The purpose of this study is to evaluate the safety, tolerability and pharmacokinetics of TRx0037 after multiple doses in elderly volunteers.

Inclusion Criteria:

• Male and female 55 and over
• No clinically important abnormal physical finding
• No clinically significant lab results
• Normal ECG
• Normal BP and HR
• BMI between 19 and 32
• Weight 50 to 100 kg
• Able to communicate
• Provide written informed consent
• Non smokers
• Males to use contraception
• Females to be surgically sterile or post menopausal

Exclusion Criteria:

• Administration of any IMP other than study drug within 12 weeks before entry
• Use of any prescribed meds, St John's wort, over the counter meds as described in the protocol
• Surgical or medical condition that might interfere with IMP
• History of drug or alcohol abuse
• Clinically significant allergy requiring treatment
• Loss of greater than 400ml of blood within 12 weeks.
• Serious adverse reaction or hypersensitivity to any drug
• Presence of Hep B, Hep c or HIV-1 or HIV-2 at screening
• Presence of G6PD at screening
• History of methaemoglobinaemia
• Partner who is pregnant of lactating
• Positive Pregnancy test