AstraZeneca and Incyte Corporation are pushing forward on the development of immunotherapy combination treatments.

This morning, the two companies announced the expansion of their clinical partnership to include a study pairing epacadostat, Incyte’s investigational selective IDO1 enzyme inhibitor with AstraZeneca’s anti-PD-LI drug, Imfinzi. The combination therapy will be compared to Imfinzi alone. The companies will initiate a Phase III trial testing the drug combination against Imfinzi alone in patients with locally-advanced (Stage III), unresectable non-small cell lung cancer. The trial is expected to begin in the first half of 2018.

Steven Stein, Incyte’s chief medical officer, said the company was excited about the combination trial as it seeks to “position IDO1 enzyme inhibition as a key component of combination immunotherapy.”

The Phase III trial, which will be co-funded by the two companies and will be conducted by AstraZeneca, is expected to begin enrolling patients in the first-half of 2018. This agreement builds on an existing clinical collaboration for epacadostat and Imfinzi, which was first announced in May 2014.

Stage III lung cancer represents approximately one-third of NSCLC incidence and was estimated to affect around 105,000 patients in seven leading markets in 2016. More than half of these patients have tumors that are unresectable, according to Incyte’s announcement.

In July, the U.S. Food and Drug Administration Administration awarded Imfinzi (duravulumab) the Breakthrough Therapy Designation for treatment of for patients with locally-advanced, unresectable non-small cell lung cancer (NSCLC) whose disease has not progressed following platinum-based chemoradiation therapy. This is the same set of patients AstraZeneca and Incyte will target with the combination treatment.  The FDA granted the designation following the announcement of interim results from its Phase III Pacific Trial in May. Interim results from the trial showed that Imfinzi had already met its primary endpoint, which was statistically significant and clinically meaningful progression-free survival (PFS). It also showed a favorable benefit/risk profile.

AstraZeneca’s CMO Sean Bohan said Imfinzi has demonstrated “exciting clinical potential” in treating lung cancer patients. He said the Incyte agreement builds on the results of the Pacific trial. By combining Imfinzi with an IDO1 enzyme inhibitor, Bohan said the combination “could provide additional benefit to patients with locally-advanced lung cancer.”

Incyte’s IDO1 (indoleamine 2,3-dioxygenase 1) programs have generated a lot of excitement in the pharma industry. In April, Incyte and Bristol-Myers Squibb forged a deal to evaluate the combination of epacadostat and Opdivo as a first-line therapy for non-small cell lung cancer across the spectrum of PD-L1 expression and first-line treatment for head and neck cancer.

Epacadostat is an investigational oral selective IDO1 enzyme inhibitor. The drug is designed to modulate anti-tumor immune responses through the promotion of regulatory T cell generation.