Antisense oligonucleotides (ASOs) bind sequence specifically to the target RNA and modulate protein expression through several different mechanisms. The ASO field is an emerging area of drug development that targets the disease source at the RNA level and offers a promising alternative to therapies targeting downstream processes. To translate ASO-based therapies into a clinical success, it is crucial to overcome the challenges associated with off-target side effects and insufficient biological activity. In this regard, several chemical modifications and diverse delivery strategies have been explored. In this review, we systematically discuss the chemical modifications, mechanism of action, and optimized delivery strategies of several different classes of ASOs. Further, we highlight the recent advances made in development of ASO-based drugs with a focus on drugs that are approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for clinical applications. We also discuss various promising ASO-based drug candidates in the clinical trials, and the outstanding opportunity of emerging microRNA as a viable therapeutic target for future ASO-based therapies. Aberrant protein production or metabolism is associated with numerous devastating diseases and disorders ,2,3,4. AIn prior studies, ASOs based on phosphodiester backbone  were used to target RNA with moderate success. However, due to the presence of a phosphodiester bond, unmodified ASOs are susceptible to nuclease degradation . In addi−1 dose of PS-ASOs revealed 40% excretion in urine in 48 h . RN. RN46]. Exogenous small interfering RNAs (siRNAs) are double-stranded 22 nucleotide RNA sequences with a 2-nucleotide overhang on the 3′ end of either strand . This seThese classes of ASOs bind to target RNA sequence and cause translational arrest by inhibiting their interaction with the 40S ribosomal subunit or preventing their assembly on the 40S or 60S ribosomal subunit  53,54].,54.53,54ASOs can also exert their effects by alternative splicing ,58,59. SWhile delivery of ASOs has always been a significant hurdle for their broad clinical applications, various strategies have been employed to deliver them ,68,69.Alnylam extensively used enhanced stabilization chemistry (ESC) to deliver siRNA. In ESC, siRNAs are conjugated to N-Acetyl galactosamine  . GalNac Numerous polymeric nanoparticle-based delivery systems like PLGA, PBAE, and PEI have been used to deliver ASOs ,73. PBAESeveral lipid-based delivery systems, lipoplexes, liposomes, and lipid nanoparticles (LNP) have been extensively used to deliver ASOs and siRNAs ,78. LNPsIn 1998, Fomivirsen was the first ASO-based drug developed by Ionis Pharmaceuticals. Fomivirsen received approval by the United States FDA for the treatment of retinitis caused by opportunistic cytomegalovirus (CMV) infection in immunocompromised AIDS patients . CMV infHomozygous familial hypercholesterolemia (HoFH) is an autosomal dominant genetic disorder that results in elevated low-density lipoprotein (LDL) levels. HoFH is caused by a mutation in the gene for LDL cholesterol receptor or pro-protein convertase subtilisin/kexin 9 (PCSK9) or apolipoprotein B (apo B) . The eleSpinal muscular atrophy (SMA) is a genetic and autosomal recessive motor neuron disease caused by a homozygous deletion in the survival motor neuron 1 (SMN1) on chromosome 5q13 . The SMN−1 [Transthyretin (TTR) is a tetrameric protein involved in the transport of thyroxin and retinol-binding protein vitamin A complex . In heal−1 . Three a−1 ,101,102.Inotersen was developed by Ionis Pharmaceuticals for hATTR treatment in 2018. Inotersen consists of gapmer design with five 2′-O-MOE nucleotides present at 5′ and 3′ ends with PS modifications present throughout the sequence. The 2′-O-MOE modification increases the ASO binding with the TTR mRNA without affecting its antisense activity. In a randomized, double-blinded placebo-controlled phase III clinical study, the safety and efficacy of subcutaneously administered Inotersen was evaluated in 112 patients and compared with 60 patients in a placebo group for 66 weeks. Composite scores based on the modified Neuropathy Impairment Score +7 (mNIS+7) and total score on the Norfolk Quality of Life-Diabetic Neuropathy (QOL-DN) questionnaire were the primary endpoints of the above-mentioned clinical study. In general, High mNIS+7 corresponds to inadequate response to therapy, and a high score on Norfolk QOL-DN is a measure of poor quality of life. The difference in the least-squares mean change from baseline to week 66 between the Inotersen and placebo-treated groups, which was −19.7 points for mNIS+7 and −11.7 points for the Norfolk QOL-DN, indicates the potential clinical efficacy of Inotersen. However, thrombocytopenia and glomerulonephritis were reported in a few patients during the study, warranting careful monitoring of hematological as well as a metabolic panel during the Inotersen-based treatment regimen .DMD is a fatal muscle degenerative disorder caused by mutations in the DMD gene, which encodes dystrophin. This partial gene deletion causes a reading frame shift resulting in an early stop codon that not only would prevent translation to functional dystrophin protein but, most importantly, induces mRNA destruction by nonsense-mediated RNA decay . This reGolodirsen is developed by Sarepta Therapeutics for the treatment of DMD. Golodirsen utilizes a similar therapeutic strategy (PMO chemistry) as the one described for Eteplirsen. Golodirsen however, addresses patients with a different deletion in the dystrophin gene. It hybridizes with DMD pre-mRNA and cause exon 53 skipping leading to the production of short but functional dystrophin protein required for muscle activity. The safety and efficacy of Golodirsen was evaluated in a randomized, double-blind, placebo-controlled study in two phases. In the first phase, all 25 patients treated with increasing doses of Golodirsen for 48 weeks showed a 16-fold increase in dystrophin protein levels over baseline as compared to the placebo group. Golodirsen was found to be well-tolerated in patients after weekly IV infusion for 48 weeks. Muscle biopsies also indicated an increase in dystrophin production in the Golodirsen treated group as compared to the placebo group .Acute hepatic porphyria (AHP) is a genetic disorder in which the enzyme delta-aminolevulinate synthase 1 (ALAS1) is produced in excess. The excess of ALAS1 enzyme accumulates neurotoxins, aminolevulinic acid (ALA), and porphobilinogen (PBG), which results in intense abdominal pain, nausea, and seizures . GivosirMilasen is a personalized ASO that was specifically designed to treat a six-year-old child suffering from neuronal ceroid lipofuscinosis 7 (CLN7) that affects the central nervous system . This raThe list of the antisense formulations in clinical trials is expanding with many candidates successfully reaching phase III clinical trials . Here, wHuntington disease (HD) is an autosomal dominant, progressive neurodegenerative disorder characterized by dystonia, cognitive dysfunction, and behavioral difficulties . In HD, Superoxide dismutase (SOD1) enzyme plays an essential role in scavenging free radicals generated in the body. Mutation in the SOD1 gene results in the production of dysfunctional SOD1 that accumulates as toxic protein in the cells and results in familial amyotrophic lateral sclerosis (ALS). Tofersen is an ASO designed to target mutated SOD1 mRNA to prevent protein production, thereby slowing ALS progression. A phase I and II double-blind, randomized, placebo-controlled trial showed a reduction in dysfunctional cerebrospinal fluid SOD1 concentrations in the Tofersen treated group . ToferseFamilial chylomicronemia syndrome (FCS) is caused by mutations in the lipoprotein lipase (LPL) gene. This condition impairs the usual break down of fats resulting in increased accumulation of fats in the blood. Abdominal pain, eruptive xanthoma, pancreatitis, hepatosplenomegaly, and lipemia retinalis are serious manifestations of FCS. Volanesorsen, developed by Ionis Pharmaceuticals, inhibits hepatic APOC3 mRNA, resulting in reduced plasma triglyceride and apolipoprotein C-III levels. In a 53-week placebo-controlled clinical trial, Volanesorsen was given once weekly subcutaneously to 66 patients with FCS. The total triglyceride levels reduced by 76.5%, and the apolipoprotein C-III levels reduced by 84.2% from baseline at three months in patients treated with Volanesorsen . During Pouchitis is inflammation caused in the lining of a pouch created during complications in surgery or ulcerative colitis. Intercellular adhesion molecule-1 (ICAM-1), is a cell surface receptor that directs the white blood cells in circulation to sites of inflammation and increases the inflammatory response in pouchitis. Alicaforsen is an ASO developed by Atlantic Healthcare that hybridizes with ICAM-1 mRNA and reduces its levels. In clinical trials, treatment with Alicaforsen reduces inflammation and stool frequency, thereby improving the quality of life. Endoscopy showed an improvement in the underlying tissue as well .Vutrisiran is an investigational drug developed by Alnylam Pharmaceuticals for the treatment of hATTR . The mecHemophilia is an X-linked bleeding disorder caused due to deficiency of blood clotting factor VIII or factor IX . FitusirPatients with heterozygous familial hypercholesterolemia (HeFH) have high serum LDL levels, which predisposes them to atherosclerotic cardiovascular disease . Though miRNAs are 20–25 nucleotides long ncRNAs that play critical roles in the development and establishment of cell identity, and atypical expression of miRNAs leads to various malignant and non-malignant disorders. Miravirsen was developed by Roche for targeting miR-122 for hepatitis C virus (HCV) infection . MiravirThe excitement surrounding antisense oligonucleotide-based drug discovery and development had previously waned due to lack of clinical efficacy even at high ASO doses . IncrediOverall, ASO-based investigational drugs possess numerous benefits; flexibility in design due to Watson–Crick base recognition, optimized synthesis protocols as well as broad quality control during the development phase. Since ASO-based drugs target the root cause of specific diseases, they have to be administered weekly (Mipomersen) or once every four months (Nusinersen) to establish their efficacy as compared to small molecule-based drugs, which have to be administered daily in most cases. Excitingly, this field has gathered momentum in the last several years as ASO-based drugs received FDA and EMA approval for clinical applications. In addition, the rapid translation of Milasen from proof-of-concept to clinical use within months is an exceptional and enthusiastic example of the development of an ASO-based precision medicine that can improve a patient’s quality of life by reducing disease severity. Overall, ASOs can be employed as personalized medicine (Milasen), as well as for the treatment of a sizeable patient population (Inclisiran).However, several challenges need to be overcome to broaden the clinical use of ASOs, principal among them being their delivery. ASOs typically accumulate in organs like kidney, liver, and spleen, resulting in toxicity. Since several delivery platforms have been developed, a more concerted effort needs to be employed to explore delivery strategies that can deliver ASOs in maximum effective dose to target organs without off-target accumulation. Optimized delivery platforms will help reduce ASO dose, increase efficiency, and allow tissue-specific targeting that can further minimize their toxicity. In considering the delivery platforms, it is also critical to be mindful of scalability and reproducibility at the industrial scale. Similar caution must be used when designing ASOs given their potential for self-hybridization and off-target binding.In addition to rare and genetic diseases, several attempts have been made in the past to develop novel antiviral-based ASO drugs . The wor


Polypoidal choroidal vasculopathy (PCV) is a vision-threatening disease common in Asian populations. However, the optimal treatment for PCV remains under debate. We searched the databases with optimal searching strategy. The study included randomized clinical trials and prospective studies that recruited patients with active PCV who had received interventions, including PDT, anti-VEGF, or a combination of PDT and anti-VEGF. The Grading of Recommendations Assessment, Development, and Evaluation methodology was used for rating the quality of evidence. Our study included 11 studies involving 1277 patients. The network meta-analysis of RCTs revealed the anti-VEGF group, early combination group, and late combination group had significant BCVA changes compared with the PDT group. Early combination therapy led to a significant decrease in CRT compared with PDT, anti-VEGF, and late combination therapy. Additionally, the early combination group had a significantly higher complete polyp regression rate than the anti-VEGF group. No significant differences were detected in the analysis of the number of anti-VEGF injections and safety profile. This network meta-analysis revealed that early combination therapy exhibited better efficacy related to anatomical outcomes than other therapies. Nonetheless, no significant differences related to BCVA change could be detected between anti-VEGF and late combination therapy. Antivascular endothelial growth factor (anti-VEGF) agents have been the first-line therapy for PCV because of their efficacy and safety3. Moreover, anti-VEGF can be combined with photodynamic therapy (PDT) for treating PCV4. PDT is another common treatment for PCV that targets the endothelial cells of vessels, resulting in the selective occlusion of polyp vessels and the resolution of active macular edema5. Notably, PDT can be used alone or in combination with anti-VEGF to treat PCV6. However, choosing the appropriate treatment for PCV is still a critical aspect of clinical practice.Polypoidal choroidal vasculopathy (PCV) is considered a vision-threatening retinal disease. It is characterized by an abnormal inner choroidal branching vascular network with a nodular polypoidal aneurysmal lesion. The clinical features of PCV include reddish-orange nodular structures beneath the retina, serous pigment epithelial detachment, retinal pigment atrophy, and serous neurosensory detachment18. These studies have further subdivided combined therapy into early combination and late combination therapy. Notably, in early combination therapy, a patient receives PDT and anti-VEGF therapy at the beginning of the treatment course. However, in late combination therapy, patients receive anti-VEGF first, followed by rescue PDT.Several prospective observational studies and randomized clinical trials (RCTs) have reported the efficacy of anti-VEGF agents, PDT, and their combination for treating PCV22, and the latest meta-analysis derived conclusions from heterogeneous findings due to mixed data from retrospective studies and 2 RCTs. Notably, conceptual heterogeneity is unavoidable Consequently, the appropriate treatment strategy for PCV remains controversial.Synthesized evidence from 4 studies was published before 201914. Therefore, an updated synthesis might confirm existing evidence and provide insight into PCV treatment. Hence, we conducted a systematic review with network meta-analysis to compare the effects of PDT monotherapy, anti-VEGF monotherapy, early combination therapy, and late combination therapy in treating PCV in terms of BCVA improvement, anatomical changes, and safety.Furthermore, several new RCTs were completed and published in 2017 and 20189. Institutional review board approval was not deemed necessary because the study used published data for analysis.This systematic review with network meta-analysis of prospective studies was conducted to better understand the efficacy of PDT, anti-VEGF, and combination therapies in treating PCV; the study was designed in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and registered on PROSPERO  beforehand. This synthesis was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelinesPredefined eligibility criteria for evidence selection were as follows: 1) RCT or prospective study design; (2) study of patients with active PCV; and (3) use of interventions with PDT, anti-VEGF, or a combination of PDT and anti-VEGF. Exclusion criteria were as follows: (1) studies with unreported outcomes, for BCVA, proportion of patients with complete polyp regression, central retinal thickness (CRT) decrease, rates of adverse or ocular adverse events; (2) gray literature lacking a detailed report. On the basis of the different treatment modalities in the included trials, combination therapy was further subdivided into early combination and late combination therapy. Patients assigned to the late combination group where those who did not receive PDT initially but later received rescue PDT. Potential references were identified from the Cochrane Library, EMBASE, and New PubMed before February 2020. The search strategy consisted of using relevant terms such as “PCV,” “PDT,” and “anti-VEGF” in the free text and medical subject heading and using Boolean algebra. Details are provided in the Supplementary  RCT or p14, and imputation was performed. For binary outcomes, we extracted the event and total sample sizes.The 2 reviewers (SCC and YNK) independently identified and extracted relevant information, including study year; population characteristics; treatment modality; authors of studies; and outcomes, such as BCVA change, BCVA improvement rate, CRT decrease, the proportion of patients with complete polyp regression, number of anti-VEGF injections, adverse events, and ocular adverse events. The authors avoided double-count data from same trial or population by double checking relevant information of each trial. We used the Early Treatment Diabetic Retinopathy Study Visual Acuity Chart as the scale for BCVA. For continuous outcomes, mean and SD were extracted. If SE was presented in original trials, then SD was estimated from the sample size according to the relevant formula (SE = SD/√N). If relevant information of SD or SE could not be extracted from the original report, then authors were contacted. Imputation was employed using the maximum SD among eligible trials in the same outcome when the original SD could not be accessed. For instance, for the outcome of CRT decrease, Lee et al. and Koh et al. (2017) did not report relevant information for SDWith reference to relevant information regarding patient characteristics and outcomes, the 2 reviewers (SCC and YNK) independently assessed the bias of the included studies in the network meta-analysis by using the Risk of Bias 2 for RCTs and the Risk Of Bias in Non-randomized Studies of Interventions assessment. In addition, the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology was employed to rate the quality of evidence.This synthesis involved qualitative and quantitative analyses. All eligible studies were included in the qualitative synthesis, but only data from eligible RCTs were used in network meta-analysis to ensure high-quality evidence synthesis. All analyses were conducted using the random-effects model due to clinical heterogeneity. We reported continuous outcomes, in terms of weighted mean difference (WMD) and 95% CI. Dichotomous outcomes were reported using the risk ratio (RR) and 95% CI. If an effect size raised clinical concerns without statistical significance, the surface under the cumulative ranking curve (SUCRA) was further determined to demonstrate the effects through hierarchical ranking of interventions.2 statistic.All analyses were performed using STATA version 14.Inconsistency and small-study effects were analyzed to evaluate the quality of network meta-analysis. Inconsistency analysis involved a loop inconsistency test according to Lu-Ades’ method and the design-by-treatment interaction model. The primary method applied in the analysis of this synthesis was loop inconsistency, but the design-by-treatment interaction model was employed when an outcome was contributed by various arm designs. The adjusted funnel plot with Egger’s test was employed for testing small-study effects. We assessed the statistical heterogeneity by using the I18 and 7 RCTs14 were included. The flow diagram is illustrated in Supplementary Overall, 1036 potential articles were identified from the Cochrane Library k = 172), EMBASE (k = 381), and New PubMed (k = 483). After the removal of duplicates through systematic (EndNote) and manual matching, the remaining 747 articles were assessed. Finally, 4 prospective cohort studies, EMBASE 14 or central foveal thickness13 as scales to report the CRT. The baseline CRT among these participants ranged from 254.50 to 506.18um. Details of the characteristics of the included studies are summarized in Table Overall, 1277 patients were involved in the 11 studies (7 RCTs and 4 prospective cohort studies). Overall, there were 812 men. The available information revealed that the mean age of participants ranged from 61.98 to 73.70 years, and the baseline BCVA ranged from 38.5 to 63 letters. Some studies employed the central subfield thickness17. In the consistency model, the results revealed significant differences in BCVA change between the anti-VEGF group and PDT group , the early combination group and PDT group , and the late combination group and PDT group . No significant differences were detected among anti-VEGF, early combination, and late combination groups. Among the prospective cohort studies, all 4 studies reported the data of BCVA change. Teo et al. and Chong reported results similar to our analysis. By contrast, Chen et al. and Li et al. reported that combination therapy led to significantly greater BCVA change than did anti-VEGF monotherapy.Regarding the outcome of BCVA change, a total of 7 RCTs revealed this outcomeMost trials defined BCVA improvement as an EDTR gain of at least > 15 words. Only Lai et al. set the EDTR gain at this threshold. Of the 7 RCTs, 5 reported this outcome. No significant differences were detected in this network meta-analysis. The SUCRA value revealed that late combination therapy could be the optimal therapy in terms of BCVA improvement . Notably, only one non-RCT reported this outcome. Li et al. suggested that the early combination group had a higher BCVA improvement rate than the anti-VEGF group.13. The anti-VEGF group had a significantly lower complete polyp regression rate than the PDT group , and the early combination group had a significantly higher complete polyp regression rate than the anti-VEGF group . Even though no significant differences were detected between the late and early combination groups, the early combination group exhibited a more favorable trend. Regarding other non-RCTs, 2 of 4 reported this outcome. Li et al. reported no significant differences between the early combination group and anti-VEGF group regarding this outcome. However, Teo et al. reported that the early combination group had a significantly higher complete polyp regression rate than the anti-VEGF group.Of the 7 RCTs, 5 reported the outcome of complete polyp regression rate17. Overall, early combination therapy led to a significantly greater decrease in CRT than did PDT , anti-VEGF , or late combination . No significant differences were noted upon comparison of the late combination group with the PDT and anti-VEGF groups. Therefore, early combination therapy might be the optimal treatment modality for reducing CRT. Notably, 2 non-RCTs presented data of CRT decrease. Li et al. reported that early combination therapy caused a more significant decrease in CRT than did anti-VEGF, which is in agreement with the results of our analysis. By contrast, Teo et al. could not detect a significant difference with the same comparison during a 3-month follow-up.Seven RCTs reported data of CRT decrease17. We could not detect a significant difference in the analysis. High heterogenicity (I2 = 89.2%) was noted in the comparative analysis between early combination and anti-VEGF groups. The origin of heterogenicity was the study by Lim et al. We speculated that it could be attributable to the small sample size of their study (n = 5 in each group). The SUCRA value revealed that late combination therapy might require fewer anti-VEGF injections . All non-RCTs presented the data for this outcome. Chong et al. reported that the early combination group required significantly fewer anti-VEGF than did the late combination group. Li et al. reported a significant difference between early combination and anti-VEGF groups. By contrast, Teo et al. observed only a marginally significant difference (P = 0.05) with the same comparison. Chen et al. reported that the combination therapy and anti-VEGF groups required a similar number of anti-VEGF injections.Regarding this outcome, comparisons were only performed among anti-VEGF, early combination, and late combination groups. Overall, 6 of the 7 RCTs reported the total number of anti-VEGF injections during follow-up17. Overall, no significant difference was detected in this analysis. Regarding ocular adverse events, Five RCTs reported data on the outcome of ocular adverse events17. The network meta-analysis revealed no significant differences related to ocular adverse events among all treatment modalities.Of the 7 RCTs, 6 reported data of systematic adverse eventsOverall, the certainty of the evidence was low to moderate in our analysis. The level of evidence was downgraded because of the high risk of bias from randomization in most studies as well as indirectness and imprecision. Details are provided in Supplementary This study is the first systematic review and network meta-analysis of PCV treatments. We included 11 studies published before February 2020 and analyzed 7 RCTs. Notably, the results of the prospective observational studies were heterogenous and not fully compatible with our network meta-analysis of RCTs. Our analysis revealed that early combination therapy might be the optimal therapy in terms of anatomical outcome. However, in terms of BCVA change, anti-VEGF monotherapy was not inferior to the 2 combination therapy modalities.23. This finding was different from that of a crucial Fujisan study that reported similar CRT decrease in early and late combination groups9. Furthermore, Regarding BCVA change, despite combination therapy exhibiting more favorable trends, our results revealed no significant differences between the 2 modalities of combination therapy and anti-VEGF therapy, which is in agreement with the findings of most studies18. By contrast, EVEREST II reported that the early combination group had a significantly greater BCVA change than did the anti-VEGF group. This heterogenicity could be attributable to the relatively better baseline BCVA in the population of EVEREST II10. Moreover, we noticed that the results of Lim et al.17 differed from those of other studies17, possibly because of the small sample size (n = 10) in their study.A significant finding of our study is that the early combination group had the best anatomical outcomes, including complete polyp regression rate and CRT decrease. To our knowledge, anatomical outcomes are the primary focus of PCV treatment; however, the association between polyp closure rate and long-term recurrence rate remains unclear25. Kawashima et al. reported the effects of aflibercept in ranibizumab-resistant PCV. They indicated a significant difference between BCVA at 6 months and at baseline, albeit with no significant CRT decrease26. Recently, Azuma et al. reported the 2-year outcome of treat-and-extend aflibercept for ranibizumab-resistant PCV. They observed a significant CRT decrease from baseline. However, significant BCVA improvement could be observed only at the 1-year mark27. Several trials have directly compared the effects of aflibercept and ranibizumab in treating PCV. Notably, even though no significant BCVA change was observed among various anti-VEGF agent groups, the aflibercept group exhibited better anatomical outcomes29. Among our included RCTs, only one study used aflibercept as the anti-VEGF agent14. Nonetheless, because of insufficient data, we could not further compare the effects of aflibercept and ranibizumab with meta-regression or subgroup analysis in our network meta-analysis. Hence, further RCTs are warranted to explore efficacy of different type of anti-VEGF monotherapy and combination therapy.Nevertheless, variations among the population characteristics and treatment protocols merit further exploration and discussion. This information might provide useful insight for clinical practice. We summarized the important information including type of Anti-VEGF agent, protocol of PDT and protocol of rescue therapy in Supplementary 23. Nonetheless, the long-term outcomes of combination therapy were reported recently. Miyata et al. reported that BCVA improved relative to the baseline only in the first year and not after 3 to 5 years. Moreover, CRT after 5 years was reported to be similar to the baseline CRT30. Wataru et al. detected a similar deterioration of BCVA improvement after 3 years. However, a significant BCVA improvement was maintained for 5 years. They speculated that the difference between the 2 trials was attributable to the age of their population31. The longest follow-up time included in our prospective study was 2 years. Therefore, our analysis could not evaluate long-term changes.Because of the recurrent nature of PCV, follow-up time is another critical issue in PCV treatment. A previous systematic review reported that the effect of early PDT could be maintained for 2 years. However, the PCV recurrence rate ranged from 40% to 78.6% after 3 years33. In addition, Miyata et al. reported a marginally significant increase (P = 0.06) in rate of macular atrophy in the combination therapy group, and they considered repeated PDT to be related to macular atrophy in the long term30. Nonetheless, there is still no sufficient evidence regarding the long-term consequences of PDT.Regarding the safety profile, our study revealed no significant differences related to systematic or ocular adverse events among the therapeutic modalities, and few severe adverse events were reported among these studies. However, several reports have indicated that repeated PDT might damage the retinal pigment epithelium and choriocapillaris layer14, whereas others only targeted the central fovea. However, no significant inconsistency or serious heterogeneity existed in the pooled estimate of CRT decrease. Third, the follow-up time in most of our included studies was 1 year; therefore, the long-term effects of PCV therapy require evaluation in future studies. Finally, because of much higher incidence and prevalence of PCV in Asian, it was lack of data for other ethnicity. Further trial in other country is warranted for more comprehensive global perspective.Our study had some limitations. First, because of the limited number of RCTs, only 7 RCTs were included in the network meta-analysis. Meta-regression could not be performed for potential confounding factors. Second, CRT measurements reported in the eligible RCTs covered different ranges. Some of them covered the central subfieldThis study is the first systematic review and network meta-analysis regarding PCV therapy. We recruited prospective observational trials and RCTs. In addition, we critically appraised these studies and performed quantitative analysis of RCTs. Our results revealed that even though no significant differences related to BCVA change were observed among anti-VEGF, late combination, and early combination groups, combination therapy, especially early combination therapy, could result in better anatomical outcomes. Further trials are warranted to investigate the crucial aspects of PCV therapy, such as long-term effects, cost effectiveness, and predictors of therapy response.Supplementary files


Stroke produces multiple symptoms, including sensory, motor, cognitive and psychological dysfunctions, among which motor deficit is the most common and is widely recognized as a major contributor to long-term functional disability. Robot-assisted training is effective in promoting upper extremity muscle strength and motor impairment recovery after stroke. Additionally, action observation treatment can enhance the effects of physical and occupational therapy by increasing neural activation. The AOT-EXO trial aims to investigate whether action observation treatment coupled with robot-assisted training could enhance motor circuit activation and improve upper extremity motor outcomes.The AOT-EXO trial is a multicentre, prospective, three-group randomized controlled trial (RCT). We will screen and enrol 132 eligible patients in the trial implemented in the Department of Rehabilitation Medicine of Tongji Hospital, Optical Valley Branch of Tongji Hospital and Hubei Province Hospital of Integrated Chinese & Western Medicine in Wuhan, China. Prior to study participation, written informed consent will be obtained from eligible patients in accordance with the Declaration of Helsinki. The enrolled stroke patients will be randomized to three groups: the CT group ; EXO group (exoskeleton therapy) and AOT-EXO group (action observation treatment-based exoskeleton therapy). The patients will undergo blinded assessments at baseline, post-intervention (after 4 weeks) and follow-up (after 12 weeks). The primary outcome will be the Fugl-Meyer Assessment for Upper Extremity (FMA-UE). Secondary outcomes will include the Action Research Arm Test (ARAT), modified Barthel Index (MBI), kinematic metrics assessed by inertial measurement unit (IMU), resting motor threshold (rMT), motor evoked potentials (MEP), functional magnetic resonance imaging (fMRI) and safety outcomes.This trial will provide evidence regarding the feasibility and efficacy of the action observation treatment-based exoskeleton (AOT-EXO) for post-stroke upper extremity rehabilitation and elucidate the potential underlying kinematic and neurological mechanisms.ChiCTR1900026656. Registered on 17 October 2019.Chinese Clinical Trial Registry The online version contains supplementary material available at 10.1186/s13063-021-05176-x. Stroke is the leading cause of mortality and disability worldwide, placing a significant burden on healthcare facilities and socioeconomic systems . Stroke Robot-assisted training is an innovative exercise-based technique that involves the principles of motor learning, such as highly repetitive, intensive and task-specific training with feedback . StudiesAction observation therapy (AOT) has been applied as an alternative or complement to another approach to rebuild motor function for stroke rehabilitation and was developed on the neurophysiological basis of the mirror neuron system (MNS) , 16. ActAlthough there have been extensive articles investigating the application of robotic devices and action observation therapy in upper limb rehabilitation after stroke, they fail to show a superior effect in arm function and ADL compared with conventional therapy. Moreover, according to our knowledge, few studies have examined the combined effects and underlying mechanisms of these two techniques. We hypothesize that action observation treatment coupled with robot-assisted training may enhance motor circuit activation and improve upper extremity motor outcomes. Therefore, in this study, we aim to evaluate the effects of action observation treatment-based exoskeleton (AOT-EXO) treatment for the upper extremity after stroke and to explore the potential kinematic mechanisms assessed by inertial measurement unit (IMU) and neurological mechanisms using functional magnetic resonance imaging (fMRI) and corticospinal excitability metrics.This protocol follows the Consolidated Standards of Reporting Trials (CONSORT) Statement on randomized trials of non-pharmacological treatment. The study will be reported according to the SPIRIT  statement . It will be implemented in the Department of Rehabilitation Medicine of Tongji Hospital, Optical Valley Branch of Tongji Hospital and Hubei Province Hospital of Integrated Chinese & Western Medicine in Wuhan, China. A flowchart overview of the study is presented in Fig. Prior to study participation, written informed consent  age 18–80, (2) clinical diagnosis of stroke  within 6 months before enrolment, (3) Fugl-Meyer Assessment of the Upper Extremity (FMA-UE) score 8–47, (4) Mini-Mental State Examination (MMSE) score ≥ 22 and compliance with the interventions and (5) provision of written informed consent , 21.The exclusion criteria are as follows: (1) more than one stroke (patients with previous transient ischaemic attack could participate); (2) other current significant impairment of the upper limb, e.g. fixed contracture, shoulder subluxation, or recent fracture; (3) severe visual deficits or unilateral spatial neglect; (4) diagnosis likely to interfere with rehabilitation or outcome assessments, e.g. traumatic brain injury, meningitis and epilepsy; and (5) current participation in another upper limb rehabilitation trial , 22. Of The following information will be collected: demographic information, medical history, medication and rehabilitation details, stroke type, time post stroke onset, complications, comorbidity and baseline outcome measures.We will randomize all the included patients into the three groups at a ratio of 1:1:1 through a computer-generated random number table centrally generated in Tongji Hospital. An independent statistician will prepare the sequentially numbered, opaque, sealed envelopes before the start of enrolment. No randomization number will be reutilized in any case. Because the training methods differ between groups and according to the features of the robot, it is not feasible to blind the subjects, therapists or physicians participating in the trial. Therefore, an independent evaluator at each centre blinded to the randomization procedure and group allocation will assess all outcome measures .Stroke patients in all groups will require multidisciplinary medication and rehabilitation; hence, their routine treatment programmes will continue as usual with the additional 4-week intervention. The intervention will be delivered at the same frequency and duration in the three groups: 45 min daily, 5 days/week for 4 weeks. The same therapists and therapy assistants will deliver all the intervention sessions at each centre .Participants in the CT group  will receive the therapist-mediated arm intervention using conventional therapy techniques, such as muscle strengthening, stretching, arm exercises or gross-motor training, fine-motor training and functional task practice. This therapy matches that in the other groups with respect to schedule and the form and intensity of movements. The programmes in the conventional group will progress to meet the patient’s training goals.The EXO group (exoskeleton therapy) will receive intensive task-specific training in the three-dimensional workspace of the human arm involving shoulder  and elbow  movements . Each training session consists of exercises in the following order: 5-min passive mode plus 15-min assist-as-needed mode for twice with a 5-min break between intervals. In the passive mode, the exoskeleton manipulates the upper limb in a three-dimensional trajectory predetermined by the therapists according to the patient’s goals. In the assist-as-needed mode, the patients practice games and ADL training programmes dedicated to shoulder and elbow movements. When the patient is unable to complete the tasks actively, assistive force will supply the upper extremity with passive movement to the target positions.The AOT-EXO group (action observation treatment-based exoskeleton therapy) will share a training routine with the EXO group. The difference is as follows: during the assist-as-needed session in the AOT-EXO group, patients will be instructed to carefully watch video clips showing upper limb movements and related daily routine tasks before training. Each session will last approximately 15 min (2-min action observation and 3-min action execution for three movement sequences) twice per day (upper limb movements followed by related daily routine tasks in the second session). The actors in the videos will be healthy volunteers. The video clips will be obtained with a Canon camera in the first-person perspective . PatientAll outcomes will be measured at baseline, post-intervention (at 4 weeks) and follow-up (at 12 weeks) with no charge. The primary outcome will be mean change in the Fugl-Meyer Assessment for Upper Extremity (FMA-UE) score. This assessment examines arm movement, coordination and reflexes, and the results are represented as a 3-point ordinal scale score with a maximum of 66 points. The FMA-UE is a reliable and valid scale with which to measure upper limb motor impairment after stroke, with higher scores indicating better motor function .Secondary outcomes will be the mean change in Action Research Arm Test (ARAT) score, modified Barthel Index (MBI), kinematic metrics, resting motor threshold (rMT) and motor evoked potentials (MEP), functional magnetic resonance imaging (fMRI) and safety outcomes.The Action Research Arm Test (ARAT) evaluates 19 tests of arm motor function, including four subscales: grasp, grip, pinch and gross movement. Each test is given an ordinal score of 0, 1, 2 or 3, with the total score ranging from 0 to 57, with higher values indicating better arm motor status and dexterity .The modified Barthel Index (MBI) is an assessment tool formulated to examine the level of independence in the basic ADL and comprises 10 categories: feeding, personal hygiene, toilet use, bladder control, bowel control, bathing, dressing, chair/bed transfer, ambulation, and stair climbing .We will use kinematic metrics  to evaluate the movement smoothness  and performance (pointing time and pointing accuracy) during the finger-to-nose test. The instrumented kinematic assessment can provide good sensitivity for detecting motor performance that is not captured by the clinical scales , 28.Corticospinal excitability will be measured using resting motor threshold (rMT) and motor evoked potentials (MEP) from the abductor pollicis brevis (APB) muscles . Patient2. During the fMRI scan, subjects will view a guidance video displayed on the screen. The video will run continuously with a 0.03-Hz movement cycle that is green during rest epochs, yellow during task 1 epochs and red during task 2 epochs. For all conditions, each series will consist of 5 cycles alternating between a 30-s baseline block (fixation cross) followed by a 30-s task block, yielding a total duration of each fMRI run of 10 min. Before entering the scanner, subjects will practice the paradigm and an investigator will observe subject movements during scanning to verify task compliance [Functional magnetic resonance imaging (fMRI) acquisition and pre-processing will be conducted as follows. Scanning will be on the same 3.0 Tesla MR scanner , including acquisition of high-resolution anatomical images, followed by two fMRI series of two hemiplegic-sided motor tasks: finger-to-nose motion (task 1) and finger-to-nose motion sequence observation and execution (task 2). The range of motion for each task is not controlled but rather self-determined. Each series contains 30-s epochs that alternate rest with 0.03-Hz movement. We will acquire functional images using the T2*-weighted gradient echo planer imaging sequence, which measures the blood oxygen level dependence (BOLD) signal. Scanning parameters will include 43 axial 3-mm-thick slices of the whole brain per repetition, 204 volumes/series, TR = 3000 ms and TE = 30 ms, matrix size = 72 × 72 and FOV = 216 × 216 mmmpliance .Pre-processing of fMRI data will be performed with SPM8  running in MATLAB  . For each subject, after motion correction, the anatomical MRI will be co-registered to the mean functional image. The fMRI data pre-processing steps include (1) inter-slice timing correction to the middle slice of a volume for signal coherence, (2) realignment of the motion artefact to the first volume in the entire scanning period, (3) co-registration normalization of spatial transformation to the standardized head domain merged from all subjects’ imaging results  and (4) spatial smoothing with a Gaussian kernel of 4 mm full to half-maximum to elevate the signal-to-noise ratio of functional responses.Safety outcomes will include the occurrence of all adverse events and serious adverse events in accordance with the guidance of the Clinical Trials Ethics Committee of Huazhong University of Science and Technology. Possible adverse events attributable to the intervention may include shoulder pain, skin abrasion and delayed muscle soreness, which will be observed in detail and documented. Establishing causality between the protocol and adverse events will require judgment. We will rate the relevance degree of all adverse events and the intervention in the AOT-EXO trial with an ordinal score from one to five, with higher values indicating a greater degree of relevance. Although robotic training has been proven safe in the previous studies, serious adverse events may occur related or unrelated to our protocol. We have rehearsed an in-hospital first-aid plan that can be carried out expertly under emergency circumstances and will immediately report to the project investigator together with Ethics Committee, who will determine whether the participant needs to be removed from the study and whether the trial should be adjusted or terminated.The sample size was calculated by considering the primary outcome measure as the reference: a mean difference of 5 points in the FMA-UE between the AOT-EXO group and CT group and 3 points between the AOT-EXO group and EXO group with a standard deviation of 5.0 . Based oThe data monitoring committee (DMC), independent from the sponsor and competing interests, will be responsible for data monitoring procedure to ensure the accuracy and completeness of the data reported by researchers. The DMC will conduct the procedure at each centre in cooperation with all investigations from institutional review board or regulatory authority. Each centre will be responsible for quality control of the informed consent, participant recruitment, intervention programme implementation and data management.The directors of each centre will be responsible for retaining all records with complete confidentiality for 10 years after the completion or termination of the study. Each centre will apply data cleansing, identification and coding and will create an electronic data set for statistical analysis and transfer of quality control records. In cases where inconsistencies, missing values or other problems are detected in the data set, the directors at each centre will be queried and will recheck the electronic case report form (CRF) if necessary. The principal investigator and all directors of each centre will receive full anonymous copies of the electronic data set to promote dissemination of the study results.The sponsor will appoint the Trial Steering Committee (TSC) comprising investigators and clinical experts independent of the clinical trial. TSC will be responsible for the scientific integrity of the clinical trial, including the scientific validity of the study protocol, assessment of study quality and conduct and scientific quality of the final study report.P > 0.05). Continuous variables will be presented as the mean (SD) for normal distributions and median for non-normal distributions and categorical variables will be presented as frequencies or percentages. Baseline data between groups will be compared using Student’s t-test for continuous variables and the chi-square or Fisher’s exact tests for categorical variables. A P value < 0.05 will be considered indicative of statistical significance. All analyses will be carried out based on the intention-to-treat principle, with missing data calculated using multiple imputation. Within-group differences will be assessed using paired t tests for the normally distributed data and Wilcoxon-signed rank test for the non-parametric equivalent test. When comparing the two patient subgroups at each time point, Student’s t test (for continuous data) and Fisher’s exact test  will be implemented. When examining the effect of the randomization procedure over time, two-way repeated measures analysis of variance (ANOVA) will be conducted to examine the time-treatment group interaction, with time as the within-group variable and treatment group as the between-group variable.All statistical analyses will be performed using SPSS software . To assess the normal distribution of quantitative data, the Shapiro-Wilk test will be employed  may allow real-time acquisition of the structural, electrophysiological and metabolic changes in the brain to achieve more satisfactory results during robot-assisted training in the future . MoreoveIn conclusion, this study aims to evaluate the effects of AOT-EXO for the upper extremity after stroke and to explore the potential underlying kinematic and neurological mechanisms. The results of the trial will provide evidence regarding the feasibility and effectiveness of AOT-EXO for post- stroke upper extremity rehabilitation.Current recruitment. At the time of submission, 12 stroke patients have been enrolled.Protocol version number V1.0, December 2018. Recruitment began on 18 October 2019, and it is anticipated that this trial will be completed by December 2021.Additional file 1.Additional file 2.


The contribution made by e-cigarettes to smoking cessation continues to be controversial. Reports suggest that teenagers are becoming increasingly addicted to e-cigarettes and that e-cigarette use in adolescents is associated with subsequent cigarette smoking.Systematic searches of eleven databases were conducted (January 2015 to June 2020). Systematic reviews, randomized controlled trials (RCTs) and cohort studies comparing e-cigarettes with placebo e-cigarettes, nicotine replacement therapy (NRT) or no e-cigarette use were included. The two primary outcomes were smoking cessation among smokers and smoking initiation among non-smoking teenagers. The secondary outcome was adverse events. Data were synthesized using risk ratio (RR) or adjusted odds ratio (AOR) with 95% confidence interval (CI).2=57.6%; low certainty; 5 trials, n=4025). Evidence from 9 cohort studies showed that e-cigarette use was not associated with cessation . Subgroup analysis suggested that intensive e-cigarette use may be associated with cessation. In terms of smoking initiation, adolescents who ever used e-cigarettes had a greater risk for smoking initiation than non-users , the findings were consistent with one included systematic review. No serious adverse events were reported in the included studies.Six systematic reviews, 5 RCTs and 24 cohort studies were identified. For smoking cessation, findings from 4 systematic reviews indicated that e-cigarettes contributed to cessation while one found the opposite. Meta-analysis of 5 RCTs suggested that e-cigarettes were superior to NRT or placebo for smoking cessation (RR=1.55; 95% CI: 1.00–2.40; ILow certainty evidence suggests that e-cigarettes appear to be potentially effective for smoking cessation. The use of e-cigarettes in adolescents may be associated with smoking initiation. No serious adverse events were reported. Reportedly, the e-cigarette was invented by the Chinese pharmacist Hon Lik in 2003, and internationally patented in 20072. E-cigarettes have been commercially available in Europe and America since 2006 as a cigarette substitute3. E-cigarettes have always been advertised as healthy and popular smoking cessation tools4. Reports have suggested that achieving abstinence by using e-cigarettes was comparable to nicotine replacement therapy (NRT), and e-cigarettes also appear to effectively decrease cigarette consumption6. This has resulted in a dramatic increase in the use of e-cigarettes worldwide. The estimated global value of e-cigarette sales was up to US$3.5 billion in 20157. A national large-scale survey from 28 EU member states reported that there were about 48.5 million e-cigarette users in 20168.Electronic cigarettes, also called e-cigarettes are electronic nicotine delivery systems (ENDS). They can deliver vaporized liquid mainly containing nicotine and propylene glycol through the mouth into the lungs, mimicking the effects of conventional cigarette smoking9. The proportion of US high school teenagers who had tried e-cigarettes in the last month rose from 1.5% to 16.0% between 2011 and 2015, a more than 10-fold increase10. In 2019, it was estimated that among high school students in the US, 27.5% (95% CI: 25.3–29.7) were current e-cigarette users11. Worse still, many studies appear to report that use of e-cigarettes by young people increases the risk of subsequent cigarette smoking12, and that minors are an emerging new smoking population13.Increasingly teenagers are becoming addicted to e-cigarettes. Between 2016 and 2017, the proportion of e-cigarette users among those aged 11 to 16 years increased from 7% to 11%, respectively, across the UK14. These were associated with the development of cancer15 and the occurrence of coronary events16. In light of the above, the FDA banned flavored e-cigarette sales in January 2020, as flavored e-cigarettes had the most appeal to teenagers17. On 1 November 2019, China as the birthplace of e-cigarettes announced that the online purchase of e-cigarettes would be completely banned in China18. Previously, two randomized controlled trials (RCTs)6 indicated that e-cigarettes were potentially effective in smoking cessation among adult smokers. Published studies on cigarette smoking initiation associated with e-cigarette use among adolescents have been primary studies and there has been limited evidence synthesis. There are few evidence-based studies that have comprehensively evaluated the benefits and risks of e-cigarettes. Therefore, a rapid review was conducted to evaluate the effects of e-cigarettes on smoking cessation among smokers and the risks for smoking initiation among non-smoking adolescents, and their safety.Concerns have been expressed about the safety of e-cigarettes. The US Food and Drug Administration (FDA) reported that e-cigarettes contained some toxic heavy metals and the concentration of heavy metals released by e-cigarettes was much higher than conventional cigarettes19. This type of simplified systematic review is helpful in providing a timely synthesis for decision makers. Streamlined methods are usually used in a rapid review, which usually includes limiting retrieval dates and databases19. This rapid review and meta-analysis are reported following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)20 statement. A PRISMA statement with a checklist of items that should be included in reports of systematic reviews is included in the Supplementary file.Due to the urgent need to inform ongoing policy, a rapid review methodology was employedSystematic reviews based on RCTs or comparative observational studies , parallel group RCTs and controlled cohort studies were included. The study population comprised adult smokers and non-smoking adolescents, who had no serious diseases or pregnancy. The study interventions were e-cigarettes. The controls referred to placebo e-cigarettes (without nicotine), NRT or no treatment. The primary outcomes were smoking cessation among smokers and smoking initiation among adolescents. The secondary outcome was occurrence of adverse events. Experimental studies and studies that failed to report the minimal required information were excluded. There was no need for approval from an ethics committee or agreement of participants in this study as data were extracted from publications that were in the public domain.www.clinicaltrials.gov) and Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx). Search terms included: e-cigarettes, electronic cigarettes, electronic nicotine delivery systems, vape, and vaping. An example of the PubMed search strategy is given in the Supplementary file.Databases searched included PubMed, Web of Science, MEDLINE, EMBASE, the Cochrane library, China National Knowledge Infrastructure (CNKI), Chinese Scientific Journal Database (VIP), SinoMed and Wanfang, from January 2015 to June 2020. The reference lists included in the systematic reviews were also searched. A systematic search was also conducted in Clinical Trials.gov  independently screened studies by title and abstract, according to the eligibility criteria. In the full text screening process, uncertainty and insufficient information was determined for eligibility through full texts. Disagreements were resolved by discussion or arbitrated by a methodologist (JPL). Reasons for excluding studies were recorded at this stage. After identification of studies, data were extracted independently by two authors (SJZ and FLB) and included: characteristics of study design ; details of PICO ; and follow-up and adjusted factors. Any disagreements were resolved by discussion or third-party adjudication.21 was employed to assess whether the risk of bias of RCTs was low, high or unclear according to its seven domains. A Measurement Tool to Assess Systematic Reviews (AMSTAR-2)22 which has 16 items with 7 key items was employed to assess the quality of the included systematic reviews; the overall confidence for each review was assessed as high, moderate, low or critically low. The quality of cohort studies was assessed by Newcastle-Ottawa Scale (NOS)23, which is composed of 8 items and includes three subscales: selection of studies, comparability of studies, and the ascertainment of exposure. The maximum score is 9 points and any study scoring >5 points was considered of moderate to high quality23. Grading of Recommendations Assessment, Development and Evaluation (GRADE)24 was employed to assess the certainty of evidence from RCTs in five domains .The methodological quality assessment of each included study was performed independently by two review authors (FLB and SJZ). Cochrane Risk of Bias tool (ROB)2 statistic was employed to assess statistical heterogeneity21. When p<0.10 and I2>50%, the heterogeneity may be considered as high25. To explain heterogeneity, we predefined the subgroup analysis by the frequency of e-cigarette use: intensive use (daily or regular use for at least one month) versus intermittent or irregular use. Sensitivity analysis was employed to test the robustness of the results when the primary outcomes were statistically different for the following three methodological domains: reported clear randomization concealment or not; placebo used or not; and reported lost to follow-up or not. Funnel plots were employed to detect the possibility of publication bias if ≥10 studies were included in a meta-analysis.Qualitative and quantitative methods were adopted to synthesize the findings. The findings from systematic reviews were narratively described. Data are presented as risk ratios (RRs) or adjusted odds ratio (AORs) with 95% confidence intervals (CIs). Meta-analysis was performed by Stata version 14.0 software when the trials had acceptable heterogeneity and similarities in clinical characteristics. The random effects model (REM) was utilized in the meta-analysis to consider potential sources of clinical heterogeneity. The I31 were narratively described. The screening process is shown in Initially, 1620 records were retrieved and 926 duplicates were removed. In all, 612 records were excluded by scanning the title and abstract due to irrelevant studies, protocols, clinical studies, case-control studies or cross-sectional surveys, commentary of included studies, and studies that provided only abstracts. This left 82 remaining records, of these, 47 studies were excluded through full-text screening due to ineligible study design, uncontrolled cohort studies or lack of cessation outcomes. Finally, 35 studies were included after full-text screening. Of these studies, findings from 6 systematic reviews31, 5 RCTs36, and 24 cohort studies60. These studies were classified into two categories based on the two primary outcome measures. Nineteen studies45 examined the effects of e-cigarette use on smoking cessation, and the remaining 16 studies60 explored the causality between e-cigarette use and smoking initiation among teenagers. The study population included adult smokers and non-smoking adolescents and young adults. The definition of e-cigarette use was ‘current use’, ‘ever use’ or ‘past 30-day use’. In terms of the included 6 systematic reviews, 5 reviews30 focused on smoking cessation among adult smokers, and included either RCTs, cohort studies or cross-sectional studies. Another systematic review31 was based on 9 cohort studies and explored the association between e-cigarette use and subsequent smoking initiation. The 5 RCTs36 involved data from 4025 adult smokers. The sample size ranged from 99 to 886. Three trials35 compared the effect of e-cigarettes with NRT on smoking cessation. The other 2 RCTs36 compared the effect of nicotine e-cigarettes with placebo or no treatment. A total of 24 cohort studies were identified. The sample size ranged from 146 to 17318 with a total of 91985 participants. Nine studies45 focused on smoking cessation, of which, 4 studies42 overlapped with the included systematic reviews30. Another 15 cohort studies60 focused on the association between e-cigarette use and subsequent smoking initiation among teenagers. Of these, six56 studies overlapped with the included systematic review31. The follow-up time varied from 6 months to 2 years.The characteristics of the included studies are shown in 26 or one28 non-critical weakness in two systematic reviews, and these were rated as high confidence according to AMSTAR-2. Three31 were rated as low confidence due to the lack of a protocol and inadequate details of the included studies. One27 was of critically low confidence as it lacked a protocol and the lists of excluded studies. Details are shown in 34 were well described and were judged as having a low risk of bias. Blinding of the participants and personnel was only reported for one RCT33 and was rated as ‘low’ in the blinding domain. Apart from this, the risk of performance bias was rated as ‘high’ in the other 4 RCTs36, but the outcome assessment was blinded in these 4 RCTs and were rated as having low risk of detection bias. Intention-to-treat analysis was conducted in 5 RCTs36, and the attrition rate was <10%; all RCTs were assessed as having low risk of attrition bias. In terms of reporting bias, 3 RCTs36 were assessed as ‘low’ since the protocols were registered and the consistency between the outcomes described in protocol and actual outcomes in the results; the remaining 2 RCTs33 were assessed as ‘unclear’ due to lack of a registered protocol. The baseline data were comparable for 4 RCTs36, one35 was rated as ‘unclear’ due to the lack of baseline data. The risk of bias summary is shown in There were no28 compared e-cigarettes with placebo e-cigarettes on smoking cessation, but only 2 RCTs6 were eligible for the meta-analysis. The abstinence rates for at least 6 months were 4% (placebo group) and 9% (e-cigarette group), suggesting that e-cigarettes were more likely to favor cessation . This was consistent with 3 systematic reviews30. Another systematic review26 reported that the odds of cessation were 28% lower in the e-cigarette group than the non-use group .A Cochrane systematic review36 reported the abstinence rate, with 180 of 2201 (8.2%) smokers achieving cessation in the e-cigarette group versus 103 of 1824 (5.6%) in the control group, suggesting that e-cigarettes may be superior to NRT or placebo on smoking cessation  (2=57.6%). Details are shown in Five newly conducted RCTs n=4025) , Table 545 reported the adjusted odds ratio (AOR) for cessation. The pooled results suggested that e-cigarettes were not associated with smoking cessation   .Nine cohort studiesn=22220) . Subgrou31 based on cohort studies involving 17389 young people aged 14–30 years was identified. This review indicated that ever e-cigarette users were more likely to initiate cigarette smoking at follow-up than never users (23.2% vs 7.2%) .Only one systematic review60 were included. The pooled results suggested that ever e-cigarette users were more likely to initiate smoking than non-e-cigarette users   appeared to be asymmetrical, suggesting that there was potential publication bias.Fifteen cohort studies34. Two systematic reviews28 reported minor adverse short-term events related to e-cigarettes. These included irritation of the mouth and throat, cough and respiratory diseases, but long-term safety is still unknown. Two studies32 reported that there was no statistical difference in adverse events between the e-cigarette group and control group. One RCT34 reported that adverse events were significantly lower in the e-cigarette group (6.7%) compared with the NRT group (17.3%); adverse events included oral pain, cough, headache, and nausea. No serious adverse events were reported in the included trials.Of the 35 included studies, adverse events were reported in 5 studies30 indicated that e-cigarettes were superior to placebo for cigarette smoking cessation. Another systematic review26 reported that the odds of cessation were 28% lower in the e-cigarette group than the non-use group. Five RCTs (two36 placebo or no treatment controlled and three35 NRT controlled) reported that the abstinence rate in the e-cigarette group was 2.6% higher than that in the control group, suggesting that e-cigarettes may be more effective than NRT or placebo in achieving smoking cessation among adult smokers. However, this evidence was downgraded due to the small number of events and inconsistencies as assessed using GRADE. Nine cohort studies involving 22220 adult smokers found that e-cigarettes were not superior to non-e-cigarette use for cessation. Subgroup analysis suggested that intensive e-cigarette use (daily or regular use for at least one month) may contribute to cessation, while intermittent or irregular use did not. In light of the limited number of RCTs and the findings from cohort studies on smoking cessation, we could not draw robust conclusions from current evidence. In terms of smoking initiation, one systematic review31 reported that ever or past 30-day e-cigarette use was more likely to initiate smoking among teenagers. Updated estimates (AORs) of 15 cohort studies60 involving 68943 adolescents suggested that ever e-cigarette users were nearly 3 times more likely than non-users to begin smoking cigarettes. However, the evidence was limited due to potential bias . No serious adverse events were reported in the included studies.In the light of current policies on e-cigarettes in China and the US, it was timely to conduct a rapid review to comprehensively evaluate the benefits and risks of e-cigarettes. Thirty-five studies published from January 2015 to June 2020 were evaluated and included 6 systematic reviews, 24 cohort studies and 5 RCTs. The study population included adult smokers with or without intention to cease smoking and non-cigarette smoking adolescents. Four systematic reviews30 have merely focused on the benefits of e-cigarettes for smoking cessation or the risks for smoking initiation31. Former systematic reviews were based on primary studies such as RCTs and cohort studies. We identified the latest systematic reviews, RCTs and cohort studies published in the last six years to provide comprehensive and rapid evidence for policy makers. This is the first rapid review to evaluate the benefits and risks of e-cigarettes, comprehensively. A newly published Cochrane systematic review61 found that nicotine e-cigarettes were superior to placebo e-cigarettes or NRT for smoking cessation. This was consistent with the findings from 5 newly conducted RCTs36 in this rapid review. In addition, this review conducted a subgroup analysis based on the frequency of e-cigarette use.Previous systematic reviews62. Juul is the most popular e-cigarette in the US63. Therefore, it is essential to study new products in the future in terms of their effect on quitting or initiating cigarettes. The definition of smoking cessation or smoking initiation needs to be clarified, the current standards suggest that the duration is for at least 30 days cessation or smoking initiation at follow-up. Likewise, the effects of electronic cigarettes on smoking cessation among smokers with long-term or short-term smoking may vary. Hence, different smoking durations among smokers should be well reported and stratified in future studies. In terms of outcomes, objective measurements of smoking initiation rather than self-reported measurements are warranted. Cotinine as a biomarker64 of smoke exposure can be used to predict smoking initiation among adolescents. Additionally, dropouts should be minimized as much as possible in future cohort studies. Last but not least, the long-term safety of e-cigarette use should also be a future focus. For policy makers, appropriate e-cigarette use may be potentially effective in smoking cessation for adult smokers. However, e-cigarette use in adolescents was potentially associated with subsequent smoking initiation, and therefore the sale of e-cigarettes to minors should be banned completely worldwide.For the study design, future studies should consider the frequency of e-cigarette use, the concentration of nicotine in e-cigarettes and the type of e-cigarettes, since the quitting or initiating smoking effects of e-cigarette use could be potentially affected by those factors. E-cigarette products change very rapidly, especially the Juul type e-cigarettes, which use nicotine salt and can deliver a higher dose of nicotineRapid review methodology was employed to provide timely evidence on e-cigarette use due to the urgent need to inform ongoing government policies. This is the first rapid review to evaluate the benefits and risks of e-cigarettes, comprehensively. The latest eligible systematic reviews, RCTs and cohort studies were all identified in order to provide a comprehensive evaluation on e-cigarette use. However, there are several limitations. First, similar to other rapid reviews, the search time was limited from January 2015 to June 2020, and some evidence may have been missed. The results for smoking initiation were at risk of publication bias. Second, though the evidence from 5 RCTs suggested that e-cigarettes were superior to NRT or placebo for smoking cessation, the certainty of evidence was downgraded due to imprecision and inconsistency. Additionally, evidence from 9 cohort studies suggested that ever e-cigarette use was not associated with smoking cessation. Thus, the smoking cessation effect of e-cigarettes still could not be determined based on current evidence.Low certainty evidence suggests that e-cigarettes appear to be potentially effective in smoking cessation for adult smokers. However, this beneficial effect needs to be further confirmed in large sample, well designed and fully reported trials. The use of e-cigarettes in adolescents may be associated with subsequent smoking initiation. No serious adverse events were reported in the included studies, however, the long-term safety of e-cigarettes should also be a future focus.Click here for additional data file.


Are statins associated with a reduced risk of postoperative adhesion-related complications?In these 2 separate retrospective cohort studies using population-representative data sets including more than 1.3 million individuals, statin use at the time of intra-abdominal surgery was significantly associated with an 8% to 19% reduction in adhesion-related complications and a 12% to 20% reduction in small-bowel obstruction after intra-abdominal surgery.The findings of this cohort study suggest that statin use at the time of intra-abdominal surgery may be associated with a decreased risk of postoperative adhesion-related complications. Adhesion-related complications (ARCs), including small-bowel obstruction, are common complications of intra-abdominal surgery. Statins, which have antifibrotic pleiotropic effects, inhibit adhesion formation in murine models but have not been assessed in humans.To assess whether statin use at the time of intra-abdominal surgery is associated with a reduction in ARCs.These 2 separate retrospective cohort studies  compared adults receiving statins with those not receiving statins at the time of intra-abdominal surgery. Individuals undergoing intra-abdominal surgery from January 1, 1996, to December 31, 2013, in the United Kingdom and from January 1, 2000, to December 31, 2016, in the US were included in the study. Those with obstructive events before surgery or a history of inflammatory bowel disease were excluded. Data analysis was performed from September 1, 2012, to November 24, 2020.The primary exposure was statin use at the time of surgery.The primary outcome was ARCs, defined as small-bowel obstruction or need for adhesiolysis, occurring after surgery. Sensitivity analyses included statin use preceding but not concurrent with surgery, fibrate use, and angiotensin-converting enzyme inhibitor use. All analyses were adjusted for age, sex, and conditions associated with microvascular disease, such as hypertension, hyperlipidemia, obesity, and tobacco use; surgical approach and site; and diagnosis of a malignant tumor.A total of 148 601 individuals met the inclusion criteria for THIN  and 1 188 217 for Optum . A total of 2060 participants (1.4%) experienced an ARC in THIN and 54 136 (4.6%) in Optum. Statin use at the time of surgery was associated with decreased risk of ARCs . Similar associations were appreciated between statins and small-bowel obstruction .This study’s findings suggest that, among individuals in 2 separate cohorts undergoing intra-abdominal surgery, statin use may be associated with a reduced risk of postoperative ARCs. Statins may represent an inexpensive, well-tolerated pharmacologic option for preventing ARCs. This analysis of 2 large, population-representative cohort studies of patients undergoing intra-abdominal surgery in the UK and US assesses whether statin use at the time of surgery is associated with a reduction in adhesion-related complications. More than 70% of small-bowel obstructions (SBOs) and 40% of cases of infertility are secondary to adhesions.5 Future operations in patients with adhesions are associated with inadvertent enterotomy rates of 10% to 20%, resulting in an estimated mortality of 13%.6More than 90% of patients develop adhesions after intra-abdominal surgery.13 Given the high prevalence of adhesion-related adverse events, a concerted effort has been made to prevent their formation. Expert-based recommendations have focused on surgical technique and laparoscopy, although the effect of such changes on reducing ARC remains modest.15 Barrier agents have been developed, but their efficacy in reducing adhesion-related SBOs remains uncertain, and their use is associated with an increased risk of abscess formation.17 An analysis18 of secular trends in ARCs, including SBO and adhesiolysis, during the past 20 years found no significant change in rates of these complications despite these methods and devices.The pathogenesis of adhesion formation is believed to involve foreign-body exposure, surgical location, and tissue hypoxia. These factors result in inflammation and a profibrotic cytokine milieu.12 have found that adhesion-related fibroblasts express higher rates of transforming growth factor β, cyclooxygenase 2, and interleukin 10 and reduced levels of tissue plasminogen activator (tPA). Current therapies do not directly target this profibrotic milieu.The key to reducing ARCs may lie in directly inhibiting the profibrotic cytokines that promote their formation. In vitro studies19 Rho-associated protein kinase is a regulator of tPA-1 and plasminogen activator inhibitor 1. Through inhibiting farnesyl pyrophosphate, statins downregulate plasminogen activator inhibitor while increasing tPA expression22 (24β-Hydroxy-β-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins) may inhibit profibrotic cytokines. Statins directly influence adhesion-related cytokines in vitro and in murine models through inhibiting farnesyl pyrophosphate and geranylgeranyl pyrophosphate formation. Geranylgeranyl pyrophosphate is a key precursor for RhoA and Rho-associated protein kinase activation.ession22 . Statins25 found a significant reduction in adhesion formation in mice undergoing intra-abdominal surgery when exposed to statins intraoperatively. This finding was reversed with coadministration of mevalonate, a downstream HMG-CoA reductase product. These findings were confirmed in rats.26 To date, the association of statins with adhesion formation in humans has not been assessed. In addition, no data regarding statins and ARCs, such as SBOs or need for adhesiolysis, are available to our knowledge. In this study, we examined the association between statin use at the time of intra-abdominal surgery and subsequent risks of ARCs in 2 large, population-representative cohorts in the United Kingdom and the US, while adjusting for other comorbidities and surgical factors that could increase the risk of ARCs.The association of statins with adhesion formation has been confirmed in murine models. Aarons et al27 Mean follow-up time within THIN exceeds 5 years. THIN represents approximately 6% of the UK population27; includes information on age, sex, and socioeconomic status; and has been validated for multiple diagnoses.31 THIN is well recognized as a validated epidemiologic resource for medication use.29 We previously validated diagnostic codes for abdominal operations and ARCs, including SBOs and lysis of adhesions within THIN.32Two retrospective cohort studies were performed to assess the association between statin use at the time of intra-abdominal surgery and postoperative ARCs. The first study used data collected prospectively in the scope of routine care from January 1, 1995, to December 31, 2013, within The Health Improvement Network (THIN). THIN includes data derived from the electronic medical records of more than 12 million patients, with 3.6 million active patients within 550 general practices within the United Kingdom.36A second retrospective study was performed using Optum’s Clinformatics Data Mart database (Optum), a medical claims database from a single private payer with patient-level data on more than 77 million unique patients from January 1, 2000, to December 31, 2016, within the US. Optum contains inpatient, outpatient, and surgical claims and pharmacy data and has been used for numerous pharmacoepidemiologic studies.STROBE) reporting guideline.Data analysis was performed from September 1, 2012, to November 24, 2020. This study was approved and/or considered exempt by the University of Pennsylvania and University of Colorado institutional review boards and was approved by THIN’s Scientific Review Committee. Because this study was a secondary analysis, informed consent was not required. All data were deidentified. The study followed the Strengthening the Reporting of Observational Studies in Epidemiology  and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes and Current Procedural Terminology (CPT) (version 4) codes for intraperitoneal surgical events , and current use . Indications for initiation or cessation of statin use were not available, although statins are most often prescribed for hyperlipidemia or cardiac protection. Statin exposure at the time of surgery was further classified by strength of low-density lipoprotein cholesterol (LDL-C)–lowering effect as low intensity, moderate intensity, and high intensity .40), obesity (using diagnostic codes or body mass index when available), and tobacco use  were also assessed. Last, a diagnosis of malignant tumor that involved the peritoneum before surgery was assessed because subsequent obstruction could be caused by tumor progression rather than adhesions.Covariates included age at surgery, sex, and whether the index surgery involved the small bowel or colon. Age was stratified by 3 categories: 18 through 44 years, 45 through 64 years, and 65 years or older. Given the hypothesized role of tissue hypoxia in adhesion formation, hypertension (defined via diagnostic codes or associated medications), hyperlipidemia . Categorical variables were summarized as ratios and percentages, whereas continuous variables were reported using medians and interquartile ranges (IQRs), stratified by statin use at the time of surgery. Descriptive statistics were used to compare statin users with nonusers and those with ARCs with those without.43 Fully adjusted models were inclusive of all variables. Iterative stepwise backward elimination was performed, removing variables not modifying the association between statin use and ARCs by greater than 10% to identify parsimonious models.44 Nonproportionality assumptions were assessed using graphical methods and Schoenfeld residuals.46 All analyses were conducted separately within THIN and Optum.The association between statin use relative to no use and ARCs was assessed using time-to-event analyses. Follow-up time started at the time of index intra-abdominal surgery and ended on the earliest of the following: an outcome of interest (ARC) or a censoring event, such as transfer out of a THIN practice or end of coverage period in Optum, death, or the end of recorded data. Because individuals could have multiple periods of coverage with associated gaps in Optum, they were censored after their initial enrollment period. Multivariable Cox proportional hazards regression models were used to assess the association between covariates and ARCs, calculating hazard ratio (HR) point estimates and 95% CIs.39 Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) were assessed as an alternative medication class with known antifibrotic effects49 in THIN as well. Because age was a 3-level categorical variable in our primary analyses, we performed our analyses again with the inclusion of age as a continuous variable in THIN. We performed additional sensitivity analyses that examined the association between statins and SBO given the clinical consequences of this specific outcome  in THIN and Optum. To assess whether the treatment effect was associated with the HMG-CoA reductase inhibition vs lipid lowering, fibrate use was assessed in both cohorts. To assess the impact of statin potency, statin use was stratified by level of HMG-CoA reductase inhibition in THIN. Statins were grouped based on expected percentage of LDL-C reduction, with low-intensity statins reducing LDL-C by less than 30%, moderate-intensity statins by 30% to 50%, and high-intensity statins by greater than 50%.Within THIN, 148 601 individuals  who met the inclusion and exclusion criteria underwent an index intra-abdominal operation. Median follow-up time was 1412 days . Baseline characteristics are presented stratified by statin exposure in Overall, 11.7% of individuals were using a statin at the time of surgery . Median In multivariable analyses, statin use at the time of intra-abdominal surgery was associated with a reduced hazard of postoperative ARCs . Increasing age , bowel surgery , and a history of malignant tumors  were associated with increased ARC risk . Sex, diIn Optum, 1 188 217 individuals  with an index intra-abdominal surgery were identified. Within this cohort, 54 136 individuals (4.6%) experienced a postoperative ARC. The median follow-up time was 1227 days . In all, 10.8% of individuals were using statins at the time of surgery, whereas 0.4% were using fibrates. Rates of comorbidities associated with microvascular disease, history of malignant tumors, and surgical site are described in In this cohort, statin use at the time of surgery was associated with a decreased risk of ARCs  . DiseaseFibrates and ACEIs or ARBs were not associated with the risk of ARCs . When exCompared with no statin use, use of statins with an expected LDL-C lowering of less than 30% was not associated with a reduction in ARCs , whereas those with 30% to 50% LDL-C lowering  and greater than 50% LDL-C lowering  were significantly associated with reduced ARCs. Similar results were seen for SBOs , 2 negative controls were used, a likely dose-response curve was assessed, and propensity score matching was performed, it is possible that unmeasurable factors may influence the association between statins and ARCs. Such factors could include perioperative complications or medication use, barrier use, and operative techniques. Future prospective research with granular data collection on surgical factors that may augment the association between statins and ARCs is required. The research presented here supports future prospective efforts.In summary, this research suggests that statin use may be significantly associated with a decreased probability of ARCs and SBOs after intra-abdominal surgery. Future prospective randomized clinical trials of this inexpensive, well-tolerated therapy will be required to confirm these findings.