The USA’s MannKind Corp says it is determined to push ahead with its investigational inhaled insulin product, despite Eli Lilly becoming the latest firm to decide that such treatments have little commercial value.

Last Friday, Lilly pulled the plug on its AIR inhaled insulin programme with Alkermes, following in the footsteps of Novo Nordisk which halted development of AERx in January. Most high-profile of all was Pfizer’s decision last October to stop marketing Exubera after it failed to make any impact in the diabetes marketplace.

Mannkind has responded to the Lilly pull-out by saying that it is “absolutely committed” to the continued development of its Technosphere Insulin programme, which is in Phase III trials. The firm noted that “that in order to be successful in today's health care market a product must offer improved efficacy and safety, not just improved convenience” and the decisions of Lilly, Pfizer and Novo Nordisk to discontinue the development of their inhaled insulin products “reinforce this view”.

The problem with those three, Mannkind argues is that “none of those products offer any advantages over injectable rapid-acting insulin analogues. However it claims that Technosphere Insulin, has an effectiveness and safety profile that is "clearly differentiated from all existing diabetes treatments”.

Specifically, MannKind says its small, patient-friendly Medtone inhaler delivers the drug in a way that much more closely matches the pattern of insulin secretion seen in people without diabetes and Technosphere is the only therapy, among other benefits, that “separately and independently lowers prandial glucose excursions.”

The firm acknowledges that “physicians and regulatory agencies are cautious about a new route of administration” and is therefore conducting “a very robust clinical trial programme involving more than 5,000 patients with diabetes”. It has also undertaken a more comprehensive examination of the toxicology profile of Technosphere “than has been reported for any other inhaled insulin”.

Mannkind concluded by saying that it has sufficient financial resources to fund its insulin programmes and others through the end of 2009. However its enthusiasm does not seem to be shared by investors and the firm’s share price fell 9.6% to $4.99.