Evaluation of Switching Patterns in FDA's Sentinel System: A New Tool to Assess Generic Drugs

Switching patterns of immediate-release forms of generic mixed amphetamine salts products among privately and publicly insured individuals aged 15-64 years in the United States, 2013-2019

PURPOSE

Immediate-release forms of generic mixed amphetamine salts (MAS) have been the subject of passive surveillance reports signaling lack of effectiveness. We examined switching patterns that might suggest whether long-term users of specific MAS are more likely to switch away or switch back after use of the MAS of interest in the FDA's Sentinel Distributed Database.

METHODS

We required at least 60-day continuous supply of selected MAS grouped by Abbreviated New Drug Application (ANDA) to describe patterns of switching away from and to generics approved under the ANDAs of interest among individuals ages 15-64 years with attention deficit hyperactivity disorder or narcolepsy during 2013-2019.

RESULTS

We observed the greatest number of treatment episodes for ANDA 040422 (n = 525 771), followed by ANDA 202424 (n = 181 693), ANDA 040439 (n = 62 363), ANDA 040440 (n = 21 143), and ANDA 040480 (n = 8792). Of those with switches away from their original ANDA, episodes initiated on generic products under ANDA 040422 (48.6%) and ANDA 202424 (43.0%) were most likely to switch back, while those initiated on generic product under ANDA 040480 were least likely (24.1%). Of those episodes with switches to a generic under an ANDA of interest, about one-third (range 27.1% to 37.0%) switched back to the same product. These switches back had a median time to switch of about 30 days.

CONCLUSIONS

These descriptive analyses, although subject to limitations, did not suggest increased switching away or switching back after use of the generics of interest. Continued post-marketing surveillance is warranted.

Dosage unit uniformity and dissolution testing of extended-release pharmaceutical products marketed in the U.S

An international sampling study yielded 69 samples of extended-release prescription pharmaceuticals for legal sale in the U.S. Samples included 29 lots of innovator and 40 lots of generic solid oral extended-release drugs manufactured at 16 different facilities and containing 6 different active ingredients. Dosage unit uniformity and dissolution were tested for each lot. All samples met the relevant testing criteria for dosage unit uniformity and dissolution. There were no indications that manufacturer or region impacted a product's acceptability for use by patients. The variability of attributes was used to calculate a process performance index (Ppk) for each facility. Higher Ppk values suggest less variability relative to specification limits. Only two manufacturers fell below a 4-sigma manufacturing benchmark Ppk of 1.33 for dosage unit uniformity: a European manufacturer of a brand drug and an Asian manufacturer of a generic drug. Conversely, all but four manufacturers fell below a 4-sigma benchmark for the minimum Ppk across their product's dissolution timepoints: generic drug manufacturers in India (two), the U.S., and Canada. Compared to the immediate-release products of a previous study, Ppks were generally lower for extended-release products. A retrospective analysis found that manufacturers performing below median Ppks submitted more Field Alert Reports after the end of the sampling period.

Patient Characteristics and Utilization Patterns of Short-Acting Recombinant Granulocyte Colony-Stimulating Factor (G-CSF) Biosimilars Compared to Their Reference Product

BACKGROUND

Data on short-acting recombinant granulocyte colony-stimulating factor (G-CSF) biosimilar utilization from claims data in the USA are limited.

OBJECTIVE

To evaluate patient baseline characteristics and utilization patterns for short-acting G-CSF products with particular focus on the assessment of filgrastim biosimilar usage relative to the originator product.

PATIENTS AND METHODS

We examined filgrastim, filgrastim-sndz, and tbo-filgrastim use among adult patients between January 2012 and March 2019 across the five health-plan research partners in the BBCIC Distributed Research Network. The publicly available Sentinel System analytic toolkit was used to perform the distributed analyses.

RESULTS

We evaluated over 38 million eligible health-plan members representing more than 88 million person-years of data. We identified 45,204 incident treatment episodes, including 33,118 episodes with filgrastim, 6525 episodes with filgrastim-sndz, and 5,561 episodes with tbo-filgrastim. We observed that the demographic and clinical characteristics of users were comparable across products. While total use of all filgrastim products remained consistent, the proportion of incident episodes of the originator filgrastim steadily decreased since 2014, with filgrastim-sndz and tbo-filgrastim making up the difference. Utilization for the G-CSF biosimilar, filgrastim-sndz, increased from 40 (1%) of 6823 total filgrastim product episodes in 2015, to 2486 (44%) of a total 5668 episodes of filgrastim products in 2018 (partial data for 2018).

CONCLUSION

New episodes of short-acting biosimilar filgrastim products have increased over time while the overall number of new users remained flat. Although barriers to biosimilar use in oncology have been noted, uptake has begun and continues to grow.

Evaluation of Switch-to-Brand Rates as a Potential Signal for Therapeutic Equivalency of Generic Antidepressants: A Real-World Retrospective Cohort Study

Negative clinical outcomes after switching from brand to generic antidepressants have raised concerns regarding therapeutic equivalency. This research aims to estimate the prevalence of switching and to identify predictors for generic to brand switching for various antidepressants. This retrospective cohort study utilized data from a 10% random sample of enrollees in the IQVIA PharMetrics Plus claims database from 2007-2015. The base cohort consisted of commercially insured patients who were prescribed escitalopram, duloxetine, or venlafaxine extended release (ER) anytime from the year prior to the generic launch through December 2014. The primary outcome was defined as a switch from generic to a brand within 14 days of sustained generic use in a 1-year follow-up period. Adjusted logistic regression and generalized estimating equations for repeated measures estimated the drug specific and overall odds of switch-to-brand among brand initiators relative to generic initiators, respectively. A total of 102,831 unique patients across 3 drug products contributed to the final analytic sample. The overall prevalence of switch from generic to brand was 0.74%. Across all three antidepressants, brands initiators were more likely to experience a switch-to-brand: escitalopram (odds ratio (OR): 14.41, 95% confidence interval (CI): 11.14-18.64), duloxetine (OR: 8.08, 95% CI: 4.85-13.41) and venlafaxine ER (OR: 16.46, 95% CI: 11.56-23.46). The pooled odds of a switch-to-brand in brand vs. generic initiators was 13.77 (95% CI: 11.35-16.71). This study suggests a low overall switch-to-brand prevalence and may support therapeutic equivalence between brand and generic antidepressants. Initiating with a brand product was the strongest predictor for switching back to brand and suggests that patient experience may play a role in drug utilization.

Understanding authorized generics-A review of the published clinical data

WHAT IS KNOWN AND OBJECTIVES

Despite the large body of evidence demonstrating equivalent efficacy and safety for branded drugs and their generic counterparts, some patients and providers have the perception that generics may be less safe and effective than branded agents. Authorized generics (AGs) are a category of generic drugs defined by the United States Food and Drug Administration (FDA) as being the same as the brand-name drug without the brand's name on the label and which may have minor differences, such as tablet or capsule markings for identification. Studies in which AGs are considered along with other generics may increase our understanding of factors that may influence perceptions about generics and shed light on areas where education may be impactful. The objectives of this paper are to provide information about AGs, review studies in which they have been evaluated and explore the role that AGs may fill in the individualized treatment of patients.

METHODS

A literature review was conducted on 30 September 2019 with follow-up search on 4 March 2020. The search was focussed on published papers and meeting abstracts that provided information on AGs with respect to medical and health outcomes of therapy as well as switching in individuals receiving branded, AG, or other generic agents. Information about patients' perceptions of generic medications and adherence to therapy was also included. Additional information, including relevant government sources, such as the FDA website and the Federal Trade Commission Report, was included as appropriate.

RESULTS

The literature specific to AGs is limited, but available data clearly highlight the importance of patient perception of generics as well as medication appearance as factors that may affect adherence and potentially more frequent switchbacks to branded agents from generics or AGs.

WHAT IS NEW AND CONCLUSION

To our knowledge, this is the first narrative review to provide a summary of the published evidence about AGs with respect to clinical and health outcomes and switching. There is a need for more research and education regarding the use of AGs in clinical practice if they are to become more recognized as a potential treatment choice for patients. Generic medications play an important role in the healthcare system, and AGs may be able to provide an option to meet the specific needs of individual patients.

Utilization patterns and characteristics of users of biologic anti-inflammatory agents in a large, US commercially insured population

We report utilization patterns and characteristics of patients treated with biologic anti-inflammatory agents in a large commercially insured patient population in the United States. We identified adult (age ≥18 years) patients receiving biologic anti-inflammatory agents between 1 January 2012 and 31 March 2019 across the five Research Partners in the Biologic and Biosimilars Collective Intelligence Consortium's Distributed Research Network. We examined the number of incident use episodes for each biologic, as well as patient demographic and clinical characteristics. Curated data and analytic tools from the Food and Drug Administration's Sentinel System were used to perform the analyses. We identified 90,360 incident episodes of tumor necrosis factor-alpha inhibitors (TNFi) and 70,506 incident episodes of non-TNFi medications. Adalimumab was the most common TNFi drug (47% of all TNFi episodes) and showed a steady increase in utilization during the study period compared to other TNFi agents. Rituximab was the most commonly initiated non-TNFi medication (44% of non-TNFi episodes). Other non-TNFi agents, namely, ustekinumab, vedolizumab, and secukinumab, demonstrated notable increases in utilization over time. Biosimilar use was limited; we observed 653 incident episodes for infliximab-dyyb and 39 incident episodes for infliximab-abda. As more biologics enter the market, greater variation in the use of biologics with similar indications and between biologic originators and biosimilars is anticipated. Because information on efficacy and safety at the time of drug approval is limited, post-marketing surveillance and research is needed to monitor medication safety and evaluate effectiveness between biologic drugs using real-world data.

A Call to Action to Track Generic Drug Quality Using Real-World Data and the FDA's Sentinel Initiative

DISCLOSURES

The author reports funding from the U.S. Food and Drug Administration to study real-world data approaches to detect generic drug quality issues. There are no further conflicts or disclosures.

Drug switching in the Netherlands: a cohort study of 20 active substances

BACKGROUND

For a patient, drug switches are not desirable (either between a brand-name drug and a generic drug, or between two generic drugs of the same active substance). Research into the causes of drug switches, and related adverse drug reactions, is hampered by the absence of quantitative data on drug switches.

METHODS

We describe the frequency of drug switches in the Netherlands for a selection of active substances. A retrospective cohort study was conducted using the Drug Information System of the National Health Care Institute in the Netherlands. We studied the Dutch patient population from mid-2009 to 2016. The selection of active substances (n = 20) was made based on a report by Lareb, the Netherlands Pharmacovigilance Centre, on adverse drug reactions related to drug switching, and we used qualitative and quantitative descriptive analyses. A drug switch is defined as the replacement of a patient's prescribed drug with a similar drug from a different manufacturer.

RESULTS

We identified 23.8 million drug switches on a total of 206 million (11.6%) similar drug dispenses. The frequency of drug switches demonstrated a yearly peak in the period from January to March. In some months, for atorvastatin, losartan, pantoprazole, and irbesartan, more than 60% of similar drug dispenses were drug switches. Most drug switches (80.3%) were between two generic drugs, and 0.12% of these involved a drug from a European parallel import. The proportion of drug switches between two brand-name drugs decreased from 14.5 to 5.53% during our study period, and of these, 86.5% involved a drug from a European parallel import.

CONCLUSIONS

Drug switching is common in the Netherlands, and most of the drug switches we studied are between generic drugs. The observed annual peak of drug switches is most likely explained by a specific Dutch reimbursement policy. Not only are the data valuable as is, but they also serve as a first step towards elucidating the reasons for the occurrence of these drug switches. In addition, these data can be used to put into perspective the adverse drug reactions associated with drug switching.

Real-World Data Approaches for Early Detection of Potential Safety and Effectiveness Signals for Generic Substitution: A Metoprolol Extended-Release Case Study

Real-world spontaneous adverse event reports and administrative health care data were utilized as one part of a multipronged approach to verify surveillance signals related to generic drug formulations. This study used metoprolol succinate extended release as a historic case example from which to develop an analytic framework. The US Food and Drug Administration Adverse Event Reporting System was utilized for disproportionality analyses and to identify outcomes of interest. Claims data were analyzed for generic uptake, proportion of prescriptions with "dispense as written" orders, time to discontinuation or switching, and relative rates of clinical events. Adverse Event Reporting System data showed that the Medical Dictionary for Regulatory Activities terms for product quality were higher for generic metoprolol cases and that a number of clinical events were increased that could be side effects of high or low variability in drug levels. Compared to amlodipine-benazepril, which also had a first-approved generic at the same time, market share data showed that metoprolol succinate had lower utilization and more prescriptions written as dispense as written. Switching and discontinuation were generally higher for metoprolol users compared to amlodipine-benazepril users. Finally, clinical event rates were generally higher for generic versus brand metoprolol but lower for the same comparison for amlodipine-benazepril users. In the claims-based analyses, the 90-day period immediately after generic entry provided stronger signal capture than using the entire study period. This analytic framework can be implemented to actively monitor new generic formulations for potential bioequivalence failures. Signals from these analyses require confirmation (eg, via pharmacometric analyses) to be informative for regulatory action.

Lower Proportion of Spontaneous Adverse Event Reports for Generic Drugs by Comparison With Original Branded Drugs at the Postmarket Stage in Japan

We investigated impacts of increased generic drug use on spontaneous adverse event reports (SAERs), because SAERs have been a major source of data for drug safety assessment at the postmarket stage. Reporting proportion of SAERs for the generic drugs was consistently and significantly lower than that for the original branded drugs. The reporting proportion targeting for 55 active product ingredients, which had the longest follow-up period after generic drug marketed, gradually decreased for the original branded drugs and increased for the generic drugs. However, these transitions did not parallel the changes in market share over the same period. These results suggest that the reporting proportion of SAERs for generic drugs may not keep pace with growth in market share. When generic drugs account for the majority of market share, utilization of multiple sources of information and data, in addition to SAERs, may be a key to assuring drug safety at the postmarket stage.