- Email: [email protected]
Enhanced Benefit in Diabetic Macular Edema from AKB-9778 Tie2 Activation Combined with Vascular Endothelial Growth Factor Suppression
Enhanced Benefit in Diabetic Macular Edema from AKB-9778 Tie2 Activation Combined with Vascular Endothelial Growth Factor Suppression Peter A. Campochiaro, MD,1 Arshad Khanani, MD,2 Michael Singer, MD,3 Sunil Patel, MD,4 David Boyer, MD,5 Pravin Dugel, MD,6,7 Saleema Kherani, MD,1 Barbara Withers, PhD,8 Laura Gambino, BS,8 Kevin Peters, MD,8 Mitchell Brigell, PhD,8 for the TIME-2 Study Group Purpose: To assess the effect of AKB-9778 alone or in combination with ranibizumab in subjects with diabetic macular edema (DME). Design: A phase IIa, randomized, placebo- and sham injectionecontrolled, double-masked clinical trial. Participants: Subjects (n ¼ 144) with decreased vision from DME and central subfield thickness (CST) 325 mm measured by spectral-domain optical coherence tomography (SD OCT) enrolled at 36 sites. Methods: Subjects were randomized to (1) AKB-9778 monotherapy: subcutaneous AKB-9778 15 mg twice per day (BID) þ monthly sham intraocular injections; (2) combination therapy: subcutaneous AKB-9778 15 mg BID þ monthly 0.3 mg ranibizumab; or (3) ranibizumab monotherapy: subcutaneous placebo injections BID þ monthly 0.3 mg ranibizumab. Best-corrected visual acuity (BCVA) and CST were measured at baseline and every 4 weeks. Main Outcome Measures: Primary outcome measure was mean change from baseline CST at week 12. Other outcomes included BCVA, safety assessments, and Diabetic Retinopathy Severity Score (DRSS). Results: At week 12, mean change from baseline CST was significantly greater in the combination group (164.424.2 mm) compared with the ranibizumab monotherapy group (110.417.2 mm; P ¼ 0.008) and was 6.213.0 mm in the AKB-9778 monotherapy group. Mean CST at week 12 and percentage of eyes with resolved edema was 340.011.2 mm and 29.2%, respectively, in the combination group versus 392.117.1 mm and 17.0%, respectively, in the ranibizumab monotherapy group. Mean change from baseline BCVA (letters) was 6.31.3 in the combination group, 5.71.2 in the ranibizumab monotherapy group, and 1.51.2 in the AKB-9778 monotherapy group. The percentage of study eyes that gained 10 or 15 letters was 8.7% and 4.3%, respectively, in the AKB-9778 monotherapy group, 29.8% and 17.0%, respectively, in the ranibizumab monotherapy group, and 35.4% and 20.8%, respectively, in the combination group. Improvements in DRSS in study eyes were similar across groups, and the percentage of qualified fellow eyes with a 2-step change was 11.4% in all AKB-9778-treated subjects compared with 4.2% in the ranibizumab monotherapy group. AKB-9778 was well tolerated, with no clear by-treatment differences in adverse events. Conclusions: Activation of Tie2 by subcutaneous injections of AKB-9778 combined with suppression of vascular endothelial growth factor (VEGF) causes a significantly greater reduction in DME than that seen with suppression of VEGF alone. Ophthalmology 2016;-:1e9 ª 2016 by the American Academy of Ophthalmology. Supplemental material is available at www.aaojournal.org.
The worldwide prevalence of diabetes was estimated to be 8.3% in 2013, a total of 382 million people.1 Because of demographic changes and the increasing prevalence of obesity, the incidence in 2035 is estimated to be 592 million people. A meta-analysis of 35 population-based studies worldwide suggests that 6.81% of the diabetic population have diabetic macular edema (DME).2 By extrapolating this prevalence to the 2013 worldwide diabetes prevalence, it is estimated that 26 million adults 2016 by the American Academy of Ophthalmology Published by Elsevier Inc.
have DME today. This prevalence is estimated to increase to 40 million people in 2035, representing a large and rapidly growing public health crisis. Retinal hypoxia3 and the hypoxia-regulated gene product, vascular endothelial growth factor (VEGF),4 play key roles in the pathogenesis of DME. Intraocular injection of a VEGF-neutralizing protein is first-line treatment for DME and provides benefit in many patients,5e9 but there is a substantial percentage of patients in whom anti-VEGF http://dx.doi.org/10.1016/j.ophtha.2016.04.025 ISSN 0161-6420/16
1
Ophthalmology Volume -, Number -, Month 2016 injections are not sufficient to eliminate edema or provide a clinically significant improvement in visual acuity. These patients may experience permanent reductions in visual acuity over time from the damaging effects of chronic, recurrent edema.10,11 New treatments are needed to address the unmet medical need of such patients. Tyrosine kinase with immunoglobulin-like and epidermal growth factorelike domains 2 (Tie2) is a tyrosine kinase receptor that, like VEGF receptor-2, is located on vascular endothelial cells and has been implicated in the modulation of vascular permeability.12e14 However, although phosphorylation of VEGF receptor-2 stimulates vascular leakage, phosphorylation of Tie2 activates downstream pathways that suppress vascular leakage and promote vascular stabilization. Angiopoietin 1 is an endogenous full agonist that stimulates phosphorylation of Tie2.15 Angiopoietin 2 is an endogenous weak, partial agonist that competes with angiopoietin 1, thereby suppressing Tie2 phosphorylation.16,17 Tie2 also is regulated by vascular endothelial protein tyrosine phosphatase (VE-PTP), also known as “human protein tyrosine phosphatase beta,” which is physically associated with Tie2. It dephosphorylates Tie2, thereby reducing Tie2 activation and signaling through the Tie2 pathway.18 Levels of both angiopoietin 2 and VE-PTP are increased by hypoxia, leading to accentuated VEGF-mediated ocular neovascularization and vascular leakage.19e23 Preclinical models have shown that VE-PTP inhibition, even in the presence of high angiopoietin 2, restores Tie2 activation.23 Thus, activating Tie2 by inhibiting VE-PTP could provide a means of enhancing the effects of VEGF blockade in retinal and choroidal vascular diseases. AKB-9778 is a small-molecule inhibitor of VE-PTP that stimulates phosphorylation of Tie2 in vascular endothelial cells and suppresses VEGF-induced leakage and neovascularization in mouse models relevant to DME and neovascular age-related macular degeneration.23 In subjects with DME, treatment for 28 days with subcutaneous injections of 15 mg twice per day (BID) caused a substantial reduction in intraretinal fluid with associated improvement in visual acuity in some but not all subjects.24 This study was designed to further explore the activity of 15 mg BID AKB-9778 in subjects with DME and to determine whether combined treatment with AKB-9778 and ranibizumab caused a significantly greater reduction in DME than treatment with ranibizumab alone.
Methods This was a phase IIa, randomized, placebo- and sham injectione controlled, double-masked clinical trial conducted at 40 sites in the United States, 36 of which enrolled at least 1 subject. The study was carried out with institutional review board approval. Informed consent for the research was obtained from all subjects, and the study complied with the Declaration of Helsinki and the Health Insurance Portability and Accessibility Act. The study was registered at www.clinicaltrials.gov under the identifier NCT02050828, January 29, 2014. The duration of the study was 5 months, with a 3-month treatment period and a 2-month follow-up observation period.
2
Subject Eligibility and Exclusion Criteria Eligible subjects were aged 18 to 80 years with type 1 or type 2 diabetes and decreased vision from DME. The major eligibility criteria for the study eye included best-corrected visual acuity (BCVA) 76 letters and 24 letters using the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity charts, and retinal central subfield thickness (CST) 325 mm measured by spectral-domain optical coherence tomography (SD OCT). Systemic exclusion criteria were (1) hemoglobin A1c 12%, (2) resting systolic blood pressure 170 mmHg, or (3) diastolic blood pressure 100 mmHg. Ocular exclusion criteria were (1) any potential contributing causes of reduced visual acuity other than DME, (2) focal/grid laser treatment within 3 months, (3) intraocular surgery or an intraocular injection of a steroid within 12 weeks, or (4) intraocular injection of a VEGF-neutralizing protein within 8 weeks. One eye was selected as the study eye. If both eyes met eligibility criteria, the more severely affected eye was designated as the study eye.
Randomization and Treatments Subjects were randomized to 1 of 3 treatment groups: (1) AKB9778 monotherapy: subcutaneous AKB-9778 15 mg BID þ monthly sham intraocular injection; (2) combination therapy: subcutaneous AKB-9778 15 mg BID þ monthly intraocular injection of 0.3 mg ranibizumab; or (3) ranibizumab monotherapy: subcutaneous placebo injection BID þ monthly intraocular injection of 0.3 mg ranibizumab. By using a central interactive web response randomization system, eligible subjects were assigned in a double-masked fashion to 1 of the 3 treatment groups in a 1:1:1 ratio. To maintain balance between treatment groups with respect to DME severity, randomization was stratified by the following study eye variables: screening ETDRS BCVA (55 vs. >55 letters) as determined by the investigator and screening CST (450 vs. >450 mm) as determined by the Johns Hopkins University Retinal Imaging Research and Reading Center (Baltimore, MD). The study design was double masked; patients, care providers, and personnel assessing outcomes were all masked to treatment. AKB-9778 was supplied as a sterile solution for subcutaneous administration packaged in a clear glass prefilled syringe sealed with a Flurotec-coated stopper (Albany Molecular Research, Inc., Burlington, MA). Each syringe was filled to a volume of 0.75 ml, which delivered a dose of 15 mg AKB-9778. The matching placebo formulation was supplied as a sterile solution for subcutaneous administration packaged in a clear glass prefilled syringe sealed with a Flurotec-coated stopper. Each syringe was filled to a volume of 0.75 ml. AKB-9778 and placebo were packaged in study medication/kit boxes in masked fashion and shipped by Xerimis, Inc., to the investigative sites. Each study medication box contained 14 sterile prefilled syringes (sufficient for 1 week of BID dosing).
Study Protocol The proposed dose, frequency, and duration of treatment were selected on the basis of the results from a study of normal volunteers, a phase Ib study in subjects with DME,24 and nonclinical safety and pharmacology studies. The active dosing period was 3 months followed by a 2-month observation period. Study visits were scheduled for 4, 8, 12, 16, and 20 weeks after baseline. The primary outcome measure was change from baseline CST measured by SD OCT at week 12. Secondary outcome measures at week 12 included change from baseline BCVA, change from baseline Diabetic Retinopathy Severity Score (DRSS) and safety assessments, and pharmacokinetic analysis. Screening assessments included medical history, vital signs, physical examination, BCVA
Campochiaro et al
Benefit of Tie2 Activation in DME
measured by the protocol established for the ETDRS,25 slit-lamp examination, indirect ophthalmoscopy, SD OCT, fundus photographs, fluorescein angiography, an electrocardiogram, and safety laboratory tests. At each study visit, subjects underwent assessment for adverse events (AEs), concomitant medications, vital signs, physical and eye examinations, BCVA, SD OCT, and safety laboratory tests. Plasma AKB-9778 concentrations were obtained 30 and 90 minutes after the first AKB-9778 dose. During the active treatment period, a study eye or qualified fellow eye was eligible for rescue treatment if any 1 of the following criteria were met: a decrease from baseline BCVA 15 letters, a decrease from baseline BCVA 10 letters and an increase from baseline CST 70 mm, or a decrease from BCVA 15 letters. During the observation period, a study eye or qualified fellow eye was eligible for rescue treatment if any 1 of the following criteria were met: an increase in baseline BCVA 3 letters and an increase from baseline CST 50 mm, a decrease from end-of-treatment BCVA 15 letters, or a decrease from end-of-treatment BCVA 10 letters and an increase from end-of-treatment CST 70 mm. A nonqualified fellow eye could receive rescue treatment for DME at any time at the discretion of the investigator.
Study Treatments All pre- and postinjection procedures were performed identically for 0.3 mg ranibizumab and sham intraocular injections by an unmasked investigator who did not communicate with masked evaluating investigators or other study personnel. Sham injections were performed by pressing the hub of a syringe without a needle against the conjunctiva to simulate the force of an intraocular injection. Subjects were trained to self-administer abdominal subcutaneous injections during the baseline visit. They were instructed to eat a meal or snack, to drink 1 to 2 glasses of fluids before injections, and to remain seated for approximately 15 minutes after injections. The first dose each day was administered in the morning (approximately the same time each day), and the evening dose was administered within 8 to 16 hours of the morning dose. Subjects maintained subcutaneous medication diaries noting the time and location of injections.
Optical Coherence Tomography Heidelberg Spectralis (Heidelberg Engineering, Inc., Heidelberg, Germany) or Cirrus (Carl Zeiss Meditec, Inc., Dublin, CA) SD OCT scans were obtained at each visit. The following scan acquisition parameters were used for Heidelberg Spectralis: (1) volume scan (20 20 , w66 mm) with 25 B-scans in horizontal orientation spaced 240 mm apart, minimum automatic real-time mean of 9, high speed (512 A-scans); (2) raster scan (30 5 ) with 7 B-scans in horizontal orientation spaced 240 mm apart, minimum automatic real-time mean of 25, high resolution (1536 A-scans). All scans after the day 1 (baseline) visit were acquired with the TruTrac eye tracker using the progression scan function. The following scan acquisition parameters were used for Cirrus: (1) macular cube 512128 scan (66-mm square grid) with 128 horizontal B-scan lines each composed of 512 A-scans; (2) 5-line raster scan with 5 horizontal B-scans where each line scan is 6 mm in length and spaced 250 mm apart. Images were graded, with manual correction of algorithms and grid alignment if required, using the Heidelberg Eye Explorer 1.9.10.0, HRA/Spectralis Viewing Module 6.0.9.0 for SD OCT, and Cirrus HD-OCT Review Software 6.5.0.772 for high-definition optical coherence tomography at the Johns Hopkins University Retinal Imaging Research and Reading Center (Baltimore, MD). Resolution of edema at the week 12 primary end point was defined as a CST of 300 mm for Spectralis scans and 282 mm for Cirrus scans. The
difference of 18 mm between Spectralis and Cirrus is the mean of the reported differences of 17 and 19.2 mm.26,27 Excess foveal thickness was determined by subtracting 300 mm from Spectralis scan values and 282 mm from Cirrus scan values.
Fundus Photography and Fluorescein Angiography Modified 7 standard field fundus photographs and a fluorescein angiogram were obtained for both eyes using a 30 fundus camera at the screening and week 12 visits. In addition, fundus photographs were acquired at the week 20 visit. Fundus photographs and a fluorescein angiogram were graded for DRSS by the Digital Angiography Reading Center (New York, NY) using the ETDRS protocol.28
Pharmacokinetic Analysis Plasma samples were obtained 30 and 90 minutes after the first dose of AKB-9778, and levels of AKB-9778 were measured at a central laboratory using a validated liquid chromatographyemass spectrometry and liquid chromatographyetandem mass spectrometry method.
Statistical Analysis Sample size was selected on the basis of published data for ranibizumab and the previous phase Ib study of AKB-9778.24 With 40 subjects in the AKB-9778 monotherapy group, the study has 83.7% power to demonstrate a statistically significant reduction from baseline in CST, assuming that the true mean reduction from baseline is 55 mm with an estimated standard deviation of 130 mm using a 1-sample 1-sided test with a significance level of 0.05. Statistical analyses were performed on a modified intent-to-treat population that included all randomized patients who had at least 1 assessment after treatment. For analysis of data obtained during the 3-month treatment period, the last observation was carried forward for patients who did not complete the study. Change from baseline measurements within treatment groups and comparisons between treatment groups were made using a 1-way analysis of covariance with the baseline value as the covariate. The independent samples t test was used for comparisons made between any 2 groups for parametric variables, and the ManneWhitney test was used for nonparametric variables. Categoric variables were compared using the chi-square test. A criterion significance level of <0.05 was used. No correction for multiple comparisons was used.
Results Subject Disposition A total of 144 subjects with clinically significant DME and CST >325 mm were enrolled. A total of 93% of subjects (134/144) completed the 12-week active treatment period: 43 subjects (89.6%) in the AKB-9778 monotherapy group, 44 subjects (93.6%) in the ranibizumab monotherapy group, and 47 subjects (95.9%) in the combination group. Of the 134 subjects who remained in the trial through the 12-week primary end point, compliance with subcutaneous study medication dosing was 97.8% across all subjects, with compliance among the treatment groups ranging from 97.0% for the combination group to 98.3% for the ranibizumab monotherapy group. The prespecified population for the primary and secondary efficacy outcome analysis was the modified intent-to-treat population, defined as subjects who had efficacy data collected after initiation of dosing and consisted of 141 subjects: 46 in the AKB-9778 monotherapy
3
Ophthalmology Volume -, Number -, Month 2016 group, 47 in the ranibizumab monotherapy group, and 48 in the combination group. The last observation was carried forward to week 12.
Subject Demographics and Baseline Characteristics The average age at enrollment was 61.3 years and similar among treatment groups (Table 1). The subject population differs from most other interventional trials for DME in that the mean duration of DME was 5 to 6 years and the majority of subjects, approximately 60%, had been previously treated with anti-VEGF intraocular injections. The mean baseline BCVA in ETDRS letter score was approximately 60 (20/63 Snellen equivalent) in each of the treatment groups, and mean CST was well balanced, ranging from 465.0 to 504.4 mm.
Anatomic Outcomes There was no reduction in mean CST at week 12 in subjects treated with AKB-9778 monotherapy. Although 10.9% of subjects in the AKB-9778 monotherapy group showed 50% reduction in excess foveal thickness, some subjects showed increased CST, so overall there was no mean change. The mean reduction (standard error of the mean) from baseline CST was 164.424.2 mm in the combination group versus 110.417.2 mm in the ranibizumab monotherapy group (P ¼ 0.008 by analysis of covariance with baseline CST as the covariate) (Fig 1). Observed data for those subjects completing through week 12 were similar; the mean reduction (standard error of the mean) from baseline CST was 168.924.3 mm in the combination group versus 106.717.8 mm in the ranibizumab monotherapy group (P ¼ 0.008). Figure 2 is a waterfall plot in which the bars show the change from baseline CST for each study eye in the combination group (orange) and the ranibizumab monotherapy group (blue). As can be seen, more subjects in the combination group had large reductions in CST. The mean CST at week 12 was 340.011.2 mm, with 29.2% of eyes with resolved edema, in the combination group versus 392.117.1 mm (P ¼ 0.03), with 17.0% (P ¼ 0.22) of eyes with resolved edema, in the ranibizumab monotherapy group. In the combination group, 70.8% of patients had a reduction of excess foveal thickness of 50% compared with 55.3% (P ¼ 0.14) of patients treated with ranibizumab monotherapy.
Figure 1. Mean change in central subfield thickness (CST) as a function of time for each treatment group. Vertical bars represent the standard error of the mean. *Statistical comparison between combination and ranibizumab (RBZ) groups at that time point by analysis of covariance, with baseline CST as the covariate.
Visual Acuity Outcomes The mean change from baseline BCVA at week 12 was 1.51.2 letters in the AKB-9778 monotherapy group, 5.71.2 letters in the ranibizumab monotherapy group, and 6.31.3 letters in the combination group (Table 2) (P ¼ 0.74 for the difference between the ranibizumab group vs. the combination group). The percentage of eyes that gained 10 letters was 8.7% in the AKB-9778 monotherapy group, 29.8% in the ranibizumab monotherapy group, and 35.4% in the combination group (P ¼ 0.66 for ranibizumab group vs. combination group). An improvement of 15 letters was observed in 4.3%, 17.0%, and 20.8% in the AKB-9778 monotherapy, ranibizumab monotherapy, and combination groups, respectively (P ¼ 0.79 for ranibizumab group vs. combination group).
Effect on Background Diabetic Retinopathy The severity of diabetic retinopathy was analyzed in eyes with nonproliferative diabetic retinopathy (DRSS grade <7). At baseline, the mean DRSS was similar among treatment groups: 4.80.17, 4.70.18, and 4.80.18 for the AKB-9778 monotherapy, ranibizumab monotherapy, and combination groups,
Table 1. Demographics and Baseline Characteristics of Subjects in the Efficacy Population AKB-9778 Monotherapy (n [ 46) Age (yrs), mean SEM Female sex, n (%) Race, n (%) White African American Others Subjects with prior anti-VEGF, n (%) Type of diabetes, n (%) Type I DM Type II DM BCVA (letters), mean SEM (Snellen equivalent) CST (mm), mean SEM
61.31.1 22 (47.8) 40 (87.0) 5 (10.9) 1 (2.1) 26 (56.5) (n ¼ 45) 3 (6.7) 42 (93.3) 61.22.1 (20/63) 465.016.9
Ranibizumab Monotherapy (n [ 47) 61.21.3 14 (29.8) 41 (87.2) 3 (6.4) 3 (6.4) 32 (68.1) (n ¼ 45) 5 (11.1) 40 (88.9) 59.22.0 (20/63) 502.420.1
AKB-9778 Combination (n [ 48) 61.31.3 23 (47.9) 41 (85.4) 4 (8.3) 3 (6.3) 27 (56.3) (n ¼ 46) 9 (19.6) 37 (80.4) 60.31.8 (20/63) 504.420.3
P Value 0.99 0.12 0.64
0.43 0.19
0.77 0.30
BCVA ¼ best-corrected visual acuity; CST ¼ central subfield thickness; DM ¼ diabetes mellitus; SEM ¼ standard error of the mean; VEGF ¼ vascular endothelial growth factor.
4
Campochiaro et al
Benefit of Tie2 Activation in DME
Figure 2. Waterfall plot of individual subject change in central subfield thickness (CST) for AKB-9778 combination therapy subjects and ranibizumab monotherapy subjects. Each bar represents an individual subject. For each group, subjects are ordered from largest increase in CST to largest decrease in CST.
respectively. The percentage of subjects with a 2-step improvement in DRSS in the study eye between screening and week 12 was similar among the 3 groups (Fig 3). In the ranibizumab monotherapy group, 24 of 47 fellow eyes had background diabetic retinopathy that was not treated with local VEGF suppression or systemic AKB-9778, and 4.2% of these eyes showed 2-step improvement in DRSS. In the AKB-9778 monotherapy and combination groups, 70 of 94 fellow eyes had background diabetic retinopathy, and 11.4% of these eyes showed 2-step improvement in DRSS (P ¼ 0.149 for fellow eyes of patients who received AKB-9778 vs. fellow eyes of patients who received no AKB-9778).
Safety and Tolerability AKB-9778 was generally well tolerated. The incidence of AEs by treatment group is shown in Table 3. Of the 528 AEs reported in the study, the majority were considered mild or moderate in severity. Twelve subjects had severe AEs (AKB-9778 monotherapy, 2; ranibizumab monotherapy, 5; AKB-9778 combination, 5). No deaths were reported in the study, and of the 6 serious AEs (2 noncardiac chest pain, 1 dizziness and dehydration, 1 toe amputation, 1 hyperglycemia, and 1 pneumonia), none were considered related to the study medication. Five subjects withdrew from active treatment because of an AE (1 urticaria, 1 worsening of DME, 1 worsening of congestive heart failure, 1 third nerve palsy, 1 noncardiac chest pain). The most common ocular AEs were worsening of DME, worsening visual acuity, and vitreous floaters (Table 4). The majority of the worsening of DME events occurred during the observation period or in the fellow eye. Ocular AEs were evenly distributed between treatment groups. The most commonly reported nonocular AEs were dizziness, nausea, fatigue, vomiting, and cough (Table 5). Among the AKB-9778 Table 2. Comparison of Visual Outcomes at Month 3 for Subjects in the Efficacy Population AKB-9778 Ranibizumab AKB-9778 Monotherapy Monotherapy Combination (n [ 46) (n [ 47) (n [ 48) Mean change in BCVA from BL, letters 2 lines, % of subjects 3 lines, % of subjects
1.5
5.7
6.3
8.7 4.3
29.8 17.0
35.4 20.8
BCVA ¼ best corrected visual acuity; BL ¼ baseline.
monotherapy and combination group subjects, AEs of dizziness and fatigue tended to occur more frequently (16.5% and 10.3%, respectively) than in the ranibizumab monotherapy subjects (8.5% and 4.3%, respectively). Twenty-two of the 29 events (75.8%) were considered mild, and the remaining 7 events were moderate in intensity. Fourteen of these events had a duration of less than 7 days, and an additional 8 events were characterized as transient, occurring after subcutaneous dosing. The remaining 7 events were chronic (6 mild dizziness, 1 moderate dizziness, 2 mild fatigue). Two of these chronic events resolved despite continued dosing, 2 resolved at the end of the treatment period, and 3 continued through the observation period. No AEs in these categories resulted in subject withdrawal from treatment. Asymptomatic reductions in blood pressure occurred after the first dose of AKB-9778. Mean systolic blood pressure while sitting was reduced by 10.0 mmHg at 30 minutes and 9.2 mmHg at 90 minutes in AKB-9778-treated subjects from a mean baseline systolic blood pressure of 138.4 mmHg, compared with an increase of 2.2 mmHg at 30 minutes and a decrease of 0.1 mmHg at 90 minutes after sham subcutaneous injection in the ranibizumab monotherapy group with a mean baseline systolic blood pressure of 142.2 mmHg. The change from mean baseline systolic blood pressure at the end of 12 weeks of treatment was similar between AKB-9778-treated subjects (0.8 mmHg) and ranibizumab monotherapy subjects (þ0.8 mmHg). AKB-9778 did not increase orthostatic blood pressure changes.
Discussion Tie2 activation renders endothelial cells less responsive to pro-angiogenic and pro-permeability factors, promoting vascular stability. This is a critical function that requires tight regulation that is achieved through titration of an endogenous full agonist, angiopoietin 1, and an endogenous weak partial agonist, angiopoietin 2; and regulation of an endothelial tyrosine phosphatase, VE-PTP. Hypoxia increases the expression of both angiopoietin 2 and VE-PTP, which collaborate to limit Tie2 activation and downstream signaling, creating a permissive environment for VEGFmediated vascular leakage and neovascularization. Inhibition of VE-PTP restores Tie2 activation, even in the presence of excess angiopoietin 2, providing an appealing strategy to treat DME and other retinal vascular diseases. AKB-9778 is a small-molecule inhibitor of VE-PTP that suppresses VEGF-induced vascular leakage and enhances vascular stability.23,29 In this study, 11% of DME subjects treated with BID subcutaneous injections of 15 mg AKB9778 as monotherapy for 12 weeks showed a 50% reduction of excess foveal thickness; however, the majority of subjects showed no effect, and there was no reduction from mean baseline CST. Although further dose ranging may reveal greater efficacy, these results indicate that monotherapy with AKB-9778 15 mg BID is not a viable approach to treat DME. The combination of subcutaneous injections of AKB9778 and monthly intraocular injections of 0.3 mg of ranibizumab resulted in a significantly greater reduction in macular edema than monthly ranibizumab monotherapy. Compared with 17% of study eyes in the ranibizumab monotherapy group, 29% in the combination group had resolution of edema. The final mean CST of 340.0 mm in the
5
Ophthalmology Volume -, Number -, Month 2016
Figure 3. Percentage of study eyes (left) and fellow eyes (right) with nonproliferative diabetic retinopathy at baseline that had a 2-step improvement in Diabetic Retinopathy Severity Score after 3 months of treatment. For study eyes, results are displayed for eyes treated with AKB-9778 monotherapy, ranibizumab (RBZ) monotherapy, or AKB-9778 combination therapy. For fellow eyes, results are displayed for eyes treated with placebo or AKB-9778.
combination group indicates that, on average, there was little residual edema in subjects receiving combination therapy. Improvements in BCVA often lag behind improvements in CST, and therefore it was not surprising that statistically significant differences in visual outcome measures between treatment groups was not seen; nor was the study powered to detect significant differences. However, there were trends favoring better outcomes in the combination group, suggesting that longer and larger trials could potentially identify a significant visual benefit. There was no difference among the 3 treatment groups in the percentage of study eyes that showed a 2-step improvement in DRSS. Because 3 injections of ranibizumab
4 weeks apart have been shown to cause an improvement in DRSS,30 it is interesting that eyes of subjects treated with AKB-9778 alone had similar rates of DRSS improvement. Fellow eyes with diabetic retinopathy in the ranibizumab monotherapy group provide an untreated control group in which the percentage of eyes with 2step improvement in DRSS was 4.2% compared with 11.2% in fellow eyes with diabetic retinopathy of subjects who received systemic AKB-9778. Although the study was not powered to detect such a difference and it was not statistically significant, these data suggest that the vascular stabilizing effects of Tie2 activation with AKB9778 may promote improvement in background diabetic
Table 3. Overall Summary of Adverse Events: Safety Population Category Total reported AEs Ocular AEs Nonocular AEs Subjects with any AE Mild Moderate Severe Total reported treatment-related AEs Subjects with any treatment-related AE Mild Moderate Severe Serious AEs Subjects with any serious AE Subjects discontinued or withdrawn because of AE
AKB-9778 Monotherapy (N [ 48) 142 46 96 39 19 18 2 44 19 17 2 0 3 3 3
(93/49) (17/29) (76/20) (32/25) (18/15) (13/9) (1/1) (37/7) (17/5) (15/4) (2/1) (0/0) (2/1) (2/1) (3/0)
Ranibizumab Monotherapy (N [ 47) 177 67 110 36 16 15 5 44 11 7 3 1 0 0 1
(134/43) (45/22) (89/21) (34/17) (15/7) (14/9) (5/1) (44/0) (11/0) (7/0) (3/0) (1/0) (0/0) (0/0) (1/0)
AKB-9778 Combination (N [ 49) 209 79 130 43 21 17 5 51 21 12 7 2 3 3 1
(156/53) (48/31) (108/22) (39/24) (19/17) (17/5) (3/2) (47/4) (20/3) (12/0) (6/2) (1/1) (2/1) (2/1) (1/0)
AE ¼ adverse event. Data are total number (number in treatment period/number in observation period). N in the headers represents the total number of subjects enrolled in each respective treatment group within the safety population. Subjects experiencing >1 AE are counted once under the maximal severity for the summary by severity.
6
Campochiaro et al
Benefit of Tie2 Activation in DME
Table 4. Summary of Ocular Treatment-Emergent Adverse Events Reported in More Than 5% of All Subjects: Safety Population AKB-9778 Monotherapy (N [ 48) Adverse Event Diabetic retinal edema worse Treatment period Observation period Visual acuity reduced Treatment period Observation period Vitreous floaters Treatment period Observation period
Ranibizumab Monotherapy (N [ 47)
AKB-9778 Combination (N [ 49)
Events
Subjects
Events
Subjects
Events
Subjects
13 5 8 6 2 4 0 0 0
10 4 6 5 2 4 0 0 0
14 6 8 3 2 1 6 6 0
12 6 6 2 2 1 4 4 0
23 9 14 6 3 3 5 3 2
15 7 11 3 2 2 4 2 2
(5) (1) (4) (3) (2) (1) (0) (0) (0)
(5) (1) (4) (2) (2) (1) (0) (0) (0)
(7) (2) (5) (2) (1) (1) (3) (3) (0)
(7) (2) (5) (1) (1) (1) (3) (3) (0)
(8) (1) (7) (4) (2) (2) (4) (3) (1)
(8) (1) (7) (3) (2) (2) (3) (2) (1)
Data are total no. (no. in study eyes).
vasodilation.35 Activation of Tie2 stimulates endothelial NO synthase and elevates NO, which could counter the negative effects of systemic suppression of VEGF.36 Overexpression of angiopoietin 2 and Tie2 inactivation may contribute to other diabetic vascular complications, including diabetic nephropathy,37,38 and if this is the case, subcutaneous AKB-9778 could have additional advantages. Systemic exposure to AKB-9778 also could increase the chance of side effects. However, AKB-9778 demonstrated a favorable safety profile in this study. Only 4 of 97 patients (4.1%) discontinued study medication because of an AE, and all of these AEs were due to complications of diabetes mellitus rather than to the study drug. The overall incidence of AEs was similar between the treatment groups, but the incidence of dizziness and fatigue was increased in patients receiving AKB-9778 compared with those receiving ranibizumab monotherapy. All of the dizziness and fatigue AEs in AKB-9778 subjects were mild to moderate in intensity, and the majority of events occurred transiently after dosing. There were no by-treatment differences in serious AEs, severe AEs, physical examination findings, ophthalmology examination, or laboratory abnormalities. Studies of longer duration will further characterize the safety and tolerability of AKB-9778 in subjects with DME.
retinopathy. This notion is supported by the proposed role of reduced Tie2 signaling in the earliest stages of diabetic retinopathy31 and is consistent with the known effects of Tie2 activation reducing inflammation and vascular leakage, enhancing endothelial viability, and maintaining the normal investment of mature vessels with pericytes and smooth muscle cells.32 The potential beneficial effect of AKB-9778 on diabetic retinopathy deserves more detailed investigation in future trials. Delivery of AKB-9778 by subcutaneous injections allows for the potential advantage of patient self-administration. Systemic delivery of AKB-9778 has the additional advantage of treating both eyes in patients with bilateral DME, and when used in combination with intraocular injections of VEGF-neutralizing proteins, there is a theoretical benefit of protection from systemic vascular complications of VEGF suppression. Systemic exposure to high levels of a VEGF antagonist reduces activity of endothelial nitric oxide (NO) synthase and thus levels of NO, causing vasoconstriction and hypertension.33 The mechanism by which VEGF antagonists promote thrombosis or hemorrhage in regions of the vasculature with previously compromised endothelium is not completely clear,34 but NO reduction is thought to play a role because NO promotes endothelial cell viability and
Table 5. Summary of Nonocular Treatment-Emergent Adverse Events Reported in More Than 5% of All Subjects: Safety Population AKB-9778 Monotherapy (N [ 48) Adverse Event
Events, n
Dizziness Treatment period Observation period Nausea Treatment period Observation period Fatigue Treatment period Observation period Vomiting Treatment period Observation period Cough Treatment period Observation period
8 8 0 4 4 0 5 5 0 3 2 1 1 1 0
Subjects, n (%) 8 8 0 4 4 0 5 5 0 3 2 1 1 1 0
(16.7) (16.7) (0.0) (8.3) (8.3) (0.0) (10.4) (10.4) (0.0) (6.3) (4.2) (2.1) (2.1) (2.1) (0.0)
Ranibizumab Monotherapy (N [ 47) Events, n 6 6 0 6 5 1 2 2 0 4 3 1 3 2 1
Subjects, n (%) 4 4 0 3 3 1 2 2 0 2 1 1 3 2 1
(8.5) (8.5) (0.0) (6.4) (6.4) (2.1) (4.3) (4.3) (0.0) (4.3) (2.1) (2.1) (6.4) (4.3) (2.1)
AKB-9778 Combination (N [ 49) Events, n 9 9 0 7 7 0 5 5 0 4 4 0 4 3 1
Subjects, n (%) 8 8 0 7 7 0 5 5 0 3 3 0 4 3 1
(16.3) (16.3) (0.0) (14.3) (14.3) (0.0) (10.2) (10.2) (0.0) (6.1) (6.1) (0.0) (8.2) (6.1) (2.0)
7
Ophthalmology Volume -, Number -, Month 2016 In conclusion, this study showed that Tie2 activation by subcutaneously administered AKB-9778 in combination with anti-VEGF therapy is more effective than anti-VEGF therapy alone in reducing DME. This is the first demonstration of clinical benefit in a randomized, placebo-controlled trial of any therapy in combination with anti-VEGF in DME. Improvements in DRSS suggest that subcutaneous AKB-9778 monotherapy may be effective in the treatment of diabetic retinopathy in subjects with or without DME. Inhibition of VE-PTP with AKB-9778 restores Tie2 activation in the diseased retina and is an appealing strategy to treat diabetic eye disease and other retinal and choroidal vascular diseases.
References 1. Guariquata L, Whiting DR, Hambleton I, et al. Global estimates of diabetes prevalence for 2013 and projections for 2035. Diabetes Res Clin Pract 2014;103:137–49. 2. Yau JW, Rogers SL, Kawasaki R, et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care 2012;35:556–64. 3. Nguyen QD, Shah SM, Van Anden E, et al. Supplemental inspired oxygen improves diabetic macular edema; a pilot study. Invest Ophthalmol Vis Sci 2003;45:617–24. 4. Nguyen QD, Tatlipinar S, Shah SM, et al. Vascular endothelial growth factor is a critical stimulus for diabetic macular edema. Am J Ophthalmol 2006;142:961–9. 5. Nguyen QD, Shah SM, Heier JS, et al. Primary end point (six months) results of the Ranibizumab for Edema of the mAcula in Diabetes (READ-2) Study. Ophthalmology 2009;116: 2175–81. 6. Nguyen QD, Brown DM, Marcus DM, et al. Ranibizumab for diabetic macular edema. Results from 2 Phase III Randomized Trials: RISE and RIDE. Ophthalmology 2012;119:789–801. 7. Heier JS, Clark WL, Boyer DS, et al. Intravitreal aflibercept injection for macular edema due to central retinal vein occlusion: two-year results from the COPERNICUS study. Ophthalmology 2014;121:1414–20. 8. Korobelnik JF, Do DV, Schmidt-Erfurth U, et al. Intravitreal aflibercept for diabetic macular edema. Ophthalmology 2014;121:2247–54. 9. The Diabetic Retinopathy Clinical Research Network. Aflibercept, bevacizumab, or ranibizumab for diabetic macular edema. N Engl J Med 2015;372:1193–203. 10. Do DV, Nguyen QD, Khwaja AA, et al. Ranibizumab for edema of the macula in diabetes trial; 3-year outcomes and the need for prolonged frequent treatment. Arch Ophthalmol 2013;131:139–45. 11. Channa R, Sophie R, Khwaja AA, et al. Factors affecting visual outcomes in patients with diabetic macular edema treated with ranibizumab. Eye (Lond) 2013;28:269–78. 12. Wong AL, Haroon ZA, Werner S, et al. Tie2 expression and phosphorylation in angiogenic and quiescent adult tissues. Circ Res 1997;81:567–74. 13. Thurston G, Suri C, Smith K, et al. Leakage-resistant blood vessels in mice transgenically overexpressing angiopoietin-1. Science 1999;286:2511–5. 14. Thurston G, Rudge JS, Ioffe E, et al. Angiopoietin-1 protects the adult vasculature against plasma leakage. Nat Med 2000;6: 460–3.
8
15. Davis S, Aldrich TH, Jones P, et al. Isolation of angiopoietin1, a ligand for the TIE2 receptor, by secretion-trap expression cloning. Cell 1996;87:1161–9. 16. Maisonpierre PC, Suri C, Jones PF, et al. Angiopoietin-2, a natural antagonist for Tie2 that disrupts in vivo angiogenesis. Science 1997;277:55–60. 17. Yuan HT, Khankin EV, Karumanchi SA, Parikh SM. Angiopoietin 2 is a partial agonist/antagonist of Tie2 signaling in the endothelium. Mol Cell Biol 2009;29:2011–22. 18. Yacyshyn OK, Lai PFH, Forse K, et al. Tyrosine phosphatase beta regulates angiopoietin-Tie2 signaling in human endothelial cells. Angiogenesis 2009;12:25–33. 19. Hackett SF, Ozaki H, Strauss RW, et al. Angiopoietin 2 expression in the retina: upregulation during physiologic and pathologic neovascularization. J Cell Physiol 2000;184: 275–84. 20. Hackett SF, Wiegand SJ, Yancopoulos G, Campochiaro P. Angiopoietin-2 plays an important role in retinal angiogenesis. J Cell Physiol 2002;192:182–7. 21. Oshima Y, Deering T, Oshima S, et al. Angiopoietin-2 enhances retinal vessel sensitivity to vascular endothelial growth factor. J Cell Physiol 2004;199:412–7. 22. Oshima Y, Oshima S, Nambu H, et al. Different effects of angiopoietin 2 in different vascular beds in the eye; new vessels are most sensitive. FASEB J 2005;19:963–5. 23. Shen J, Frye M, Lee BL, et al. Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature. J Clin Invest 2014;124:4564–76. 24. Campochiaro PA, Sophie R, Tolentino M, et al. Treatment of diabetic macular edema with an inhibitor of vascular endothelial-protein tyrosine phosphatase that activates Tie2. Ophthalmology 2015;122:545–54. 25. The Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema. Early Treatment Diabetic Retinopathy Study report number 1. Arch Ophthalmol 1985;103:1796–806. 26. Lammer J, Scholda C, Prunte C, et al. Retinal thickness and volume measurements in diabetic macular edema: a comparison of four optical coherence tomography systems. Retina 2011;31:48–55. 27. Hatef E, Khwaja A, Rentiya Z, et al. Comparison of time domain and spectral-domain optical coherence tomography in measurement of macular thickness in macular edema secondary to diabetic retinopathy and retinal vein occlusion. J Ophthalmol 2012;2012:354783. 28. The Early Treatment Diabetic Retinopathy Study Research Group. Grading diabetic retinopathy from stereoscopic color fundus photographs-an extension of the modified Airlie House classification. ETDRS Report Number 10. Ophthalmology 1991;98(5 Suppl):786–806. 29. Goel S, Gupta N, Walcott BP, et al. Effects of vascularendothelial protein tyrosine phosphatase inhibition on breast cancer vasculature and metastatic progression. J Natl Cancer Inst 2013;105:1188–201. 30. Ip MS, Domalpally A, Hopkins JJ, et al. Long-term effects of ranibizumab on diabetic retinopathy severity and progression. Arch Ophthalmol 2012;130:1145–52. 31. Hammes H-P, Feng Y, Pfister F, Brownlee M. Diabetic retinopathy: targeting vasoregression. Diabetes 2011;60: 9–16. 32. Augustin HG, Koh GY, Thurston G, Alitalo K. Control of vascular morphogenesis and homeostasis through the angiopoietin-Tie system. Nat Rev Mol Cell Biol 2009;10: 165–77.
Campochiaro et al
Benefit of Tie2 Activation in DME
33. Robinson ES, Khankin EV, Choueiri TK, et al. Suppression of the nitric oxide pathway in metastatic renal cell carcinoma patients receiving vascular endothelial growth factor-signaling inhibitors. Hypertension 2010;56:1131–6. 34. Zuo P-Y, Chen X-L, Liu Y-W, et al. Increased risk of cerebrovascular events in patients with cancer treated with bevacizumab: a meta-analysis. PLoS One 2014;9:e102484. 35. Dimmeler S, Fleming I, Fisslthaler B, et al. Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation. Nature 1999;399:601–5.
36. Alfieri A, Ong AC, Kammerer RA, et al. Angiopoietin-1 regulates microvascular reactivity and protects the microcirculation during acute endothelial dysfunction: role of eNOS and VE-cadherin. Pharmacol Res 2014;80:43–51. 37. Davis B, Dei Cas A, Long DA, et al. Podocyte-specific expression of angiopoietin-2 causes proteinuria and apoptosis of glomerular endothelia. J Am Soc Nephrol 2007;18:2320–9. 38. Dei Cas A, Gnudi L. VEGF and angiopoietins in diabetic glomerulopathy: how far for a new treatment? Metabolism 2012;61:1666–73.
Footnotes and Financial Disclosures Originally received: January 18, 2016. Final revision: April 15, 2016. Accepted: April 15, 2016. Available online: ---. Manuscript no. 2016-116. 1 Johns Hopkins, Wilmer Eye Institute, Baltimore, Maryland.
S.P.: Grants e Alcon, Ophthotech, Genentech, Allergan, Regeneron.
2
Sierra Eye Associates, Reno, Nevada.
D.B.: Consultant e Aerpio Therapeutics, Alcon, Allegro, Allergan, Bausch & Lomb, Bayer, CoDa Therapeutics, ForeSight Biotherapeutics, Erigen Inc., Genentech, GlaxoSmithKline, Neurotech, Notal Vision, Novartis Ophthalmics, Ophthotech, Ohr, Optos, Regeneron, RetroSense Therapeutics, Sun Pharmaceuticals, Stem Cells Inc., ThromboGenics.
3
Medical Center Ophthalmology Associates, San Antonio, Texas.
B.W., L.G., K.P., M.B.: Employees e Aerpio Therapeutics.
4
Retina Research Institute of Texas, Abilene, Texas.
This study was funded by Aerpio Therapeutics, Cincinnati, Ohio.
5
Retina Vitreous Associates Medical Group, Beverly Hills, California.
Author Contributions:
6
Retinal Consultants of Arizona, Phoenix, Arizona.
Conception and design: Campochiaro, Withers, Gambino, Peters, Brigell
7
USC Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California.
8
Aerpio Therapeutics, Cincinnati, Ohio.
Data collection: Campochiaro, Khanani, Singer, Patel, Boyer, Dugel, Kherani Analysis and interpretation: Campochiaro, Kherani, Withers, Gambino, Peters, Brigell
Members of the TIME-2 study group are listed in the Appendix (available at www.aaojournal.org).
Obtained funding: Not applicable
Financial Disclosure(s): The author(s) have made the following disclosure(s): P.A.C.: Consultant e Aerpio Therapeutics, Alimera, Applied Genetic Technologies, Eleven Biotherapeutics, AsclipiX, Genentech/Roche, Kala Pharmaceuticals, Rxi Pharmaceuticals, Akebia, Regeneron, Allegro, Intrexon, RegenX; Institutional grants e AbbVie, Aerpio Therapeutics, Allergan, Genentech/Roche, Genzyme, GlaxoSmithKline, Oxford Biomedica, Regeneron, RegenX, Rxi Pharmaceuticals; Royalties e Graybug; Equity e Alimera, Allegro, Graybug.
Abbreviations and Acronyms: AE ¼ adverse event; BCVA ¼ best-corrected visual acuity; BID ¼ twice per day; CST ¼ central subfield thickness; DME ¼ diabetic macular edema; DRSS ¼ Diabetic Retinopathy Severity Score; ETDRS ¼ Early Treatment Diabetic Retinopathy Study; NO ¼ nitric oxide; SD OCT ¼ spectral-domain optical coherence tomography; Tie2 ¼ tyrosine kinase with immunoglobulin-like and epidermal growth factorelike domains 2; VEGF ¼ vascular endothelial growth factor; VE-PTP ¼ vascular endothelial-protein tyrosine phosphatase.
A.K.: Grants e Aerpio Therapeutics, Genentech; Personal fees e Genentech, Novartis, Allergan; Nonfinancial support e Genentech, Novartis. M.S.: Research support and personal fees (Advisory Committee) e Aerpio Therapeutics; Consultant e Genentech, Allergan; Grants Regeneron, Ampio, Allegro, Stem Cells Inc., Acucela, Optos, Neurotech.
Overall responsibility: Campochiaro, Kherani, Withers, Gambino, Brigell
Correspondence: Peter A. Campochiaro, MD, Maumenee 815, The Wilmer Eye Institute, Johns Hopkins University, 600 N. Wolfe Street, Baltimore, MD 21287. E-mail: [email protected].
9
The worldwide prevalence of diabetes was estimated to be 8.3% in 2013, a total of 382 million people.1 Because of demographic changes and the increasing prevalence of obesity, the incidence in 2035 is estimated to be 592 million people. A meta-analysis of 35 population-based studies worldwide suggests that 6.81% of the diabetic population have diabetic macular edema (DME).2 By extrapolating this prevalence to the 2013 worldwide diabetes prevalence, it is estimated that 26 million adults 2016 by the American Academy of Ophthalmology Published by Elsevier Inc.
have DME today. This prevalence is estimated to increase to 40 million people in 2035, representing a large and rapidly growing public health crisis. Retinal hypoxia3 and the hypoxia-regulated gene product, vascular endothelial growth factor (VEGF),4 play key roles in the pathogenesis of DME. Intraocular injection of a VEGF-neutralizing protein is first-line treatment for DME and provides benefit in many patients,5e9 but there is a substantial percentage of patients in whom anti-VEGF http://dx.doi.org/10.1016/j.ophtha.2016.04.025 ISSN 0161-6420/16
1
Ophthalmology Volume -, Number -, Month 2016 injections are not sufficient to eliminate edema or provide a clinically significant improvement in visual acuity. These patients may experience permanent reductions in visual acuity over time from the damaging effects of chronic, recurrent edema.10,11 New treatments are needed to address the unmet medical need of such patients. Tyrosine kinase with immunoglobulin-like and epidermal growth factorelike domains 2 (Tie2) is a tyrosine kinase receptor that, like VEGF receptor-2, is located on vascular endothelial cells and has been implicated in the modulation of vascular permeability.12e14 However, although phosphorylation of VEGF receptor-2 stimulates vascular leakage, phosphorylation of Tie2 activates downstream pathways that suppress vascular leakage and promote vascular stabilization. Angiopoietin 1 is an endogenous full agonist that stimulates phosphorylation of Tie2.15 Angiopoietin 2 is an endogenous weak, partial agonist that competes with angiopoietin 1, thereby suppressing Tie2 phosphorylation.16,17 Tie2 also is regulated by vascular endothelial protein tyrosine phosphatase (VE-PTP), also known as “human protein tyrosine phosphatase beta,” which is physically associated with Tie2. It dephosphorylates Tie2, thereby reducing Tie2 activation and signaling through the Tie2 pathway.18 Levels of both angiopoietin 2 and VE-PTP are increased by hypoxia, leading to accentuated VEGF-mediated ocular neovascularization and vascular leakage.19e23 Preclinical models have shown that VE-PTP inhibition, even in the presence of high angiopoietin 2, restores Tie2 activation.23 Thus, activating Tie2 by inhibiting VE-PTP could provide a means of enhancing the effects of VEGF blockade in retinal and choroidal vascular diseases. AKB-9778 is a small-molecule inhibitor of VE-PTP that stimulates phosphorylation of Tie2 in vascular endothelial cells and suppresses VEGF-induced leakage and neovascularization in mouse models relevant to DME and neovascular age-related macular degeneration.23 In subjects with DME, treatment for 28 days with subcutaneous injections of 15 mg twice per day (BID) caused a substantial reduction in intraretinal fluid with associated improvement in visual acuity in some but not all subjects.24 This study was designed to further explore the activity of 15 mg BID AKB-9778 in subjects with DME and to determine whether combined treatment with AKB-9778 and ranibizumab caused a significantly greater reduction in DME than treatment with ranibizumab alone.
Methods This was a phase IIa, randomized, placebo- and sham injectione controlled, double-masked clinical trial conducted at 40 sites in the United States, 36 of which enrolled at least 1 subject. The study was carried out with institutional review board approval. Informed consent for the research was obtained from all subjects, and the study complied with the Declaration of Helsinki and the Health Insurance Portability and Accessibility Act. The study was registered at www.clinicaltrials.gov under the identifier NCT02050828, January 29, 2014. The duration of the study was 5 months, with a 3-month treatment period and a 2-month follow-up observation period.
2
Subject Eligibility and Exclusion Criteria Eligible subjects were aged 18 to 80 years with type 1 or type 2 diabetes and decreased vision from DME. The major eligibility criteria for the study eye included best-corrected visual acuity (BCVA) 76 letters and 24 letters using the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity charts, and retinal central subfield thickness (CST) 325 mm measured by spectral-domain optical coherence tomography (SD OCT). Systemic exclusion criteria were (1) hemoglobin A1c 12%, (2) resting systolic blood pressure 170 mmHg, or (3) diastolic blood pressure 100 mmHg. Ocular exclusion criteria were (1) any potential contributing causes of reduced visual acuity other than DME, (2) focal/grid laser treatment within 3 months, (3) intraocular surgery or an intraocular injection of a steroid within 12 weeks, or (4) intraocular injection of a VEGF-neutralizing protein within 8 weeks. One eye was selected as the study eye. If both eyes met eligibility criteria, the more severely affected eye was designated as the study eye.
Randomization and Treatments Subjects were randomized to 1 of 3 treatment groups: (1) AKB9778 monotherapy: subcutaneous AKB-9778 15 mg BID þ monthly sham intraocular injection; (2) combination therapy: subcutaneous AKB-9778 15 mg BID þ monthly intraocular injection of 0.3 mg ranibizumab; or (3) ranibizumab monotherapy: subcutaneous placebo injection BID þ monthly intraocular injection of 0.3 mg ranibizumab. By using a central interactive web response randomization system, eligible subjects were assigned in a double-masked fashion to 1 of the 3 treatment groups in a 1:1:1 ratio. To maintain balance between treatment groups with respect to DME severity, randomization was stratified by the following study eye variables: screening ETDRS BCVA (55 vs. >55 letters) as determined by the investigator and screening CST (450 vs. >450 mm) as determined by the Johns Hopkins University Retinal Imaging Research and Reading Center (Baltimore, MD). The study design was double masked; patients, care providers, and personnel assessing outcomes were all masked to treatment. AKB-9778 was supplied as a sterile solution for subcutaneous administration packaged in a clear glass prefilled syringe sealed with a Flurotec-coated stopper (Albany Molecular Research, Inc., Burlington, MA). Each syringe was filled to a volume of 0.75 ml, which delivered a dose of 15 mg AKB-9778. The matching placebo formulation was supplied as a sterile solution for subcutaneous administration packaged in a clear glass prefilled syringe sealed with a Flurotec-coated stopper. Each syringe was filled to a volume of 0.75 ml. AKB-9778 and placebo were packaged in study medication/kit boxes in masked fashion and shipped by Xerimis, Inc., to the investigative sites. Each study medication box contained 14 sterile prefilled syringes (sufficient for 1 week of BID dosing).
Study Protocol The proposed dose, frequency, and duration of treatment were selected on the basis of the results from a study of normal volunteers, a phase Ib study in subjects with DME,24 and nonclinical safety and pharmacology studies. The active dosing period was 3 months followed by a 2-month observation period. Study visits were scheduled for 4, 8, 12, 16, and 20 weeks after baseline. The primary outcome measure was change from baseline CST measured by SD OCT at week 12. Secondary outcome measures at week 12 included change from baseline BCVA, change from baseline Diabetic Retinopathy Severity Score (DRSS) and safety assessments, and pharmacokinetic analysis. Screening assessments included medical history, vital signs, physical examination, BCVA
Campochiaro et al
Benefit of Tie2 Activation in DME
measured by the protocol established for the ETDRS,25 slit-lamp examination, indirect ophthalmoscopy, SD OCT, fundus photographs, fluorescein angiography, an electrocardiogram, and safety laboratory tests. At each study visit, subjects underwent assessment for adverse events (AEs), concomitant medications, vital signs, physical and eye examinations, BCVA, SD OCT, and safety laboratory tests. Plasma AKB-9778 concentrations were obtained 30 and 90 minutes after the first AKB-9778 dose. During the active treatment period, a study eye or qualified fellow eye was eligible for rescue treatment if any 1 of the following criteria were met: a decrease from baseline BCVA 15 letters, a decrease from baseline BCVA 10 letters and an increase from baseline CST 70 mm, or a decrease from BCVA 15 letters. During the observation period, a study eye or qualified fellow eye was eligible for rescue treatment if any 1 of the following criteria were met: an increase in baseline BCVA 3 letters and an increase from baseline CST 50 mm, a decrease from end-of-treatment BCVA 15 letters, or a decrease from end-of-treatment BCVA 10 letters and an increase from end-of-treatment CST 70 mm. A nonqualified fellow eye could receive rescue treatment for DME at any time at the discretion of the investigator.
Study Treatments All pre- and postinjection procedures were performed identically for 0.3 mg ranibizumab and sham intraocular injections by an unmasked investigator who did not communicate with masked evaluating investigators or other study personnel. Sham injections were performed by pressing the hub of a syringe without a needle against the conjunctiva to simulate the force of an intraocular injection. Subjects were trained to self-administer abdominal subcutaneous injections during the baseline visit. They were instructed to eat a meal or snack, to drink 1 to 2 glasses of fluids before injections, and to remain seated for approximately 15 minutes after injections. The first dose each day was administered in the morning (approximately the same time each day), and the evening dose was administered within 8 to 16 hours of the morning dose. Subjects maintained subcutaneous medication diaries noting the time and location of injections.
Optical Coherence Tomography Heidelberg Spectralis (Heidelberg Engineering, Inc., Heidelberg, Germany) or Cirrus (Carl Zeiss Meditec, Inc., Dublin, CA) SD OCT scans were obtained at each visit. The following scan acquisition parameters were used for Heidelberg Spectralis: (1) volume scan (20 20 , w66 mm) with 25 B-scans in horizontal orientation spaced 240 mm apart, minimum automatic real-time mean of 9, high speed (512 A-scans); (2) raster scan (30 5 ) with 7 B-scans in horizontal orientation spaced 240 mm apart, minimum automatic real-time mean of 25, high resolution (1536 A-scans). All scans after the day 1 (baseline) visit were acquired with the TruTrac eye tracker using the progression scan function. The following scan acquisition parameters were used for Cirrus: (1) macular cube 512128 scan (66-mm square grid) with 128 horizontal B-scan lines each composed of 512 A-scans; (2) 5-line raster scan with 5 horizontal B-scans where each line scan is 6 mm in length and spaced 250 mm apart. Images were graded, with manual correction of algorithms and grid alignment if required, using the Heidelberg Eye Explorer 1.9.10.0, HRA/Spectralis Viewing Module 6.0.9.0 for SD OCT, and Cirrus HD-OCT Review Software 6.5.0.772 for high-definition optical coherence tomography at the Johns Hopkins University Retinal Imaging Research and Reading Center (Baltimore, MD). Resolution of edema at the week 12 primary end point was defined as a CST of 300 mm for Spectralis scans and 282 mm for Cirrus scans. The
difference of 18 mm between Spectralis and Cirrus is the mean of the reported differences of 17 and 19.2 mm.26,27 Excess foveal thickness was determined by subtracting 300 mm from Spectralis scan values and 282 mm from Cirrus scan values.
Fundus Photography and Fluorescein Angiography Modified 7 standard field fundus photographs and a fluorescein angiogram were obtained for both eyes using a 30 fundus camera at the screening and week 12 visits. In addition, fundus photographs were acquired at the week 20 visit. Fundus photographs and a fluorescein angiogram were graded for DRSS by the Digital Angiography Reading Center (New York, NY) using the ETDRS protocol.28
Pharmacokinetic Analysis Plasma samples were obtained 30 and 90 minutes after the first dose of AKB-9778, and levels of AKB-9778 were measured at a central laboratory using a validated liquid chromatographyemass spectrometry and liquid chromatographyetandem mass spectrometry method.
Statistical Analysis Sample size was selected on the basis of published data for ranibizumab and the previous phase Ib study of AKB-9778.24 With 40 subjects in the AKB-9778 monotherapy group, the study has 83.7% power to demonstrate a statistically significant reduction from baseline in CST, assuming that the true mean reduction from baseline is 55 mm with an estimated standard deviation of 130 mm using a 1-sample 1-sided test with a significance level of 0.05. Statistical analyses were performed on a modified intent-to-treat population that included all randomized patients who had at least 1 assessment after treatment. For analysis of data obtained during the 3-month treatment period, the last observation was carried forward for patients who did not complete the study. Change from baseline measurements within treatment groups and comparisons between treatment groups were made using a 1-way analysis of covariance with the baseline value as the covariate. The independent samples t test was used for comparisons made between any 2 groups for parametric variables, and the ManneWhitney test was used for nonparametric variables. Categoric variables were compared using the chi-square test. A criterion significance level of <0.05 was used. No correction for multiple comparisons was used.
Results Subject Disposition A total of 144 subjects with clinically significant DME and CST >325 mm were enrolled. A total of 93% of subjects (134/144) completed the 12-week active treatment period: 43 subjects (89.6%) in the AKB-9778 monotherapy group, 44 subjects (93.6%) in the ranibizumab monotherapy group, and 47 subjects (95.9%) in the combination group. Of the 134 subjects who remained in the trial through the 12-week primary end point, compliance with subcutaneous study medication dosing was 97.8% across all subjects, with compliance among the treatment groups ranging from 97.0% for the combination group to 98.3% for the ranibizumab monotherapy group. The prespecified population for the primary and secondary efficacy outcome analysis was the modified intent-to-treat population, defined as subjects who had efficacy data collected after initiation of dosing and consisted of 141 subjects: 46 in the AKB-9778 monotherapy
3
Ophthalmology Volume -, Number -, Month 2016 group, 47 in the ranibizumab monotherapy group, and 48 in the combination group. The last observation was carried forward to week 12.
Subject Demographics and Baseline Characteristics The average age at enrollment was 61.3 years and similar among treatment groups (Table 1). The subject population differs from most other interventional trials for DME in that the mean duration of DME was 5 to 6 years and the majority of subjects, approximately 60%, had been previously treated with anti-VEGF intraocular injections. The mean baseline BCVA in ETDRS letter score was approximately 60 (20/63 Snellen equivalent) in each of the treatment groups, and mean CST was well balanced, ranging from 465.0 to 504.4 mm.
Anatomic Outcomes There was no reduction in mean CST at week 12 in subjects treated with AKB-9778 monotherapy. Although 10.9% of subjects in the AKB-9778 monotherapy group showed 50% reduction in excess foveal thickness, some subjects showed increased CST, so overall there was no mean change. The mean reduction (standard error of the mean) from baseline CST was 164.424.2 mm in the combination group versus 110.417.2 mm in the ranibizumab monotherapy group (P ¼ 0.008 by analysis of covariance with baseline CST as the covariate) (Fig 1). Observed data for those subjects completing through week 12 were similar; the mean reduction (standard error of the mean) from baseline CST was 168.924.3 mm in the combination group versus 106.717.8 mm in the ranibizumab monotherapy group (P ¼ 0.008). Figure 2 is a waterfall plot in which the bars show the change from baseline CST for each study eye in the combination group (orange) and the ranibizumab monotherapy group (blue). As can be seen, more subjects in the combination group had large reductions in CST. The mean CST at week 12 was 340.011.2 mm, with 29.2% of eyes with resolved edema, in the combination group versus 392.117.1 mm (P ¼ 0.03), with 17.0% (P ¼ 0.22) of eyes with resolved edema, in the ranibizumab monotherapy group. In the combination group, 70.8% of patients had a reduction of excess foveal thickness of 50% compared with 55.3% (P ¼ 0.14) of patients treated with ranibizumab monotherapy.
Figure 1. Mean change in central subfield thickness (CST) as a function of time for each treatment group. Vertical bars represent the standard error of the mean. *Statistical comparison between combination and ranibizumab (RBZ) groups at that time point by analysis of covariance, with baseline CST as the covariate.
Visual Acuity Outcomes The mean change from baseline BCVA at week 12 was 1.51.2 letters in the AKB-9778 monotherapy group, 5.71.2 letters in the ranibizumab monotherapy group, and 6.31.3 letters in the combination group (Table 2) (P ¼ 0.74 for the difference between the ranibizumab group vs. the combination group). The percentage of eyes that gained 10 letters was 8.7% in the AKB-9778 monotherapy group, 29.8% in the ranibizumab monotherapy group, and 35.4% in the combination group (P ¼ 0.66 for ranibizumab group vs. combination group). An improvement of 15 letters was observed in 4.3%, 17.0%, and 20.8% in the AKB-9778 monotherapy, ranibizumab monotherapy, and combination groups, respectively (P ¼ 0.79 for ranibizumab group vs. combination group).
Effect on Background Diabetic Retinopathy The severity of diabetic retinopathy was analyzed in eyes with nonproliferative diabetic retinopathy (DRSS grade <7). At baseline, the mean DRSS was similar among treatment groups: 4.80.17, 4.70.18, and 4.80.18 for the AKB-9778 monotherapy, ranibizumab monotherapy, and combination groups,
Table 1. Demographics and Baseline Characteristics of Subjects in the Efficacy Population AKB-9778 Monotherapy (n [ 46) Age (yrs), mean SEM Female sex, n (%) Race, n (%) White African American Others Subjects with prior anti-VEGF, n (%) Type of diabetes, n (%) Type I DM Type II DM BCVA (letters), mean SEM (Snellen equivalent) CST (mm), mean SEM
61.31.1 22 (47.8) 40 (87.0) 5 (10.9) 1 (2.1) 26 (56.5) (n ¼ 45) 3 (6.7) 42 (93.3) 61.22.1 (20/63) 465.016.9
Ranibizumab Monotherapy (n [ 47) 61.21.3 14 (29.8) 41 (87.2) 3 (6.4) 3 (6.4) 32 (68.1) (n ¼ 45) 5 (11.1) 40 (88.9) 59.22.0 (20/63) 502.420.1
AKB-9778 Combination (n [ 48) 61.31.3 23 (47.9) 41 (85.4) 4 (8.3) 3 (6.3) 27 (56.3) (n ¼ 46) 9 (19.6) 37 (80.4) 60.31.8 (20/63) 504.420.3
P Value 0.99 0.12 0.64
0.43 0.19
0.77 0.30
BCVA ¼ best-corrected visual acuity; CST ¼ central subfield thickness; DM ¼ diabetes mellitus; SEM ¼ standard error of the mean; VEGF ¼ vascular endothelial growth factor.
4
Campochiaro et al
Benefit of Tie2 Activation in DME
Figure 2. Waterfall plot of individual subject change in central subfield thickness (CST) for AKB-9778 combination therapy subjects and ranibizumab monotherapy subjects. Each bar represents an individual subject. For each group, subjects are ordered from largest increase in CST to largest decrease in CST.
respectively. The percentage of subjects with a 2-step improvement in DRSS in the study eye between screening and week 12 was similar among the 3 groups (Fig 3). In the ranibizumab monotherapy group, 24 of 47 fellow eyes had background diabetic retinopathy that was not treated with local VEGF suppression or systemic AKB-9778, and 4.2% of these eyes showed 2-step improvement in DRSS. In the AKB-9778 monotherapy and combination groups, 70 of 94 fellow eyes had background diabetic retinopathy, and 11.4% of these eyes showed 2-step improvement in DRSS (P ¼ 0.149 for fellow eyes of patients who received AKB-9778 vs. fellow eyes of patients who received no AKB-9778).
Safety and Tolerability AKB-9778 was generally well tolerated. The incidence of AEs by treatment group is shown in Table 3. Of the 528 AEs reported in the study, the majority were considered mild or moderate in severity. Twelve subjects had severe AEs (AKB-9778 monotherapy, 2; ranibizumab monotherapy, 5; AKB-9778 combination, 5). No deaths were reported in the study, and of the 6 serious AEs (2 noncardiac chest pain, 1 dizziness and dehydration, 1 toe amputation, 1 hyperglycemia, and 1 pneumonia), none were considered related to the study medication. Five subjects withdrew from active treatment because of an AE (1 urticaria, 1 worsening of DME, 1 worsening of congestive heart failure, 1 third nerve palsy, 1 noncardiac chest pain). The most common ocular AEs were worsening of DME, worsening visual acuity, and vitreous floaters (Table 4). The majority of the worsening of DME events occurred during the observation period or in the fellow eye. Ocular AEs were evenly distributed between treatment groups. The most commonly reported nonocular AEs were dizziness, nausea, fatigue, vomiting, and cough (Table 5). Among the AKB-9778 Table 2. Comparison of Visual Outcomes at Month 3 for Subjects in the Efficacy Population AKB-9778 Ranibizumab AKB-9778 Monotherapy Monotherapy Combination (n [ 46) (n [ 47) (n [ 48) Mean change in BCVA from BL, letters 2 lines, % of subjects 3 lines, % of subjects
1.5
5.7
6.3
8.7 4.3
29.8 17.0
35.4 20.8
BCVA ¼ best corrected visual acuity; BL ¼ baseline.
monotherapy and combination group subjects, AEs of dizziness and fatigue tended to occur more frequently (16.5% and 10.3%, respectively) than in the ranibizumab monotherapy subjects (8.5% and 4.3%, respectively). Twenty-two of the 29 events (75.8%) were considered mild, and the remaining 7 events were moderate in intensity. Fourteen of these events had a duration of less than 7 days, and an additional 8 events were characterized as transient, occurring after subcutaneous dosing. The remaining 7 events were chronic (6 mild dizziness, 1 moderate dizziness, 2 mild fatigue). Two of these chronic events resolved despite continued dosing, 2 resolved at the end of the treatment period, and 3 continued through the observation period. No AEs in these categories resulted in subject withdrawal from treatment. Asymptomatic reductions in blood pressure occurred after the first dose of AKB-9778. Mean systolic blood pressure while sitting was reduced by 10.0 mmHg at 30 minutes and 9.2 mmHg at 90 minutes in AKB-9778-treated subjects from a mean baseline systolic blood pressure of 138.4 mmHg, compared with an increase of 2.2 mmHg at 30 minutes and a decrease of 0.1 mmHg at 90 minutes after sham subcutaneous injection in the ranibizumab monotherapy group with a mean baseline systolic blood pressure of 142.2 mmHg. The change from mean baseline systolic blood pressure at the end of 12 weeks of treatment was similar between AKB-9778-treated subjects (0.8 mmHg) and ranibizumab monotherapy subjects (þ0.8 mmHg). AKB-9778 did not increase orthostatic blood pressure changes.
Discussion Tie2 activation renders endothelial cells less responsive to pro-angiogenic and pro-permeability factors, promoting vascular stability. This is a critical function that requires tight regulation that is achieved through titration of an endogenous full agonist, angiopoietin 1, and an endogenous weak partial agonist, angiopoietin 2; and regulation of an endothelial tyrosine phosphatase, VE-PTP. Hypoxia increases the expression of both angiopoietin 2 and VE-PTP, which collaborate to limit Tie2 activation and downstream signaling, creating a permissive environment for VEGFmediated vascular leakage and neovascularization. Inhibition of VE-PTP restores Tie2 activation, even in the presence of excess angiopoietin 2, providing an appealing strategy to treat DME and other retinal vascular diseases. AKB-9778 is a small-molecule inhibitor of VE-PTP that suppresses VEGF-induced vascular leakage and enhances vascular stability.23,29 In this study, 11% of DME subjects treated with BID subcutaneous injections of 15 mg AKB9778 as monotherapy for 12 weeks showed a 50% reduction of excess foveal thickness; however, the majority of subjects showed no effect, and there was no reduction from mean baseline CST. Although further dose ranging may reveal greater efficacy, these results indicate that monotherapy with AKB-9778 15 mg BID is not a viable approach to treat DME. The combination of subcutaneous injections of AKB9778 and monthly intraocular injections of 0.3 mg of ranibizumab resulted in a significantly greater reduction in macular edema than monthly ranibizumab monotherapy. Compared with 17% of study eyes in the ranibizumab monotherapy group, 29% in the combination group had resolution of edema. The final mean CST of 340.0 mm in the
5
Ophthalmology Volume -, Number -, Month 2016
Figure 3. Percentage of study eyes (left) and fellow eyes (right) with nonproliferative diabetic retinopathy at baseline that had a 2-step improvement in Diabetic Retinopathy Severity Score after 3 months of treatment. For study eyes, results are displayed for eyes treated with AKB-9778 monotherapy, ranibizumab (RBZ) monotherapy, or AKB-9778 combination therapy. For fellow eyes, results are displayed for eyes treated with placebo or AKB-9778.
combination group indicates that, on average, there was little residual edema in subjects receiving combination therapy. Improvements in BCVA often lag behind improvements in CST, and therefore it was not surprising that statistically significant differences in visual outcome measures between treatment groups was not seen; nor was the study powered to detect significant differences. However, there were trends favoring better outcomes in the combination group, suggesting that longer and larger trials could potentially identify a significant visual benefit. There was no difference among the 3 treatment groups in the percentage of study eyes that showed a 2-step improvement in DRSS. Because 3 injections of ranibizumab
4 weeks apart have been shown to cause an improvement in DRSS,30 it is interesting that eyes of subjects treated with AKB-9778 alone had similar rates of DRSS improvement. Fellow eyes with diabetic retinopathy in the ranibizumab monotherapy group provide an untreated control group in which the percentage of eyes with 2step improvement in DRSS was 4.2% compared with 11.2% in fellow eyes with diabetic retinopathy of subjects who received systemic AKB-9778. Although the study was not powered to detect such a difference and it was not statistically significant, these data suggest that the vascular stabilizing effects of Tie2 activation with AKB9778 may promote improvement in background diabetic
Table 3. Overall Summary of Adverse Events: Safety Population Category Total reported AEs Ocular AEs Nonocular AEs Subjects with any AE Mild Moderate Severe Total reported treatment-related AEs Subjects with any treatment-related AE Mild Moderate Severe Serious AEs Subjects with any serious AE Subjects discontinued or withdrawn because of AE
AKB-9778 Monotherapy (N [ 48) 142 46 96 39 19 18 2 44 19 17 2 0 3 3 3
(93/49) (17/29) (76/20) (32/25) (18/15) (13/9) (1/1) (37/7) (17/5) (15/4) (2/1) (0/0) (2/1) (2/1) (3/0)
Ranibizumab Monotherapy (N [ 47) 177 67 110 36 16 15 5 44 11 7 3 1 0 0 1
(134/43) (45/22) (89/21) (34/17) (15/7) (14/9) (5/1) (44/0) (11/0) (7/0) (3/0) (1/0) (0/0) (0/0) (1/0)
AKB-9778 Combination (N [ 49) 209 79 130 43 21 17 5 51 21 12 7 2 3 3 1
(156/53) (48/31) (108/22) (39/24) (19/17) (17/5) (3/2) (47/4) (20/3) (12/0) (6/2) (1/1) (2/1) (2/1) (1/0)
AE ¼ adverse event. Data are total number (number in treatment period/number in observation period). N in the headers represents the total number of subjects enrolled in each respective treatment group within the safety population. Subjects experiencing >1 AE are counted once under the maximal severity for the summary by severity.
6
Campochiaro et al
Benefit of Tie2 Activation in DME
Table 4. Summary of Ocular Treatment-Emergent Adverse Events Reported in More Than 5% of All Subjects: Safety Population AKB-9778 Monotherapy (N [ 48) Adverse Event Diabetic retinal edema worse Treatment period Observation period Visual acuity reduced Treatment period Observation period Vitreous floaters Treatment period Observation period
Ranibizumab Monotherapy (N [ 47)
AKB-9778 Combination (N [ 49)
Events
Subjects
Events
Subjects
Events
Subjects
13 5 8 6 2 4 0 0 0
10 4 6 5 2 4 0 0 0
14 6 8 3 2 1 6 6 0
12 6 6 2 2 1 4 4 0
23 9 14 6 3 3 5 3 2
15 7 11 3 2 2 4 2 2
(5) (1) (4) (3) (2) (1) (0) (0) (0)
(5) (1) (4) (2) (2) (1) (0) (0) (0)
(7) (2) (5) (2) (1) (1) (3) (3) (0)
(7) (2) (5) (1) (1) (1) (3) (3) (0)
(8) (1) (7) (4) (2) (2) (4) (3) (1)
(8) (1) (7) (3) (2) (2) (3) (2) (1)
Data are total no. (no. in study eyes).
vasodilation.35 Activation of Tie2 stimulates endothelial NO synthase and elevates NO, which could counter the negative effects of systemic suppression of VEGF.36 Overexpression of angiopoietin 2 and Tie2 inactivation may contribute to other diabetic vascular complications, including diabetic nephropathy,37,38 and if this is the case, subcutaneous AKB-9778 could have additional advantages. Systemic exposure to AKB-9778 also could increase the chance of side effects. However, AKB-9778 demonstrated a favorable safety profile in this study. Only 4 of 97 patients (4.1%) discontinued study medication because of an AE, and all of these AEs were due to complications of diabetes mellitus rather than to the study drug. The overall incidence of AEs was similar between the treatment groups, but the incidence of dizziness and fatigue was increased in patients receiving AKB-9778 compared with those receiving ranibizumab monotherapy. All of the dizziness and fatigue AEs in AKB-9778 subjects were mild to moderate in intensity, and the majority of events occurred transiently after dosing. There were no by-treatment differences in serious AEs, severe AEs, physical examination findings, ophthalmology examination, or laboratory abnormalities. Studies of longer duration will further characterize the safety and tolerability of AKB-9778 in subjects with DME.
retinopathy. This notion is supported by the proposed role of reduced Tie2 signaling in the earliest stages of diabetic retinopathy31 and is consistent with the known effects of Tie2 activation reducing inflammation and vascular leakage, enhancing endothelial viability, and maintaining the normal investment of mature vessels with pericytes and smooth muscle cells.32 The potential beneficial effect of AKB-9778 on diabetic retinopathy deserves more detailed investigation in future trials. Delivery of AKB-9778 by subcutaneous injections allows for the potential advantage of patient self-administration. Systemic delivery of AKB-9778 has the additional advantage of treating both eyes in patients with bilateral DME, and when used in combination with intraocular injections of VEGF-neutralizing proteins, there is a theoretical benefit of protection from systemic vascular complications of VEGF suppression. Systemic exposure to high levels of a VEGF antagonist reduces activity of endothelial nitric oxide (NO) synthase and thus levels of NO, causing vasoconstriction and hypertension.33 The mechanism by which VEGF antagonists promote thrombosis or hemorrhage in regions of the vasculature with previously compromised endothelium is not completely clear,34 but NO reduction is thought to play a role because NO promotes endothelial cell viability and
Table 5. Summary of Nonocular Treatment-Emergent Adverse Events Reported in More Than 5% of All Subjects: Safety Population AKB-9778 Monotherapy (N [ 48) Adverse Event
Events, n
Dizziness Treatment period Observation period Nausea Treatment period Observation period Fatigue Treatment period Observation period Vomiting Treatment period Observation period Cough Treatment period Observation period
8 8 0 4 4 0 5 5 0 3 2 1 1 1 0
Subjects, n (%) 8 8 0 4 4 0 5 5 0 3 2 1 1 1 0
(16.7) (16.7) (0.0) (8.3) (8.3) (0.0) (10.4) (10.4) (0.0) (6.3) (4.2) (2.1) (2.1) (2.1) (0.0)
Ranibizumab Monotherapy (N [ 47) Events, n 6 6 0 6 5 1 2 2 0 4 3 1 3 2 1
Subjects, n (%) 4 4 0 3 3 1 2 2 0 2 1 1 3 2 1
(8.5) (8.5) (0.0) (6.4) (6.4) (2.1) (4.3) (4.3) (0.0) (4.3) (2.1) (2.1) (6.4) (4.3) (2.1)
AKB-9778 Combination (N [ 49) Events, n 9 9 0 7 7 0 5 5 0 4 4 0 4 3 1
Subjects, n (%) 8 8 0 7 7 0 5 5 0 3 3 0 4 3 1
(16.3) (16.3) (0.0) (14.3) (14.3) (0.0) (10.2) (10.2) (0.0) (6.1) (6.1) (0.0) (8.2) (6.1) (2.0)
7
Ophthalmology Volume -, Number -, Month 2016 In conclusion, this study showed that Tie2 activation by subcutaneously administered AKB-9778 in combination with anti-VEGF therapy is more effective than anti-VEGF therapy alone in reducing DME. This is the first demonstration of clinical benefit in a randomized, placebo-controlled trial of any therapy in combination with anti-VEGF in DME. Improvements in DRSS suggest that subcutaneous AKB-9778 monotherapy may be effective in the treatment of diabetic retinopathy in subjects with or without DME. Inhibition of VE-PTP with AKB-9778 restores Tie2 activation in the diseased retina and is an appealing strategy to treat diabetic eye disease and other retinal and choroidal vascular diseases.
References 1. Guariquata L, Whiting DR, Hambleton I, et al. Global estimates of diabetes prevalence for 2013 and projections for 2035. Diabetes Res Clin Pract 2014;103:137–49. 2. Yau JW, Rogers SL, Kawasaki R, et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care 2012;35:556–64. 3. Nguyen QD, Shah SM, Van Anden E, et al. Supplemental inspired oxygen improves diabetic macular edema; a pilot study. Invest Ophthalmol Vis Sci 2003;45:617–24. 4. Nguyen QD, Tatlipinar S, Shah SM, et al. Vascular endothelial growth factor is a critical stimulus for diabetic macular edema. Am J Ophthalmol 2006;142:961–9. 5. Nguyen QD, Shah SM, Heier JS, et al. Primary end point (six months) results of the Ranibizumab for Edema of the mAcula in Diabetes (READ-2) Study. Ophthalmology 2009;116: 2175–81. 6. Nguyen QD, Brown DM, Marcus DM, et al. Ranibizumab for diabetic macular edema. Results from 2 Phase III Randomized Trials: RISE and RIDE. Ophthalmology 2012;119:789–801. 7. Heier JS, Clark WL, Boyer DS, et al. Intravitreal aflibercept injection for macular edema due to central retinal vein occlusion: two-year results from the COPERNICUS study. Ophthalmology 2014;121:1414–20. 8. Korobelnik JF, Do DV, Schmidt-Erfurth U, et al. Intravitreal aflibercept for diabetic macular edema. Ophthalmology 2014;121:2247–54. 9. The Diabetic Retinopathy Clinical Research Network. Aflibercept, bevacizumab, or ranibizumab for diabetic macular edema. N Engl J Med 2015;372:1193–203. 10. Do DV, Nguyen QD, Khwaja AA, et al. Ranibizumab for edema of the macula in diabetes trial; 3-year outcomes and the need for prolonged frequent treatment. Arch Ophthalmol 2013;131:139–45. 11. Channa R, Sophie R, Khwaja AA, et al. Factors affecting visual outcomes in patients with diabetic macular edema treated with ranibizumab. Eye (Lond) 2013;28:269–78. 12. Wong AL, Haroon ZA, Werner S, et al. Tie2 expression and phosphorylation in angiogenic and quiescent adult tissues. Circ Res 1997;81:567–74. 13. Thurston G, Suri C, Smith K, et al. Leakage-resistant blood vessels in mice transgenically overexpressing angiopoietin-1. Science 1999;286:2511–5. 14. Thurston G, Rudge JS, Ioffe E, et al. Angiopoietin-1 protects the adult vasculature against plasma leakage. Nat Med 2000;6: 460–3.
8
15. Davis S, Aldrich TH, Jones P, et al. Isolation of angiopoietin1, a ligand for the TIE2 receptor, by secretion-trap expression cloning. Cell 1996;87:1161–9. 16. Maisonpierre PC, Suri C, Jones PF, et al. Angiopoietin-2, a natural antagonist for Tie2 that disrupts in vivo angiogenesis. Science 1997;277:55–60. 17. Yuan HT, Khankin EV, Karumanchi SA, Parikh SM. Angiopoietin 2 is a partial agonist/antagonist of Tie2 signaling in the endothelium. Mol Cell Biol 2009;29:2011–22. 18. Yacyshyn OK, Lai PFH, Forse K, et al. Tyrosine phosphatase beta regulates angiopoietin-Tie2 signaling in human endothelial cells. Angiogenesis 2009;12:25–33. 19. Hackett SF, Ozaki H, Strauss RW, et al. Angiopoietin 2 expression in the retina: upregulation during physiologic and pathologic neovascularization. J Cell Physiol 2000;184: 275–84. 20. Hackett SF, Wiegand SJ, Yancopoulos G, Campochiaro P. Angiopoietin-2 plays an important role in retinal angiogenesis. J Cell Physiol 2002;192:182–7. 21. Oshima Y, Deering T, Oshima S, et al. Angiopoietin-2 enhances retinal vessel sensitivity to vascular endothelial growth factor. J Cell Physiol 2004;199:412–7. 22. Oshima Y, Oshima S, Nambu H, et al. Different effects of angiopoietin 2 in different vascular beds in the eye; new vessels are most sensitive. FASEB J 2005;19:963–5. 23. Shen J, Frye M, Lee BL, et al. Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature. J Clin Invest 2014;124:4564–76. 24. Campochiaro PA, Sophie R, Tolentino M, et al. Treatment of diabetic macular edema with an inhibitor of vascular endothelial-protein tyrosine phosphatase that activates Tie2. Ophthalmology 2015;122:545–54. 25. The Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema. Early Treatment Diabetic Retinopathy Study report number 1. Arch Ophthalmol 1985;103:1796–806. 26. Lammer J, Scholda C, Prunte C, et al. Retinal thickness and volume measurements in diabetic macular edema: a comparison of four optical coherence tomography systems. Retina 2011;31:48–55. 27. Hatef E, Khwaja A, Rentiya Z, et al. Comparison of time domain and spectral-domain optical coherence tomography in measurement of macular thickness in macular edema secondary to diabetic retinopathy and retinal vein occlusion. J Ophthalmol 2012;2012:354783. 28. The Early Treatment Diabetic Retinopathy Study Research Group. Grading diabetic retinopathy from stereoscopic color fundus photographs-an extension of the modified Airlie House classification. ETDRS Report Number 10. Ophthalmology 1991;98(5 Suppl):786–806. 29. Goel S, Gupta N, Walcott BP, et al. Effects of vascularendothelial protein tyrosine phosphatase inhibition on breast cancer vasculature and metastatic progression. J Natl Cancer Inst 2013;105:1188–201. 30. Ip MS, Domalpally A, Hopkins JJ, et al. Long-term effects of ranibizumab on diabetic retinopathy severity and progression. Arch Ophthalmol 2012;130:1145–52. 31. Hammes H-P, Feng Y, Pfister F, Brownlee M. Diabetic retinopathy: targeting vasoregression. Diabetes 2011;60: 9–16. 32. Augustin HG, Koh GY, Thurston G, Alitalo K. Control of vascular morphogenesis and homeostasis through the angiopoietin-Tie system. Nat Rev Mol Cell Biol 2009;10: 165–77.
Campochiaro et al
Benefit of Tie2 Activation in DME
33. Robinson ES, Khankin EV, Choueiri TK, et al. Suppression of the nitric oxide pathway in metastatic renal cell carcinoma patients receiving vascular endothelial growth factor-signaling inhibitors. Hypertension 2010;56:1131–6. 34. Zuo P-Y, Chen X-L, Liu Y-W, et al. Increased risk of cerebrovascular events in patients with cancer treated with bevacizumab: a meta-analysis. PLoS One 2014;9:e102484. 35. Dimmeler S, Fleming I, Fisslthaler B, et al. Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation. Nature 1999;399:601–5.
36. Alfieri A, Ong AC, Kammerer RA, et al. Angiopoietin-1 regulates microvascular reactivity and protects the microcirculation during acute endothelial dysfunction: role of eNOS and VE-cadherin. Pharmacol Res 2014;80:43–51. 37. Davis B, Dei Cas A, Long DA, et al. Podocyte-specific expression of angiopoietin-2 causes proteinuria and apoptosis of glomerular endothelia. J Am Soc Nephrol 2007;18:2320–9. 38. Dei Cas A, Gnudi L. VEGF and angiopoietins in diabetic glomerulopathy: how far for a new treatment? Metabolism 2012;61:1666–73.
Footnotes and Financial Disclosures Originally received: January 18, 2016. Final revision: April 15, 2016. Accepted: April 15, 2016. Available online: ---. Manuscript no. 2016-116. 1 Johns Hopkins, Wilmer Eye Institute, Baltimore, Maryland.
S.P.: Grants e Alcon, Ophthotech, Genentech, Allergan, Regeneron.
2
Sierra Eye Associates, Reno, Nevada.
D.B.: Consultant e Aerpio Therapeutics, Alcon, Allegro, Allergan, Bausch & Lomb, Bayer, CoDa Therapeutics, ForeSight Biotherapeutics, Erigen Inc., Genentech, GlaxoSmithKline, Neurotech, Notal Vision, Novartis Ophthalmics, Ophthotech, Ohr, Optos, Regeneron, RetroSense Therapeutics, Sun Pharmaceuticals, Stem Cells Inc., ThromboGenics.
3
Medical Center Ophthalmology Associates, San Antonio, Texas.
B.W., L.G., K.P., M.B.: Employees e Aerpio Therapeutics.
4
Retina Research Institute of Texas, Abilene, Texas.
This study was funded by Aerpio Therapeutics, Cincinnati, Ohio.
5
Retina Vitreous Associates Medical Group, Beverly Hills, California.
Author Contributions:
6
Retinal Consultants of Arizona, Phoenix, Arizona.
Conception and design: Campochiaro, Withers, Gambino, Peters, Brigell
7
USC Eye Institute, Keck School of Medicine, University of Southern California, Los Angeles, California.
8
Aerpio Therapeutics, Cincinnati, Ohio.
Data collection: Campochiaro, Khanani, Singer, Patel, Boyer, Dugel, Kherani Analysis and interpretation: Campochiaro, Kherani, Withers, Gambino, Peters, Brigell
Members of the TIME-2 study group are listed in the Appendix (available at www.aaojournal.org).
Obtained funding: Not applicable
Financial Disclosure(s): The author(s) have made the following disclosure(s): P.A.C.: Consultant e Aerpio Therapeutics, Alimera, Applied Genetic Technologies, Eleven Biotherapeutics, AsclipiX, Genentech/Roche, Kala Pharmaceuticals, Rxi Pharmaceuticals, Akebia, Regeneron, Allegro, Intrexon, RegenX; Institutional grants e AbbVie, Aerpio Therapeutics, Allergan, Genentech/Roche, Genzyme, GlaxoSmithKline, Oxford Biomedica, Regeneron, RegenX, Rxi Pharmaceuticals; Royalties e Graybug; Equity e Alimera, Allegro, Graybug.
Abbreviations and Acronyms: AE ¼ adverse event; BCVA ¼ best-corrected visual acuity; BID ¼ twice per day; CST ¼ central subfield thickness; DME ¼ diabetic macular edema; DRSS ¼ Diabetic Retinopathy Severity Score; ETDRS ¼ Early Treatment Diabetic Retinopathy Study; NO ¼ nitric oxide; SD OCT ¼ spectral-domain optical coherence tomography; Tie2 ¼ tyrosine kinase with immunoglobulin-like and epidermal growth factorelike domains 2; VEGF ¼ vascular endothelial growth factor; VE-PTP ¼ vascular endothelial-protein tyrosine phosphatase.
A.K.: Grants e Aerpio Therapeutics, Genentech; Personal fees e Genentech, Novartis, Allergan; Nonfinancial support e Genentech, Novartis. M.S.: Research support and personal fees (Advisory Committee) e Aerpio Therapeutics; Consultant e Genentech, Allergan; Grants Regeneron, Ampio, Allegro, Stem Cells Inc., Acucela, Optos, Neurotech.
Overall responsibility: Campochiaro, Kherani, Withers, Gambino, Brigell
Correspondence: Peter A. Campochiaro, MD, Maumenee 815, The Wilmer Eye Institute, Johns Hopkins University, 600 N. Wolfe Street, Baltimore, MD 21287. E-mail: [email protected].
9