A Phase 1 study using in vivo MRS showed a rapid decrease in 2-HG levels within the tumour following treatment with a novel IDH1 inhibitor, consistent with metabolic response to therapy.24 Hyperpolarised 13C MRI techniques require the infusion of hyperpolarised 13C substrates, most commonly using 13C pyruvate although other probes are being developed, and can also allow characterisation of flux through metabolic pathways and signal the presence of cancer.25 The gene discussed is IDH1; the disease is neoplasm.