Dengue virus (DENV) remains a major global health concern without effective treatments. Previously, we identified sulfonyl anthranilic acid (SAA) derivatives (compounds 1 and 2) as potent pan-DENV inhibitors, likely targeting a primate-specific factor. Here, mass spectrometry-based target deconvolution revealed that SAA compounds downregulate ribosomal protein expression, some of which are essential for DENV replication, as confirmed by siRNA-knockdown studies. This novel mechanism aligns with the broad-spectrum antiviral activity of compounds 1 and 2. Moreover, compound 1 was also effective against the Zika virus in a human brain organoid model. The subsequent medicinal chemistry optimization process resulted in the identification of compound 7, which demonstrated an EC50 value of 50 nM against DENV-2, promising broad-spectrum potential and favorable in vitro ADME properties. Further studies indicated that these compounds modulate the 5'-terminal oligopyrimidine (5'-TOP) motif in ribosomal mRNAs. These findings open a new avenue for antiviral development by targeting a previously unexplored host pathway.