A novel immunotherapy combination of vidutolimod and nivolumab has demonstrated promising results in patients with stage III cutaneous melanoma. The phase II clinical trial, published in Cancer Cell, showed that presurgical treatment with the TLR9 agonist vidutolimod and the PD-1 inhibitor nivolumab led to tumor control in a significant proportion of patients, potentially improving long-term survival outcomes.
The study, led by Diwakar Davar, MD, Associate Professor at the University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, involved 31 patients with high-risk stage III resectable melanoma. Patients received seven injections of vidutolimod into their tumors and three rounds of intravenous nivolumab prior to surgery, followed by adjuvant treatment with both drugs for one year.
The results indicated a 55% tumor control rate, defined as less than 10% viable tumor cells remaining in the surgical specimen. Patients with the highest response rates exhibited an impressive 88% 2-year recurrence-free survival rate and a 94% metastasis-free survival rate. In contrast, 45% of patients showed either partial (10% to 50% viable tumor cells) or no response (greater than 50% viable tumor cells).
Immune Response and Biomarkers
Comparative analysis of tumors and blood samples revealed that plasmacytoid dendritic cells and myeloid cells were enriched in the highest responders. This finding is notable because these cell types are not typically enriched in patients treated with nivolumab alone, suggesting that vidutolimod may stimulate antitumor immunity through a distinct pathway.
Mass spectrometry analysis further supported this hypothesis, demonstrating that most patients treated with the combination therapy had elevated levels of key immune-related proteins, indicating TLR9 activation. According to Dr. Davar, identifying a protein signature associated with TLR9 administration was a key finding, providing a pharmacodynamic parameter for TLR9 agonists.
Gut Microbiome Analysis
Interestingly, the study also explored the role of the gut microbiome in modulating treatment responses. Patients whose tumors shrank the most had higher levels of Gram-negative bacteria, a finding that contrasts with typical observations in anti-PD-1 therapy, where specific bacterial compositions are associated with better outcomes. Hassane Zarour, MD, Professor at the University of Pittsburgh School of Medicine and UPMC Hillman Cancer Center, noted that these findings highlight the complexity and context-dependency of the gut microbiome's effects in cancer immunotherapy.
Clinical Implications
The observed 55% response rate is on par with currently approved immunotherapy combinations for melanoma, according to Dr. Davar. This study marks the first clinical trial to evaluate the combination of nivolumab and vidutolimod in the neoadjuvant setting, offering a potential new treatment strategy for patients with resectable stage III melanoma. Further research is warranted to confirm these findings and to elucidate the precise mechanisms by which vidutolimod enhances antitumor immunity and interacts with the gut microbiome.
