Blenrep (belantamab mafodotin) is a medication used to treat adults with relapsed or refractory multiple myeloma, a type of blood cancer. This targeted therapy delivers a cytotoxic agent directly to cancer cells. A common side effect of Blenrep is ocular toxicity, which can affect vision and eye health.
How Blenrep Affects the Eyes
Blenrep can cause eye damage primarily through a condition called keratopathy. Keratopathy refers to changes or damage to the cornea, which is the clear, outermost layer at the front of the eye. The drug’s cytotoxic component, monomethyl auristatin F (MMAF), is internalized by corneal epithelial cells through an off-target mechanism, leading to cell death. This process results in microcyst-like corneal epithelial changes, which are tiny, fluid-filled sacs that form on the surface of the cornea.
The drug reaches the corneal epithelium through the tear film or the vascularized limbal region, the area where the cornea meets the white part of the eye. These microcysts are typically multiple, bilateral, and affect the superficial cornea. While keratopathy is the most common ocular adverse reaction, Blenrep can also induce other changes like decreased visual acuity.
Recognizing Eye Symptoms
Patients undergoing Blenrep treatment may experience various eye symptoms due to ocular toxicity. Blurred vision is a frequently reported symptom, affecting a significant percentage of patients, ranging from 22% to 33% depending on the dose. Dry eyes are another common complaint, reported by 14% to 25% of patients. Patients might also experience light sensitivity, known as photophobia, or general eye pain and discomfort.
Symptoms can fluctuate in severity, from mild irritation to more pronounced visual impairment. In some cases, patients may experience a decline in visual acuity, with some reporting severe vision loss (20/200 or worse) in the better-seeing eye. Symptom onset typically ranges from nine days to nine months after starting Blenrep, with a median onset around 36 days. Any new or worsening eye symptoms, such as difficulty reading, trouble driving at night, or eye irritation, should be promptly reported to a healthcare provider.
Managing Eye Health During Treatment
Managing ocular health during Blenrep treatment involves proactive monitoring and supportive care. Regular eye examinations by an ophthalmologist are recommended before starting Blenrep, prior to each treatment cycle (typically every three weeks), and if symptoms worsen. These exams usually include an assessment of visual acuity and a slit lamp examination to check for corneal changes. The Keratopathy and Visual Acuity (KVA) scale is often used to grade the severity of ocular toxicity and guide treatment decisions.
Dose modifications or temporary interruptions of Blenrep may be necessary based on the severity of ocular toxicity. For instance, if severe keratopathy occurs, treatment may be held until the condition improves to a milder grade.
Patients are often advised to use preservative-free lubricating eye drops at least four times a day, starting with the first infusion and continuing throughout treatment. Patients with a history of dry eyes may benefit from additional therapies and should avoid contact lenses. Patient education about potential symptoms and adherence to eye care instructions are important for managing these side effects. The corneal changes are generally reversible with dose modification or discontinuation of therapy.