Discovery of novel Jak2-Stat pathway inhibitors with extended residence time on target

Area of Science:

• Oncology
• Molecular Biology
• Medicinal Chemistry

Background:

• The Janus kinase 2 (Jak2)/Signal transducer and activator of transcription 5 (Stat5) pathway is implicated in oncogenesis.
• Activating mutations in Jak2 (e.g., V617F) and modulation of Stat3 by Jak2 inhibitors have increased interest in targeting this pathway for cancer therapy.

Purpose of the Study:

• To discover and characterize novel inhibitors targeting the Jak2/Stat5 signaling axis.
• To evaluate the in vitro and in vivo efficacy of newly synthesized N-(1H-pyrazol-3-yl)pyrimidin-2-amino derivatives.

Main Methods:

• Chemical synthesis of N-(1H-pyrazol-3-yl)pyrimidin-2-amino derivatives.
• Enzymatic assays to assess Jak2 inhibition and residence time.
• Kinase selectivity profiling.
• In vivo studies to evaluate downstream Stat5 phosphorylation inhibition.

Main Results:

• Novel N-(1H-pyrazol-3-yl)pyrimidin-2-amino derivatives were synthesized and evaluated.
• Lead compounds 6 and 9 demonstrated prolonged residence time on Jak2 at the enzymatic level.
• Despite in vitro potency and long residence time, compounds 6 and 9 did not achieve sustained inhibition of Stat5 phosphorylation in vivo.

Conclusions:

• N-(1H-pyrazol-3-yl)pyrimidin-2-amino derivatives represent a novel class of Jak2 inhibitors with promising in vitro characteristics, including long residence time.
• The in vivo efficacy of these inhibitors in suppressing downstream Stat5 signaling was not recapitulated, highlighting a potential disconnect between in vitro residence time and in vivo pharmacodynamics.