Merck (MSD) has reported that its Keytruda met the primary goal of overall survival (OS) in Phase III KEYNOTE-355 trial involving patients with metastatic triple-negative breast cancer (mTNBC).

A humanised monoclonal antibody, Keytruda hinders the interaction between PD-1 and its ligands, PD-L1 and PD-L2, to trigger T lymphocytes that could impact tumour cells and healthy cells.

The anti-programmed death receptor-1 (PD-1) treatment boosts the immune system’s ability to find and fight tumour cells.

The randomised, two-part, placebo-controlled Phase III trial compared Keytruda against a placebo when given with one of the three chemotherapy regimens.

Subjects enrolled in the trial had locally recurrent inoperable or metastatic TNBC and did not receive chemotherapy earlier in the advanced setting.

Part two of the trial involved 847 subjects, who were randomised in a 2:1 ratio to be given Keytruda 200mg every three weeks plus chemotherapy or placebo in combination with chemotherapy.

In the trial, the investigator selected chemotherapy regimens that were either nab-paclitaxel, paclitaxel or gemcitabine/carboplatin.

Data from the trial showed that first-line therapy with Keytruda plus chemotherapy offered a statistically significant and clinically meaningful improvement in OS versus the placebo combination in mTNBC patients with PD-L1-expressing tumours.

Furthermore, no new safety signals linked to the treatment were observed in the trial.

Merck Research Laboratories clinical research vice-president Dr Vicki Goodman said: “In the fight against triple-negative breast cancer, the subtype with the worst survival prognosis, new options that can extend the lives of patients are urgently needed.

“These new overall survival results confirm that Keytruda in combination with chemotherapy represents an important treatment option for certain patients with metastatic TNBC.”

The new OS data comes after an interim analysis that was conducted previously. According to the results, Keytruda plus chemotherapy substantially enhanced progression-free survival in mTNBC patients.

Merck, earlier this month, reported that the Phase III KEYNOTE-522 trial of Keytruda plus chemotherapy showed a statistically significant event-free survival in high-risk early-stage TNBC patients.