OM-85, a Bacterial Lysate, Reduces Pulmonary Nodule Malignant Probability: A Retrospective Study

Introduction: The current clinical management of pulmonary nodules relies heavily on CT follow-up, without early intervention. This retrospective study investigated the efficacy of OM-85, a standardized lysate of human respiratory bacteria, in the treatment of high-risk pulmonary nodules detected by computed tomography (CT) in patients with chronic bronchitis. Methods: This study included 72 patients (93 enrolled nodules) who underwent treatment with OM-85 and a matched control group of 90 patients (111 control nodules). The primary endpoint included reduced size of high-risk ground glass nodules based on thin-layer CT scans during follow-up. Flow cytometry, multiplex immunofluorescence (mIF) analysis, and scRNA-seq data were employed to determine differences in the immune cell subsets between the treatment and control groups. Results: Oral OM-85 treatment significantly reduced lung nodule diameter (p = 0.031), the risk probability of malignancy (p = 0.003), and the likelihood of clinical disease progression (p = 0.0091). The effects of OM-85 treatment were more pronounced in older patients (> 65-year-old) (p = 0.029) and those with longer follow-up cycles (> 200 days) (p = 0.011). The peripheral blood samples showed a significantly higher proportion of natural killer (NK) cells in the treatment group. Furthermore, mIF staining of the pulmonary nodules and scRNA-seq data demonstrated a higher percentage of NK cells in the treatment group compared with the control group (p = 0.0003). Conclusion: OM-85 reduced the size of high-risk pulmonary nodules and decreased the risk of malignant probability and disease progression in patients with chronic bronchitis by increasing the proportion of NK cells. Therefore, OM-85 is a potential drug for the treatment of high-risk pulmonary nodules in patients with chronic bronchitis.