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Stargardt disease has no approved treatment. A new trial tests a shot that limits vitamin A reaching the eye

A Stargardt disease clinical trial has dosed its first participant with CITY-RBP4, a City Therapeutics shot meant to cut vitamin A delivery to the eye.

HNHealthcare News

A Stargardt disease clinical trial of CITY-RBP4 dosed its first participant, City Therapeutics said on November 10, 2026. The Cambridge, Massachusetts company is testing whether an injection that lowers the vitamin A carried to the retina can slow the inherited vision loss, which has no approved treatment.

Key points

  • City Therapeutics (Nasdaq: CTY) says the first person has received CITY-RBP4 in a first-in-human Phase 1 study.
  • The drug is an RNA interference (RNAi) medicine given under the skin, designed to switch off the liver's production of RBP4, the protein that carries vitamin A to the eye.
  • The randomized, double-masked, placebo-controlled study enrolls healthy volunteers and people with Stargardt disease, and tests single and repeat doses.
  • City expects to report the first data in mid-2027.
  • CITY-RBP4 is the company's second program to reach human testing.

What is Stargardt disease?

Stargardt disease is the most common inherited macular dystrophy in adults and children, affecting about 1 in 8,000 to 10,000 people, according to a review in the British Journal of Ophthalmology. The same review puts the share of people who carry a disease-causing ABCA4 variant at up to 1 in 20, and says symptoms most often begin in childhood, with a second peak in early adulthood. The National Eye Institute explains that a faulty ABCA4 gene lets fatty waste from the eye's use of vitamin A build up on the macula, the part of the retina that gives sharp central vision, and that care today rests on vision aids and rehabilitation. City Therapeutics' own site estimates that more than 30,000 people in the United States live with the disease.

How is CITY-RBP4 meant to slow the disease?

CITY-RBP4 is built to reduce how much vitamin A reaches the retina, so less of the toxic byproduct forms there. City says RBP4 is the main carrier of retinol, a form of vitamin A, from the liver to the eye, and that published clinical data from other groups support lowering RBP4 as a way to slow Stargardt disease. The drug is a small interfering RNA joined to GalNAc, a sugar that steers it to liver cells. In the company's preclinical work, it says, the drug produced strong, lasting falls in RBP4 and in retinol in the blood, and modeling points to the possibility of infrequent injections.

What will the Stargardt disease clinical trial measure?

The first goal of the Stargardt disease clinical trial is safety. City says the study will track safety, tolerability and how the body handles the drug, and will measure how far RBP4 and circulating retinol fall after each dose. People with Stargardt disease who take part can move into a planned open-label extension, which is set to look at longer-term safety and early signs of benefit through retinal imaging and tests of visual function. The study is registered on ClinicalTrials.gov as NCT07836452, with an estimated 48 participants and recruitment under way. For how a first-in-human study like this fits into the later phases of testing, see our guide to how clinical trials work.

"We look forward to evaluating CITY-RBP4's therapeutic potential in this Phase 1 study and reporting initial data in mid-2027."

— Andy Orth, President and Chief Executive Officer, City Therapeutics

What does the trial mean for eye care?

Our analysis: for ophthalmologists, optometrists and the families of young patients, CITY-RBP4 brings a different route into human testing for a condition where care has centered on making the most of remaining sight. Three things set it apart.

  • Treatment without an eye injection. Because the drug works in the liver, where RBP4 is made, it is given as a shot under the skin, and City's modeling points to infrequent doses. For a disease that often starts in childhood, that is a practical difference in how a long-term therapy would be given.
  • An early read on the mechanism. The Phase 1 study measures RBP4 and retinol in the blood after each dose, so the first data, due in mid-2027, are designed to show whether the drug lowers the vitamin A supply it targets well before any effect on sight can be judged. Retinal imaging and vision tests come later, in the extension study.
  • A wider use in view. City says it is also exploring the drug in geographic atrophy, the advanced dry form of age-related macular degeneration, which it says shares the same buildup of vitamin A byproducts in the retina.

Placebo-controlled early studies are also how other drugs for conditions with no approved treatment are being judged, as in the NUN-004 trial in motor neurone disease we covered earlier.

Frequently asked questions

Is CITY-RBP4 approved?

No. City Therapeutics describes CITY-RBP4 as an investigational candidate, and the Phase 1 study is its first test in people.

Where is the CITY-RBP4 trial running, and who can join?

The ClinicalTrials.gov record lists one site, Nucleus Network in Melbourne, Australia, and enrolls healthy volunteers and people with Stargardt disease type 1 aged 12 to 45.

Is there any treatment for Stargardt disease today?

There is no treatment for the disease itself, according to the National Eye Institute, but vision aids and vision rehabilitation help people use the sight they have.

Is City Therapeutics a public company?

Yes. City Therapeutics trades on Nasdaq under the symbol CTY, and filed the final prospectus for its initial public offering with the SEC on October 16, 2026.

What else is City Therapeutics developing?

City's other lead programs are CITY-FXI for thromboembolic diseases and CITY-TFR2 for anemia linked to chronic disease, and it says a third program should enter the clinic by the end of the year.

Sources

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