AG 879 or Tyrphostin AG 879 inhibits the tyrosine kinase activity of nerve growth factor(NGF)-dependent TrKA tyrosine phosphorylation in in PC-12 cells (IC₅₀ = ~40 μM), HER2-ErbB2 kinase in several breast and ovarian cancer cell lines (IC₅₀ = ~0.5 μM).  It  acts as an antiproliferative agent for diseases caused by the hyperactivity of PTKs. AG-879 has also been shown to suppress IL-6-induced tyrosine phosphorylation of STAT3 (IC₅₀ = 15 μM) in schwannoma cells.