Late-stage study of Sanofi, Regeneron's Libtayo stopped early after anti-PD-1 therapy significantly improves OS in lung cancer

Data from a Phase III trial showed that Sanofi and Regeneron Pharmaceuticals' anti-PD-1 therapy Libtayo (cemiplimab) significantly prolonged overall survival (OS) in patients with first-line locally advanced or metastatic non-small-cell lung cancer (NSCLC) who tested positive for PD-L1 in at least 50% of tumour cells, the companies reported Monday. The drugmakers said that based on a recommendation by the independent data monitoring committee to stop the trial early, the study will be modified to allow all patients to receive Libtayo.

The trial included 712 patients with squamous or non-squamous, locally advanced NSCLC, who tested positive for PD-L1 in at least half their tumour cells. The companies noted that patients were not candidates for surgical resection or definitive chemoradiation or had progressed after treatment with definitive chemoradiation, or previously untreated metastatic NSCLC. Participants were randomised to receive Libtayo monotherapy administered intravenously every three weeks for up to 108 weeks, or an investigator-selected platinum-based, doublet chemotherapy regimen. The co-primary endpoints are OS and progression free survival (PFS), while secondary measures include overall response rate and duration of response.

According to the companies, the interim analysis showed that patients treated with Libtayo monotherapy saw their risk of death decrease by 32.4% compared to platinum-doublet chemotherapy, "despite a third of [them] entering the trial within the past six months and all chemotherapy patients being able to crossover to Libtayo if their disease progressed." Detailed results will be presented at a future medical meeting, and also used to support marketing applications in the US and Europe this year.

"While demonstrating a survival benefit in first-line NSCLC has been challenging for immunotherapies, the one FDA-approved anti-PD-1 monotherapy [Merck & Co.'s Keytruda (pembrolizumab)] has changed the therapeutic paradigm," commented George Yancopoulos, chief scientific officer at Regeneron. Libtayo is already approved in the US, EU, and other countries for adults with metastatic cutaneous squamous cell carcinoma (CSCC) or locally advanced CSCC who are not candidates for curative surgery or curative radiation.

Meanwhile, a separate Phase III trial evaluating a first-line combination of Libtayo plus chemotherapy in patients with advanced NSCLC irrespective of PD-L1 expression is also under way and expected to be fully enrolled in 2020.

Sanofi and Regeneron are jointly developing Libtayo, formerly known as REGN2810, under a 2015 agreement that was later expanded. The drugmakers eventually restructured the deal, which had been scheduled to end in approximately mid-2020, to allow Sanofi to exit early, although along with Libtayo, the French firm has the right to opt-in to two bispecific programmes.

For additional analysis, see ViewPoints: Libtayo's first lung cancer look is necessary but not sufficient.

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