The POSEIDON trial was a Phase III trial of AstraZeneca’s Imfinzi (durvalumab) plus platinum-based chemotherapy or Imfinzi, tremelimumab and chemotherapy versus chemotherapy alone in the 1st-line treatment of patients with Stage IV (metastatic) non-small cell lung cancer (NSCLC).

Positive high-level results from the final analysis of POSEIDON showed the combination of Imfinzi, tremelimumab and chemotherapy demonstrated a statistically significant and clinically meaningful overall survival (OS) benefit versus chemotherapy alone. This immunotherapy combination also demonstrated a statistically significant improvement in progression-free survival (PFS) versus chemotherapy alone, as previously reported in October 2019. Patients in this arm were treated with a short course of tremelimumab, an anti-CTLA4 antibody, over a 16-week period in addition to Imfinzi and standard chemotherapy.

The Imfinzi plus chemotherapy arm demonstrated a statistically significant improvement in PFS versus chemotherapy in the previous analysis, but the OS trend observed in this analysis did not achieve statistical significance. Patients in the control arm were treated with up to six cycles of chemotherapy, while those in the experimental arms were treated with up to four cycles.

Each combination demonstrated an acceptable safety profile, and no new safety signals were identified. The combination with tremelimumab delivered a broadly similar safety profile to the Imfinzi and chemotherapy combination and did not lead to an increased discontinuation of treatment.

Dave Fredrickson, Executive Vice President, Oncology Business Unit, said: “We are pleased to see the POSEIDON Phase III trial demonstrate, for the first time, a significant and clinically meaningful overall survival benefit for Imfinzi plus tremelimumab with chemotherapy in metastatic non-small cell lung cancer. We were particularly pleased by the safety profile. We’ve seen encouraging uptake of novel combinations in this setting and believe this new approach will add a further option for patients with high unmet medical need. We look forward to discussing next steps with regulatory authorities.”

The data will be presented at a forthcoming medical meeting.

Imfinzi is the only approved immunotherapy in the curative-intent setting of unresectable, Stage III NSCLC after chemoradiation therapy and is the global standard of care based on the PACIFIC Phase III trial. Imfinzi is also approved in the US, the EU, Japan and many countries around the world for the treatment of extensive-stage small cell lung cancer (ES-SCLC) based on the CASPIAN Phase III trial.

Imfinzi is being further assessed across all stages of lung cancer as part of an extensive Immuno-Oncology programme across NSCLC and SCLC, as well as in other tumour types.

The combination of Imfinzi and tremelimumab is being tested in lung cancer, bladder cancer and liver cancer settings.