Preclinical Evaluation of LVR01 Attenuated Salmonella as Neoadjuvant Intralesional Therapy in Combination with Chemotherapy for Melanoma Treatment

Treatment of malignant melanoma has improved in the last few years owing to early detection and new therapeutic options. Still, management of advanced disease remains a challenge because it requires systemic treatment. In such cases, dacarbazine-based chemotherapy has been widely used, despite low efficacy. Neo -adjuvant therapies emerge as alternative options that could help chemotherapy to achieve increased benefit. In this work, we evaluate LVR01, an attenuated Salmonella enterica serovar typhimurium, as neoadjuvant intra-lesional therapy in combination with dacarbazine in a preclinical melanoma model. B16F1 melanoma-bearing mice received intraperitoneal administration of dacarbazine for 3 consecutive days. LVR01 treatment, consisting of one single intratumoral injection, was applied 1 day before chemotherapy began. This therapeutic approach retarded tumor growth and prolonged overall survival, revealing a strong synergistic antitumor effect. Dacar-bazine induced a drastic reduction of secondary lymphoid organ cellularity, which was partially restored by Salmonella, particularly potentiating activated cytotoxic cell compartments. Systemic immune reactivation could be a consequence of the intense inflammatory tumor microenvironment induced by LVR01. We propose that the use of LVR01 as neoadjuvant intralesional therapy could be considered as an interesting strategy with close clinical application to boost chemotherapy effect in patients with melanoma. 2