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Arastoo M, Mazanetz MP, Miller S, Shiells H, Hull C, Robinson K, Storey JMD, Harrington CR, Wischik CM. Exploring the Anti-Hypoxaemia Effect of Hydromethylthionine: A Prospective Study of Phase 3 Clinical Trial Participants. Int J Mol Sci 2023; 24:13747. [PMID: 37762050 PMCID: PMC10531415 DOI: 10.3390/ijms241813747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 09/29/2023] Open
Abstract
Methylthioninium chloride (MTC) is a standard treatment for methaemoglobinaemia. A preparation of reduced MTC has been reported to increase blood oxygen saturation (SpO2) and lower respiratory rates in patients with severe COVID-19. We have developed a stable form of reduced methylthionine (hydromethylthionine-mesylate, HMTM) having a benign safety profile in two Phase 3 trials in Alzheimer's disease. The aim of this prospective study was to determine the effects of oral HMTM on SpO2 and methaemoglobin (metHb) levels in a cohort of patients with mild hypoxaemia not due to COVID-19. Eighteen participants randomised to a single dose of 4, 75, 100 or 125 mg doses of HMTM had SpO2 levels below 94% at baseline. Patients were routinely monitored by pulse oximetry after 4 h, and after 2 and 6 weeks of twice daily dosing. Significant ~3% increases in SpO2 occurred within 4 h and were sustained over 2 and 6 weeks with no dose differences. There were small dose-dependent increases (0.060-0.162%) in metHb levels over 2 to 6 weeks. Minimum-energy computational chemistry revealed that HMT can bind within 2.10 Å of heme iron by donating a pair of electrons from the central nitrogen of HMT to d orbitals of heme iron, but with lower affinity than oxygen. In conclusion, HMTM can increase SpO2 without reducing metHb by acting as a strong displaceable field ligand for heme iron. We hypothesise that this facilitates a transition from the low oxygen affinity T-state of heme to the higher affinity R-state. HMTM has potential as an adjunctive treatment for hypoxaemia.
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Affiliation(s)
- Mohammad Arastoo
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZP, UK; (M.A.); (C.R.H.)
- Scottish Biologics Facility, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZP, UK
| | - Michael P. Mazanetz
- NovaData Solutions Ltd., 15 Monreith Rd, Newlands, Glasgow G43 2NX, UK;
- Department of Chemistry, University of Aberdeen, Aberdeen AB24 3UE, UK;
| | - Sonya Miller
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
| | - Helen Shiells
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
| | - Claire Hull
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
| | | | - John M. D. Storey
- Department of Chemistry, University of Aberdeen, Aberdeen AB24 3UE, UK;
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
| | - Charles R. Harrington
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZP, UK; (M.A.); (C.R.H.)
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
| | - Claude M. Wischik
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZP, UK; (M.A.); (C.R.H.)
- TauRx Therapeutics Ltd., 395 King Street, Aberdeen AB24 3FX, UK; (S.M.); (H.S.); (C.H.)
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