Molecule

Description

Solid tumours

Description

MK-1775 is a potent and selective Wee1 inhibitor with IC50 of 5.2 nM.

Targets

IC₅₀

In Vitro

MK-1775 inhibits Wee1 kinase in an ATP-competitive manner. Compared to Wee1, MK-1775 displays 2- to 3-fold less potency against Yes with IC50 of 14 nM, 10-fold less potency against seven other kinases with >80% inhibition at 1 μM, and >100-fold selectivity over human Myt 1, another kinase that inhibits cyclin-dependent kinase 1 (CDC2) by phosphorylation at an alternative site (Thr14). By abrogating the DNA damage checkpoint via blockade of Wee1 activity in WiDr cells bearing mutated p53, MK-1775 treatment inhibits the basal phosphorylation of CDC2 at Tyr15 (CDC2Y15) with EC50 of 49 nM, and suppresses gemcitabine-, carboplatin- or cisplatin-induced phosphorylation of CDC2 and cell cycle arrest in a dose-dependent manner, with EC50 of 82 nM and 81 nM, 180 nM and 163 nM, as well as 159 nM and 160 nM, respectively. MK-1775 treatment alone at 30-100 nM has no significant antiproliferative effect in WiDr and H1299 cells, whereas MK-1775 at 300 nM, sufficient to inhibit Wee1 by >80%, displays moderate but significant antiproliferative effects by 34.1% in WiDr cells and 28.4% in H1299 cells. ^[1]

In Vivo

MK-1775 treatment alone at ~20 mg/kg displays minimal antitumor effects against WiDr xenografts in rats with T/C of 69% at day 3. Antitumor efficacy by MK-1775 alone in the nude rat HeLa-luc and TOV21G-shp53 xenograft models models is also moderate. ^[1]

Clinical Trials

A Phase I dose escalation study evaluating MK-1775 in both monotherapy and in combination with Gemcitabine, Cisplatin, or Carboplatin in adult subjects with advanced solid tumors is currently ongoing.

Features

First reported Wee1 inhibitor

Description

In WiDr cells, MK-1775 treatment at 30 nM or 100 nM in combination with gemcitabine remarkably enhances the antigrowth effect of gemcitabine, reducing the IC50 of gemcitabine (>100 nM) to 21.5 nM and 7.1 nM, respectively. MK-1775 (300 nM) or gemcitabine (100 nM) treatment alone induces only a minimal sub-G1 population by 2.9% and 5.2%, respectively, whereas the combination treatment drastically induces sub-G1 population in a MK-1775 dose-dependent manner by 55% at 100 nM and 59% at 300 nM. MK-1775 cotreatment dramatically sensitizes TOV21G-shp53 cells but not the TOV21G-vec cells to gemcitabine, carboplatin, or cisplatin, suggesting that MK-1775 abrogates G2 DNA damage checkpoint by Wee1 inhibition, sensitizing cells to apoptosis selectively in p53-deficient cells. Gemcitabine alone only moderately inhibits tumor growth of WiDr xenografts in rats with T/C of 35%, whereas cotreatment with MK-1775 significantly enhances the antitumor effects in a dose-dependent manner with T/C of 1% and -25% at doses of 10 mg/kg and 20 mg/kg, respectively, and reduces the dose of chemotherapy required to achieve a similar or better antitumor efficacy. MK-1775 also significantly enhances the antitumor effects of carboplatin and cisplatin in the nude rat HeLa-luc and TOV21G-shp53 xenograft models models. The cotreatment does not significantly increase toxicity, which is correlated with inhibition of CDC2Y15 phosphorylation in tumor tissue and skin hair follicles. ^[1] MK-1775 in combination with Chk1 inhibitor AR458323 synergistically inhibits proliferation in multiple cancer cell types, resulting in dramatic decreases in inhibitory phosphorylation of cyclin-dependent kinases, an increase in DNA damage, alterations in cell-cycle profile, and collapse of DNA synthesis, which is correlated with a synergistic induction of apoptosis. ^[2] A Phase II study of MK-1775 in combination with Paclitaxel and Carboplatin versus Paclitaxel and Carboplatin alone in adult patients with platinum sensitive p53 mutant ovarian cancer is currently ongoing.

In vitro kinase assays

Recombinant human Wee1 is used. Kinase reaction is conducted with 10 μM ATP, 1.0 μCi of [γ-³³P]ATP, and 2.5 μg of poly(Lys, Tyr) as a substrate in the presence of increasing concentrations of MK-1775 at 30°C for 30 minutes. Radioactivity incorporated into the substrate is trapped on MultiScreen-PH plates and is counted on a liquid scintillation counter.

Cell Lines

WiDr, NCI-H1299, TOV21G, and HeLa

Concentrations

Dissolved in DMSO, final concentrations ~10 μM

Incubation Time

24 hours

Methods

Cells are treated with or without gemcitabine for 24 hours, then with MK-1775 for an additional 24 hours. Cell viability is determined with a WST-8 kit using SpectraMax. Cellular caspase-3/7 activities are determined with a Caspase-3/7 Glo kit.

Animal Models

Immunodeficient nude rats (F344/NJcl-rnu) bearing WiDr, HeLa-luc, or TOV21G-shp53 tumors

Formulation

Prepared in a vehicle of 0.5% methylcellulose solution

Doses

~20 mg/kg/day

Administration

Orally