To further validate the cellular potency of our covalent SOCS2 binder and to establish inhibition of SOCS2 binding to its native substrates, we performed a SOCS2 pull-down from K562 cell lysates with biotinylated GHR_pY595 peptide immobilized onto agarose beads . Dose-dependent reduction in the amounts of SOCS2 pulled down when the cell lysates that are preincubated with increasing concentrations of MN551 demonstrates competitive binding of MN551 to the GHR substrate binding pocket of SOCS2 (Figure ). Pulldown of cellular SOCS2 was abrogated when K562 cells were pre-treated for 6 hours with MN714 prior to cell lysis, further evidencing the inhibitor cell permeability and specific target engagement (Figure ).