Pimitespib (TAS-116) is a novel, potent and selective inhibitor of heat shock protein 90 (Hsp90) subtypes alpha and beta [HSP90α/HSP90β] with anticancer activity. It inhibits HSP90α/HSP90β with Kis of 34.7 nM and 21.3 nM, respectively. It has potential antineoplastic and chemo/radiosensitizing activities. TAS-116 specifically binds to and inhibits the activity of Hsp90 alpha and beta; this results in the proteasomal degradation of oncogenic client proteins, which inhibits client protein dependent-signaling, induces apoptosis, and inhibits the proliferation of cells overexpressing HSP90alpha/beta.

Physicochemical Properties

Molecular Formula	C25H26N8O
Molecular Weight	454.526943683624
Exact Mass	454.223
CAS #	1260533-36-5
PubChem CID	67501411
Appearance	White to off-white solid powder
LogP	4.491
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	5
Rotatable Bond Count	6
Heavy Atom Count	34
Complexity	721
Defined Atom Stereocenter Count	0
InChi Key	JMNDKGSFCHWKBP-UHFFFAOYSA-N
InChi Code	InChI=1S/C25H26N8O/c1-5-26-25(34)17-6-8-19(9-7-17)33-24-22(23(30-33)16(2)3)21(10-11-27-24)32-14-20(28-15-32)18-12-29-31(4)13-18/h6-16H,5H2,1-4H3,(H,26,34)
Chemical Name	N-ethyl-4-(3-isopropyl-4-(4-(1-methyl-1H-pyrazol-4-yl)-1H-imidazol-1-yl)-1H-pyrazolo[3,4-b]pyridin-1-yl)benzamide
Synonyms	TAS-116 TAS 116 TAS116 Pimitespib
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

ln Vitro	Pimitespib binds to both new and the traditional binding pocket of the Hsp-90 that is currently in use. Due to its distinct binding mechanism, pimitespib is extremely effective against Hsp-90α/β without attaching to other Hsp-90s. The human pigment epithelial ARPE-19 cell line and NCI-H929 MM Cell growth[2] are inhibited by pimitespib (0-5 μM, 48). Family proteins, such as GRP94 in the endoplasmic reticulum or TRAP-1 in mitochondria, are also inhibited. Pimitespib (0.125-1 μM, 24 hours) significantly degraded pC-Raf and p-MEK1/2, HSP90 client proteins and important RAS/RAF/MEK dye modulators in INA6 and NCI-H929 MM cells.
ln Vivo	Pimitespib (12.0 mg/kg, lung, 14 d) does not harm the eyes and shows anticancer efficacy in malignancies. Pimitespib does not create any detectable Pimitespib-triggered boost of anti-MM activity in vivo and has a positive safety profile when administered alone or in combination with PS-341 (BTZ), as it is projected to be less dispersed than the liver. When compared to solution dye, mice treated with Pimitespib (10 mg/kg and 15 mg/kg, pass, 38 d), BTZ, or Pimitespib + BTZ demonstrated noticeably increased growth inhibition. In comparison to the solvent control, half of the dye-treated animals (Pimitespib, pass, 10 mg/kg=33 d, 15 mg/kg=37 d, BTZ=36 d, combination=56.5 d) lived noticeably longer [2]. Pimitespib's dose-dependent anticancer activity demonstrates a favorable pharmacokinetic profile; T/C (Pimitespib-treated model versus solvent-treated tumor volume of the model) was 47%, 21%, and 9%, respectively, at dosages of 3.6 mg/kg, 7.1 mg/kg, and 14.0 mg/kg. Pimitespib's bioavailability in mice following simulated absorption was nearly 100%, with a residual rate of 69.0%. In mice, the half-life of pimitespib's terminal elimination is intermediate, with t1/2=8.2 h, 2.5 h, 4.4 h, and 2.2 h for 3.6 mg/kg, face, 7.1 mg/kg, face, 14.0 mg/kg, facial, and involved (4 mg/kg, facial). Compared to other HSP90 implicates, pimitespib is removed from the trial more quickly (t1/2=3.4 hours)[1].
Cell Assay	Cell viability assay [2] Cell Types: human retinal pigment epithelial ARPE-19 cell line and NCI-H929 MM cells Tested Concentrations: 0-5 μM Incubation Duration: 48 hrs (hours) Experimental Results: Inhibits the growth of NCI-H929 MM cells with an IC50 of 0.35 μM. Western Blot Analysis[2] Cell Types: MM cell line INA6 and NCI-H929 Cell Tested Concentrations: 0.125-1 μM Incubation Duration: 24 hrs (hours) Experimental Results: Effective targeting of HSP90 client proteins, including C-Raf and MEK1/2; and inhibition of HSP27 up-regulate and overcome the 17-AAG resistance mechanism.
Animal Protocol	Animal/Disease Models: Male F344 nude mice (6 weeks old) versus established NCI-H1975 xenografts (6 weeks old) [1] Doses: 12.0 mg/kg Route of Administration: Oral; daily; two-week Experimental Results: Causes tumor shrinkage. Demonstrated anti-tumor activity in the NCI-H1975 rat xenograft model, did not cause eye damage in rats, and did not cause ocular toxicity at effective doses. Animal/Disease Models: CB17 SCID (severe combined immunodeficient) mouse (48-54 days old), mouse xenograft model [2] Doses: 10 and 15 mg/kg Route of Administration: oral; 5 days per week; continued for 28 days Experimental Results: Growth inhibition was Dramatically enhanced compared to vehicle control. The delay in tumor growth was greater in the combination treatment group compared with either treatment group alone. Animal/Disease Models: Mice, rats and dogs [1] Doses: dogs 3.0 mg/kg, rats 4.0 mg/kg, mice 3.6, 7.1 and 14.0 mg/kg Route of Administration: oral; Routine; 20-day Experimental Results: Oral absorption, without special formulation, bioavailability was nearly 100% in mice, 69.0% in rats, and 73.9% in dog
References	[1]. 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. [2]. 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. [3]. Utsugi T. New challenges and inspired answers for anticancer drug discovery and development. Jpn J Clin Oncol. 2013 Oct;43(10):945-53.
Additional Infomation	TAS-116 is under investigation in clinical trial NCT02965885 (A Study of TAS-116 in Patients With Solid Tumors). Pimitespib is a specific inhibitor of heat shock protein 90 (Hsp90) subtypes alpha and beta, with potential antineoplastic and chemo/radiosensitizing activities. Upon oral administration, pimitespib specifically binds to and inhibits the activity of Hsp90 alpha and beta; this results in the proteasomal degradation of oncogenic client proteins, which inhibits client protein dependent-signaling, induces apoptosis, and inhibits the proliferation of cells overexpressing HSP90alpha/beta. Hsp90, a family of molecular chaperone proteins that are upregulated in a variety of tumor cells, plays a key role in the conformational maturation, stability, and function of "client" proteins within the cell,; many of which are involved in signal transduction, cell cycle regulation and apoptosis, including kinases, cell-cycle regulators, transcription factors and hormone receptors. As TAS-116 selectively inhibits cytosolic HSP90alpha and beta only and does not inhibit HSP90 paralogs, such as endoplasmic reticulum GRP94 or mitochondrial TRAP1, this agent may have less off-target toxicity as compared to non-selective HSP90 inhibitors.

Solubility Data

Solubility (In Vitro)

DMSO : ~125 mg/mL (~275.01 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.08 mg/mL (4.58 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 2.08 mg/mL (4.58 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Solubility in Formulation 3: ≥ 2.08 mg/mL (4.58 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	2.2001 mL	11.0004 mL	22.0007 mL
	5 mM	0.4400 mL	2.2001 mL	4.4001 mL
	10 mM	0.2200 mL	1.1000 mL	2.2001 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.