Eli Lilly & Co’s lung cancer hopeful, sintilimab, got hit with a complete response letter from the U.S. FDA. The agency says it needs more information before it can approve the drug in its current form and recommended another clinical study.

Lilly, along with China-based partner Innovent Biologics, is developing sintilimab as an injectable treatment, combined with pemetrexed and platinum chemotherapy, as a treatment for patients with nonsquamous non-small-cell lung cancer (NSCLC) — one of the two major types of lung cancer.

The FDA wants to know more before they can approve sintilimab. The agency has recommended the additional trial of sintilimab to compare the standard of care therapy for first-line metastatic NSCLC to sintilimab with other forms of chemotherapy.

Sintilimab is already approved and marketed in China under the name Tyvyt as a treatment for some types of cancer, including relapsed or refractory classic Hodgkin’s lymphoma. It has also been approved as a treatment for NSCLC in China and approved to be used alongside chemotherapies for other types of cancers.

Back in January, Innovent and Laekna Therapeutics announced a partnership to study the combination of Innovent’s sintilimab with Laekna’s pan-AKT inhibitor afuresertib. The two companies were hoping to use the combination to develop a therapy for patients with solid tumors that have not been responsive to treatment.

Following the FDA’s letter, Innovent and Lilly say they will assess the next steps before moving forward.