Merck's remigromig meets primary endpoint in diabetic macular edema trial amid safety concerns

Merck announced on September 24, 2026, that its experimental eye drug remigromig met its primary endpoint in the Phase 2b/3 BRUNELLO trial for diabetic macular edema, matching Roche's Lucentis in visual acuity improvement. However, the drug showed higher rates of proliferative diabetic retinopathy, bleeding inside the eye, and treatment discontinuations. Analysts expressed mixed reactions over these safety signals as Merck seeks to build its post-Keytruda pipeline following its 2024 acquisition of EyeBio.

BRUNELLO trial design and efficacy results

• ▪The Phase 2b/3 BRUNELLO trial enrolled 984 patients who received either one of two doses of remigromig or ranibizumab (Lucentis) administered via eye injection.
• ▪Both the 0.5 mg and 0.8 mg doses of remigromig demonstrated non-inferiority to ranibizumab (Lucentis) in best-corrected visual acuity change from baseline to week 52.
• ▪Merck announced on September 24, 2026, that its investigational tri-specific antibody remigromig met its primary endpoint in the Phase 2b/3 BRUNELLO trial for adults with diabetic macular edema.

Safety findings and Merck's response

• ▪The Phase 2b/3 BRUNELLO trial showed higher rates of proliferative diabetic retinopathy, vitreous hemorrhage (bleeding inside the eye), and treatment discontinuations due to adverse events in patients receiving remigromig compared to ranibizumab.
• ▪Merck stated that remigromig was generally well tolerated in the BRUNELLO trial and plans to present full first-year results at a medical meeting on October 10, 2026.
• ▪Merck is conducting additional analyses to better understand the safety findings from the BRUNELLO trial and plans to discuss the results with regulatory authorities.

Analyst assessments of the trial results

• ▪BMO Capital Markets analysts stated on September 24, 2026, that the BRUNELLO trial update was insufficient to establish a differentiated profile for remigromig, noting that side effects and lack of detailed data limited enthusiasm.
• ▪Evercore ISI analyst Umer Raffat expressed less concern over the safety disclosures, stating that vitreous hemorrhages have occurred in other eye drug trials and that the disclosure reflects Merck's conservative reporting style.
• ▪RBC Capital Markets analyst Trung Huynh characterized the BRUNELLO trial results as mixed, noting encouraging efficacy but expressing concern over the new safety disclosures.
• ▪Guggenheim analysts noted that while the side effects were concerning, the BRUNELLO trial marked the first time a novel mechanism of action matched Lucentis in a clinical trial.

Additional remigromig studies

• ▪Remigromig previously delivered positive results in a Phase 1b/2a study in patients with diabetic macular edema and wet age-related macular degeneration.
• ▪Merck is continuing to evaluate remigromig in the ongoing Phase 2b/3 BAROLO study and a Phase 2 proof-of-concept study.

Merck's acquisition of EyeBio

• ▪The acquisition of EyeBio in 2024 marked Merck's return to the ophthalmology market after nearly a decade, following a prior partnership with NGM Biopharmaceuticals that ended after disappointing study results in 2022.
• ▪Merck acquired remigromig (formerly known as Restoret) through its 2024 acquisition of privately held EyeBio for $1.3 billion in upfront cash, with potential milestone payments of up to $1.7 billion.

Merck's growth diversification strategy

• ▪Merck is developing remigromig as part of its strategy to diversify its growth profile and reach $70 billion in annual sales next decade ahead of Keytruda's loss of market exclusivity.
• ▪Merck is advancing other pipeline assets to diversify its growth, including the Moderna-partnered mRNA cancer vaccine intismeran autogene, the Kelun-Biotech-partnered antibody-drug conjugate sacituzumab tirumotecan, and the antibody tulisokibart.

Debatable claims

• ▪The BRUNELLO trial validates the Wnt-pathway as a viable target for retinal diseases
• ▪The safety risks of Merck's remigromig outweigh its clinical benefits
• ▪Merck's remigromig lacks a sufficiently differentiated profile to compete in the ophthalmology market