Soft tissue sarcoma (STS) encompasses a diverse group of rare, high-grade malignancies originating from mesenchymal tissues, exhibiting significant heterogeneity in histology, molecular characteristics, and clinical behavior. The prognosis for advanced or metastatic STS remains generally poor, underscoring the urgent need for more effective therapeutic strategies. Currently, the standard first-line treatment for advanced STS involves chemotherapy regimens comprising anthracyclines, primarily doxorubicin, often combined with ifosfamide (the AI regimen). While these regimens can induce tumor responses, their overall efficacy is limited, with modest response rates and survival benefits. Moreover, certain STS subtypes demonstrate resistance to conventional chemotherapy, highlighting the necessity for novel and combination treatment approaches.
Recent advances in immunotherapy, particularly immune checkpoint inhibitors (ICIs) targeting PD-1/PD-L1 pathways, have opened new avenues for treating specific STS subtypes. Evidence suggests that anthracyclines, such as doxorubicin, can induce immunogenic cell death, enhance tumor antigen presentation, and upregulate PD-L1 expression, creating a compelling rationale for combining chemotherapy with immunotherapy. Indeed, clinical studies have demonstrated that combining ICIs like pembrolizumab with chemotherapy regimens can improve objective response rates (ORR), progression-free survival (PFS), and overall survival (OS) compared to chemotherapy alone in certain patient populations.
Envolizumab represents a groundbreaking development in the realm of immunotherapeutics. As the world's first subcutaneously injectable PD-L1 single-domain antibody-Fc fusion protein, it boasts several distinct advantages: a small molecular weight (\~80 kDa) that ensures superior tissue penetration, high stability with room temperature storage capability, and a convenient subcutaneous administration route that enhances patient tolerability and adherence. Phase II clinical data have demonstrated promising anti-tumor activity in MSI-H/dMMR solid tumors, with an ORR of 42.7%, and an acceptable safety profile, with grade 3-4 treatment-emergent adverse events (TEAEs) in only 15.5% of patients. Notably, in 2022, the FDA granted orphan drug designation to Envolizumab for the treatment of STS, highlighting its potential as a novel therapeutic option.
This study aims to systematically evaluate the efficacy and safety of combining Envolizumab with the AI chemotherapy regimen as a first-line treatment for patients with advanced STS. The primary endpoint will focus on the overall response rate (ORR), with secondary endpoints including disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety profile assessments. The study hypothesizes that this combination could synergistically enhance anti-tumor immune responses, improve clinical outcomes, and offer a more tolerable treatment option for patients with advanced STS. The findings could potentially establish a new standard of care and provide critical insights into the integration of immunotherapy and chemotherapy in the management of this challenging malignancy.
