Pimitespib

• CAT Number: I009711
• CAS Number: 1260533-36-5
• Molecular Formula: C25H26N8O
• Molecular Weight: 454.53
• Purity: ≥95%
• Synonyms: 3-ethyl-4-[4-[4-(1-methylpyrazol-4-yl)imidazol-1-yl]-3-propan-2-ylpyrazolo[3,4-b]pyridin-1-yl]benzamide
• InChI: InChI=1S/C25H26N8O/c1-5-16-10-17(24(26)34)6-7-20(16)33-25-22(23(30-33)15(2)3)21(8-9-27-25)32-13-19(28-14-32)18-11-29-31(4)12-18/h6-15H,5H2,1-4H3,(H2,26,34)
• InChIKey: NVVPMZUGELHVMH-UHFFFAOYSA-N
• SMILES: CCC1=C(C=CC(=C1)C(=O)N)N2C3=NC=CC(=C3C(=N2)C(C)C)N4C=C(N=C4)C5=CN(N=C5)C

Pimitespib (TAS-116) is an oral bioavailable, ATP-competitive, highly specific HSP90α/HSP90β inhibitor (Kis of 34.7 nM and 21.3 nM, respectively) without inhibiting other HSP90 family proteins such as GRP94[1]. Pimitespib demonstrates less ocular toxicity[2].
Pimitespib binds not only to the conventional-binding pockets as existing Hsp-90 inhibitors, but also to a novel-binding pocket. Such a unique binding mode makes Pimitespib highly specific for Hsp-90α/β without inhibiting other Hsp-90 family proteins such as GRP94 in endoplasmic reticulum or TRAP-1 in mitochondria[3].
Pimitespib (0-5 μM, 48 hours) inhibits human retinal pigment epithelial ARPE-19 cell lines and NCI-H929 MM cells growth[2].
More significant degradation of p-C-Raf and p-MEK1/2, HSP90 client proteins and key RAS/RAF/MEK pathway regulators, is triggered by Pimitespib (0.125-1 μM, 24 hours) than 17-AAG in INA6 and NCI-H929 MM cells[2].
Pimitespib (12.0 mg/kg, p.o., 14 days) shows antitumor activity without inducing eye injury in rats. Pimitespib is distributed less in retina than in plasma in rats; consequently, Pimitespib does not produce any detectable photoreceptor injury[1]. Pimitespib triggers enhanced in vivo anti-MM activities, both alone and in combination with PS-341 (BTZ), with a favorable safety profile. Mice treated with Pimitespib (10 mg/kg and 15 mg/kg, orally, 38 days), BTZ, or Pimitespib plus BTZ show significantly enhance growth inhibition versus the vehicle control group. Median overall survival of treated animals (Pimitespib, orally, 10 mg/kg=33 days, 15 mg/kg=37 days, BTZ=36 days, and the combination=56.5 days) is significantly longer than vehicle control[2].
The favorable pharmacokinetic profile of Pimitespib is reflected in its dose-dependent antitumor activity; the T/C (tumor volume of Pimitespib-treated mice vs. vehicle-treated mice) is 47%, 21%, and 9% for doses of 3.6 mg/kg, 7.1 mg/kg, and 14.0 mg/kg, respectively. Pimitespib is orally absorbed and has a bioavailability of almost 100% in mice, and 69.0% in rats. Pimitespib has moderate terminal elimination half-life (t1/2=8.2 h, 2.5 h, 4.4 h and 2.2 h for mouse (3.6 mg/kg, p.o.), mouse (7.1 mg/kg, p.o.), mouse (14.0 mg/kg, p.o.), rat (4 mg/kg, p.o.)). Pimitespib is more rapidly eliminated from retina (t1/2=3.4 hours) than the other HSP90 inhibitors (t1/2=7.1-19.1 hours)[1].

Reference

[1]. Ohkubo S, et al. TAS-116, a highly selective inhibitor of heat shock protein 90α and β, demonstrates potent antitumor activity and minimal ocular toxicity in preclinical models. Mol Cancer Ther. 2015 Jan;14(1):14-22.
 [Content Brief]

[2]. Suzuki R, et al. Anti-tumor activities of selective HSP90α/β inhibitor, TAS-116, in combination with PS-341 in multiple myeloma. Leukemia. 2015 Feb;29(2):510-4.
 [Content Brief]

[3]. Utsugi T. New challenges and inspired answers for anticancer drug discovery and development. Jpn J Clin Oncol. 2013 Oct;43(10):945-53.
 [Content Brief]