NIH Clinical Center Search the Studies: Study Number, Study Title

Protocol Details

Oral Metformin for Treatment of ABCA4 Retinopathy

This study is currently recruiting participants.

Summary | Eligibility | Citations | Contacts




Sponsoring Institute

National Eye Institute (NEI)

Recruitment Detail

Type: Participants currently recruited/enrolled
Gender: Male & Female
Min Age: 12 Years
Max Age: 100 Years

Referral Letter Required


Population Exclusion(s)



Stargardt Disease;
Retinal Dystrophy;
Retinal Degeneration

Recruitment Keyword(s)



ABCA4 Retinopathy;
Stargardt Disease;
Retinal Dystrophy;
Retinal Degeneration

Investigational Drug(s)

Metformin Hydrochloride

Investigational Device(s)



Drug: Metformin hydrochloride

Supporting Site

National Eye Institute


ABCA4 retinopathy is a genetic disease in which the ABCA4 protein is absent or faulty. It can cause waste material to collect in the eye and may cause cells to die. The cell death can lead to vision loss. Researchers want to see if an oral drug called metformin can help.


To see if metformin is safe and possibly helps to slow the rate of ABCA4 retinopathy.


People age 12 and older who have ABCA4 retinopathy and have problems with their vision.


Participants will be screened under a separate protocol.

Participants will have a medical and family history. They will complete a questionnaire about their vision and daily activities. They will have a physical exam. They may have blood drawn through a needle in the arm.

Participants will have an eye exam. Their pupils may be dilated with eye drops. Their retina may be photographed.

Participants will have a visual field test. They will sit in front of a large dome and press a button when they see a light within the dome.

Participants will have an electroretinogram. It examines the function of the retina. They will sit in the dark for 30 minutes. Then their eyes will be numbed with eye drops. They will wear contact lenses that can sense signals from the retinas. They will watch flashing lights.

Participants will have optical coherence tomography. This non-invasive procedure makes pictures of the retina.

Participants will have fundus autofluorescence. A bright blue light will be shone into their eye.

Participants will take metformin by mouth for 24 months.

Participants will have study visits every 6 months. Participation will last for at least 36 months.

--Back to Top--



To be eligible, the following inclusion criteria must be met, where applicable.

1. Participant must be at least 12 years of age.

2. Participant (or legal guardian) must understand and sign the protocol's informed consent document.

3. Participant must have at least one definite pathogenic or likely pathogenic mutation in ABCA4 and a typical clinical presentation of Stargardt disease and phenotypic presentation of ABCA4 retinopathy in both eyes.

4. Participant must have at least two years of natural history data from at least four data points (a). The separation between any two consecutive data points must be at least six months (b). The most recent data point must be at least 4.5 months and no more than 16 months prior to the baseline visit (c).

a. Potential participants with three natural history data points may be enrolled to obtain their fourth natural history data point on protocol.

b. The separation between any two consecutive data points may fall short of 6 months by no more than 45 days; however, the total separation among the data points must allow for at least two years of natural history data.

c. Potential participants with four or more natural history data points completed off protocol, all of which having occurred more than 16 months prior to the baseline visit, may be enrolled to complete an additional natural history data point on protocol within the required timeframe from the baseline visit.

5. Participant must agree to adhere to Lifestyle Considerations throughout study duration.

6. Any female participant of childbearing potential must have a negative urine pregnancy test at screening and be willing to undergo urine pregnancy tests throughout the study.

7. Any female participant of childbearing potential must:

-Have had a surgical sterilizationa OR

-Completely abstain from intercourse OR

-Practice at least one form of contraceptionb during the study and at least one week after IP discontinuation OR

-Have a partner who had a surgical sterilization OR

-Have a partner who practices one form of contraception for the duration of the study and at least one week after the female participant discontinues IP.

Any male participants must:

-Have had a surgical sterilization (a) OR

-Completely abstain from intercourse OR

-Practice at least one form of contraception (b) throughout the study and at least for 3 months after IP discontinuation OR

-Have a partner who had a surgical sterilization OR

-Have a partner who practices one form of contraception for the duration of the study and at least 3 months after the male participant discontinues IP.

(a) Acceptable forms of surgical sterilization include: vasectomy, hysterectomy, or tubal ligation.

(b) Acceptable methods of contraception include: hormonal contraception (i.e., birth control pills, injected hormones, dermal

patch or vaginal ring), intrauterine device, or barrier methods (diaphragm, condom) with spermicide.

Metformin, like insulin, is considered a class B drug by the FDA (animal reproductive studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women) and is frequently prescribed for gestational diabetes. One meta-analysis showed outcomes with metformin were slightly superior to insulin. Nonetheless, out of an abundance of caution, we will ask female and male participants in this trial to use these forms of contraception.


An individual who meets any of the following criteria will be excluded from participation in this study:

1. Participant is actively receiving study IP in another investigational study.

2. Participant has a condition that would preclude participation in the study (e.g., unstable medical status including blood pressure and glycemic control) by interfering with the participant's ability to engage in the required protocol evaluation and testing and/or comply with study visits.

3. Any female participant of childbearing potential that is pregnant, breast-feeding or planning to become pregnant during the study.

4. Participant has definitive pathogenic or likely pathogenic mutations in RDS/peripherin (PRPH2), PROM1, and/or ELOVL4.

5. Participant has a history of chronic renal impairment as measured in the acute care panel estimated glomerular filtration rate (eGFR<45 ml/min/1.73 m2) or severe hepatic, pulmonary, or cardiovascular disease (hypoxic state).

6. Participant is taking any medication that could adversely interact with metformin (e.g., cimetidine, furosemide, nifedipine) and cannot switch to an alternative medication.

7. Participant is currently taking metformin or participant has taken metformin during the period of natural history data collection that will be used for this study for a cumulative total of more than one month (> 31 days).

8. Participant has a known hypersensitivity to metformin.

9. Participant has a history of chronic lactic acidosis, including diabetic ketoacidosis, with or without coma.

10. Participant has type 1 diabetes mellitus.

11. Scarring due to choroidal neovascularization (CNV) is present in either eye.


In order to participate in the study, the participant must have at least one qualifying eye that meets all of the inclusion and none of the exclusion criteria listed below.

Qualifying Eye Inclusion Criteria:

1. A growth rate of square-root AreaEZloss > 0.025 mm/year based on calculation from natural history data.

Qualifying Eye Exclusion Criteria:

1. Retinal degeneration has advanced beyond a point where reliable measurement of the integrity of the IS-OS on OCT is possible.

--Back to Top--


Not Provided

--Back to Top--


Principal Investigator

Referral Contact

For more information:

Brian P. Brooks, M.D.
National Eye Institute (NEI)
(301) 496-3577

Cathy Kangale-Whitney, R.N.
National Eye Institute (NEI)
National Institutes of Health
Building 10
Room 10D45
10 Center Drive
Bethesda, Maryland 20892
(301) 402-4174

Office of Patient Recruitment
National Institutes of Health Clinical Center (CC)
Building 61, 10 Cloister Court
Bethesda, Maryland 20892
Toll Free: 1-800-411-1222
Local Phone: 301-451-4383
TTY: TTY Users Dial 7-1-1

Clinical Trials Number:


--Back to Top--