K-41 is a monoglycoside polyether fungal metabolite originally isolated from S. hygroscopicus that has antibiotic and antiparasitic activities.^1,2 It is active against B. subtilis, B. anthracis, S. aureus, S. pyogenes, S. pneumoniae, C. diphtheriae, and M. tuberculosis (MICs = 3.13, 1.56, 1.56, 0.78, 0.39, 0.78, and 3.13 µg/ml, respectively).¹ K-41 is active against the K1 drug-resistant and FCR3 drug-susceptible P. falciparum strains (IC₅₀s = 8.5 and 31 nM, respectively).² In vivo, K-41 has antiparasitic activity in mouse models of P. berghei and P. yoelii infection (ED₅₀s = 1.9 and 7.0 mg/kg, respectively).