Amgen's Imdelltra used in combination with AstraZeneca's immunotherapy Imfinzi reduced the risk of death by 58 percent compared to the Astra drug alone in patients with extensive-stage small cell lung cancer, according to data from a study presented at a major medical meeting on Saturday.
Imfinzi is currently the standard of care following chemotherapy for patients with this very aggressive and hard-to-treat disease whose cancer does not worsen after initial chemotherapy.
The study found that those given both drugs lived for a median of 21.1 months, compared with 12.7 months for those treated only with Imfinzi.
"If you give Imdelltra earlier and earlier, you get bigger clinical benefit," said Paul Burton, chief medical officer at California-based Amgen. He called the results "unprecedented in advancing the treatment of extensive-stage small cell lung cancer".
Imdelltra's US list price is about $30,000 per cycle, or over $390,000 a year. Wall Street analysts have estimated annual sales reaching more than $2.5 billion by 2030, according to LSEG data.
The Amgen drug is currently approved for adults in the advanced stages of small cell lung cancer that has worsened despite chemotherapy, based on data showing that Imdelltra reduced the risk of death by 40 percent.
Full results of the 563-patient trial were presented at the European Society for Medical Oncology meeting in Madrid and published in the New England Journal of Medicine. Amgen had previously announced that the Phase 3 study was successful.
Imdelltra belongs to a dual-target class of drugs called bispecific antibodies designed to pull immune system T cells into contact with cancer cells to destroy them. Imfinzi is an older type of immunotherapy that essentially blocks the mechanism tumours use to hide from immune-system assault.
Most lung cancer cases are non-small cell, while up to 15 percent are the small cell variety targeted by Imdelltra. About 250,000 new cases are diagnosed worldwide each year, according to the US National Institutes of Health.
Very few people diagnosed with small cell lung cancer are candidates for surgery, and most are initially given radiotherapy and chemotherapy, Burton said.
Survival rates depend on when the cancer is diagnosed, but the overall five-year rate is only around 9 percent, according to the American Cancer Society.
Amgen said that nearly 80 percent of trial patients treated with the combination were alive after one year, compared with 53 percent of those on Imfinzi alone, as patient follow-up continues.
Serious side effects, including low white blood cell counts, occurred in 20.9 percent of patients on the dual therapy and 10.8 percent with the single therapy. A potentially dangerous condition known as cytokine release syndrome, an aggressive inflammatory response, was reported in 49.6 percent of patients who received Imdelltra. But only one case was serious and there were no CRS-related deaths.
Adverse events led to discontinuation of the combination therapy in 5.7 percent of trial patients and 5.8 percent of patients given only Imfinzi.