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Antimalarial Quinacrine and Chloroquine Lose Their Activity by Decreasing Cationic Amphiphilic Structure with a

Tomohisa Kitagawa¹, Atsushi Matsumoto¹, Ichiro Terashima¹

¹Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Journal of Medicinal Chemistry

|March 29, 2021

Summary

Quinacrine and chloroquine exhibit antimicrobial and antiviral effects by forming a cationic amphiphilic drug (CAD) structure. This structure is pH-dependent, impacting their efficacy in acidosis, suggesting pH-insensitive drugs may be more effective.

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Area of Science:

Pharmacology
Microbiology
Infectious Diseases

Background:

Quinacrine (QC) and chloroquine (CQ) possess known antimicrobial, antiviral, and antimalarial activities.
The precise mechanisms underlying these activities remain largely unelucidated.
Both drugs are classified as cationic amphiphilic drugs (CADs).

Purpose of the Study:

To investigate the pH-dependent mechanisms of QC and CQ antimicrobial activity.
To determine the role of the cationic amphiphilic drug (CAD) structure in their pharmacological effects.
To explore implications for treating infectious diseases, particularly in patients with acidosis.

Main Methods:

Assessed the antimicrobial activity of QC against yeast at varying pH levels.
Investigated the localization and cellular effects of QC in yeast, including glucose uptake inhibition.
Compared the pH-dependent CAD formation and activity of QC and CQ with other quinoline drugs (quinine, primaquine, mefloquine).

Main Results:

QC's antimicrobial activity increased exponentially with pH-dependent CAD formation, localizing to yeast membranes and inducing glucose starvation.
CQ also demonstrated pH-dependent CAD formation correlating with increased antimicrobial activity.
Reduced CAD structure at pH < 7.4 significantly diminished QC and CQ efficacy, suggesting potential resistance in acidosis.
Quinine, primaquine, and mefloquine did not exhibit this pH-dependent decrease in CAD structure.

Conclusions:

The cationic amphiphilic drug (CAD) structure is critical for the antimicrobial and antiviral activities of quinacrine and chloroquine.
The efficacy of these drugs is compromised in acidic conditions (acidosis) due to a decrease in CAD formation.
Strategies such as restoring normal blood pH or utilizing pH-insensitive quinoline drugs may be beneficial for treating infectious diseases like falciparum malaria and COVID-19 pneumonia in patients with acidosis.