The Quinism Foundation Reemphasizes the Need for Caution in the Investigational and Off-Label Use of Tafenoquine Against COVID-19

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The Neurotoxic U.S. Army-Developed Antimalarial Drug is Structurally Related to Hydroxychloroquine and Chloroquine and Carries a Risk of Potentially Severe Neuropsychiatric Adverse Effects

The Quinism Foundation has again called on clinical researchers and prescribers to exercise caution in the investigational and off-label use of tafenoquine against COVID-19, following an announcement by 60 Degrees Pharmaceuticals ("60P"), the marketers of Arakoda®-branded tafenoquine, [1] of a decision by a Data Safety Monitoring Board to recommend continuation of a clinical trial funded by 60P and the Department of Defense Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense, [2] evaluating the safety and efficacy of the drug for treatment of mild-moderate COVID-19 disease in adults aged 18 years of age or older. [3]

"As its 'quine' suffix indicates, tafenoquine is a quinoline antimalarial drug structurally related to hydroxychloroquine and chloroquine," said Dr. Remington Nevin, MD, MPH, DrPH, a former U.S. Army public health physician and Johns Hopkins-trained psychiatric epidemiologist and drug safety expert, who now serves as Executive and Medical Director of The Quinism Foundation.

"All quinoline antimalarial drugs are amphiphilic and diprotic weak bases, which lead to their accumulation in acidic cellular endosomes, the property thought to at least partly underlie the observed antiviral activity of certain previously-tested drugs," said Dr. Nevin. [4,5]

"Unfortunately, as experience with hydroxychloroquine and chloroquine has shown, the same common properties that likely underlie the observed effectiveness of these quinoline antimalarial drugs in-vitro against the virus may also underlie their common dangers," said Dr. Nevin.

"In susceptible individuals, these drugs act as idiosyncratic neurotoxicants, potentially causing irreversible brain and brainstem dysfunction, even when used at relatively low doses," said Dr. Nevin. "This drug-induced dysfunction causes a disease of the brain and brainstem called quinoline encephalopathy, or quinism, which can be marked by lasting psychiatric and neurological symptoms including tinnitus, dizziness, vertigo, paresthesias, visual disturbances, nightmares, insomnia, anxiety, agoraphobia, paranoia, psychosis, cognitive dysfunction, depression, personality change, and suicidal thoughts, among others," said Dr. Nevin. [6]

"In recognition of tafenoquine’s neuropsychiatric liability, the FDA has required language in the approved U.S. drug label for Arakoda® warning of a risk of severe psychotic reactions, and that those taking the drug should be promptly evaluated by a medical professional if psychiatric symptoms occur during use, such as changes in mood, anxiety, insomnia, and nightmares if they are moderate and last more than three days or are severe." [7]

Although the unpublished research paper accompanying 60P's original announcement of its clinical trial [8] suggests "proof of hope" for tafenoquine against COVID-19, in other words, an "expectation that pharmacologically relevant concentrations… can be achieved clinically and a likelihood that a relevant therapeutic index exists," [9] Dr. Nevin notes that tafenoquine's neurotoxicity may significantly narrow the drug's therapeutic index for this proposed indication.

"In U.S. Army research conducted prior to 60P's commercialization of tafenoquine, the drug was found to be the most neurotoxic quinoline among six tested, including mefloquine and chloroquine, and in cultured embryonic rat neurons, exhibited an IC50 of 12.1 µM," said Dr. Nevin. [10] "This is less than threefold the concentration of 5.1 µM exhibiting EC90 against SARS-CoV-2 in VERO E6 cells in 60P's unpublished research paper." [9]

"While these results suggest promise against COVID-19, experience with chloroquine and hydroxychloroquine should temper institutional interest in similar investigational use of tafenoquine," said Dr. Nevin. "Likewise, to ensure adequate informed consent, patients enrolled in the clinical trials underway must also be informed of tafenoquine's inherent neurotoxicity and neuropsychiatric liability.”

“As has been seen from popular interest in another anti-parasitic drug, ivermectin, prescribers may be approached by patients seeking alternatives to FDA-approved medications for prevention and treatment of COVID-19,” said Dr. Nevin. “Particularly given the availability of FDA-approved vaccines and medications for these indications, prescribers should exercise caution against the ill-advised off-label use of either Arakoda®- or Krintafe®-branded tafenoquine, neither of which is FDA-approved for prevention or treatment of COVID-19.”

“With international travel to malaria-endemic areas all but eliminated during the pandemic, and with significantly reduced demand for antimalarial drugs within the U.S. market as a result, such off-label use of Arakoda® could risk becoming the dominant reason for the drug’s prescribing,” said Dr. Nevin. “We encourage 60P to work with FDA, and to be transparent in sharing and monitoring its sales data with interested parties, to ensure the drug is not being widely prescribed for this reason, contrary to its FDA-approved antimalarial indications.”

Dr. Nevin also emphasized the importance of recognizing and properly reporting suspected adverse effects from use of tafenoquine, including when the drug is used off label against COVID-19. "While it may be tempting to attribute anxiety, depression, paranoia, or other mental health symptoms to the psychological effects of the COVID-19 pandemic," said Dr. Nevin, "these symptoms, if they occur during attempted off-label use in prevention or treatment of disease, may be an early warning sign of idiosyncratic quinoline neurotoxicity. Likewise, more severe neuropsychiatric symptoms, including confusion or psychosis, may not necessarily be merely neurologic complications of the disease, but may represent potentially lasting adverse effects from the use the drug."

Dr. Nevin noted that suspected adverse effects from tafenoquine and related quinoline drugs may be reported to the U.S. Food and Drug Administration's MedWatch program, at
https://www.fda.gov/safety/medwatch-fda-safety-information-and-adverse-event-reporting-program.

About The Quinism Foundation

The Quinism Foundation, founded in January 2018, in White River Junction, Vermont, promotes and supports education and research on quinism, the family of medical disorders caused by exposure to quinoline drugs, including tafenoquine, chloroquine, hydroxychloroquine, and mefloquine.

Dr. Nevin is a board-certified occupational medicine and preventive medicine physician and former U.S. Army medical officer and epidemiologist. He is author of more than 30 scientific publications on malaria and the quinoline antimalarials, including “Neuropsychiatric Quinism: Chronic Encephalopathy Caused by Poisoning by Mefloquine and Related Quinoline Drugs,” published in the Springer Nature book, “Veteran Psychiatry in the US."
(https://link.springer.com/chapter/10.1007/978-3-030-05384-0_20).

References

1. 60 Degrees Pharmaceuticals, LLC. Data Safety Monitoring Board Recommends Completion of Phase II Study to Evaluate the Efficacy and Safety of ARAKODA® (tafenoquine) for Treatment of Mild-Moderate Covid-19 Disease. October 12, 2021. Available at: https://www.prnewswire.com/news-releases/data-safety-monitoring-board-recommends-completion-of-phase-ii-study-to-evaluate-the-efficacy-and-safety-of-arakoda-tafenoquine-for-treatment-of-mild-moderate-covid-19-disease-301398568.html

2. Department of Defense. PEO-CBRND Investment Initiates Phase II Clinical Trial Using Tafenoquine to Treat COVID-19. March 12, 2021. Available at: https://www.jpeocbrnd.osd.mil/Media/News/Article/2547624/jpeo-cbrnd-investment-initiates-phase-ii-clinical-trial-using-tafenoquine-to-tr/

3. 60 Degrees Pharmaceuticals, LLC . Tafenoquine in Patients With Mild to Moderate COVID-19. ClinicalTrials.gov Identifier: NCT04533347. Available at: https://clinicaltrials.gov/ct2/show/NCT04533347

4. Vincent MJ, Bergeron E, Benjannet S, et al. Chloroquine is a potent inhibitor of SARS coronavirus infection and spread. Virology journal. 2005;2:69.

5. Yao X, Ye F, Zhang M, et al. In Vitro Antiviral Activity and Projection of Optimized Dosing Design of Hydroxychloroquine for the Treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Clinical infectious diseases. 2020;7:732-739.

6. Nevin RL. Neuropsychiatric Quinism: Chronic Encephalopathy Caused by Poisoning by Mefloquine and Related Quinoline Drugs. In: Ritchie EC, Llorente MD, eds. Veteran Psychiatry in the US. Cham: Springer International Publishing; 2019:315-331.

7. 60 Degrees Pharmaceuticals. Arakoda (tafenoquine) Prescribing Information. August 2018. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/210607lbl.pdf

8. 60 Degrees Pharmaceuticals, LLC. 60 Degrees Pharmaceuticals Announces Positive Results of Cell Culture Testing of ARAKODA® (tafenoquine) for COVID-19. July 14, 2020. Available at: https://www.businesswire.com/news/home/20200714005355/en/60-Degrees-Pharmaceuticals-Announces-Positive-Results-of-Cell-Culture-Testing-of-ARAKODA®-tafenoquine-for-COVID-19

9. Dow GS, Dc W, Fenner J, Yeo KR. Tafenoquine inhibits replication of SARS-Cov-2 at pharmacologically relevant concentrations in vitro. 2020. bioRxiv 2020.07.12.199059. Available at: https://doi.org/10.1101/2020.07.12.199059

10. Agboruche RL. 529.3 In-Vitro Toxicity Assessment of Antimalarial Drug Toxicity on Cultured Embryonic Rat Neurons, Macrophage (RAW 264.7), and Kidney Cells (VERO-CCl-81). FASEB Journal. 2009;23(1 Meeting Abstract Supplement):529.3.

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