Chloroquine (phosphate)

Chloroquine is an aminoquinoline that is an inhibitor of autophagy and has antimalarial, anti-inflammatory, anticancer, and antiviral activities.^1,2,3,4,5 Chloroquine inhibits autophagosome-lysosome fusion in HeLa cells when used at a concentration of 100 µM.¹ It is active against the chloroquine-sensitive GC03 strain of P. falciparum (IC₅₀ = 29.2 nM) but has decreased activity against mutant pfcrt P. falciparum (IC₅₀s = 100-150 nM).³ Chloroquine prevents infection by severe acute respiratory coronavirus 2 (SARS-CoV-2) in Vero cells (EC₅₀ = 1.13 µM) but does not inhibit SARS-CoV replication in the lungs in a mouse model of SARS-CoV infection.^5,6 It inhibits the growth of human SSC25 and CAL 27 oral squamous cell carcinoma cells (IC₅₀s = 29.9 and 17.3 µM, respectively), as well as A498, SN12C, RXF 393, and 769-P renal cancer cells (IC₅₀s = 16, 62, 81, and 25 µM, respectively).^4,7 It reduces tumor growth in a CAL 27 mouse xenograft model and a 4T1 mouse allograft model when administered at a dose of 50 mg/kg.^4,8 Formulations containing chloroquine have been used in the prevention of malaria, as well as the treatment of rheumatoid arthritis and systemic lupus erythematosus (SLE), and have been associated with cardiotoxicity and myopathy.

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1. Mauthe, M., Orhon, I., Rocchi, C., et al. Chloroquine inhibits autophagic flux by decreasing autophagosome-lysosome fusion. Autophagy 14(8), 1435-1455 (2018).

2. Plantone, D., and Koudriavtseva, T. Current and future use of chloroquine and hydroxychloroquine in infectious, immune, neoplastic, and neurological diseases: A mini-review. Clin. Drug Investig. 38(8), 653-671 (2018).

3. Sidhu, A.B.S., Verdier-Pinard, D., and Fidock, D.A. Chloroquine resistance in Plasmodium falciparum malaria parasites conferred by pfcrt mutations. Science 298(5591), 210-213 (2002).

4. Jia, L., Wang, J., Wu, T., et al. In vitro and in vivo antitumor effects of chloroquine on oral squamous cell carcinoma. Mol. Med. Rep. 16(5), 5779-5786 (2017).

5. Wang, M., Cao, R., Zhang, L., et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res. 30(3), 269-271 (2020).

6. Barnard, D.L., Day, C.W., Bailey, K., et al. Evaluation of immunomodulators, interferons and known in vitro SARS-coV inhibitors for inhibition of SARS-coV replication in BALB/c mice. Antivir. Chem. Chemother. 17(5), 275-784 (2006).

7. Grimaldi, A., Santini, D., Zappavigna, S., et al. Antagonistic effects of chloroquine on autophagy occurrence potentiate the anticancer effects of everolimus on renal cancer cells. Cancer Biol. Ther. 16(4), 567-579 (2015).

8. Jiang, P.-D., Zhao, Y.-L., Deng, X.-Q., et al. Antitumor and antimetastatic activities of chloroquine diphosphate in a murine model of breast cancer. Biomed. Pharmacother. 64(9), 609-614 (2010).