Systematic review and meta-analysis of drug induced liver injury secondary to biologic medications in inflammatory bowel disease

Intestine is most commonly affected, although the large intestine may also be involved. Common symptoms include abdominal pain, diarrhea, weight loss, bleeding, nausea and vomiting [3]. Abdominal complications may include bowel obstruction, perforation, abscesses, istulas, and peri-anal disease [4]. Round about twenty percent of people with CD go through extra-intestinal complications that may include musculoskeletal, ocular, dermatologic, hepato-biliary, renal and hematological conditions [5]. On the other hand we have Ulcerative colitis which is an idiopathic in lammatory condition of the colon which results in diffuse friability and super icial erosions on the colonic wall associated with bleeding [6]. It is the most common form of in lammatory bowel disease worldwide [7]. It typically consists of in lammation limited to the mucosa and sub mucosa of the colon [8]. Typically, the disease starts in the rectum and extends proximally in a continuous manner [9]. The cause of in lammatory bowel disease is indistinguishable, but it seems to occur in genetically disposed people in response to environmental factors [10]. Ulcerative colitis is almost certainly an autoimmune disease initiated by an in lammatory More Information


Introduction
Ulcerative colitis (UC) and Crohn's disease (CD), collectively known as in lammatory bowel disease (IBD), are both characterized by a diffuse in lammation of the bowel [1]. Crohn's disease (CD) is a chronic, episodic, in lammatory condition of the gastrointestinal system, with affected regions consisting of transmural ulceration separated by normal mucosa [2]. The small Intestine is most commonly affected, although the large intestine may also be involved. Common symptoms include abdominal pain, diarrhea, weight loss, bleeding, nausea and vomiting [3]. Abdominal complications may include bowel obstruction, perforation, abscesses, istulas, and peri-anal disease [4]. Round about twenty percent of people with CD go through extra-intestinal complications that may include musculoskeletal, ocular, dermatologic, hepato-biliary, renal and hematological conditions [5]. On the other hand we have Ulcerative colitis which is an idiopathic in lammatory condition of the colon which results in diffuse friability and super icial erosions on the colonic wall associated with bleeding [6]. It is the most common form of in lammatory bowel disease worldwide [7]. It typically consists of in lammation limited to the mucosa and sub mucosa of the colon [8]. Typically, the disease starts in the rectum and extends proximally in a continuous manner [9]. The cause of in lammatory bowel disease is indistinguishable, but it seems to occur in genetically disposed people in response to environmental factors [10]. Ulcerative colitis is almost certainly an autoimmune disease initiated by an in lammatory response to colonic bacteria [11].Conservative medications for irritable bowel disease such as Ulcerative colitis (UC) and Crohn's disease (CD), include anti-in lammatory drugs, immune-suppressants and corticosteroids [12]. Still an individual does not respond, or loses response to irst-line treatments, then biologic therapies such as tumour necrosis factor-alpha (TNF-G) antagonists such as adalimumab are considered for treating irritable bowel disease [13]. Maintenance of remission of IBD is a clinically important goal, as disease relapse can negatively affect quality of life [14]. Amongst the most commonly prescribed treatments for several chronic in lammatory diseases one of the categories of medications are biologics [15]. Tumor necrosis factor alpha inhibitors, more so than other agents, have been observed to cause drug-induced liver injury. Additionally, because the approval and popularity of checkpoint inhibitors have grown, similar patterns of liver injury have been documented, with a majority of cases describing immune-mediated hepatitis [16]. Although the exact mechanism of injury is unknown, various host and medication characteristics play a role in the outcome of the molecular cascade invoked by biologics [17]. Prognosis is usually favorable with cessation of the damage causing agent, but cases of acute liver failure requiring liver transplantation have also been observed [18]. Therefore, algorithms have been created to assist clinicians in treating drug-induced autoimmune hepatitis, mostly with corticosteroids [19]. Additionally, case reports have documented successfully re-challenging patients with a different biologic without recurrence of liver injury, but data are limited [20]. Further investigation is warranted regarding the potential for cross-reactivity and mechanism of injury to develop guidelines to aid clinicians in further management of these patients [21].
Hepatobiliary disorders are common in patients with in lammatory bowel disease (IBD), and persistent abnormal liver function tests are found in approximately twenty to thirty percent of individuals with IBD. In most cases, the cause of these elevations will fall into 1 of 3 main categories [22]. They can be as a result of extraintestinal manifestations of the disease process, related to medication toxicity, or the result of an underlying primary hepatic disorder unrelated to IBD [23]. Biologic therapy to inhibit tumor necrosis factoralpha (TNF-), a pro-in lammatory cytokine, has become a widely used, safe, and effective treatment for patients with in lammatory bowel disease (IBD) [24]. For more than the past two decades, biologic therapies have revolutionized the care for people with in lammatory bowel disease (IBD), but each therapy has its own risks, together with the likelihood of liver damage. Numerous classes of biologics for the treatment of IBD now exist [25]. Tumor necrosis factor α (TNF-α) inhibitors were the irst biologic class approved for use in 1998. Mechanism of action of these monoclonal antibodies (mAbs) is directed against proin lammatory TNF molecules, which are frequently increased in IBD patients [26]. It has also been reported that he development of anti-drug antibodies with biologic therapy possibly will have positive implications for long-term management [27]. Hence, therefore it was essential to carry out a review study the hepatotoxicity caused by biologics given for treatment of Ulcerative colitis (UC) and Crohn's disease (CD), in IBD patients.

Search methods for identifi cation of studies
Detailed search strategies for each electronic database were developed based on the one used for Pubmed (Ovid) Medline, and (Ovid) Embase but with appropriate database related search strategy modi ication such as the use of truncations, wildcards, and ilters [28]. The subject search used a combination of the controlled vocabulary terms "Mesh terms" and free-text words based on the search strategy developed for Medline.
We searched the following databases with English language restriction applied in each database until 2020 from the studies inception.

• Cochrane IBD Group Specialized Register
With the guidelines described by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) [29].
This review covered controlled trials in which biologic was administered to one study group; the control group may or may not have received a placebo.

Criteria for considering studies for this review
Types of studies: We include prospective and retrospective RCTs that assessed the ef icacy and hepatotoxicity of biologigcs in IBD patients.

Types of participants:
This review includes participants of any age who have been diagnosed with Ulcerative colitis (UC) and Crohn's disease (CD), using clinical, radiological, endoscopic or histological criteria.

Types of interventions:
This review includes trials that compared any biologic either to a placebo or to an active comparator.
Outcome measures: Studies done on ef icacy and events of adverse effects, such as liver injury by biologics in IBD patients. https://doi.org/10.29328/journal.acgh.1001025

Data collection and analysis
Two review authors independently assessed the titles and abstracts of studies identi ied by the search criteria to determine eligibility according to the inclusion criteria. We discussed disagreements until we reached a consensus among the review authors, and consulted with a third review author when we could not reach agreement. The characteristics of all included studies are presented in table 1.

Data extraction and management
Two review authors independently extracted data using a standardized extraction form. We discussed any disagreements over extracted data, and then brought them to a third review author for resolution as required. We extracted the following information: 1. General information (type of publication, title, journal, year).

Study design features (method of randomization,
concealment of allocation and blinding, power calculation, dates of enrolment and follow-up, study).     8. Funding details and author con licts of interest.

Assessment of risk of bias in included studies
Two review authors independently assessed risks of bias using the Cochrane 'Risk of bias' tool [30]. We assessed several study characteristics for risks of bias, including random sequence generation, allocation concealment, blinding, incomplete outcome data, and selective outcome reporting and other potential sources of bias. Based on these criteria, we rated the studies as having a low, high or unclear risk of bias for each category. We discussed any disagreements about risks of bias and then brought them to a third review author as necessary.

Statistical analysis
We used Review Manager 5 (RevMan5) to analyze the data. For dichotomous outcomes, we calculated the Odds ratio (OR) with a 95% con idence interval (CI).

Assessment of heterogeneity
We assessed heterogeneity using the chi 2 test and the I 2 statistic [31]. We considered an I 2 value of less than 25% indicative of low heterogeneity, greater than 50% indicative of moderate heterogeneity and greater than 75% high heterogeneity.
For the chi 2 test, we considered a p value of 0.10 to be statistically signi icant. If the I 2 statistic and chi 2 test suggested heterogeneity, we visually inspected the forest plot for outliers. We used a sensitivity analysis (e.g. excluding outliers) to explore potential explanations for heterogeneity.

Assessment of reporting biases
We used a funnel plot to assess publication bias found between the studies which are presented in igure 3 [32].

Data synthesis
We combined data from individual trials for meta-analysis when interventions, participant groups and outcomes were suf iciently similar. We determined this by discussion and consensus among the review author team. We calculated the pooled OR with a 95% CI for dichotomous outcomes. As there were not a signi icant heterogeneity between our study we used a ixed-effects model to pool the data.

Sensitivity analysis
We used sensitivity analysis to examine the impact of the following variables on the pooled effect estimate: 1. Random-effects versus ixed-effect modeling.

Low risk of bias versus unclear or high risk of bias.
3. Relevant loss to follow-up (more than 10%).

4.
Full-text articles versus abstract or unpublished studies.

Description of studies/Results of the search
Our literature search identi ied 862 records in total. After we had removed duplicates 564 records were left for review. Two review authors (MK and SK) independently reviewed the titles and abstracts of these records and selected 40 fulltext articles for review, we further excluded thirty one studies with different reasons and inally seven studies [33][34][35][36][37][38][39] (total of 896 participants) met the prede ined inclusion criteria and were included in this review (Figure 1).

Risk of bias in included studies
We assessed the methodological quality of each study using the Cochrane 'Risk of bias' tool and we summarize our indings in igure 2.

Allocation
Four studies did not report on how participants were randomized to treatment groups or how allocation concealment was achieved. We rated these studies at unclear risk of bias for these domains [35,36,38,39].

Blinding
Two studies did not report on how blinding was maintained for participants, personnel or outcome assessors throughout the study time period. We rated these studies at unclear risk of bias for these domains [38,40].

Incomplete outcome data
One study [39] did not report on the number of participants who were initially randomized, so we could not determine the number of participants who had withdrawn during the study period. We rated the study at unclear risk of bias for this domain.

Selective reporting
All of the included studies reported on all expected outcomes and were rated at low risk of bias for this domain.

Other potential sources of bias
Five of the included studies appeared to have other potential sources of bias and were rated at low risk of bias for this domain [35,36,38,39].

Result of pooled data
All of our included trials mentioned adverse effect of biologics on liver which are analyzed statistically and result is summarized in igure 3, there was not presence of any heterogeneity among studies by (Chi 2 = 2.21, df = 6, p = 0.90,  and I 2 = 0%), when the whole seven studies were involved for analysis. Our meta-analysis was conducted on the ixed effects model, with the (0.770, 95% CI [-0.630, 0.957], and p = 0.02).

Publication bias
The funnel plot was generated based on the mean adverse events; funnel plot was applied to evaluate the publication biases of all seven studies. Summarized in igure 4, the outcome suggests that there was not signi icant publication bias.
in IBD patients treated with thiopurinic immunomodulators [42]. The incidence of abnormal LFTs or liver toxicity is a relevant inding during the follow-up of patients treated with thiopurinic immune-modulators as it was showed in their study conducted with a cohort of 161 IBD patients [43]. There is a lack of recent published series that speci ically assess thiopurine-induced hepatotoxicity, but some recent studies with IBD patients do not describe any case of liver injury during the follow-up [33]. Probably the main limitation of studies evaluating drug-induced liver toxicity is related with diagnosis, due to the absence of speci ic markers or tests. Therefore, the diagnosis relied entirely on circumstantial evidence and only in the cases of relapse after rechallenge we had the certainty that azathioprine or mercaptopurine were the offending drug [44].Liver biopsy is an invasive procedure with signi icant morbidity and was not performed routinely to all patient presented with abnormal LFTs. However, liver biopsy is not required to establish the diagnosis of druginduced liver toxicity. Based on the absence of histological con irmation and in the fact that an important percentage of patients were able to tolerate full-dose therapy, we cannot assert that we are handling with a true hepatotoxicity which implies hepatocyte damage rather than a form of tolerance. It is important to remark that we ruled out other causes that might have explained the liver injury as well as alcohol or hepatotoxic drugs intake, but we should be aware that the patient could be hiding the consumption of illegal drugs or herbal remedies [45]. In their study Paul, et al. reported that ATI levels were associated with loss of response to in liximab. The ELISA used in their study was able to assess ATI levels independently from IFX trough concentrations. This may partly explain the discrepancy between our results and previous reports [46,47]. Immuno-monitoring has been increasingly recognized as a useful tool to explore an immune basis behind LOR to anti-TNFa therapy. It can be used alongside other biochemical predictors of LOR such as CRP and faecal calprotectin [48]. In their one retrospective study Tighe, et al. 2017 analyzed patients who previously had stand-alone anti-TNFa trough and antibodies measured [38]. They aimed to see whether these stand-alone anti-TNFa trough and antibody levels would be useful in predicting future outcomes [38]. Similar to other studies, a signi icant number of their cohort treated with anti-TNFa had a negative outcome (twenty-seven percent 20/74) [14,49], it is important to remark that we ruled out other causes that might have explained the liver injury as well as alcohol or hepatotoxic drugs intake, but we should be aware that the patient could be hiding the consumption of illegal drugs or herbal remedies [50]. It is worth noting some considerations related to the clinical course of thiopurineinduced liver injury. At irst it is important to point out that a small percentage of patients, less than ive percent presented with a slight elevation of LFTs that did not have

Discussion
This review includes seven studies which are prospective observational studies that examined the ef icacy and safety of biologics in IBD patients. Warman, et al. 2015 discussed therapeutic drug monitoring of in liximab is not common care in the daily practice of a gastroenterologist treating IBD. Lack of effectiveness or the manifestation of side effects may often be encountered by dose or interval adjustments before turning to therapeutic drug monitoring. Therefore, these trough levels are not based on a standard regime, as we see in patients newly started on in liximab, but might be in luenced by the adjustments [41]. Their study provided insights into in liximab trough levels in our IBD cohort in which dose adjustments had already been performed and whether there is still an association with remission [39]. clinical implications: the abnormalities in liver chemical tests returned to normal values during the follow-up and was not necessary to adjust dose of immunomodulator [51]. As with other drugs, thiopurine induced liver injury occurred more frequently within the irst months of treatment, 50% of cases within the irst 3 months [52]. Moreover, treatment withdrawal because of hepatotoxicity occurred in most of cases, 75%, during this period of time [53]. Despite this, in some cases the liver injury was only detected after a long period of follow-up leading to therapy withdrawal [54]. This inding is surprising because the long delay makes the role of the suspected drug unlikely; the explanation of this event could be related to a cumulative effect of the metabolites on liver or to the con luence of multiple factors that could be triggers of an autoimmune liver injury. We found acute hepatocellular hepatitis in eighty seven percent of patients, in contrast with previous descriptions that considered pure cholestasis as the typical pattern [55]. In all cases LFTs returned to normal values and no chronic disease was detected [56]. When hepatotoxicity occurred, the treatment was withdrawn in thirty one percent of patients, but an important percentage, forty four was able to continue on full dose of thiopurine once the dose was temporarily adjusted [57]. This group of patients had a dose-dependent hepatotoxicity rather than an immune-allergic hepatitis [58]. The rationale about how these patients were able to return to full doses of thiopurinic immune-modulators may be theoretically explained by the con luence of multiple factors in the onset of hepatotoxicity: dose of immunomodulator, concomitant treatment, quality of nutrition, drug interaction, etc.. [59].  postulated that the variation in injury pattern could be secondary to variables such as concomitant medications or dosage of medications [60]. Dosage of TNF-antagonists did not correlate with liver injury in our case series [61]. Amongst our patients, Subject 1 received therapy with high dose in liximab (10 mg/kg every 8 weeks) when hepatotoxicity was documented. However, Subjects 2 and 3 received standard doses of in liximab (5 mg/kg every 8 weeks) and standard induction dosing of adalimumab (160 mg at week 0, 80 mg at week 2, and 40 mg every other week thereafter), respectively, when liver injury was noticed. Latency time to the development of liver toxicity was also variable. Some cases, liver toxicity developed after eighteen months of in liximab, whereas toxicity developed within three months in some cases [62]. Hepatotoxicity was not related to any particular TNF-antagonist, and patient age also varied among our three patients [63]. The variability of histology, dosage, time to toxicity, and presence of concomitant medications, in our patients as well as in review of published cases, highlights the idiosyncratic nature of this drug-induced liver injury [1]. As clinician awareness of this entity increases, and more cases are detected, hopefully distinct patterns of injury will be delineated so that early detection can take place and fulminant liver failure can be prevented [64].

Quality of the evidence
Two of the included studies were judged to be at low risk of bias [38,40]. Four studies were rated at unclear risk of bias for random sequence generation and allocation concealment [33,35,38,60]. Another two studies were found at unclear risk of bias for blinding [33,36] and one study at unclear risk of bias for incomplete outcome data [39].

Potential biases in the review process
A comprehensive literature review to help ensure that we included all relevant studies. Two review authors independently assessed for study inclusion, extracted data and assessed for risks of bias. The main limitation of this review is the lack of data available for endoscopic and histological end points.

Conclusion
This study summed up the broad information of incidences of biologic related hepatotoxicity in IBD patients in clinical practice setting. When hepatotoxicity occurred, the treatment was withdrawn in thirty one percent of patients, but an important percentage, forty-four was able to continue full dose of thiopurine once the dose was temporarily adjusted. This group of patients had a dose-dependent hepatotoxicity rather than an immunologic hepatitis. Further studies are required to look into dose related hepatotoxicity in different stages of in lammatory bowel diseases especially patients who underwent surgical interventions.