How Immutep’s Efti Combo Achieved 51.5% Tumor Response in Soft Tissue Sarcoma
Immutep Limited’s Phase II trial of eftilagimod alfa combined with radiotherapy and KEYTRUDA in soft tissue sarcoma patients has exceeded its primary endpoint, showing a 51.5% median tumor hyalinization rate, more than triple the historical standard. These promising results, presented at ESMO 2025, suggest a potential breakthrough in a challenging cancer indication.
- Phase II EFTISARC-NEO trial met primary endpoint with 51.5% tumor hyalinization
- Tumor response over three times higher than standard radiotherapy alone
- Efti combined with KEYTRUDA and radiotherapy showed strong safety profile
- Results consistent across multiple soft tissue sarcoma subtypes
- Data presented as a Proffered Paper at ESMO Congress 2025
A Significant Step Forward in Soft Tissue Sarcoma Treatment
Immutep Limited has announced compelling results from its investigator-initiated Phase II EFTISARC-NEO trial evaluating eftilagimod alfa (efti) in combination with radiotherapy and KEYTRUDA for patients with resectable soft tissue sarcoma (STS). Presented at the 2025 European Society of Medical Oncology (ESMO) Congress, the study surpassed its primary endpoint, achieving a median tumor hyalinization/fibrosis rate of 51.5%, significantly above the pre-specified target of 35% and historical benchmarks of 15% with radiotherapy alone.
This measure of tumor hyalinization serves as an early surrogate marker linked to improved overall and recurrence-free survival, suggesting that the novel combination therapy could meaningfully enhance patient outcomes in a disease known for its poor prognosis and limited treatment options.
Broad Efficacy and Safety Across Sarcoma Subtypes
The trial’s results were consistent across multiple STS subtypes, underscoring the potential versatility of efti’s mechanism of action. Eftilagimod alfa activates antigen-presenting cells, stimulating both innate and adaptive immune responses to overcome the immunosuppressive tumor microenvironment. This immune activation appears to synergize effectively with radiotherapy and the anti-PD-1 immunotherapy KEYTRUDA, amplifying anti-cancer effects.
Importantly, the safety profile was favorable, with only one patient experiencing a grade 3 or higher immunotherapy-related adverse event, supporting the combination’s tolerability in this patient population.
Implications for Future Development and Patient Care
STS remains an orphan disease with significant unmet medical needs, with thousands of new cases and deaths annually in the United States alone. The promising data from EFTISARC-NEO, primarily funded by the Polish Medical Research Agency, could pave the way for larger pivotal trials and eventual regulatory submissions.
Immutep’s CEO Marc Voigt emphasized the importance of these findings in addressing the substantial gap in effective therapies for STS patients. Meanwhile, the company continues to advance efti in other solid tumors, including ongoing Phase III studies in lung and head and neck cancers, leveraging its unique immunomodulatory properties.
While these Phase II results are encouraging, longer-term survival data and broader clinical validation will be critical to confirm the therapy’s full potential and impact on standard-of-care treatment paradigms.
Bottom Line?
Immutep’s breakthrough Phase II results mark a hopeful advance for soft tissue sarcoma, but the journey to clinical adoption and market impact is just beginning.
Questions in the middle?
- Will larger Phase III trials confirm the survival benefits suggested by tumor hyalinization?
- How will Immutep position efti in the competitive immunotherapy landscape for STS?
- What regulatory pathways and timelines can investors expect following these results?
