In JAK2(V617F)-expressing SET-2 and HEL92.1.7 cells, pacritinib reduced STAT3/STAT5 phosphorylation despite increasing JAK2 Y1007/8 phosphorylation. In HEL92.1.7 cells, JAK2 Y221 phosphorylation decreased, demonstrating that phosphosite choice affects interpretation. [2]
Pacritinib inhibited FLT3 and downstream signaling in MV4-11 AML cells. A pan-JAK inhibitor did not reduce FLT3 phosphorylation at the tested concentrations, consistent with FLT3 pathway inhibition beyond JAK blockade. [3]
Recombinant kinase inhibition profile
Biochemical assay · 439-member recombinant kinase panel [1]
The assay measured multiple kinase targets and relatively little JAK1 inhibition at the screening concentration. Enzyme results do not establish cellular target dependence.
Literature-Reported Treatment Conditions
- Treatment concentration
- 100 nM screen; 1–100 nM titration for kinases inhibited >50%
- Exposure duration
- 120 min reaction at 25°C
- Method
- HotSpot radiometric filter-binding assay; 10 μM ATP
- Vehicle
- 1% DMSO
- Reported limits
- No salt/counterion or per-kinase uncertainty reported in the selected table.
Methods and source locations
Compound reported in the paper: Pacritinib (SB1518)
Compound-level research evidence; no validation of an Adooq lot or salt-equivalent conversion.
Methods: Materials and kinase assay methods; Results, Table 1
JAK2 catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
JAK2(V617F) catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
FLT3 catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
JAK3 catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
IRAK1 catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
CSF1R catalytic activity: Radiometric assay; background inactive-enzyme control; activity normalized to DMSO reactions. — Table 1; Methods: kinase assay methods
JAK1 catalytic activity: 100 nM screening assay normalized to vehicle. — Results first paragraph; Table 1
Phosphosite-dependent JAK2 signaling response
Cell-based study · SET-2 and HEL92.1.7 cells expressing endogenous JAK2(V617F) [2]
Pacritinib reduced downstream pSTAT3/pSTAT5 despite increased JAK2 Y1007/8 phosphorylation. In HEL92.1.7 cells, the Y221 site showed the opposite response to Y1007/8.
Literature-Reported Treatment Conditions
- Treatment concentration
- 0, 8, 40, 200, 1000 nM; site comparison at 1 μM
- Exposure duration
- 3 h
- Method
- Immunoblotting for phosphoproteins, total JAK2 and actin
- Reported limits
- Cell-treatment vehicle concentration and biological replicate count not specified for Figure 2a,b,e.
Methods and source locations
Compound reported in the paper: Pacritinib (SB1518)
Compound-level research evidence; no validation of an Adooq lot or salt-equivalent conversion.
Results: Modulation of JAK2 signaling; Figure 2a,b,e; Compounds and reagents; Western blot analysis
STAT3 Y705 and STAT5 Y694 phosphorylation: Figure 2a,b immunoblots; total JAK2/actin controls. No densitometric IC50 inferred. — Figure 2a,b and adjacent Results
HEL92.1.7 JAK2 phosphorylation: Figure 2e immunoblot compared with untreated lane; total JAK2 control. — Figure 2e caption and adjacent Results
FLT3 pathway inhibition in MV4-11 cells
Cell-based study · FLT3-ITD MV4-11 human AML cells [3]
Pacritinib reduced FLT3 and downstream phosphorylation. The pan-JAK inhibitor comparator did not reduce FLT3 phosphorylation through 1000 nM; sunitinib provided a FLT3-active comparator.
Literature-Reported Treatment Conditions
- Treatment concentration
- 0, 8, 40, 200, 1000 nM
- Exposure duration
- 3 h
- Method
- Immunoblotting; β-actin loading control
- Vehicle
- 0.1% DMSO
- Reported limits
- Number of independent immunoblot experiments and uncertainty of fitted cellular IC50 values not provided at this location.
Methods and source locations
Compound reported in the paper: Pacritinib (SB1518)
Compound-level research evidence; no validation of an Adooq lot or salt-equivalent conversion.
Results: Pacritinib modulates FLT3 signaling pathways; Figure 1a; Compounds and reagents; Western blot analyses
FLT3 Y591 phosphorylation: Author-reported quantified phosphorylation endpoint, not a treatment dose or cell-viability IC50. — Results: Pacritinib modulates FLT3 signaling pathways, first MV4-11 paragraph; Figure 1a
STAT5 Y694 phosphorylation: Author-reported quantified phosphorylation endpoint, not a treatment dose or cell-viability IC50. — Results: Pacritinib modulates FLT3 signaling pathways, first MV4-11 paragraph; Figure 1a
ERK1/2 phosphorylation: Author-reported quantified phosphorylation endpoint, not a treatment dose or cell-viability IC50. — Results: Pacritinib modulates FLT3 signaling pathways, first MV4-11 paragraph; Figure 1a
Akt T308 phosphorylation: Author-reported quantified phosphorylation endpoint, not a treatment dose or cell-viability IC50. — Results: Pacritinib modulates FLT3 signaling pathways, first MV4-11 paragraph; Figure 1a
FLT3 phosphorylation with pan-JAK inhibitor JAKi-1: 3 h treatment; immunoblot with β-actin loading control. — Figure 1a and adjacent Results
