Infant TB Infection Prevention Study (iTIPS): A randomised trial protocol evaluating isoniazid to prevent M. tuberculosis infection in HIV-exposed uninfected children

Introduction: HIV-exposed uninfected (HEU) infants in tuberculosis (TB) endemic settings are at high risk of Mycobacterium tuberculosis (Mtb) infection and TB disease, even in the absence of known Mtb exposure. Because infancy is a time of rapid progression from primary infection to active TB disease, it is important to define when and how TB preventive interventions exert their effect in order to develop effective prevention strategies in this high-risk population. Methods and analysis: We designed a non-blinded randomised controlled trial to determine efficacy of isoniazid (INH) to prevent primary Mtb infection among HEU children. Target sample size is 300 (150 infants in each arm). Children are enrolled at 6 weeks of age from maternal and child health clinics in Kenya and are randomised to receive 12 months of daily INH ∼10 mg/kg plus pyridoxine or no INH. The primary endpoint is Mtb infection, assessed by interferon-gamma release assay QuantiFERON-TB Gold Plus (QFT-Plus) or tuberculin skin test after 12 months post-enrolment. Secondary outcomes include severe adverse events, expanded Mtb infection definition using additional QFT-Plus supernatant markers and determining correlates of Mtb infection. Exploratory analyses include a combined outcome of TB infection, disease and mortality, and sensitivity analyses excluding infants with baseline TB-specific responses on flow cytometry. Ethics and dissemination: An external and independent Data and Safety Monitoring Board monitors adverse events. Results will be disseminated through peer-reviewed journals, presentations at local and international conferences to national and global policy-makers, the local community and participants. The infant TB Infection Prevention Study (‘iTIPS’) is a two-arm, non-blinded RCT comparing efficacy of a 12-month course of daily INH versus no INH to prevent Mtb infection among HEU Kenyan children enrolled at 6 weeks of age (figure 2). Eligible infants are randomised using a 1:1 allocation to INH versus no INH (figure 3). Overall study strategy. HEU, HIV-exposed uninfected; IGRA, interferon-gamma release assay; INH, isoniazid; MCH, maternal child health; Mtb, Mycobacterium tuberculosis; PMTCT, prevention of maternal to child transmission; TST, tuberculin skin test. CONSORT diagram. IGRA, interferon-gamma release assay; INH, isoniazid; Mtb, Mycobacterium tuberculosis; TST, tuberculin skin test. Kenya is one of 22 high TB burden countries with a generalised TB epidemic,35 with an estimated TB prevalence of 426 per 100 000.36 This study is conducted in collaborative research sites in western Kenya embedded in Ministry of Health (MOH) maternal child health (MCH) clinics. HIV-infected mothers are followed as part of the national prevention of maternal to child transmission (PMTCT) programme and currently receive Option B+ triple antiretroviral therapy (ART).37 Per Kenyan guidelines, all PLHIV should be screened at routine HIV care visits using symptom-based TB screening and those with negative screens are evaluated for IPT.11 35 37 We recruit mothers living with HIV and their HIV-exposed infants from MCH/PMTCT sites. Infants 6 weeks (+4 weeks) of age are eligible for inclusion if they are born to HIV-infected mothers, with birth weight >2.5 kg, and not born premature (>37 weeks’ gestation). Infants with known household TB exposure, including mothers with TB diagnosed in the past year, are ineligible. Infants enrolled in other TB prevention or TB vaccine studies are ineligible because these interventions might affect ascertainment of endpoints. Site-stratified randomisation is used to allocate infants 1:1 to INH or no INH arms. Randomisation numbers were generated prior to study start using STATA V.14 “ralloc” command with resulting randomisation assignment by participant ID printed on cards and placed in opaque envelopes. The study is non-blinded to enable prompt clinical management for any potential drug-related adverse event. IGRAs are performed in the Kenya Medical Research Institute (KEMRI) Centers for Disease Control (CDC) laboratory, which is blinded to arm. The study team administers TST and is not blinded to TST result. Data monitoring by the study team is not disaggregated by study arm. The study biostatistician reviews data by arm during preparation of reports to the external Data and Safety Monitoring Board (DSMB). These data are reviewed during closed DSMB sessions, which excludes team members involved in study implementation. After informed consent is obtained by study staff, household locator information, medical identification number and cellphone contacts are obtained to facilitate tracing. On enrolment, standardised questionnaires regarding sociodemographic, clinical, obstetric and HIV-related factors, TB exposure and history, and TB symptoms (for infant, mother and household members (by maternal report) using WHO symptom screen38) are administered (online supplementary table 1). Mothers with suspected TB are referred to the TB programme for further screening. If mothers are found to have TB on enrolment, their infants are ineligible for participation and are referred to receive INH per Kenya national guidelines. bmjopen-2019-034308supp001.pdf Infants undergo physical examination measuring weight, height/length, mid-upper arm circumference and presence of BCG scar. Medical records are used to abstract data on infant birth weight, PMTCT prophylaxis, other medications, immunisations, and maternal ART regimen, viral load and CD4 cell counts. INH ~10 mg/kg (7–15 mg/kg) is administered once daily to infants in the INH arm for 12 months. Standardised weight-based dosing (by weight band using 100 mg scored tablets) is used, corresponding to Kenya and WHO recommendations.30 39 Pyridoxine is provided to children randomised to INH to decrease peripheral neuropathy risk.30 39 Caregivers are advised on how to pulverise INH and pyridoxine to be mixed with small quantities of breast milk, clean water or liquid co-trimoxazole to ensure full doses are given and for ease of administration to infants. Participants in the intervention arm are administered daily INH and pyridoxine by caregivers. Infants in the control arm do not receive INH or pyridoxine. Follow-up visits occur at 10 weeks for infants enrolled at 6 weeks of age and at 14 weeks, and 6, 9 and 12 months of age for all participants coinciding with routine Kenya paediatric visit schedule. Follow-up visits include assessment of any TB diagnosis in the mother, infant or household member since the past visit, as well as any TB symptom in the mother, infant and household members (by maternal report). Infants in the no INH arm found to have a known TB contact during the study are referred for IPT per Kenyan guidelines. Infants and mothers found to have TB symptoms are referred to the MOH TB Programme for further evaluation. Questionnaires regarding caregiver barriers and facilitators to providing prophylactic medications (co-trimoxazole, antiretrovirals for PMTCT and INH (if in INH arm)) are administered at the 6 month of age visit. Endpoint ascertainment occurs at a study visit 12 months post-randomisation at approximately 14 months of age. Infant blood for peripheral blood mononuclear cells (PBMCs) and plasma are collected at baseline and visit 2 (10–14 weeks of age). At 12 months post-randomisation, blood is collected for IGRA (QFT-Plus) and TST placed and read within 48–96 hours.40 41 Infant rectal swabs are collected at enrolment for future gut microbiome studies. Maternal breast milk and blood for PBMC and plasma separation are collected on enrolment. Liver function tests (LFTs) are performed at enrolment and 1 month following INH initiation. Adherence is assessed by caregiver report at follow-up visits. Urine is collected at follow-up and study endpoint visits and tested using strips developed to detect INH metabolites.42 43 Hair is collected at study endpoint for future assessment of INH levels as a more objective adherence measure over time.44 45 IPT has been shown to be safe in prior RCTs and is administered routinely to TB-exposed infants.2 12–14 Although routine LFT monitoring is not recommended during INH in children,20 for this trial baseline LFTs are drawn at enrolment and 1 month after INH initiation. National Institutes of Health (NIH) Division of AIDS (DAIDS) Table for Grading the Severity of Paediatric Adverse Events is used to grade toxicities.46 Infants with LFTs ≤grade 2 are allowed to initiate INH. Infants with baseline LFTs >grade 3 at baseline have LFTs monitored every 2 weeks and do not initiate INH until LFTs are ≤grade 2. Children are evaluated for peripheral neuropathy using a truncated Denver Developmental test.47 After INH initiation, if toxicity is suspected, study-administered drugs are immediately discontinued and in case of concern for hepatoxicity, LFTs are repeated. An external and independent DSMB, including experts in paediatric TB, biostatistics and trial design, monitors severe adverse events (SAEs). Summaries of SAEs are given to DSMB members during scheduled meetings. Each SAE is assigned plausibility of relatedness to study drug by study investigators. ‘Open’ reports detailing cumulative overall SAEs are descriptive (no statistical analyses). ‘Closed’ reports of SAEs by study arm are reviewed and the DSMB makes recommendations regarding any imbalances in safety outcomes. O’Brien-Fleming boundaries for benefit and harm are used for interim monitoring, and these boundaries are provided by the study statistician in closed reports. The DSMB assesses operational aspects, safety and effectiveness, and makes recommendations regarding study continuation or modifications. Futility is not considered a basis for stopping rules because of the trial’s value in understanding correlates of Mtb infection in HEU infants. Participants may withdraw from the study at any point. Study investigators may withdraw a participant on a case-by-case basis if the intervention or study involvement poses a risk to the participant. No modification of allocation will be made. Infants who receive at least one dose of study drug will be included in per-protocol analyses. Caregivers of infants who discontinue INH are encouraged to continue study follow-up and endpoint ascertainment. Study staff use tablets to collect de-identified data using secure password-protected Research Electronic Data Capture mobile software (REDCap; Vanderbilt University, Nashville, Tennessee, USA).48 Data are uploaded daily from tablets to the web-based REDCap database. Study investigators will have access to the finalised dataset. Patients were not directly involved in the development of the research question, design of the study or recruitment. We assess the burden of the trial intervention for participants by gathering data on adverse events, tolerability of INH, and assessment of caregiver barriers and facilitators to providing prophylactic medications to HEU children via questionnaire. Overall study results will be shared with the clinical facilities and presented to local stakeholders including MOH county and national representatives. The primary outcome is Mtb infection by QFT-Plus assay or TST 12 months after enrolment. Similar to QuantiFERON-TB Gold (QFT) IGRA, QFT-Plus measures IFN-γ released by primarily CD4+ T helper lymphocytes after TB-specific antigen (ESAT-6 and CFP-10) stimulation. In addition, QFT-Plus measures IFN-γ released by CD8+ cytotoxic T lymphocytes, after stimulation with the same antigens, which may have increased sensitivity in children, and in populations with lower CD4 counts including PLHIV.49 50 Responses of ≥0.35 IU/mL to TB antigens above the Nil response in either the primarily CD4+ (TB1) or CD8+ response (TB2) (with Nil <8 IU/mL and a positive mitogen control) are considered positive per manufacturer recommendations.49 A TST of >10 mm is considered positive.20 Secondary outcomes include severe adverse events (grade >3 per DAIDS Grading Severity of Paediatric Adverse Experiences),46 use of IFN-γ-independent immune markers in QFT-Plus supernatants to indicate Mtb infection,51–55 and epidemiological and immunological correlates of Mtb infection. Exploratory outcomes include combined endpoint of Mtb infection, TB diagnosis and/or death, as well as sensitivity analyses of the primary outcome of Mtb infection after excluding infants with evidence of immune responses to ESAT-6 or CFP-10 at enrolment in flow cytometric analyses. Assuming an alpha of 0.05, power of 0.80, using a two-sided test and a 1:1 allocation ratio, with 125 infants in each arm, we have power to detect at least a 65% decrease in Mtb infection in INH arm versus control if cumulative incidence of Mtb infection in the control arm at 12 months is 0.20, or to detect 70%–80% or higher (HR 0.3–0.2) decrease if cumulative incidence of Mtb infection in the control arm is 0.15 or 0.10 (online supplementary table 2). To account for loss to follow-up, non-adherence and INH resistance, we increased sample size by 20%, with goal enrolment of 300 infants (150 per arm). Baseline characteristics will be compared between randomisation arms to assess randomisation adequacy. bmjopen-2019-034308supp002.pdf Modified intention-to-treat: We will use a modified intention-to-treat approach, including all participants who underwent randomisation irrespective of receiving trial medication with at least one measure of Mtb infection (QFT-Plus or TST), excluding children found to be HIV DNA positive during the study. We will compare the proportion of infants with Mtb infection (either QFT or TST positive) at 12 months between INH and no INH arms using a χ2 test and estimate relative risk with 95% CIs using a generalised linear model with log link and Poisson family. We will compare cumulative incidence of Mtb infection by arm using a Cox proportional hazard regressions model. Per protocol: We will evaluate our primary outcome by a per-protocol analysis, considering only HEU infants who took at least one dose as taking INH versus infants who did not take any INH. We anticipate future sensitivity analyses using IPT adherence and continuation data as exposure of interest and Mtb infection as outcome. Safety and expanded Mtb infection outcomes: For secondary outcomes, we will compare proportions of participants by arm using either χ2 or Fisher’s exact tests as appropriate for >grade 3 serious adverse events. In addition, we will conduct secondary analyses using an expanded Mtb infection definition including a positive TST, QFT-Plus or IFN-γ-independent immune markers in QFT-Plus supernatants. Epidemiological and immune correlates of Mtb infection will be assessed using nested case–control studies incorporating all Mtb infections from both arms then conducting stratified analyses in each trial arm to evaluate potential cofactors modified by INH. We will compare a composite endpoint of Mtb infection, TB diagnosis and/or death between randomisation groups using a χ2 test. Baseline assays may detect evidence of Mtb infection. We will conduct additional exploratory analyses, incorporating data from baseline assays56 (using flow cytometry of cryopreserved PBMCs) to exclude infants with evidence of Mtb-specific immune responses to ESAT-6 or CFP-10 at enrolment also using a χ2 test.