Stable immediate release tablet and capsule formulations of 1-((2S,5R)-5-((7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-2-methylpiperidin-1-yl)prop-2-en-1-one

A stable immediate release formulation comprising about 15-67% 1-((2S,5R)-5-((7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-2-methylpiperidin-1-yl)prop-2-en-1-one para-toluenesulfonate salt, about 12-40% microcrystalline cellulose, about 12-40% lactose monohydrate, about 2-4% crospovidone;

• and about 3-10% glyceryl dibehenate, wherein the formulation has 0.7% w/w or less of a dimer of 1-((2S,5R)-5-((7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-2-methylpiperidin-1-yl)prop-2-en-1-one at 25-30° C./10-65% relative humidity for at least one year, wherein the stable immediate release formulation is free of, or comprises no more than 1.00% of magnesium stearate.