PLX-4720

Abstract

PLX-4720 is an orally-available, ATP-competitive, highly selective, azaindole-based inhibitor of B-Raf (V600E) with IC50 value of 13 nM. PLX-4720 has additional activity towards mutant forms of c-Raf-1 (Y340D, Y341D) at an IC50 of 6.7 nM, with modest single micromolar activity versus kinases such as FRK, CSK, SRC, FGFR, KDR< HGK, and Aurora A.  PLX-4720 has shown preclinical activity in melanoma and thyroid cancer models.
PLX-4720 preferentiallly inhibits ERK phosphorylation in tumor cell lines bearing the V600E allele. In melanoma models it induces cell cycle arrest and apoptosis exclusively in B-Raf (V600E)-positive cells.
In an orthotopic 8505c human thyroid cancer mice model, PLX-4720 caused significant reduction in tumor growth (>90%) and dramatically decreased lung metastases.

Biological activity

PLX4720 is a potent and selective inhibitor of B-RafV600E with IC50 of 13 nM in a cell-free assay, equally potent to c-Raf-1(Y340D and Y341D mutations), 10-fold selectivity for B-RafV600E than wild-type B-Raf.

In vitro

PLX-4720 displays >10 times selectivity against wild type B-Raf, and >100 times selectivity over other kinases such as Frk, Src, Fak, FGFR, and Aurora A with IC50 of 1.3-3.4 μM. PLX-4720 significantly inhibits the ERK phosphorylation in cell lines bearing B-RafV600E with IC50 of 14-46 nM, but not the cells with wild-type B-Raf. PLX-4720 significantly inhibits the growth of tumor cell lines bearing the B-RafV600E oncogene, such as COLO205, A375, WM2664, and COLO829 with GI50 of 0.31 μM, 0.50 μM, 1.5 μM, and 1.7 μM, respectively. In addition, PLX-4720 treatment at 1 μM induces cell cycle arrest and apoptosis exclusively in the B-RafV600E-positive 1205Lu cells, but not in the B-Raf wild-type C8161 cells. PLX-4720 treatment (10 μM) significantly induces >14-fold expression of BIM in the PTEN+ cells, compared with the PTEN-cell lines (4-fold), giving an explanation of the resistance of PTEN-cells to PLX-4720-induced apoptosis.

In vivo

Oral administration of PLX-4720 at 20 mg/kg/day induces significant tumor growth delays and regressions in B-RafV600E-dependent COLO205 tumor xenografts, without obvious adverse effects in mice even at dose of 1 g/kg. PLX-4720 at 100 mg/kg twice daily almost completely eliminates the 1205Lu xenografts bearing B-RafV600E, while has no activity against C8161 xenografts bearing wild-type B-Raf. The anti-tumor effects of PLX-4720 correlate with the blockade of MAPK pathway in those cells harboring the V600E mutation. PLX-4720 treatment at 30 mg/kg/day significant inhibits the tumor growth of 8505c xenografts by >90%, and dramatically decreases distant lung metastases.

References

http://www.cellagentech.com/PLX-4720/
[1] Tsai J, et al. Discovery of a selective inhibitor of oncogenic B-Raf kinase with potent antimelanoma activity. Proceedings of the National Academy of Sciences of the United States of America, 2008; 105: 3041–3046.

Description

The Raf kinases activate cellular pathways that lead to cell proliferation and can contribute to certain types of cancer. Mutations in the kinase B-Raf are involved in a wide range of cancers. In particular, the mutation B-Raf^V600E occurs in melanomas and thyroid cancer but is poorly targeted by many inhibitors of wild type B-Raf. PLX4720 is an orally-available, highly selective inhibitor of B-Raf^V600E (IC₅₀ = 13 nM). It is less effective against wild type B-Raf (IC₅₀ = 160 nM) as well as several other kinases. PLX4720 induces cell cycle arrest and apoptosis in cells and xenografts expressing the mutant of B-Raf.

Uses

A potent and selective inhibitor of B-RafV600E and c-Raf-1Y340D/Y341D with IC50s of 13 nM and 6.7 nM, respectively.

Uses

Labelled PLX4720. It is a selective inhibitor of mutant B-RAF and its analog, PLX4032, is currently undergoing clinical trials in melanoma.

Definition

ChEBI: A pyrrolopyridine that is vemurafenib in which the p-chlorophenyl group has been replaced by chlorine. It is a potent and selective inhibitor of the Raf kinase B-Raf(V600E).

target

B-RafV600E

storage

+4°C

Advantages

PLX4720, a 7-azaindole derivative that inhibits B-RafV600E with an IC50 of 13 nM, defines a class of kinase inhibitor with marked selectivity in both biochemical and cellular assays. PLX4720 preferentially inhibits the active B-RafV600E kinase compared with a broad spectrum of other kinases, and potent cytotoxic effects are also exclusive to cells bearing the V600E allele. Consistent with the high degree of selectivity, ERK phosphorylation is potently inhibited by PLX4720 in B-RafV600E-bearing tumor cell lines but not in cells lacking oncogenic B-Raf. In melanoma models, PLX4720 induces cell cycle arrest and apoptosis exclusively in B-RafV600E-positive cells. In B-RafV600E-dependent tumor xenograft models, orally dosed PLX4720 causes significant tumor growth delays, including tumor regressions, without evidence of toxicity[1].