Effect of potent urease inhibitor, fluorofamide, on Helicobacter sp. in vivo and in vitro

Pope, A. J., Toseland, N., Rushant, B., Richardson, S., McVey, M. and Hills, J. (1998) Effect of potent urease inhibitor, fluorofamide, on Helicobacter sp. in vivo and in vitro. Digestive Diseases and Sciences, 43(1), pp. 109-119. (doi: 10.1023/A:1018884322973)

Abstract

The therapeutic potential of urease inhibition of <i>Helicobacter pylori</i> has been studied by examining the effect of the potent urease inhibitor, fluorofamide (N-(diaminophosphinyl)-4-fluorobenzenamide), on urease activity and bacterial survival in vivo and in vitro. In culture, acid protection in <i>H. pylori</i> was shown to be due to changes in the pH of the medium brought about by the release of ammonia. Both the acid protection and the ammonia release were completely blocked by fluorofamide at low doses (ED₅₀= approximately 100 nM). However, fluorofamide was unstable under acidic conditions (T_1/2= 5.7 min at pH 2). Despite this, fluorofamide was the best available compound to test <i>in vivo</i>. In ferrets naturally infected with <i>H. mustelae</i>, a single dose (50 mg/kg, <i>per os</i>) of fluorofamide completely inhibited bacterial urease. In repeat dosing studies, fluorofamide (50 mg/kg <i>per os</i>, three times a day) was compared with the <i>Helicobacter</i> triple therapy regime (amoxycillin, metronidazole, and bismuthsubcitrate). Fluorofamide failed to eradicate the <i>H. mustelae</i> infection, compared to 80% eradication with triple therapy. However, histological samples showed a profound reduction in bacterial numbers following fluorofamide treatment. A combination of fluorofamide and amoxycillin was dosed to ferrets(seven days of treatment with 50 mg/kg fluorofamide plus 10 mg/kg amoxycillin <i>per os</i> twice a day); however, this failed to eradicate the infection, despite there being a reduction in bacterial numbers in 3/5 ferrets after 21 days after dosing stopped. It was concluded that urease inhibitors (either alone or in combination with antibiotics) are unlikely to have therapeutic potential for <i>Helicobacter pylori</i> infections. This is probably because, <i>in vivo</i>, some bacteria (perhaps dormant forms) are not entirely dependent upon urease for survival. However, given the acid instability of fluorofamide, the possibility that more stable urease inhibitors might have therapeutic potential, cannot be excluded.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McVey, Dr Mary
• Authors: Pope, A. J., Toseland, N., Rushant, B., Richardson, S., McVey, M., and Hills, J.
• Subjects: Q Science > Q Science (General); Q Science > QR Microbiology
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: Digestive Diseases and Sciences
• Publisher: Springer Verlag
• ISSN: 0163-2116
• ISSN (Online): 1573-2568