Side-by-side comparisons of PG27 and PG490 for immunosuppressive potency and drug cytotoxicity. T cells from a single donor were pretreated in parallel with DMSO (Ctl) or various concentrations (in serial dilutions) of PG490 or PG27 that contained an equal amount of PG490, and then stimulated with PMA + ionomycin (A) or 3 different stimuli (PMA + ionomycin, CD3/CD28 and TNF-α) as indicated (B) for 24 h. In (A), the concentrations of PG27 and PG490 at 1× (the highest concentration) were 200 ng/mL and 2.56 ng/mL, respectively. In (B), the concentrations of PG27 and PG490 at 1× (the highest concentration) were 6400 ng/mL and 81.28 ng/mL, respectively. The supernatants were collected for the measurement of IL-2 (A) and the cells were collected for the measurement of cytotoxicity by MTT colorimetric assays (B). The results are representative of T cells from at least 3 different donors.