for mice: Stock ST1926 (ADAROTENE) solution was diluted in 1:1 cremophor/ethanol solution (10 µL stock ST1926 containing 0.6 mg in 40 µL cremophor/ethanol). Each animal received by gavage 50 µL of ST1926 solutions, equivalent to 30 mg/kg body weight (average mouse weight, 20 g) as this dosage was reported to cause survival advantage in AML mice with no signs of toxicity

Were used 3 HTLV-1–transformed cell lines (HuT-102, MT-2, and C8166) and 3 HTLV-1–negative cell lines (CEM, Jurkat, and MOLT-4) to test for the effects of ST1926 (ADAROTENE) on cell growth and viability. ST1926 concentrations ranging from 0 05 to 5 µM as these are pharmacologically achievable were used. ST1926 treatment resulted in a time-dependent growth inhibition of all tested cell lines. In general, both HTLV-1–negative and –positive cell lines were equally sensitive to ST1926. A threshold level at 0.5 µM concentration was noted, with similar growth suppressive effects as 10-fold higher concentrations, except for CEM cells. 1 µM ST1926 caused a growth inhibition that was almost complete in primary ATL cells from the newly diagnosed acute ATL patients and >60% in the relapsed one. In contrast, resting and phytohemagglutinin-stimulated normal T cells from 3 healthy donors were resistant to ST1926 up to 10 μM.