Structure-Activity relationship of 1-(Furan-2ylmethyl)Pyrrolidine-Based Stimulation-2 (ST2) inhibitors for treating graft versus host disease

Prophylactic Mitigation of Acute Graft versus Host Disease by Novel 2-(Pyrrolidin-1-ylmethyl)pyrrole-Based Stimulation-2 (ST2) Inhibitors

“…Modifications within the piperazine ring (23,24) retained the compound activity (IC 50 ∼ 6.0 μM) in the HEK-Blue assay, and 23 had a 3-fold improvement of IC 50 values over 22 according to the AlphaLISA assay (Table 1). Addition of chemical groups to the terminal amine in the piperazine group (25, 27, and 28) or using the methyl and amine group (26) gave IC 50 values similar to 22 in both assays except for 25 and 28. Interestingly, replacement of piperazine with morpholine (29) led to reduced activity (Table 1).…”

“…25,26 Our previous work focused on modifying the phenylpyrrolidine moiety and the nitrophenyl group in iST2-1 to obtain 4 (Figure 1). 26 Compound 4 had improved activity in the AlphaLISA ST2/ IL-33 biochemical activity but had a similar IC 50 value as iST2-1 in the cellular reporter assay (Figure 1). 26 Based on 4, we first replaced the furan ring with a pyrrole ring, which was a more soluble isostere.…”

“…Following our previous studies, we determined the activities of our compounds using two complementary assays, the AlphaLISA ST2/IL-33 biochemical binding assay and the HEK-Blue IL-33 cell-based reporter assay (a functional assay to confirm the inhibitory activity). , Our previous work focused on modifying the phenylpyrrolidine moiety and the nitrophenyl group in iST2-1 to obtain 4 (Figure ). Compound 4 had improved activity in the AlphaLISA ST2/IL-33 biochemical activity but had a similar IC 50 value as iST2-1 in the cellular reporter assay (Figure ). Based on 4 , we first replaced the furan ring with a pyrrole ring, which was a more soluble isostere.…”

“…Our most effective compound, 32 (or XY52 ), showed ∼11-fold selectivity between sST2 and ST2/IL1RAcP, giving IC 50 values of 5.68 ± 1.86 and 64.3 ± 3.2 μM, respectively (Figure ). To further validate the assay, we examined 2 and 3 from our previous study . Compound 2 was a close analogue of iST2-1 and had an improved PK profile over iST2-1 , whereas 3 had a weak inhibitory activity (Figure ).…”

“…Data from an in vitro assessment indicated that 32 had better activity and metabolic stability than 4 developed from our previous study. 26 We then determined the in vivo pharmacokinetic (PK) profile of 32 and compared it with that of our lead, iST2-1. The t 1/2 of 32 in mice was greater than 7 h (much longer than t 1/2 = 1.42 h of iST2-1), but the AUC 0−7h obs of 32 was 2-fold lower than that of iST2-1 (Table S3).…”