A drug from Amgen could give patients with a notoriously aggressive form of lung cancer significantly more time to live when added to an immunotherapy from AstraZeneca, a study found.

Full results from a late-stage trial released Saturday show that adding Amgen's immunotherapy Imdelltra to AstraZeneca's Imfinzi drug slashed the risk of death by 58% in patients with extensive-stage small cell lung cancer, a fast-growing disease that has spread beyond the lung where it began.

The drug combination extended their median overall survival to 21.1 months compared with 12.7 months with AstraZeneca's drug alone, the trial found.

That means half of patients in the group that took the combination regimen were alive for at least roughly 21 months. The trial tested the combo as a maintenance therapy in patients who received initial treatment with Imfinzi and chemotherapy, and whose cancer had not progressed.

"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, in an interview.

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," he said, adding that "these data say that's a possibility." The results also suggest a greater commercial opportunity for Imdelltra, which posted $288 million in sales during the second quarter, up 115% year over year. The drug already generated $627 million in global sales in 2025 and appears to be on its way to becoming a blockbuster medicine, or hitting the $1 billion sales threshold.

Small cell lung cancer remains difficult to treat because, even if chemotherapy initially works well for most patients, the disease often returns or progresses within months, said lead trial investigator Dr. Jacob Sands, who is the associate chief of the Lowe Center for Thoracic Oncology at Dana-Farber Cancer Institute.

He said immunotherapy has helped a small subset of patients achieve years of disease control, but most have not experienced similarly durable benefits, highlighting the need for better treatments. There are roughly 31,000 new small cell lung cancer cases in the U.S. each year, and an estimated 60% to 70% of those people are diagnosed with extensive-stage disease.

Sands said the benefits in the trial were seen across subgroups of patients, including those whose cancer spread to the brain or liver. Disease that has spread to those organs is associated with poorer treatment outcomes.

He added that with longer-term follow-up data on the patients, the 21-month figure "may evolve further and hopefully will substantially improve," similar to what Amgen saw in a Phase 1 trial on the immunotherapy combination. In that early-stage trial on a smaller number of patients, a long-term follow-up showed the benefit was sustained for years.

Amgen said the findings also suggest that using Imdelltra earlier in a patient's treatment could meaningfully alter the trajectory of the disease. Imdelltra is currently approved for patients whose small cell lung cancer has progressed while they are on, or after, platinum-based chemotherapy.

Researchers specifically tested whether adding Imdelltra could help patients live longer than continuing Imfinzi alone, which is already approved as a first treatment for this type of lung cancer. Amgen said nearly 80% of patients who started taking both drugs were alive at one year compared with 53% receiving Imfinzi alone.

Imdelltra's "big impact" on controlling the disease and ultimately how long people live highlights the importance of including it in first-line maintenance treatment, Sands said. That refers to ongoing therapy given after an initial heavy treatment, such as chemotherapy or surgery.

Burton added that it positions Amgen's drug to be an "indispensable backbone therapy" for small cell lung cancer, regardless of the other immunotherapy that can be paired with it.

Imdelltra binds to DLL3, a protein on cancer cells, and CD3, a protein on T cells, which are a type of immune cell that can kill cancer. By binding to both, Imdelltra brings T cells into close contact with tumor cells, helping the immune system destroy the cancer.

Imfinzi, made by AstraZeneca, is an immunotherapy that blocks a protein called PD-L1, which cancer cells use to evade the immune system. The drugs work together in complementary ways: Imfinzi helps remove the brakes on the immune response, while Imdelltra brings T cells directly to cancer cells and helps activate them to attack the tumor.

The study, which was presented at a major cancer meeting called the European Society for Medical Oncology Congress, did not test whether the combination was better than other first-line treatment approaches.

Still, the findings suggest Amgen's drug could be another option offered to small cell lung cancer patients earlier in their treatment. Kate Brenan, a 44-year-old mother of two from Denver, sees that as a win on its own.

She was diagnosed with extensive-stage small cell lung cancer in early January 2024. Brenan underwent six rounds of a common combination chemotherapy, followed by chest radiation and later whole-brain radiation after the cancer spread.

In September 2024, she started Imdelltra and has had no evidence of disease ever since.

"I think that it's remarkable how quickly things are changing in the world of small cancer treatment options," Brenan told CNBC, adding that Imdelltra potentially becoming an earlier treatment option "can only be a good thing for the patients moving forward, and I'm really excited about that."