Adavosertib (MK-1775)

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 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]

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 is also moderate. ^[1]

• 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

• Method

  Cells are treated 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

• Dosages

  ~20 mg/kg/day

• Administration

  Orally