AstraZeneca (LON: AZN) announced that Imfinzi (durvalumab) together with tremelimumab and platinum-based chemotherapy improved overall survival by 23% and progression-free survival by 28% compared to chemotherapy alone in patients with Stage IV (metastatic) non-small cell lung cancer (NSCLC). The data came from a Phase 3 trial known as POSEIDON.

Imfinzi and tremelimumab are immune checkpoint inhibitors.

“The POSEIDON data offer patients further benefit from Imfinzi and are an important validation of our development strategy to explore novel combinations,” said Susan Galbraith, AstraZeneca’s executive vice president, oncology R&D.

Imfinzi is a human monoclonal antibody that targets programmed death-ligand 1 (PD-L1).

While many Big Pharma firms have developed PD-L1 drugs, few have become blockbusters — Bristol Myers Squibb’s Yervoy (ipilimumab) is one exception.

The POSEIDON trial had 338 recipients who received Imfinzi, tremelimumab and chemotherapy. Another 337 received chemotherapy alone.

A 2020 study published in Medicine found that durvalumab and tremelimumab combination therapy was well tolerated and demonstrated clinical benefit in treating head and neck squamous cell carcinoma. That study concluded that more evidence was needed to confirm the benefit of using the two drugs together.

FDA first approved Imfinzi for advanced bladder cancer on May 1, 2017. It is now approved for unresectable Stage III non-small cell lung cancer and extensive-stage small cell lung cancer. Earlier this year, the company voluntarily withdrew the indication for advanced bladder cancer.

The safety profile of the combination of durvalumab, tremelimumab and chemotherapy was similar to that of chemotherapy alone.