(A) MTT assay showing the viability of SK-MEL-28, SK-MEL-5 and SK-MEL-2 cells treated with either DMSO or 10, 20, 50 μmol/L of RRD-251 for 24 hr. Absorbance given by vehicle treated cells was taken as 100% cell survival. Data represent the average ± S.D. from three independent experiments. (B) RRD-251 inhibits the anchorage independent growth of SK-MEL-28, SK-MEL-5 and SK-MEL-2 cells in soft agar. Photographs shown are representative of three independent experiments. (C) RRD-251 inhibits the growth of SK-ME-28 xenograft in nude mice. SK-MEL-28 cells mixed with Matrigel were xenotransplanted bilaterally into the flanks of athymic nude mice and allowed to grow for 14 days until xenograft were established. Data represents the average tumor volume ± S.E. (D) Daily administration of RRD-251 for 15 days did not show any treatment associated body weight loss. Data represent the body weight of 5 different mice, before and after the treatment.