Trial Outcomes & Findings for Efficacy and Safety Evaluation of Two to Four Months of Treatment With the Combination Regimens of DBOS and PBOS in Adults With Pulmonary Tuberculosis (NCT NCT05971602)

This multicenter, two-stage, open-label, randomized trial evaluated the efficacy, safety, and pharmacokinetics (PK) of two novel regimens: DBOS: Delamanid (D), Bedaquiline (B), OPC-167832 (O), and Sutezolid (S) and PBOS: Pretomanid (P), Bedaquiline, OPC-167832, and Sutezolid in adult participants with drug sensitive tuberculosis (DS-TB) against the standard 2HRZE/4HR regimen (Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), Ethambutol (E), referred to as HRZE hereafter).

Total of 93 participants were enrolled and started on study treatment (DBOS, n=30; PBOS, n=32; HRZE, n=31). One randomized participant from PBOS arm withdrew from the trial before starting study treatment. The study was terminated early based on preliminary results showing inadequate efficacy to support either investigational regimen's ability to meet the core trial objective of identifying a ≤3-month regimen after review with the Independent Data Monitoring Committee. Stage 2 was not conducted.

Efficacy and Safety Evaluation of Two to Four Months of Treatment With the Combination Regimens of DBOS and PBOS in Adults With Pulmonary Tuberculosis

An Adverse Event is any untoward medical occurrence in a patient or clinical trial participant, temporally associated with the use of trial intervention, whether or not it is considered related to trial intervention. TEAEs are new or worsening AEs that occur on or after first dose of treatment and no later than two weeks after last dose of treatment. Intensity for each TEAE was graded using Division of Allergy and Infectious Diseases (DAIDS) grading as Grade 1 (Mild), Grade 2 (Moderate), Grade 3 (Severe), Grade 4 (Potentially Life-threatening), or Grade 5 (Death), as determined by Investigator. A serious adverse event (SAE) is defined as any untoward medical occurrence that, at any dose that resulted in death, was immediately life-threatening, required inpatient hospitalization or prolongation of an existing hospitalization, significant disability or incapacity, had a congenital anomaly or birth defect, or was determined to be a medically significant or important event or reaction.

Participants that experienced one or more of the following events after randomization were categorized as having an unfavorable outcome status: absence of microbiological cure (positive sputum culture, excluding documented TB re-infection with a different Mtb strain than baseline, at Week 17 \[DBOS and PBOS arms\] or Week 17-26 \[HRZE arm\]); death from any cause; permanent discontinuation of trial treatment before the end of the assigned treatment duration; extension of TB treatment by the Investigator more than 5 days beyond the end of the assigned treatment duration for any reason such as re-start of TB treatment by the Investigator during the post-treatment follow-up period excluding documented TB re-infection with a different Mycobacteria tuberculosis (Mtb) strain than baseline; positive culture for Mtb at last visit excluding documented TB re-infection with a different Mtb strain than baseline.

Trial treatment of participants was discontinued due to various reasons such as, pregnancy, AE, SAE, death, laboratory abnormality, intercurrent medical condition or illness, new requirement for a concomitant medication on the excluded medication list, or other situation where an Investigator determined that continued administration of trial treatment is not in the best interest of the participant and study terminated by sponsor and treatment failure.

An AE is any untoward medical occurrence in a patient or clinical trial participant, temporally associated with the use of trial intervention, whether or not it is considered related to the trial intervention. Intensity for each AE was graded using Division of Allergy and Infectious Diseases (DAIDS) grading as Grade 1 (Mild), Grade 2 (Moderate), Grade 3 (Severe), Grade 4 (Potentially Life-threatening), or Grade 5 (Death), as determined by the Investigator. A SAE is defined as any untoward medical occurrence that, at any dose that resulted in death, was immediately life-threatening, required inpatient hospitalization or prolongation of an existing hospitalization, significant disability or incapacity, had a congenital anomaly or birth defect and was medically significant or important event or reaction.

Participants that experienced one or more of the following events following randomization were categorized as having an unfavorable outcome status: absence of microbiological cure (positive sputum culture from Week 17 or later, excluding documented TB re-infection with a different Mtb strain than baseline); death from any cause; permanent discontinuation of trial treatment before the end of the assigned treatment duration; extension of TB treatment by the Investigator more than 5 days beyond the end of the assigned treatment duration for any reason such as re-start of TB treatment by the Investigator during the post-treatment follow-up period excluding documented TB re-infection with a different Mtb strain than baseline; positive culture for Mtb at last visit excluding documented TB re-infection with a different Mtb strain than baseline.

Sputum culture conversion (SCC) was assessed using MGIT liquid culture and was defined as two successive Mtb culture negative results collected at least 5 days apart up to and including the assessment timepoint (Week 28) without any intervening or subsequent Mtb culture positive results through Week 28, ignoring contaminated and unevaluable cultures. A higher percentage reflects more participants achieving and maintaining sputum culture conversion to negative for Mtb.

Time to sustained SCC (SSCC) is defined as the time from first dose to the first of two successive Mtb culture negative results, collected at least 5 days apart, without any intervening or subsequent Mtb culture positive result for the duration of a participant's follow-up. For positive Mtb culture results at or after Week 17, the strain must have been indistinguishable from baseline based on whole genome sequencing results to lose SSCC status. Participants in the who never achieved SSCC were censored at the date of sputum collection that yielded their last negative or positive culture result

TTD is measured as the length of time in days from the beginning of culture incubation to the detection of pure Mtb growth. At each study visit, up to two MGIT sputum cultures were performed. The shorter TTD value from the (up to) two cultures resulted as pure Mtb-positive without contamination, was used for analysis at that timepoint. If culture was negative for Mtb, TTD was set to 43 days. Culture results of "Positive for MTB Complex with contamination", "Positive for MTB and NTM", "Contaminated", or "No result", were excluded from the analysis. Mean change from Baseline in sputum MGIT culture TTD was calculated as change in the TTD at week T minus baseline TTD. Higher TTD indicates slower bacterial growth.

Löwenstein Jensen (LJ) medium was used as an additional solid culture medium for isolation of Mtb. SCC in LJ was defined as two negative solid sputum cultures obtained at least 5 days apart up to and including the assessment timepoint (Week X) without any intervening or subsequent Mtb culture positive result through Week X ignoring contaminated and unevaluable cultures. A higher percentage reflects more participants achieving and maintaining sputum culture conversion to negative for Mtb.

Time to sustained SCC (SSCC) using LJ medium is defined as the time from first dose to the first of two successive Mtb culture negative results, collected at least 5 days apart, without any intervening or subsequent Mtb culture positive result for the duration of a participant's follow-up. For positive Mtb culture results at or after Week 17, the strain must have been indistinguishable from baseline based on whole genome sequencing results to lose SSCC status. Participants who never achieved SSCC were censored at the date of sputum collection that yielded their last negative or positive culture result.

Phenotypic drug susceptibility testing (DST) was performed on Mtb-positive cultures in the MGIT system to assess if any resistance had developed during and after treatment. DST was performed on the baseline visit or Week 1 sputum culture depending on suitability of culture growth for DST performance, and again on the first culture positive for Mtb at Week 13 or afterwards in all arms. WHO-recommended critical concentrations were used to test for susceptibility to Bedaquiline (1.0 microgram \[ug\]/mL), Delamanid (0.6 ug/mL), Isoniazid (0.1 ug/mL), Rifampicin (1.0 ug/mL), Pyrazinamide (100 ug/mL), and Ethambutol (5 ug/mL).

MIC testing determined the lowest drug concentration for Mtb susceptibility in the DBOS and PBOS groups, following the same schedule as DST. Bedaquiline, Delamanid, and Pretomanid were tested via the MGIT system, while OPC-167832 and Sutezolid used EUCAST-recommended broth microdilution. Baseline is defined as last assessment made prior to first administered dose of trial medication. In measured values table below, baseline and post-baseline median MIC values are presented for each drug.