Celastrol suppresses SARS‐CoV‐2 in vitro propagation in nonhuman and human cell lines. RT‐PCR quantification of SARS‐CoV‐2 RNA in supernatants from the infected cell lines (a) Vero CCL‐81, (b) Caco‐2, and (c) Calu‐3, and (d) Calu‐3 infected with SARS‐CoV‐2 gamma variant treated with celastrol at concentrations of 125, 250, 500, and 1000 nM. DMSO solution (0.05%; vehicle) was used as a negative control. Cells were infected using MOI = 1.0 for 2 h and then treated with celastrol for 48 h. The detection levels of SARS‐CoV‐2 RNA were performed in the supernatants of cultures and expressed in viral load using a standard curve described in Section 2. Statistical differences between celastrol treatments and the negative control were analyzed by ANOVA followed by Tukey's posttest. The significance levels were indicated as *p < .05, **p <.01, ***p < .001, and ****p < .0001. ANOVA, analysis of variance; MOI, multiplicity of infection; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2.