Dual-Target Approach Challenges the Ceiling of Intravitreal Injections as KSI-501 Begins Phase 3 Trial in Diabetic Macular Edema

Anti-VEGF drugs have transformed the treatment landscape for diabetic macular edema, but repeated intravitreal injections, residual fluid, and incomplete visual recovery remain realities that many patients must face. Kodiak Sciences has now advanced its dual-target candidate KSI-501 into the global Phase 3 ALTO trial, seeking to answer a more ambitious question: beyond blocking vascular leakage, can simultaneous inhibition of inflammatory signaling deliver more complete and durable disease control?

ALTO is a randomized, double-blind, active-controlled, multicenter study. Its ClinicalTrials.gov registration lists it as NCT07734844, sponsored by Kodiak, with plans to enroll approximately 910 participants with vision loss due to center-involving diabetic macular edema. The trial will compare intravitreal KSI-501 (tabirafusp tedromer) 5 mg with aflibercept 2 mg. It includes both treatment-naive and previously treated patients, with treatment and follow-up lasting approximately 96 weeks.

Participants will be assigned to three groups in a 5:3:5 ratio. Two groups will receive six monthly loading doses of KSI-501, followed either by dosing every eight weeks with additional treatment based on monthly assessments, or by individualized intervals adjusted from four to 24 weeks according to each patient’s response. The control group will receive aflibercept every eight weeks after five monthly loading doses. This design will compare not only efficacy but also the potential to reduce treatment burden within the same Phase 3 evaluation.

The primary endpoint is the change from baseline in mean best-corrected visual acuity at weeks 48 and 52. The study aims to demonstrate that KSI-501 is superior to aflibercept, rather than merely noninferior. The key secondary endpoint is the proportion of patients achieving an improvement of at least two steps on the Diabetic Retinopathy Severity Scale at week 48. Other analyses cover retinal anatomy, treatment frequency, durability, and safety.

KSI-501 combines a VEGF-trapping receptor structure with an anti-IL-6 antibody and links them to Kodiak’s antibody biopolymer conjugate platform. VEGF is an important driver of retinal vascular leakage, while IL-6 is associated with inflammation, endothelial dysfunction, and disruption of the blood–retinal barrier. Dual inhibition therefore has a biological rationale, but the barrier-restoration and disease-modifying potential described by the company currently derives mainly from preclinical models and cannot be regarded as proven in humans.

Enrollment of the first patients marks the program’s entry into a pivotal validation stage, but it does not yet represent an efficacy breakthrough. The announcement provided no new comparative clinical efficacy or safety data. Whether individualized intervals of up to 24 weeks will be suitable for enough patients, and whether adding IL-6 inhibition can deliver a clinically meaningful visual advantage, cannot be determined until the complete Phase 3 results are available. The comparator already has established efficacy and safety data, meaning KSI-501 must demonstrate incremental benefit and durability while also showing that the risks of long-term intraocular use are acceptable.