Kynurenine is a metabolite of the amino acid L-tryptophan used in the production of niacin. Kynurenine is synthesized by the enzyme tryptophan dioxygenase, which is made primarily but not exclusively in the liver, and indoleamine 2,3-dioxygenase, which is made in many tissues in response to immune activation. Kynurenine and its further breakdown products carry out diverse biological functions, including dilating blood vessels during inflammation and regulating the immune response. Evidence suggests that increased kynurenine production may precipitate depressive symptoms associated with interferon treatment for hepatitis C. Cognitive deficits in schizophrenia are associated with imbalances in the enzymes that break down kynurenine. Kynurenine production is increased in Alzheimer's disease and cardiovascular disease where its metabolites are associated with cognitive deficits and depressive symptoms.

Hafnium oxide is a radio enhancer; its nanoparticles (NBTXR3) were designed for high dose energy deposition within cancer cells when exposed to ionizing radiation. When activated by radiotherapy (RT), NBTXR3 allows for a higher energy deposit than RT alone, yielding an increased tumoral cell death. Nanocrystals of hafnium oxide are under investigation in phase II/III in patients with locally advanced soft tissue sarcoma (STS) of the extremity and trunk wall. In addition, NBTXR3, nanoparticles are being studied in phase I/II in patients with head and neck cancer; liver cancer; prostate cancer and rectal cancer.