OPN1MW and cancer: Various cannabinoids have already been used as either (a) natural or synthetic THC alone or together with TMZ in patients with recurrent GBs in clinical trials (CT-NCT01812603, CT-NCT01812616); (b) CBD alone (CT-NCT02255292) or together with TMZ [20]; or (c) an equimolar THC:CBD combination drug (e.g., Sativex or Nabiximol), which is approved in over 30 countries for the management of (cancer-associated) pain.