials have not been satisfying. It is important to understand the mechanism of synergy between these two therapeutic modalities. Here, through integrated analysis of multiple single-cell RNA sequencing (scRNA-seq) datasets of human tumor-infiltrating immune cells, we demonstrate that IL21 is produced by tumor-associated T follicular helper cells and hyperactivated/exhausted CXCL13+CD4+ T cells in the human tumor microenvironment (TME). In the mouse model, the hyperactivated/exhausted CD4+ T cell-derived IL21 enhances the helper function of CD4+ T cells that boost CD8+ T cell-mediated immune responses during PD-1 blockade immunotherapy. In addition, we demonstrated that IL21's antitumor activity did not require T-cell trafficking. Using scRNA-seq analysis of the whole tumor-infiltrating immune cells, we demonstrated that IL21 treatment in combination with anti-PD-1 blockade synergistically drives tumor antigen-specific CD8+ T cells to undergo clonal expansion and differentiate toward the hyperactive/exhausted functional state in the TME. In addition, IL21 treatment and anti-PD-1 blockade synergistically promote dendritic cell (DC) activation and maturation to mature DC as well as monocyte to type 1 macrophage (M1) differentiation in the TME. Furthermore, the combined treatment reprograms the immune cellular network by reshaping cell-cell communication in the TME. Our study establishes unique mechanisms of synergy between IL21 and PD-1-based ICI in the TME through the coordinated promotion of type 1 immune responses. Significance: This study reveals how cytokine and checkpoint inhibitor therapy can be combined to increase the efficacy of cancer immunotherapy.

Efficacy and safety of CD24Fc in hospitalised patients with COVID-19: a randomised, double-blind, placebo-controlled, phase 3 study.

BACKGROUND: Non-antiviral therapeutic options are required for the treatment of hospitalised patients with COVID-19. CD24Fc is an immunomodulator with potential to reduce the exaggerated inflammatory response to tissue injuries. We aimed to evaluate the safety and efficacy of CD24Fc in hospitalised adults with COVID-19 receiving oxygen support. METHODS: We conducted a randomised, double-blind, placebo-controlled, phase 3 study at nine medical centres in the USA. Hospitalised patients (age ≥18 years) with confirmed SARS-CoV-2 infection who were receiving oxygen support and standard of care were randomly assigned (1:1) by site-stratified block randomisation to receive a single intravenous infusion of CD24Fc 480 mg or placebo. The study funder, investigators, and patients were masked to treatment group assignment. The primary endpoint was time to clinical improvement over 28 days, defined as time that elapsed between a baseline National Institute of Allergy and Infectious Diseases ordinal scale score of 2-4 and reaching a score of 5 or higher or hospital discharge. The prespecified primary interim analysis was done when 146 participants reached the time to clinical improvement endpoint. Efficacy was assessed in the intention-to-treat population. Safety was assessed in the as-treated population. This study is registered with ClinicalTrials.gov, NCT04317040. FINDINGS: Between April 24 and Sept 22, 2020, 243 hospitalised patients were assessed for eligibility and 234 were enrolled and randomly assigned to receive CD24Fc (n=116) or placebo (n=118). The prespecified interim analysis was done when 146 participants reached the time to clinical improvement endpoint among 197 randomised participants. In the interim analysis, the 28-day clinical improvement rate was 82% (81 of 99) for CD24Fc versus 66% (65 of 98) for placebo; median time to clinical improvement was 6·0 days (95% CI 5·0-8·0) in the CD24Fc group versus 10·0 days (7·0-15·0) in the placebo group (hazard ratio [HR] 1·61, 95% CI 1·16-2·23; log-rank p=0·0028, which crossed the prespecified efficacy boundary [α=0·0147]). 37 participants were randomly assigned after the interim analysis data cutoff date; among the 234 randomised participants, median time to clinical improvement was 6·0 days (95% CI 5·0-9·0) in the CD24Fc group versus 10·5 days (7·0-15·0) in the placebo group (HR 1·40, 95% CI 1·02-1·92; log-rank p=0·037). The proportion of participants with disease progression within 28 days was 19% (22 of 116) in the CD24Fc group versus 31% (36 of 118) in the placebo group (HR 0·56, 95% CI 0·33-0·95; unadjusted p=0·031). The incidences of adverse events and serious adverse events were similar in both groups. No treatment-related adverse events were observed. INTERPRETATION: CD24Fc is generally well tolerated and accelerates clinical improvement of hospitalised patients with COVID-19 who are receiving oxygen support. These data suggest that targeting inflammation in response to tissue injuries might provide a therapeutic option for patients hospitalised with COVID-19. FUNDING: Merck & Co, National Cancer Institute, OncoImmune.