diff --git a/src/plugins/gtopdb/parser.py b/src/plugins/gtopdb/parser.py
index 3dc43d3..13777d4 100644
--- a/src/plugins/gtopdb/parser.py
+++ b/src/plugins/gtopdb/parser.py
@@ -74,7 +74,9 @@ def preprocess_ligands(d: dict, _id: str):
         d["species"] = [species.lower() for species in species_list]
 
     if "synonyms" in d.keys():
-        d["synonyms"] = d["synonyms"].split("|")
+        # replace trademark and registered symbols with url encoding
+        d["synonyms"] = d["synonyms"].split(
+            "|").replace("™", "™").replace("®", "®")
     if "uniprot_id" in d.keys():
         d["uniprot_id"] = d["uniprot_id"].split("|")
     if "ensembl_id" in d.keys():