PU-WS13

PU-WS13 is a purine scaffold-based Grp94-specific heat shock protein 90 (Hsp90) inhibitor^[1]. In humans, Hsp90α and Hsp90β in the cytoplasm, Grp94 in the endoplasmic reticulum, and Trap-1 in the mitochondria are the four Hsp90 paralogs^[2]. The mechanism of action of PU-WS13 is to block the formation of the Grp94-IgG complex by occupying the ATP site in Grp94^[3].

In vitro, treatment of M2 macrophages with PU-WS13 (25μM) for 72h blocked Grp94 secretion induced by thapsigargin (Tg), attenuated endoplasmic reticulum (ER) stress, reduced the secretion of proinflammatory factors IFNγ, IL-6, and TNFα, and reduced intracellular cathepsin L^[4]. Treatment of MV4-11 cells expressing FLT3-ITD with PU-WS13 (50μM) for 24h significantly reduced cell survival and induced cell membrane translocation^[5].

In vivo, treatment of wild-type mice with PU-WS13 (15mg/kg) by intraperitoneal injection inhibited Grp94, thereby limiting tumor growth and collagen content, and increased the number of CD8⁺ cells in the tumor microenvironment (TME)^[6]. Intratracheal treatment of mice co-infected with influenza A virus and Streptococcus pneumoniae with PU-WS13 (20mg/kg) significantly reduced bacterial colonization in the lungs, improved lung pathology, and restored E-cadherin expression in lung tissues^[7].

References:
[1] Wu B X, Hong F, Zhang Y, et al. GRP94/gp96 in cancer: biology, structure, immunology, and drug development[J]. Advances in cancer research, 2016, 129: 165-190.
[2] Patel P D, Yan P, Seidler P M, et al. Paralog-selective Hsp90 inhibitors define tumor-specific regulation of HER2[J]. Nature chemical biology, 2013, 9(11): 677-684.
[3] Tramentozzi E, Finotti P. Effects of purine-scaffold inhibitors on HUVECs: Involvement of the purinergic pathway and interference with ATP. Implications for preventing the adverse effects of extracellular Grp94[J]. Biochemistry and Biophysics Reports, 2019, 19: 100661.
[4] Chaumonnot K, Masson S, Sikner H, et al. The HSP GRP94 interacts with macrophage intracellular complement C3 and impacts M2 profile during ER stress[J]. Cell death & disease, 2021, 12(1): 114.
[5] Wang F, Baverel V, Chaumonnot K, et al. The endoplasmic reticulum stress protein GRP94 modulates cathepsin L activity in M2 macrophages in conditions of obesity-associated inflammation and contributes to their pro-inflammatory profile[J]. International Journal of Obesity, 2024: 1-11.
[6] Bouchard A, Sikner H, Baverel V, et al. The GRP94 inhibitor PU-WS13 decreases M2-like macrophages in murine TNBC tumors: a pharmaco-imaging study with 99mTc-Tilmanocept SPECT[J]. Cells, 2021, 10(12): 3393.
[7] Sumitomo T, Nakata M, Nagase S, et al. GP96 drives exacerbation of secondary bacterial pneumonia following influenza A virus infection[J]. Mbio, 2021, 12(3): 10.1128/mbio. 03269-20.