A Safety Study of Retinal Gene Therapy for Choroideremia With Administration of BIIB111

An Open-Label Safety Study of Retinal Gene Therapy for Choroideremia With Bilateral, Sequential Administration of Adeno-Associated Viral Vector (AAV2) Encoding Rab Escort Protein 1 (REP1)

The objective of the study is to evaluate the safety of bilateral, sequential sub-retinal administration of a single dose of BIIB111 in adult male participants with Choroideremia (CHM).

This study was previously posted by NightstaRx Ltd. In October 2020, sponsorship of the trial was transferred to Biogen.

Key Inclusion Criteria:

1. Are willing and able to give informed consent for participation in the study to have both eyes treated.

2. Have documentation of a genetically-confirmed diagnosis of CHM.

3. Have active disease clinically visible within the macular region of both eyes.

4. Have a BCVA of ≥34 ETDRS letters (20/200 or better Snellen acuity) in both eyes, or in the untreated eye, if the other eye was previously treated with BIIB111*

   *If previously treated with BIIB111 in an antecedent study, participants may be eligible for participation following Sponsor approval.

5. For participants who received treatment with BIIB111 in an antecedent study, have biological samples available to complete an adequate immunology profile.

Key Exclusion Criteria:

1. Have a history of amblyopia or inflammatory disorder in either eye.

2. Are unwilling to use barrier contraception methods or abstain from sexual intercourse for a period of 3 months following treatment with BIIB111 in either eye.

3. Have had previous intraocular surgery performed within 3 months of the Screening Visit in either eye.

4. Have any other significant ocular or non-ocular disease/disorder which, in the opinion of the investigator, may either put the participants at risk because of participation in the study, or may influence the results of the study or the participant's ability to participate in the study. This includes but is not limited to a potential participants:

   • with a contraindication to oral corticosteroid (e.g., prednisolone/prednisone)
   • with clinically significant cataract in either eye
   • who, in the clinical opinion of the Investigator, is not an appropriate candidate for sub-retinal surgery.

5. Have participated in another research study involving an investigational product in the past 12 weeks or received a gene/cell-based therapy at any time previously, except if treated within an antecedent study with BIIB111.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply