SMI-4a is a selective inhibitor of Pim1 with IC50 value of 17 nM [1] [2].

Pim-1 is an enzyme that is encoded by human PIM1 gene and it has been revealed that Pim-1 directly involved in the regulation of cell cycle progression and apoptosis and many studies have shown that Pim were over-expressed and promote cell growth and survival in a veraity of solid cancers and hematologic malignancies [3, 4].

SMI-4a is a selective Pim inhibitor and more active than the reported SMI-16a. When tested with human erythroleukemia cell line K562 cells, SIM-4a treatment modulated cell growth and activated AMPK which inhibited mTORC1 activity by inhibiting Pim activity [5]. In 25 leukemic cell lines, administration of SMI-4a induced cell-cycle arrest, elevated cell apoptosis, and pre–T-LBL/T-ALL being the highly sensitive cell line through mitochondrial pathway and inhibition of the mTORC1 pathway [2].

In Nu/nu nude mice model with 2 × 106 6812/2 cells subcutaneous xenograft, oral administration of SMI-4a from the third day for 5 of 7 days per week until day 21 on twice daily schedule significantly reduced tumor sizse [2].

References:
[1].  Beharry, Z., et al., Novel benzylidene-thiazolidine-2,4-diones inhibit Pim protein kinase activity and induce cell cycle arrest in leukemia and prostate cancer cells. Mol Cancer Ther, 2009. 8(6): p. 1473-83.
[2].  Lin, Y.W., et al., A small molecule inhibitor of Pim protein kinases blocks the growth of precursor T-cell lymphoblastic leukemia/lymphoma. Blood, 2010. 115(4): p. 824-33.
[3].  Liu, Z., et al., Computational prediction and experimental validation of a novel synthesized pan-PIM inhibitor PI003 and its apoptosis-inducing mechanisms in cervical cancer. Oncotarget, 2015.
[4].  Warfel, N.A. and A.S. Kraft, PIM kinase (and Akt) biology and signaling in tumors. Pharmacol Ther, 2015.
[5].  Beharry, Z., et al., The Pim protein kinases regulate energy metabolism and cell growth. Proc Natl Acad Sci U S A, 2011. 108(2): p. 528-33.