GSK J5 HCl is the hydrochloride form of GSK J5. GSK J5 is an inactive isomer of GSK J4 and a cell-permeable ester derivative of inactive control GSK J2. Lysine-specific demethylase 6B (KDM6B), also known as Jumonji domain-containing protein D3 (JMJD3), was overexpressed in patients with AML and these patients have a poor prognosis. KDM6B-specific pharmacological inhibitor GSK-J4 had a significant anti-proliferative effect in AML cell lines and freshly isolated BM monocytes (MNCs) from AML patients, while H3K27me3 levels were also increasing. GSK-J4 also caused apoptosis and cell cycle arrest in vitro, and reduced tumor burden in vivo in AML xenograft mouse models. It is worth noting that injection of GSK-J4 attenuated disease progression in a human AML xenograft mouse model. Treatment with GSK-J4 mainly resulted in downregulation of DNA replication and cell cycle-related pathways, and prevents the expression of HOX, a key cancer gene. ChIP-qPCR verified the increased H3K27me3 enrichment in the HOX gene transcription initiation site ^[1].

[1]. Li Y, Zhang M, Sheng M, Zhang P, Chen Z, Xing W, Bai J, Cheng T, Yang FC, Zhou Y. Therapeutic potential of GSK-J4, a histone demethylase KDM6B/JMJD3 inhibitor, for acute myeloid leukemia. J Cancer Res Clin Oncol. 2018 Jun;144(6):1065-1077. doi: 10.1007/s00432-018-2631-7. Epub 2018 Mar 28. PubMed PMID: 29594337; PubMed Central PMCID: PMC5948279.