On Apr. 27, 2020, Regeneron and Sanofi announced preliminary results from the Phase 2 portion of an ongoing Phase 2/3 trial evaluating Kevzara (sarilumab), an interleukin-6 (IL-6) receptor antibody, in hospitalized patients with “severe” or “critical” respiratory illness caused by COVID-19. Following a review by the Independent Data Monitoring Committee (IDMC) of all available Phase 2 and Phase 3 data, the trial will be immediately amended so that only “critical” patients continue to be enrolled to receive Kevzara 400 mg or placebo.

The randomized Phase 2 portion of the trial compared intravenously-administered Kevzara higher dose (400 mg), Kevzara lower dose (200 mg) and placebo. It assessed 457 hospitalized patients, who were categorized at baseline as having either “severe” illness (28% of patients), “critical” illness (49% of patients) or “multi-system organ dysfunction” (MSOD) (23% of patients). Patients were classified as “severe” if they required oxygen supplementation without mechanical or high-flow oxygenation; or “critical” if they required mechanical ventilation or high-flow oxygenation or required treatment in an intensive care unit.

Preliminary analysis of the Phase 2 portion of the trial demonstrated that Kevzara rapidly lowered C-reactive protein (CRP), a key marker of inflammation, meeting the primary endpoint (see table below). Baseline levels of IL-6 were elevated across all treatment arms, with higher levels observed in “critical” patients compared to “severe” patients. Additionally, no new safety signals were observed with the use of Kevzara in COVID-19 patients.

Analysis of clinical outcomes in the Phase 2 trial was exploratory and pre-specified to focus on the “severe” and “critical” groups. In the preliminary Phase 2 analysis, Kevzara had no notable benefit on clinical outcomes when combining the “severe” and “critical” groups, versus placebo. However, there were negative trends for most outcomes in the “severe” group, while there were positive trends for all outcomes in the “critical” group (see table below). Subsequent to the IDMC review, Regeneron and Sanofi reviewed the discontinued “severe” group data, which revealed that the negative trends in the Phase 2 trial (n=126) were not reproduced in Phase 3 trial (n=276), and that clinical outcomes were balanced across the Kevzara and placebo treatment arms. Outcomes for the “severe” group were better than expected based on prior reports, regardless of treatment assignment: for example, in the Phase 2 portion, approximately 80% were discharged, 10% of patients died and 10% remain hospitalized.

The Kevzara trial was designed after a small (n=21), single-arm study in China (Xu et al) among mostly severe, febrile hospitalized COVID-19 patients found elevated IL-6 levels and suggested that inhibiting this pathway with the IL-6 blocker tocilizumab rapidly reduced fever and improved oxygenation in severe patients, allowing for successful hospital discharge. These uncontrolled findings require confirmation in adequately-sized and well-controlled trials. Last month, Regeneron and Sanofi moved rapidly to evaluate Kevzara in a prospective, randomized, placebo-controlled adaptively-designed U.S. Phase 2/3 trial in collaboration with U.S. groups including the Biomedical Advanced Research and Development Authority (BARDA, part of the office of the Assistant Secretary for Preparedness and Response at the U.S. Department of Health and Human Services), the Food and Drug Administration (FDA) and hospitals across the country.

The ongoing portion of the Phase 3 trial, which is continuing to enroll, currently includes more than 600 patients in the “critical” group. Regeneron and Sanofi remain blinded to the ongoing portion of the Phase 3 trial and expect to report results by June.

In addition, the companies are also conducting a second trial in countries outside of the U.S. The Phase 3 trial of Kevzara in approximately 400 patients hospitalized with COVID-19 infection is currently enrolling in Italy, Spain, Germany, France, Canada, Russia, Israel and Japan. Initial results from this second trial are expected in the third quarter of 2020. The findings from the U.S. trial will be shared immediately with the IDMC and similar amendments to the trial outside the U.S. will be considered.