Tuesday, October 6, 2015

Drugs in Clinical Pipeline: AZD1775 | WEE1 Inhibitor | Cell Cycle Inhibitor

AZD1775 [2-allyl-1-(6-(2-hydroxypropan-2-yl)pyridin-2-yl)-6-(4-(4-methylpiperazin-1-yl)phenylamino)-1,2-dihydropyrazolo[3,4-d]pyrimidin-3-one] is potent and selective small-molecule inhibitor of Wee1 kinase, with an IC50 value of 5.2 nM in in vitro kinase assays. An increasing linear relationship was observed between the IC50 value of AZD1775 and ATP concentration in an enzyme assay, suggesting that AZD1775 inhibited Wee1 kinase in an ATP-competitive manner. Wee1 is a tyrosine kinase that phosphorylates and inactivates CDC2 and is involved in G2 checkpoint signaling. As p53 is a key regulator in the G1 checkpoint, p53-deficient tumors rely only on the G2 checkpoint after DNA damage. Hence, such tumors are selectively sensitized to DNA-damaging agents by Wee1 inhibition.

AZD1775 : 2D and 3D Structure
AZD1775 is highly selective against other serine/threonine or tyrosine kinases. Among 223 kinases in the Upstate Kinase Profiler panel, only 8 kinases were inhibited by more than 80% with 1 ┬ÁM AZD1775. The IC50 values determined for these eight kinases indicate that AZD1775 is 10-fold less potent against seven of these kinases relative to Wee1 and 2- to 3-fold less potent against Yes (IC50 = 14 nM). AZD1775 shows greater than 100-fold selectivity over human Myt 1, another kinase that suppresses CDC2 by a phosphorylation at an alternative site (Thr14).
In Sept 2013, AstraZeneca and Merck, announced a worldwide licensing agreement for Merck’s oral small molecule inhibitor of WEE1 kinase (MK-1775). The WEE1 inhibitor MK-1775 is designed to cause certain tumour cells to divide without undergoing the normal DNA repair processes, ultimately leading to cell death. Preclinical evidence suggests that the combination of MK-1775 and DNA damage-inducing chemotherapy agents can enhance anti-tumor properties, in comparison to chemotherapy alone. AstraZeneca will be responsible for all future clinical development, manufacturing and marketing.
The activity of AZD1775 is as follows:
IC50 (WEE1 enzyme assay) = 5.2 nM
IC50 (YES enzyme assay) = 14 nM
Common Name: AZD1775
Synonyms: MK-1775; MK1775; MK 1775; AZD-1775; AZD1775; AZD 1775
IUPAC Name: 2-allyl-1-(6-(2-hydroxypropan-2-yl)pyridin-2-yl)-6-((4-(4-methylpiperazin-1-yl)phenyl)amino)-1H-pyrazolo[3,4-d]pyrimidin-3(2H)-one
CAS Number: 955365-80-7
Mechanism of Action: Kinase Inhibitor; WEE1 Kinase Inhibitor
Indication: Various Cancers; Inhibition of Cell Cycle
Development Stage: Phase I/II
Company: Merck/AstraZeneca

1H-NMR (Estimated) for AZD1775

What is WEE1 Kinase?

Wee1 is a tyrosine kinase that selectively phosphorylates the Tyr15 residue of cyclin-dependent kinase 1 (also known as CDC2) and inactivates its activity. As CDC2Y15 phosphorylation is involved in G2-M checkpoint regulation by DNA damage, Wee1 is an interesting target for development of a G2 checkpoint abrogator. Consistent with this hypothesis, Wee1 silencing with siRNA or inhibition of Wee1 by small molecular inhibitor compounds was reported to sensitize cells toward DNA damage. When cellular DNA is damaged, cells can arrest the cell cycle temporally to allow for the damaged DNA to be repaired. This cell cycle checkpoint could protect normal cells or tissues from damage and promote their survival, but it may reduce the effectiveness of chemotherapy on tumor cells. Thus, if one can selectively reduce the checkpoint activity in tumor cells, treatment with DNA-damaging agents could be much more effective. Many of the conventional anticancer treatments, including ionizing radiation, antimetabolites, alkylating agents, DNA topoisomerase inhibitors, and platinum compounds, damage DNA in cells. Although these DNA-damaging agents are among the most effective anticancer agents, their clinical use has many limitations. Their therapeutic potentials are not sufficient because of poor patient responses and because of side effects due to their lack of tumor selectivity.

p53 is a key regulator of the G1 checkpoint and is one of the most frequently mutated genes in cancer. Therefore, a majority of human cancers lack G1 checkpoint but retain the S- and G2-phase checkpoints. As a result, p53-deficient cells are predicted to be more dependent on S or G2 checkpoint. Hence, p53-deficient tumors treated with G2 checkpoint abrogator may be particularly susceptible to DNA damage. Nontumor tissue will retain G1 checkpoint activity due to its normal p53 pathway function. Thus, checkpoint escape induced by G2-checkpoint abrogator may selectively sensitize p53-deficient cells to DNA-damaging anticancer agents while sparing normal tissues from toxicity [1].

Preclinical Activity

AZD1775 possesses preferential killing effect in p53-deficient tumors by using p53 matched-pair cell lines. The selective antitumor effect of MK-1775 on p53-deficient cells was shown in combination with DNA-damaging agents with different modes of action, gemcitabine and platinum compounds. The p53 context specificity of Wee1 inhibition was carefully investigated by another modality, Wee1 siRNA, in the additional comparative study with H1299 (p53-deficient) cancer cells and human normal renal epithelial cells (p53 wild-type). These studies also confirmed that Wee1 silencing is effective only in cells with dysfunctional p53 [1].

1. Hirai, H.; et. al. Small-molecule inhibition of Wee1 kinase by MK-1775 selectively sensitizes p53-deficient tumor cells to DNA-damaging agents. Mol Cancer Ther 20098(11), 2992-3000.
2. Takeshi, S.; et. al. Dihydropyrazolopyrimidinone derivatives US20140303178A1