Adding Amgen’s immunotherapy Imdelltra to AstraZeneca’s Imfinzi sharply improved survival among patients with extensive stage small cell lung cancer, according to full results from a late stage trial. The aggressive disease grows quickly and has spread beyond the lung where it began.

The combination reduced the risk of death by 58% compared with Imfinzi alone. Median overall survival reached 21.1 months for patients receiving both medicines, compared with 12.7 months among those continuing only AstraZeneca’s treatment.

That median means half of the patients who received the combination remained alive for at least roughly 21 months. Researchers tested the regimen as maintenance therapy after patients received initial treatment with Imfinzi and chemotherapy without their cancer progressing.

“I think there are moments in medicine when you see a piece of data that is so profound that it’s going to transform the standard of care for patients, and I think, honestly, we’re at that moment,” said Dr. Paul Burton, Amgen’s chief medical officer.

Burton said the combination “has the potential to take on one of the most aggressive cancers that we deal with today, and almost convert it into a chronic disease,” adding that “these data say that’s a possibility.”

The findings could also expand the commercial opportunity for Imdelltra. The medicine recorded $288 million in second quarter sales, up 115% from the previous year, and has already generated $627 million in global sales during 2025.

Small cell lung cancer remains particularly difficult to treat because the disease often returns or progresses within months, even when chemotherapy initially works well for most patients. Roughly 31,000 new cases arise in the United States annually, with an estimated 60% to 70% diagnosed at the extensive stage.

Lead trial investigator Dr. Jacob Sands said immunotherapy has helped a small group of patients achieve years of disease control. Most patients, however, have not experienced similarly durable benefits, reinforcing the need for more effective treatment options.

Sands, the associate chief of the Lowe Center for Thoracic Oncology at Dana-Farber Cancer Institute, said the trial’s benefits appeared across patient subgroups. That included people whose cancer had spread to the brain or liver, which is associated with poorer treatment outcomes.

Longer follow up could further change the 21 month survival figure, Sands said. A Phase 1 trial involving fewer patients found that the combination’s benefit remained for years when researchers later examined longer term results.

Amgen said the new findings indicate that giving Imdelltra earlier could meaningfully alter the disease’s trajectory. The medicine is currently approved for patients whose small cell lung cancer has progressed during or after treatment with platinum based chemotherapy.

Researchers examined whether adding Imdelltra could extend survival beyond continuing Imfinzi alone, which is already approved as an initial treatment for this cancer. Nearly 80% of patients who began taking both medicines were alive after one year, compared with 53% receiving only Imfinzi.

Imdelltra binds to DLL3, a protein found on cancer cells, and CD3, a protein on T cells. Connecting with both proteins brings the immune cells close to tumor cells, helping the immune system destroy the cancer.

Imfinzi blocks PD-L1, a protein cancer cells use to evade the immune system. The medicines therefore act in complementary ways, with Imfinzi removing restraints on the immune response while Imdelltra brings T cells directly to cancer cells and helps activate an attack.

The study was presented at the European Society for Medical Oncology Congress, although it did not compare the combination with other initial treatment approaches. Still, the results suggest Imdelltra could become an earlier option for patients with small cell lung cancer.

Kate Brenan, a mother of two from Denver who was 44, was diagnosed with extensive stage small cell lung cancer in January 2024. After chemotherapy and radiation, she began Imdelltra in September 2024 and has had no evidence of disease since then.