S3I-201 is primarily used in research settings to study and inhibit the STAT3 signaling pathway, which plays a critical role in cancer development and progression. By blocking STAT3 activation, it helps researchers understand the pathway's involvement in tumor growth, survival, and metastasis. This compound is particularly valuable in preclinical studies for evaluating potential therapeutic strategies targeting STAT3-dependent cancers, such as breast, lung, and prostate cancers. Additionally, S3I-201 is utilized to explore its effects on inflammation and immune responses, as STAT3 is also implicated in these processes. Its application extends to identifying novel drug candidates that can disrupt STAT3 signaling in various diseases.