Determining topical product bioequivalence with stimulated Raman scattering microscopy

Generic drugs are essential for affordable medicine and improving accessibility to treatments. Bioequivalence (BE) is typically demonstrated by assessing a generic product's pharmacokinetics (PK) relative to a reference-listed drug (RLD). Accurately estimating cutaneous PK (cPK) at or near the site of action can be challenging for locally acting topical products. Certain cPK approaches are available for assessing local bioavailability (BA) in the skin. Stimulated Raman scattering (SRS) microscopy has unique capabilities enabling continuous, high spatial and temporal resolution and quantitative imaging of drugs within the skin. In this paper, we developed an approach based on SRS and a polymer-based standard reference for the evaluation of topical product BA and BE in human skin ex vivo. BE assessment of tazarotene-containing formulations was achieved using cPK parameters obtained within different skin microstructures. The establishment of BE between the RLD and an approved generic product was successfully demonstrated. Interestingly, within the constraints of the current study design the results suggest similar BA between the tested gel formulation and the reference cream formulation, despite the differences in the formulation/dosage form. Another formulation containing polyethylene glycol as the vehicle was demonstrated to be not bioequivalent to the RLD. Compared to using the SRS approach without a standard reference, the developed approach enabled more consistent and reproducible results, which is crucial in BE assessment. The abundant information from the developed approach can help to systematically identify key areas of study design that will enable a better comparison of topical products and support an assessment of BE.

Sensitivity of Pharmacokinetics to Differences in the Particle Size Distribution for Formulations of Locally Acting Mometasone Furoate Suspension-Based Nasal Sprays

To assess bioequivalence of locally acting suspension-based nasal sprays, the U.S. FDA currently recommends a weight-of-evidence approach. In addition to in vitro and human pharmacokinetic (PK) studies, this includes a comparative clinical endpoint study to ensure equivalent bioavailability of the active pharmaceutical ingredient (API) at the site of action. The present study aimed to assess, within an in vitro/in vivo correlation paradigm, whether PK studies and dissolution kinetics are sensitive to differences in drug particle size for a locally acting suspension-based nasal spray product. Two investigational suspension-based nasal formulations of mometasone furoate (MF-I and MF-II; delivered dose: 180 μg) differed in API particle size and were compared in a single-center, double-blind, single-dose, randomized, two-way crossover PK study in 44 healthy subjects with oral charcoal block. Morphology-directed Raman spectroscopy yielded volume median diameters of 3.17 μm for MF-I and 5.50 μm for MF-II, and dissolution studies showed that MF-II had a slower dissolution profile than MF-I. The formulation with larger API particles (MF-II) showed a 45% smaller Cmax and 45% smaller AUC0-inf compared to those of MF-I. Systemic bioavailability of MF-I (2.20%) and MF-II (1.18%) correlated well with the dissolution kinetics, with the faster dissolving formulation yielding the higher bioavailability. This agreement between pharmacokinetics and dissolution kinetics cross-validated both methods and supported their use in assessing potential differences in slowly dissolving suspension-based nasal spray products.

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

Regulatory science for generic dry powder inhalers (DPIs) in the United States (U.S.) has evolved over the last decade. In 2013, the U.S. Food and Drug Administration (FDA) published the draft product-specific guidance (PSG) for fluticasone propionate and salmeterol xinafoate inhalation powder. This was the first PSG for a DPI available in the U.S., which provided details on a weight-of-evidence approach for establishing bioequivalence (BE). A variety of research activities including in vivo and in vitro studies were used to support these recommendations, which have led to the first approval of a generic DPI in the U.S. for fluticasone propionate and salmeterol xinafoate inhalation powder in January of 2019. This review describes the scientific and regulatory activities that have been initiated by FDA to support the current BE recommendations for DPIs that led to the first generic DPI approvals, as well as research with novel in vitro and in silico methods that may potentially facilitate generic DPI development and approval.

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.

Medication Cost-Savings and Utilization of Generic Inhaled Corticosteroid (ICS) and Long-Acting Beta-Agonist (LABA) Drug Products in the USA

BACKGROUND

In the USA, drug costs associated with the inhaled corticosteroid (ICS) and long acting β agonist (LABA) combination products have been increasing since 2001. In January 2019, the first generic ICS/LABA drug product was approved by the U.S. Food and Drug Administration.

METHODS

We investigated retrospectively the effects of the first approved generic ICS/LABA drug from 2019 to 2020 on the wholesale cost-savings and prescription dispensing using the IQVIA data system in the USA.

RESULTS

The marketing of the first generic for fluticasone propionate and salmeterol xinafoate dry powder inhaler was associated with $941 million in drug cost-savings during the first year for this class of medications. Although the brand-name drug manufacturer concurrently introduced its authorized generic, these cost-savings were driven by the averaged unit cost of the approved generic at $115, compared to $169 for the authorized generic and $334 for the branded product. Generic initiation and substitution with the first generic were, respectively, higher compared to those with authorized generics; however, overall dispensing of the first generic was lower than that of its branded product. As in the case of budesonide and formoterol fumarate dry powder inhaler, marketing of authorized generics alone was not associated with any noticeable change in sales or prescription cost-saving.

CONCLUSION

We estimated that more than 20% of prescription cost-saving was achieved for the ICS/LABA dry powder inhalers in the first year following the introduction of the first approved generic, even though generic utilization remained lower than that of the branded counterpart.

Scientific and Regulatory Considerations for the Approval of the First Generic Glucagon

Glucagon for Injection (NDA 020928) is a polypeptide hormone identical to human glucagon approved 20 years ago for severe hypoglycemia in patients with diabetes mellitus. On Dec 28, 2020, the U.S. FDA approved the first generic version of glucagon for injection USP, 1 mg/vial packaged in an emergency kit. The generic and the reference listed drug (RLD) version, i.e., the innovator version, of glucagon were each produced through different manufacturing processes. The RLD version of glucagon is produced via recombinant DNA in yeast while the generic version of glucagon is produced by peptide synthesis. The FDA published its current thinking on how to ensure sameness between the generic and innovator peptide products prepared with different manufacturing processes in a Draft Guidance for Industry: Submission of Abbreviated New Drug Applications for Certain Highly Purified Synthetic Peptide Drug Products, which applies to five peptide drug products, including glucagon. In this presentation, we aim to provide an overview of the regulatory recommendations for submitting generic glucagon drug products for approval, as outlined in the aforementioned draft guidance. Although glucagon may be produced using different manufacturing processes, the sameness in glucagon can be adequately demonstrated using analytical methods, which involve demonstrating physicochemical properties, as well as primary and secondary structures, oligomers and aggregation states. Biological assays may also be used as part of the demonstration of active pharmaceutical ingredient sameness. Synthetic glucagon may have different impurity profiles when compared to the RLD recombinant product. As part of the ANDA review, impurities in the synthetic drugs are analyzed and controlled, in addition, the potential immunogenicity of new impurities, which are not in the RLD products, are assessed and compared using non-clinical assays. In this work, we will discuss non-clinical assays for assessing the immunogenicity risk of these impurities, for both adaptive and innate immune responses. In conclusion, the sameness of an approved generic synthetic glucagon to an RLD can be adequately established through various analytical methods and biological assays.

Regulating Generic Ophthalmologic Drug Bioequivalence-Envisioning Accessibility for Patients

New, brand-name, ophthalmology drug products are developed, investigated, and submitted for marketing approval through premarket interactions with the Food and Drug Administration (FDA). These drug applications for novel drugs are reviewed by FDA for safety and effectiveness before being allowed on the market. Many brand-name drugs are allowed a period of marketing exclusivity and/or have patent protections that can delay generic competition. When these exclusivity periods or patents expire or are challenged (in the case of patents), generic competitors may then market equivalent products, as allowed by U.S. law (eg, Drug Price Competition and Patent Term Restoration Act, often referred to as "the Hatch-Waxman Act"). To be approved as a therapeutic equivalent, a generic product must demonstrate that it is both pharmaceutically equivalent and bioequivalent to the brand-name drug product, which can involve innovative analytical methods and study designs. To facilitate generic drug assessment and approval, the FDA has negotiated the Generic Drug User Fee Amendments (GDUFA) program that funds a rigorous generic drug development program that includes pre-Abbreviated New Drug Application (pre-ANDA) correspondence and meetings, targeted bioequivalence research, and publication of product-specific guidances (PSGs) to support generic drug research and development for manufacturers interested in developing generic drugs for the U.S. market. FDA's regulatory practices include the monitoring of quality and postapproval adverse events of all marketed products, including those for use in and around the eyes.

From Pharmacology Research, to Pharmacology Regulation, and Back-as Inspired by the Teachings of Dr. Gavril Pasternak

Dr. Gavril Pasternak, M.D., Ph.D. was an inspiration to many of his students, including myself. It was with great sadness that I learned about the passing of Dr. Gavril Pasternak in February 2019 after his brief battle with pancreatic cancer. I worked with Dr. Pasternak while I was an undergraduate chemistry student and as one of his technicians, collaborating with Dr. Charles Inturrisi and Dr. Eliot F. Hahn on opiate agonists and antagonists for opioid receptor subtypes. Dr. Pasternak inspired me and set me on the road to a career in pharmacology and encouraged me to pursue the fruitful paradigm of moving therapeutics from bench to bedside.

The relationship between the number of available therapeutic options and government payer (medicare part D) spending on topical drug products

The cost of prescription drugs has increased at rates far exceeding general inflation in recent history, with topical drugs increasing at a disproportionate rate compared to other routes of administration. We assessed the relationship between net changes in the number of therapeutic options, defined as any approved drug or therapeutic equivalent on the market, and prescription topical drug spending. Drugs were divided based on the category of use through pairing of Medicare Part D Prescriber Public Use and Food and Drug Administration (FDA) approved drug products databases. Across drug classes, we modeled the log of the ratio of total spending per unit in 2015 to total spending per unit in 2011 as a linear function of net number of topical therapeutic options over this time period. Primary outcomes include total Medicaid Part D spending on topical drugs and net change in the number of available therapeutic options within each category of use. Total spending on topical drugs increased by 61%, while the number of units dispensed increased by only 18% from 2011-2015. The greatest total spending increases were in categories with few new therapeutic options, such as topical corticosteroid and antifungal medications. Each net additional therapeutic option during 2011-2015 was associated with an reduction in how much relative spending per unit increased (95% CI 2.5%-14.4%, p = 0.013). Stimulating greater competition through increasing the net number of therapeutic options within each major topical category of use may place downward pressure on topical prescription drug spending under medicare Part D.

Mucosal morbidity in patients with epidermolysis bullosa acquisita

BACKGROUND

Epidermolysis bullosa acquisita is an acquired inflammatory and/or dermolytic subepidermal blistering disease characterized by IgG autoantibodies to type VII collagen. Four patients with documented epidermolysis bullosa acquisita were evaluated by a multidisciplinary team of care providers (4 dermatologists, an ophthalmologist, a radiologist, a voice and speech specialist, and an otolaryngologist) for 1 to 5 years to characterize mucosal involvement and its complications and response to treatment. Patients were evaluated clinically and by slitlamp examinations, endoscopies, computed tomographic scans, and videofluorographic swallowing studies. Spiral computed tomographic scans for virtual endoscopy were used for the nontraumatic evaluation of airways in 2 patients with respiratory tract compromise.

OBSERVATIONS

Involvement of 5 or more mucosal sites--mouth, nose, conjunctiva, pharynx, and larynx--was documented in all patients. Complications included ankyloglossia, periodontal disease, scarring and crusting of nasal mucosa, symblepharon formation, obstruction of nasolacrimal ducts, deformation of the epiglottis, impaired phonation, dysphagia, esophageal strictures, and supraglottic stenosis requiring emergency tracheostomy.

CONCLUSIONS

Epidermolysis bullosa acquisita may extensively (or predominantly) affect mucosal epithelia in a manner resembling cicatricial pemphigoid. Mucosal disease in these patients is often subclinical, can lead to serious complications, and is best managed using a multidisciplinary approach.

Grouped papules in Hurler-Scheie syndrome

In a patient with Hurler-Scheie syndrome, a type of mucopolysaccharidosis (I H/S), an initial presentation was grouped papules on the extensor surfaces on the upper portions of the arms and legs. Other physical findings included progressive flexion contractures and mild developmental delay. The patient had deficient alpha-L-induronidase activity, and electron microscopy showed large cytoplasmic vacuoles and lysosomes, consistent with Hurler-Scheie syndrome. Findings of grouped papules have not been previously reported in patients with this syndrome.

Human androgen receptor binding to the androgen response element of prostate specific antigen

This study examined the in vitro interaction of the human androgen receptor with a putative androgen response element (ARE) in the promoter region of the prostate specific antigen (PSA) gene. To characterize the androgen receptor's interactions with its DNA response elements we expressed the full length human androgen receptor protein in a baculovirus expression system. The receptor was shown to be 110 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and was purified using ion-exchange column chromatography. Binding of the synthetic androgen R1881 to the unpurified recombinant receptor exhibited a kd of 7.6 nM by Scatchard analysis. In DNA gel electromobility shift assays the promoter region from PSA (a 313-bp fragment) was bound by the unpurified recombinant androgen receptor in a sequence-specific manner. An ARE-containing sequence from the promoter region of the PSA gene was synthesized as a 30-bp oligonucleotide and was shown to bind specifically to the human androgen receptor in gel electromobility shift assays by DNA competition and by antibody supershifts of the receptor-ARE complex. The specific binding of the insect cell expressed androgen receptor to its ARE was shown to occur even in the absence of androgen. Androgen receptors purified by ion-exchange chromatography were unable to bind to ARE, suggesting the presence of other factors required for DNA binding.

Irreversible opiate agonists and antagonists: V. Hydrazone and acylhydrazone derivatives of naltrexone

We have synthesized a series of hydrazones and acylhydrazones of naltrexone. These substitutions had modest effects on competition of mu binding but many greatly enhanced the relative potency of the compounds for delta receptors. Increased delta affinity was most prominent with the acylhydrazones. Many of the derivatives elicited a wash-resistant inhibition of binding which was restricted to mu, not delta, binding sites. This wash-resistant inhibition of binding did not correlate with affinity, as determined by IC50 values, implying that the inhibition could not be explained simply by slow rate of dissociation due to increased affinity.

Upregulation of opioid receptor subtypes correlates with potency changes of morphine and DADLE

Chronic treatment with opioid antagonists increases the potency of opioid agonists and produces an increase in brain opioid binding sites. In the present study, 8 day treatment with naltrexone blocked morphine and DADLE analgesia for the entire treatment period and increased mu 1, mu 2 and delta opioid receptor binding sites in mouse brain. mu 1 and mu 2 binding were increased by 81 and 67%, respectively, while delta binding was increased by 31%. Consistent with these binding changes, the potency of ICV morphine to produce analgesia was increased by over 3-fold, while the potency of ICV DADLE was increased by only 1.7. These findings indicate that relative increases in opioid receptor subtypes agree with pharmacodynamic studies on potency changes of opioid agonists.