OPRM1 and cancer: For ex vivo or in vitro data, “clinical” concentrations of μOR agonists were based on human subject studies reporting maximal peak concentrations experienced by adult patients with cancer receiving opioids as part of the standard of care: morphine (≤350 nM), fentanyl (≤10.8 nM), methadone (≤3.2 μM), and oxycodone (≤320 nM), and antagonists: nalmefene, methylnaltrexone, naltrexone, and naloxone (≤1 μM).