GlaxoSmithKline (GSK) has announced that it will stop enrolling patients into trials evaluating its investigational inducible T cell co-stimulatory (ICOS) agonist feladilimab.

The British drugmaker has taken the decision to halt enrolment into the Phase II INDUCE-3 trial, following a recommendation from the Independent Data Monitoring Committee, the company said in a statement.

The INDUCE-3 study was designed to evaluate feladilimab as part of a combination treatment alongside Merck & Co’s Keytruda (pembrolizumab), versus placebo plus Keytruda.

The benefit of the ICOS agonist plus Keytruda was being evaluated as a treatment for patients with PD-L1 positive recurrent locally advanced or metastatic head and neck squamous cell carcinoma in this trial.

At the same time, GSK also announced its intent to halt another study – the Phase II INDUCE-4 trial – which is investigating feladilimab versus placebo in combination with Keytruda and chemotherapy.

The INDUCE-4 was also evaluating the ICOS agonist in patients with recurrent or metastatic head and neck squamous cell carcinoma.

Feladilimab – also known as GSK3359609 – is designed to selectively enhance T cell function, with GSK previously saying the drug has shown promising anti-tumour activity in combination with Keytruda in PD-1/L1 naive patients with head and neck squamous cell carcinoma.

In the previous INDUCE-1 study, head and neck squamous cell carcinoma patients who had received up to five prior lines of therapy in the advanced setting received either a combination of feladilimab plus Keytruda or feladilimab monotherapy.

In the combination arm, the overall response rate was 24% – these responses were durable, according to GSK, with all patients maintaining benefit for at least six months or longer.

Although GSK did not disclose its reasons for stopping the trials, the company said that the totality of the data will be evaluated to ‘assess the impact on the overall clinical development programme for feladilimab’.