Currently, there are several ongoing Phase I–III clinical trials investigating the efficacy of novel therapeutic agents for TRD, which include Ketamine, Psychedelics, anti-inflammatory mediators, as well as antagonists and/or agonists for DA, NMDA, metabotropic glutamate receptor (mGlu5), GABA, and opioid receptors [242]. The gene discussed is GRM5; the disease is treatment resistant depression.