RSK Inhibitor | BIX 02565
Highlights
BIX 02565 has been characterized as a highly potent inhibitor of the N-terminal kinase domain of the three RSK isoforms expressed in cardiac cells. It showed the best combination of potency, selectivity, and solubility among a panel of molecules and is well suited for both in vitro and in vivo experiments. Generated against human RSK, BIX 02565 shows cross-reactivity to mouse and rat RSK. The overall balanced profile makes it an attractive compound to study the role of RSK kinase.
Background information
Target Information
The p90 ribosomal s6 kinases (RSKs) are a group of serine/threonine kinases that are constituents of the AGC subfamily in the human kinome. The RSK isoforms are activated by growth factors, cytokines, peptide hormones and neurotransmitters that stimulate the Ras-ERK pathway. RSK regulates numerous biological processes through its phosphorylation of cellular substrates. One important cardiovascular target of RSK is the Na+/H+ exchanger isoform 1 (NHE1). RSK has also been reported to regulate PKC and ROS mediated phosphorylation of cardiac troponin I and to induce pro-renin converting enzyme in ischemia and diabetic cardiomyopathy. RSK is implied in regulation of cardiac cells and there are scientific data that support the notion of a potential role in heart failure secondary to myocardial infarction.
Structure of the Human Ribosomal protein S6 kinase (PDB Code: 2WKN).
In vitro activity
BIX 02565 inhibits RSK kinases in nanomolar range and inhibition of adrenergic receptor subtypes (α1A, α2A, α1B and β2) and the Imidazoline I2 (IC50 values between 0.052 and 1.820 µM).
| PROBE NAME / NEGATIVE CONTROL | BIX 02565 |
| MW [Da, free base]a | 458.6 |
| RSK1 (IC50) [nM] | 3 |
| RSK2 (IC50) [nM] | 1 |
| RSK3 (IC50) [nM] | 1 |
| HLR-CREB (IC50) [nM]b | 20 |
| pNHE1 (DC50) [nM]b | 70 |
| Adrenergic α1A [µM] | 0.91 |
| Adrenergic α2A [µM] | 1.42 |
| Adrenergic α1B [µM] | 0.052 |
| Adrenergic β2 [µM] | 1.82 |
| Imidazoline I2 [µM] | 0.097 |
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
b Assay conditions1-3
In vitro DMPK and CMC parameters
| PROBE NAME | BIX 02565 |
| logP @ pH 11 | 3.39 |
| Solubility @ pH 4.5 / 7.4 [µg/mL] | >45 / 26 |
| Caco-2 permeability AB @ pH 7.4 [*10-6 cm/s] | 4.4 |
| Caco-2 efflux ratio | 16.6 |
| Microsomal stability (human/rat) [% QH] | <30 / 10 |
| Hepatocyte stability (human/rat) [% QH] | 58 / 45 |
| Plasma Protein Binding (human/rat) [%] | 94 / 90 |
| PAMPA [10-6 cm/sec] | 43.5 |
| hERG [inh. % @ 10 µM] | 54.8 |
| CYP 3A4 (IC50) [µM] | >50 |
| CYP 2C8 (IC50) [µM] | >50 |
| CYP 2C9 (IC50) [µM] | >50 |
| CYP 2C19 (IC50) [µM] | >50 |
| CYP 2D6 (IC50) [µM] | >50 |
In vivo DMPK parameters
| BIX 02565 | RAT |
| Clearance [% QH]a | 75 |
| Mean residence time after i.v. dose [h]a | 4.9 |
| Cmax [nM]b | 6550 |
| F [%]b | 100 |
| Vss [L/kg]a | 15 |
a i.v. dose: 1 mg/kg
b p.o. dose: 100 mg/kg
In vivo pharmacology
In telemetry-instrumented rats, BIX 02565 elicits concentration-dependent decreases in MAP after each dose. BIX 02565 produces concentration-dependent relaxation ex vivo in the phenylephrine-constricted rat aortic ring. Subsequently, BIX 02565 is infused in the anesthetized rat in a low-dose and high-dose series of continuous infusions to test the effect of compound on hemodynamics in vivo. Nevertheless, the off-target pharmacology of BIX 02565 made it potentially difficult to distinguish efficacy as a result of off-target vasodilatation from inhibition of RSK23.
Selectivity
BIX 02565 was profiled against the Invitrogen kinase panel (229 kinases), and dose-response was obtained for each kinase with inhibition > 50% at 3 µM. Kinase inhibition > 80% at 3 µM is predictive of an IC50 of 1 µM or below. Kinases outside the RSK family (IC50 [nM]): LRRK2 (16), PRKD1 (35), CLK2 (112), PRKD2 (139), RET (161), PRKD3 (219), FGFR2 (320), CLK1 (512), FLT3 (714), PDGFRa (956).
| SELECTIVITY DATA AVILABLE | BIX 02565 |
SafetyScreen44™ with kind support of  | Yes |
| Invitrogen® | Yes |
| DiscoverX® | Yes |
| Dundee | No |
Download selectivity data:
BIX-02565_selectivityData.xlsx
Co-crystal structure of the BI probe compound and the target protein
A RSK2 homology model was created based on the publicly available crystal structure of RSK1 (PDB: 2z7r)2.
Reference molecule(s)
BI-D1870, RMM-46 – Calbiochem
Summary
BIX 02565 is a highly potent nanomolar inhibitor of the ribosomal S6 kinase (RSK) isoforms. It has been extensively characterized on a standardized kinase panel, proving to have a relatively high selectivity. Further to this, it demonstrates inhibition of adrenergic receptor subtypes and the imidazoline I2 receptor. In an animal model, BIX 02565 showed dose-dependent decrease in mean arterial pressure accompanied by bradycardia. The off-target pharmacology of BIX 02565 makes de it potentially difficult to distinguish efficacy as a result of off-target vasodilatation from inhibition of RSK2.
Supplementary data
2D structure formats available
References
Indole RSK inhibitors. Part 1: Discovery and initial SAR
Boyer S. J., Burke J., Guo X., Kirrane T. M., Snow R. J., Zhang Y., Sarko C., Soleymanzadeh L., Swinamer A., Westbrook J., Dicapua F., Padyana A., Cogan D., Gao A., Xiong Z., Madwed J. B., Kashem M., Kugler S., O'Neill M. M.
Bioorg Med Chem Lett 2012, 22, 733–737.
Mitigation of Off-Target Adrenergic Binding and Effects on Cardiovascular Function in the Discovery of Novel Ribosomal S6 Kinase 2 Inhibitors
Fryer R. M., Muthukumarana A., Chen R. R., Smith J. D., Mazurek S. N., Harrington K. E., Dinallo R. M., Burke J., DiCapua F. M., Guo X., Kirrane T. M., Snow R. J., Zhang Y., Soleymanzadeh F., Madwed J. B., Kashem M. A., Kugler S. Z., O'Neill M. M., Harrison P. C., Reinhart G. A., Boyer S. J.
J Pharmacol Exp Ther 2012, 340, 492–500.
How to cite opnMe?
When you plan a publication, please use the following acknowledgement:
BIX 02565 was kindly provided by Boehringer Ingelheim via its open innovation platform opnMe, available at https://opnme.com.
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