RAHWAY, N.J., April 2, 2026
Merck (MSD) has announced the initiation of a pivotal Phase 2b/3 clinical trial (MALBEC) evaluating MK-8748 (Tiespectus), a novel bispecific antibody targeting Tie2 activation and VEGF inhibition, for the treatment of neovascular age-related macular degeneration (NVAMD). This advancement marks a significant step in addressing vision loss caused by retinal vascular instability, with the investigational therapy designed to offer a dual-mechanism approach to stabilize blood vessels and reduce fluid leakage in the retina. The trial represents the first in a broader late-stage development program aimed at transforming treatment paradigms in retinal diseases driven by neovascularization and vascular leakage.
Pivotal MALBEC Trial Targets Vision Preservation
The MALBEC Phase 2b/3 trial is a randomized, double-masked, multi-arm study evaluating the efficacy and safety of two dose levels of MK-8748 compared to aflibercept, a current standard-of-care therapy. Patients enrolled in the study will receive intravitreal injections administered monthly (Q4W) initially, followed by extended dosing intervals (Q8W), with treatment duration extending up to 96 weeks. The primary endpoint focuses on improvement in best-corrected visual acuity (BCVA), a key clinical measure of vision function.
By incorporating flexible dosing based on individual patient response, the study aims to demonstrate not only clinical efficacy but also real-world treatment adaptability, which is critical in chronic retinal conditions. This trial design reflects increasing emphasis on patient-centric outcomes and long-term disease management strategies in ophthalmology.
Novel Prodrug Design Enhances Muscle Targeting
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Preclinical studies have demonstrated that UX016 can increase sialic acid levels across multiple muscle groups and restore them toward near-normal levels, suggesting its potential to slow or modify disease progression. By targeting the underlying metabolic deficiency in sialic acid biosynthesis, UX016 represents a precision medicine approach aimed at correcting the root cause of GNE myopathy rather than merely managing symptoms.
Dual Mechanism Offers Differentiated Therapeutic Potential
MK-8748 (Tiespectus) is a next-generation bispecific antibody engineered to simultaneously activate the Tie2 signaling pathway and inhibit vascular endothelial growth factor (VEGF), addressing two key drivers of retinal vascular leakage and abnormal blood vessel growth. While existing therapies primarily target VEGF alone, this dual-action mechanism aims to enhance vascular stability and durability of treatment response, potentially reducing disease progression and treatment burden.
Early clinical and preclinical data suggest that modulating both pathways may improve retinal integrity and support sustained vision outcomes, offering a promising alternative to current monotherapy approaches. This innovation aligns with Merck’s broader strategy to develop differentiated biologics that address complex disease mechanisms through multi-target engagement.
Addressing Unmet Need in Retinal Diseases
Neovascular age-related macular degeneration remains a leading cause of irreversible vision loss among older adults, affecting approximately 1.5 million individuals in the United States alone. Despite the availability of anti-VEGF therapies, many patients continue to experience progressive vision decline due to persistent vascular leakage and incomplete disease control.
The development of MK-8748 aims to overcome these limitations by introducing a more comprehensive therapeutic approach, potentially improving both clinical outcomes and treatment durability. Additionally, Merck is advancing a broader ophthalmology pipeline targeting related conditions such as diabetic macular edema (DME) and retinal vein occlusion (RVO), reinforcing its commitment to addressing high-burden ophthalmic diseases with innovative biologics.
With the initiation of this pivotal trial, Merck strengthens its position in the ophthalmology and biologics innovation space, advancing a potentially transformative therapy that could redefine standards of care in retinal disease management. If successful, MK-8748 may offer patients a more effective and durable treatment option, addressing longstanding challenges in vision preservation and quality of life improvement for millions affected by age-related macular degeneration.
Source: Merck press release
