Mannkind's (MNKD 2.00%) continued battle for FDA approval of its short-acting inhalable insulin Afrezza isn't looking good following release of documents for this week's FDA panel meeting April 1. A final decision is set for April 15.
So, what does the data say?
Mannkind produced results from two new studies for Afrezza, but the conclusions were lackluster at best.
In treating diabetes type 1, the new study compared Afrezza to injectable insulin aspart, both to be used with an injected basal insulin. The study did meet its primary endpoint of noninferiority (barely meeting the margin of 0.4%) to insulin aspart, but Afrezza still underperformed compared to aspart. Patients in the Afrezza arm required more basal insulin than the insulin aspart group, and the Afrezza group's insulin was titrated up while the aspart group's was not, possibly minimizing the difference between Afrezza and aspart.
In short, Afrezza as a treatment for diabetes type 1? Technically "not inferior" per the one study, but there are enough questions that it could well be inferior. As the reviewer's comment on page 83 notes, "it is not clear how to interpret the results of this non-inferiority study."
In treating diabetes type 2, studies compared Afrezza to placebo (no insulin), both in conjunction with oral antidiabetic drugs. Afrezza did show improvement as compared to placebo, but a "surprisingly modest" one given that any insulin versus no insulin should show significant advantage.
In short, Afrezza as a treatment for diabetes type 2? Superior, but not as much as it should. Nonetheless, the more likely approval (if any) for Afrezza appears to be for type 2 diabetes over type 1.
Pfizer's cautionary tale
The FDA documents are riddled with comparisons to Exubera, Pfizer's (PFE 0.65%) attempt at an inhalable insulin. Exubera was the first inhalable insulin to hit the market, but the agent was ditched in 2007 following poor sales.
Physicians and patients both never took to the rapid-acting inhalable insulin, especially given difficult dosing and significant concern over serious respiratory infection and questionable association with lung cancer. Notably, the association with lung cancer was shown to be statistically insignificant later and more prominently seen in patients with known tobacco history.
Mannkind has worked hard to establish why Afrezza is not going to be another Exubera. But similar to Exubera, safety concerns again rear up. While the data clearly shows there is no increase in respiratory infections, other lung issues do arise, including coughing and bronchospasm and pulmonary function decline, both of which may limit use in patients with preexisting lung disease.
Even if Afrezza makes it past the FDA on safety, just the mention of respiratory side effects will inevitably bring back to mind the failure of Exubera and again may limit adoption by physicians and patients. Approval is the first of Mannkind's concerns, but Pfizer showed that approval does not necessarily translate into sales.
Third time's the charm?
Mannkind has already weathered two rejections for Afrezza. During that time, many others have tried and ditched their own efforts for an inhalable insulin, including diabetes giants Eli Lilly & Co. (with Alkermes) and Novo Nordisk (with Aradigm).
The prognosis for this next round of FDA review over Afrezza is not good, to my mind. Data for type 1 diabetes is not encouraging, and data for type 2 diabetes is underwhelming at best. Coupled with a very complicated dosing equation, questions on delivery, and concerns over safety, it may be three strikes -- Mannkind's out.