A 24-Month Trial of NPI-001 for the Preservation of Photoreceptors in Retinitis Pigmentosa Associated With Usher Syndrome

Inclusion Criteria

• Able to comprehend and willing to sign an informed consent form (OCF) and adhere to the study protocol.
• Diagnosed with RP associated with Usher syndrome.
• EZ width ≥ 500 microns, which includes the fovea in each eye at Visit 1.
• All edges of the EZ area in both eyes can be visualized at Visit 1 (Screening).
• Have at least 20 detectable points on the MAIA grid in at least one eye at the Screening and Baseline visits (same eye for both visits).
• On stable dose of medications associated with other conditions for at least one month.
• Willing to use contraception during study (for anyone of childbearing potential).

Exclusion Criteria

• Concurrent retinal pathologies that result in vision loss or inability to fixate.
• Intraocular surgery within the last two months or capsulotomy within the last month.
• Current or history of uveitis, Coat's disease, diabetic retinopathy, glaucoma, herpes simplex of the eye, or currently has a cataract that prevents visualization of the posterior pole.
• Likely to require cataract surgery within the next 12 months.
• Unstable fixation during microperimetry in either eye at either Screening or Baseline visits.
• Use of any other investigational new drug, or participation in another clinical trial within 12 weeks before the start of study treatment.
• Use of N-acetylcysteine containing products in the previous 30 days prior to the baseline visit or unwilling to refrain from such supplements for the duration of the study.
• Chronic liver or kidney disease, cystic fibrosis, severe asthma, or chronic obstructive pulmonary disease (COPD), history of thrombocytopenia not due to a reversible cause, or other blood dyscrasia.
• Suspected liver dysfunction determined by having alanine aminotransferase (ALT), aspartate aminotransferase (AST), or bilirubin values > 1.5 X the upper limit of normal (ULN) at screening.
• Platelet or hemoglobin values \< 100 at screening.
• History of known sensitivity to N-acetylcysteine or similar thiol compounds or any ingredients of NPI-001.
• History of hypersensitivity to any medication or food resulting in systemic symptoms.
• History of cancer (other than non-melanoma skin cancer) diagnosed or requiring treatment within the past 2 years.
• Pregnant women or women planning to become pregnant in the next 25 months or men with partners planning to become pregnant in the next 25 months.
• Lactating women who are breast-feeding.
• Potential participant lives in the same household as a current participant in this study.
• Subjects who are unwilling or unable to refrain from donation of blood from 30 days prior to Screening, plasma from 2 weeks prior to Screening, or platelets from 6 weeks prior to Screening until 56 days following the last study drug dose administered.
• Inability to provide blood samples, including difficulty with venous access.
• Any reason, in the opinion of the Principal Investigator, the participant should not participate.