Here we show that MEK inhibitors are ineffective in MPD, but induce objective regression of many Nf1-deficient AMLs...Mice with AML blasts in the peripheral blood were assigned to treatment with either vehicle (n = 11) or CI-1040 (n = 12)...recipients of Mx1-Cre, Nf1flox/flox AMLs invariably died with recurrent leukaemia despite ongoing treatment…