Mannkind Corp needs to give more information to regulators in the USA before its inhaled insulin treatment Afrezza will get approval.

The US Food and Drug Administration has issued a complete response letter regarding the New Drug Application for Afrezza, which precludes approval in the current form of the filing. Mannkind says the letter has requested “several items, including information and currently-available clinical data that support the clinical utility of Afrezza”.

The agency also wants more information about the comparability of the commercial version of the MedTone inhaler to the earlier version used in Phase III trials. The letter also requested changes to the proposed labelling of the cartridges, foil pouches and cartons used with the device.

The letter cited no safety concerns (but did request updated safety data) and Mannkind stressed that the FDA does not require any additional pre-marketing clinical studies in order to complete its review. Chief executive Alfred Mann said the company will respond “in a timely manner”, noting that “we had always planned to follow the original NDA for Afrezza with a regulatory submission for our next-generation inhaler”.

He went on to say that rather than launch with the commercial version of the MedTone device. “we will discuss with the FDA whether it is appropriate to use what would otherwise have been a supplemental NDA submission”, which would have been made during the second quarter. Mr Mann added that “if this approach is acceptable, we believe that this regulatory action will not have a significant impact on the timing of the commercial launch of Afrezza”.

Nevertheless, MannKind’s shares have taken a hit as investors expressed concerned about inhaled insulin as a viable treatment. In recent years, Eli Lilly and diabetes specialist Novo Nordisk have abandoned the field and in October 2007, Pfizer pulled its inhaled insulin therapy Exubera after it failed to make any impact in the diabetes market.

Simos Simeonidis and Yatin Suneja, analysts at Rodman & Renshaw, described the FDA's letter as "benign", saying that the issues brought up "can be addressed without significant delays". They noted that "obviously, a straight approval would have been the ideal scenario for MannKind holders", but the news means that "Afrezza approval is still very much alive, and with significant overhangs removed".