Wednesday, May 6, 2015

Drugs in Clinical Pipeline: Uprosertib

Uprosertib [N-((S)-1-amino-3-(3,4-difluorophenyl)propan-2-yl)-5-chloro-4-(4-chloro-1-methyl-1H-pyrazol-5-yl)furan-2-carboxamide] is an orally available, ATP-competitive, pan-AKT kinase inhibitor (IC50 AKT1, AKT2, AKT3 = 180, 328, 38 nM). Cells treated with Uprosertib show decreased phosphorylation of several substrates downstream of AKT. Uprosertib has desirable pharmaceutical properties and daily oral dosing results in a sustained inhibition of AKT activity as well as inhibition of tumor growth in several mouse tumor models of various histologic origins. Improved kinase selectivity was associated with reduced effects on glucose homeostasis as compared to previously reported ATP-competitive AKT kinase inhibitors [1,2].

Uprosertib is also time dependant and fully reversible inhibitors of the AKT kinase family with Ki of 0.066, 1.4 and 1.5 nM against AKT1, AKT2 and AKT3, respectively. It is in Phase I human trials [2].

The activity of Uprosertib is as follows:

IC50 (AKT1 enzyme assay) = 180 nM; Ki = 0.066 nM
IC50 (AKT2 enzyme assay) = 328 nM; Ki = 1.4 nM
IC50 (AKT3 enzyme assay) = 38 nM; Ki = 1.5 nM

Common Name: Uprosertib
Synonyms:  GSK-2141795; GSK2141795; GSK 2141795; GSK795; GSK-795; GSK 795
IUPAC Name: N-((S)-1-amino-3-(3,4-difluorophenyl)propan-2-yl)-5-chloro-4-(4-chloro-1-methyl-1H-pyrazol-5-yl)furan-2-carboxamide
CAS Number: 1047634-65-0; 1047635-80-2 (hydrochloride)
Mechanism of Action: Kinase Inhibitor; pan-AKT Inhibitors
Indication: Various Cancers; Solid Tumors
Development Stage: Phase I
Company: GlaxoSmithKline

The AKTs are a family of serine-threonine kinases and an integral component in the signaling cascade downstream of PI3K and PTEN which work to catalyze the formation of PIP3 membrane lipids from PIP2 and back, respectively. PIP3 lipids tether the AKT kinases to the membrane via their plextrin homology domain which enables activation by phosphorylation on Thr308 by PDK1 and Ser473 by the mTORC2 complex. Activated AKT phosphorylates a variety of proteins (e.g. FOXO, TSC1/2, PRAS40, GSK3ß) involved in cell survival, growth and proliferation. Given the importance of this pathway in various cancers, a number of small molecules targeting PI3K with and without mTOR inhibition are being evaluated in patients. Several AKT inhibitors have also entered clinical development; however some of them block activation of AKT rather than inhibiting kinase activity.Activation of the PI3K-AKT pathway is common in many human malignancies leading to an increase in cell survival, growth and proliferation; all necessary hallmarks of a cancer cell. This pathway is up-regulated in cancer cells as a result of a variety of genetic alterations including over-expression of or activating mutations in receptor tyrosine kinases (e.g. ERBB2 or MET), activating mutations in PI3K subunits, loss or promoter methylation of PTEN and over-expression of or mutations in the AKTs.

Uprosertib inhibit the kinase activity of the E17K AKT 1 mutant protein in a standard kinase assay with EC50 of 0.2 nM. Uprosertib was tested against a diverse panel of kinase assays at GlaxoSmithKline and Millipore. Initially, the compounds were tested at 0.5 and 10 µM in all available kinase assays and were followed up with full IC50 curves against a subset of enzymes that showed strong inhibition against 0.5 µM, for which in-house assay were not available. Kinase selectivity was evaluated at 0.5 and 10 µM compound concentration against a panel of 261 different kinase assays, including more than 225 unique kinases together with some mutant forms and some orthologs from mouse, rat or yeast origin. The majority of the enzymes tested (~90%) showed more than 50% inhibition at 0.5 µM of both compounds. Most of the enzymes that were inhibited greater than 50% at 0.5 µM belonged to the AGC family including PKA, PKC, and PKG isoforms. IC50 values were generated for some enzymes (PKA, PKCβ1, PKCβ2, PKG1α, PKG1β = 2.0, 56, 86, less than 1, less than 1 nM, respectively).

In a diverse cell line proliferation screen, Uprosertib showed increased potency in cell lines with an activated AKT pathway (via PI3K/PTEN mutation or loss) while cell lines with activating mutations in the MAPK pathway (KRAS/BRAF) were less sensitive to AKT inhibition. Further investigation in mouse models of KRAS driven pancreatic cancer confirmed that combining the AKT inhibitor, Uprosertib with a MEK inhibitor (GSK2110212; trametinib) resulted in an enhanced anti-tumor effect accompanied with greater reduction in phospho-S6 levels. Taken together these results support clinical evaluation of the AKT inhibitors in cancer, especially in combination with MEK inhibitor [2].

1. Pachl, F.; et. al. Characterization of a chemical affinity probe targeting Akt kinases. J Proteome Res 2013, 12(8), 3792-3800.
2. Dumble, M.; et. al. Discovery of novel AKT inhibitors with enhanced anti-tumor effects in combination with the MEK inhibitor. PLoS One 2014, 9(6), e100880.
3. A Phase I, Open-Label, First-Time-In-Human Study of the Oral AKT Inhibitor GSK2141795. NCT00920257 (retrieved 05-05-2015)
4. GSK2141795, Dabrafenib, and Trametinib in Treating Patients With Stage IIIC-IV Cancer. NCT01902173 (retrieved 05-05-2015)
5. GSK1120212+GSK2141795 for Cervical Cancer. NCT01958112 (retrieved 05-05-2015)