Study of Serine Supplementation to Protect Vision in MacTel

NCT07342439 | Not Yet Recruiting Phase 3 DMC FDA Drug

• 1 other identifier: 2026-001
• Study Type: interventional
• Target: 120
• Locations: 5 countries
• Sites: 12

Brief Summary

The goal of this clinical trial is to look at the efficacy and safety of giving oral serine (an amino acid) on the progression of structural and functional changes of the retina in people with MacTel type 2. The main questions it aims to answer are:

• Does serine slow the progression of MacTel?
• Is long-term serine supplementation safe in people with MacTel? Researchers will compare serine to a placebo (a look-alike substance that contains no drug) to see if serine works to slow the progression of MacTel. Participants will:
• Take serine or a placebo twice a day for 24 months
• Visit the clinic once every 6 months for eye exam, eye imaging and blood tests
• Keep a diary of their symptoms, missed doses, and changes in medications

Conditions

Macular Telangiectasia Type 2 (MacTel)

Keywords

Serine; MacTel

Outcome Measures

Primary Outcomes (1)

• EZ loss

  Mean rate of change in the total area of EZ loss (IS/OS; macular photoreceptor loss) from Baseline (BL) through Month 24 (M24), as assessed using SD-OCT in the study eye(s).

  Baseline through Month 24

Secondary Outcomes (23)

• EZ loss at different time points

  Baseline through Month 12 and 24

• Changes in Disease Severity

  Baseline through Month 24

• Retinal Sensitivity Loss

  Baseline through Month 24

• Reading Speed

  Baseline through Month 24

• Contrast Sensitivity

  Baseline through Month 24

Study Arms (2)

L-serine

EXPERIMENTAL

Participant receives oral L-serine

Drug: L-serine

Placebo

PLACEBO COMPARATOR

Participant receives placebo

Other: Placebo

Interventions

L-serine DRUG

L-serine powder administered twice daily

L-serine

Placebo OTHER

Placebo powder administered twice daily

Placebo

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Be able to read, comprehend, and agree to conditions as explained in the informed consent document and provide written informed consent;
• Be at least 18 years of age;
• Enrolled or enrolling in the Natural History Observation and Registry Study (NHOR) and confirmed with MacTel type 2 by the Reading Center in at least one eye\*;
• Participant has clear ocular media (both eyes) for sufficient image quality;
• Participant must have steady fixation in the foveal or parafoveal area;
• Female participants of childbearing potential must agree to use a highly effective method of contraception from the time consent is signed until six days after treatment discontinuation (this is due to a lack of safety data on use of L-serine in pregnant and breastfeeding women; and to allow for medication wash out post treatment discontinuation). Highly effective methods of contraception include:
• (i)Combined hormonal contraception associated with inhibition of ovulation, (ii) progesterone only hormonal contraception associated with inhibition of ovulation (iii) Intrauterine devices, (iv) surgical sterilization such as bilateral tubal occlusion or vasectomized partner or (v) true abstinence (refraining from heterosexual intercourse during the entire period associated with the study treatments, and the reliability of sexual abstinence is in line with the usual lifestyle of the subject)
• Willing and able to comply with study protocol and follow-up visits
• Agree to unconditional use of their donated samples, images and/or data;
• Be able to fast for at least 10 hours prior to blood specimen collection;
• Have a minimum area of total EZ loss of 0.16 mm2 in the study eye. The Reading Center will determine the exact size once images are uploaded.
• Participant has a BCVA of better than or equal to 20/100 Snellen equivalent (\>/= 50 letters) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts at a starting distance of 4 meters in the study eye.

You may not qualify if:

• Unable to undergo the study procedures or unavailable for follow up visits;
• Unwilling to agree to blanket consent for use of the acquired data, including human biological specimens and images;
• Participant is pregnant, breastfeeding or planning a pregnancy during the study time period;
• Participant has taken serine or glycine supplements in the last 3 months;
• Participant is currently taking or has been taking Fibrates such as fenofibrate, clofibrate, ciprofibrate, bezafibrate, gemfibrozil within the last 3 months;
• Participant has known allergy or hypersensitivity to serine or rice;
• Participant is currently taking or has been taking tamoxifen, chloroquine (or hydroxychloroquine) and/or other retinotoxic substances; for a total period of 6 months
• Participant has uncontrolled type 1 or type 2 diabetes (defined as an HbA1c level of 9% or higher at screening (with or without medication);
• Participant has uncontrolled hypo- or hyperthyroidism, defined as TSH-levels of below 0.4mU/L or above 4.0mU/L at screening with or without treatment;
• Participant is undergoing chemotherapy, radiation therapy or other treatments for active cancer;
• Participant has significant kidney disease or an estimated glomerular filtration rate \<50 ml/min/1.73m2 at screening;
• Participant has an active and/ or chronic liver disease (including viral hepatitis, autoimmune liver disease, hemochromatosis, homozygous alpha1-antitrypsin deficiency and Wilson disease, primary biliary cirrhosis, primary sclerosing cholangitis) or poor liver function as estimated by transaminases (ALT/AST) or gamma glutamyl transferase (GGT) or alkaline phosphatase or bilirubin above 2xULN (upper limit of normal) at screening;
• Participant is currently enrolled in another clinical treatment trial or participated in one within the last 30 days;
• Participant has previously received a CNTF device ("Encelto"; either eye) or has intentions of receiving a CNTF device in either eye during the duration of this study;
• Participant shows signs of retinal diseases other than MacTel (including central serous chorioretinopathy, severe non-proliferative or proliferative diabetic retinopathy, diabetic macular edema, age-related macular degeneration, preretinal membrane) that, in the judgment of the investigator, may confound the diagnosis, procedures or outcome of the study (either eye);

Sponsors & Collaborators

• The Lowy Medical Research Institute Limited: lead

Study Sites (12)

Hamilton Glaucoma Center- UCSD

La Jolla, California, 92093, United States

Location

University of Michigan, Kellogg Eye Center

Ann Arbor, Michigan, 48105, United States

Location

Retina Associates Of Cleveland, Inc.

Cleveland, Ohio, 44122, United States

Location

University of Utah Health Care, Moran Eye Center

Salt Lake City, Utah, 84132, United States

Location

Save Sight Institute

Sydney, New South Wales, 2000, Australia

Location

Cerulea- RVEEH

Melbourne, Victoria, 3002, Australia

Location

University of Bonn

Bonn, 53127, Germany

Location

University of Freiburg, Department of Ophthalmology

Freiburg im Breisgau, 79106, Germany

Location

St. Franziskus Hospital

Münster, 48145, Germany

Location

Radboud University Medical Center

Nijmegen, 6525GA, Netherlands

Location

Moorfields Eye Hospital

London, EC1V 2PD, United Kingdom

Location

Oxford Eye Hospital

Oxford, OX3 9DU, United Kingdom

Location

MeSH Terms

Interventions

Serine

Intervention Hierarchy (Ancestors)

Amino Acids, Neutral; Amino Acids; Amino Acids, Peptides, and Proteins

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: masked, two-arm, parallel-group, randomized, placebo-controlled trial

Study Record Dates

• First Submitted: January 7, 2026
• First Posted: January 15, 2026
• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): November 1, 2029
• Study Completion (Estimated): February 1, 2030
• Last Updated: January 15, 2026

Record last verified: 2026-01

Data Sharing

• IPD Sharing: Will not share

Locations

GB (2); AU (2); DE (3); US (4); NL (1)