Old drug new use--amoxapine and its metabolites as potent bacterial β-glucuronidase inhibitors for alleviating cancer drug toxicity.
OBJECTIVE
Irinotecan (CPT-11) induced diarrhea occurs frequently in patients with cancer and limits its usage. Bacteria β-glucuronidase (GUS) enzymes in intestines convert the nontoxic metabolite of CPT-11, SN-38G, to toxic SN-38, and finally lead to damage of intestinal epithelial cells and diarrhea. We previously reported amoxapine as a potent GUS inhibitor in vitro. To further understand the molecular mechanism of amoxapine and its potential for treatment of CPT-11-induced diarrhea, we studied the binding modes of amoxapine and its metabolites by docking and molecular dynamics simulation, and tested the in vivo efficacy on mice in combination with CPT-11.


METHODS
The binding of amoxapine, its metabolites, 7-hydroxyamoxapine and 8-hydroxyamoxapine, and a control drug loxapine with GUS was explored by computational protocols. The in vitro potencies of metabolites were measured by Escherichia coli GUS enzyme and cell-based assay. Low-dosage daily oral administration was designed to use along with CPT-11 to treat tumor-bearing mice.


RESULTS
Computational modeling results indicated that amoxapine and its metabolites bound in the active site of GUS and satisfied critical pharmacophore features: aromatic features near bacterial loop residue F365' and hydrogen bond toward E413. Amoxapine and its metabolites were demonstrated as potent in vitro. Administration of low dosages of amoxapine with CPT-11 in mice achieved significant suppression of diarrhea and reduced tumor growth.


CONCLUSIONS
Amoxapine has great clinical potential to be rapidly translated to human subjects for irinotecan-induced diarrhea.
Authors' Affiliations: Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College;
Ren
R
Kong
Authors' Affiliations: Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College;
Timothy
T
Liu
Authors' Affiliations: Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College;
Xiaoping
X
Zhu
Biomanufacturing Research Institute and Technology Enterprise, North Carolina Central University, Durham, North Carolina.
Syed
S
Ahmad
Biomanufacturing Research Institute and Technology Enterprise, North Carolina Central University, Durham, North Carolina.
Alfred L
AL
Williams
Methodist Cancer Center, Houston Methodist Hospital, Houston, Texas; and.
Alexandria T
AT
Phan
Authors' Affiliations: Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College; hzhao@houstonmethodist.org jscott@nccu.edu.
Hong
H
Zhao
Biomanufacturing Research Institute and Technology Enterprise, North Carolina Central University, Durham, North Carolina hzhao@houstonmethodist.org jscott@nccu.edu.
John E
JE
Scott
Biomanufacturing Research Institute and Technology Enterprise, North Carolina Central University, Durham, North Carolina.
Li-An
LA
Yeh
Authors' Affiliations: Department of Systems Medicine and Bioengineering, Houston Methodist Research Institute, Weill Cornell Medical College; Methodist Cancer Center, Houston Methodist Hospital, Houston, Texas; and.
Stephen T C
ST
Wong
D000657:Amoxapine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity; D002166:Camptothecin / Q000031:analogs & derivatives / Q000633:toxicity; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006023:Glycoproteins / Q000737:chemistry / Q000494:pharmacology*; D000077146:Irinotecan; D051379:Mice; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D009369:Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology; D020011:Protective Agents / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D006023:Glycoproteins; D020011:Protective Agents; C011473:beta-glucuronidase inhibitor; C035234:8-hydroxyamoxapine; D000077146:Irinotecan; C041917:7-hydroxyamoxapine; D000657:Amoxapine; D002166:Camptothecin