After a week of excitable predictions from industry observers, MannKind Corp has revealed that a US regulatory review of its inhaled insulin therapy is going to take a bit longer.

The US Food and Drug Admininstration has told the firm it will not be able to complete the review of its New Drug Application for its ultra rapid-acting insulin therapy, which will be marketed as Afrezza and was previously known as Afresa, by the action date of January 16. This announcement comes after a week of speculation from analysts as to whether the treatment was going to get the agency’s green light.

MannKind’s shares fell some 5% in after-hours trading once the news emerged but closer inspection suggests that the delay is not necessarily bad news. The company believes that the only problem seems to be that the FDA has not completed the inspection of the insulin manufacturing facility of Organon, a subsidiary of Merck which is a third-party supplier to MannKind.

Chief executive Alfred Mann said that “to our knowledge, all other FDA inspections of third-party suppliers and clinical trial sites are complete”, as is the pre-approval inspection of MannKind’s manufacturing facility in Danbury, Connecticut. He added that “at this time, there are no pending answers to any FDA questions or other deliverables due on MannKind's part”.

The company also noted that it has discussed the basis for obtaining a waiver and deferral for paediatric studies with the FDA. MannKind has agreed to conduct a Phase IV study of Afrezza in 500 children aged at least four.

Simos Simeonidis, an analyst at Rodman & Renshaw, issued a research note saying that “the delay itself does not signify anything negative or positive about what the final decision on the NDA may be”. He added that “we see this as simply a case of the agency not being able to complete the review on time and/or dropping the ball and not realising they hadn’t inspected all the sites”.

Mr Simeonidis went on to say that “given the high-profile nature of inhalable insulin,” there is always the possibility that “higher level officials at the FDA that had not yet been heavily involved with the NDA up to this point may decide it would be prudent to put Afrezza in front of an advisory panel”. He said that would be interpreted as negative by the market but “it would be more of a case of the FDA officials wanting to protect themselves by adding an extra layer of expert opinion, than anything else”.

MannKind has not yet been informed about the expected timing for the agency’s final determination on the NDA but Mr Simeonidis expects a decision anytime between two to four weeks from now, barring the need for an advisory panel, which would delay the process by two-three months. He concluded by saying “we continue to believe that Afrezza and MannKind will pull the upset of 2010 and receive an approval this year”.