Regeneron and partner Sanofi on Monday disclosed new results showing their immunotherapy Libtayo helped patients newly diagnosed with advanced non-small cell lung cancer live longer than those given chemotherapy in a Phase 3 trial.Libtayo reduced the risk of death by 32% versus chemo in patients whose tumors expressed high levels of PD-L1, a protein known to predict response to immunotherapy, and by 43% in those with PD-L1 expression confirmed by a specific test. Libtayo patients in the former group lived a median of 22 months, versus 14 months for chemo-treated patients. Median overall survival wasn’t reached for patients confirmed to have high PD-L1, according to data unveiled at the European Society of Medical Oncology’s virtual meeting.

The results likely support approval of Regeneron’s drug in lung cancer, one of oncology’s largest markets. But the data don’t yet separate Libtayo from Merck’s dominant immunotherapy Keytruda, which has become the standard of care for many with the disease and one of the world’s top-selling medicines.

Regeneron, best known for the eye drug Eylea, is a latecomer to the hyper-competitive field of cancer immunotherapy. But its efforts appear to be gaining traction.

The Tarrytown, New York-based biotech first announced a move into the field via a major immuno-oncology alliance with Sanofi in 2015, after Keytruda and Bristol Myers Squibb’s Opdivo and Yervoy were already approved. When Libtayo won its first approval in 2018 for a type of skin cancer, several other similar immunotherapies had already joined Merck’s and Bristol Myers’ as well.

By then, immunotherapy developers were aggressively pursuing a mix-and-match strategy to test their treatments with others, hoping to broaden the proportion of patients who benefit from treatment. That’s resulted in a surge of clinical studies: the non-profit Cancer Research Institute last week reported some 6,200 immunotherapy trials are currently underway globally, up 14% from last year.

Regeneron’s approach has been to get its foot in the door in areas others haven’t pursued, like cutaneous squamous cell carcinoma and cervical cancer, and then prove Libtayo competitive in more crowded fields like lung cancer.

The data disclosed at ESMO are a potentially important step in that process. They set the stage for Libtayo to be competitive in lung cancer, a field in which multiple immunotherapy regimens already exist but room for improvement remains. Immunotherapies are expected to generate $20 billion in sales in 2020 in non-small cell lung cancer alone and should continue to grow for the next five years, wrote SVB Leerink analyst Geoffrey Porges.

Regeneron could soon be in the mix, having filed for approval last week. The study supporting that submission, disclosed on Monday, pitted Libtayo against chemotherapy in 710 patients with squamous or non-squamous advanced non-small cell lung cancer and whose tumor cells expressed high levels of PD-L1. Regeneron measured the results in those patients, as well as a subset of 563 people whose PD-L1 levels were confirmed using a specific test.

Regeneron said 39% of patients responded to Libtayo in its Phase 3 trial and were 32% less likely to die. In the subgroup with confirmed high PD-L1 expression, the relative risk reduction was even higher, at 43%.

In a similar trial called Keynote-024, 45% of patients responded to treatment with Merck’s Keytruda, which reduced the risk of death by 40% versus chemotherapy.

Though it’s difficult to compare drugs across trials, Wall Street analysts found the results as matching Keytruda’s. That could make it difficult for Regeneron to compete with Merck’s drug, which is firmly entrenched as the leading immunotherapy in lung cancer.

“Clearly the long-game here for [Regeneron] in oncology remains combinations, and it has many in its arsenal,” wrote Cantor Fitzgerald analyst Alethia Young. The biotech has some bi-specific antibodies it’s developing, for instance, and is teaming with others to test Libtayo alongside treatments such as oncolytic viruses and cell therapies.

A more immediate threat to Merck in lung cancer could come via an ongoing Phase 3 trial testing combinations of Libtayo and either chemotherapy or Yervoy against Keytruda head-to-head. Results could come next year, according to the clinicaltrials.gov database.