Phase 2b Open-label Randomized Controlled Trial to Evaluate the Ecacy, Safety and Tolerability of N-acetylcysteine in Reducing Adverse Drug Reactions among Adults Treated for Multidrug-resistant Tuberculosis in Tanzania. (Trial Acronym NAC Trial).

Background: Adverse drug reactions (ADRs) frequently occur in patients using second-line antituberculosis medicine for treatment of multidrug resistant tuberculosis (MDR-TB). ADRs contribute to treatment interruptions which can compromise treatment response and risk acquired drug resistance to critical newer drugs such as bedaquiline, while severe ADRs carry considerable morbidity and mortality . N-acetylcysteine (NAC) has shown promise in reducing ADRs for medications related to TB in case series or randomized controlled trials in other medical conditions. We therefore designed a pilot clinical trial to study the protective effect of NAC among people treated for MDR-TB with second-line anti-TB medications. Methods: This is a phase 2b randomized open label clinical trial with 3 treatment arms including a control arm , an interventional arm of NAC 900mg daily , and an interventional arm of NAC 900mg twice-daily administered during the intensive phase of MDR-TB treatment. Patients initiating MDR-TB treatment will be enrolled at Kibong’oto National Center of Excellence for MDR-TB in the Kilimanjaro region of Tanzania . The minimum anticipated sample size is 66 ; with 22 participants in each arm. ADR monitoring will be performed at baseline and daily follow-up over 24 weeks including blood and urine specimen collection for hepatic and renal function and electrolyte abnormalities, and electrocardiogram. Sputum will be collected at baseline and monthly thereafter and cultured for mycobacteria as well as assayed for other molecular targets of Mycobacterium tuberculosis . Adverse drug events will be analysed over time using mixed effect models. Mean differences between arms in change of the ADRs from baseline (with 95% condence intervals) will be derived from the tted model. Discussion: that treatment outcomes for multidrug regimens that prolonged treatment durations.


Background and rationale
The crisis of multidrug-resistant tuberculosis (MDR-TB), de ned as point mutations of Mycobacterium tuberculosis (MTB) chromosomes resulting in strains that are resistance to isoniazid and rifampicin, key medicines for the treatment of TB, continues to worsen [1]. In 2019, the World Health Organization (WHO) estimated 484,000 cases of MDR-TB, while approximately 156,000 were enrolled to initiate treatment. This marked a 21% increase in enrolment compared to the 2016 report [2]. With the growing epidemic of MDR-TB, further exacerbated by the COVID-19 pandemic [3], and a greater proportion of people accessing treatment, there is further urgency to assure treatment regimens are tolerable and completed without interruption which poses risk to individual outcomes and M. tuberculosis strains with ampli ed drug resistance [4]. Despite the priority for tolerable regimens, medicines used to treat MDR-TB are referred to as "second-line" because of reduced potency and a worse side effect pro le [5]. Regimens are constructed of 4-6 drugs based on the susceptibility pro le of the infecting M. tuberculosis strain, drug-drug interactions or individual contraindications, and supply chain availability [6]. New and repurposed drugs have improved the e cacy and shortened the duration of MDR-TB treatment but those medications have signi cant and often overlapping toxicities [7]. Based on data from controlled trials and large operational studies, the WHO has recently prioritized bedaquiline, linezolid, newer generation uoroquinolones (moxi oxacin or levo oxacin), and clofazimine for the treatment of MDR-TB as well as consideration of other new agents such as delamanid and conventional anti-TB drugs such as cycloserine, pyrazinamide, ethionamide/prothionamide and ethambutol to complete a multi-drug regimen [8]. While medications requiring intravenous or intramuscular injection are no longer preferred, there are some uncommon clinical scenarios where TB treatment programs or patients themselves may opt to include an injectable aminoglycoside (amikacin or streptomycin) or a carbapenem with beta-lactamase inhibitor (meropenem/clavulanate or imipenem-cilastin/clavulanate).
No other infectious disease requires treatment strategies of such quantity of drugs, and drug class diversity as MDR-TB, and combined toxicities are not dissimilar to treatment of hematological malignancy. As described elsewhere, the severe adverse drug reactions (ADRs) from medications used to treat MDR-TB include hepatotoxicity, cytopenias, QTc prolongation and cardiac arrhythmia, nephrotoxicity, ototoxicity, peripheral and optic neuropathy, and psychosis [9,10]. Given the combination of drug-classes, including broad spectrum classes such as the uoroquinolones, gastrointestinal side effects are common, and can even confuse the presentation of more serious ADRs including hepatoxicity and lactic acidosis [11]. For example, despite the e cacy of bedaquiline, up to 20.8% of people experience bedaquiline related ADRs, with 7.4% serious. ADRs related to bedaquiline were most frequently gastrointestinal (14%), followed by metabolic disorders (8.5%) and nervous system disorders (8.5%) [12]. Likewise, the inclusion of linezolid in MDR-TB regimen has a signi cant positive effect in improving treatment outcome and reducing mortality, yet the occurrence of ADRs include myelosuppression (33%), neuropathy (30%) whereas other less common ADRs are vomiting, hyperpigmentation and transient visual impairment [13]. Clofazimine is considered safe since the ADRs requiring discontinuation or withdrawal reported have been as low as 0.1% common ADRs are skin discolouration and gastrointestinal side effects with a pooled proportion of 22% [14]. Furthermore, several drugs have overlapping ADRs for instance the uoroquinolones, bedaquiline and delamanid all may cause QTc interval prolongation, and hepatotoxicity [15].
We have designed the following trial to study a promising compound, N-acetylcysteine (NAC), for reduction of ADRs during the course of MDR-TB treatment, which is to our knowledge the rst of its kind with this primary objective for MDR-TB. NAC is a thiol compound and the acetylated form of L-cysteine with the chemical formula C5H9NO3S and molecular weight of 163.2 g/mol. NAC is e ciently absorbed and metabolized primarily by the liver. Absorption provides a large amount of NAC for cellular uptake, deacetylation of cysteine and synthesis of glutathione (GSH). GSH is an intracellular antioxidant that combats the impact of oxidative stress thus protecting the vital cellular components against the dangerous effect of peroxidation. The free sulfyhydryl group in GSH readily scavenges harmful radicals such as reactive oxygen species, peroxides and superoxides to thiyl radical, which rapidly dimerises to form glutathione disul de [16,17]. GHS released from NAC then carriers out its putative protective effect both enzymatically and non-enzymatically. The bene t of NAC on oxidative damage extend to organs such liver, pancreas, kidney, inner ear hair cells, and cells of the immune system. Furthermore, NAC demonstrates anti-in ammatory properties by limiting pro-in ammatory cytokine release, particularly through a NF-kappa beta pathway [18].
NAC has been employed in clinical practice for several decades. It has been used as a mucolytic agent and for the treatment of numerous disorders including paracetamol intoxication, doxorubicin cardiotoxicity, ischemia-reperfusion cardiac injury, acute respiratory distress syndrome, bronchitis, chemotherapy-induced toxicity, heavy metal toxicity and psychiatric disorders [19]. Most relevant to prevention of ADRs from MDR-TB treatment, previous NAC interventions have been trialed in drug susceptible (DS)-TB among primarily Asian populations [20,21]. Baniasadi et al conducted a clinical trial in an older age (³ 60 years) population at higher risk of drug induced liver injury (DILI). The hepatoprotective effect of NAC was signi cant since anti-TB DILI occurred in 12 patients (37.5%) in the control group but none in the NAC group [20]. Farazi et al conducted another NAC trial in 85 patients with age ³ 50 years and treated for DS-TB. Eligible participants were randomly selected to receive NAC 600mg or placebo with standard rifampicin, isoniazid, pyrazinamide and ethambutol (RHZE) treatment. DILI occurred in 14.3% of the placebo group as signi ed by raised serum aspartate transaminases (AST), alanine transaminases (ALT) and bilirubin. Interestingly, the group receiving NAC also had reduced levels of AST, ALT and bilirubin compared to their baseline values [21]. A further meta-analysis by Kranzer et al conducted a review on the e cacy and safety of NAC in preventing aminoglycoside induced ototoxicity and found the weight of evidence supporting the safety and otoprotective effect of NAC when coadministered with an aminoglycoside, even for durations shorter than those used for MDR-TB [22]. Thus, the prior studies in non-MDR-TB populations and among people with drug-susceptible TB provide a strong justi cation for a clinical trial to investigate the effect of concomitant NAC treatment in patients receiving MDR-TB treatment. If NAC allows uninterrupted use of the most e cacious dose and duration while limiting the long-term sequela of MDR-TB treatment, then the trial may indeed contribute to the current ambitious goals set by the global health community for achieving a 90% TB treatment success rate by 2035 [23]. Hence conducting this randomized controlled trial within a MDR-TB programme from a TB endemic country will provide actionable programmatic data with which to determine the eventual role of a NAC intervention.

Objectives
Hypothesis I Administration of oral NAC at a dose of 900mg daily in combination with second-line during treatment of multidrug-resistant tuberculosis (MDR-TB) will protect against occurrence of serious advent events without interfering with the effect of second line anti-TB regimen.

Hypothesis II
Administration of oral NAC at a dose of 900mg twice a day in combination with second-line during treatment of multidrug resistant tuberculosis (MDR-TB) will protect more than the dose of 900 mg daily against occurrence of serious adverse events without interfering with the effect of second line anti-TB

Methods: Participants, Interventions And Outcomes
Study setting Patients will be recruited at one centre, Kibong'oto Infectious Diseases Hospital (KIDH) in Tanzania. The site is experienced in recruitment, hospitalization, safety and e cacy measurement and has the capacity to receive more than 100 MDR-TB patients per year [24]. KIDH has also participated in the International Collaboration for Infectious Diseases Research (ICIDR) consortium to build capacity for MDR-TB trials recruitment and follow-up of a longitudinal cohort of MDR-TB participants through 96 weeks (NCT 03559582). In addition, the KIDH research team has demonstrated the capacity of recruiting DS-TB patients for other trials in the Pan African Consortium for Evaluating Anti-TB Antibiotics (PanACEA) with a remarkably high proportion of retention [25].

Eligibility criteria
Page 7/22 MDR-TB participants will be eligible, if they are able and willing to provide a written informed consent prior to participation, with age range between 18 and 65 years. They should be newly diagnosed with MDR-TB without a history of using or being on MDR-TB treatment. Decisions on composition of the MDR-TB treatment regimen and timing of initiation will be made by the treating clinicians, but study participants will only be eligible if Karnofsky score of ³ 50 de ned as individuals requiring less considerable or frequent medical care. Female participants should not be pregnant as con rmed by urinary pregnant test to ensure homogeneity of the participants.
Other exclusion criteria include people with previous existing pathology which will preclude testing such as severe baseline hearing loss, central nervous system pathology (i.e. major head trauma, meningitis, encephalitis, or brain metastasis,), or untreated mood disorders such as schizophrenia, schizoaffective disorder or psychotic disorder or using psychotherapeutics like imipramine, and escitalopram. Similarly, participants with known comorbid conditions such as severe liver or renal diseases will be excluded.
Who will take informed consent?
Recruitment will take place among individuals to KIDH for MDR-TB treatment. Upon identi cation of a potentially eligible participant, study staff (research nurse or research doctor) will provide information about the study to the participant. As described in greater detail in the study-speci c standard operating procedure, the informed consent process will include detailed review of the study informed consent form (ICF), and will allow time to address any questions or concerns each participant may have, and an assessment of each participant's understanding will be performed before proceeding to the informed consent decision. Illiterate adult patients will have to thumbprint the consent sheet in presence of an impartial witness who will sign the consent sheet in addition. The process will be fully documented and only participants who are able to demonstrate understanding will be asked to provide written informed consent to take part in the study. Written informed consent for study participation must be obtained before any study related procedures are performed. Screening evaluations must be performed within 7 days of entry. Participants screening and enrolment registers will be used to assist with tracking the screening and enrolment process. When informed consent is obtained for the study, a participant identi cation screening (PID) number will be assigned and eligible participants will receive enrolment PID number. For participants who are found to be ineligible for the study, or who do not enrol in the study for any reason, an electronic case report form (eCRF) will be completed to record the screening outcome.
Additional consent provisions for collection and use of participant data and biological specimens Additional consent will be administered for phlebotomy for full pharmacokinetic sampling, which will be performed at 2 weeks after initiation of treatment. The consent will cover week 2 venous blood collection that will be drawn at 1, 2, 6, and 10-12 (late sample per site feasibility) hours and week 8 drawn at 2 and 6 hours after medication administration with attempt by single venipuncture for peripheral IV insertion. Such sampling allows for adequate calculation of serum peak (C max ) and estimate total exposure (AUC) of the MDR-TB drugs in the regimen to determine if NAC co-administration unexpectedly impacts these parameters. A maximum of 7 ml will be obtained in heparinized tubes at each draw as up to 4 drugs will be required to be assayed. Additional consent will be obtained for other baseline specimens like stool, urine and saliva for pre-planned future studies.

Interventions
We will use n-acetylcysteine (NAC) 900mg in the effervescent tablet preparation as study drug. NAC is manufactured by BioAdventex Pharma Inc -Canada based on good manufacturing practice standards. One intervention group will receive NAC at a dose of 1800mg divided twice daily with second line MDR-TB drugs and another intervention group will receive NAC at a dose of 900mg second line MDR-TB drugs. The control group will receive only second line MDR-TB drugs. There will be no restrictions that will be imposed on standard treatment for MDR-TB while NAC is administered.
Participants will stop the use of trial medications if there will be any serious adverse events related to the use of NAC for instance allergic reactions or if a participant opts to withdraw from continuing with research participation. Study nurses will be responsible for observing the participants taking the investigational medicinal product (IMP) during the treatment phase. Study nurses will provide the participants daily IMP and will document administration in the IMP treatment adherence chart. The site trial pharmacist/delegated dispenser will be responsible for dispensing the IMP. Accurate accountability records will be kept by the site to assure that the IMP will not be dispensed to any person who is not a subject under the terms and conditions set forth in this protocol i.e. delivery to site, inventory at site, use by subject, destruction etc. The investigator/designee will immediately inform the sponsor of any quality issues arising with respect to the IMP. The sponsor will take whatever action is required should such a situation arise. The investigator undertakes to use the IMP only as indicated in this protocol. Relevant concomitant care permitted or prohibited during the trial NAC interacts with nitroglycerin resulting in formation of S-nitroso-NAC, which strongly inhibit platelet aggregation whereas the free sulfhydryl donated from NAC can potentiate the systemic, and coronary vasodilator effects of nitroglycerin in patients with acute myocardial infarction or angina pectoris [26,27]. This effect increases the risk of hypotension. Likewise, the sulfhydryl NAC modi es the renin-angiotensin II, possibly by inhibition of angiotensin converting enzyme inhibitors, thus reduces conversion of angiotensin I to angiotensin II [28,29].Through different mechanisms, NAC modulates glutamate and may results in clinically relevant psychopharmacological properties. In an animal model, Costa-Campos et al investigated the combination of NAC with antidepressant drugs [30]. Findings show NAC reduced the potency of imipramine and escitalopram but not those of desipramine and bupropion. Conversely, in the same model NAC potentiates uoxetine. Therefore, participants using imipramine and escitalopram will be excluded while uoxetine may require dose adjustment.
Although there is no concrete evidence on the interaction of NAC with second line anti-TB drugs for MDR-TB, a number of antimicrobial drugs have the potential to exert central nervous system (CNS) effects and many are associated with stimulant, psychotomimetic and epileptogenic properties [31]. For example, uoroquinolones can cause CNS effects mediated by gamma-aminobutyric acid (GABA) antagonism, cycloserine and aminoglycosides use can lead to N-Methyl-D-Aspartate (NMDA) agonism, and linezolid and isoniazid can exert monoamine oxidase (MAO) inhibition. In this trial, participants that will be using the psychotomimetic or epileptogenic agents, they will receive second line anti-TB medication without dose adjustment, however they will be monitored closely according to the protocol.

Outcomes
Primary endpoint Development of all clinical or laboratory-based adverse events at any frequency during the rst six months of MDR-TB treatment Primary end-point is based on Safety and Tolerability Patients will be daily assessed for adverse events including vital signs, physical examinations, routine clinical laboratory tests such as complete metabolic panel, complete blood count and urinalysis, and interval assessment of electrocardiogram and for those using injectable agents, audiometry testing. Screening may be initiated after a written informed consent is obtained. Screening procedures will be performed on multiple days, including on the date of enrolment. For potential participants who do not meet the eligibility criteria, screening may be discontinued once ineligibility is determined. The information will be entered in the case record form to record the screening outcome. Subjects, who following the screening assessments are eligible for the trial and willing to participate, will be randomized/enrolled into the trial and assigned a Randomization Number. Participant will be followed according to the schedule of events as described in Figure 1 Sample size This is a pilot trial to collect information about the effect of NAC that will potentially guide a future larger trial, thus there was no formal power calculation. Therefore, the sample size for the proposed trial will be 20-per arm and thus 60 participants will be enrolled for three arms. However, previously we have found a withdrawal/non-evaluable subject rate from our previous TB clinical trials estimated at 10% [32]. Therefore a total of 66 MDR-TB patients will be recruited for this clinical trial [33].

Recruitment
The onsite research coordinators will immediately review newly diagnosed or referred MDR-TB patients and administer processes for potential eligibility and assessment. Likewise, communication with physicians referring patients for MDR-TB treatment from different centres will eventually sensitize potential participants interested to participate to receive referral to KIDH. This will facilitate recruitment.

Assignment of interventions: allocation
Sequence generation: All patients who give consent for participation and those that ful l the inclusion criteria will be randomized to either the control or the experimental groups in 1:1:1 allocation as per a computergenerated random schedule using permuted blocks of randomization ( Figure 2).

Concealment mechanism
The randomized block size will not be disclosed to ensure concealment and to avoid selection bias. In addition, block size will randomly vary to avoid a participant, treating physician or study staff deducing the next treatment allocation. Details of the randomization block size will not be included in the protocol, but will be provided in a separate document with restricted access.
To prevent selection bias by facilitating enrolment of the comparable participants in each arm, allocation concealment will be ensured. Participants will complete all baseline measurements prior to release of the randomization code. An opaque sealed envelope with printed randomization numbers will be prepared.
For every randomization number a code for a treatment will be assigned.
Primary endpoint (ADRs) will be measured by both clinical assessment and laboratory measurements. To avoid ascertainment bias in the measurement of other endpoints such as adverse events, or performance bias in decision to discontinue or modify treatment, or exclusion/attrition bias in the decision to withdraw from the trial or exclude a participant from analysis, blinding will be implemented. Blinding will be at two levels; the trial participants and health care providers. Health care providers include outcomes assessors (physicians and technicians such as audiologists), data collectors, laboratory staff, nurses and pharmacists.

Implementation
An allocation sequence will be generated by the sponsor representative pharmacist. Site investigators will enroll participants while the site research pharmacist(s) will assign participants to interventions.

Assignment of interventions
This is an open label thus research participants and the investigator team and health care providers will be aware of the assignment. The later includes clinicians, and data collectors.

Data collection and management
All case record forms (CRF) both electronic and hard copy pages will be completed for every participant receiving any amount of IMP. Clinical information will be captured in eCRF while laboratory information will be captured in hard copy CRF. For screening failure participants, a screening failure eCRF will be completed. For subjects who are prematurely withdrawn, the visits up to withdrawal plus the withdrawal and follow-up visits need to be completed.
Source documents are de ned as all information in original records and certi ed copies of original records of clinical ndings, observations, or other activities in a clinical trial necessary for the reconstruction and evaluation of the trial. Source documents will include, but are not limited to, progress notes, electronic data, screening logs, and recorded data from automated instruments.
All source documents pertaining to this trial will be maintained by the investigators. Source documents will be available for trial-related monitoring, audits, Institutional Review Board (IRB) review and regulatory inspections providing authorized persons direct access to source documents.

File management at the Trial Site
It is the responsibility of the investigators to ensure that the trial center les are maintained in accordance with International Good Clinical Practice Guidelines and the ethical principles that have their origin in the Declaration of Helsinki.

Records retentions at the Trial Site
The investigator will retain records and data from the trial for safety reasons and for audit and inspection subsequent to trial completion. The essential documents will be retained according to ICH-GCP guideline.
The sponsor will make nancial provisions for the investigator to deposit the documents at an external site for safekeeping for as long as required by regulations and the sponsor.

Plans to promote participant retention and complete followup
Although the site has experience with retaining up to 100% of research participants in longitudinal trials, refresher training of research staff will be conducted to maintain the enthusiasm and perseverance of research staff but also, high morale, and compassion to engage and relate with patients. We have found this an important strategy in achieving high retention rates.

Data management
CRFs will be lled in a timely, accurate and legible manner. Electronic-CRF will be populated in the database while the laboratory CRF entries will be veri able to source documentation other than the CRF.
The CRFs will be lled electronically, in a timely, accurate and legible manner into the Research Electronic Data Capture (REDCap), a highly secured web-based application to capture data for clinical research. CRF entries will be veri able to source documentation other than the CRF. Site Standard Operating Procedures will be adhered to for all clinical and bioanalytical activities relevant to the quality of the trial. Subject compliance will be monitored throughout the trial. The investigator will be signing and date any test results to verify that the results have been reviewed. The investigator may appoint other sub-investigators to assist with the trial. However, the lead investigator maintain responsibility for the trial and will supervise the sub-investigators. Written IEC/IRB approval will be obtained prior to involvement in the trial. The investigator will ensure that all site personnel are adequately trained in GCP, the protocol, IB and all trial procedures and requirements.
The study will be monitored to verify that the rights and well-being of human subjects are protected; that trial data are accurate, complete and veri able with source data; and that the trial is conducted in compliance with the protocol, International GCP, the ethical principles that have their origin in the Declaration of Helsinki and the applicable regulatory requirements.
Monitors assigned by the sponsor will conduct regular site visits for the purpose of monitoring various aspects of the trial. Visits will take place within a predetermined interval, but this may vary during the course of the trial. The investigator and site staff will allow the trial monitor and authorized representatives of the sponsor to inspect all CRFs, written informed consent documents and corresponding source documents (e.g. original medical records), subject records and laboratory raw data, and (2) access clinical supplies, dispensing and storage areas. The investigator and site staff will also assist with monitoring activities if requested and provide adequate time and space for monitoring visits. The monitor will query any missing, confusing, spurious, or otherwise ambiguous data with the investigator. All queries will be resolved in a timely manner. A monitoring log will be maintained recording each visit, the reason for the visit, the monitor's signature and investigator or designee's con rmation signature.

Con dentiality
All site staff, the sponsor, and any sponsor representatives will preserve the con dentiality of all subjects taking part in the trial, in accordance with International GCP, applicable local legislation/regulations. Subject to the requirement for source data veri cation by the trial personnel by reference to the subject's notes, con dentiality of all subject identities will be maintained. Only subject trial number and initials will be used on the CRF and in all trial correspondence, as permitted. No material bearing a subject's name will be kept on le by the sponsor. The written informed consent will contain a clause granting permission for review of the participants' source data.
Plans for collection, laboratory evaluation and storage of biological specimens for genetic or molecular analysis in this trial/future use NA Statistical methods Statistical methods for primary and secondary outcomes The primary e cacy analysis will be conducted using laboratory measurement. Both Modi ed Intent to Treat (MITT) and a Per Protocol (PP) analysis will be performed.
The primary e cacy endpoint is the incidence of ADRs in the rst six months of MDR-TB treatment. The primary e cacy analysis in the treatment groups will include two comparisons, a superiority comparison of each of the 2 experimental NAC arms with the standard treatment arm.
The difference in the proportion of patients with ADRs (as de ned by the primary e cacy endpoint) between each treatment arm and control arm will be calculated with 95% con dence interval using standard methods. In addition, hearing threshold level will be analysed over time using mixed effect models to account for the longitudinal nature of the data. Mean differences between arms in change from baseline (with 95% con dence intervals) will be derived from the tted model.

Secondary E cacy Endpoint Analysis Pharmacokinetics Analysis
Plasma concentrations will be used to build a population PK models to evaluate the effects of NAC on the distribution, metabolism and excretion of MDR-TB drugs.

Mycobacterial characterization
Descriptive summary statistics of M.tuberculosis isolate susceptibility will be presented.

Interim analyses
There will be no interim analysis, apart from approximately 6-monthly safety review by the DSMB (see below). The nal analysis will be performed when the last participant has completed the last trial procedure. There will be database lock, data analysis and trial reports generated from this trial.
Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data We will deploy multiple imputations under the missing at random assumptions for the missing outcomes or covariates, which we anticipate to minimal and not systematic.
Plans to give access to the full protocol, participant level-data and statistical code Data will be available and will be accessed in appropriate data management portals, yet privacy and personal data will not be shared.

Oversight and monitoring
Composition of the coordinating centre and trial steering committee There will be a Clinical Trial Management Group (CTMG) which will undertake all sponsorship responsibilities to ensure that the conduct of the clinical trial comply with Medicines for Human use Regulations of 2004 and subsequent amendments for regulated trials. Five members of the CTMG are composed with the sponsor-investigator, the co-investigator also serves as pharmacotherapy expert, the clinical microbiologist, study doctor also a PhD trainee on clinical trials, and quality assurance largely focusing on safety who has a decade experience of working in clinical trials but also attached for one year at Novartis Pharma under the EDCTP Clinical Research and Development Fellowship. The CTMG will ensure the right, safety, dignity and well-being of the participants are protected and take priority over other interests while the data generated are reliable and robust.
Composition of data safety monitoring board (DSMB), its role and reporting structure A DSMB with three members will be appointed with a primary responsibility of an act in an advisory capacity to the sponsor to safeguard the interests of trial subjects by monitoring subject safety, assess subject risk versus bene t, assess data quality and general evaluation of the trial progress. DSMB activities will be delineated in a term of agreement that will de ne the membership, responsibilities and the scope and frequency of data reviews. The DSMB will operate on a con ict-free basis independently of the sponsor and the trial team. It will comprise at least 3 voting members. The DSMB will have an organisational meeting prior to commencement of the trial. The DSMB will meet approximately every six months and at least annually when it will review unblinded data during a closed session. The sponsor or the DSMB may convene ad hoc meetings if safety concerns arise during the trial. After its assessment, the DSMB will recommend to the sponsor continuation, modi cation or termination of the clinical trial.
Adverse event reporting and harms Adverse events will be collected by the investigator from the time a subject sign the Informed Consent Form through to their end of follow-up visit. Participants that will be early withdrawn, will only have SAEs collected at the time of withdrawal. Any AE (serious or non-serious) observed by the investigator or reported by the subject will be recorded on the Adverse Event Case Report Form. The investigator will review each AE and assess its severity and relationship to drug treatment based on all available information at the time of the completion of the case report form. AE with relationship with drug treatment will be termed as ADRs and severity grading will be according to the CTCAE.
In the case where an overall diagnosis cannot be made, each speci c sign and/or symptom will be recorded as individual AEs. Documentation of the date of onset, and stop date (duration) if applicable will be done. The AEs will also be described in severity, and action taken with IMP while concurrently describing the action taken to the participant. The outcome and relationship to IMP will be recited. Also, the occurrence and seriousness of the AEs will be documented.
Plans for communicating important protocol amendments to relevant parties Any change to the protocol will be completed by means of a protocol amendment. Any changes, which affect subject safety or welfare, will be submitted to the IRB and Regulatory Authorities prior to implementation. Protocol amendments will be incorporated into the public Partnership for Access to Clinical Trial Registry (PACTR202007736854169).

Dissemination plans
Results of this research will be submitted for publication as soon as feasible upon completion of the trial.
An integrative knowledge translation strategy will be used for involving policy makers at the Ministry of Health and Tuberculosis and Leprosy Programme in Tanzania. Findings of this study will be presented to different audiences including the community through community advisory board meetings, media coverage and policy briefs. Findings will also be shared at relevant international conferences.

Discussion
To our knowledge, this is the rst registered trial to examine the protective effect of NAC on occurrence of ADRs in MDR-TB patients treated with current WHO recommended regimens that prioritize bedaquiline, uoroquinolones, linezolid and clofazimine. While this new prioritization removes some renal and hearing loss potential if the injectable aminoglycoside is withheld, there remains considerable risk for hepatoxicity from the combination of bedaquiline, clofazimine and a uoroquinolone, as well as linezolid related cytopenias and neuropathy. Severe ADRs are independently morbid, but resulting treatment interruptions can also amplify M. tuberculosis drug-resistance which is particular concern for loss of e cacy of the novel drugs such as bedaquiline [34]. NAC has been recommended as an adjuvant therapy in certain TB and non-TB settings but currently few programmes have adopted this approach in part due to lack of evidence. NAC trials conducted in DS-TB showed not only a protective effect in DILI but also a delayed onset and hastened resolution of DILI if it did occur [35]. Furthermore, a large cohort study revealed that patients that received pulmonary TB treatment and NAC had a substantial reduction in 90day all-cause mortality compared to those that did not receive NAC [36].
While NAC may provide an opportunity of reducing severe ADRs, it will be important to determine if NAC causes any adverse events independent of the MDR-TB regimen. A pooled analysis of 83 studies (N=9988) that did not include people treated for MDR-TB described the safety of administration of NAC for >6 weeks. Important adverse events included the gastrointestinal intolerance such as nausea, vomiting, abdominal pain which increased 1.4-2.2 times compared to those that did not get NAC [22].
Given this potential, and the fact that NAC has not been trialed in within a patient population on current WHO recommended medication regimens for MDR-TB, there is clinical equipoise for our proposed trial design.
The maximum tolerated dose in phase I study that enrolled participants with a mutation associated degenerative cell disease conducted in US population was found 1800 mg twice daily [37]. Considering less body weight and size of the Tanzanian population, we selected two different doses of NAC, 900 mg and 1800 mg daily for this clinical trial. It is clearly shown that increasing the dose of NAC increases the bioavailability and maximal plasma concentration, yet in overdose scenarios haemolysis, status epilepticus, cerebral oedema and death have occurred, thus warranting vigilance [38][39][40]