The crude MRTX849 (1.00 X, basis for recrystallization) is charged to a suitable reaction vessel and dissolved in IPA (6.28 X) at 58-60°C. The process stream is polish filtered into an inert crystallization vessel and to the resulting filtrate is added n-heptane (1.37 X) at 58-60°C. The solution is cooled to 43-47°C, seeded with MRTX849 Form 2 seed (0.015 X), then the resulting slurry is slowly cooled in stages to 20-25°C. The slurry is wet-milled at 20-25°C to achieve a D90 of not more than 150 μm. The milled slurry is cooled to 3-7°C, the product is collected by filtration and washed with a mixture of IPA (0.95 X) and n-heptane (0.54 X). After sweeping with nitrogen, the collected product is dried under vacuum at less than 40°C to achieve an acceptable volatiles content by GC analysis. The finished MRTX849 is de-lumped and sieved through a 30 mesh screen. 104.1 kg of white solid with 100.3 wt% assay and 99.95% a/a purity was obtained (70% yield).