Quantitative assessment of antimalarial activity in vitro by a semiautomated microdilution technique

TLDR

The new test system’s applications and expectations within a drug‑development program are discussed. The study developed a rapid, semiautomated microdilution method to measure antimalarial activity against cultured *Plasmodium falciparum* asexual stages. The method uses microtitration plates to prepare serial dilutions, subcultures parasites for 42 h, and measures inhibition of radiolabeled nucleic‑acid precursor uptake, enabling testing of multiple drugs and cross‑resistance evaluation. Repeated measurements with chloroquine, quinine, and mefloquine demonstrated the method is sensitive and precise, and its results for other drugs matched in‑vivo data and allowed cross‑resistance assessment.

Abstract

A rapid, semiautomated microdilution method was developed for measuring the activity of potential antimalarial drugs against cultured intraerythrocytic asexual forms of the human malaria parasite Plasmodium falciparum. Microtitration plates were used to prepare serial dilutions of the compounds to be tested. Parasites, obtained from continuous stock cultures, were subcultured in these plates for 42 h. Inhibition of uptake of a radiolabeled nucleic acid precursor by the parasites served as the indicator of antimalarial activity. Results of repeated measurements of activity with chloroquine, quinine, and the investigational new drug mefloquine demonstrated that the method is sensitive and precise. Several additional antimalarial drugs and compounds of interest were tested in vitro, and the results were consistent with available in vivo data. The use of P. falciparum isolates with known susceptibility to antimalarial drugs also permitted evaluation of the cross-resistance potential of each compound tested. The applications and expectations of this new test system within a drug development program are discussed.