UPDATE 3-Regeneron's blood cancer therapy faces setback as FDA raises trial concerns

(Updates shares, adds analyst comments in last two paragraphs,)

March 25 (Reuters) - Regeneron Pharmaceuticals said on Monday the U.S. FDA has declined approval for its blood cancer therapy for two forms of lymphoma on concerns over the progress of ongoing confirmatory trials.

The FDA said in its response letter that it needs more data from enrollments in dose-finding and confirmatory portions of trials, delaying its decision on the drug, while confirming no issues with clinical efficacy or safety, trial design, labeling or manufacturing.

The company was testing its experimental drug, odronextamab, in multiple late-stage trials in patients with follicular lymphoma and diffuse large B-cell lymphoma, the two most common subtypes of non-Hodgkin lymphoma.

Regeneron said "it was the first time" a CRL for this reason was issued by the U.S. Food and Drug Administration, which has been lately working to raise the bar for cancer drug developers seeking accelerated approval for their candidates.

Such approvals allow the agency to move therapies that target serious and life-threatening conditions to the market more quickly, but have been criticized because some drugs have later been proven to be ineffective.

Regeneron's shares fell marginally to $961.78 in early trading. The company was looking to expand its oncology portfolio with odronextamab, beyond its lone approved skin cancer drug, Libtayo

While odronextamab was on track to potentially become Regeneron's first blood cancer drug, it has a much smaller market opportunity of $200 million compared to other potential launches of the company as lymphoma is a competitive space, RBC Capital Markets analyst Brian Abrahams said.

Abrahams added that he does not believe this delay significantly impacts the company's fundamentals as odronextamab would have been a "marginal revenue driver".

(Reporting by Sneha S K, Puyaan Singh and Sriparna Roy in Bengaluru; Editing by Shinjini Ganguli)