FDA approves MannKind's Afrezza for T1DM and T2DM, but restrictions and lack of benefits in label may limit uptake
On 27 June 2014, the FDA approved MannKind's pulmonary insulin Afrezza for the treatment of adult patients with T1DM and T2DM, however with a number of restrictions. The label does not contain comparative data vs NovoRapid® regarding hypoglycaemia or weight as claimed by MannKind to be key advantages. Further, the ultrafast absorption seen in a small PK/PD study did not translate into faster onset of action vs injectable fast-acting insulin. (MannKind and FDA press releases, 27 June 2014, and US label) Comment: In 2013, MannKind published top-line results from the two pivotal 24-week phase 3 trials AFFINITY-1 and -2 in T1DM and T2DM patients, respectively. In T1DM, Afrezza showed benefits on hypoglycaemia and weight vs NovoRapid®; however, efficacy was not compelling. Although within the non-inferiority margin of 0.4%, Afrezza was statistically inferior to NovoRapid®, which also was not titrated optimally. At the AdComm meeting for Afrezza on 1 April 2014, the Agency already stated its belief that the lower hypoglycaemia rate and weight benefit vs NovoRapid® is linked to lower efficacy of Afrezza. US label includes boxed warning on the risk of bronchospasm in patients with chronic lung disease Afrezza is contraindicated in patients with chronic lung disease including asthma and COPD due to risk of acute bronchospasm. Before initiating therapy, detailed medical history, physical examination and spirometry (FEV1) must be performed prior to initiation to identify potential lung disease. Afrezza is not recommended in patients who smoke or who have recently stopped smoking, as safety and efficacy has not been established in this population. In addition, Afrezza is not recommend for the treatment of diabetic ketoacidosis. Most common side effect is cough which in clinical trials occurred in ~27% of patients treated with Afrezza vs ~5% on comparators. Anti-insulin antibodies were observed more frequently with Afrezza than with sc prandial insulins; however, this did not correlate with reduced efficacy.
Comment: In clinical trials, pulmonary function as assessed by Forced Expiratory Volume in 1 sec (FEV1) declined on average by 40 ml with Afrezza vs comparators over two years, which was considered clinically non-significant. However, these data are insufficient to evaluate long-term safety. A higher rate of diabetic ketoacidosis was seen with Afrezza in T1DM: 13 vs 3 cases with comparators, indicating lack of efficacy in certain patients.
Afrezza's approval comes with a REMS and requirements for additional clinical trials FDA has approved Afrezza with a Risk Evaluation and Mitigation Strategy (REMS) consisting of a communication plan regarding the risk of acute bronchospasm. Pulmonary function (FEV1) should be assessed at baseline, after the first six months, and annually thereafter. Post-marketing requirements further include the following clinical studies:
•§A PK, safety and efficacy trial in paediatric patients
•§A trial to evaluate the potential risk of lung cancer, cardiovascular risk and the long-term effect on pulmonary function
•§Two PK/PD euglycaemic clamp trials, one to characterise dose-response and one to characterise within-subject variability
Comment: Two cases of lung cancer were reported in the clinical trials (both smokers) and two cases of a rare type of lung cancer in non-smokers were reported following 2.5 and 3.5 years, respectively. No lung cancer cases were reported in comparator-exposed patients. As the four cancer cases are not out of line with the expected background rate, these data are inconclusive. In the clinical trial programme, 19.6% of subjects had a history of cardiovascular disease. Although cardiovascular risk evaluation was not predefined, analyses showed no signal of increased risk.
Use of Afrezza is restricted in specific populations Afrezza is not indicated for use in children until a post-marketing study has been conducted. In addition, the drug should not be used in pregnant or lactating woman. Geriatric patients were included in the clinical trials, with 381 patients being ≥65 years of age, of which 20 were ≥75 years of age.
Afrezza should be dosed at the beginning of the meal by a single inhalation per cartridge Afrezza comes in two dose strengths: a 4 unit (blue) cartridge and an 8 unit (green) cartridge. Hence, patients needing >8 units per meal will have to inhale more than once. Cartridges are supplied in blister cards with five strips of three cartridges per card. At dosing, the cartridge must have been at room temperature for 10 min. If the inhaler is turned upside down, held with the mouthpiece pointing down, shaken or dropped after cartridge insertion, the drug effect may be lost and the cartridge should be replaced. Comment: The cartridges contain 10 U and 20 U of insulin, equivalent to 4 and 8 units of injected insulin, respectively. MannKind had at submission proposed a different conversion factor: equivalence to 3 and 6 units of injected insulin, respectively. However, the FDA found that this conversion was not in accordance with the dosing regimens used in the clinical trials. Lack of favourable comparative label claims reduces the competitiveness of Afrezza MannKind aims to launch Afrezza in the second half of 2014, but the company has so far not secured a partnership for commercialisation. The price is planned to be on par with prandial insulin analogues in prefilled pens. MannKind has indicated that Afrezza will be targeted for T2DM patients as add-on to OADs as well as for existing prandial insulin users; however, most likely Afrezza will primarily be used by subgroups of patients. Commercial success not only requires a partner but also a change in treatment paradigm, as most T2DM patients in the US start insulin treatment with basal insulin.
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