It is worth noting that additional classes of metabolic agents in development exist outside the scope of this Review, including small-molecule receptor blockers with consequences for metabolic processes (e.g., trigluazole; ref. 165), antibody-based therapies (e.g., anti-CD73; ref. 166), enzyme-based metabolic inhibitors (e.g., ADI-PEG-20; ref. 167), and metabolic inhibitors already developed for other diseases now under investigation in cancer (e.g., eflornithine; ref. 168). Here, NT5E is linked to cancer.