Author contributions
Study design and data interpretation: G Lorenzo, M Cepeda, M Ramos, D Saavedra, Z Mazorra, K Leon and T Crombet; clinical investigators (recruited and treated patients): LM Filgueira, JB Cervantes, OA Lovelle, C Herrera, C Figueredo, JA Caballero, N Sánchez, J Berrio, A Caballero; immunological assessments: D Saavedra, AL Añe-Kouri, Z Mazorra; writing and or/revision of the manuscript: T Crombet and A Caballero.

Acknowledgments
We are extremely grateful to all ICU physicians, nurses and general staff working with severe and critically ill COVID-19 patients.

Financial & competing interests disclosure
Seven authors (G Lorenzo, M Cepeda, M Ramos, D Saavedra, Z Mazorra, K Leon and T Crombet) currently work for the Center of Molecular Immunology, the institution that generated and originally patented itolizumab. The remaining authors do not have any commercial or financial relationships that could be taken as a potential conflict of interest. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research
The authors state that they have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. The study was approved by a central ethical review board, created especially for COVID-19 and by the Cuban Regulatory Agency (CECMED). Before the treatment, informed consent was obtained from enrolled patient.

Data sharing statement
The authors certify that this manuscript reports original clinical trial data on three patients, RPCEC00000311. Individual participant data that underlies the results reported in the article, after de-identification (text, tables, figures and supplement) are available along with the study protocol. The data will be available 9 months after article publication and will end 36 months following article publication. The information will be shared with investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose and for individual participant data meta-analysis. Proposals may be submitted up to 36 months following article publication. After this date the data will be available in our data warehouse but without investigator support other than deposited metadata. Information regarding submitting proposal and accessing data may be found at http://rpcec.sld.cu/trials/RPCEC00000311-En