Saturday, May 23, 2015

Drugs in Clinical Pipeline: AZD1208

AZD1208 [5-[[2-[(3R)-3-Aminopiperidin-1-yl]biphenyl-3-yl]methylidene]-1,3-thiazolidine-2,4-dione] is a highly selective, orally available ATP-competitive inhibitor of all three Pim isoforms. The Ki values were determined for Pim-1, Pim-2, Pim-3 to be as 0.1 nM, 1.92 nM, 0.4 nM, respectively. In enzymatic assays carried out at a concentration of ATP that leads to half-maximal reaction velocity, AZD1208 inhibited kinase activity with an IC50 of 0.4 nM for Pim-1, 5.0 nM for Pim-2, and 1.9 nM for Pim-3. In enzyme assays using 5 mM ATP, the high end of physiologic ATP concentration in human cells, the IC50 values were 2.6 nM for Pim-1, 164 nM for Pim-2, and 17 nM for Pim-3 [1].

The efficacy of AZD1208 in cultured acute myeloid leukemia (AML) cell lines, tumor xenograft models, and ex vivo cultures of primary tumor cells from Flt3-ITD and Flt3 wild-type patients is demonstrated, as well as accompanying modulation of Pim signaling substrates that can contribute to the inhibition of tumor growth. The results have supported the initiation of phase 1 clinical trials of AZD1208 in AML.

The activity of AZD1208 is as follows:

IC50 (Pim-1 enzyme assay) = 0.4 nM; Ki = 0.1 nM
IC50 (Pim-2 enzyme assay) = 5.0 nM; Ki = 1.92 nM
IC50 (Pim-2 enzyme assay) = 1.9 nM; Ki = 0.4 nM

Common Name: AZD1208
Synonyms: AZD-1208;  AZD1208;  AZD 1208
IUPAC Name: 5-[[2-[(3R)-3-Aminopiperidin-1-yl]biphenyl-3-yl]methylidene]-1,3-thiazolidine-2,4-dione
CAS Number: 1204144-28-4
Mechanism of Action: Kinase Inhibitor; pan-PIM Inhibitor
Indication: Various Cancers; Treatment of Acute Myeloid Leukemia
Development Stage: Phase I
Company: AstraZeneca

The Pim serine/threonine kinase family is composed of three highly homologous members, Pim-1, -2, and -3, identified as proviral insertion sites of the Moloney murine leukemia virus associated with the development of T-cell lymphomas. Pim-1 and Pim-2 are upregulated in several hematologic malignancies, including acute myeloid leukemia (AML), chronic lymphocytic leukemia (CML), acute lymphoblastic leukemia (ALL), multiple myeloma (MM), and non-Hodgkin lymphoma. In AML, this is driven at least in part by activation of receptor tyrosine kinases such as the Flt3-internal tandem duplication (Flt3-ITD) mutation found in approximately one third of AML patients.

To access selectivity of AZD1208 for Pims relative to other kinases, it was evaluated against a panel of 442 kinases using the DiscoveRx KINOMEscan competition binding assay. The three Pim kinases showed the highest percentage of inhibition. In addition, 13 other kinases were found to be inhibited by 50% or more. No inhibition of Flt3 or Flt3-ITD was observed. A dose-response follow-up conducted against the 13 kinases inhibited greater than 50% showed AZD1208 to bind tightly to Pim-1, -2, and -3 with binding constants (Kd) of 0.2 nM, 0.88 nM, and 0.76 nM, respectively, comparable to the Ki determined in functional enzyme assays. AZD1208 bound six other kinases (CDK7, MAPK15, CAMK4, DAPK1, HIPK3, STK17B) with potencies ranging from 38 nM to 930 nM, but did not show significant binding to the remaining seven kinases (Kd >10 ┬ÁM). The potency difference between affinity of AZD1208 for Pim kinases and the next most potent “hit” in the panel (CDK7, Kd = 38.0 nM) was at least 43-fold [1].

AZD1208 inhibited growth in AML cell lines and xenograft tumor models, both as monotherapy and in combination with the standard-of-care cytarabine. AZD1208 also showed activity in ex vivo colony assays of progenitor cells from AML patients, in which inhibition of colony growth was seen in the majority of samples tested. This included three samples with the Flt3-ITD mutation, demonstrating activity of AZD1208 in Flt3-ITD leukemic cells. Notably, this was in the absence of the off-target inhibition of Flt3 activity characteristic of other Pim inhibitors reported to have activity in this setting. These results indicate that Pim inhibition may be beneficial for the treatment of both Flt3 wild-type and Flt3-ITD AML [1]. Moreover, treatment with AZD1208 was shown to suppress Ser 112 phosphorylation of proapoptotic BAD, a well-documented mediator of Pim kinase prosurvival activity. In MOLM-16 cells, significant but incomplete inhibition of pBAD was seen and correlated with induction of apoptosis. However, in AZD1208-sensitive KG-1a cells, suppression of pBAD did not correspond with increased apoptosis, and suppression of pBAD was also observed in cells insensitive to growth inhibition by AZD1208.

1. Keetin, E. K.; et. al. AZD1208, a potent and selective pan-Pim kinase inhibitor, demonstrates efficacy in preclinical models of acute myeloid leukemia. Blood 2014, 123(6), 905-913.
2. Dakin, L. A.; et. al. Discovery of novel benzylidene-1,3-thiazolidine-2,4-diones as potent and selective inhibitors of the PIM-1, PIM-2, and PIM-3 protein kinases. Bioorg Med Chem Lett 2012, 22(14), 4599-4604. (synthesis)
3. Phase Global Phase1 Study to Assess the Safety and Tolerability of AZD1208 in Advanced Solid Tumors and Malignant Lymphoma. NCT01588548 (retrieved 20-05-2015)