Immunotherapy Breakthrough Offers Hope for Rare Soft Tissue Sarcomas

NEW YORK, NY – November 13, 2025

A Novel Approach to a Rare Cancer

Positive Phase II trial data released this week is generating excitement in the oncology community, offering a potential new avenue for treating soft tissue sarcoma (STS), a rare and aggressive cancer. Australian biotechnology company, Immutep Limited, announced encouraging results from its EFTISARC-NEO trial at the recent CTOS Annual Meeting, demonstrating the potential of its lead immunotherapy candidate, eftilagimod alfa (efti), in combination with radiotherapy and pembrolizumab. This represents a significant step forward in addressing a disease with limited treatment options and historically poor outcomes.

STS accounts for approximately 1% of all adult cancers, with over 70 distinct subtypes, making diagnosis and treatment particularly challenging. The standard of care typically involves surgical resection, often followed by radiotherapy, and, in some cases, chemotherapy. However, for patients with advanced or metastatic disease, treatment options are often limited, highlighting a critical unmet need for innovative therapies.

Promising Phase II Data

The EFTISARC-NEO trial, conducted at the Maria Skłodowska-Curie National Research Institute of Oncology in Poland, evaluated the combination of efti, radiotherapy, and pembrolizumab in patients with resectable STS. The results showcased a remarkable 51.5% tumor hyalinization/fibrosis rate, exceeding expectations and suggesting a robust biological effect. Importantly, increases in key immune response biomarkers – CXCL9, CXCL10, IL-23, and IFN-γ – correlated with positive pathological responses, offering valuable insights into the mechanism of action.

“The correlation of biomarker changes with clinical response is particularly exciting,” stated an oncologist familiar with the trial data. “It suggests we're seeing a true activation of the immune system within the tumor microenvironment, which is crucial for durable responses.” The ability to identify predictive biomarkers could also enable clinicians to better select patients who are most likely to benefit from this combination therapy.

The trial included patients with a diverse range of STS subtypes, including rare and aggressive forms, broadening the potential applicability of the treatment. The combination therapy is designed to stimulate the immune system’s ability to recognize and destroy cancer cells, going beyond the limitations of traditional therapies. The observed tumor hyalinization/fibrosis suggests a unique mechanism of action – the replacement of viable tumor cells with fibrous tissue – potentially leading to long-term disease control.

Immutep's LAG-3 Strategy Gains Momentum

Immutep’s approach centers on activating the Lymphocyte-Activation Gene-3 (LAG-3) pathway, a critical immune checkpoint that regulates T cell function. Unlike other immunotherapies that focus on blocking PD-1 or CTLA-4, efti is a soluble LAG-3-related protein that binds to and activates the LAG-3 receptor on immune cells, enhancing their ability to target and kill cancer cells. This unique mechanism of action differentiates efti from existing immunotherapies and opens up new possibilities for combination strategies.

The company has been strategically building its clinical pipeline around LAG-3 activation, with trials underway in several different cancer types, including non-small cell lung cancer, head and neck cancer, and breast cancer. Positive data from the EFTISARC-NEO trial reinforces the potential of this strategy and positions Immutep as a key player in the rapidly evolving field of immuno-oncology.

“We believe that LAG-3 activation holds significant promise for unlocking the full potential of the immune system in cancer,” stated a source close to Immutep’s research and development efforts. “By stimulating rather than simply blocking immune checkpoints, we aim to achieve more durable and effective responses.”

Beyond Metastasis: A Paradigm Shift in Treatment?

The current standard of care for STS largely focuses on treating advanced or metastatic disease. However, the EFTISARC-NEO trial represents a significant departure from this approach, demonstrating the potential of immunotherapy in earlier-stage disease. By intervening before the cancer has had a chance to spread, clinicians may be able to achieve more durable remissions and improve long-term survival rates.

The concept of adjuvant immunotherapy – administering immunotherapy after surgery to eliminate any remaining cancer cells – is gaining traction in other cancer types, and the results of the EFTISARC-NEO trial suggest that this approach may also be beneficial in STS. The ability to enhance the immune system’s ability to clear residual disease could significantly improve outcomes and reduce the risk of recurrence.

The company plans to continue evaluating the data from the EFTISARC-NEO trial and explore potential avenues for further development, including larger clinical trials and biomarker studies. The ultimate goal is to establish efti as a standard-of-care treatment for patients with resectable STS and improve the lives of those affected by this challenging cancer. The market for STS treatment is projected to reach $2.8 billion by 2035, indicating significant opportunities for innovative therapies like efti.