Loss of MAPK Pathway Activation in Post-Mitotic Retinal Cells as Mechanism in MEK Inhibition-Related Retinopathy in Cancer Patients

A correlation between oxidative stress and diabetic retinopathy: An updated review

Oxidative stress (OS) is a cytopathic outcome of excessively generated reactive oxygen species (ROS), down regulated antioxidant defense signaling pathways, and the imbalance between the produced radicals and their clearance. It plays a role in the genesis of several illnesses, especially hyperglycemia and its effects. Diabetic retinal illness, a micro vascular side effect of the condition, is the prime reason of diabetic related blindness. The OS (directly or indirectly) is associated with diabetic retinopathy (DR) and related consequences. The OS is responsible to induce and interfere the metabolic signaling pathways to enhance influx of the polyol cascades and hexosamine pathways, stimulate Protein Kinase-C (PKC) variants, and accumulate advanced glycation end products (AGEs). Additionally, the inequity between the scavenging and generation of ROS is caused by the epigenetic alteration caused by hyperglycemia that suppresses the antioxidant defense system. Induced by an excessive buildup of ROS, retinal changes in structure and function include mitochondrial damage, cellular death, inflammation, and lipid peroxidation. Therefore, it is crucial to comprehend and clarify the mechanisms connected to oxidative stress that underlie the development of DR.

Mitogen-Activated Pathway Kinase Inhibitor-Associated Retinopathy: Do Features Differ with Upstream versus Downstream Inhibition?

Introduction

Many cancers have derangement of the mitogen-activated pathway kinase (MAPK), making this pathway blockade a therapeutic target. However, inhibitors of MAPK can result in adverse effects including retinopathy. This study compares clinical and morphological characteristics of serous retinal disturbances in patients taking agents with variable inhibition of MAPK: either direct interference of mitogen-activated protein kinase kinase (MEK) or extracellular signal-regulated kinase (ERK) inhibitors or with indirect inhibition via interference with FGFR signaling.

Methods

This retrospective observational study of prospectively collected pooled data is from a single tertiary oncology referral center. Of 339 patients receiving MAPK inhibitors (171, 107, and 61 on FGFR, MEK, and ERK inhibitors, respectively) for treatment of metastatic cancer, this study included 128 eyes of 65 patients with evidence of retinopathy confirmed by optical coherence tomography (OCT). The main outcome was characteristics of treatment-emergent choroid/retinal OCT abnormalities as compared to baseline OCT.

Results

In all patients on one of three drug classes (FGFRi, MEKi, ERKi), the retinopathy manifested as subretinal fluid foci that were bilateral, fovea involving, and reversible without intervention. There were notable differences between the three classes of drugs: the proportion of patients with retinopathy, number of fluid foci per eye, proportion of eyes with intraretinal edema, and the proportion of symptomatic patients was least for the upstream target (FGFR inhibitors) and greatest for the downstream targets (MEK or ERK inhibitors).

Conclusion

This study shows MAPK pathway inhibitors may cause subretinal fluid foci with unique clinical and morphological characteristics depending on the target (FGFR, MEK, or ERK) implicated. Retinopathy is more common, more symptomatic, and more severe (more fluid foci, more expansive fluid configurations) the further downstream the MAPK pathway is inhibited.

Central retinal vein occlusion in the setting of fibroblast growth factor receptor inhibition

Purpose

To report a case of central retinal vein occlusion (CRVO) in a patient being treated with a fibroblast growth factor receptor (FGFR) inhibitor.

Observations

A 54-year-old female patient with endometrial cancer presented with CRVO and cystoid macular edema while receiving lenvatinib/pembrolizumab combination therapy. The patient received treatment with intravitreal bevacizumab, after which her visual acuity improved markedly, permitting the continuation of her chemotherapy regimen without recurrence of ocular adverse events.

Conclusions and Importance

Like mitogen-activated protein kinase inhibitors, FGFR inhibitors have the potential to be associated with retinal vein occlusion. In this case, visual recovery was possible with intravitreal anti-vascular endothelial growth factor therapy, and toxicity did not recur with drug reinitiation and continuation over five years of follow-up.

Retinal Toxicity Induced by Chemical Agents

Vision is an important sense for humans, and visual impairment/blindness has a huge impact in daily life. The retina is a nervous tissue that is essential for visual processing since it possesses light sensors (photoreceptors) and performs a pre-processing of visual information. Thus, retinal cell dysfunction or degeneration affects visual ability and several general aspects of the day-to-day of a person's lives. The retina has a blood-retinal barrier, which protects the tissue from a wide range of molecules or microorganisms. However, several agents, coming from systemic pathways, reach the retina and influence its function and survival. Pesticides are still used worldwide for agriculture, contaminating food with substances that could reach the retina. Natural products have also been used for therapeutic purposes and are another group of substances that can get to the retina. Finally, a wide number of medicines administered for different diseases can also affect the retina. The present review aimed to gather recent information about the hazard of these products to the retina, which could be used to encourage the search for more healthy, suitable, or less risky agents.

Choroidal vasculature analysis in MEK inhibitor-associated retinopathy

PURPOSE

To evaluate choroidal vascularity index (CVI) in patients developing mitogen-activated protein kinase kinase (MEK) inhibitor-associated retinopathy (MEKAR).

METHODS

In this prospective observational study, extensive ophthalmic examination was performed, including enhanced-depth-imaging-optical coherence tomography (EDI-OCT). EDI-OCT scans of patients receiving Cobimetinib, taken at baseline and at MEKAR manifestation, were considered for choroid analysis. Choroidal thickness (CT) was measured on high-resolution b-scans passing through the fovea at three different locations. Same scans were therefore imported for binarization into a previously reported software and CVI was calculated as the ratio of luminal area (LA) to total choroid area (TCA).

RESULTS

When compared to baseline, eyes with MEKAR (14 eyes) did not show significative CT variation in subfoveal region (p = 0,57), 750-µm-nasal to the fovea (p = 0,08) and 750-µm-temporal to the fovea (p = 0,07). Similarly, there were no statistically significant differences for TCA (p = 0.54), LA (p = 0.85), stromal area (SA) (p = 0.13), LA/SA (p = 0.34) and CVI (p = 0.47). Best-corrected visual acuity was significantly reduced at fluid accumulation when compared to baseline values (p = 0.03), with complete recovery after fluid resolution (p = 0.73).

CONCLUSION

Multiple parameters reflecting the status of the choroid seemed not influenced by Cobimetinib administration. Retinal pigment epithelium toxic disfunction likely represents the crucial step in MEKAR pathogenesis.

Clinical and Morphologic Characteristics of Extracellular Signal-Regulated Kinase Inhibitor-Associated Retinopathy

PURPOSE

To investigate clinical and morphologic characteristics of serous retinal disturbances in patients taking extracellular signal-regulated kinase (ERK) inhibitors.

DESIGN

Single-center retrospective study of prospectively collected data.

PARTICIPANTS

Of 61 patients receiving ERK inhibitors for treatment of metastatic cancer, this study included 40 eyes of 20 patients with evidence of retinopathy confirmed by OCT.

METHODS

Clinical examination, fundus photography, and OCT were used to evaluate ERK inhibitor retinopathy. The morphologic features, distribution, and location of fluid foci were evaluated serially. Visual acuity (VA) and choroidal thickness measurements were compared at baseline, fluid accumulation, and resolution.

MAIN OUTCOME MEASURES

Characteristics of treatment-emergent choroid and retinal OCT abnormalities as compared with baseline OCT findings and the impact of toxicity on VA.

RESULTS

Of 20 patients with retinopathy, most showed fluid foci that were bilateral (100%), multifocal in each eye (75%), and with at least 1 focus involving the fovea (95%). All subretinal fluid foci occurred between the interdigitation zone and an intact retinal pigment epithelium. No statistical difference was found in choroidal thickness at fluid accumulation and resolution compared with baseline. Forty-five percent of eyes showed evidence of concomitant intraretinal edema localized to the outer nuclear layer. At the time of fluid accumulation, 57.5% eyes showed a decline in VA (mainly by 1-2 lines from baseline). For all eyes with follow-up, the subretinal fluid and intraretinal edema were reversible and resolved without medical intervention, and best-corrected VA at fluid resolution was not statistically different from baseline. Concomitant intraretinal fluid was not associated with worsening of VA. No patient discontinued or decreased drug dose because of retinopathy.

CONCLUSIONS

This study showed that ERK inhibitors may cause subretinal fluid foci with unique clinical and morphologic characteristics. The observed foci were similar to mitogen-activated protein kinase kinase (MEK) inhibitor-associated retinopathy and distinct from central serous chorioretinopathy. However, unlike with MEK inhibitors, an increased occurrence of concomitant intraretinal fluid without significant additive visual impact seems to occur with ERK inhibitors. In this series, ERK inhibitors did not cause irreversible loss of vision or serious eye damage; retinopathy was self-limited and did not require medical intervention.

Clinical and Morphologic Characteristics of Fibroblast Growth Factor Receptor Inhibitor-Associated Retinopathy

Importance

Fibroblast growth factor receptor (FGFR) 1 to 4 inhibitors are approved by the US Food and Drug Administration and suppress the mitogen-activated protein kinase (MAPK) pathway, with a potential for treatment-related retinopathy. To date, implications of FGFR inhibitor-associated ocular toxic effects are poorly described. Therefore, more detailed clinical descriptions of this ocular toxic effect could help explain visual symptoms while receiving drug therapy.

Objective

To describe the clinical and morphologic characteristics of serous retinal disturbances associated with FGFR inhibitors.

Design, Setting, and Participants

In this retrospective case series, 146 patients receiving FGFR inhibitors as cancer treatment at a single tertiary referral center were included. This study included 40 eyes of 20 patients with retinopathy by optical coherence tomography (OCT). OCTs were obtained on the remaining patients and the results were judged normal. Patients were recruited from March 2012 to January 2021.

Main Outcomes and Measures

Characteristics of treatment-emergent choroidal and retinal OCT abnormalities as compared with baseline OCT, associated with visual acuity at presentation and at fluid resolution.

Results

A total of 20 of 146 patients (13.7%) exhibited FGFR inhibitor-associated retinopathy. Of these 20 patients, 11 (55%) were female, and the median (range) age was 62.6 (42.7-86.0) years. The median (range; mean) time from medication start to initial subretinal fluid detection was 21 (5-125; 32) days. The median (interquartile range [IQR]) baseline logMAR best-corrected visual acuity (BCVA) was 0 (0-0.1). At fluid accumulation, 11 eyes had decreased vision: the median (IQR) subgroup baseline BCVA was 0 (0-0.1); and the median (IQR) BCVA change from baseline to accumulation was -0.1 (-0.2 to -0.1). For 26 eyes (65%) with follow-up, the subretinal fluid resolved without medical intervention or drug interruption in all but 1 patient. At fluid resolution, the median (IQR) BCVA was 0.1 (0-0.1), and the change in median (IQR) BCVA from baseline to fluid resolution was 0 (-0.03 to 0). No patient discontinued drug therapy on account of their retinopathy.

Conclusions and Relevance

FGFR inhibitors result in subretinal fluid foci similar to other drugs that inhibit the MAPK pathway. In this series, FGFR inhibitors did not cause irreversible loss of vision; the retinopathy was self-limited and did not require medical intervention. These results may explain visual symptoms while taking the drug, although the precise frequency or magnitude of this adverse effect cannot be determined with certainty from this retrospective investigation.

Serous business: Delineating the broad spectrum of diseases with subretinal fluid in the macula

A wide range of ocular diseases can present with serous subretinal fluid in the macula and therefore clinically mimic central serous chorioretinopathy (CSC). In this manuscript, we categorise the diseases and conditions that are part of the differential diagnosis into 12 main pathogenic subgroups: neovascular diseases, vitelliform lesions, inflammatory diseases, ocular tumours, haematological malignancies, paraneoplastic syndromes, genetic diseases, ocular developmental anomalies, medication-related conditions and toxicity-related diseases, rhegmatogenous retinal detachment and tractional retinal detachment, retinal vascular diseases, and miscellaneous diseases. In addition, we describe 2 new clinical pictures associated with macular subretinal fluid accumulation, namely serous maculopathy with absence of retinal pigment epithelium (SMARPE) and serous maculopathy due to aspecific choroidopathy (SMACH). Differentiating between these various diseases and CSC can be challenging, and obtaining the correct diagnosis can have immediate therapeutic and prognostic consequences. Here, we describe the key differential diagnostic features of each disease within this clinical spectrum, including representative case examples. Moreover, we discuss the pathogenesis of each disease in order to facilitate the differentiation from typical CSC.

Central serous chorioretinopathy: An update on risk factors, pathophysiology and imaging modalities

Central serous chorioretinopathy (CSC) is a common form of vision loss, typically seen in working-age men. The pathophysiology behind CSC still eludes us, however significant advances have been made in understanding this disease over the last decade using information from genetic and cell-based studies and imaging modalities. This review aims to give an overview of the current pathophysiology hypotheses surrounding CSC in addition to future directions in cellular work from human induced pluripotent stem cell derived choroidal endothelial cells from CSC patients. Furthermore, this review will provide the reader with an update on the clinical aspects of CSC including risk factors, diagnostic challenges and findings from multimodal imaging.

OCULAR ADVERSE EVENTS ASSOCIATED WITH MEK INHIBITORS

PURPOSE

Mitogen-activates protein kinase (MAPK) inhibitors, particularly MEK inhibitors, have shifted the treatment paradigm for metastatic BRAF-mutant cutaneous melanoma; however, oncologists, ophthalmologists, and patients have noticed different toxicities of variable importance. This review aims to provide an update of the ocular adverse events (OAEs), especially retinal toxicity, associated with the use of MEK inhibitors.

METHODS

We conducted a scientific literature search using the PubMed database up to July 2018 with the terms "MEK inhibitors" with a "review" filter and "MEK inhibitors" with a "clinical trials" filter. Phase I-III experimental studies and reviews were selected. Current principles and techniques for diagnosing and managing MEK inhibitor retinopathy and other OAEs are discussed.

RESULTS

In patients treated with MEK inhibitors, including asymptomatic patients, OAEs occur with an incidence of up to 90%. Mild to severe ophthalmic toxicities are described, including visual disturbances, a 2-line decrease in Snellen visual acuity, dry eye symptoms, ocular adnexal abnormalities, visual field defects, panuveitis, and retinal toxicities, such as different degrees of MEK-associated retinopathy, vascular injury, and retinal vein occlusion.

CONCLUSION

MEK inhibitors can lead to different degrees of retinal, uveal, and adnexal OAE, causing visual disturbances or discomfort. One of the most relevant OAE of MEK therapy is MEK inhibitor-associated retinopathy (MEKAR), which is usually mild, self-limited, and may subside after continuous use of the drug for weeks or months, or discontinuation, thereby restoring the normal visual function of the retina, with some exceptions. Ocular adverse events are often associated with other systemic adverse effects that can modify the dosage of treatment, so the communication with the oncologist is fundamental.

Encorafenib, binimetinib and cetuximab combined therapy for patients with BRAFV600E mutant metastatic colorectal cancer

Approximately 10-15% of colorectal cancers (CRCs) harbor an activating BRAF mutation, leading to tumor growth promotion by activation of the mitogen-activated protein kinases pathway. BRAFV600E mutations are prognostic for treatment failure after first-line systemic therapy in the metastatic setting. In contrast to the efficacy of combined BRAF and MEK inhibition in melanoma, BRAFV600E mutant CRC is intrinsically unresponsive due to upregulation of HER/EGFR. However, combining the EGFR inhibitor cetuximab, the BRAF inhibitor encorafenib and the MEK inhibitor binimetinib improves overall survival. This review discusses the current treatment field for patients with BRAFV600E mutant metastatic CRC and summarizes the pharmacology, efficacy and safety of the novel doublet and triplet therapies consisting of encorafenib and cetuximab with or without binimetinib.

Drug-induced maculopathy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of drug-induced maculopathies including their clinical presentations, diagnostic findings, and treatment options. With the increasing pace of development and arrival of drugs to the market, this review aims to inform retina specialists of relevant side effects that may be encountered in a clinical practice setting.

RECENT FINDINGS

The major themes visited in this article focus on relevant findings of drugs that cause pigmentary and crystalline maculopathy, photoreceptor dysfunction, cystoid macular edema, central serous choroidopathy, uveitis, and vascular damage.

SUMMARY

The current review reports updated findings and discusses the pathophysiologic mechanisms, presentations, and treatments of drug-induced maculopathies.

Safety of BRAF+MEK Inhibitor Combinations: Severe Adverse Event Evaluation

Aim: The selective BRAF and MEK inhibitors (BRAFi+MEKi) have substantially improved the survival of melanoma patients with BRAF V600 mutations. However, BRAFi+MEKi can also cause severe or fatal outcomes. We aimed to identify and compare serious adverse events (sAEs) that are significantly associated with BRAFi+MEKi. Methods: In this pharmacovigilance study, we reviewed FDA Adverse Event Reporting System (FAERS) data in order to detect sAE reporting in patients treated with the combination therapies vemurafenib+cobimetinib (V+C), dabrafenib+trametinib (D+T) and encorafenib+binimetinib (E+B). We evaluated the disproportionate reporting of BRAFi+MEKi-associated sAEs. Significant associations were further analyzed to identify combination-specific safety signals among BRAFi+MEKi. Results: From January 2018 through June 2019, we identified 11,721 sAE reports in patients receiving BRAFi+MEKi. Comparison of BRAFi+MEKi combinations demonstrates that skin toxicities, including Stevens–Johnson syndrome, were disproportionally reported using V+C, with an age-adjusted reporting odds ratio (adj. ROR) of 3.4 (95%CI, 2.9–4.0), whereas fever was most significantly associated with D+T treatment with an adj. ROR of 1.9 (95%CI, 1.5–2.4). Significant associations using E+B treatment include peripheral neuropathies (adj. ROR 2.7; 95%CI, 1.2–6.1) and renal disorders (adj. ROR 4.1; 95%CI, 1.3–12.5). Notably, we found an increase in the proportion of Guillain–Barré syndrome reports (adj. ROR 8.5; 95%CI, 2.1–35.0) in patients administered E+B. Conclusion: BRAFi+MEKi combinations share a similar safety profile attributed to class effects, yet concomitantly, these combinations display distinctive effects that can dramatically impact patients’ health. Owing to the limitations of pharmacovigilance studies, some findings warrant further validation. However, the possibility of an increased risk for these events should be considered in patient care.

Clinical Development of BRAF plus MEK Inhibitor Combinations

Genomic profiling shows that many solid tumors are characterized by specific driver aberrations, and this has expanded the therapeutic options for many patients. The mitogen-activated protein kinase (MAPK) pathway is a key cell signaling pathway involved in regulating cellular growth, proliferation, and survival. Driver mutations in the BRAF gene, a key player in the MAPK pathway, are described in multiple tumor types, including subsets of melanoma, non-small cell lung cancer (NSCLC), and anaplastic thyroid cancer (ATC), making BRAF a desirable target for inhibition. BRAF inhibitors have shown efficacy in several cancers; however, most patients eventually develop resistance. To delay or prevent resistance, combination therapy targeting BRAF and MEK, a downstream signaling target of BRAF in the MAPK pathway, was evaluated and demonstrated synergistic benefit. BRAF and MEK inhibitor combinations have been approved for use in various cancers by the US FDA. We review the clinical data for various BRAF plus MEK combination regimens in three cancer types with underlying BRAF driver mutations: melanoma, NSCLC, and ATC. We also discuss practical treatment considerations and management of selected combination therapy toxicities.

Adverse events associated with encorafenib plus binimetinib in the COLUMBUS study: incidence, course and management

BACKGROUND

Dual inhibition of the mitogen-activated protein kinase pathway with BRAF/MEK inhibitor (BRAFi/MEKi) therapy is a standard treatment for BRAFV600-mutant metastatic melanoma and has historically been associated with grade III pyrexia or photosensitivity depending on the combination used. The objective of this study was to fully describe adverse events from the COLUMBUS study evaluating the most recent BRAF/MEK inhibitor combination encorafenib+binimetinib.

PATIENTS AND METHODS

Patients with locally advanced, unresectable or metastatic BRAFV600-mutant melanoma were randomised to receive encorafenib 450 mg once daily plus binimetinib 45 mg twice daily, encorafenib 300 mg once daily or vemurafenib 960 mg twice daily. Adverse events that represent known effects of available BRAFi and/or MEKi were evaluated.

RESULTS

The safety population included a total of 570 patients (encorafenib+binimetinib = 192; encorafenib = 192; vemurafenib = 186). Median duration of exposure was longer with encorafenib+binimetinib (51 weeks) than with encorafenib (31 weeks) or vemurafenib (27 weeks). Common BRAFi/MEKi toxicities with encorafenib+binimetinib were generally manageable, reversible and infrequently associated with discontinuation. Pyrexia was less frequent with encorafenib+binimetinib (18%) and encorafenib (16%) than with vemurafenib (30%) and occurred later in the course of therapy with encorafenib+binimetinib (median time to first onset: 85 days versus 2.5 days and 19 days, respectively). The incidence of photosensitivity was lower with encorafenib+binimetinib (5%) and encorafenib (4%) than with vemurafenib (30%). The incidence of serous retinopathy was higher with encorafenib+binimetinib (20%) than with encorafenib (2%) or vemurafenib (2%), but no patients discontinued encorafenib+binimetinib because of this event.

CONCLUSION

Encorafenib+binimetinib is generally well tolerated and has a low discontinuation rate in patients with BRAFV600-mutant melanoma, with a distinct safety profile as compared with other anti-BRAF/MEK targeted therapies.

TRIAL REGISTRATION

ClinicalTrials.gov (Identifier: NCT01909453) and with EudraCT (number 2013-001176-38).

FREQUENT SUBCLINICAL MACULAR CHANGES IN COMBINED BRAF/MEK INHIBITION WITH HIGH-DOSE HYDROXYCHLOROQUINE AS TREATMENT FOR ADVANCED METASTATIC BRAF MUTANT MELANOMA: Preliminary Results From a Phase I/II Clinical Treatment Trial

PURPOSE

To assess the potential ocular toxicity of a combined BRAF inhibition (BRAFi) + MEK inhibition (MEKi) + hydroxychloroquine (HCQ) regime used to treat metastatic BRAF mutant melanoma.

METHODS

Patients with stage IV metastatic melanoma and BRAF V600E mutations (n = 11, 31-68 years of age) were included. Treatment was with oral dabrafenib, 150 mg bid, trametinib, 2 mg/day, and HCQ, 400 mg to 600 mg bid. An ophthalmic examination, spectral domain optical coherence tomography, near-infrared and short-wavelength fundus autofluorescence, and static perimetry were performed at baseline, 1 month, and q/6 months after treatment.

RESULTS

There were no clinically significant ocular events; there was no ocular inflammation. The only medication-related change was a separation of the photoreceptor outer segment tip from the apical retinal pigment epithelium that could be traced from the fovea to the perifoveal retina noted in 9/11 (82%) of the patients. There were no changes in retinal pigment epithelium melanization or lipofuscin content by near-infrared fundus autofluorescence and short-wavelength fundus autofluorescence, respectively. There were no inner retinal or outer nuclear layer changes. Visual acuities and sensitivities were unchanged.

CONCLUSION

BRAFi (trametinib) + MEKi (dabrafenib) + HCQ causes very frequent, subclinical separation of the photoreceptor outer segment from the apical retinal pigment epithelium without inner retinal changes or signs of inflammation. The changes suggest interference with the maintenance of the outer retinal barrier and/or phagocytic/pump functions of the retinal pigment epithelium by effective MEK inhibition.

Carnosine improves diabetic retinopathy via the MAPK/ERK pathway

Diabetic retinopathy (DR) is one of the most common causes of blindness in developed countries. Due to its asymptomatic onset and progressive disease course, DR is typically diagnosed at a late stage when treatment options are limited and therefore often results in irreversible blindness. Studies have demonstrated that carnosine may prevent and treat DR. In a previous study, the positive effect of carnosine on DR was determined and it was revealed that there may be an association between carnosine and the mitogen-activated protein kinase (MAPK)/extracellular signal related kinase (ERK) signaling pathway. To assess the interaction between carnosine and the MAPK/ERK signaling pathway, changes in PKC, ERK and p-ERK expression was assessed in diabetic rats following treatment with carnosine, PD98059 or U46619 via reverse transcription-quantitative polymerase chain reaction and western blotting. The results demonstrated that the expression of ERK and p-ERK were significantly suppressed following treatment with carnosine, but no significant effect on the expression of PKC was identified, which indicates that suppressing the activation of the MAPK/ERK signaling pathway may serve an important role in carnosine-induced DR prevention and treatment.

Pimasertib-associated ophthalmological adverse events

PURPOSE

To analyse ophthalmological adverse events associated with mitogen-activated protein kinase kinase (MEK) inhibition with pimasertib treatment for metastatic cutaneous melanoma (CM).

METHODS

In this prospective observational, cohort-based, cross-sectional study, eight patients treated with the MEK inhibitor pimasertib received a complete ophthalmic examination. This included Early Treatment of Diabetic Retinopathy Study best-corrected visual acuity, visual field testing, colour vision testing, slit-lamp examination, applanation tonometry, indirect ophthalmoscopy, digital colour fundus photography and optical coherence tomography (OCT). In selected cases, fluorescein angiography was performed.

RESULTS

Serous subretinal fluid (SRF) developed in all patients, within a time frame of 9-27 days after the start of treatment. The fovea was involved in six of eight patients (75%). None of the patients with foveal SRF [excluding a patient who developed a bilateral retinal vein occlusion (RVO)] experienced visual symptoms. Subretinal fluid (SRF) decreased or resolved in all patients, despite continuation of study medication in six of eight patients (75%). Complaints in the CM patient (13%) consisted of experiencing a dark fleck in the inferior part of the visual field of the right eye 1 week after the start of treatment, due to an RVO. Subsequent intravitreal bevacizumab treatment resulted in functional and anatomical improvement.

CONCLUSION

Patients with metastatic CM who are treated with the MEK inhibitor pimasertib are at high risk of development of ocular adverse events including serous retinopathy and possibly RVO, stressing the need of adequate ophthalmological follow-up including OCT during administration of pimasertib, despite the fact that SRF generally does not lead to ophthalmological complaints.

The Oxidative Stress and Mitochondrial Dysfunction during the Pathogenesis of Diabetic Retinopathy

Diabetic retinopathy is one of the most serious microvascular complications induced by hyperglycemia via five major pathways, including polyol, hexosamine, protein kinase C, and angiotensin II pathways and the accumulation of advanced glycation end products. The hyperglycemia-induced overproduction of reactive oxygen species (ROS) induces local inflammation, mitochondrial dysfunction, microvascular dysfunction, and cell apoptosis. The accumulation of ROS, local inflammation, and cell death are tightly linked and considerably affect all phases of diabetic retinopathy pathogenesis. Furthermore, microvascular dysfunction induces ischemia and local inflammation, leading to neovascularization, macular edema, and neurodysfunction, ultimately leading to long-term blindness. Therefore, it is crucial to understand and elucidate the detailed mechanisms underlying the development of diabetic retinopathy. In this review, we summarized the existing knowledge about the pathogenesis and current strategies for the treatment of diabetic retinopathy, and we believe this systematization will help and support further research in this area.

Reversible Macular Lesions in the Setting of Oral Pan-Fibroblast Growth Factor Inhibitor for the Treatment of Bladder Cancer

The tyrosine kinase inhibitor, JNJ-42756493, is an oral pan-fibroblast growth factor receptor inhibitor being studied as an antineoplastic agent. It is currently the subject of a phase II clinical trial for the treatment of urothelial cancer. We report 2 patients who developed visual disturbance shortly after starting or increasing dosage of this medication and were found to have bilateral foveal detachments on ocular coherence tomography imaging. The first patient discontinued this medication and the retinal lesions resolved with a return to baseline vision within 4 to 6 weeks. After restarting the medication at a lower dose, neither visual disturbance nor retinal lesions recurred. In the second patient, lesions were found to greatly improve shortly after discontinuation of the medication but recurred even on a reduced dose regimen.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Neuro-ophthalmic side effects of molecularly targeted cancer drugs

The past two decades has been an amazing time in the advancement of cancer treatment. Molecularly targeted therapy is a concept in which specific cellular molecules (overexpressed, mutationally activated, or selectively expressed proteins) are manipulated in an advantageous manner to decrease the transformation, proliferation, and/or survival of cancer cells. In addition, increased knowledge of the role of the immune system in carcinogenesis has led to the development of immune checkpoint inhibitors to restore and enhance cellular-mediated antitumor immunity. The United States Food and Drug Administration approval of the chimeric monoclonal antibody (mAb) rituximab in 1997 for the treatment of B cell non-Hodgkin lymphoma ushered in a new era of targeted therapy for cancer. A year later, trastuzumab, a humanized mAb, was approved for patients with breast cancer. In 2001, imatinib was the first small-molecule kinase inhibitor approved. The approval of ipilimumab-the first in class immune checkpoint inhibitor-in 2011 serves as a landmark period of time in the resurgence of immunotherapy for cancer. Despite the notion that increased tumor specificity results in decreased complications, toxicity remains a major hurdle in the development and implementation of many of the targeted anticancer drugs. This article will provide an overview of the current cellular and immunological understanding of cancer pathogenesis-the foundation upon which molecularly targeted therapies were developed-and a description of the ocular and neuro-ophthalmic toxicity profile of mAbs, immune checkpoint inhibitors, and small-molecule kinase inhibitors.