A phase Ib trial investigating the combination of neoadjuvant oncolytic virus OrienX010 (ori) and toripalimab (tori) has shown promising results in patients with resectable stage III and IVM1a acral melanoma (AM). The study, published in Nature, demonstrated a 77.8% pathological response rate and a 33.3% major pathological response, offering a potential new treatment avenue for this challenging melanoma subtype.
Superior Recurrence-Free Survival
The trial's recurrence-free survival (RFS) rates at one and two years post-operation were 85.2% and 81.5%, respectively. The median RFS was not reached, while the mean RFS reached 40.3 months. These figures significantly surpass previously reported RFS rates for adjuvant therapy alone in AM, which range from 14.8 to 26 months. "These preliminary data are encouraging and require further confirmation in a controlled trial," the researchers noted.
Addressing Unmet Needs in Acral Melanoma Treatment
Acral melanoma, a rare subtype of melanoma that occurs on the palms, soles, or nail beds, is often less responsive to immunotherapy compared to cutaneous melanoma. Data from clinical trials of anti-PD-1 monotherapy in Asia have shown an overall response rate of only 18.0% and a median progression-free survival (PFS) of 3–5 months. This lower efficacy is attributed to a more immunosuppressive tumor microenvironment in AM, characterized by depletion of cytotoxic CD8+ T cells, enrichment of Treg cells, and exhausted CD8+ T cells.
Oncolytic Virus Enhances Immunotherapy Response
The study leverages the ability of oncolytic viruses to modify the tumor microenvironment, making it more susceptible to immune checkpoint inhibitors (ICIs). The combination therapy of ori and tori significantly increased the secretion of cytokines critical for tumor elimination, including TNF, TNFR, IFN-γ, Fas ligand, GZMA, GZMH, GZMB, CXCL9, CXCL10, CXCL11, CXCL13, CCL19, CCL23, IL-12, IL-18, and IL-10. This extensive cytokine elevation suggests that virotherapy enhances immune cell activity, thereby improving sensitivity to immunotherapy.
Implications for Adjuvant Therapy
The trial also raises questions about the necessity of adjuvant therapy following neoadjuvant treatment in patients who achieve a major pathological response. Given that most grade 3 adverse events (AEs) were associated with the adjuvant period and patient outcomes were satisfactory after neoadjuvant treatment, the researchers suggest that subsequent adjuvant therapy may not be necessary for AM patients with a major pathological response. This approach could potentially reduce the risk of AEs without compromising efficacy.
Safety Profile and Future Directions
The majority of treatment-emergent adverse events (TEAEs) were grade 1/2, with only 13.3% of patients experiencing grade 3 AEs. This safety profile compares favorably to previous studies combining anti-PD-1 inhibitors and oncolytic viruses. The study authors emphasize the need for a phase 3 randomized controlled trial to confirm these findings, given the single-arm design of the current study. They also suggest future studies should explore subsequent treatment and surgery strategies based on different pathologic response patterns.
Limitations
The authors acknowledge limitations including the small sample size and single-center design, as well as the need for longer follow-up to fully assess the clinical impact and durability of responses. Despite these limitations, the preliminary data support the promise of this new combination immunotherapy regimen in acral melanoma.
