Serous Retinopathy Associated withMitogen-Activated Protein Kinase KinaseInhibition (Binimetinib) for MetastaticCutaneous and Uveal Melanoma

Elon H.C. van Dijk, MD,1 Carla M.L. van Herpen, MD, PhD,2 Marina Marinkovic, MD,1,3

John B.A.G. Haanen, MD, PhD,4 Drake Amundson, BSc,5 Gré P.M. Luyten, MD, PhD,1

Martine J. Jager, MD, PhD,1 Ellen H.W. Kapiteijn, MD, PhD,6 Jan E.E. Keunen, MD, PhD,7

Grazyna Adamus, PhD,5 Camiel J.F. Boon, MD, PhD1

Purpose: To analyze the clinical characteristics of a serous retinopathy associated with mitogen-activatedprotein kinase kinase (MEK) inhibition with binimetinib treatment for metastatic cutaneous melanoma (CM) anduveal melanoma (UM), and to determine possible pathogenetic mechanisms that may lead to this retinopathy.

Design: Prospective observational, cohort-based, cross-sectional study.Participants: Thirty CM patients and 5 UM patients treated with the MEK inhibitor binimetinib (CM) or a

combination of binimetinib and the protein kinase C inhibitor sotrastaurin (UM).Methods: Extensive ophthalmic examination was performed, including Early Treatment of Diabetic

Retinopathy Study best-corrected visual acuity, applanation tonometry, slit-lamp examination, indirect ophthal-moscopy, digital color fundus photography, and optical coherence tomography (OCT). In selected cases, addi-tional examinations were performed, including visual field testing and electro-oculography (EOG). Blood sampleswere obtained from 3 CM patients and 3 UM patients to analyze the presence of autoantibodies against retinaland retinal pigment epithelium (RPE) proteins.

Main Outcome Measures: Visual symptoms, visual acuity, fundus appearance, characteristics on OCT,fundus autofluorescence (FAF), and EOG.

Results: Six CM patients (20%) and 2 UM patients (40%) reported visual symptoms during the study. Themedian time to the onset of symptoms, which were all mild and transient, was 3.5 days (range, <1 hour to 3weeks). On OCT, subretinal fluid (SRF) was detected in 77% of CM patients and 60% of UM patients. In the 26patients with SRF, the fovea was affected in 85%. After the start of the medication, an EOG was performed in 19eyes of 11 patients; 16 of these eyes (84%) developed SRF on OCT. Fifteen of these eyes (94%) showed anabnormal Arden ratio (<1.65). A broad pattern of anti-retinal antibodies was found in 3 CM patients and 2 UMpatients tested, whereas anti-RPE antibodies were detected in all 6 tested patients.

Conclusions: A time-dependent and reversible serous retinopathy can develop both in patients with met-astatic CM and UM treated with binimetinib. A minority of patients develop visual symptoms, which are generallymild and transient. A cause of binimetinib-associated serous retinopathy may be toxicity of medication, butautoantibodies also may be involved. Ophthalmology 2015;-:1e10 ª 2015 by the American Academy ofOphthalmology.

Supplemental material is available at www.aaojournal.org.

Cutaneous melanoma (CM) is an increasingly occurringmalignant skin tumor. Distant metastases, either via lym-phatics or the bloodstream, occur in 15% of patients, witha 5-year survival rate of 15% to 22%.1 Although CMrepresents only 4% of skin cancer cases, it causes 65% ofskin cancererelated deaths.2

Uveal melanoma (UM) is the most common primaryintraocular malignancy in adults. Metastasis occurs in 34%of patients within 10 years after diagnosis, and after

� 2015 by the American Academy of OphthalmologyPublished by Elsevier Inc.

detection of metastases, the 2-year survival rate is only 8%.3

Metastasis in UM occurs purely hematogenously, and theliver is involved in 95% of patients. The median survivalin these cases is 4 to 6 months, whereas the mediansurvival in cases without liver metastases is 19 to 28months.4

The treatment options for metastatic CM and UM arelimited. However, new targeted treatment options includetherapies that target the mitogen-activated protein kinase

1http://dx.doi.org/10.1016/j.ophtha.2015.05.027ISSN 0161-6420/15

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(MAPK) signaling pathway. The MAPK pathway plays acrucial role in intracellular signal transduction and inducestranscription of genes, encoding several cellular processes,such as growth, differentiation, migration, inflammation,angiogenesis, and cell death.5,6 The MAPK pathway isregulated by several growth factors, including fibroblastgrowth factor receptors, which are present on the cellsurface. The MAPK cascade can be activated by the ratsarcoma small guanidine phosphatase, which subsequentlyactivates rapidly accelerated fibrosarcoma kinase, enablingthe phosphorylation and activation of mitogen-activatedprotein kinase kinase (MEK) and, finally, extracellularsignal-regulated kinase.7

Patients with CM or UM can be subdivided on the basisof underlying genetic mutations in the melanoma cells. In52% to 86% of patients with UM and in more than 66% ofpatients with CM, uncontrolled activation and aberrantsignaling of the MAPK pathway can be detected.8 In CM,RAS and BRAF gene mutations may cause activation of theMAPK pathway.9 In UM, mutually exclusive mutations inGNAQ and GNA11 often can be found. These mutationscause a permanently activated GTP-bound state, leading tothe activation of protein kinase C and consequently theMAPK pathway.8,9

Several targeted therapies, such as the BRAF inhibitorsvemurafenib and dabrafenib, the MEK inhibitors trametinib,selumetinib, and binimetinib (MEK162), and combinationsof BRAF and MEK inhibitors, have emerged as noveltherapeutic options, especially for patients with metastaticBRAF-mutated CM.10e12 In patients with NRAS-mutatedCM, MEK inhibition by MEK162 has shown clinicalactivity.13

Retinopathy, described as a “central serouschorioretinopathy-like event,” an unspecified “chorioretin-opathy,” or a “bilateral, multifocal, mild and self-limitingretinopathy,” was described in association with binimetinibtreatment in patients with advanced or metastatic CM in 2%to 65% of patients.12,14

Little is known about the clinical characteristics,outcome, and pathogenesis of MEK inhibitoreassociatedretinopathy. In this study, we analyzed the clinical charac-teristics of retinopathy associated with MEK inhibitiontreatment for metastatic CM and UM. In addition, westudied possible pathogenetic mechanisms that may lead tosuch retinopathy, and we examined a correlation betweenthe development of retinopathy and the tumor response toMEK inhibition treatment in metastatic CM.

Methods

Patient Characteristics

Twenty patients from an academic medical center (RadboudUniversity Medical Center, Nijmegen, The Netherlands) and 10patients from a comprehensive cancer center (The NetherlandsCancer Institute Antoni van Leeuwenhoek, Amsterdam, TheNetherlands, in collaboration with the general hospital Onze LieveVrouwe Gasthuis, Amsterdam, The Netherlands) were included.These patients had a histologically confirmed, locally advanced,and unresectable or metastatic CM harboring BRAF V600E or

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NRAS mutations, confirmed by a central laboratory.12 Fromanother academic medical center (Leiden University MedicalCenter, The Netherlands), 5 patients with liver biopsy-confirmedmetastatic UM were included.

The local ethics committee approved the study. Each patientsigned informed consent, and the studies were performed inaccordance with the Declaration of Helsinki. The clinical trialswere registered in the Clinical Trial Registration as numbersNCT01320085 (Nijmegen and Amsterdam) and NCT01801358(Leiden). Within these trials, patients were included from July2011 to April 2014.

Treatment

In patients with metastatic CM, the MEK inhibitor binimetinib wasadministered in a phase II trial setting. Patients received 45 mg ofbinimetinib orally twice per day, continuously for 28 days (definedas a 1-treatment cycle, for scheduling purposes). The patients withmetastatic UM received a combination of binimetinib and theprotein kinase C inhibitor sotrastaurin (AEB071) in a phase Ib/IItrial setting. Patients with metastatic UM started with continuousdosing of binimetinib 30 or 45 mg twice daily for 28 days. Theyalso received sotrastaurin twice daily. Patients continued with thestudy medication until the development of disease progression orunacceptable toxicity.

Ophthalmic Examinations

All patients received a complete ophthalmic examination,including Early Treatment of Diabetic Retinopathy Study(ETDRS) best-corrected visual acuity (BCVA), applanationtonometry, slit-lamp examination, and indirect ophthalmoscopy.When ETDRS BCVA was not available (in 10 patients), SnellenBCVA was determined and a previously established conversionmethod was used to achieve ETDRS values.15

Dilation of pupils was achieved by topical administration of 1%tropicamide and 5% phenylephrine drops. Optical coherencetomography (OCT), using spectral-domain OCT (SpectralisHRAþOCT; Heidelberg Engineering, Heidelberg, Germany) or theCirrus OCT device (Carl Zeiss Meditec, Dublin, CA), and digitalcolor fundus photography (Topcon Corp., Tokyo, Japan) wereperformed at baseline, at day 15 of treatment cycle 1 (CM) or at day8 and day 22 of treatment cycle 1 (UM), day 2 of each treatmentcycle from cycle 2, and at the end of treatment (within 14 days afterdiscontinuation of treatment). In selected cases, enhanced-depthimaging OCT, fundus autofluorescence (FAF), and fluoresceinangiography (FA) were performed with spectral-domain OCT. Inaddition, electro-oculography (EOG) and electroretinography(ERG) were performed according to the guidelines of the Interna-tional Society for Clinical Electrophysiology of Vision in selectedcases, as well as color vision testing using the Desaturated Panel D-15 test.16e18

In 25 patients (20with CMand 5withUM), central visual analysiswas performed (Humphrey Field Analyzer, Carl Zeiss Meditec; 24-2or 30-2 SITA Standard Algorithm). One patient underwent micro-perimetry using the MAIA microperimeter (CenterVue, SpA,Padova, Italy), examining an area covering the central 15�.

Patients who reported new or worsened visual symptomsreceived an additional ophthalmic examination at their earliestconvenience. Additional ophthalmic examinations were performedas clinically indicated. When signs of ocular toxicity occurred, pa-tients received weekly ophthalmologic examinations until thesymptoms resolved or stabilized after at least 6 months of follow-up.

In this study, serous retinopathy was defined as retinal lesionson ophthalmoscopy corresponding to a localized separation of theneuroretina and retinal pigment epithelium (RPE) on OCT.

van Dijk et al � Serous Retinopathy Associated with MEK

Dose Modification in Patients with OphthalmologicSymptoms

Adverse events were assessed according to the CommonTerminology Criteria for Adverse Events version 4.03.19 Theclassification of adverse events into 4 grades and dose changesafter the occurrence of adverse events specified in the studyprotocols can be found in the Supplemental Text 1 (available atwww.aaojournal.org).

Analysis of Autoantibodies in Serum

Sera from patients were collected after the start of binimetinibtreatment. Sera were examined for anti-retinal and anti-RPEautoantibodies by Western blotting using human retinal and RPEproteins extracted from the retina or RPE, dissected from thehuman eye. A description of the analyses can be found in theSupplemental Text 2 (available at www.aaojournal.org).

Safety and Efficacy Monitoring

During every visit to the outpatient clinic of the Department ofMedical Oncology, a report was completed. After clinical assess-ment, the dose of study medication could be reduced when unac-ceptable signs of toxicity or disease progression had developed.Every 2 treatment cycles, a computed tomography scan was madefor evaluation of disease. The main efficacy end points of the studywere progression-free survival and overall survival.

Statistical Analysis

Both ETDRS BCVA at the time point of most pronounced sub-retinal fluid (SRF) on OCT and at final follow-up were comparedwith EDTRS BCVA at screening, using an independent t test inIBM SPSS Statistics, version 20.0 (SPSS Inc., Chicago, IL). Thesame statistical test was used to assess the differences inprogression-free survival and overall survival in patients with CM,in whom EOG abnormalities and SRF on OCT were and were notdetected.

Results

Patient Characteristics

The 30 patients with CM and 5 patients with UM (22 male, 13female) were aged 56.3 years (median, 56 years; range, 32e77years). The clinical characteristics of the patients with CM and UMare summarized in Table 1.

Ophthalmic Characteristics

During the period of administration of the study medication, 6patients with CM (20%) and 2 patients with UM (40%) reportedvisual symptoms. Five patients developed symptoms of blurredvision, which resolved within a few hours in 3 patients and within1 week in the other 2 patients. In 1 patient, these symptomsrecurred after 2 weeks. Dark flecks in the visual field were noticedin 2 patients after taking the study medication. One patientdeveloped persistent binocular vertical diplopia 26 days afterthe start of the study medication. Ophthalmic characteristics aresummarized in Table 1.

Subretinal fluid as seen on OCT developed in 22 binocular pa-tients, 3 monocular patients, and 1 functionally monocular patient (atotal of 48 eyes); the (converted) median ETDRS BCVA at screeningwas 86 letters (range, 72e97 letters). At final follow-up, the medianETDRS BCVA recorded in 42 eyes was 87 letters (range, 65e99

letters). The difference in ETDRS BCVA between final follow-upand baseline was not statistically significant (P ¼ 0.586).

Ophthalmoscopy revealed transparent to yellowish vitelliformfundus lesions consisting of shallow SRF that developed in 27 of35 eyes of 18 patients with CM (77%) and in 3 of 5 eyes of 5patients with UM (60%), from whom ophthalmoscopy imageswere available (Figs 1A and D, 2A and D). Patients showed singleor multifocal lesions (Table 1). Residual mild granular RPEchanges were seen after the disappearance of the lesions withSRF in 7 of 15 follow-up cases (47%).

Subretinal fluid was detected in 23 of 30 patients with CM(77%) and 3 of 5 patients with UM (60%) (Fig 1A and D).Subretinal fluid accumulation was bilateral in all patients withCM. Also, the onset of SRF accumulation was virtually identicalin both eyes of all 22 binocular patients. On OCT, lesions weredetected between a few hours and 26 days (median, 14 days)after the start of binimetinib. In 22 of 26 patients with CM/UM(85%) who showed SRF on OCT, the SRF affected the fovea.

In all 18 eyes of 10 patients of a total of 40 eyes of 22 patients(45%) with subfoveal serous SRF on OCT, the aspect of lesionswas dome-shaped (Fig 1C and F). On infrared reflectance imaging,these lesions showed a hyperreflective center surrounded by ahyporeflective zone, with a median size of 0.50 optic discdiameter (mean, 0.63; range, 0.33e1.5 disc diameter) (Fig 1Band E). In all 22 eyes of the other 12 patients (55%) withsubfoveal SRF on OCT, smaller, round, and relatively well-demarcated foveal lesions were present, which corresponded to ashallow neuroretinal detachment on OCT with a hyperreflectivesubretinal accumulation (Fig 2I and N).

The median ETDRS BCVA at the time point of most pro-nounced subfoveal SRF accumulation on OCT was 85 letters(range, 64e97 letters). No statistically significant difference(P¼ 0.572) was found between ETDRS BCVA at the time point ofmost pronounced SRF on OCT and at screening.

Subretinal fluid was also detected extrafoveally on OCT in 22of 26 patients (85%). Four of 22 patients (18%) showed onlyextrafoveal lesions (Fig 1G and H). The median total number ofextrafoveal lesions counted in the posterior pole of 21 patientswith CM and UM, based on a 30� infrared reflectancephotograph, was 7 (mean, 8.33; range, 0e27 lesions; 2 eyeswithout extrafoveal lesions) in 39 eyes.

Complete resolution of SRF on OCT within 2 weeks afterdetection of SRF was observed in 7 of 23 patients (30%) whoreceived ophthalmological follow-up. In 4 of these patients, SRFdisappeared spontaneously; in 1 patient, the SRF disappeared afterbinimetinib dose reduction; and in 2 patients, the study medicationwas stopped 3 and 6 days before complete resolution of SRF. Afterthe first detection of SRF, 6 of 14 patients (43%) showed a completeresolution at 2 months of follow-up. In all these patients, the res-olution occurred spontaneously. Persistent subfoveal or extrafovealSRF for at least 4 months after the first detection of SRF on OCTwas seen in 2 of 5 patients who had sufficient ophthalmologicalfollow-up. None of these patients had visual symptoms. Mildintraretinal fluid accumulation was present on OCT in 1 patient withCM (Fig 2AeC) and 1 patient with UM; the intraretinal fluid haddisappeared 12 and 7 days after the first detection, respectively.

In 4 of 26 patients (15%), including 3 with CM and 1 with UM,recurrence of SRF was seen after initial resolution. Subretinal fluidreappeared 9 days (range, 3e16 days) after the restart of treatment.Despite the continuation of medication, this SRF showed sponta-neous resolution in all patients. One patient with a recurrence hadsymptoms of blurred vision, which had also occurred at the firstdetection of SRF. In 3 patients with recurrence of SRF, the locationof the SRF was almost similar to that in the previous episode.In 1 patient with initial bilateral subfoveal SRF, for whom the

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Table 1. Clinical and Ophthalmic Characteristics of Cutaneous Melanoma and Uveal Melanoma Patients

CutaneousMelanoma

UvealMelanoma

Clinical characteristicsNo. of patients 30 5No. of male patients 18/30 (60%) 4/5 (80%)No. of female patients 12/30 (40%) 1/5 (20%)Mean age (yrs) 55.7 59.8Median age (yrs) 56 59

Ophthalmic characteristicsNo. of patients developing visual symptoms 6/30 (20%) 2/5 (40%)

Ophthalmoscopy images available during ophthalmological follow-up (patients) 18 5Transparent to yellowish fundus lesions (eyes) 27/35 (77%) 3/5 (60%)Single foveal lesion (eyes) 2/27 (8%) 1/3 (33%)Multifocal lesions (eyes) 25/27 (92%) 2/3 (67%)

OCT images available during ophthalmological follow-up (patients) 30 5SRF on OCT (patients) 23/30 (77%) 3/5 (60%)Foveal SRF (patients) 19/23 (82%) 3/3 (100%)

Only foveal SRF 2/19 (11%) 1/2 (50%)Foveal and extrafoveal SRF 17/19 (89%) 2/2 (100%)

Extrafoveal SRF (patients) 21/23 (91%) 0/2 (0%)Only extrafoveal SRF 4/23 (17%) 0/2 (0%)Recurrence of SRF (patients) 3/23 (13%) 1/2 (33%)

IRR images available during ophthalmological follow-up (patients) 18 3Extrafoveal lesions (eyes) 34/36 (94%) 3/3 (100%)Small, focal extrafoveal lesions (eyes) 32/36 (89%) 2/3 (66%)Larger, diffuse extrafoveal lesions (eyes) 19/36 (53%) 2/3 (66%)

FAF images available during ophthalmological follow-up (patients) 13 3Subfoveal fluid: increase central FAF, surrounded by a mildly decreased FAF (eyes) 16/26 (61%) 3/3 (100%)Extrafoveal focal fluid: slight decrease in central FAF, surrounded by an increased FAF (eyes) 15/26 (58%) 2/3 (66%)Extrafoveal diffuse fluid: mildly decreased FAF (eyes) 10/26 (38%) 1/3 (33%)

EOG available during ophthalmological follow-up (patients) 11 4Abnormal Arden ratio (<1.65) (eyes) 14/22 (64%) 4/5 (80%)*Subnormal Arden ratio (1.65e1.8) (eyes) 4/22 (18%)* 1/5 (20%)Normal Arden ratio (>1.8) (eyes) 4/22 (18%) 0/5 (0%)

Full-field ERG available during ophthalmological follow-up (patients) 0 2Decreased B-wave (eyes) 1/2 (50%)No abnormalities (eyes) 1/2 (50%)

Multifocal ERG available during ophthalmological follow-up (patients) 3 0Decreased responses (eyes) 2/6 (33%)No abnormalities (eyes) 4/6 (67%)

CM ¼ cutaneous melanoma; EOG ¼ electro-oculography; ERG ¼ electroretinography; FAF ¼ fundus autofluorescence; IRR ¼ infrared reflectance;OCT ¼ optical coherence tomography; SRF ¼ subretinal fluid; UM ¼ uveal melanoma.Clinical and ophthalmic characteristics of patients with CM and UM receiving binimetinib as a single agent (in those with CM) or a combination ofbinimetinib and sotrastaurin (in those with UM). Three of the patients in the study were (functionally) monocular: 2 patients with UM due to previoustreatment of their UM, and 1 patient with CM due to ocular trauma in childhood. One patient had received proton beam irradiation for UM in the past, and1 patient had undergone a primary enucleation for a large UM.*In 2 patients who received 30 mg of binimetinib twice daily at the time of testing and who did not show SRF at any time point during follow-up, we stillnoticed an abnormal Arden ratio in the only eye of a monocular patient with UM and a subnormal ratio in both eyes of a patient with CM.

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binimetinib was temporarily stopped, unilateral extrafovealSRF with subfoveal SRF occurred within 1 week after restartingbinimetinib (Fig 2IeU).

The FAF imaging was performed during ophthalmologicalfollow-up in 16 patients, 13 of whom had serous SRF, andabnormalities varied from a mild decrease of FAF to slightlyincreased FAF (Table 1).

One patient with serous foveal and extrafoveal lesions un-derwent multiple FA examinations during the course of SRFaccumulation and after resolution of SRF. Lesions showedmoderate hypofluorescence in the late phase of the angiogram(Fig 2DeH).

Eight patients underwent an EOG before the start of thebinimetinib therapy, which showed a normal Arden ratio (>1.8) in

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14 eyes of 7 patients, whereas 1 patient had an abnormal Ardenratio (<1.65) in both eyes without any ophthalmological abnor-malities, revealing a pathologically decreased light rise. Duringtreatment, a subsequent EOG showed a subnormal Arden ratio(1.65e1.8) in 2 eyes of 2 patients (25%), an abnormal ratio in botheyes of 1 patient (25%), and a normal ratio in the remaining 4 eyes(50%), although 3 of these eyes had developed SRF previously orat the time of testing. The normal Arden ratios were found in 1 eyeof a patient who did not develop SRF on OCT and in 3 eyes of 2patients who did develop SRF.

In 19 eyes of 11 cases, an EOGwas performed only after the start ofthe binimetinib medication, and 16 of these eyes (84%) had developedSRF. Fifteen of these eyes (94%) with SRF showed an abnormalArden ratio, and 1 eye (6%) showed a subnormal Arden ratio.

Figure 1. Spectrum of serous retinopathy associated with binimetinibtreatment. A, Fundus photograph of a 65-year-old patient with metastaticcutaneous melanoma (CM) who developed a central yellowish lesion in thefovea.B, On infrared reflectance (IRR) imaging, a lesion of approximately 1/3disc diameter was found, showing a hyperreflective center, surrounded by ahyporeflective zone. C, On optical coherence tomography (OCT) a dome-shaped accumulation of subretinal fluid (SRF) was detected. D, Foveal andextrafoveal yellowish lesions with a vitelliform aspect developing 12 days afterthe start of binimetinib treatment in a 67-year-old patient with metastaticCM. The IRR imaging showed a foveal lesion of approximately 1 optic discdiameter, again showing a hyperreflective center, surrounded by a hypore-flective zone, and multiple smaller lesions scattered throughout the posteriorpole with similar reflectance characteristics. These lesions were dome-shapedon OCT (F). G and H, Multifocal serous retinopathy with smaller round to

van Dijk et al � Serous Retinopathy Associated with MEK

Color vision testing in 17 patients, including 9 patients withsubfoveal SRF onOCT at the time of color vision testing, showed nosignificant changes in color vision during the time of follow-up. In22 patients, including 12 patients with subfoveal SRF, central visualfield analysis was within normal limits over several treatment cy-cles. In 1 monocular patient with UM, microperimetry using theMAIA microperimeter was performed when SRF was alreadydecreasing and the patient had no visual symptoms. Microperimetryrevealed a mildly decreased retinal sensitivity (Fig 3).

During the period of the administration of study medication, 1patient with UM and 1 patient with CM developed small retinalhemorrhages without signs of retinal vascular occlusion. Onepatient with CM developed papillary edema in both eyes.

Correlation between Ophthalmological Findings andOncologic Response to Binimetinib Treatment inPatients with Cutaneous Melanoma

In the 30 patients with CM, the median progression-free survival was77 days (range, 20e898 days) and the median overall survival was189.5 days (range, 24e919 days). The median overall survival was193 days (range, 24e861 days) in 23 patients who developed SRF,compared with 167 days (range, 63e919 days) in 7 patients withoutSRF. This finding was not statistically significant (P ¼ 0.595).

Autoantibody Analysis

Evidence of anti-RPE autoantibodies was found in 3 patients withCM and 3 patients with UM, and anti-retinal antibodies weredetected in 3 patients with CM and 2 patients with UM. Multipleanti-retinal autoantibodies and anti-RPE autoantibodies could bedetected in 1 patient. Anti-bestrophin antibodies were present in 1patient with CM and 2 patients with UM (Table 2).

Discussion

In this study, serous retinopathy developed in 77% of 30patients with CM and in 60% of 5 patients with UM treatedwith the MEK inhibitor binimetinib and affected the fovea in85% of these cases. However, visual symptoms developed inonly 23% of the patients. Most patients developed symptomsof blurred vision or dark flecks in the visual field within a fewhours to 3 weeks after starting the study medication, andthese symptoms generally disappeared within 1 week. In

oval lesions and larger, more indistinct and irregular lesions on IRR imaging(G), occurring 16 days after the start of binimetinib in a 64-year-old patientwith metastatic CM. Lesions were present only outside the fovea. On OCT(scanning plane depicted with light-green line in G), the smaller round/ovallesions corresponded to a dome-shaped accumulation of SRF (H, black arrow),and the larger irregular lesions corresponded to a shallow neuroretinaldetachment (H, white arrow). The space between the small and shallowneuroretinal detachments and retinal pigment epithelium was filled mainlywith hyperreflective material on OCT, presumably corresponding to accu-mulation of shed photoreceptor outer segment debris. I and J, Multiple lesionson IRR imaging (I) and the corresponding fundus autofluorescence (FAF)image (J) in binimetinib-associated serous retinopathy. On FAF, the lesionscorresponded to mildly decreased autofluorescence, in some lesions with aborder of faintly increased autofluorescence.

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some patients, visual symptoms recurred within 1 week afterrestarting the binimetinib. However, the serous SRF collec-tions in general seemed to have little visual impact: Thedifference between visual acuity at the time of most pro-nounced SRF and at screening was insignificant. At the endof study follow-up, there was no significant change in visualacuity compared to baseline pretreatment values.

In binocular patients, lesions were always bilateral andfairly symmetric. On ophthalmoscopy, foveal and extrafoveallesions could have a vitelliform aspect corresponding to dome-shaped serous neuroretinal detachments, but some patients hadmore extensive, irregular, shallow neuroretinal detachments.Multifocal areas of SRF occurred frequently outside the fovea,which is an indication of a more extensive retinal/RPEdysfunction. We did not find a clear correlation between thepresence or absence of serous retinopathy and the progression-free or overall survival of the patients with metastatic CM.

Figure 2. Multimodal imaging illustrating the clinical course of serousretinopathy associated with binimetinib treatment. AeC, Multifocal,variably sized serous neuroretinal detachments on red-free fundus photog-raphy (A) and infrared reflectance (IRR) imaging (B) in a 64-year-oldpatient with metastatic cutaneous melanoma (CM) treated with binime-tinib. Bilateral mild intraretinal fluid accumulation and a dome-shapedserous neuroretinal detachment with subretinal fluid (SRF) accumulationwere seen on optical coherence tomography (OCT) (C). The intraretinalfluid appeared 20 days after the start of binimetinib and disappeared in 12days. The binimetinib dose was tapered 7 days after appearance of theintraretinal fluid. Resolution of the intraretinal fluid occurred faster thanthe resolution of the subfoveal SRF, which was still present at ophthal-mological follow-up 11 weeks later. D and H, A 65-year-old patient withmetastatic CM with yellowish, foveal, and small, round, and oval vitelli-form extrafoveal lesions on fundus photography (D), corresponding tohyporeflective lesions with a moderately hyperreflective center on IRRimaging (E). On OCT (light-green line in E indicating scanning plane), thefoveal lesion corresponded to a focal serous neuroretinal detachment (F).On fluorescein angiography (FA), lesions showed hardly any fluorescencechanges in the early phase (G), whereas the smaller temporal lesionsshowed modest fluorescein staining in the late phase of the angiogram, andthe foveal lesions remained mostly hypofluorescent (H). No FA abnor-malities were present after resolution of the serous SRF. IeU, Evolution ofbinimetinib-associated serous retinopathy in a 45-year-old patient withmetastatic CM. At the baseline examination before the start of binimetinibtreatment, the OCT scan showed an entirely normal macular structure(M). Within 1 day after the start of binimetinib treatment (45 mg twicedaily), the patient developed bilateral small, round, and relatively well-demarcated foveal lesions without evidence of extrafoveal lesions (I).These lesions corresponded to a shallow neuroretinal detachment on OCT(N). Binimetinib was stopped to assess the effect of treatment discontin-uation on the retinopathy. Five days after the discontinuation of binime-tinib, SRF resolution was seen on OCT (O). Study medication wasrestarted at a lower dose (30 mg twice daily), and a shallow unilateral serousneuroretinal detachment reoccurred between 3 (P) and 4 days (Q) after therestart. In addition, small, round, and oval extrafoveal lesions (J), whichwere dome-shaped on OCT (K), gradually developed in these 5 days afterrestarting binimetinib. Fundus autofluorescence of the foveal lesion showedno obvious abnormalities in the fovea and only minor fundus auto-fluorescence (FAF) changes corresponding to the focal lesions superior inthe macula (L). Despite the fact that binimetinib treatment was continuedafter this reoccurrence of lesions, the foveal SRF resolved 2 days after therestart of binimetinib (R), and this resolution of the lesion persisted 6 (S),21 (T), and 43 days later (U). Resolution of the extrafoveal lesionsoccurred between 6 and 21 days later.

Figure 3. Functional findings in serous retinopathy associated with bini-metinib treatment. This 67-year-old asymptomatic patient with metastaticuveal melanoma, who previously received proton beam radiation therapy inthe left eye and was currently treated with binimetinib and sotrastaurin,showed mildly decreased retinal sensitivity (A) on microperimetry in thearea of neuroretinal detachment (B). At this moment, the patient had novisual symptoms. An electro-oculogram was made 1 week earlier, when thepatient reported symptoms of blurred vision, showing Arden ratios of 1.68(right eye) and 1.28 (left eye). However, the low Arden ratio in the left eyemay be partly due to the previous proton beam radiation therapy.

van Dijk et al � Serous Retinopathy Associated with MEK

Previous studies have described the aforementioned retinallesions associated with MEK inhibition treatment as centralserous-like chorioretinopathy,12 an eye conditionresembling central serous chorioretinopathy,14 bilateralsubfoveal neurosensory retinal detachments,20 and MEKinhibitoreassociated retinopathy.21 In our study, there wasno evidence of choroidal abnormalities or leakage fromfocal RPE defects in the patients with serous SRF. Instead,we found that the most striking abnormality besides theusually transient serous retinopathy was the profoundlyabnormal EOG. This indicates that the primary abnormalityis a panretinal dysfunction of the RPE, which can lead to aserous retinopathy supposedly due to failure of the RPEpump. Previous studies and OCT, FA, and FAF findings asin our study did not show visible structural RPE changes or“hot spots” of leakage that would have been suggestive ofcentral serous chorioretinopathy.20,21 Therefore, we suggestdescribing the phenotype as serous retinopathy. Disappear-ance of SRF was observed in 43% of patients within 8 weeksafter the start of binimetinib treatment, despite continuation ofthe study medication. A possible reason for this disappearancecould be a gradual reduced sensitivity of the RPE to medica-tion. However, the EOG remained abnormal despite SRFresolution, indicating prolonged RPE dysfunction despiteSRF resolution.

The pathogenesis of serous retinopathy associated withMEK inhibitor treatment is unclear. Serum samples of all3 patients with CM and 3 patients with UM tested forautoantibodies showed various anti-retinal and anti-RPEantibodies. Data on the possible prevalence of theseautoantibodies in individuals are scarce.22 In one study,anti-retinal autoantibodies were found in 16% of 58 healthysubjects, which was significantly lower compared withpatients with macular telangiectasia type 2.23 Autoantibodiesagainst bestrophin were present in 3 of 6 patients. Theseautoantibodies were also reported earlier in a patient withchoroidal malignant melanoma in the left eye andvitelliform lesions in the right eye.24 It has been proposedthat dysfunction of bestrophin results in abnormal fluid andion transport by the RPE.25 It is possible that treatmentwith binimetinib triggers (tumor) cells to stimulate thegeneration or release of antibodies that could play a role inthe pathogenesis of serous retinopathy. Moreover, anautoantibody attack against certain RPE epitopes couldresult in compromised RPE ion homeostasis, resulting in anabnormal EOG (which reflects changes in the standingpotential of the entire RPE), as well as a disturbed RPEpumping function of fluid from the subretinal space,resulting in serous SRF accumulation. A mechanism ofanti-RPE antibodies against the RPE protein bestrophin,which is also affected in Best vitelliform macular dystrophyas a result of BEST1 gene mutations, has been described in apatient with metastatic choroidal melanoma with vitelliformparaneoplastic retinopathy who also had a pathologicallyreduced Arden ratio on the EOG.24,25 In a patient withmetastatic melanoma with acute exudative polymorphousvitelliform maculopathy, which may resemble cases with themore extensive multifocal serous retinopathy in our study,anti-RPE antibodies to peroxiredoxin 3 (26 kDa) were foundin combination with an abnormal EOG. The autoantibodiesbecame undetectable after the exudation had resolved.26

Subretinal fluid was present on OCT in the 1 patient withCM and 2 patients with UM who showed the highestnumber of different antibodies. Multiple antibodies couldhave a higher pathogenic potential than a single antibody byenhancing pathology. However, only 1 of the 6 patientstested for autoantibodies had visual symptoms. In patientswith cancer-associated retinopathy (CAR), the presence ofanti-a-enolase autoantibodies has been described.27 Theseanti-a-enolase autoantibodies were found in only 1 patientin our study, who did not have visual symptoms. In ourstudy, neither a clear relationship between the presence ofanti-bestrophin antibodies and EOG nor a consistentpattern of specific autoantibodies in the tested patients wasfound. Therefore, the identification of a broad spectrum ofanti-retinal and anti-RPE antibodies does not necessarilymean that binimetinib-associated serous retinopathy isprimarily caused by this autoantibody attack, despite the factthat the presence of these autoantibodies is an indication ofautoimmune response.

Bearing this in mind, we hypothesize that direct toxicityof MEK inhibitor treatment to the RPE also can be animportant factor in the pathogenesis of binimetinib-associated serous retinopathy and RPE dysfunction. Thepotentially rapid onset of visual symptoms and serous

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Table 2. Analysis of Anti-retinal, AntieRetinal Pigment Epithelium, and Anti-bestrophin Antibodies in 3 Uveal Melanoma Patients and3 Cutaneous Melanoma Patients

Patient Diagnosis Anti-retinal AAbs Anti-RPE AAbs Anti-recombinant Bestrophin AAbs

58-year-old man UM 30k, 36k (GAPDH), 40k (aldolase), 46k (enolase) 40k, 46k, 60k þþ55-year-old man UM 30k, 32k, 33k, 36k (GAPDH), 40k (aldolase), 92k 36k, 40k, 118k þ64-year-old man UM negative 52k, 120k þ/�49-year-old woman CM 136k, 189k 40k, 136k þþþ70-year-old man CM 28k 37k, 70k �48-year-old man CM 30k, 33k, 36k (GAPDH), 62k, 80k 62k, 70k þ/�

Aabs ¼ antibodies; CM ¼ cutaneous melanoma; EOG ¼ electro-oculography; GAPDH ¼ glyceraldehyde-3-phosphate dehydrogenase; RPE ¼ retinalpigment epithelium; UM ¼ uveal melanoma.Analysis of anti-retinal, antieretinal pigment epithelium (RPE), and anti-bestrophin antibodies in 3 patients with UM (1 female, 2 male) and 3 patientswith CM (3 male). Of these patients, 2 with CM and 2 with UM showed subretinal fluid on optical coherence tomography and 2 with CM and 3 with UMshowed abnormal Arden ratios on electro-oculography (EOG) at ophthalmological examination during the study. Anti-retinal antibodies were detected in 3patients with CM and 2 patients with UM. None of these patients had dark adaptation difficulties or night blindness, and full-field electroretinography wasperformed in 3 of these patients. Anti-RPE antibodies were detected in all 6 patients. Anti-bestrophin antibodies were detected in 1 patient with CM and 2patients with UM. These anti-bestrophin autoantibodies were analyzed because they were detected previously in a patient with choroidal malignantmelanoma in the left eye and a vitelliform macular lesion in the right eye with a markedly abnormal EOG.24 In 2 patients in whom anti-bestrophin an-tibodies were detected and in 3 patients in whom antibodies were not detected, EOG did show an abnormal Arden ratio. In 1 patient with anti-bestrophinantibodies, EOG showed a normal Arden ratio in 1 eye and a subnormal Arden ratio in the other eye.

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retinopathy would support direct RPE toxicity as animportant contributing factor.

Serous retinopathy associated with MEK inhibitor treat-ment can be confused with several other clinical entities.Our study indicates that the clinical picture of the retinop-athy can be discerned from central serous chorioretinopathyon the basis of the occurrence of symptoms within days afteradministration of the medication, the absence of associatedRPE detachments, the absence of “hot spots” on FA, and anabnormal EOG.20,21 Melanoma-associated retinopathy(MAR) occurs most frequently in patients with metastasizedCM. Patients with MAR characteristically have a suddenstart of photopsia and may experience night blindness,scotomas, and visual field loss, with rod function beingprimarily affected.28 In CAR, both rod and cone function areaffected. An association with autoantibodies against retinalbipolar cells has been found both in MAR and CAR,29 aswell as autoantibodies against a 22-kDa neuronal antigen,a 34-kDa protein in Müller cells, transducin-b, mitofilin, andtitin in cases of MAR.30,31 Paraneoplastic vitelliform reti-nopathy resembling Best vitelliform macular dystrophy,acute exudative polymorphous vitelliform maculopathy, andadult-onset foveomacular vitelliform macular dystrophyhave been described in patients with metastatic CM andUM.32e37 In Best vitelliform macular dystrophy, a diseasecaused by autosomal dominantly inherited BEST1 genemutations that lead to an aberrant bestrophin protein in theRPE, a vitelliform lesion similar to a central serous retinaldetachment is described.25,38 An abnormal EOG and anormal full-field ERG are typically found in Best vitelliformmacular dystrophy. In autosomal recessive bestrophinop-athy, also caused by BEST1 gene mutations, the full-fieldERG also can be abnormal in addition to the abnormalEOG.39

In summary, we show that the MEK inhibitor binimetinib isassociated with a high incidence of serous retinopathy due todysfunction of the RPE. Possible pathogenetic mechanismsinclude anti-RPE and anti-retinal autoantibodies or direct RPE

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toxicity ofMEK inhibitors, which is a subject for further studies.Binimetinib-associated serous retinopathy was time-dependentand reversible despite continuation of the study medication.Ophthalmological monitoring is warranted in patients usingMEK inhibition treatment, but discontinuation of binimetinibadministration generally does not seemnecessary because of therelatively lowvisual impact and transient nature of the associatedserous retinopathy. Future studies should assess whether otherMEK inhibitors besides binimetinib are also associated with thedevelopment of a similar clinical picture.

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Footnotes and Financial Disclosures

Originally received: February 19, 2015.Final revision: May 15, 2015.Accepted: May 15, 2015.Available online: ---. Manuscript no. 2015-289.1 Department of Ophthalmology, Leiden University Medical Center,Leiden, The Netherlands.2 Department of Medical Oncology, Radboud University Medical Center,Nijmegen, The Netherlands.3 Department of Ophthalmology, Onze Lieve Vrouwe Gasthuis, Amster-dam, The Netherlands.4 Division of Medical Oncology, The Netherlands Cancer Institute Antonivan Leeuwenhoek, Amsterdam, The Netherlands.

5 Department of Ophthalmology, Oregon Health and Science University,Portland, Oregon.6 Department of Medical Oncology, Leiden University Medical Center,Leiden, The Netherlands.7 Department of Ophthalmology, Radboud University Medical Center,Nijmegen, The Netherlands.

Financial Disclosure(s):The author(s) have no proprietary or commercial interest in any materialsdiscussed in this article.

Author Contributions

Conception and design: Keunen, Boon

Data collection: van Dijk, van Herpen, Marinkovic, Haanen, Amundson,Luyten, Kapiteijn, Keunen, Adamus, Boon

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Analysis or interpretation: van Dijk, van Herpen, Amundson, Jager,Keunen, Adamus, Boon

Obtained funding: Not applicable

Overall responsibility: van Dijk, van Herpen, Marinkovic, Haanen, Luyten,Jager, Kapiteijn, Keunen, Adamus, Boon

Abbreviations and Acronyms:BCVA ¼ best-corrected visual acuity; CM ¼ cutaneous melanoma;EOG ¼ electro-oculography; ERG ¼ electroretinography;ETDRS ¼ Early Treatment of Diabetic Retinopathy Study; FAF ¼ fundus

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autofluorescence; MAPK ¼ mitogen-activated protein kinase;MAR ¼ melanoma-associated retinopathy; MEK ¼ mitogen-activatedprotein kinase kinase; OCT ¼ optical coherence tomography;RPE ¼ retinal pigment epithelium; SRF ¼ subretinal fluid; UM ¼ uvealmelanoma.

Correspondence:Camiel J.F. Boon, MD, PhD, Department of Ophthalmology, LeidenUniversity Medical Center, Department J3-S, PO Box 9600, 2300RCLeiden, The Netherlands. E-mail: c.j.f.boon@lumc.nl.