INTRODUCTION
Systemic inflammation seems to play a key role in the progression of COVID-19 to acute respiratory distress syndrome (ARDS) (
1,
2). A disordered inflammatory host immune response ultimately leading to diffuse alveolar damage, endothelial injury, and microvascular thrombosis is thought to be a crucial step in the pathogenesis of severe COVID-19 (
3,
4). Reinforcing this, adjuvant treatment with dexamethasone has been associated with better outcomes in patients with COVID-19 requiring respiratory support (
5).
Interleukin (IL)-6 blockade has been proposed as an attractive immunomodulatory approach to treat systemic inflammatory response in COVID-19. Although initial retrospective studies using tocilizumab (
6–8), a membrane-bound monoclonal anti-IL-6 antibody, reported a survival benefit of this strategy, results from clinical trials have been conflicting (
9–14). A large meta-analysis including clinical trials assessing the efficacy of IL-6 antagonists in patients hospitalized for COVID-19 released in July 2021 has concluded that the use of IL-6 antagonists is associated with lower mortality (
15).
Sarilumab, a human anti-IL-6 soluble receptor monoclonal antibody licensed for the treatment of rheumatoid arthritis, is an alternative option for IL-6 blockade. In April 2020 the SARICOR trial was conceived with the aim to investigate the efficacy and safety of early treatment with sarilumab added to standard of care (SOC) in hospitalized adults with COVID-19 pneumonia and features of systemic inflammation to prevent progression to severe pulmonary forms of COVID-19 requiring high-flow nasal oxygenation (HFNO) devices, non-invasive mechanical ventilation (NIMV), and/or invasive mechanical ventilation (IMV).
DISCUSSION
In this phase II trial, we found that in patients recently admitted to hospital with COVID-19 pneumonia and features of systemic inflammation, early IL-6 blockade with a single dose of sarilumab 400 mg was safe and associated with a trend for better outcomes than the current SOC. These benefit signals were observed for primary and secondary outcomes and across different sensitivity and secondary analyses, providing a rationale for continuing with larger, confirmatory phase III trials.
This was a phase II trial that aimed to explore if early blockade with two different doses of the sarilumab human anti-IL-6 soluble receptor monoclonal antibody prevents disease progression in COVID-19. As the study was conducted during the earlier phases of the pandemic, sample size calculations were made on the basis of ICU admissions and mortality rates at that time. Fortunately, mortality has evolved and fallen since the beginning of the epidemic, which has notably affected the power of this trial to detect differences between groups. In spite of this, our results suggest that adding sarilumab 400 mg to SOC provides clinical benefit. Thus, when compared with the control group, a 15% lower rate of need for HFNO, NIMV, or IMV with sarilumab 400 mg was observed. Notably, there were no deaths among those receiving sarilumab 400 mg. On the other hand, recovery tended to occur more frequently and faster with sarilumab 400 mg, which could help to lessen the burden of COVID-19 in an overloaded health care system. Finally, post hoc analyses using DOOR methodology were consistent with a clinically beneficial effect of this treatment. While this trial cannot definitely conclude that sarilumab 400 mg reduces clinical progression or mortality due to its lack of potency, these results support the continuation of the clinical evaluation of this strategy in further trials.
In addition to a relative low sample size, this trial has other limitations. First, it was nonblinded, which has the potential for ascertainment bias. Besides, awareness of the intervention assignment could affect management in the control group. In fact, three patients in the control group received tocilizumab due to clinical deterioration but prior to achieving the primary outcome, probably due to the perceived clinical benefit of tocilizumab by many clinicians at that time during the trial. However, sensitivity analyses excluding these patients showed similar results and other secondary outcomes such as mortality are very unlikely to be influenced by the open design. Second, recruitment extended over an 8-month period, which could potentially affect background care during the trial. Apart from the difficulties of conducting an academic clinical trial during a pandemic, the wide use of IL-6 and IL-1 blockers by clinicians, even before of any evidence of its efficacy, has been a constant in many parts of the world and hindered recruitment in a trial including a control group, thus explaining the relatively long recruitment period. However, results from the unique interventions that have showed some clinical benefit, such as remdesivir or corticosteroids, were available before enrollment of the first patient. Indeed, almost all patients in the trial received concomitant corticosteroids at baseline and overall mortality was 6%, reflecting that our trial population is highly representative of the current clinical picture of hospitalized COVID-19 patients in high-income countries.
Previous information on the use of sarilumab for the treatment of COVID-19 was scarce and inconclusive. Apart from 48 patients included in the REMAP-CAP trial (
9) and two small observational studies (
16,
17), information from larger randomized clinical trials was limited to that announced by press releases (
18,
19). A randomized double-blind, placebo-controlled clinical trial including patients with COVID-19 pneumonia requiring oxygen or critical care not showing efficacy of intravenous sarilumab 200 mg or 400 mg compared with placebo has recently been published (
20). Drawbacks of this previous trial were that only 20% of patients received corticosteroids and more than 75% had normal IL-6. Thus, suboptimal backbone therapy and inadequate selection criteria for evaluating immunomodulatory therapy might explain the negative findings. By contrast, more than 90% of patients in our study were on oxygen support and receiving corticosteroids at baseline and patients were enrolled on the basis of exhibiting features of systemic inflammation. In such a population, our results are in line with recent findings of the RECOVERY trial (
21) with the use of tocilizumab and the WHO REACT meta-analysis (
15), suggesting a role of IL-6 blockade if combined with steroids and in patients on oxygen support with high inflammatory markers.
Our study has several strengths. First, it was performed in a context of universal use of corticosteroids and rates of 11% for IMV use and 6% overall mortality, which is a more representative scenario of current COVID-19 care. Thus, interventions in this trial were proven in a more exigent context than other larger clinical trials assessing treatment interventions where mortality rates in the control group exceeded 30% (
21). Besides, unlike other large platform COVID-19 trials, our trial included a contemporaneous control group, which is the best way to guarantee that between-group differences in outcomes can be attributed to interventions and to avoid unnoticed bias, as has been recently noted (
22). Finally, we have included a
post hoc DOOR analysis, a methodology designed to address several challenges in clinical trials that allows evaluating the clinically relevant question of superiority of a new strategy based on the consideration of all consequences (
23). With this approach, our analyses suggest that receiving sarilumab 400 mg promotes a clinical benefit when compared to the control group.
Like other trials using tocilizumab, treatment with sarilumab was safe and was not associated with serious adverse events. Notably, we did not observe an increased risk of serious infections when compared with patients in the control group, in spite of having used higher doses than commonly used for rheumatoid arthritis in one of the arms of the study. As with other interventions, long-term safety, including assessing the risk of secondary infections beyond 28 days should be confirmed.
The role of IL-6 blockade in the treatment of COVID-19 is being clarified by recent studies. REMAP-CAP (
9) and RECOVERY (
21) trials have recently provided evidence of a survival benefit of tocilizumab in critically ill patients and in patients with hypoxia and evidence of inflammation receiving systemic corticosteroids, respectively. A reduction in all-cause mortality has been also found in a large meta-analysis (
15). Our results suggest that combining sarilumab at high doses with corticosteroids early on in the course of COVID-19 pneumonia reduces clinical progression and shortens the time to hospital discharge. Whether similar clinical benefits can be expected with tocilizumab or sarilumab is not known, as comparative clinical trials are lacking. In the meantime, it is reasonable to prioritize the use of tocilizumab as the cumulative safety and efficacy with such a drug is larger than for sarilumab and to consider the use of sarilumab as an alternative option based on our results. The increasing demands of tocilizumab have led to shortage of the drug during the pandemic, which can occur again due to its widespread use. Our study provides evidence for the use of sarilumab as an alternative option if access to tocilizumab is limited. As our study has not included patients with critical COVID, the use of tocilizumab should be prioritized in this specific scenario.
In summary, patients hospitalized with COVID-19 pneumonia requiring oxygen support and markers of systemic inflammation receiving corticosteroids might benefit from early blockade of IL-6 with sarilumab 400 mg during the first 48 h of admission. The efficacy of this strategy should be confirmed in a well-powered randomized clinical trial.
ACKNOWLEDGMENTS
We thank the following for their collaboration in the study: Rocío Herrero del Río, Jesús Machuca, Estefanía García Sánchez, Antonio Lesmes Serrano, Concepción Ferrete Morales, Jesús M. Gómez Mateos (Hospital Universitario de Valme), Patricia Jiménez-Aguilar, María Luisa Fernández-Ávila, Blanca Anaya-Baz, Rosario Castilla-Ortiz (Hospital Universitario Puerto Real), María Macías-Barrera, Rocío Gálvez- Cordero (Hospital Universitario Virgen Macarena), María Esther Guisado-Espartero Justo Sánchez-Gil, María Lorena Montero-Rivas, Raimundo Tirado-Miranda, José Pablo Mazuelas-Teatino, Juan Hidalgo-Cabrera (Hospital Infanta Margarita), Jorge Rodríguez-Gómez, María Purificación Carmona-Sánchez, José Manuel Vaquero-Barrios, Roberto Martin de León, Laura Limia-Pérez, Antonio Miguel Luque-Pineda (Hospital Universitario Reina Sofía), Alberto Benavente-Fernández, María del Mar Díaz-Alcázar, Emilio Guirao-Arrabal, Naya Faro-Mínguez (Hospital Universitario Clínico San Cecilio), María Concepción López-Robles, Judit Constan Rodríguez, Coral García Vallecillos, Carlos García de los Ríos, Miguel Ángel López Zúñiga, Ramiro Cañaveral Vaccari, Carmen Hidalgo Tenorio, María Rosario Javier Martínez, Juan Pasquau Liaño, Miguel Ángel López-Ruz (Hospital Universitario Virgen de las Nieves), Antonio Plata Ciézar, Beatriz Sobrino Díaz, María Victoria Arijo-García, Óscar Porras-Perales, José María Reguera-Iglesias, Rocío Asensi Díez, Ana Fernández Sánchez, Ignacio Márquez Gómez, Juan Diego Ruíz-Mesa, Lucía Valiente de Santis (Hospital Regional Universitario de Málaga), Carmen Sánchez Cano, Iris El Attar Acedo, María Isabel Rodríguez Higuera (Hospital Universitario Torrecárdenas), María Franco Huerta, Alicia Hidalgo Jiménez, Elena Concejo Martínez, Mercedes de Sousa Baena, Álvaro Sánchez Alcázar del Río, Francisco Javier Carrasco Sánchez, Alberto Tenorio Abreu, Laura Corpa Almazán, Raquel Sánchez del Moral, Pilar Villar Santos, Olalla Montero Pérez, and Álvaro Gragera Martínez (Hospital Universitario Juan Ramón Jiménez).
This study has been supported by the Consejeria de Salud y Familias, Junta de Andalucia, Spain (COVID-19 Research Program. Project code COVID-0013-2020). B.G.G. and J.T.C. are supported by General Sub-Directorate of Networks and Cooperative Research Centers, Ministry of Science and Innovation, Spanish Network for Research in Infectious Diseases [REIPI RD16/0016/0001, RD16/0016/0008]—co-financed by the European Regional Development Fund “A Way to Achieve Europe, Operational Program Smart Growth 2014–2020.” J.C.G. is supported by SCReN (Spanish Clinical Research Network) funded by the ISCIII-Sub-Directorate General for Research Assessment and Promotion through project PT17/0017/0032 and PT20/0039. R.L.L., C.D.L.F., J.T.-C., and B.G.-G. are supported by the Center of Biomedical Investigation Network for Infectious Diseases (CIBERINFEC) funded by ISCIII through projects CB21/13/00049 and CB21/13/00012.
Funding sources had no role in the study design; in the collection, analysis, and interpretation of data; and in the writing of the report or the decision to submit the paper for publication.
Dr. Merchante and Dr. Torre-Cisneros had full access and to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Torre-Cisneros.
Acquisition, analysis, or interpretation of data: All authors.
Statistical analysis: Merchante, Cárcel, Gutiérrez-Gutiérrez and Torre-Cisneros.
Drafting of the manuscript: Merchante.
Critical revision of the manuscript for important intellectual content: All authors.
Obtained funding: Torre-Cisneros.
Study supervision: Merchante and Torre-Cisneros.
The authors have no conflict of interest or financial relationships relevant to the submitted work to disclose. No form of payment was given to anyone to produce the manuscript.