• Shc binds to Erk and sequesters it from MAPK signal transduction. • Inhibition of PTB domain binding to EGFR prevents release of Erk. • In silico screen identified indomethacin, a known NSAID, as an inhibitor for Shc PTB. • Indomethacin indirectly inhibits MAPK signalling by depriving the pathway of Erk. • The approach to MAPK inhibition through depleting free-Erk concentration is validated.