Flavin adenine dinucleotide (FAD) is engaged in several metabolic diseases. Its main role is being a cofactor essential for the activity of many flavoproteins, which play a crucial role in electron transport pathways in living systems. The aim of this study was to apply a pegylated flavins formulation named FAD-PEG diacide complex as theranostic pathway in cancer therapy. For this purpose, a mouse liver cancer model induced by Hepa1-6 cells was used to evaluate the therapeutic efficacy of FAD (named NP1) and FAD-PEG diacide complex (named NP2). The cytokines were applied to screen the serum inflammatory factors, to establish the blood cell content of different groups of nude mice. The highlights follows that FAD formulations (NP1; NP2) significantly suppressed the tumor growth and reduced the tumor index without effects on the body weight of mice. Furthermore, NP2 significantly reduced the serum levels of cytokines IL-6, TNF-α and IL-12 (P70). The reported results provide the proof-of-concept for the synthesis of a smart adjuvant for liver cancer therapy and support their further development in the field of nanomedicine.