TABLE 1.

IC₅₀s for SIPI 1029 and the clinical trypanocide melarsen oxide against growth of bloodstream-form trypanosomes in vitro^a

Strain	IC50 (nM)
	SIPI 1029	Melarsen oxide
T. b. brucei Lab 110 EATRO	2.15	4.4
T. b. rhodesiense
KETRI 243	0.6	13.0
KETRI 269	0.6	33.0
KETRI 243 As-10-3	0.15	24.0

^aGrowth studies were done in duplicate in 24-well plates, with modified Iscove modified Dulbecco medium (9) as described previously (3). Cell counts were made with a Z1 Coulter Counter after 48 h, and IC₅₀s were determined (7).