Regeneron Pharmaceuticals Inc. (REGN) and Sanofi SA (SNY) may have to delay the launch of two potential blockbuster drugs due to deficiencies at Sanofi's Le Trait drug manufacturing plant in France.

Leerink analysts Geoffrey Porges and Seamus Fernandez said after viewing the Complete Response Letter (CRL) issued by the Food and Drug Administration (FDA), they realize there are more problems at the manufacturing plant than they originally thought, FiercePharma reported

“Frankly, now we have the (CRL) letter in hand, the list of issues cited is longer, and somewhat more concerning, than we had anticipated," the analysts said.

Regeneron and Sanofi received the CRL from the FDA in October 2016, where the agency cited numerous deficiencies identified during an inspection of Sanofi’s Le Trait facility. The CRL requires the companies to address the deficiencies before their drug can be approved in the United States. (For more, see Regeneron, Sanofi Drug Delayed by FDA.)

FDA Inspection Found Multiple Deficiencies

As a result, the biotech companies' sarilumab drug was delayed. But now ongoing deficiencies at Le Trait may force a delay of Regeneron and Sanofi's other drug, called Dupixent (dupilumab).

With the dupilumab’s PDUFA date (which is the deadline for the FDA to approve new drugs) is set for March 29, 2017, chances are high that along with sarilumab, the launch of dupilumab may also get impacted.

PDUFA dates are deadlines for the FDA to approve new drugs. The FDA is normally given 10 months to review new drugs.

While Regeneron and Sanofi are working together with the FDA to resolve issues, a Sanofi spokesperson maintains that dupilumab is not expected to be impacted as Sanofi works on the deficiencies.

An option to use another facility to fill and finish dupilumab does not appear realistic, as it may be difficult to get FDA approval for the new facility in time.

The rheumatoid arthritis drug sarilumab is expected to compete against AbbVie Inc.’s (ABBV) blockbuster drug Humira, which clocked sales of $14 billion last year. Sarilumab recently outperformed Humira in its Phase 3 trials. (For more, see Regeneron Arthritis Drug Outperforms Humira.)

Once approved, sarilumab sales are projected to hit $1.8 billion by 2020. (See also: Regeneron, Sanofi Report Drug Results.)

Dupixent is an eczema drug to treat adult patients with moderate-to-severe atopic dermatitis. It is projected to cost up to $30,000 a year and have annual sales of more than $5 billion. (For more, see Regeneron Win Review for Dermatitis Drug.)

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