Characterisation of the Janus Kinase inhibitory activity of novel kinase inhibitor AT9283
Year: 2008
Session type: Poster / e-Poster / Silent Theatre session
Astex Therapeutics, Cambridge, UK
Abstract
The Janus kinase family (JAKs) consists of four intracellular tyrosine kinases, JAK1, JAK2, JAK3 and TYK2. The JAKs are activated through specific membrane bound receptors. Upon activation, JAKs phosphorylate multiple sites on the receptor cytoplasmic domain and the Signal transducers and activators of transcription (STATs) that are recruited to these sites. Upon phosphorylation the STATs homodimerise, translocate to the nucleus and directly activate transcription. AT9283 is a multi-targeted kinase inhibitor which is currently in phase I/IIa clinical trials for haematological malignancies and a phase I trial in solid tumours. Here we describe the characterisation of its inhibitory activity against members of the JAK family.
We have established assays to characterise the cellular JAK inhibitory activity of compounds and investigate their effects on specific signalling pathways. These assays were used to investigate the cellular activity of AT9283 against JAK2 and JAK3. A panel of cell lines with differing JAK dependencies were used to profile compounds including human erythroleukaemia (HEL) cells with the constitutively active JAK2V617F mutation, engineered Ba/F3 TEL-JAK2 and TEL-JAK3 cells, and cytokine stimulated TF-1 cells. AT9283 inhibited the proliferation of JAK-dependent cells lines with IC50s in the range of 17-110nM. It also inhibited phosphorylation of direct JAK2 and JAK3 substrates STAT5 and STAT6 and other relevant markers in cells.
We have shown that the activity of AT9283 against the isolated enzymes translates into potent cellular JAK2 and JAK3 activity in a number of cellular systems.
The Janus kinase family (JAKs) consists of four intracellular tyrosine kinases, JAK1, JAK2, JAK3 and TYK2. The JAKs are activated through specific membrane bound receptors. Upon activation, JAKs phosphorylate multiple sites on the receptor cytoplasmic domain and the Signal transducers and activators of transcription (STATs) that are recruited to these sites. Upon phosphorylation the STATs homodimerise, translocate to the nucleus and directly activate transcription. AT9283 is a multi-targeted kinase inhibitor which is currently in phase I/IIa clinical trials for haematological malignancies and a phase I trial in solid tumours. Here we describe the characterisation of its inhibitory activity against members of the JAK family.
We have established assays to characterise the cellular JAK inhibitory activity of compounds and investigate their effects on specific signalling pathways. These assays were used to investigate the cellular activity of AT9283 against JAK2 and JAK3. A panel of cell lines with differing JAK dependencies were used to profile compounds including human erythroleukaemia (HEL) cells with the constitutively active JAK2V617F mutation, engineered Ba/F3 TEL-JAK2 and TEL-JAK3 cells, and cytokine stimulated TF-1 cells. AT9283 inhibited the proliferation of JAK-dependent cells lines with IC50s in the range of 17-110nM. It also inhibited phosphorylation of direct JAK2 and JAK3 substrates STAT5 and STAT6 and other relevant markers in cells.
We have shown that the activity of AT9283 against the isolated enzymes translates into potent cellular JAK2 and JAK3 activity in a number of cellular systems.
