Wednesday, September 30, 2015

Drugs in Clinical Pipeline: CEP-32496

CEP-32496 [1-(3-((6,7-dimethoxyquinazolin-4-yl)oxy)phenyl)-3-(5-(1,1,1-trifluoro-2-methylpropan-2-yl)isoxazol-3-yl)urea] as a potent, selective, orally-administered, quinazoline containing small molecule BRAF inhibitor that potently inhibits MEK phosphorylation and cell proliferation in vitro in cells harboring the BRAFV600E mutation. CEP-32496 potently binds to wild-type BRAF in vitro but is selectively cytotoxic to cell lines harboring the BRAFV600E mutation versus BRAF wild-type cells. Furthermore, CEP-32496 shows favorable pharmaceutical properties and is orally bioavailable with sustained plasma and tissue exposures in all preclinical species examined.

CEP-32496 is a potent BRAF inhibitor (Kd BRAF = 36 nM) in an in vitro binding assay for mutated BRAFV600E (Kd BRAFV600E = 14 nM) and in a mitogen-activated protein (MAP)/extracellular signal–regulated (ER) kinase (MEK) phosphorylation (pMEK) inhibition assay in human melanoma (A375) and colorectal cancer (Colo-205) cell lines (IC50 = 78 and 60 nM). In vitro, CEP-32496 has multikinase binding activity at other cancer targets of interest; however, it exhibits selective cellular cytotoxicity for BRAFV600E versus wild-type cells. CEP-32496 is orally bioavailable in multiple preclinical species (more than 95% in rats, dogs, and monkeys) and has single oral dose pharmacodynamic inhibition (10-55 mg/kg) of both pMEK and pERK in BRAFV600E colon carcinoma xenografts in nude mice [1].

In addition to both wild-type BRAF and BRAFV600E, CEP-32496 exhibits high binding affinity for related CRAF (Kd = 39 nM), as well as certain receptor tyrosine kinases of known therapeutic utility, such as Abl-1, c-Kit, Ret, PDGFR-ß, and VEGFR-2 ((Kd = 3, 2, 2 and 8 nM, respectively). However, CEP-32496 proved selective for the RAF members of the MAPK signal transduction pathway, as no significant affinity was observed for other key kinases of the MAPK pathway, including MEK-1 (Kd = 7100 nM), MEK-2 (Kd = 8300 nM), ERK-1, and ERK-2 (Kd greater than 10 uM for both resoectively). This suggests that the observed cellular activity was driven primarily through inhibition of BRAFV600E [2].

The activity of CEP-32496 is as follows:

Kd (BRAF binding assay) = 36 nM
Kd (BRAFV600E binding assay) = 14 nM
Kd (CRAF binding assay) = 39 nM; IC50 = 146 nM
Kd (ABL1 binding assay) = 2.8 nM; IC50 = 6 nM
Kd (KIT binding assay) = 2.4 nM
Kd (PDGFR-ß binding assay) = 2 nM;
Kd (VEGFR-2 binding assay) = 7.9 nM; IC50 = 43 nM
Kd (VEGFR-1 binding assay) = 14 nM; IC50 = 1 nM
Kd (RET binding assay) = 1.5 nM; IC50 = 7 nM

Common Name: CEP-32496
Synonyms: AC013773; AC 013773; AC-013773; CEP-32496; CEP32496; CEP 32496
IUPAC Name: 1-(3-((6,7-dimethoxyquinazolin-4-yl)oxy)phenyl)-3-(5-(1,1,1-trifluoro-2-methylpropan-2-yl)isoxazol-3-yl)urea
CAS Number: 1188910-76-0; 1227678-26-3 (hydrochloride)
Mechanism of Action: Kinase Inhibitor; BRAF Inhibitor; BRAFV600E Inhibitor
Indication: Various Cancers; Anti-tumor Therapy
Development Stage: Phase II
Company: Ambit Biosciences: Daiichi Sankyo/Cephalon: Teva

1. James, J.; et. al. CEP-32496: a novel orally active BRAF(V600E) inhibitor with selective cellular and in vivo antitumor activity. Mol Cancer Ther 2012, 11(4), 930-941.
2. Rowbottom, M. W.; et. al.  Identification of 1-(3-(6,7-dimethoxyquinazolin-4-yloxy)phenyl)-3-(5-(1,1,1-trifluoro-2-methylpropan-2-yl)isoxazol-3-yl)urea hydrochloride (CEP-32496), a highly potent and orally efficacious inhibitor of V-RAF murine sarcoma viral oncogene homologue B1 (BRAF)  V600E. J Med Chem 2012, 55(3), 1082-1105.