The efficacy and safety of topical diquafosol ophthalmic solution for the treatment of dry eye: A systematic review of randomized clinical trials
Di Wu1,4, PhD, Wang Qi Chen2, Ryan Li3, Yan Wang4, MD, PhD
1 Tianjin Medical University. 22 Qixiangtai Rd, Heping, Tianjin, China, 300070
2 University of California, Berkeley, College of Chemistry. 419 Latimer Hall, Berkeley, CA 94720
3 University of Toronto, Faculty of Arts and Science. Sidney Smith Hall, 100 St. George Street Toronto, Ontario, Canada M5S 3G3
4 Tianjin Eye Hospital & Eye Institute, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Medical University. No 4. Gansu Rd, Heping District, Tianjin, China, 300020
Corresponding author: Yan Wang, MD, PhD. Tianjin Eye Hospital & Eye Institute, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Medical University. No 4. Gansu Rd, Heping District, Tianjin, China, 300020 Tel: 86-22-27305083. Email:
None of the authors has a financial interest related to this study.
Keywords: diquafosol, dry eye, keratoconjunctivitis sicca, randomized clinical trials, systematic review
Purpose: To evaluate the efficacy and safety of topical diquafosol ophthalmic solution treatment for dry eye.
Methods: Randomized clinical trials (RCTs) from MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were identified to evaluate the efficacy and safety of topical administration of diquafosol for dry eye patientsents. Data evaluation was based on endpoints including Schirmer’s test, tear film break-up time test (TFBUT), ocular surface staining score, subjective symptom score and adverse events.
Results: A total of 8 RCTs involving 1516 patients were selected abiding pre-specified criteria. Significant improvement of Schirmer’s test values and TFBUT were reported in 40% (2/5) and 80% (4/5) studies, respectively. Ocular surface staining scores significantly decreased in 100% (Fluorescein corneal staining: 6/6; Rose Bengal corneal and conjunctival staining: 4/4) RCTs. Symptoms significantly improved in 75% (6/8) RCTs in dry eye patients. No severe adverse events were reported with the concentrations of diquafosol from 0.5% - 5%. Heterogeneity in study design prevented meta-analysis from statistical integration and summarization.
Conclusions: Topical diquafosol appears to be a safe therapeutic option for the treatment of dry eye. The high variability of the selected RCTs compromised the strength of evidence and limits the determination of efficacy. However, the topical administration of diquafosol showed appears to be beneficial in improving the integrity of the epithelial cell layer of ocular surface and mucin secretion in dry eye patients. This review indicates a need for standardized criteria and methods for evaluation to assess the efficacy of diquafosol in the future clinical trials.
INTRODUCTION
Dry eye or keratoconjunctivitis sicca (KCS) is a multifactorial disease characterized by increased osmolarity of the tear film and inflammation of the ocular surface.1 Based on population-based epidemiologic studies, The International Dry Eye Workshop (2007) reported the prevalence of dry eye to be a range of approximately 5%-35% at various ages.2-9 Furthermore, tAside from the disturbance of vision function, the burden of dry eye also may include the impact on daily activities, social and physical functioning, and quality of life.10
The pathogenesis of dry eye is a cyclic amplification of the damage and discomfort associated with the disease. The cascade of inflammatory events in dry eye caused by tTear hyperosmolarity and tear film instability have been regarded as the causative and core mechanism causing ocular surface damage, symptoms of discomfort and a cascade of inflammatory events in dry eye.1 The activation of inflammatory signaling pathways (e.g., MAP kinases and NFκB) and the release of inflammatory cytokines elicits apoptotic death of surface epithelial cells, including the goblet cells (GCs).11-13 GCs secrete gel-forming mucin that plays an essential role in maintaining the integrity of the tear film.14,15 The reduction of GCs leads to a corresponding reduction of mucin, which exacerbates tear film instability and ocular surface hyperosmolarity, triggering the progression of dry eye into a vicious cycle. Therefore, increasing mucin secretion is would be an important therapeutic target in dry eye syndrome in an effort to break from this cycle.
Diquafosol, a pharmacological agent under investigation, has been known as a purinergic P2Y2 receptor agonist that promotes fluid transfer and mucin secretion by activating P2Y2 receptors expressed on ocular surface.16,17-20 Previous studies have shown that the stimulation of water and mucin secretion by diquafosol is related to the activation of phospholipase C via G proteins caused by the combination of diquafolsol and P2Y2 receptor, which consequently increases the concentration of calcium ion within conjunctival epithelial cells and in GCs.19,21 Animal in vivo studies, conducted on dogs, rabbits, or age-related dry eye murine model, demonstrated that the topical administration of diquafosol appeared to be effective in improving mucin MUC5AC concentration and aqueous tear secretion.22-24
Even though tThere is evidence demonstrating the improvement of aqueous tear secretion in animal models22-24, but, no consensus on the efficacy of diquafosol as a clinical therapy for dry eye has been established. Diquafosol ophthalmic solution was approved in Japan in April 2010 as a novel therapeutic option for dry eye, but it has not yet been accepted by United States Food and Drug Administration (FDA).25 So far, several randomized clinical trials (RCTs) have been performed concerning diquafosol and dry eye. To our knowledge, there has been no reported systematic review or meta-analysis to provide recommendations to evaluate the treatment effects of diquafosol for dry eye. This present report aimed to systematically review the results of RCTs on safety and efficacy of diquafosol ophthalmic solution in different dry eye types.
MATERIALS AND METHODS
This review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).26 A previously written protocol can be found in the Appendix 1. The details of the protocol abide the recommendations from Cochrane Handbook for Systematic Reviews of Interventions (Cochrane Handbook).27
Eligibility Criteria
Types of Studies: RCTs studying the effect of diquafosol administration as an ophthalmic solution for dry eye disease.
Types of Participants: Male or female participants of any age ≥18 with either subjective or objective diagnosis of dry eye were considered. Methods of diagnosis can be tear film break-up time (TFBUT) test, ocular surface staining, symptoms of ocular dryness, and/or Schirmer’s test.
Types of Intervention: Topical diquafosol administration as an ophthalmic solution of any vehicles, dose and regiments were included.
Types of Outcome: Clinical outcomes including symptom score, ocular surface staining score, TFBUT, Schirmer’s test, and adverse events.
Literature Search
The Cochrane highly sensitive search strategy was applied to MEDLINE (1966-2014), EMBASE (1980-2014), and Cochrane Central Register of Controlled Trials (CENTRAL, the Cochrane Library, Issue 9, 2014) database, with language restriction to English, Chinese, and French. The initial electronic database search was conducted on July 21st 2014, using the following terms to search all databases and registers: diquafosol; diquafosol tetrasodium; diquafosol sodium; P2Y2 agonist, P2Y2; dry eye; Sjögren syndrome; keratoconjunctivitis; keratoconjunctivitis sicca. The search strategy is available in the Appendix 2. Two authors (Wu, D; Chen, W) conducted the search independently. In addition, all references of included studies and those of published relevant reviews278, 289 wereare hand searched.
Study Selection
The study selection process was independently completed by two authors (Wu, D; Chen, W) independently. All titles and abstracts identified from the search strategy were scanned and reports that were apparently either notneither about diquafosol, norot randomized, nor desired they had no associated clinical outcomes were excluded. After an initial screening, Ffull texts of potentially eligible studies were obtained and verified inclusion using a prior constructed eligibility form. Disagreements were resolved by discussion.
Data Extraction
A data extraction sheet based on “Checklist of items to consider in data collection or data extraction” from Cochrane Handbook, pilot-tested it on 3 randomly selected included studies and refined accordingly.2930 The following data from included studies were extracted: risk of bias items, study design, characteristics of participants (total number, age, sex, diagnostic criteria, country), type of intervention (duration, regimen, concentration), and type of outcome measures (including outcomes listed in the eligibility of criteria, missing participants, and length of follow up). Any unclear or absence of information was confirmed with original investigators.
Risk of Bias in Individual Studies
Risk of Bias was assessed based on the ‘Risk of bias’ tool described in Handbook (Version 5.1.0).3031 To determine the validity of eligible randomized trials, an assessment of the adequacy of sequence randomization, concealment of allocation, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting and ‘other issues’ was completed. The bias was defined as high risk, low risk, or unclear provided by criteria defined in the Cochrane Handbook for evaluating risk of bias.
Summary Mmeasures
The primary outcome of this systematic review was the evaluation of the efficacy of topical diquafosol treatment on dry eye by tear function tests (Schirmer’s test and TFBUT test). Secondary outcomes of this study included: ocular surface staining score (fluorescein or Rose Bengal staining), subjective symptom score; and safety parameters (ocular and systemic adverse events).
Statistical analysis
All selected information was subjected to analysis by RevMan 5 (Review Manager Version 5.2, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2012). A chi-squared test evaluated statistical heterogeneity between studies, with significant heterogeneity (P<0.05) ceasing meta-analysis
RESULT
Due to the presence of between-study heterogeneity induced by the variation of comparison, follow-up time points, and diquafosol concentrations for evaluating different outcome measures, it is inappropriate to report these outcomes in conjunction with meta-analysis. As an alternative, data yielded from included RCTs were subjected to descriptive analysis.
Study Selection
Of 375 potentially relevant citations identified from electronic databases (23 from MEDLINE, 89 from EMBASE, and 19 from CENTRAL), and hand searches (244 from all references of included studies and previous relevant reviews), 31 articles were retrieved for full-text review after adjusting for duplicates and titles and abstracts screening. A Selectively, a total of 8 RCTs were included in this systematic review.312-389 DThe details of the selection process are given in Figure1.
Study Characteristics
Table 1 shows the characteristics of the 8 included studies that dated from 2001 to 2014. All 8 studies (see Table 1) selected for the review were RCTs published in English. Seven of which were full text312-378 and one was conference abstract389. A total of four trials were performed in Japan,312,334,345,367 three in America,323,378,389 and one in Korea.356 Two studies were conducted following two trials each.334, 378 One study included a RCT and a non-RCT.334 Only the RCT was enrolled in this review. The other study comprising of with two trials evaluated the safety of diquafosol and its efficacy separately.378
Methods:
In all, there were five multicenter studies.32,33,35,37,39 Of the eight studies, four specified the washout period before the randomization with a mean washout period from previous treatments of 1.5±0.58 weeks. The mean follow-up time was 1.94±1.94 months.32,33,35,39 (Table 1)
Participants:
The included studies involved 1516 patients with dry eye. Mean age was 59.87 (range: 36.7 - 65.3) years old, and 73.0% were female (see Table 2). All studies included provided specified criteria of dry eye diagnosis. Four studies evaluated diquafosol efficacy in specific dry eye populations: one study included patients with short BUT type of dry eye (eyes with Schirmer values ≤ 5 mm were excluded),334, one study included patients with aqueous-tear deficient dry eye but not evaporative dry eye,356 one study included patients with dry eye refractory to sodium hyaluronate monotherapy,-37 and one study enrolled patients with mild-to-moderate dry eye.378 (see Table 2). In the remaining 4 studies, type or severity of DED of enrolled patients was not specified.
Intervention:
Of the 8 included studies, one study recruited 32 patients and tested topical diquafosol in 1 randomly selected eye, and the other eye was assigned as control.367 Three studies enrolled 286, 150 and 17 patients respectively, and only one eye from each patient was selected into study. 312,334,356 However, Nno explicit explanation relating to the selection of two eyes was documented. Two studies that recruited 286 and 158 patients remained unclear in the number of eyes included in trials.345,389 In the remaining 2 studies (three trials), 527 and 60 enrolled patients were grouped respectively and randomly to receive either topical diquafosol in both eyes, or placebo in both eyes.323,378
Different concentrations of diquafosol were evaluated in the 8 studies included in this systematic review with a range from 0.5% to 5%. Detailed information of regimen can be found in Table 1.
Outcomes:
All studies included in this systematic review evaluated efficacy of diquafosol ophthalmic solution primarily using Schirmer I test (without anesthesia, in 5 studies33,34,36-38), Shirmer II test (with anesthesia, in 1 study38), TFBUT (in 5 studies32,34-37), ocular surface staining (in 7 studies32-37,39), and symptom score (in 7 studies32-37,39). Five studies evaluated adverse events.32,33,35,37,38
Risk of Bias Within Studies
The outcome of ‘Risk of Bias’ assessment is summarized in Figure 2. In terms of selection bias, four of the eight RCTs specified the methods of random sequence generation.334-367 Two studies provided the method of allocation concealment.334,367 Regarding performance biases (blinding of participants and personnel), four of the eight included studies were double masked,312,323,345,378 and two were open-label study design,334,356 which were judged as high risk in both performance bias and detection bias. Among the eight included RCTs, six were judged as low risk of attrition bias because the dropouts patients’ number werewas reported clearly and the percentages werewas believed unlikely to affect the outcome.312-367 Six RCTs included in this systematic review were judged to be free from reporting bias, as all of the studies’ pre-specified outcomes were addressed in result.312,334-378 One However, one study didn’t report the result of TFBUT, which was addressed as an endpoint for efficacy assessment in methodologies.323 For the only one conference abstract enrolled in this review, there was no sufficient information to assess the risk of bias within study.
Outcome of Efficacy
Schirmer I/II Test
Schirmer’s test is a method of assessment indicative of volume tear fluid secretion. In the result of the included studies, two out of five studies showed significant improvement.323,356 (Table 3) Hwuang356 reported improvement in both monotherapy and in combination (diquafosol/ sodium hyaluronate) throughout a three months period from 1.12 to 3.27mm(/5min). Tauber323 reported of the subjects with intermediate or high tear volume in diquafosol (1%, 2%) treatment group was significantly higher than placebo group at six weeks. The other three studied showed no significant improvement compared with baseline values.334,367,378 No significant improvement reported from Schirmer II test assessed.378