Chinese COVID-19 experts reveal their take on convalescent plasma and tocilizumab
A webinar hosted by China Global Television Network (CGTN) on 20 April saw a panel of experts from China sharing their experience on using convalescent plasma and tocilizumab in the treatment of COVID-19 with colleagues from the US and Canada.
The panel of doctors from China consisted of Dr Aijun Pan, chief physician of Intensive Care Unit, First Affiliated Hospital of University of Science and Technology of China (USTC), Anhui; Dr Wei-Wei, chief physician of the Department of Radiology, First Affiliated Hospital of USTC; Professor Dr Shang You, director of Critical Care Medicine Department, Jin Yin-tan Hospital, Wuhan; Professor Dr Binqing Fu, professor of immunology, USTC; Dr Xinming Qin , associate professor of environment and health sciences, Anhui University, China. In their presentation, the experts covered two major topics—convalescent plasma and tocilizumab use in COVID-19 patients.
In some patients, pathogenic T-cells and inflammatory monocytes with high interleukin-6 (IL-6) secretion may enter the pulmonary circulation in large numbers. This leads to the ‘cytokine storm’ or cytokine release syndrome associated with severe disease. [J Transl Med 2020;18,164. https://doi.org/10.1186/s12967-020-02339-3] Tocilizumab, a monoclonal antibody that targets both soluble and membrane bound IL-6 receptors, is thus able to inhibit the proinflammatory effects of COVID-19.
When a preliminary clinical trial was carried out on 21 patients using tocilizumab and standard therapy, the panel said the fever subsided and other symptoms improved ‘remarkably.’ One patient no longer needed oxygen therapy while another 15 had lower need for oxygen supplementation. They noted that abnormally high C-reactive protein levels decreased significantly in 84.2 percent of the patients. More importantly, no obvious adverse effects were observed in the treated patients and 19 patients were discharged on average 13.5 days after treatment with tocilizumab. Finally, chest computed tomography (CT) scans of the patients showed significant remission in both lungs. [Effective Treatment of Severe COVID-19 patients with Tocilizumab, PNAS 2020, In Press]
The positive outcomes resulted in tocilizumab being included in the seventh edition of the diagnosis and treatment programme of COVID-19 of the national health commission of China.
Another treatment option discussed at the webinar was the use of convalescent plasma. While there have been reports of promising results arising from its use, the Chinese panel noted that convalescent plasma use brought along many confounding factors and complications. One of the main requisites is a large enough population of people who have recovered from COVID-19 to serve as donor pool. Secondly, not every donor has sufficient therapeutic antibody titre. Additionally, the blood and plasma would require proper storage facilities.
As convalescent plasma requires blood extraction, storage and testing of various parameters, a properly equipped facility with blood bank capability is required, they noted.
Ed: The concern of immunosuppression attributed to tocilizumab use was also addressed. It was suggested that IL-6 inhibitors might suppress only the immune responses governed by IL-6, thus leaving other immune responses intact and able to fight the COVID-19 disease. Steroids, however, will suppress both macrophages and CD4 T-cells, which are responsible for initiating immune responses. Steroids also suppress CD8 T-cells, which are capable of killing virus infected cells.