Pathway coessentiality mapping reveals complex II is required for de novo purine biosynthesis in acute myeloid leukaemia.

Understanding how cellular pathways interact is crucial for treating complex diseases like cancer. Individual gene-gene interaction studies have provided valuable insights, but may miss pathways working together. Here we develop a multi-gene approach to pathway mapping which reveals that acute myeloid leukaemia (AML) depends on an unexpected link between complex II and purine metabolism. Through stable-isotope metabolomic tracing, we show that complex II directly supports de novo purine biosynthesis and that exogenous purines rescue AML cells from complex II inhibition. The mechanism involves a metabolic circuit where glutamine provides nitrogen to build the purine ring, producing glutamate that complex II metabolizes to sustain purine synthesis. This connection translates into a metabolic vulnerability whereby increasing intracellular glutamate levels suppresses purine production and sensitizes AML cells to complex II inhibition. In a syngeneic AML mouse model, targeting complex II leads to rapid disease regression and extends survival. In individuals with AML, higher complex II gene expression correlates with resistance to BCL-2 inhibition and worse survival. These findings establish complex II as a central regulator of de novo purine biosynthesis and a promising therapeutic target in AML.