In Vitro and In Vivo Assessment of FK506 Analogs as Novel Antifungal Drug Candidates

• Published in: Antimicrobial agents and chemotherapy 2018-11, Vol.62 (11)
• Main Authors: Lee, Yeonseon, Lee, Kyung-Tae, Lee, Soo Jung, Beom, Ji Yoon, Hwangbo, Areum, Jung, Jin A, Song, Myoung Chong, Yoo, Young Ji, Kang, Sang Hyeon, Averette, Anna F, Heitman, Joseph, Yoon, Yeo Joon, Cheong, Eunji, Bahn, Yong-Sun
• Format: Article
• Language: English
• Subjects: Antifungal Agents; Pharmacology; Tacrolimus
• ISSN: 0066-4804; 1098-6596
• DOI: 10.1128/AAC.01627-18

FK506 (tacrolimus) is an FDA-approved immunosuppressant indicated for the prevention of allograft rejections in patients undergoing organ transplants. In mammals, FK506 inhibits the calcineurin-nuclear factor of activated T cells (NFAT) pathway to prevent T-cell proliferation by forming a ternary complex with its binding protein, FKBP12, and calcineurin. FK506 also exerts antifungal activity by inhibiting calcineurin, which is essential for the virulence of human-pathogenic fungi. Nevertheless, FK506 cannot be used directly as an antifungal drug due to its immunosuppressive action. In this study, we analyzed the cytotoxicity, immunosuppressive activity, and antifungal activity of four FK506 analogs, 31- -demethyl-FK506, 9-deoxo-FK506, 9-deoxo-31- -demethyl-FK506, and 9-deoxo-prolyl-FK506, in comparison with that of FK506. The four FK506 analogs generally possessed lower cytotoxicity and immunosuppressive activity than FK506. The FK506 analogs, except for 9-deoxo-prolyl-FK506, had strong antifungal activity against and , which are two major invasive pathogenic yeasts, due to the inhibition of the calcineurin pathway. Furthermore, the FK506 analogs, except for 9-deoxo-prolyl-FK506, had strong antifungal activity against the invasive filamentous fungus Notably, 9-deoxo-31- -demethyl-FK506 and 31- -demethyl-FK506 exhibited robust synergistic antifungal activity with fluconazole, similar to FK506. Considering the antifungal efficacy, cytotoxicity, immunosuppressive activity, and synergistic effect with commercial antifungal drugs, we selected 9-deoxo-31- -demethyl-FK506 for further evaluation of its antifungal efficacy in a murine model of systemic cryptococcosis. Although 9-deoxo-31- -demethyl-FK506 alone was not sufficient to treat the cryptococcal infection, when it was used in combination with fluconazole, it significantly extended the survival of -infected mice, confirming the synergistic antifungal efficacy between these two agents.