Aug 1 (Reuters) - Regeneron REGN.O said on Friday the U.S. Food and Drug Administration has once again declined to approve its blood cancer therapy, this time in relation to observations from the regulator's inspection at a third-party manufacturing site.

The company was seeking approval for its drug odronextamab to treat follicular lymphoma — a type of cancer that begins in the lymph system, a part of the immune system — in patients whose cancer has returned and who have received at least two prior lines of treatment.

The regulator had first declined to approve the therapy in March last year, seeking more data from enrollments in dose-finding and confirmatory portions of trials testing it.

Regeneron said on Friday the latest FDA decision was due to its inspection at contract manufacturer Catalent's Indiana site, which was acquired by Danish drugmaker Novo Nordisk NOVOb.CO.

Catalent's Bloomington, Indiana facility is a fill-finish site for Regeneron's Eylea HD and odronextamab, and handles the final stages of drug preparation and packaging.

The observations at the inspection have also resulted in delays to three applications for the high-dose version of its eye disease drug Eylea, Regeneron said, adding that Novo has been in communication with the FDA and expects to submit its response next week.

There is clear frustration and exhaustion with the repeated regulatory setbacks, said Cantor analyst Carter Gould.

Regeneron said the inspection was completed in mid-July and it anticipates an expeditious resolution of the issues.

Odronextamab belongs to a class of treatments called bispecific antibodies, which are designed to attach to a cancer cell and an immune cell bringing them together so that the body's immune system can kill the cancer.

The drug was approved by the European Commission in August 2024 to treat follicular lymphoma, and is branded as Ordspono in the region.

(Reporting by Puyaan Singh, Mariam Sunny and Siddhi Mahatole in Bengaluru; Editing by Shilpi Majumdar)

((Puyaan.Singh@thomsonreuters.com))