Kirby is originally from St. Louis, Missouri, USA. In 2007, he graduated with a BS (Hons) in Biochemistry from the University of Missouri. In 2013, he completed his PhD in the same institute under the guidance of Jay Thelen. Here his PhD research focused on applying state-of-the-art proteomics and mass spectrometry techniques to unravel the phosphorylation networks of Arabidopsis seed development.

After completing his PhD, Kirby joined David Komander's lab at the MRC Laboratory of Molecular Biology in Cambridge, UK, to study the complexity of the ubiquitin system. Here he developed innovative proteomic approaches to identify and understand the architecture of polyubiquitin chains, which provided critical insights into how these complex signals function in cells. In 2018, he joined Brenda Schulman's Department at the Max Planck Institute of Biochemistry in Munich, Germany, to pursue his interests in structural biology of multiprotein complexes of the Ub/Ubl system. Kirby will start his research group in the MRC Protein Phosphorylation and Ubiquitylation Unit at the beginning of 2022.