Friday, September 4, 2015

Drugs in Clinical Pipeline: Saracatinib

Saracatinib [N-(5-Chloro-1,3-benzodioxol-4-yl)-7-[2-(4-methyl-1-piperazinyl)ethoxy]-5-[(tetrahydro-2H-pyran-4-yl)oxy]-4-quinazolinamine] is an orally available, reversible, ATP-competitive c-Src kinase inhibitor (IC50 = 2.7 nM) which is in clinical development for the treatment of a wide range of tumor types. It inhibited other Src tyrosine kinase family members investigated (c-Yes, Fyn, Lyn, Blk, Fgr, and Lck), with high selectivity observed against a panel of other protein kinases involved in signal transduction. It should no activity against Csk (IC50 greater than 1000 nM), the intracellular negative regulator of Src activation. Saracatinib showed moderate activity aginst EGFR (IC50 = 66 nM), and was virtually inactive against KDR (IC50 ~ 21 uM).

The only other notable activities observed were versus Abl (in common with other ATP-competitive Src inhibitors, IC50 ((v-Abl) = 30 nM) and versus activating mutant forms of the EGFR (L858R and L861Q, IC50 = 5 and 4 nM, respectively) [1,2].

AstraZeneca believes that Saracatinib is likely to have a therapeutic benefit as an anti-invasive agent, with potential for activity in early and advanced solid tumors, leukemia, and metastatic bone disease. Moreover, investigators recently characterized a molecular pathway by which β-amyloid damages neurons, and showed that the protein termed Fyn kinase is crucial. Saracatinib has good activity against Fyn kinase. Chronic Saracatinib administration is well tolerated in humans, and the investigators propose to test its potential as a novel Alzheimer's disease modifying therapy. 

The activity of Saracatinib is as follows:

IC50 (c-Src enzyme assay) = 2.7 nM
IC50 (v-Abl enzyme assay) = 30 nM

IC50 (c-Yes enzyme assay) = 4 nM
IC50 (Fyn enzyme assay) = 10 nM
IC50 (Lyn enzyme assay) = 5 nM
IC50 (Blk enzyme assay) = 11 nM
IC50 (Fgr enzyme assay) = 10 nM
IC50 (Lck enzyme assay) = less than 4 nM

Common Name: Saracatinib
Synonyms: AZD 0530; AZD-0530; AZD0530
IUPAC Name: N-(5-Chloro-1,3-benzodioxol-4-yl)-7-[2-(4-methyl-1-piperazinyl)ethoxy]-5-[(tetrahydro-2H-pyran-4-yl)oxy]-4-quinazolinamine
CAS Number: 379231-04-6
Mechanism of Action: Kinase Inhibitor; c-Src Inhibitor
Indication: Various Cancers; Anti-Tumor Therapy; Treatment of Alzheimer's Disease
Development Stage: Phase III
Company: AstraZeneca

c-Src kinase is a nonreceptor tyrosine kinase that acts as a signal transduction inhibitor that is a critical component of multiple signaling pathways that control cell growth, proliferation, invasion, and apoptosis. While c-Src kinase is highly regulated and active only at low levels in most normal cells, studies have shown that c-Src kinase is upregulated in many human tumor types. Recently emerging data support the hypothesis that the predominant consequence of increased c-Src activity in tumor cells is to reduce cell adhesion, facilitate motility, and thereby promote an invasive phenotype. Consequently, there is considerable interest in the inhibition of c-Src kinase as a treatment for cancer and in particular as an antiinvasion strategy. Studies have shown that c-Src kinases have a function in imatinib-resistant CML and ALL and that inhibitors of c-Src and Bcr-Abl kinases have activity against both imatinib-sensitive and imatinibresistant cell lines. c-Src kinase activity is also implicated in metastatic bone disease, a characteristic of late-stage progression of many solid tumor types, for example, breast and prostate, and of leukemias. In animal models, inhibition of c-Src kinase has been shown to limit invasion of bone metastases and destructive bone resorption [2].

Inhibition of c-Src activity in cells was evaluated in mouse NIH 3T3 cells transfected with constitutively active human c-Src. Saracatinib displayed IC50 values of 76 nM in the proliferation assay (c-Src-transfected NIH3T3 cells) and 140 nM in the migration assays (A549 cells) [2]. Animals treated with Saracatinib orally once daily at doses of 6 (mg/kg)/d for 18 days show greater than 95% inhibition of tumor volume and tumor weight at the end of the experiment.

Saracatinib potently inhibited the in vitro proliferation of Src3T3 mouse fibroblasts and demonstrated variable antiproliferative activity in a range of human cancer cell lines containing endogenous Src. Sub micromolar growth inhibition of five of the human cancer cell lines tested with Saracatinib (tumor types: colon, prostate, lung, and leukemia) was observed with IC50 values of 0.2-0.7 uM. In the microdroplet migration assay, Saracatinib reduced the migration of human lung cancer A549 cells in a concentration-dependent manner (IC50 = 0.14 uM). Saracatinib at concentrations of 0.01-0.5 uM demonstrated a clear dose-dependent antimigratory effect compared with untreated controls in monolayer scratch assays of human breast cancer MDA-MB-231 cells. Moreover, in rat and mouse tumor model, complete tumor growth inhibition was observed (100% inhibition at 25 mg/kg/day in mice and 10 mg/kg/day in rats) [1]. 

1. Green, T. P.; et. al. Preclinical anticancer activity of the potent, oral Src inhibitor AZD0530. Mol Oncol 2009, 3(3), 248-261.
2. Hennequin, L. F.; et. al. N-(5-chloro-1,3-benzodioxol-4-yl)-7-[2-(4-methylpiperazin-1-yl)ethoxy]-5- (tetrahydro-2H-pyran-4-yloxy)quinazolin-4-amine, a novel, highly selective, orally available, dual-specific c-Src/Abl kinase inhibitor. J Med Chem 2006, 49(22), 6465-6488.
3. Safety and Tolerability of AZD0530 (Saracatinib) in Alzheimer's Disease. NCT01864655 (retrieved 01-09-2015)
4. Study to Evaluate the Safety and Effects AZD0530 on Prostate and Breast Cancer Subjects With Metastatic Bone Disease. NCT00558272 (retrieved 01-09-2015)
5. AZD0530 to Treat Recurrent Stage IIIB/IV NSCLC Previously Treated With Combination Chemotherapy. NCT00638937 (retrieved 01-09-2015)
6. Saracatinib in Treating Patients With Stage III or Stage IV Melanoma That Cannot Be Removed By Surgery. NCT00669019 (retrieved 01-09-2015)