Establishing bioequivalence for inhaled drugs; weighing the evidence

Generic dry powder inhalers bioequivalence: Batch-to-batch variability insights

Active pharmaceutical ingredient(s) [API(s)] of dry powder inhalers (DPIs) deposition and their fate in the respiratory system are influenced by a complex matrix of formulation, device, manufacturing and physiological variations. DPIs on the market have shown bioinequivalence between batches of the same product. Despite being clinically insignificant, they affect bioequivalence studies when a generic product is compared with the originator. This review discusses implications of batch-to-batch variability on bioequivalence study outcomes and shortcomings of current regulatory requirements. Possible formulation and manufacturing factors resulting in batch-to-batch variability highlight the inherent nature of this issue. Despite scholarly investigations and official regulatory guidance, there remains a need for reliable and realistic in vitro tests that accurately guide a representative reference product batch selection.

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.

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.

A new hypothesis to investigate bioequivalence of pharmaceutical inhalation products

BACKGROUND

This short communication reports a new hypothesis regarding bioequivalence of inhalation products which can potentially provide a reliable means to compare pharmaceutical aerosol formulations and inhalers.

METHODS

Available methods regarding the bioequivalence studies, inhaled drugs and advantages of exhaled breath condensate (EBC) samples were reviewed to develop this hypothesis.

RESULTS

It is postulated that two inhalation products providing the same drug concentrations in airway lining fluid (ALF) could be considered bioequivalent. The use of EBC tests which reflect ALF composition can be recommended as an alternative to current testing methods for consideration of bioequivalence.

CONCLUSION

The methods based on EBC analysis can potentially be applied to bioequivalence study of inhalation products and could reflect drug concentration in ALF. However, experimental studies would be necessary to support or refute this hypothesis on the novel application of EBC to bioequivalence in the future. Graphical abstract In vitro (cascade impactor) and In vivo (EBC concentration) corrolation for inhaled drugs.

Bioequivalence Evaluations of Generic Dry Powder Inhaler Drug Products: Similarities and Differences Between Japan, USA, and the European Union

In Japan, the development of generic oral dry powder inhaler (DPI) drug products for marketing approval has recently increased. The Pharmaceuticals and Medical Devices Agency (PMDA) considers the required data for each drug product in the consultation meeting. However, guidelines for DPI drug products have been published by the US Food and Drug Administration and the European Medicines Agency. Recently, the basic principles of bioequivalence evaluations of generic DPI drug products were published in March 2016 by the Ministry of Health, Labour and Welfare. The document mainly outlines the current understanding regarding the bioequivalence evaluations of generic DPI drug products based on knowledge from PMDA consultation meetings. In this review, we compared the bioequivalence evaluations of DPI drug products among Japan, USA, and the European Union and discuss future development of generic DPI drug products in Japan.

Pharmacokinetic properties and bioequivalence of orally inhaled salbutamol in healthy Chinese volunteers

CONTEXT

Salbutamol is a short-acting β2-adrenergic receptor agonist that has been used for many years for relief of bronchospasm. However, studies on the pharmacokinetic profile of orally inhaled salbutamol doses used in clinical practice have not yet been reported in Chinese subjects.

OBJECTIVE

The aim of this study was to compare the pharmacokinetics and evaluate the bioequivalence of two orally inhaled salbutamol formulations.

MATERIALS AND METHODS

A single-dose randomized fasting two-period, two-treatment and two-sequence crossover open-label bioequivalence study was conducted in 24 healthy Chinese adult male volunteers, with a 1-week washout period between treatments. Plasma concentrations of salbutamol were determined using liquid chromatography coupled to tandem mass spectrometry. Pharmacokinetic parameters, including AUC0-0.33 h, AUC0-24 h and Cmax were calculated and the 90% confidence intervals of the ratio (test/reference) pharmacokinetic parameters were obtained by analysis of variance on logarithmically transformed data.

RESULTS

The mean (SD) pharmacokinetic parameters of the reference drug were AUC0-0.33 h, 227.2 (89.9) pg·h/ml; AUC0-24 h, 2551.9 (1008.0) pg·h/ml; Cmax, 801.3 (307.3) pg/ml and t1/2, 5.14(1.36) h. Those of the test drug were AUC0-0.33 h, 244.0 (104.4) pg·h/ml; AUC0-24 h, 2664.4 (1081.8) pg·h/ml; Cmax, 873.7 (374.4) pg/ml, t1/2, 5.29 (1.23) h. The median value for Tmax was 0.25 h for both formulations. The 90% confidence intervals for the AUC0-0.33 h, AUC0-24 h and Cmax were in the range of 0.892-1.208, 0.876-1.195 and 0.911-1.203, respectively.

CONCLUSION

This single-dose study found that the test and reference products met the regulatory criteria for bioequivalence of China in healthy Chinese volunteers.

Switching treatments in COPD: implications for costs and treatment adherence

Inhaled therapy is key to the management of chronic obstructive pulmonary disease (COPD). New drugs and inhalers have recently been launched or will soon become available, and the expiry of patent protection covering several currently used inhaled bronchodilators and corticosteroids will be accompanied by the development of bioequivalent, generic inhaled drugs. Consequently, a broader availability of branded and generic compounds will increase prescription opportunities. Given the time course of COPD, patients are likely to switch drugs and inhalers in daily practice. Switching from one device to another, if not accompanied by appropriate training for the patient, can be associated with poor clinical outcomes and increased use of health care resources. In fact, while it seems reasonable to prescribe generic inhaled drugs to reduce costs, inadequate use of inhaler devices, which is often associated with a poor patient–physician or patient–pharmacist relationship, is one of the most common reasons for failure to achieve COPD treatment outcomes. Further research is needed to quantify, as in asthma, the impact of inappropriate switching of inhalers in patients with COPD and show the outcomes related to the effect of using the same device for delivering inhaled medications.

Asthma and COPD: Interchangeable use of inhalers. A document of Italian Society of Allergy, Asthma and Clinical Immmunology (SIAAIC) & Italian Society of Respiratory Medicine (SIMeR)

Prescription cost-containment measures are increasing in many European countries and, as more inhaler devices become available, there may be pressure to switch patients from reference inhaled medication to cheaper generic inhaled drugs. Indeed, in some countries, such a substitution is mandated by current regulations, and patients who do not accept the substitution have to pay the difference in cost. Generic inhaled drugs are therapeutically equivalent to original branded options but may differ in their formulation and inhalation device. This new situation raises questions about the potential impact of switching from branded to generic inhaled medications in patients with asthma or chronic obstructive pulmonary disease (COPD), with or without their consent, in countries where this is permitted. Acquisition cost savings from a substitution could be offset by costs related to deterioration in asthma control or worsening in COPD outcomes if the patient is unable or unwilling to use the inhaler device properly. Non-adherence to therapy and incorrect inhaler usage are recognised as major factors in uncontrolled asthma and worsening of COPD outcomes. Switching patients to a different inhaler device may exacerbate these problems, particularly in patients who disagree to switch. Where switching is permitted or mandatory, it is crucial that the reason for switching has been properly explained to the patient and adequate instruction for operating correctly the inhaler have clearly been provided.

[The choice of inhalation device: A medical act]

Inhaled treatments are essential for respiratory diseases management, including COPD and asthma. Optimal control of the disease largely depends on patient's compliance and proper use of these treatments. Different types of ready-to-use inhaler devices are available: metered dose inhaler, dry powder inhaler or soft mist inhaler. Each of these devices presents specific characteristics and constraints that have to be evaluated and taken into account before prescription. In order to optimize adherence and treatment efficacy, the choice of inhaler device should depend on the specific needs, abilities and preferences of each patient and a specific education to treatment should be provided. Inhaled treatments, even containing the same drug, have different technical constraints and are thus not easily interchangeable. Their substitution without prior medical consent and without proper training can lead to errors in taking treatment, treatment failures and increased health care consumption. In France, substitution by the pharmacist is not authorized. While patient education must be carried out in collaboration with all health professionals, it is preferable that the choice of inhaler device remains the responsibility of the physician.

Switching from branded to generic inhaled medications: potential impact on asthma and COPD

Pressure on healthcare budgets is increasing, while at the same time patent protection for many branded inhaled medications has expired, leading to the development and growing availability of generic inhaled medicines. Generic inhaled drugs are therapeutically equivalent to original branded options but may differ in their formulation and inhalation device. This new situation raises questions about the potential impact of switching from branded to generic drug/inhaler combination products in patients with asthma or COPD, with or without their consent, in countries where this is permitted. Inhalation devices, particularly dry powder inhalers, vary markedly in their design, method of operation and drug delivery to the lungs. Current guidelines stress the importance of training patients how to use their inhalers but offer little or no guidance on how this should be achieved. Non-adherence to therapy and incorrect inhaler usage are recognised as major factors in poorly or uncontrolled asthma and COPD and switching patients to a different inhaler device may exacerbate these problems, particularly in patients who disagree to switch. Where switching is permitted or mandatory, adequate patient instruction and follow-up monitoring should be provided routinely.

Pharmacokinetics and pharmacodynamics of fluticasone propionate and salmeterol delivered as a combination dry powder from a capsule-based inhaler and a multidose inhaler in asthma and COPD patients

BACKGROUND

The object of this study was to assess whether a capsule-based and multidose dry powder inhaler containing salmeterol (as xinafoate salt) 50 μg plus fluticasone propionate (FP) 250 μg [combination (SFC 50/250)] could be equivalent in terms of in vivo drug delivery and systemic exposure.

METHODS

This was a randomized, double-blind, double-dummy, replicate treatment design comparative bioavailability study of SFC 50/250 delivered in a capsule-based inhaler (Rotahaler®) and a multidose dry powder inhaler (Diskus®). Subjects with asthma or chronic obstructive pulmonary (COPD) disease (n=60) were randomized to receive twice-daily SFC 50/250 via a Rotahaler and via Diskus each for two 10-day treatment periods (GlaxoSmithKline Protocol ASR114334).

RESULTS

For FP and salmeterol, the in vitro aerodynamic particle size profiles were within±15% of Diskus for the fine particle mass (FPM) and emitted dose (ED) using the Andersen Cascade Impactor, and ED, mass median aerodynamic diameter, and geometric standard deviation using the New Generation Impactor (NGI). This was also the case for FP but not salmeterol for FPM and fine particle dose using the NGI. For the combined asthma and COPD subjects, the plasma AUC and Cmax for FP and salmeterol were higher for Rotahaler:Rotahaler/Diskus geometric mean ratios (90% confidence intervals) for FP AUC0-τ of 1.52 (1.37-1.67) and Cmax of 1.94 (1.75-2.10) and salmeterol AUC0-τ of 1.15 (1.09-1.21) and Cmax of 1.56 (1.42-1.67). Corresponding values for the primary pharmacodynamic endpoint, weighted mean (0-12 hr) serum cortisol, were 0.928 (0.886-0.971). Inhaled FP/salmeterol via both inhalers was well-tolerated. One serious adverse event, considered possibly related to study medication, resulted in subject withdrawal from the study.

CONCLUSIONS

The in vitro tests and systemic pharmacodynamic endpoints revealed no major differences between the two inhalers, but lacked predictive power and sensitivity to guide in vivo drug delivery performance and systemic exposure. Based on pharmacokinetic endpoints, the inhalers were not considered bioequivalent in terms of systemic exposure. Further studies to refine the Rotahaler performance are ongoing.

Bioequivalence of inhaled drugs: fundamentals, challenges and perspectives

Interest in bioequivalence (BE) of inhaled drugs derives largely from the desire to offer generic substitutes to successful drug products. The complexity of aerosol dosage forms renders them difficult to mimic and raises questions regarding definitions of similarities and those properties that must be controlled to guarantee both the quality and the efficacy of the product. Despite a high level of enthusiasm to identify and control desirable properties there is no clear guidance, regulatory or scientific, for the variety of aerosol dosage forms, on practical measures of BE from which products can be developed. As more data on the pharmaceutical and clinical relevance of various techniques, as described in this review, become available, it is likely that a path to the demonstration of BE will become evident. In the meantime, debate on this topic will continue.

Effect of device design on the in vitro performance and comparability for capsule-based dry powder inhalers

This study investigated the effect of modifying the design of the Cyclohaler on its aerosolization performance and comparability to the HandiHaler at multiple flow rates. The Cyclohaler and HandiHaler were designated as model test and reference unit-dose, capsule-based dry powder inhalers (DPIs), respectively. The flow field, pressure drop, and carrier particle trajectories within the Cyclohaler and HandiHaler were modeled via computational fluid dynamics (CFD). With the goal of achieving in vitro comparability to the HandiHaler, the CFD results were used to identify key device attributes and to design two modifications of the Cyclohaler (Mod 1 and Mod 2), which matched the specific resistance of the HandiHaler but exhibited different cyclonic flow conditions in the device. Aerosolization performance of the four DPI devices was evaluated by using the reference product's capsule and formulation (Spiriva capsule) and a multistage cascade impactor. The in vitro data showed that Mod 2 provided a closer match to the HandiHaler than the Cyclohaler and Mod 1 at 20, 39, and 55 l/min. The in vitro and CFD results together suggest that matching the resistance of test and reference DPI devices is not sufficient to attain comparable aerosolization performance, and the improved in vitro comparability of Mod 2 to the HandiHaler may be related to the greater degree of similarities of the flow rate of air through the pierced capsule (Q(c)) and the maximum impact velocity of representative carrier particles (V(n)) in the Cyclohaler-based device. This investigation illustrates the importance of enhanced product understanding, in this case through the CFD modeling and in vitro characterization of aerosolization performance, to enable identification and modification of key design features of a test DPI device for achieving comparable aerosolization performance to the reference DPI device.