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Astegolimab or Efmarodocokin Alfa in Patients With Severe COVID-19 Pneumonia: A Randomized, Phase 2 Trial*

OBJECTIVES: Severe cases of COVID-19 pneumonia can lead to acute respiratory distress syndrome (ARDS). Release of interleukin (IL)-33, an epithelial-derived alarmin, and IL-33/ST2 pathway activation are linked with ARDS development in other viral infections. IL-22, a cytokine that modulates innate immunity through multiple regenerative and protective mechanisms in lung epithelial cells, is reduced in patients with ARDS. This study aimed to evaluate safety and efficacy of astegolimab, a human immunoglobulin G2 monoclonal antibody that selectively inhibits the IL-33 receptor, ST2, or efmarodocokin alfa, a human IL-22 fusion protein that activates IL-22 signaling, for treatment of severe COVID-19 pneumonia. DESIGN: Phase 2, double-blind, placebo-controlled study (COVID-astegolimab-IL). SETTING: Hospitals. PATIENTS: Hospitalized adults with severe COVID-19 pneumonia. INTERVENTIONS: Patients were randomized to receive IV astegolimab, efmarodocokin alfa, or placebo, plus standard of care. The primary endpoint was time to recovery, defined as time to a score of 1 or 2 on a 7-category ordinal scale by day 28. MEASUREMENTS AND MAIN RESULTS: The study randomized 396 patients. Median time to recovery was 11 days (hazard ratio [HR], 1.01 d; p = 0.93) and 10 days (HR, 1.15 d; p = 0.38) for astegolimab and efmarodocokin alfa, respectively, versus 10 days for placebo. Key secondary endpoints (improved recovery, mortality, or prevention of worsening) showed no treatment benefits. No new safety signals were observed and adverse events were similar across treatment arms. Biomarkers demonstrated that both drugs were pharmacologically active. CONCLUSIONS: Treatment with astegolimab or efmarodocokin alfa did not improve time to recovery in patients with severe COVID-19 pneumonia.

The study consisted of a screening period followed by randomization (Fig. 1A); on day 1, patients received either one IV infusion of 700 mg astegolimab, 90 μg/kg efmarodocokin alfa, or matching placebos (2 and 5 mL vials of a sterile, clear solution to match astegolimab and efmarodocokin alfa, respectively, with diluent for efmarodocokin alfa supplied by Genentech for the matching placebo). If the patient remained hospitalized and on supplemental oxygen, a second dose of 350 mg astegolimab, 90 μg/kg efmarodocokin alfa, or matching placebo was given on day 15 Meaning: Despite lack of clinical benefit, both drugs were safe and pharmacologically active.
(Brazil). Patients, or their legally authorized representatives, provided written, informed consent before study procedures.

Patients
Eligible patients were aged 18 years or older, hospitalized with COVID-19 pneumonia, verified by positive polymerase chain reaction assay, chest radiograph or computed tomography scan, and having peripheral capillary oxygen saturation (Spo 2 ) less than or equal to 93% or Pao 2 /Fio 2 less than or equal to 300 mm Hg or a requirement for supplemental oxygen to maintain Spo 2 greater than 93%. Key exclusion criteria included likely progression to death within 24 hours; clinical evidence of active or unstable cardiovascular disease; and Janus kinase inhibitor use within 30 days or five drug elimination half-lives before screening (full eligibility

Randomization and Blinding
Patients were assigned via an interactive voice or webbased response system to treatment groups receiving astegolimab, efmarodocokin alfa, or their matching placebos at a 2:2:1:1 ratio using permuted-block randomization. Randomization was stratified by invasive mechanical ventilation use and region. The proportion of patients needing invasive mechanical ventilation was capped at ~25%. See Supplementary Appendix (http:// links.lww.com/CCM/H235) for details on blinding.

Outcomes and Assessments
The primary efficacy endpoint was time to recovery, defined as time to a score of 1 or 2 on a 7-category ordinal scale (whichever occurred first): 1, discharged (or "ready for discharge" as evidenced by normal body temperature and respiratory rate, and stable oxygen saturation on ambient air or less than or equal to 2 L supplemental oxygen); 2, non-ICU hospital ward (or "ready for hospital ward") not requiring supplemental oxygen; 3, non-ICU hospital ward (or "ready for hospital ward") requiring supplemental oxygen; 4, ICU or non-ICU hospital ward, requiring noninvasive ventilation or high-flow oxygen; 5, ICU, requiring intubation and mechanical ventilation; 6, ICU, requiring extracorporeal membrane oxygenation (ECMO) or mechanical ventilation and additional organ support (e.g., vasopressors, renal replacement therapy); 7, death (17). During the trial, the original primary endpoint, "Clinical status assessed using a 7-category ordinal scale at day 28" was changed because prior trials for COVID-19 pneumonia indicated that time to recovery was more clinically meaningful (18). The original primary endpoint is now a secondary endpoint ( Safety assessments included frequency and severity (using Common Terminology Criteria for Adverse Events) of adverse events (AEs) and serious adverse events (SAEs), changes in vital signs, electrocardiograms, and clinical laboratory results. Pharmacokinetic assessments included serum concentration measurements of astegolimab and efmarodocokin alfa.

Statistical Methods
Efficacy analyses were conducted on the modified intent-to-treat (mITT) population (all patients who received at least one dose of study drug), with patients grouped according to treatment assigned at randomization. Placebo-treated patients were pooled for outcome analyses. Time to recovery was analyzed using the stratified log-rank test, adjusting for stratification factors. Hazard ratios (HRs) comparing astegolimab or efmarodocokin alfa with placebo, respectively, adjusting for stratification factors, were estimated using a Cox proportional hazards regression model. For timeto-recovery and time-to-improvement endpoints, patients who did not recover/improve or died before day 28 were censored at day 29.
The planned sample size of 390 patients provided ~80% power using a log-rank test to detect a 7-day difference between treatment groups (astegolimab vs placebo; efmarodocokin alfa vs placebo) in time to recovery with a minimum detectable difference of 5.3 days assuming the median time to improvement in the placebo group was 21 days (with 28 d of follow-up), using a one-sided 5% alpha.

Patient Disposition and Baseline Characteristics
The COVASTIL study, conducted from June 2020 to March 2021, enrolled and randomized patients at 54 investigator sites (Supplementary Appendix, http:// links.lww.com/CCM/H235). Of 463 patients screened, 410 were randomized, and 396 received at least one dose of study drug or placebo (313 patients [79%] received one dose; 83 patients [21%] received two doses) and were included in the final analysis. Three-hundred thirty-two patients completed study assessments through day 28 (Fig. 1B), and 299 patients completed study assessments through day 60.

Pharmacokinetics
Because the majority of patients (astegolimab, 103 [79.2%]; efmarodocokin alfa, 107 [81.1%]) received only one dose, only pharmacokinetic parameters following the first doses of astegolimab and efmarodocokin alfa were calculated (Table S5, http://links.lww. com/CCM/H235). The cohort mean of the maximum serum concentration (C max ) for astegolimab was 210 µg/mL and for efmarodocokin alfa was 1,286 ng/ mL. The serum trough concentration (C trough_day 14 ) for astegolimab was 33.5 µg/mL and for efmarodocokin alfa was 81.8 ng/mL. Overall, pharmacokinetic exposures showed high variability (30-73%) in patients. To understand potential effects of SARS-CoV-2 infection on astegolimab and efmarodocokin alfa exposure, C max and area under the curve from 0 to 14 days (AUC 0-14 ) were plotted by baseline disease severity. Patients with higher baseline disease severity (ordinal score of 4 vs 3) a Matching placebo groups for astegolimab and efmarodocokin alfa were pooled for all analyses. b Clinical status was defined by the 7-category ordinal scale: 1, discharged (or "ready for discharge" as evidenced by normal body temperature and respiratory rate, and stable oxygen saturation on ambient air or ≤ 2 L supplemental oxygen); 2, non-ICU hospital ward (or "ready for hospital ward") not requiring supplemental oxygen; 3, non-ICU hospital ward (or "ready for hospital ward") requiring supplemental oxygen; 4, ICU or non-ICU hospital ward, requiring noninvasive ventilation or high-flow oxygen; 5, ICU, requiring intubation and mechanical ventilation; 6, ICU, requiring extracorporeal membrane oxygenation or mechanical ventilation and additional organ support (e.g., vasopressors, renal replacement therapy); 7, death. had lower astegolimab exposure, but baseline disease severity did not impact efmarodocokin alfa exposure (Fig. S2, http://links.lww.com/CCM/H235). The antidrug antibody rate after treatment with either drug was low (Supplementary Results, http://links.lww.com/ CCM/H235).

Biomarkers
Serum pharmacodynamic biomarkers for astegolimab and efmarodocokin alfa were measured throughout the study. Astegolimab binds sST2, a decoy receptor for ST2, allowing sST2 use as a surrogate for ST2 binding. Efmarodocokin alfa induces expression of both REG3A (a secreted antimicrobial protein produced by stomach, pancreas, and Paneth cells in the ileum) and CRP (an acute phase protein) (16,22,23). Sparse sample collection affected interpretability of day 15 and 21 data (samples were only collected at these timepoints from patients who remained hospitalized). Baseline serum sST2 in COVID-19 patients was increased (13.8-1,600 ng/mL; mean, 116 ng/mL; Table  S6, http://links.lww.com/CCM/H235) compared with healthy volunteers (HVs) (24). Similar to other serum proteins (25), astegolimab binding is predicted to increase the half-life of sST2, resulting in sST2 elevations. Absolute sST2 levels increased over time in astegolimab-treated patients but not in other treatment groups (Fig. 3A).

DISCUSSION
COVASTIL, a phase 2, double-blind, placebo-controlled trial, is the first study to examine IL-33 and IL-22  with those expected in a study of patients hospitalized with severe COVID-19 and with previous studies of these drugs (11,23). Although there were more related SAEs in the treatment groups compared with the placebo group, the small number of events precluded any definitive conclusions. We observed no new safety signals for either study drug. Previously identified pharmacodynamic biomarkers for astegolimab (sST2) and efmarodocokin alfa (REG3A, CRP) were measured in patients with COVID-19 pneumonia. Baseline serum levels of sST2 were elevated, possibly reflecting an association between sST2 and the presence of tissue damage, as seen in cardiac disease and ARDS (26,27). Serum sST2 increased above baseline levels in the astegolimab arm compared with the other treatment arms‚ indicating target engagement and pharmacological activity.
Increases in REG3A following efmarodocokin alfa treatment indicated IL-22R engagement in these patients. The percent increase from baseline was lower compared with HVs (23), but elevated baseline REG3A levels may explain this finding. While REG3A has been detected in human lung fibrotic tissue (28), this is the first study demonstrating elevated levels of REG3A in the circulation of COVID-19 patients. Although the murine homolog of REG3A, REG3γ, is induced by IL-22 in lung epithelium (29) and has been shown to provide protection in lung infection models (30)(31)(32)(33), in this study, REG3A increases were not correlated with clinical benefit.
As expected in patients with COVID-19 (20,21,34), baseline CRP levels were elevated. Similar to previous studies (23), efmarodocokin alfa treatment led to a significant increase in CRP that was not seen in the other groups. Due to the timing of sample collection, we did not measure the expected CRP peak after the day 15 dose. Although the early decrease of CRP as compared with the other treatment arms suggests efmarodocokin alfa treatment may promote resolution of inflammation, factors such as secondary bacterial infections and concomitant medications may have also contributed to elevated CRP levels.
There are four possible reasons for the apparent lack of efficacy of these drugs in patients with COVID-19 pneumonia, despite evidence of their pharmacological activity. First, while the IL-33 and IL-22 pathways may be involved in development of COVID-19 pneumonia, redundancies may have been sufficient to prevent measuring the effects of modulating these pathways. Second, patients were heterogeneous for disease presentation, comorbidities, and SOC treatment. During the study, COVID-19 treatment approaches were evolving and varied by region, and SOC in this study included steroids, remdesivir, and tocilizumab. In contrast to earlier studies (e.g., Adaptive COVID-19 Treatment Trial-1 [18]), most patients in this trial received dexamethasone, which may have masked the effect of astegolimab. Overall, COVID-19 treatment outcomes improved during the study, with the percentage of hospitalized patients admitted to ICUs and rates of mechanical ventilation decreasing significantly (35,36). Third, patients who were mechanically ventilated at time of randomization comprised 10% of the patient population, and inclusion of only a small number of these severely ill patients may have limited the opportunity to see a treatment effect.
Fourth, study drug exposure (dose and frequency) or timing may have been insufficient for efficacy in COVID-19 patients. However, a dose-ranging study would be needed to address this question, and this study tested astegolimab and efmarodocokin alfa at the highest safe doses based on previous studies (11,23). Based on efmarodocokin alfa's mechanism of action, C max or AUC could be drivers of efficacy. While the observed mean pharmacokinetic exposures were expected (similar to ulcerative colitis patients but lower than HVs), the exposure distribution was highly variable in patients (C max , 73%; AUC 0-14 , 43%), possibly contributing to insufficient efficacy. For astegolimab, exposure (C max and AUC) was slightly lower than exposure in HVs (unpublished data). In an exploratory analysis, patients with higher disease severity (ordinal score of 4 vs 3) tended to have lower exposure. Timing of presentation with COVID-19 is heterogeneous, and it is unclear which subset of patients might benefit from either therapy with respect to timing of drug administration, number of doses of drug, and severity of COVID-19 pneumonia. In previous COVID-19 trials examining drugs that target hyperinflammation (e.g., tocilizumab and baricitinib), clinical benefit was only shown in patients with severe COVID-19 pneumonia, especially those on supplemental oxygen, who were beginning to clinically worsen (37,38). A follow-up study measuring later clinical and imaging outcomes is ongoing to evaluate long-term effects of both interventions.

CONCLUSIONS
Although neither astegolimab nor efmarodocokin alfa showed efficacy against COVID-19 pneumonia, this study confirmed that both drugs were safe and pharmacologically active in patients with severe COVID-19 pneumonia. Findings from COVID-19 pneumonia yield important insights but may not be generalizable to ARDS. Further nonclinical and clinical studies are needed to identify the subset of COVID-19 patients who may benefit from blockade in the inflammatory cascade or from stimulation of pathways that can promote healing of damaged lung tissue.