GSK-3 inhibitor
BI-5521
BI-5521 is a highly potent and selective non-covalent ATP-competitive inhibitor of glycogen synthase kinase (GSK-3). It is similarly active on both GSK-3 isoforms (GSK-3α and β) with single-digit nanomolar potency and has demonstrated glucose-lowering efficacy in both acute and subchronic settings in rodents. This compound has a decent PK profile in vivo and may be a useful tool for the validation of GSK-3 as a therapeutic target.
More information
Glycogen synthase kinase (GSK-3) is a constitutively active serine/threonine kinase that phosphorylates a large number of proteins in a variety of different pathways. In mammalian tissues, GSK-3 exists as two isoforms (GSK-3α and GSK-3β) that share 98% homology of their kinase domains. GSK-3β has been implicated in various diseases such as diabetes, inflammation, cancer, amyotrophic lateral sclerosis (ALS), Alzheimer’s and Parkinson’s diseases, and bipolar disorders2-5. Moreover, GSK-3 inhibitors serve as tools for regenerative medicine through increasing self-renewal and/or differentiation of stem cells5.
Crystal structure of GSK-3 complexed with BI-91BS, a close analog of BI-5521 (PDB code 6GJO).
BI-5521 inhibits GSK-3βa with an IC50 of 1.1 nM. The N-ethylated analog BI-4481, which can be used as a negative control, shows an activity of > 10,000 nM in this assay.
| Probe name / negative control | BI-5521 | BI-4481 |
| MW [Da, free base]a | 419.5 | 448.5 |
| Inhibiton of GSK-3β (IC50) [nM]b | 1.1 | >10,000 |
| Inhibiton of GSK-3α (IC50) [nM]c | 2.0 | n.d. |
| Inhibiton of GSK-3β (DC50) [nM]c | 5.0 | n.d. |
| Stimulation of Glycogen Synthesis rate in C3A cells (EC50) [nM] | 3.0 | n.d. |
| Cytotoxicity (IC50) [nM]50c | 390 | >50,000 |
a For the salt form you will get, please refer to the label on the vial and for the molecular weight of the salt, please refer to the FAQs
bInhouse assay: recombinant human GSK-3 was incubated with 33P-ATP and a 21 AA-peptide from Glycogen Synthase bearing the phosphorylation sites for GSK-3. The radiolabelled P-GS peptide was absorbed using a filter and was quantified in a counter
cin vitro cytotoxicity assay using the U937 cell line and the colorimetric EZ4U assay
| Probe name / negative control | BI-5521 | BI-4481 | ||||
| logD @ pH 11 | 2.2 | 3.4 | ||||
| Solubility @ pH 6.8 [µg/mL] | 76 | 90 | ||||
| Caco-2 permeability AB@ pH 7.4 [*10-6 cm/s] | 10 | 30 | ||||
| Caco-2 efflux ratio | 4.6 | 0.7 | ||||
| Microsomal stability (human/mouse/rat) [% QH] | 26 / 48 / 34 | 52 / >88 / 83 | ||||
| CYP 3A4 (IC50) [µM] | >50 | n.a. | ||||
| CYP 1A2 (IC50) [µM] | >50 | n.a. | ||||
| CYP 2C9 (IC50) [µM] | >50 | n.a. | ||||
| CYP 2C19 (IC50) [µM] | 12.9 | n.a. | ||||
| CYP 2D6 (IC50) [µM] | >50 | n.a. | ||||
Pharmacokinetic parameters of BI-5521 in rats
| BI-5521 | Rat |
| Clearance [mL/min/kg]a | 32 |
| Mean residence time after iv dose [h]a | 2.9 |
| tmax [h]b | 4 |
| Cmax [nM]b | 15.5 |
| Vss [l/kg]a | 5.6 |
| F [%] | 17 |
a i.v. dose: 4.2 mg/kg
b p.o. dose: 0.42 mg/kg
BI-5521 showed acute efficacy in ZDF rats
Fig. 4: Decreased plasma glucose levels during an oral glucose tolerance test in ZDF rats.
BI-5521 showed subchronic efficacy in db/db mice
Fig. 5: Decreased plasma glucose levels over 4 weeks in db/db mice.
The N-ethylated analog BI-4481 can be used as negative control (IC50 GSK-3β >10,000 nM).
BI-4481 which serves as a negative control.
BI-5521 is similarly active on both isoforms GSK-3α and GSK-3β.
Selectivity against other protein kinases:
- No selectivity against DYRK1A (99% inhibition @500 nM)
- ≥ 100fold selectivity against CDK2/CyclinA, MAP3K7_K7IP1, MAPKAPK1A, ROCK1
- > 1000fold selectivity against all other targets tested
Selectivity against non-kinase targets:
- > 500 fold selectivity against all targets of a 62 target panel (please see Suppplementary Data for detailed information)
| SELECTIVITY DATA AVILABLE | BI-5521 | BI-4481 |
SafetyScreen44™ with kind support of  | Yes | Yes |
| Invitrogen® | Yes | No |
| DiscoverX® | No | No |
| Dundee | Yes | No |
Download selectivity data:
BI-5521_selectivityData_1.xlsx
BI-4481_selectivityData.xlsx
A crystal structure of GSK-3 complexed with BI-91BS a close analog of BI-5521 is available (PDB code 6GJO).
Pharmacological inhibitors of GSK-3 described in the literature can be classified as either ATP competitive, non-ATP-competitive (allosteric) or substrate competitive inhibitors. Among these, three molecules so far reached clinical trials: the ATP competitive inhibitors AZD1080 and LY2090314 and Tideglusib with a non-ATP-competitive binding mode.2,4
BI-5521 is a potent and selective ATP-competitive small molecule inhibitor of glycogen synthase kinase 3 (GSK-3) with demonstrated in vivo activity. The N-alkylated derivative BI-4481 is also available as negative control.
US Patent 2005/0203104
Subtly Modulating Glycogen Synthase Kinase 3 β: Allosteric Inhibitor Development and Their Potential for the Treatment of Chronic Diseases
Palomo V., Perez D. I., Roca C., Anderson C., Rodríguez-Muela N., Perez C., Morales-Garcia J. A., Reyes J. A., Campillo N. E., Perez-Castillo A. M., Rubin L. L., Timchenko L., Gil C., Martinez A.
J. Med. Chem. 2017, 60, 4983−5001.
When you plan a publication, please use the following acknowledgement:
BI-5521 was kindly provided by Boehringer Ingelheim via its open innovation platform opnMe, available at https://www.opnme.com.