PD184352 (CI-1040)S1020

CI-1040 treatment produces a reduction of pMAPK levels in multiple tumor cells including Colon 26, BX-PC3 pancreatic, A431 cervical, HT-29 colon, ZR-25-1 breast and SKOV-3 ovarian carcinomas. CI-1040 treatment doesn't inhibit the phosphorylation of Jun kinase, p38 kinase or Akt, indicating CI-1040 specifically targets MEK. Inhibition of MAPK activation by CI-1040 prevents cell cycle progression and induces a G1 block. ^[1] The IC50 for inhibition of MEK1 by CI-1040 is 0.3 μM, 15-fold higher than the concentration required to inhibit the EGF-induced activation of ERK2 in Swiss 3T3 cells. These results indicate CI-1040 exerts its effects on cells by suppressing the activation of MKK1, and not by blocking its activity. 2 nM PD184352 inhibits the activation of MKK1 in Swiss 3T3 cells by 50%, while over 100-fold concentration of CI-1040 inhibits MEK1 in vitro. PD184352 also inhibits the Raf-catalysed phosphorylation of MEK1 without any effect on the Raf-catalysed phosphorylation of myelin basic protein. ^[2] CI-1040 inhibits 86% of papillary thyroid carcinoma (PTC) cell growth with the RET/PTC1 rearrangement at 10μM compared with cells treated with DMSO only. CI-1040 shows potent inhibition to PTC cells (BRAF mutation) with GI50 of 52 nM, but low activity to RET/PTC1 rearrangement type with GI50 of 1.1 μM. ^[3] A recent research indicates CI-1040 increases the apoptotic effect of BMS-214662 in a CML blast crisis cell line, K562, and in primary chronic phase CD34+ CML cells. ^[4]