Scientific and regulatory activities initiated by the U.S. Food and drug administration to foster approvals of generic dry powder inhalers: Bioequivalence perspective

Design, development, and technical considerations for dry powder inhaler devices

The dry powder inhaler (DPI) stands out as a highly patient-friendly and effective pulmonary formulation, surpassing traditional and other pulmonary dosage forms in certain disease conditions. The development of DPI products, however, presents more complexities than that of other dosage forms, particularly in device design and the integration of the drug formulation. This review focuses on the capabilities of DPI devices in pulmonary drug delivery, with a special emphasis on device design and formulation development. It also discusses into the principles of deep lung particle deposition and device engineering, and provides a current overview of the market for DPI devices. Furthermore, the review highlights the use of computational fluid dynamics (CFD) in DPI product design and discusses the regulatory environment surrounding these devices.

Regional lung targeting with a fluticasone/salmeterol aerosol using a bolus breath hold method of the PreciseInhale® system: A first evaluation in humans

BACKGROUND

In development of inhaled drugs- and formulations the measured concentration in the systemic circulation is often used as a surrogate for local dosimetry in the lungs. To further elucidate regional differences in the fate of drugs in the lungs, different aerodynamic sizes of aerosols have been used to target major airway regions. An alternative approach to achieve regional targeting of aerosols, is to use a defined aerosol bolus together with a bolus breath hold strategy. A small volume of test aerosol is intercalated and stopped at different penetration depths, to achieve increased drug deposition at chosen lung locations. Drug permeation from the lung regions is then investigated by repeatedly sampling venous blood from the systemic circulation. The PreciseInhale® (PI) exposure platform was developed to allow generation of aerosols from different sources, including clinical inhalers, into a holding chamber, for subsequent use with alternative exposure modules in vitro and in vivo. In the current first-in-human study was investigated the feasibility of a new clinical exposure module added to the PI system. By extracting aerosol puffs from a medical inhaler for subsequent delivery to volunteers, it was possible to administer whole lung exposures, as well as regional targeting exposures.

METHODS

Aerosols containing 250 µg/25 µg fluticasone propionate (FP)/salmeterol xinafoate (SMX) were automatically actuated and extracted from the pressurized Metered Dose Inhaler (pMDI) Evohaler Seretide forte into the PI system's holding chamber, then administered to the healthy volunteers using controlled flowrate and volume exposure cycles. Two main comparisons were made by measuring the systemic PK response: I. One label dose directly from the inhaler to the subject was compared to the same dose extracted from the pMDI into the PI system and then administered to the subject. II A small aerosol bolus at a penetration level in the central airways was compared to a small aerosol bolus at a penetration level in the peripheral lung.

RESULTS AND CONCLUSIONS

When one inhaler dose was administered via the PI system, the absorbed dose, expressed as AUC24, was approximately twice as high and the CV was less than half, compared to direct inhalation from the same pMDI. Bolus breath hold targeting of drugs from the same aerosol mixture to the peripheral lung and the central airways showed a difference in their appearance in the systemic circulation. Normalized to the same deposited dose, SMX had a 57 % higher Cmax in the peripheral lung compared to the central airways. However, from 6 to 24 h after dosing the systemic concentrations of SMX from both regions were quite similar. FP had parallel concentrations curves with a 23 % higher AUC24 in the peripheral lung with no noticeable elevation around Cmax. The permeability of these two substances from similar sized aerosols was indeed higher in the thinner air/blood barriers of the peripheral lung compared to the central airways, but differences as measured on the venous side of the circulation were not dramatic. In conclusion, the PI system provided better control of actuation, aspiration, and dispensation of aerosols from the clinical inhaler and thereby delivered higher quality read outs of pharmacokinetic parameters such as tmax, Cmax, and AUC. Improved performance, using PI system, can likely also be employed for studying regional selectivity of other responses in the lungs, for use in drug development.

Microstructural insight into inhalation powder blends through correlative multi-scale X-ray computed tomography

Dry powder inhalers (DPI) are important for topical drug delivery to the lungs, but characterising the pre-aerosolised powder microstructure is a key initial step in understanding the post-aerosolised blend performance. In this work, we characterise the pre-aerosolised 3D microstructure of an inhalation blend using correlative multi-scale X-ray Computed Tomography (XCT), identifying lactose and drug-rich phases at multiple length scales on the same sample. The drug-rich phase distribution across the sample is shown to be homogeneous on a bulk scale but heterogeneous on a particulate scale, with individual clusters containing different amounts of drug-rich phase, and different parts of a carrier particle coated with different amounts of drug-rich phase. Simple scalings of the drug-rich phase thickness with carrier particle size are used to derive the drug-proportion to carrier particle size relationship. This work opens new doors to micro-structural assessment of inhalation powders that could be invaluable for bioequivalence assessment of dry powder inhalers.

Patenting Strategies on Inhaler Delivery Devices

BACKGROUND

Patients with asthma and COPD rely on inhalers to control symptoms. Yet, these products remain expensive, in part because brand-name manufacturers have obtained numerous patents on inhalers, including on their delivery devices. Recent antitrust litigation has raised questions about the boundaries of listing device patents with the US Food and Drug Administration (FDA), particularly when patents do not claim any active ingredients.

RESEARCH QUESTION

How have manufacturers relied on device patents to preserve market exclusivity on brand-name inhalers?

STUDY DESIGN AND METHODS

We identified patents on brand-name inhalers approved for asthma and COPD between 1986 and 2020 using the FDA's Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book). We extracted information about patents from LexisNexis TotalPatent One and Google Patents and searched device patents for mention of active ingredients or other prespecified features linking the patent to the relevant drug. For each inhaler, we determined the duration of protection added by device patents.

RESULTS

The FDA approved 53 brand-name inhalers for asthma and COPD from 1986 through 2020, 39 of which had at least one device patent. One hundred thirty-seven distinct device patents were in the final cohort, representing 49% of all patents listed on inhalers. Seventy-seven percent of device patents made no mention of active ingredients or their molecular structures, and 72% made no mention of any relevant prespecified feature connecting the device patent to the drug product. For the 39 brand-name inhalers with one or more device patents listed in the Orange Book, device patents extended the duration of market protection by a median of 5.5 years (interquartile range, 0.0-10.5 years) beyond the last-to-expire nondevice patent.

INTERPRETATION

Patent and regulatory reform is needed to promote generic competition and to ensure that patients with asthma and COPD have access to affordable medications.

Scientific and regulatory activities initiated by the U.S. food and drug administration to foster approvals of generic dry powder inhalers: Quality perspective

Regulatory science for generic dry powder inhalation products worldwide has evolved over the last decade. The revised draft guidance Metered Dose Inhaler (MDI) and Dry Powder Inhaler (DPI) Products - Quality Considerations [1] (Revision 1, April 2018) that FDA issued summarizes product considerations and potential critical quality attributes (CQAs). This guidance emphasizes the need to apply the principles of quality by design (QbD) and elements of pharmaceutical development discussed in the International Conference for Harmonisation of (ICH) guidelines. Research studies related to quality were used to support guidance recommendations, which preceded the first approval of a generic DPI product in the U.S. This review outlines scientific and regulatory hurdles that need to be surmounted to successfully bring a generic DPI to the market. The goal of this review focuses on relevant issues and various challenges pertaining to CMC topics of the generic DPI quality attributes. Furthermore, this review provides recommendations to abbreviated new drug application (ANDA) applicants to expedite generic approvals.