Friday, Immutep Limited (NASDAQ:IMMP) released results from Cohort B of the TACTI-003 (KEYNOTE-PNC-34) Phase 2b trial of eftilagimod alfa (efti) in combination with Merck & Co Inc (NYSE:MRK) Keytruda (pembrolizumab) as first-line treatment of recurrent or metastatic head and neck squamous cell carcinoma patients with negative PD-L1 expression.

The updated efficacy and safety data was presented at the ESMO Virtual Plenary session.

The investigational immuno-oncology (IO) combination utilizing efti and Keytruda achieved an objective response rate (ORR) of 35.5% (11 of 31 evaluable patients) and a disease control rate (DCR) of 58.1%.

The company says the results are among the highest recorded for a chemotherapy-free approach in negative PD-L1 patients and compare favorably to a historical control of 5.4% ORR and 32.4% DCR from anti-PD-1 monotherapy.

Additionally, the IO combination attained a high complete response rate of 9.7% (3 of 31 patients). This compares favorably to a historical control of 0% from anti-PD-1 monotherapy in 1L HNSCC patients with a Combined Positive Score (CPS) <1.

One patient with early progressive disease evolved into a confirmed partial responder who remains on therapy after 14 months, resulting in a 38.7% ORR for the IO combination.

Response durability is tracking well, as has been seen in other clinical trials when efti is combined with Keytruda.

Over 50% of patients in Cohort B received treatment for at least six months, with three additional patients nearing this threshold at the data cutoff (11 March 2024). The combination also has a favorable safety profile, with no new safety signals observed.

In April, Immutep reported preliminary topline results from Cohort B of the TACTI-003 Phase 2b trial, demonstrating an ORR of 26.9% and DCR of 57.7% in 26 patients whose tumors do not express PD-L1, which compares favorably to historical controls.

Price Action: At last check on Friday, IMMP shares were up 19.4% at $2.39 during the premarket session.