5-Methyl-2-(1H-pyrazol-1-yl)-d3-1H-indole is the labeled analogue of 5-Methyl-2-(1H-pyrazol-1-yl)-1H-indole (M326990). 5-Methyl-2-(1H-pyrazol-1-yl)-1H-indole is a reactant for the preparation of pyrazolic analogs of granulatimide and isogranulatimide which are selective inibitors of checkpoint 1 (Chk1) kinase.