Rethinking bioequivalence and equivalence requirements of orally inhaled drug products

Innovating on Inhaled Bioequivalence: A Critical Analysis of the Current Limitations, Potential Solutions and Stakeholders of the Process

Orally inhaled drug products (OIDPs) are an important group of medicines traditionally used to treat pulmonary diseases. Over the past decade, this trend has broadened, increasing their use in other conditions such as diabetes, expanding the interest in this administration route. Thus, the bioequivalence of OIDPs is more important than ever, aiming to increase access to affordable, safe and effective medicines, which translates into better public health policies. However, regulatory agencies leading the bioequivalence process are still deciding the best approach for ensuring a proposed inhalable product is bioequivalent. This lack of agreement translates into less cost-effective strategies to determine bioequivalence, discouraging innovation in this field. The Next-Generation Impactor (NGI) is an example of the slow pace at which the inhalation field evolves. The NGI was officially implemented in 2003, being the last equipment innovation for OIDP characterization. Even though it was a breakthrough in the field, it did not solve other deficiencies of the BE process such as dissolution rate analysis on physiologically relevant conditions, being the last attempt of transferring technology into the field. This review aims to reveal the steps required for innovation in the regulations defining the bioequivalence of OIDPs, elucidating the pitfalls of implementing new technologies in the current standards. To do so, we collected the opinion of experts from the literature to explain these trends, showing, for the first time, the stakeholders of the OIDP market. This review analyzes the stakeholders involved in the development, improvement and implementation of methodologies that can help assess bioequivalence between OIDPs. Additionally, it presents a list of methods potentially useful to overcome some of the current limitations of the bioequivalence standard methodologies. Finally, we review one of the most revolutionary approaches, the inhaled Biopharmaceutical Classification System (IBCs), which can help establish priorities and order in both the innovation process and in regulations for OIDPs.

A sensitive and high-throughput LC-ESI-MS/MS method to detect budesonide in human plasma: application to an evaluation of pharmacokinetics of budesonide intranasal formulations with and without charcoal-block in healthy volunteers

Budesonide is one of the intranasal corticosteroids, referred as first-line therapy for allergic rhinitis. Its determination is a challenging task due to its extremely low plasma levels, which limits the progress in the investigation of pharmacokinetics and quality control of preparations. In this study, a sensitive and high-throughput method to determine budesonide in human plasma using budesonide-d8 as the internal standard was developed and validated. A small volume of plasma sample (0.2 mL) was diluted with 0.2 mL water, followed by a solid-phase extraction using Cleanert PEP-2 products. Extracted samples were analyzed by liquid chromatography coupled to electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Chromatographic separation of analytes was performed on an InertSustain AQ-C18 HP column (3 µm, 2.1 × 50 mm) under the reversed-phase condition with gradient elution. With the assay, linear calibration curves were obtained over the concentration range of 10-1200 pg/mL for budesonide, with considerable extraction recoveries (84.7-89.4%), and negligible matrix effects (<4.1). Moreover, the newly developed method was successfully applied to the evaluation of pharmacokinetics of two budesonide intranasal formulations with and without charcoal block in healthy volunteers.

Bioequivalence studies of inhaled indacaterol maleate in healthy Chinese volunteers under gastrointestinal non-blocking or blocking with concomitant charcoal administration

BACKGROUND

Indacaterol is one of the long-acting beta₂-adrenergic agonists, referred as first-line monotherapy for Chronic obstructive pulmonary disease since 2011. Generic products are encouraged to benefit the large COPD patients in China, in which can provide more choices association with reduced cost and improve the quality of patient life.

OBJECTIVE

The three-part study consists of two independent cohorts of thirty-six subjects, aimed to evaluate the bioequivalence (BE) of two indacaterol formulations in gastrointestinal (GI) absorption charcoal-block or non-block conditions. One pilot study performed in six healthy subjects to determine the blocking effect of a new charcoal-based regimen on GI absorption after orally inhalation of indacaterol.

METHODS

Two BE studies were conducted with a randomized, open-label, 2-period crossover design in two independent 36-healthy-subject cohorts, equivalence in systemic and lung deposition was assessed after inhalation of a single dose of 150 μg indacaterol (test or reference formulation) alone or concomitant administration of charcoal. The charcoal-based regimen was improved by optimizing the dose and number of doses, and its blocking efficacy against GI absorption was assessed in a pilot study. Six healthy subjects received 9 g charcoal 10 min before, immediately after and 2 h after indacaterol (3 g/100 ml water × 3 times). Blood collected at predetermined time points up to 72 h. Plasma indacaterol concentrations were determined using HPLC-MS/MS. Pharmacokinetics parameters were calculated with non-compartment analysis. Equivalences were concluded if the 90% confidence interval (CI) for test: reference of C_max and AUC_0-t fell within the limits of 0.8-1.25.

RESULTS

Indacaterol was undetectable in plasma samples in pilot study. The T/R ratio of the geometric mean C_max and AUC_0-t was 109.9% (90% CI, 106.1-113.8%) and 104.8% (90% CI, 101.5-108.1%) for charcoal-block subjects and 105.4% (90% CI, 99.8% ~ 111.3%), and 101.0% (90% CI, 97.7%-104.4%) for non-block subjects. No serious adverse events were reported.

CONCLUSIONS

The results showed that 150 μg indacaterol (+/- 9 g charcoal) was well tolerated in all subjects. The two formulations are bioequivalent in terms of the rate and absorption both in charcoal-block and non-block conditions. The improved charcoal-based regimen demonstrated to be effective and fully blockade of GI absorption of indacaterol.

Understanding the Essentialities in Establishing the Bioequivalence of Oral Inhalation Drug Products to be Marketed in the USA

BACKGROUND

Oral inhalation drug products (OIDPs) are combination products comprising two components, i.e., a device and the corresponding formulation, and are manufactured with 'patient use' being the key consideration. The formulation is designed to be compatible with the device, as the device and formulation have to work in tandem for the intended effect of the drug to be imparted to the patient. OIDPs are generally categorized into three sections: pressurized metered dose inhalers (pMDIs or MDIs), dry powder inhalers (DPIs), and nebulizers.

AREA COVERED

As OIDPs are most convenient in the treatment of asthma and COPD, it makes these drugs all the more vital in terms of inhalational therapy. The introduction and sustenance of a generic market for these drugs is extremely essential as prices of innovator OIDPs have always been a point of contention with respect to ensuring adequate patient care. Since generic drug approvals require the conduct of bioequivalence studies, it becomes imperative for regulatory authorities to establish strict guidelines for the same. For a long time now, the lack of an appropriate approach for the conduct of bioequivalence studies for OIDPs has proven to be a major obstacle.

EXPERT OPINION

With the publication of individual guidance documents for OIDPs, the US FDA has paved a path for future approvals of generic OIDPs guided by the ideology that "no one-size-fits-all." This approach, known as the "weight-of-evidence" approach, requires manufacturers to submit in vitro studies, pharmacokinetic studies, and pharmacodynamic studies, in order to seek authorization for marketing generic OIDPs.

Opportunities and Challenges Related to the Implementation of Model-Based Bioequivalence Criteria

The science of bioequivalence and biosimilarity has greatly evolved over the past 3 decades. Current methods for assessing bioequivalence mostly rely on noncompartmental pharmacokinetic (PK) analyses, which have proven to be reliable and robust for most products. However, the development of more complex products is forcing scientists and regulators to consider alternative approaches, including those derived from model-based population PK analyses. This article will examine the strengths and weaknesses of standard noncompartmental methods and compare them to model-based approaches, including a comparison of metrics associated with each method. Specific situations for which model-based approaches could prove to be more suitable will be presented, as well as potential bioequivalence metrics that could be considered for bioequivalence comparisons. The opportunities and challenges that are associated with these novel methods will also be discussed.