Comparison of the safety and efficacy of fingolimod and tofacitinib in the zebrafish model of colitis

Oral targeted small molecules, including sphingosine 1 phosphate receptor (S1PR) modulators and tyrosine kinase inhibitors (TKIs), seem to revolutionize the management of inflammatory bowel disease (IBD). To select the most effective treatment, there is an unmet need to comparatively study their mechanism of action, efficacy, and toxicity in the preclinical stage and further translate it into clinical practice.Using 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced adult zebrafish colitis model, LC50 of fingolimod and tofacitinib were determined based on the acute toxicity test to compare aquatic toxicity potential. Subsequently, the efficacy of different concentrations of tofacitinib and fingolimod was compared using flow cytometry, qPCR, and histopathology analyses.TNBS significantly reduced the length of villi, and the number of goblet cells increased the level of TNF-α, MyD88, and NF-κB2, the thickness of villi and necrosis, and induced histopathological changes. All of these parameters were reversed almost dose-dependently with both medications, with the highest concentration of fingolimod being superior to other groups. Additionally, results from qPCR analysis suggested that these medications might suppress canonical and non-canonical NF-κB pathways by targeting toll-like receptors and MyD88. LC50 of tofacitinib and fingolimod was 0.9014 and 0.36 mg/L, respectively. Hence, both are in the cory 1 of the Global Harmonization System (GHS) aquatic toxicity and are toxic to adult zebrafish life.Given the better efficacy of fingolimod, it is worth translating the effectiveness and safety of S1PR modulators into IBD patients and comparing them with TKIs in head-to-head studies; albeit, their toxicity should not be overlooked.