Oral Hydroxychloroquine (HCQ) for Retinitis Pigmentosa Caused by P23H- Rhodopsin (RHO)

Inclusion Criteria: * Stated willingness to comply with all study procedures and availability for the duration of the study * Signed and dated informed consent form * Early Treatment Diabetic Retinopathy Study Best Corrected Visual Acuity (ETDRS BCVA) of 20 letters (approximately 20/400 Snellen) or better in at least one eye * Clinical diagnosis of autosomal dominant retinitis pigmentosa * Confirmed to have one copy of the P23H-RHO pathogenic variant by genetic testing at a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory * Clarity of ocular media and adequate pupillary dilation to allow for adequate clinical ocular examination and retinal imaging * Ability to perform testing required by the study as determined by the investigator * Ability to take oral medication (medication tablets must be swallowed whole) and be willing to adhere to the daily medication regimen * For females of reproductive potential: use of highly effective contraception beginning no later than 1 week after the first screening visit, and agreement to use such a method during study participation and through the end of the washout period (6 months after the end of HCQ administration) * Agreement to adhere to Lifestyle Considerations throughout study duration (take the study drug with meals, avoid taking over-the-counter antacids or kaolin-containing products 4 hours before or after taking the study drug) Exclusion Criteria: * Use of any other drugs which are known to prolong the QT interval * Concurrent use of any of the following drugs, if the drug cannot be discontinued or substituted: digoxin, antiepileptic medications, cimetidine, methotrexate, cyclosporine, praziquantel, ampicillin * Current or previous use of tamoxifen * Pregnancy or lactation * Known allergy or hypersensitivity to hydroxychloroquine or any other 4-aminoquinoline drugs (chloroquine, amodiaquine, mefloquine, quinacrine, etc.), or known history of glucose-6-phosphate dehydrogenase deficiency * Treatment with another investigational medical intervention for retinitis pigmentosa within 3 months, or any ever previous treatment with an investigational surgical intervention * Any pre-existing cardiac, renal, hepatic, or hematologic disease, any prior history of psoriasis or porphyria, or any alcoholism * Abnormal screening laboratory values including aspartate transaminase (AST) or alanine transaminase (ALT) \> 2.0 x upper limit of normal, subnormal glomerular filtration rate (\< 90 mL/min/1.73m2) or abnormal complete blood count attributable to underlying hematologic disease such as malignancy, aplastic anemia, agranulocytosis, leukopenia, or thrombocytopenia.