mNLS-CPP-WSTFTFA is the trifluoroacetate salt form of mNLS-CPP-WSTF, a cell-penetrating peptide based on the mouse WSTF sequence with a nuclear localization signal (NLS). This compound significantly inhibits the interaction between GABARAP and WSTF, as well as WSTF degradation and the expression of inflammatory genes. It effectively alleviates chronic inflammation, liver fibrosis, and cartilage damage in mouse models of metabolic dysfunction-associated steatotic hepatitis (MASH) and osteoarthritis (OA). mNLS-CPP-WSTF holds research potential for chronic inflammatory diseases such as MASH and OA.