KX2-391 (Tirbanibulin)

Catalog No.S2700 Synonyms: KX 01

For research use only.

KX2-391, the first clinical Src inhibitor (peptidomimetic class) that targets the peptide substrate site of Src, with GI50 of 9-60 nM in cancer cell lines. Phase 2.

KX2-391 (Tirbanibulin) Chemical Structure

CAS No. 897016-82-9

Selleck's KX2-391 (Tirbanibulin) has been cited by 34 publications

Purity & Quality Control

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Biological Activity

Description KX2-391, the first clinical Src inhibitor (peptidomimetic class) that targets the peptide substrate site of Src, with GI50 of 9-60 nM in cancer cell lines. Phase 2.
Src (HuH7) [1]
(Cell-free assay)
Src (PLC/PRF/5) [1]
(Cell-free assay)
Src (Hep 3B) [1]
(Cell-free assay)
Src (Hep G2) [1]
(Cell-free assay)
9 nM(GI50) 13 nM(GI50) 26 nM(GI50) 60 nM(GI50)
In vitro

KX2-391 is a Src inhibitor that is directed to the Src substrate pocket. KX2-391 shows steep dose-response curves against Huh7 (GI 50 = 9 nM), PLC/PRF/5 (GI 50 = 13 nM), Hep3B (GI 50 = 26 nM), and HepG2 (GI 50 = 60 nM), four hepatic cell cancer (HCC) cell lines. [1] KX2-391 is found to inhibit certain leukemia cells that are resistant to current commercially available drugs, such as those derived from chronic leukemia cells with the T3151 mutation. KX2-391 is evaluated in engineered Src driven cell growth assays inNIH3T3/c-Src527F and SYF/c-Src527F cells and exhibits GI50 with 23 nM and 39 nM, respectively. [2]

Cell Data
Cell Lines Assay Type Concentration Incubation Time Formulation Activity Description PMID
mouse NIH3T3 cells NIrKT2RHfW6ldHnvckBie3OjeR?= MUWzJIRigXN? NV3hcIRoUW6qaXLpeIlwdiCxZjDjc45{fGm2dYTpeoVtgSCjY4TpeoUhcHWvYX6gZ{1UWkN3MkfGJI12fGGwdD3pcoR2[2WmIHfyc5d1cCCrbnjpZol1cW:wIHnuJI1wfXOnIF7JTFNVOyClZXzsd{Bi\nSncjCzJIRigXNiYomgUXRVKGG|c3H5 MkTKNlE5PTJyMkO=
Methods Test Index PMID
Western blot α-SMA / Collagen 1 / Fibronectin / p-Src / Src 29137389
In vivo In pre-clinical animal models of cancer, orally administered KX2-391 is shown to inhibit primary tumor growth and to suppress metastasis. [2]

Protocol (from reference)

Cell Research:


  • Cell lines: Huh7, PLC/PRF/5, Hep3B, and HepG2 cell lines
  • Concentrations: 6,564 to 0.012 nM
  • Incubation Time: 3 days
  • Method:

    Liver cell lines including Huh7, PLC/PRF/5, Hep3B, and HepG2 (NutriCyte, Buffalo, NY) are routinely cultured and maintained in basal medium containing 2% fetal bovine serum (FBS) at 37 °C and 5% CO2. Cells are seeded at 4.0 × 103/190 μL and 8.0 × 103/190 μL per well of 96-well plate in basal medium containing 1.5% FBS. These are cultured overnight at 37 °C and 5% CO2 prior to the addition of KX2-391, at concentrations ranging from 6,564 to 0.012 nM in triplicates. Treated cells are incubated for 3 days. Ten microliters of 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide (MTT) solution (5 mg/mL) is then added to each well on day 3 and cells incubated for 4 hours. The formazan product is dissolved with 10% SDS in dilute HCl. Optical density at 570 nm is measured by using BioTek Synergy HT multiplatform microplate reader. For comparison of activity and potency, parallel experiments are performed using KX2-391. Growth inhibition curves, 50% inhibition concentration (GI50), and 80% inhibition concentration (GI80) are determined using GraphPad Prism 5 statistical software. Data are normalized to represent percentage of maximum response as well as reported in optical density at wavelength of 570 nm (OD570) signal format.</

Solubility (25°C)

In vitro

In vivo

Add solvents to the product individually and in order
(Data is from Selleck tests instead of citations):
4% DMSO+30% PEG 300+ddH2O
For best results, use promptly after mixing.


Chemical Information

Molecular Weight 431.53


CAS No. 897016-82-9
Storage 3 years -20°C powder
2 years -80°C in solvent

In vivo Formulation Calculator (Clear solution)

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Method for preparing in vivo formulation: Take μL DMSO master liquid, next add μL Corn oil, mix and clarify.

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Clinical Trial Information

NCT Number Recruitment Interventions Conditions Sponsor/Collaborators Start Date Phases
NCT03575780 Completed Drug: KX2-391 Ointment 1% Actinic Keratoses Athenex Inc.|TKL Research Inc. September 7 2018 Phase 1
NCT02838628 Completed Drug: 50 mg of KX2-391 Ointment 1% Actinic Keratosis Almirall S.A.|Athenex Inc. April 11 2016 Phase 2
NCT02337205 Completed Drug: KX2-391 Ointment Actinic Keratosis Athenex Inc. December 2014 Phase 1
NCT01397799 Completed Drug: KX2-391 Acute Myelogenous Leukemia Kinex Pharmaceuticals Inc.|Athenex Inc. December 2013 Phase 1
NCT01074138 Completed Drug: KX2-391 Bone-Metastatic Castration-Resistant Prostate Cancer Kinex Pharmaceuticals Inc.|Athenex Inc. February 2010 Phase 2

(data from https://clinicaltrials.gov, updated on 2022-08-01)

Tech Support

Answers to questions you may have can be found in the inhibitor handling instructions. Topics include how to prepare stock solutions, how to store inhibitors, and issues that need special attention for cell-based assays and animal experiments.

Handling Instructions

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Frequently Asked Questions

Question 1:
How to formulate KX2-391 for animal trials?

KX2-391 can be dissolved in 4% DMSO/corn oil at 5 mg/ml as a homogeneous suspension for oral administration and dissolved in 4% DMSO/30% PEG 300/ddH2O at 5 mg/ml as a clear solution.

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