It also had improved microsome stability (rat, mouse, human LM t1/2 ~17, 37, 777 min, respectively) and aqueous solubility >30 g/mL. Table enumerates the cytotoxic activity of key analogs from our SAR campaign against the four biliary tract cancer cell lines that were used in the screening. As expected, the activity was very similar in the RBE and SNU-1079 cells with mIDH1 with almost complete inactivity against the HuCCT1 and CCLP1 with wt IDH1. The rat liver microsome (RLM) stability was the best for compound 15 and analog 58 was second with RLM t1/2 of 17 min. The passive permeability as determined by PAMPA was high for the chemical series; there were also multiple compounds with improved solubility (Table ). Based on this data, compounds 15 and 58 were advanced to mouse pharmacokinetics. Pharmacokinetics (PK). Compounds 15, 58, and YC-1 (1) were evaluated in mouse PK experiments to help select a candidate for efficacy experiments. The plasma exposure for each compound was evaluated in male CD1 mice after dosing via intravenous (IV), oral (PO), and intraperitoneal (IP) routes at 5, 10, 30 mgkg -1 . Table showcases PK parameters calculated. Highest plasma concentrations, C0 in the IV and Cmax in the IP and PO, were achieved with YC-1 1 in every experiment. Among the three routes of administration, oral route had the lowest AUCs for all three compounds, while the intraperitoneal route offered best exposures with analog 58 having the highest AUC in this set. The in vivo clearance, as determined in the IV dosing experiments, seemed high and similar for all three compounds. This was disappointing as the in vitro microsomal stability, especially for compound 58, was high. We speculate that high clearance could be due to Phase II metabolizing enzymes acting directly on the free alcohol or amine present in these molecules leading to the elimination of the parent from the blood. This rationale is in line with the mechanism by which YC-1 transforms into an alkylator via sulfonation by SULT1A1 which is a Phase II metabolizing enzyme itself. The plasma concentration versus time profiles are plotted in Figure for compounds 1 and 58; both compounds reach peak concentrations in <1 hr and analog 58 is cleared at a slower rate compared to YC-1. YC-1 (1) was dosed as solution in PEG300/30% solutol in water/ Saline (30/17/54) and 58 was dosed as solution in 5% NMP, 20% PEG 300 and 75% of a solutol HS 15 in water (15 wt%). 24-hr time point concentration for YC-1 was below LLQ (Lower limit of quantification).