Antitumor mechanisms of OncoTherad (MRB-CFI-1) nanoimmunotherapy involving monoamine oxidases: Clinical implications in BCG-unresponsive non-muscle invasive bladder cancer.

e14597 Background: Bacillus Calmette-Guérin (BCG) immunotherapy has been the gold standard treatment for non-muscle invasive bladder cancer (NMIBC) for nearly half a century. However, many high-risk patients experience recurrence, including those who progress and eventually become unresponsive to BCG. The emergence of new immunotherapeutic agents has revolutionized the treatment of various tumor types, including urothelial carcinoma. In this context, our research group has developed OncoTherad (MRB-CFI-1) immunotherapy, which has shown promising results in cancer treatment, particularly in NMIBC. Given the inherent complexity of the immune response, patient selection and the development of biomarkers to guide the identification of individuals who will derive the greatest benefit from a specific immunotherapy remain crucial. Over the past years, several studies have demonstrated the upregulation of monoamine oxidases (MAOs) in tumor progression and metastasis. Therefore, the objectives of this present study were to characterize the effects of OncoTherad (MRB-CFI-1) on the modulation of MAOs (MAO-A and MAO-B) in the bladder of patients with BCG-unresponsive NMIBC. Methods: A total of 40 bladder biopsies from patients with BCG-unresponsive NMIBC treated with OncoTherad (MRB-CFI-1) were collected and analyzed from Paulínia Municipal Hospital (HMP). These samples were then divided into two groups (n=20 per group): Group 1 (biopsy before OncoTherad treatment) and Group 2 (biopsy after OncoTherad treatment). Subsequently, the samples underwent immunohistochemical analyses for MAO-A and MAO-B. The retrospective anonymous study was approved by the local ethics committee (Clinical Trial: RBR-6swqd2). Results: Our results demonstrated high immunoreactivities for both MAO-A and MAO-B in the bladder tumor microenvironment prior to OncoTherad (MRB-CFI-1) treatment, confirming that the pattern reported in literature studies can also be observed in NMIBC. Total immunoreactivities for MAO-A did not differ statistically between bladder biopsies of Groups 1 and 2, indicating that this treatment does not interfere with the action of MAO-A in bladder tissue. In contrast, immunoreactivities for MAO-B were significantly lower (p<0.05) in the Group 2 when compared to Group 1 suggesting that this immunotherapy reversed the immunosuppressive state and tumor progression induced by MAO-B. Conclusions: Taken together, our results support the use of MAO-B as a biomarker for clinical response to OncoTherad (MRB-CFI-1) immunotherapy.