<p>(A) Dose-response curves of <i>P. falciparum</i> 3D7 in the presence of 916, 024, or 025. EC<sub>50</sub> values are shown. (B) Parasitemia measured at 72 h (<i>y</i>-axis) following drug treatment at rings (30 min postinvasion) and replacement of the medium with inhibitor-free medium (wash-out) at the time intervals shown (<i>x</i>-axis). (C) Parasitemia at 72 h (<i>y</i>-axis) after replacement of inhibitor-free medium with media containing compounds at the intervals shown (<i>x</i>-axis). Parasitemia was determined by FACS in (A–C) and is relative to DMSO treatment in (B) and (C). Concentrations are as follows: 916, 024, 025 (15 µM); CQ, chloroquine (150 ng/ml); ART, artemisinin (100 ng/ml). Error bars in (A–C) are mean ±SEM from duplicate experiments. (D) Light micrographs of Giemsa-stained parasites 16 and 32 h after drug treatment at early rings (15 µM). 916-treated parasites failed to develop into trophozoites and did not recover. Ring parasites treated with E-64 (10 µM) <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001897#pbio.1001897-terKuile1" target="_blank">[22]</a> contained swollen food vacuoles (arrow) due to inhibition of proteases involved in hemoglobin degradation; however, treatment with DMSO, 916, 024, or 025 did not cause swelling. Swelling was quantified using 500 infected cells per condition in duplicate. Scale bar is 6 µm.</p
