Objectives: In the context of COVID-19, patients with severe or critical illness may be more susceptible to developing secondary bacterial infections. This study aims to investigate the relationship between the use of prophylactic antibiotic therapy and the occurrence of bacterial or fungal isolates following the administration of tocilizumab in hospitalized COVID-19 patients who had previously received steroids during the first and second waves of the pandemic in Spain. Methods: This retrospective observational study included 70 patients hospitalized with COVID-19 who received tocilizumab and steroids between January and December 2020. Data on demographics, comorbidities, laboratory tests, microbiologic results, treatment, and outcomes were collected from electronic health records. Patients were divided into two groups based on the use of antibiotic prophylaxis, and the incidence of bacterial and fungal colonizations/infections was analyzed. Results: Among the included patients, 45 patients received antibiotic prophylaxis. No significant clinical differences were observed between patients based on prophylaxis use regarding the number of clinically diagnosed infections, ICU admissions, or mortality rates. However, patients who received antibiotic prophylaxis showed a higher incidence of colonization by multidrug-resistant germs compared to the subgroup that did not receive prophylaxis. The most commonly isolated microorganisms were Candida albicans, Enterococcus faecalis, Staphylococcus aureus, and Staphylococcus epidermidis. Conclusions: In this cohort of hospitalized COVID-19 patients treated with tocilizumab and steroids, the use of antibiotic prophylaxis did not reduce the incidence of secondary bacterial infections. However, it was associated with an increased incidence of colonization by multidrug-resistant organisms.

The interleukin 6 (IL-6) receptor blocking antibody tocilizumab was repurposed in the coronavirus pandemic with the intention of blocking the excess inflammatory activation associated with severe disease. We retrospectively evaluated the response to tocilizumab based on measured levels of IL-6 as well as other inflammatory markers. In the sample of 41 patients with measured levels, 16 received tocilizumab. In patients who received tocilizumab, there was a statistically significant relationship between both higher IL-6 levels and measured acute phase reactants with mortality, but not in those who did not. Additionally, an improved mortality after tocilizumab was suggested with those with higher IL-6 measurements, but not in those with lower levels, but this finding failed to achieve statistical significance (p=0.14). Though this study is limited by a small sample size and retrospective design, an association is suggested between higher IL-6 levels and improved mortality after tocilizumab.

Tocilizumab against interleukin-6 receptor (IL-6R) has been demonstrated to inhibit the progression of diverse cancers in vitro and in vivo. Nonetheless, evidence regarding the anti-tumor effects of Tocilizumab on human colorectal carcinoma (CRC) corresponding to IL-6R expression levels re-mains scarce. To investigate the influence of IL-6R expression, SW480 and HT-29 cells inoculated subcutaneously into NU/NU mice were used as our human CRC xenograft models with anti-IL-6R antibody (Tocilizumab) therapy. IL-6R expression levels, the histology of CRC growth/ invasiveness and tumor growth-related signaling pathway were estimated by H&E and immunohistochemical staining. SW480 tumor cells with higher IL-6R expression levels exerted better responsiveness in Tocilizumab therapy than the treated HT-29 group. Likewise, therapeutic effects of Tocilizumab on the proliferative ability with mitotic index and Ki-67 expressions, the invasiveness with MMP-9 proteinase expressions, ERK 1/2 and STAT3 signaling transduction in SW480 treatment group were superior to HT-29 treatment group. In light of our results, IL-6R is the key indicator for the efficacy of Tocilizumab treatment in CRC xenografts. From the perspective of precision medicine, tumor response to anti-IL-6R antibody therapy could be predicted on the basis of IL-6R expression levels. In this manner, Tocilizumab may serve as a targeted and promising anti-CRC therapy.

Systemic lupus erythematosus (SLE), the prototype of systemic autoimmune diseases is characterized by extreme heterogeneity with a variable clinical course. Renal involvement may be observed and affects the outcome. Hydroxychloroquine is the cornerstone of lupus treatment. Conventional immunosuppressive therapy includes corticosteroids, methotrexate, azathioprine, cyclosporine and tacrolimus. Cyclophosphamide and mycophenolate mofetil may also be used. However, despite conventional immunosuppressive treatment flares occur and broad immunosuppression is accompanied by multiple side effects. Flare occurrence, target organ involvement, side effects of broad immunosuppression, increased knowledge of the pathogenetic mechanisms involved in SLE pathogenesis as well as the availability of biologic agents has led to the application of biologic agents in SLE management. Biologic agents targeting various pathogenetic paths have been applied. B cell targeting agents have been used successfully. Belimumab, a B cell targeting agent has been approved for the treatment of SLE. Rituximab, an anti-CD20 targeting agent is also used in SLE. Anifrolumab, an interferon I receptor targeting agent has beneficial effects on SLE. In conclusion, biologic treatment is applied in SLE and should be further evaluated with the aim of a good treatment response and a significant improvement in quality of life.