Targeting the tumor microenvironment (TME) is an attractive strategy for developing new drugs with anticancer activity against triple-negative breast cancer (TNBC). Interleukins (ILs) are key players in the TME cytokine network promoting cancer progression. Recent studies have highlighted the involvement of IL-20 receptor subunit alpha (IL-20RA) signalling in several cancers, including BC, in which IL-20RA is highly expressed, correlating with poor prognosis and influencing tumoral characteristics such as proliferation, cell death, invasiveness, and TME activity. Therefore, elucidating the role of the IL-20RA signalling pathway could form the basis for developing new therapeutic strategies. This study aimed to identify selective bioactive ligands able to affect IL-20RA activity. Virtual screening of over 310,000 compounds from both the DrugBank and ZINC15 databases identified four potential hit compounds tested for their anticancer activity against TNBC in vitro cell lines. Notably, Ritonavir, a well-known Human Immunodeficiency Virus Type 1 (HIV-1) protease inhibitor, significantly inhibited cell proliferation (about 40% at 50 µM,