Abstract: Verteporfin (VP) is a benzoporphyrin derivative and a second-generation photosensitizer that has revolutionized the treatment of various ocular diseases. Clinically approved as a liposomal formulation (Visudyne), it is primarily utilized in photodynamic therapy (PDT) for the management of age-related macular degeneration (AMD), polypoidal choroidal vasculopathy (PCV), and central serous chorioretinopathy (CSC). Upon activation by a specific wavelength of light, verteporfin generates reactive oxygen species (ROS) that selectively damage abnormal neovascular endothelial cells, leading to microvascular occlusion. Beyond its photoactivated properties, recent research has uncovered verteporfin's ability to function without light activation as a potent inhibitor of the Yes-associated protein (YAP)/TEA domain (TEAD) interaction within the Hippo signaling pathway, as well as an inhibitor of autophagy. This comprehensive review explores the pharmacological activity, molecular mechanisms, structure-activity relationships, current clinical limitations, and future perspectives of verteporfin, particularly focusing on its evolving role in ophthalmology, ocular oncology, and tissue regeneration.
1. Introduction
Verteporfin (commercially known as Visudyne) is a benzoporphyrin derivative that serves as a highly effective second-generation photosensitizer [1][2]. Approved by the FDA in 2000, it is currently the only nanoparticle-based formulation that achieves targeted delivery to the eye through systemic intravenous administration [5][12]. Verteporfin was initially developed and is most widely recognized for its role in photodynamic therapy (PDT) to treat neovascular age-related macular degeneration (AMD), a leading cause of severe visual loss among the elderly [1][7]. By leveraging a light-activated mechanism, verteporfin allows for the selective destruction of abnormal blood vessels while minimizing collateral damage to the adjacent normal neurosensory retina [1][15]. In recent years, the therapeutic scope of verteporfin has expanded significantly. Researchers have discovered that even in the absence of light activation, verteporfin exhibits profound biological activities, including the inhibition of the Hippo-YAP signaling pathway and the modulation of autophagy, opening new avenues for its application in oncology and regenerative medicine [1][8].
2. Pharmacological Activity
In the field of ophthalmology, verteporfin is a first-line therapeutic agent for conditions characterized by the abnormal activation of blood vessels. Its primary clinical application is in the treatment of neovascular (wet) AMD and myopic choroidal neovascularization [2][9]. Verteporfin PDT is also the standard treatment for polypoidal choroidal vasculopathy (PCV) and is highly effective for chronic central serous chorioretinopathy (CSC) [1][11]. In ocular oncology, it has been utilized to treat localized choroidal hemangiomas, choroidal melanomas, and retinal capillary hemangiomas [1].
Clinically, verteporfin is administered intravenously (typically 6 mg/m2 of body surface area) and is subsequently activated by a non-thermal diode laser [13]. To enhance safety and reduce the risk of retinal pigment epithelium (RPE) atrophy or persistent choriocapillaris hypoperfusion, modified protocols such as half-dose (HD) or half-fluence (HF) PDT have been widely adopted, particularly for CSC [3][11]. Furthermore, verteporfin PDT is frequently combined with intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents (e.g., ranibizumab or bevacizumab). This combination therapy is synergistic: PDT induces the occlusion of abnormal vascular networks, while anti-VEGF drugs counteract the angiogenic factors released due to PDT-induced local hypoxia, leading to superior anatomical and functional outcomes in patients with retinal angiomatous proliferation (RAP) and PCV [3][13].
3. Molecular Mechanism of Action
The molecular mechanism of verteporfin can be divided into two distinct pathways: photoactivated and non-photoactivated.
Photoactivated Mechanism: When used in PDT, verteporfin is activated by a specific wavelength of red light (typically 689-690 nm) in the presence of oxygen [1][2]. Upon light absorption, the photosensitizer's low-energy electrons transition to an excited singlet state and then to an excited triplet state. These electrons transfer energy to molecular oxygen, generating highly reactive oxygen species (ROS), including singlet oxygen [1][15]. The accumulation of ROS causes severe photochemical damage to the mitochondria of the targeted vascular endothelial cells, triggering a complex cascade of apoptosis, necrosis, and autophagy [1]. This oxidative damage exposes the vascular basement membrane, leading to rapid platelet activation, aggregation, thrombosis, and ultimately, the selective occlusion of the abnormal neovascular network [1][13].
Non-Photoactivated Mechanism: Remarkably, verteporfin exerts significant pharmacological effects without laser irradiation. It is a potent inhibitor of the Yes-associated protein (YAP), a core transcriptional co-activator of the Hippo signaling pathway, which regulates tissue homeostasis, organ size, and tumorigenesis [1][10]. Verteporfin disrupts the interaction between YAP and the TEA domain (TEAD) transcription factors, promoting the cytoplasmic sequestration and degradation of YAP [1][4]. Additionally, verteporfin directly targets p62 (sequestosome 1), causing the rapid formation of covalently crosslinked, high-molecular-weight p62 oligomers. This impairs p62's ability to bind to LC3, thereby blocking autophagosome formation and effectively inhibiting early-stage autophagy [8].
4. Structure-Activity Relationship (SAR)
Verteporfin is a benzoporphyrin derivative with the chemical formula C41H42N4O8 [10]. Its core porphyrin ring structure is responsible for its light-absorbing capabilities and subsequent ROS generation [10]. Because verteporfin is highly hydrophobic, it is formulated into liposomes (Visudyne) using a repeated freeze-thaw method to enable systemic intravenous administration [1][12].
The liposomal formulation is critical to its structure-activity relationship in vivo. Once in the bloodstream, the liposomes bind to apolipoproteins, particularly low-density lipoproteins (LDL) [1][7]. Because rapidly proliferating cells—such as the abnormal neovascular endothelial cells in AMD or tumor cells—exhibit a high demand for cholesterol and overexpress LDL receptors, verteporfin is preferentially and selectively taken up by these target tissues [1]. This targeted accumulation ensures that the photodynamic cytotoxicity is localized to the pathological vasculature, providing a high degree of photosensitizing activity while sparing normal choroidal and retinal vessels [1].
5. Current Limitations
Despite its clinical success, verteporfin therapy presents several limitations. Systemically, patients may experience injection site reactions, including pain, edema, inflammation, and hemorrhage [2]. Ocular side effects can include visual impairments such as blurred vision, photopsia, reduced visual acuity, and visual field defects like scotomas [2][11].
A significant mechanistic limitation of verteporfin PDT is the induction of local tissue hypoxia. The targeted destruction and occlusion of choroidal neovascularization create a hypoxic environment that can trigger a compensatory wound-healing response. This response often leads to the upregulation of pro-angiogenic factors like VEGF, which can stimulate the recurrence of neovascularization and necessitate repeated treatments [3][15]. Furthermore, standard-dose PDT carries the risk of causing persistent choriocapillaris hypoperfusion and collateral thermal or oxidative damage to the retinal pigment epithelium (RPE), which can further impair vision over the long term [3][7].
6. Future Perspectives
The future of verteporfin in ophthalmology and beyond is highly promising, driven by advancements in drug delivery and a deeper understanding of its non-photoactivated properties. To overcome the limitations of systemic administration and rapid clearance, novel nanomedicine-based delivery systems—such as PEG-based hydrogels, mesoporous silica nanoparticles, and targeted polymeric micelles—are being developed to provide sustained, localized release of verteporfin directly to the eye [1][5].
Moreover, verteporfin's ability to inhibit the YAP/TEAD pathway without light activation positions it as a strong candidate for drug repurposing. Because the Hippo-YAP pathway is crucial for cellular plasticity, stem cell regulation, and tissue regeneration, modulating this pathway with verteporfin could offer novel therapeutic strategies for corneal regeneration and the management of ocular fibrosis [1]. Additionally, its YAP-inhibitory and autophagy-blocking effects are being actively investigated as adjuvant therapies in various solid tumors, including uveal melanoma and glioblastoma, highlighting its potential as a multifaceted pharmacological agent [4][8][10].
