Preclinical Study on Novel Treatment Regimen for Elderly Patients with Drug-Sensitive Pulmonary Tuberculosis

Treatment for elderly patients with pulmonary tuberculosis (PTB) is challenging due to poor efficacy and tolerance. The aim of this study is to preliminarily screen candidate regimens for elderly patients with drug-sensitive PTB. Candidate regimens were initially screened using the artificial-intelligence-enabled phenotypic response surface (AI-PRS) platform and in vitro experiments. The hepatorenal cytotoxicity of drug combinations was assessed with HEK293T and THLE-2 cells. In the in vivo validation stage, aged mice with airway Mycobacterium tuberculosis (Mtb) infection received the novel regimens by oral gavage for 4 weeks, while isoniazid (H)/rifampicin (R)/ethambutol (E)/pyrazinamide (Z) served as the standard regimen control. Hepatorenal function was monitored during the treatment to assess drug safety, and pathological HE staining was also performed to evaluate liver and kidney damage. Bacterial loads in the lungs and spleens were evaluated using colony-forming unit (CFU) assays. After three rounds of AI-PRS analysis and MIC screening in vitro, three optimized treatment regimens were identified including delamanid (Dlm)/bedaquiline (Bdq)/pretomanid (Pa) combined with rifapentine (Rpt), pasiniazid (PAS-H) and levofloxacin (Lfx). After validation with an experiment on aged mice, the Bdq-containing regimen resulted in the mildest pulmonary inflammation and the lowest bacterial loads in lungs and spleens. The bacterial burden was similar between Bdq- and Dlm-containing regimens, which presented stronger bactericidal activity over the HREZ regimen. Regarding drug safety evaluation, the Bdq-containing regimen showed no marked hepatotoxicity and nephrotoxicity in our preclinical models, while other regimens showed variable abnormalities in serum biochemical indices. The Bdq/Lfx/PAS-H/Rpt regimen presented high efficacy and more favorable safety in aged mice compared with the standard regimen, considered as a promising preclinical candidate for elderly patients with drug-sensitive TB and deserving of further clinical trials for evaluation.