Immutep (ASX:IMM) announced promising new data from the Phase IIb TACTI-003 trial presented at ESMO Immuno-Oncology Congress 2024. The trial combines the company’s lead drug candidate, efthyragimod alfa (efti), with Merck & Co.’s drug Keytruda (pembrolizumab). The target indication is head and neck squamous cell carcinoma (HNSCC).

Cancer cells hiding from T cells

T cells are the “soldiers” of the immune system, and there are different types of T cells. For example, “cytotoxic” T cells recognize and destroy abnormal cells, such as cancer cells.

PD-1 is a protein receptor on the surface of T cells, and PD-L1 is a protein on cancer cells (and some normal cells).

When PD-L1 binds to PD-1, it effectively turns T cells “off” and prevents them from attacking abnormal cells. This is a defense mechanism used by cancer cells.

PD-1 inhibitors (Keytruda is one example) work by blocking PD-1 and preventing it from interacting with PD-L1. This keeps T cells active.

The amount of PD-L1 protein within the tumor is measured by the PD-L1 composite positivity score (CPS). A high CPS suggests that a patient will respond well to treatments like Keytruda. However, if a tumor has very low PD-L1 (for example, CPS <1), this suggests that the tumor is not relying on the PD-1/PD-L1 pathway to evade the immune system. Masu. Other mechanisms may be used instead. In this scenario, blocking PD-1 receptors has little effect. Immutep’s efti drug is not a PD-1 inhibitor per se, but stimulates a broader immune response and promotes T-cell activation and proliferation. This makes PD-1 inhibitors such as Keytruda even more effective. result

Immutep results demonstrate a clear improvement compared to historical outcomes for HNSCC patients with a CPS score less than 1, which represents approximately 20% of all HNSCC patients.

  • Overall survival of 12 months. This is the percentage of a group of patients who are alive after 12 months. Typically, when treated with PD-1 inhibitors alone, the 12-month overall survival rate is 39%. In contrast, Immutep reports a 12-month overall survival rate of 67% when using efti with Keytruda.
  • Progression-free survival. This is the period of time from the start of treatment until the cancer progresses, worsens, or the patient dies. It is reported as the “median” (the time at which 50% of the patient group experienced worsening of symptoms). With anti-PD1 therapy alone, this number would be 2.1 months. 5.8 months with efti.
  • Response period. This is the period of time from when treatment begins to work until the cancer worsens. For anti-PD1 alone, the median time is 2.6 months. For efti, it’s been 9.3 months so far.
  • Objective response rate. This is the percentage of patients whose tumor shrinks significantly (partial response) or disappears completely (complete response). For anti-PD1 alone, the rate is 5.4%. efti is 35.5%.
  • complete response. This means that the cancer can no longer be detected by scans or other laboratory tests. Anti-PD1 alone does not produce a complete response. However, Immutep reports complete responses of 12.9% or 16.1% (depending on which criteria are used to measure tumor response to treatment).

Immutep CEO Marc Voigt said the data highlights the potential for efti to address important unmet needs. “Treatment options for patients with PD-L1 expression <1 are very limited and usually include chemotherapy. This data suggests that new approaches may be possible for up to 20% of these patients. “It highlights the possibilities,” he said. Immutep shares are trading 2.82% higher at 36.5 cents.