Consensus guidelines: best practices for detection, assessment and management of suspected acute druginduced liver injury occurring during clinical trials in adults with chronic cholestatic liver disease

Background: Improved knowledge of the molecular pathophysiology and immunopathogenesis of cholestatic liver diseases in recent years has led to an increased interest in developing novel therapies. Patients with cholestatic liver disease often require different approaches to assessment and management of suspected drug-induced liver injury (DILI) compared to those with healthy livers and those with parenchymal liver diseases. At present, there are no regulatory guidelines or society position papers, that systematically address best practices pertaining to detection of DILI in these patients.Aims:To outline best practices for detection, assessment and management of suspected acute DILI during clinical trials in adults with the cholestatic liver diseases -Primary Biliary Cholangitis (PBC) and Primary Sclerosing Cholangitis (PSC).Methods: This is one of the several papers developed by the IQ DILI Initiative, which is comprised of members from 16 pharmaceutical companies, in collaboration with DILI experts from academia and regulatory agencies. The contents are the result of an extensive literature review, as well as in-depth discussions among industry, regulatory and academic DILI experts, to achieve consensus recommendations on DILIrelated issues occurring during clinical trials for cholestatic liver diseases.Results:Recommended best practices are outlined pertaining to hepatic eligibility criteria, monitoring of liver tests, approach to a suspected DILI signal, and hepatic discontinuation rules.Conclusions: This paper provides a framework for the approach to detection, assessment and management of suspected acute DILI occurring during clinical trials in adults with cholestatic liver disease.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

## | introduc ti on
Cholestatic liver diseases comprise many conditions of dysfunctional bile flow and/or formation, which can lead to progressive hepatobiliary damage and its complications. While the primary pathogenic mechanisms are yet to be fully elucidated, improved knowledge of the molecular and cellular pathophysiology and immunopathogenesis of cholestatic liver diseases in recent years has led to a resurgence of interest to develop new therapies. As such, a number of drugs, some of which are novel, are currently undergoing clinical evaluation. This increase in clinical development programs for cholestatic liver diseases. has brought to light the fact that there are numerous challenges faced in detecting, assessing, and managing suspected acute drug-induced liver injury (DILI) occurring during these trials (Box 1). To start with, the literature surrounding drug DILI occurring in patients with underlying cholestatic liver diseases is scarce. There are no regulatory guidelines or society position papers that systematically address best practices pertaining to detection of DILI in these patients.
Furthermore, patients with these conditions likely require different approaches to the assessment and management of suspected DILI, compared to patients with normal livers, or patients with parenchymal liver diseases such as viral hepatitis or non-alcoholic steatohepatitis (NASH). Thus, standard liver biochemical monitoring and stopping rules in the face of acute drug-associated liver injury may not be applicable to those with underlying cholestatic diseases. As there are a growing number of clinical trials assessing drugs for the treatment of cholestatic liver diseases, there is a great unmet need for consistent, evidence-based recommendations for best practices pertaining to suspected DILI in such patients. This consensus paper focuses on best practices for detection, assessment, and management of suspected acute DILI occurring during clinical trials in adults with cholestatic liver diseases.
The IQ DILI Initiative was launched in June 2016 within the International Consortium for Innovation and Quality in Pharmaceutical Development (also known as the IQ consortium) to reach consensus and propose best practices on topics related to clinical DILI.The IQ Consortium is a science-focused, not-for-profit organisation addressing scientific and technical aspects of drug development and is comprised of 38 pharmaceutical and biotechnology companies. The IQ DILI Initiative is an affiliate of the IQ Consortium, comprised of 17 IQ member companies, focused on establishing best practices for monitoring, diagnosing, managing, and preventing DILI. This publication is based on an extensive literature review, and the consensus achieved in carefully structured discussions between IQ DILI members and academic and regulatory experts. The recommendations are based on the opinions of the authors, and do not imply a regulatory guidance or mandate. This paper will be limited to a discussion of detection, assessment and management of acute hepatocellular and cholestatic DILI in adults with Primary Biliary Cholangitis (PBC) and Primary Sclerosing Cholangitis (PSC) without advanced liver disease (Child Pugh B, and C) who are participating in clinical trials. Due to the scarcity of data in the published literature, other types of acute DILI and chronic forms of DILI (eg, vanishing bile duct syndrome or nodular regenerative hyperplasia) will not be discussed in this paper. However, it is strongly recommended that drug developers and investigators remain mindful of these less common types of DILI that could arise during drug development. While a complete discussion of the detection, assessment and management of DILI occurring in patients with paediatric cholestatic liver diseases is beyond the scope of this paper, there are many salient features specific to these patients which will be briefly addressed. Finally, a discussion of causality assessment is beyond the scope of this publication and will not be addressed in detail. A full discussion of 2. It is unknown if patients with cholestatic liver disease have an increased susceptibility to DILI or worse outcomes when DILI occurs, compared with those with normal livers or patients with hepatocellular liver disease.
3. There are no regulatory guidelines or society position papers that systematically address monitoring and stopping criteria for patients with cholestatic liver disease who develop a hepatocellular or cholestatic DILI signal.. Liver biochemical monitoring and stopping rules that are utilized for patients with normal livers or patients with hepatocellular liver disease may not be applicable to those with cholestatic liver diseases.. The upper limit of normal for alkaline phosphatase varies among laboratories and some laboratories report separate upper limit of normal values for different sex and age groups.. Cholestatic DILI may be indistinguishable from progression of the underlying cholestatic liver disease both clinically as well as histologically. biochemical tests often fluctuate in patients with PSC possibly due to intermittent blockage of strictured bile ducts by biliary sludge or small stones confounding evaluation for DILI.. The natural course of PSC characteristically includes episodes of cholangitis which may mimic DILI biochemically, making detection and assignment of causality challenging.. The optimal approach of applying Hy's Law in clinical trials in patients with cholestatic liver disease is still a matter of debate, and clear guidelines and definitions are lacking.. Establishing liver biochemical test monitoring and stopping rules based solely on multiples of upper limit normal may result in inconsistent and/or incorrect evaluation of the hepatotoxicity of the candidate drug. these topics will be the focus of subsequent papers from the IQ DILI Initiative.

## | defining the pat tern of d ili in patients with chole s tatic liver dise a se
The three predominant patterns of liver blood test elevations used to differentiate and classify the types of DILI are hepatocellular, cholestatic and mixed. The international criteria for liver toxicity, established by the Council of International Organizations of Medical Sciences (CIOMS) in 1990, defined the pattern of liver injury by using an R value,The ratio is 5 in acute hepatocellular injury, <2 in cholestatic liver injury, and between 2 and 5 in mixed hepatocellular-cholestatic liver injury.However, it has been recommended that for patients with underlying liver disease and baseline abnormal hepatic biochemical indicators, R values derived from serum test results at the peak of acute drug-associated liver injury should be calculated using the mean baseline values obtained prior to exposure to the suspect drug, instead of the ULN.This should then be compared with the R value after drug exposure. It should be emphasised that the utility of the R value in patients with underlying cholestatic liver disease has not been defined or systematically evaluated and therefore, needs to be established.

## | consensus recommendations 1 & 2
1. The utility of the R value in patients with cholestatic liver disease has not been demonstrated and therefore, needs to be established 2. If the R value is used to define the pattern of DILI in patients with PBC or PSC, it is recommended that the R value of the suspected event be compared to the baseline R value of the underlying disease, although the significance of a shift from the baseline value has not been assessed, and therefore, needs to be established.

## | are patients with chroni c chole s tati c liver d is e a s e at in cre a s ed ris k for d ili?
Experts in the field of DILI generally consider that patients with underlying chronic liver disease, do not appear to have an increased susceptibility for DILI compared with those patients without chronic liver disease.However, should DILI occur, patients with chronic liver disease have an increased incidence of morbidity and mortality compared with those with healthy livers.Of note, patients with PBC and PSC were excluded in the drug-induced liver injury network (DILIN) studies,and thus, findings from the drug-induced liver injury network may not be applicable to patients with cholestatic liver disease. Finally, two studies noted cases of an increased likelihood of hepatotoxicity when rifampicin was given to patients with PBC to treat pruritus to the incidence reported when rifampicin was given to those without underlying chronic liver disease noted in other studies.These studies were not placebo-controlled and consisted of case reports or retrospective chart reviews. Thus, a definitive conclusion as to the increased risk of hepatotoxicity due to rifampicin in patients with PBC cannot be drawn.

## | consensus recommendations 3-6
3. It is unknown if patients with chronic cholestatic liver disease have an increased susceptibility to DILI 4. The outcome of DILI in patients with cholestatic liver disease has not been specifically studied, but until proven otherwise, it is a good practice to consider that acute DILI occurring in patients with cholestatic liver diseases, especially those with advanced liver disease, is associated with worse outcomes.

## 5.
Studies are needed to evaluate if patients with cholestatic liver diseases are more susceptible to DILI than those with normal livers, or patients with hepatocellular liver disease.
6. Studies are needed to evaluate if DILI occurring in patients with cholestatic liver diseases is associated with worse outcomes

## | primary b iliary chol ang itis
PBC is a chronic autoimmune cholestatic liver disease in which the small and medium-sized intrahepatic bile ducts are the target of destruction leading to cholestasis, portal inflammation, fibrosis and cirrhosis.The diagnosis of PBC is made when two of the following are present: an elevated ALP, a positive antimitochondrial antibody (AMA) and/or consistent liver histology.Prevalence is estimated at 1.9 to 40.2 per 100 000 people.Approximately 90% are Caucasian women, and the median age at presentation is 52 years.While the rate of disease progression may vary individually, PBC is characterised by a slow steady progression occurring over many decades.With the approval of ursodeoxycholic acid in 1997, the natural history of PBC has improved and this drug remains a first line treatment for PBC.

## | consensus recommendations 15-18
15. Clinically significant abrupt elevations in hepatic biochemical tests should prompt accelerated monitoring and evaluation for potential DILI as detailed in 16. If cases of suspected DILI marked by isolated increases of bilirubin, especially direct bilirubin, above baseline and/or other clinical or laboratory abnormalities that point to worsening of liver function occur in a clinical trial, an unblinded safety assessment of subjects with these findings should be performed by an external advisory panel of experts. Consideration should be given to temporarily pause the trial. In assessing whether the trial should be allowed to continue, the panel should also evaluate all pertinent liver safety data connected to the drug development program. Consideration by the panel for an option to change the study protocol in order to mitigate DILI risk in the clinical trial may also be warranted.
17. An episode of DILI leading to hepatic decompensation in a study subject should trigger permanent drug discontinuation 18. When it is determined that new elevations in liver tests are due to progression of PBC to cirrhosis or hepatic decompensation, it is prudent to determine exposure levels of the investigational product, as a dose reduction or change in dosing regimen may be deemed necessary to avoid toxic drug levels and subsequent DILI.

## | ob e ti choli c acid and p otential hepatotoxi cit y
Adherence to instructions outlined in the clinical trial protocol, as well as the prescribing regimen detailed in the approved product label to modify study drug dosing or avoid treatment altogether in the presence of defined liver abnormalities remains an important aspect for preventing DILI in patients with chronic liver disease.The mechanism of action of potential obeticholic acid hepatotoxicity is unknown.A case report of a patient with Child Pugh A cirrhosis due to PBC who developed clinical and histologic cholestatic hepatitis two months after stopping a higher than recommended dose of ursodeoxycholic acid (23mg/kg) and simultaneously starting obeticholic acid has recently been reported.The authors of this article postulated that this event was triggered by an increase in hydrophobic bile acids in addition to a reduction in bile flow, leading to cholestatic hepatitis. In the phase 2 obeticholic acid study in patients with PBC and an inadequate response to ursodeoxycholic acid, Hirschfield and colleagues reported jaundice The specific interval between tests should also be determined based on the patient's clinical condition. d The study subject will require close follow-up monitoring to exclude recurrence of liver injury after restarting the study drug.
in two patients.While the fibrosis stage of these patients was not stated in the publication, a similar mechanism of action might be postulated as these patients were on a higher dose (50mg) The study subject will require close follow-up monitoring to exclude recurrence of liver injury after restarting the study drug.

## | consensus recommendations 19-21
19. Dose adjustment recommendations as stated in the obeticholic acid (Ocaliva  ) product label should be followed in any clinical trial that is investigating obeticholic acid as part of a combination therapy.

## 21.
To determine whether subjects with advanced liver disease have been optimally dosed with any study drug that undergoes hepatobiliary clearance, a pharmacokinetic analysis of the parent compound and its metabolites should be performed.

## | us e of ne w nad ir liver value s and s topping rule s in pbc clini c al trial s
While HCV, being a hepatocellular disease, and PBC, being a cholestatic disease, differ significantly, some lessons learned from HCV drug development can be applied to drug development for new PBC therapies. In particular, since it was noted that normalisation or significant reductions of ALT values occurred within the first few weeks of direct acting antiviral therapy for HCV,it was recommended that this new ALT nadir value be used instead of baseline ALT levels, to evaluate potential DILI.As such, an elevation of ALT and/or AST >5 baseline or >5 the nadir value occurring early after treatment initiation, was used to trigger drug discontinuation in some HCV trials.The specific interval between tests should also be determined based on the patient's clinical condition. d The study subject will require close follow-up monitoring to exclude recurrence of liver injury after restarting the study drug.
ALP were achieved and stabilised by 1-3 months of therapy.Although not assessed in any trials, the degree of reduction in ALT and ALP to achieve this nadir value was approximately a mean reduction of 15% from baseline value.Of note, this reduction is not as steep and impressive as the reduction of ALT achieved in HCV trials in response to therapy which triggered the nadir recommendation.While total bilirubin levels also decrease in response to therapy, change from baseline is mild due to the fact that most subjects enter PBC trials with a total bilirubin < 2 gm/dL.Algorithms for monitoring, interrupting and stopping drug for the management of patients with PBC in clinical trials are illustrated in However, the specific interval between the tests should also be shortened if the patient's clinical condition warrants a rapid response by the investigator.

## | s pecial con s ider ati on s for c ausalit y a ss e ss ment of p otential d ili e vents in patients with pbc
Causality assessment in patients with PBC participating in a clinical trial can be challenging. While a full discussion is beyond the scope of this paper, a few points specific to PBC will be discussed. When elevated liver biochemistries occur during a PBC clinical trial, it is also important to rule out the onset of PBC/autoimmune hepatitis overlap syndrome. Clues that a patient may have developed an overlap syndrome includes a new rise in ALT >5 ULN, which is uncommon for PBC alone.An immunoglobulin G >2 ULN and/or anti-smooth muscle antibody titre >1:80 is characteristic of overlap syndrome and these tests should be obtained for evaluation to assist in differentiating from potential DILI. As drugs are known potential triggers for idiopathic autoimmune hepatitis, it is important to be aware that DILI can also be associated with high antinuclear antibody and anti-smooth muscle antibody titres, as well as high immunoglobulin G levels.In addition, there is also a subset of au-. PBC/autoimmune hepatitis overlap syndrome, as well as idiopathic autoimmune DILI should be considered as potential causes for the new onset of elevated liver biochemistries. However, it must be kept in mind that a new-onset overlap syndrome could be drug-induced.. A liver biopsy should be considered as part of causality assessment as it may provide clues that assist in differentiating autoimmune hepatitis from DILI. The possible need for a liver biopsy to determine causality or to assist with the clinical management of a case of concern, should be addressed in the protocol, as well as the informed consent.

## | consensus recommendations 26-28
28. Additional causes of clinically significant abrupt elevations in liver blood tests including, but not limited to, acute and chronic viral hepatitis (hepatitis A-E), cholelithiasis and alcohol, other drugs both prescribed and over-the-counter herbs and supplements, should be also ruled out. Aetiology is unknown but likely multifactorial, and includes, but is not limited to influences related to genetic factors, the environment, immunity, gut-lymphocyte homing and toxic bile acids.Higher doses of ursodeoxycholic acid at 28 to 30 mg/kg/d have been associated with an increased mortality compared with placebo.Although commonly used off-label at a dose of ~ 20 mg/kg/d,there has not been a definitive recommendation in society guide- The natural history of PSC is highly variable and needs to be studied in further detail. Its course is characteristically marked by fluctuating hepatic blood tests, symptoms and bouts of cholangitis.Thus, determining the aetiology of abrupt elevations in liver biochemistries and differentiating an episode of acute cholangitis from DILI in patients with PSC can be challenging. Aminotransferase levels are elevated in the majority of patients (2-5 ULN) but can also be in the normal range. However, peak aminotransferase levels are rarely above 300 U/L.

## | primary scleros ing chol ang itis

## | hepati c eli g ib ilit y criteria for patients with psc

## | consensus recommendations 29-38
29. Alkaline phosphatase >10 upper limit normal should be set as

## | special considerations for causality assessment of potential dili events in patients with psc without advanced cirrhosis (child pugh b, c)
The

## | monitoring of liver b i o chemis trie s and d ili de tec ti on in psc clinic al trial s
Monitoring and stopping rules for liver test elevations from PSC clinical trials and publications were not readily located in the public domain for review. Suggested algorithms There is no single definitive prognostic biomarker for measuring PSC disease progression and there is a lack of consensus over clinically relevant endpoints in PSC clinical trials. However, ALP is the most commonly utilised surrogate biomarker and as such, is typically the primary endpoint in most early phase PSC treatment trials.Thus, a reduction of ALP has been utilised as an indicator of treatment response and has been noted to occur by week 12 in many trials and as early as week 4 of treatment in some.However, the specific interval between the tests should also be based on the patient's clinical condition.

## | chole s tati c d ili

## | additional cons ider ations for clini c al trial s of pbc and psc
As between 5%-10% of the population has Gilbert's Syndrome, it is likely that some patients enrolled in a cholestatic liver disease trial will also have this hereditary condition characterised by intermittent unconjugated (indirect) hyperbilirubinaemia in the absence of hepatocellular disease.Total bilirubin levels in Gilbert's Syndrome are usually mildly elevated, but rarely greater than 4-5 mg/dL.Gilbert's Syndrome is caused by a reduction of the level of the enzyme uridine 5'-diphospho--glucuronyl-transferase to 20-30% of its normal amount which results in impaired conjugation of bilirubin with glucuronic acid.It is important to accurately identify Gilbert's Syndrome in clinical trials, especially clinical trials in cholestatic liver diseases, as misdiagnosis may result in unnecessary diagnostic testing, incorrect assignment of causality, as well as drug interruption or discontinuation. Diagnosis is confirmed by calculating the amount of conjugated bilirubin, which should be less than 20%-30% of the total bilirubin, in the absence of haemolysis.It should be noted that the terms "direct" and "conjugated" hyperbilirubianemia, are regu-
larly, yet incorrectly, used interchangeably. Direct bilirubin includes both the conjugated fraction, as well as delta bilirubin, which is bound to albumin, and thus, has a half-life of approximately 21 days.
It is the presence of delta bilirubin that causes direct hyperbilirubinaemia to persist.If the aetiology of prolonged hyperbilirubinaemia is uncertain, a breakdown of the direct bilirubin fraction to conjugated and delta bilirubin should be considered.
When hyperbilirubinaemia is due to DILI, the fraction of direct bilirubin should be measured, and is usually greater than 35%.When the diagnosis is unclear, genetic testing for DNA mutations of uridine 5'-diphospho--glucuronyl-transferase should be considered.

## | algorithm for monitoring and manag ement of p oss ib le hepato cellul ar or chole s tati c d ili in pbc and psc clini c al trial s in patients with normal or ele vated ba s eline alt
Hy's law identifies hepatotoxic drugs with a potential to cause idiosyncratic severe hepatocellular liver injury.

## | paed iatri c chole s tati c liver dise a se
A comprehensive review of assessment and monitoring of DILI in paediatric cholestatic liver diseases is beyond the scope of this paper. There is great interest in developing novel therapies for paediatric cholestatic liver diseases, many of which have an urgent unmet medical need. As such, clinical trials for many of these diseases with varied pharmacologic interventions are ongoing and more are under consideration.A full discussion of this topic will be the focus of a subsequent paper from the IQ DILI Initiative. However, a few salient points will be mentioned. 2. In patients with PSC, two consecutive alkaline phosphatase and aminotransferase measurements should be obtained at least >2 weeks apart during the screening period. If values vary widely (eg, >30%), enrollment should be postponed until further screening demonstrates stable values, or the etiology is identified and corrected.
3. After treatment initiation, a subject's new treatment-related stable nadir level of alkaline phosphatase and/or alanine aminotransferase, as opposed to the pre-treatment baseline level, should be used as a frame of reference to monitor and assess potential DILI.
Application of the new nadir value should be considered when a >50% reduction from baseline is achieved.
4. Monitoring and stopping rules based on multiples of upper limit normal, baseline and nadir values of alkaline phosphatase and alanine aminotransferase, baseline values of total and direct bilirubin, and liver-related or immunologic-related symptoms should be followed for clinical trials of patients with PBC and PSC.
5. The optimal approach of applying Hy's Law in clinical trials in patients with cholestatic liver disease is still a matter of debate, and clear guidelines and definitions are lacking. However, using the baseline ALT value or treatment-related new nadir level and a combination of multiples of ULN, in conjunction with an elevated bilirubin may lead to a more accurate assessment.
6. In patients with PBC, PBC/autoimmune hepatitis overlap syndrome, as well as idiopathic autoimmune DILI should be considered as potential causes of a new onset of elevated liver biochemistries.
7. When it is determined that new elevations in liver tests are due to progression of cholestatic liver disease to cirrhosis, it is prudent to determine exposure levels of the investigational product, as a dose reduction or change in dosing regimen may be deemed necessary to avoid toxic drug levels and subsequent DILI.
8. Patients entering clinical trials utilizing obeticholic acid or any of the newer farnesoid X receptor agonists, who have advanced liver disease or patients determined to have progressed to advanced liver disease during the course of the trial, should be monitored on a more frequent basis to evaluate for signs of hepatic decompensation.
9. If cases of suspected DILI marked by isolated increases of bilirubin, especially direct bilirubin, above baseline and/or other clinical or laboratory abnormalities that indicate worsening liver function occur, or have no alternative causal explanation an unblinded safety assessment of subjects with these findings should be performed by an external advisory panel. A temporary trial pause should be considered. Study drug can be restarted only if another etiology is identified and liver enzymes return to baseline.
10. An episode of DILI resulting in hepatic decompensation should trigger permanent drug discontinuation.
the normal ranges of common liver tests including total bilirubin, aminotransferases, and ALP from early infancy through the pubertal growth spurt. In addition, certain hereditary cholestatic liver diseases in infants and children are not associated with the characteristic rise in GGT that are seen in PBC or PSC and cannot be relied upon as a marker of cholestatic injury.During growth in normal paediatric study subjects, ALP levels are affected by fluctuations of the enzyme derived from bone. Changes of ALP in paediatric patients are also typically observed with vitamin D deficiency. Nutritional problems including fat soluble vitamin deficiency are very common and may be difficult to completely correct in paediatric cholestatic disease.The clinical and biochemical course of the varied monogenic defects in bile secretion machinery that are uniquely seen in children are quite distinct from each other and thus need to be considered individually. As such, DILI monitoring and study drug stopping criteria designed for adult cholestatic liver diseases cannot simply be applied to paediatric cholestatic liver diseases. The ontogeny of intrahepatic enzymes and transporters also factor into the biochemical phenotype of infantile and early childhood paediatric cholestatic liver disease, another factor which needs to be considered in the development of guidelines for these study populations.

## | con clus ion
The number of drug development programs for cholestatic liver disease, particularly PBC and PSC, has grown considerably over the last few years. Patients with these diseases often require different approaches to suspected DILI detection, assessment and management. compared to patients with healthy livers or patients with parenchymal liver disease. This paper highlights the challenges faced and provides consensus recommendations for best practices on this topic based on collaborative work of the IQ DILI initiative and DILI experts from academia, and the Food and Drug Administration.
However, there are still many gaps to fill, and questions to be answered, underscoring the need for further research in this important and complex area.

## Ack n owled g em ents

## Declaration of personal interests