Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system in which immune cells attack the myelin sheath surrounding the nerve fibers causing demyelination and axonal degeneration.1 The symptoms and signs of MS can vary depending on the affected neurons. Some of the most common clinical features of MS are optic neuritis, Lhermitte’s sign (an electrical sensation that extends from the neck down to the spine), depression, sexual dysfunction, gait changes, and neurogenic bladder.1
The prevalence of MS in the United States has been increasing over time from 727,344 cases in 2010 to nearly 913,925 in 2017, with female patients having a higher incidence rate than male patients.2 Although MS is classified as a rare disease,3 it carries a substantial economic burden, with an estimated annual direct healthcare cost of $18.94 billion in the United States.4 The high financial burden of MS can be attributed to multiple factors. First, MS is a progressive disabling disorder that predominantly affects younger adults at their most productive years, between age 20 and 50 years.5
As a result, the disease is associated with loss of work productivity, absenteeism costs, and a high burden on caregivers.6 In a study that focused on patients with MS and low physical disability, the employment rate was only 47.2% and the mean retirement age was 43.6 years.6 A systematic review showed that productivity loss and informal care in patients with MS account for 17% to 67% of total costs in patients with high disease severity.7
Furthermore, different conditions and diseases arise as sequelae of MS, requiring more expenses for the treatment of these conditions (ie, depression, malaise, fatigue, and convulsions).8 However, the most significant cost driver in the management of MS is spending on prescription drugs. It is estimated that prescription drugs represent 29% to 82% of all healthcare costs for patients with MS who have low disease severity.8 Moreover, in a retrospective study of patients with MS, increased spending on prescription medications totaled 76% of the incremental total MS-related healthcare expenses from 2010 to 2015.4
To date, there is no cure for MS; therefore, treatment is based on the use of disease-modifying therapies to stop the progression of disease and to prevent future relapses.9 Currently, there are 18 disease-modifying therapies approved by the US Food and Drug Administration (FDA) for the treatment of MS (Table 1).9-11 Only 1 medication, daclizumab (Zinbryta), has been withdrawn from the market (in 2018) because of safety issues.10
Most disease-modifying therapies are classified as specialty drugs because they meet the criteria set by the Pharmaceutical Care Management Association.12 Some of the characteristics of these drugs are that they have a high monthly cost, require special storage and transportation conditions, are usually indicated for patients with complex conditions, need considerable patient education, and are available through specialty pharmacies rather than retail pharmacies.12 In a 2018 report, spending on specialty drugs constituted 44.7% of the total drug expenditure, and this spending is projected to increase in future years.13 Similarly, the cost of disease-modifying therapies has rapidly increased since 2008.13
The annual cost of disease-modifying therapies per patient with MS in a commercial population increased by an annual rate of 13% from 2011 to 2015.14 A research reported by Hartung and colleagues revealed that from 1993 to 2013, the annual inflation rate of disease-modifying therapy costs in the United States skyrocketed 5 to 7 times more than the inflation rate of other prescription drugs.15 Furthermore, newer disease-modifying therapies were launched with a 25% to 60% greater cost than the already-available disease-modifying therapies, with an annual cost averaging of approximately $60,000 in 2015.15
Studies have concluded that more than 90% of patients with MS had health insurance coverage.16,17 Nonetheless, patients’ accessibility to drugs may be compromised because of higher out-of-pocket payments required by the insurance industry to combat the soaring cost of disease-modifying therapies.18 In 2018, disease-modifying therapies for MS were ranked among the top 15 therapy classes based on the total per-member per-year drug spending for commercial health plans, for Medicare, and for Medicaid.13
Several studies investigated the utilization and cost patterns of disease-modifying therapies in commercially insured and in Medicare populations.14,19-21 To our knowledge, this is the first study to calculate these trends in the Medicaid-insured population. Medicaid is targeted mainly toward patients with low incomes and is sponsored by federal and state governments. Medicaid eligibility requirements and coverage may differ from one state to another, making it difficult to obtain accurate information about Medicaid-covered patients with MS.22,23
The objective of this study was to analyze the trends in drug expenditure, utilization, and cost of specialty drugs for the treatment of patients with MS who were enrolled in Medicaid between 2008 and 2018. By studying these patterns, we aim to elucidate the MS drug market and to guide policymakers to adapt the best strategies to allocate resources for this patient population.
In this retrospective study, we analyzed the National Pharmacy Summary Files for the Medicaid State Drug Utilization Data from the first quarter of 2008 to the fourth quarter of 2018.24 The Medicaid State Drug Utilization Data are provided by the Centers for Medicare & Medicaid Services (CMS) and are freely available to the public. The files were combined by pooling the state files, which contain information about outpatient drug utilization for drugs that are paid for by state Medicaid agencies.
The database’s records include the state, drug name, National Drug Code (NDC), number of prescriptions, and the amount of dollars reimbursed.24 We searched each of the drugs listed in Table 1 using NDC codes. All drugs for the treatment of MS were included in our study, except for cladribine (Mavenclad), siponimod (Mayzent), and diroximel fumarate (Vumerity), because they were approved for the treatment of MS in 2019, after our study period.
The annual number of prescriptions and the annual reimbursement amount were calculated for each drug separately, and then the annual total was aggregated. In addition, we estimated the annual cost per prescription for each of the drugs, by dividing the reimbursement amount by the prescription counts. This cost may not represent the real per-prescription amount exactly, because information about state rebates from pharmaceutical companies is not publicly available and therefore was not included in this analysis.
Moreover, the market share in the Medicaid program for the various disease-modifying therapy classes was computed as a percentage of the total prescription count and as a percentage of the total reimbursement amount. The disease-modifying therapy classes were categorized according to the drugs’ route of administration (ie, injectable, oral, or infusion; Table 2).9 Descriptive statistics were used to analyze the trends in the prescription counts, the total reimbursement amount, and the cost per prescription over the 10-year study period.
Total Annual Utilization and Reimbursement of All Study Drugs
The total MS disease-modifying therapies prescription counts, as well as the total spending over time, are shown in Table 3. In general, the number of prescriptions increased by 128.7% from 85,209 in 2008 to 194,877 in 2018. When comparing the annual change by year, the greatest percent increase was observed in 2011 when the number of prescriptions increased by approximately 51% compared with 2010. The prescription count declined in 2017 and 2018, by 1.63% in 2017 and by 11.4% in 2018.
The total annual spending increased by almost 633% from $171,953,894 in 2008 to $1,259,861,796 in 2018. As with the total prescription utilization pattern, the greatest percent increase in spending (ie, 81.42%) was in 2011. The only year in which spending decreased was 2018, by 10.39%.
Total Annual Utilization of Each Drug
(To avoid confusion, brand names are used in the following sections for drugs that have more than 1 brand name drug). The total prescription counts for each disease-modifying therapy by year are listed in Appendix Table 1 and Figure 1.
From 2008 through 2012, glatiramer acetate (Copaxone) 20 mg was dominating the MS market, and its prescription count reached a peak of 51,147 in 2012. Intramuscular interferon beta-1a (Avonex), subcutaneous interferon beta-1a (Rebif), and subcutaneous interferon beta-1b (Betaseron) showed a similar utilization pattern to Copaxone 20 mg, but with lower prescription counts. The use of natalizumab (Tysabri) increased by 384.5% from only 2992 prescriptions in 2008 to 14,499 prescriptions in 2012. Fingolimod (Gilenya), the first oral disease-modifying therapy for MS, was introduced in 2010, and its utilization increased rapidly from a prescription count of 29 in 2010 to 9032 prescriptions in 2012.
Subsequently, the use of Copaxone 20 mg significantly declined from 46,203 prescriptions in 2013 to 8165 prescriptions in 2018, and the drug no longer dominated the MS market. From 2013 to 2018, the use of intramuscular interferon beta-1a, subcutaneous interferon beta-1a, and interferon beta-1a (Betaseron) significantly decreased as well. From 2014 to 2016, the prescription counts of Copaxone 40 mg increased and the counts for the 20 mg decreased; in 2017, these trends reversed. In 2018, the use of Copaxone 20 mg and 40 mg decreased from the previous year. By contrast, in 2017 and 2018, there were substantial increases in the prescription counts of generic glatiramer acetate 20 mg and 40 mg.
The utilization of oral MS medications increased from 2013 to 2018, except for dimethyl fumarate (Tecfidera), which had a decline in its prescription count in 2016. Nevertheless, from the year 2015, dimethyl fumarate was the drug with the highest prescription count, with a market share of 22.2% in 2018. As for infusion drugs, the utilization of natalizumab started to decrease in 2016. The use of alemtuzumab (Lemtrada) increased during its first year (2016-2017), but its use decreased in 2018. The use of ocrelizumab (Ocrevus) has been increasing since its entry into the market in 2017.
Total Annual Reimbursement of All Study Drugs
The patterns of reimbursement and spending on disease-modifying therapies are similar to those of utilization, as shown in Figure 2 and Appendix Table 2. Until 2013, Copaxone 20 mg was the medication with the highest total reimbursement amount, reaching $211,813,564. After 2013, among injectable drugs, spending on Copaxone 20 mg declined, but in 2017, spending on brand-name Copaxone 40 mg and generic glatiramer acetate 20 mg and 40 mg increased.
Since the entry of oral drugs to the market, their reimbursement amount has been increasing sharply. Dimethyl fumarate had the greatest increase in reimbursement, which saw a slight decline in 2018, when the reimbursement amount reached $297,683,988. For the infusion drugs natalizumab and alemtuzumab, spending increased until 2017, then decreased. Spending on ocrelizumab, however, increased by 854% in only 2 years (ie, 2017 and 2018).
Annual Cost per Prescription of Each Study Drug
The cost of prescriptions of most disease-modifying therapies for MS has been increasing between 2008 and 2018 at high rates (Figure 3 and Appendix Table 3). For example, the cost of Copaxone 20 mg has increased by 307% from $2030 in 2008 to a high of $8268 in 2017. However, in 2018, the cost of the generic drugs glatiramer acetate 20 mg (Glatopa); glatiramer acetate 20 mg and 40 mg; Copaxone 20 mg and 40 mg; and natalizumab declined. The exception to this trend included mitoxantrone hydrochloride (Novantrone), whose cost showed an overall decrease during our study period.
In 2008, based on the annual reimbursement data, injectables drugs were the predominant medications on the MS market (Figure 4). However, the market share percentage for injectable drugs decreased significantly, from 96% in 2008 to 37% in 2018. By comparison, the market share for infusion drugs and oral drugs has been increasing. In 2008, the share of infusion drugs was 4%, and no oral medications had launched in the market. In 2011, oral drugs had a market share of 4%. Between 2017 and 2018, the market share for injectable drugs and oral drugs flipped, and the share of oral medications reached 46% in 2018.
The annual market share for each disease-modifying therapy is shown in the Appendix Table 4.
Overall, the utilization of MS drugs increased by approximately 128.7% from 2008 to 2018. Many reasons could have accounted for this growth. First, the number of available medications for the treatment of MS increased from 6 drugs in 2008 to 16 drugs in 2018, with each drug having several doses and dosage forms approved by the FDA. Advancements in medical technology and the introduction of the Orphan Drug Act (ODA) of 1983 could have caused this increase; the ODA incentivized pharmaceutical companies to develop drugs for rare diseases.25
Second, as a result of the increases in disease prevalence and the life expectancy of patients with MS, there is more demand for drugs, which leads to an increase in the volume of drug purchases.2,26 Another contributing factor to these increases could be the growth in Medicaid beneficiaries and enrollment, which likely results from the Medicaid expansion endorsed by several states after the Affordable Care Act in 2010. Between 2013 and 2019, Medicaid enrollment increased by 14.7 million across 49 states.27 Despite this rise in the utilization of drugs for MS, prescription counts for disease-modifying therapies for MS in 2018 declined by 11.4% compared with 2017; this trend has also been observed in commercial health plans.
The market shift from treatment with dimethyl fumarate to ocrelizumab may have contributed to this trend. Dimethyl fumarate is a twice-daily oral regimen, whereas ocrelizumab is a twice-annual infusion. Shifting from dimethyl fumarate to ocrelizumab may have resulted in less prescription purchases because ocrelizumab may be more convenient to take for some patients. Moreover, ocrelizumab has a safety profile comparable to and similar or superior efficacy to other disease-modifying therapies, which may have led physicians to prefer one drug over the other.28,29
Our analysis also shows strong competition between disease-modifying therapies in the healthcare market. There is intermarket competition between the different classes. Self-injectable drugs dominated the market when they were introduced; however, in 2018, the market share was almost split between self-injectable and oral medications. As noted, intermarket competition was also evident between certain drugs of different classes, such as dimethyl fumarate and ocrelizumab. Competition also exists within each class; there was interbrand competition in oral drugs between fingolimod and teriflunomide (Aubagio). Although fingolimod was launched in 2010, 2 years before teriflunomide and had more market share than teriflunomide, by 2018 the 2 drugs had a comparable market share.
There was also competition between natalizumab and ocrelizumab. Natalizumab has a black box warning for progressive multifocal leukoencephalopathy, and physicians likely preferred prescribing ocrelizumab for its better safety profile.29,30 The influence of brand name–generic drug competition is still not very clear in the MS drug market. Despite Teva Pharmaceuticals’ efforts of evergreening with the launch of Copaxone 40 mg in 2014 (taken 3 times weekly) to extend Copaxone patency, generic equivalents for Copaxone 20 mg (taken once daily) and Copaxone 40 mg are now available.31,32
The impact of Glatopa 40 mg was not found in our study, because the drug was approved in 2018; however, in 2016, the utilization of Glatopa 20 mg increased, with a corresponding decrease in the use of Copaxone 20 mg. There was brand-name drug versus generic drug competition between glatiramer acetate 40 mg and Copaxone 20 mg and 40 mg. Before the market entry of glatiramer acetate 40 mg, the market share of Copaxone 20 mg was 6.16% and that of Copaxone 40 mg was 16.62%; in 2018, the market share decreased to 4.2% and 9.03%, respectively, in contrast to glatiramer acetate 40 mg, which reached 7.6% that year. By contrast, the utilization of glatiramer acetate 20 mg increased only slightly in market share since its entry into the market.
In general, the total Medicaid expenditures on MS drugs increased from 2008 to 2018. The reasons for the increased spending resemble the causes for the increased utilization of MS drugs and the inflated medication costs. As noted earlier, most medications for the treatment of MS are specialty drugs that have higher costs than many other medications on the market. A report from the AARP Public Policy Institute lists 101 specialty drugs frequently used by older Americans.33 A total of 12 of these specialty drugs are indicated for the treatment of MS; 7 of the MS drugs were ranked among the 30 top-selling specialty drugs. The 7 MS drugs include Copaxone 20 mg and 40 mg, dimethyl fumarate, intramuscular interferon beta-1a autoinjection and prefilled syringes, subcutaneous interferon beta-1a, and interferon beta-1b (Betaseron).33
In 2018, a decrease in overall spending was observed, which could have resulted from the decreased overall prescription purchases during that year and/or a market shift from brand-name Copaxone to less-costly generic glatiramer acetate. Market share and competition among MS drugs calculated based on the total reimbursement data yielded similar results to those calculated based on utilization data. The only difference found was that the market share for oral drugs in the reimbursement data surpassed that of injectable therapies.
In general, the cost per prescription for most of the MS drugs increased from 2008 to 2018. This upsurge in most of the costs of the MS drugs has also been observed in previous studies.14,15,20,34 Theoretically, when there is a competing drug market, the entry of new brand-name drugs reduces, or at least sustains, the cost of existing older drugs; however, this was not the case in the MS drug market. Instead, our data show that when new brand-name drugs were launched, the cost of already existing disease-modifying therapies was elevated to compete with the new drugs on the same cost level and maximize profit. This finding was supported by Hartung and colleagues, who observed that the phenomenon was only happening in the United States.15
Another factor that contributes to the constant rise in MS drug costs is the lack of competition between brand-name biologic drugs (reference drugs) and their biosimilars. Most current therapies for MS are biologic drugs; therefore, pharmaceutical companies have been slow in developing biosimilars, because these drugs require large investments, in accordance with the Biologics Price Competition and Innovation Act of 2009.35
Only in 2017 and 2018 did generic Glatopa and glatiramer acetate receive FDA approvals. In general, the advantage of having generic drugs and biosimilars on the market is that they serve as the antidote to skyrocketing prescription costs, as suggested in previous studies conducted in various therapeutic areas.36,37
Paradoxically, when they entered the market, the cost per prescription of Glatopa 20 mg was higher than those of Copaxone 20 mg and 40 mg. Then, the cost of Glatopa 20 mg started declining, which was met by a rise in the cost of the 2 doses of Copaxone to leverage revenues. In 2017, generic glatiramer acetate (20 mg and 40 mg) was introduced, at which time glatiramer acetate 20 mg and Glatopa 20 mg were approximately half the cost of Copaxone 20 mg. In 2018, the cost of both doses of Copaxone, Glatopa 20 mg, and both doses of glatiramer acetate decreased. Furthermore, Glatopa 40 mg was introduced at a cost between Copaxone 40 mg and glatiramer acetate 40 mg. Although it can be argued that the effect of brand-name and generic drug competition was seen in 2018, the impact of this competition on the broader MS drug market remains to be more clearly defined in the future.
This study has several limitations. The current findings are limited by the available data on the CMS National Medicaid Pharmacy File. Patient-specific information was not available in the national Medicaid database, so we could not perform multivariate analysis to study the impact of various patient characteristics on spending and utilization of MS drugs. Also, we could not obtain information about the indication of each prescribed medication, and this could have potentially biased our results.
The effect of brand-name versus generic drug competition is constrained by the limited measurement available to calculate competition during the study period. Moreover, prescribing patterns may be influenced by the prescriber’s and the patient’s ability to access a medication. No data about the appropriate use of the drugs or the patient’s adherence are reported.
Finally, this study only focused on the Medicaid population, which encompasses the underserved, low-income population. Consequently, our findings may not be generalizable to other populations, such as patients with Medicare or with commercial insurance.
Our findings indicate the presence of intermarket and interbrand competition among MS specialty drugs between 2008 and 2018. The increased utilization and spending trends for specialty MS medications are significant and sizable for Medicaid beneficiaries. This research provides informative data about the increasing cost trends of MS medications for Medicaid-related policymakers. These findings highlight the need to have a cost-containment strategy to control the economic burden of MS specialty drugs on Medicaid state budgets. This information can allow policymakers to investigate new ways to control spending in this high-cost therapeutic drug class. Our study also allows clinical providers to consider the affordability of MS drugs for non-Medicaid patients who are enrolled in commercial or private insurance plans with less generous benefit designs.
The opinions and conclusions expressed in this article are solely those of the authors. The authors did not receive financial support or material gain that may involve the subject matter of the article.
Author Disclosure Statement
Ms Elsisi, Dr Hincapie, and Dr Guo have no conflicts of interest to report. Dr Guo was a principal or co-investigator on research studies sponsored by Novartis, AstraZeneca, Bristol-Myers Squibb, Janssen Ortho-McNeil, Roche-Genentech, and Eli Lilly, none of which involved specialty drugs for MS.
- Calabresi PA. Diagnosis and management of multiple sclerosis. Am Fam Physician. 2004;70:1935-1944.
- Wallin MT, Culpepper WJ, Campbell JD, et al; for the US Multiple Sclerosis Prevalence Workgroup. The prevalence of MS in the United States: a population-based estimate using health claims data. Neurology. 2019;92:e1029-e1040. Erratum in: Neurology. 2019;93:688.
- National Organization for Rare Disorders. Rare Disease Database. Search results for: M. https://rarediseases.org/?s=M&post_type=rare-diseases. Accessed August 8, 2019.
- Earla JR, Thornton JD, Aparasu RR. Health care resource utilization and economic burden in multiple sclerosis patients. Res Social Adm Pharm. 2018;14:e19.
- National Multiple Sclerosis Society. Who gets MS? (Epidemiology). www.nationalmssociety.org/What-is-MS/Who-Gets-MS. Accessed August 4, 2019.
- García-Domínguez JM, Maurino J, Martínez-Ginés ML, et al; for the W-IMPACT clinical investigators. Economic burden of multiple sclerosis in a population with low physical disability. BMC Public Health. 2019;19:609. doi.org/10.1186/s12889-019-6907-x. Erratum in: BMC Public Health. 2019;19:909. doi.org/10.1186/s12889-019-7275-2.
- Ernstsson O, Gyllensten H, Alexanderson K, et al. Cost of illness of multiple sclerosis - a systematic review. PLoS One. 2016;11:e0159129. doi.org/10.1371/journal.pone.0159129.
- Carroll CA, Fairman KA, Lage MJ. Updated cost-of-care estimates for commercially insured patients with multiple sclerosis: retrospective observational analysis of medical and pharmacy claims data. BMC Health Serv Res. 2014;14:286. doi.org/10.1186/1472-6963-14-286.
- National Multiple Sclerosis Society. Treating MS: medications. www.nationalmssociety.org/Treating-MS/Medications. Accessed July 6, 2019.
- National Multiple Sclerosis Society. Zinbryta (daclizumab), a therapy for relapsing MS, is withdrawn from market - UPDATED with FDA info. March 15, 2018. www.nationalmssociety.org/About-the-Society/News/Zinbryta,-a-Therapy-for-Relapsing-MS,-is-Withdrawn. Accessed August 8, 2019.
- US Food and Drug Administration. Drugs@FDA: FDA-approved drugs. www.accessdata.fda.gov/scripts/cder/daf/index.cfm. Accessed July 6, 2019.
- Pharmaceutical Care Management Association. What is a specialty drug? www.pcmanet.org/pcma-cardstack/what-is-a-specialty-drug/. Accessed April 17, 2019.
- Express Scripts. 2018 Drug Trend Report. 2019. https://corporate-site-labs-prod.s3.us-east-2.amazonaws.com/2020-02/Express%20Scripts%202018%20Drug%20Trend%20Report.pdf. Accessed August 9, 2019.
- Kim Y, Krause TM, Blum P, Freeman L. Disease modifying therapies continue to drive up health care cost among individuals with multiple sclerosis. Mult Scler Relat Disord. 2019;30:69-75.
- Hartung DM, Bourdette DN, Ahmed SM, Whitham RH. The cost of multiple sclerosis drugs in the US and the pharmaceutical industry: too big to fail? Neurology. 2015;84:2185-2192. Erratum in: Neurology. 2015;85:1728.
- 16. Iezzoni LI, Ngo L. Health, disability, and life insurance experiences of working-age persons with multiple sclerosis. Mult Scler. 2007;13:534-546.
- 17. Minden SL, Frankel D, Hadden L, Hoaglin DC. Access to health care for people with multiple sclerosis. Mult Scler. 2007;13:547-558.
- 18. Callaghan BC, Reynolds E, Banerjee M, et al. Out-of-pocket costs are on the rise for commonly prescribed neurologic medications. Neurology. 2019;92:e2604-e2613. Erratum in: Neurology. 2019;93:688.
- Sanchirico M, Caldwell-Tarr A, Mudumby P, et al. Treatment patterns, healthcare resource utilization, and costs among Medicare patients with multiple sclerosis in relation to disease-modifying therapy and corticosteroid treatment. Neurol Ther. 2019;8:121-133.
- Hartung DM. Economics and cost-effectiveness of multiple sclerosis therapies in the USA. Neurotherapeutics. 2017;14:1018-1026.
- Desai RJ, Mahesri M, Gagne JJ, et al. Utilization patterns of oral disease-modifying drugs in commercially insured patients with multiple sclerosis. J Manag Care Spec Pharm. 2019;25:113-121.
- Owens GM. Economic burden of multiple sclerosis and the role of managed care organizations in multiple sclerosis management. Am J Manag Care. 2016;22(6 suppl):S151-S158.
- National Multiple Sclerosis Society. Medicaid and other public health insurance programs. www.nationalmssociety.org/Living-Well-With-MS/Work-and-Home/Insurance-and-Financial-Information/Health-Insurance/Medicaid-and-Other-Public-Health-Insurance-Program. Accessed July 6, 2019.
- National Bureau of Economic Research. Medicaid State Drug Utilization Data. Updated February 19, 2018. www.nber.org/data/state-drug-utilization.html. Accessed March 10, 2019.
- National Institutes of Health. List of FDA orphan drugs: M. Genetic and Rare Diseases Information Center. https://rarediseases.info.nih.gov/diseases/fda-orphan-drugs/M. Accessed April 17, 2019.
- Scalfari A, Knappertz V, Cutter G, et al. Mortality in patients with multiple sclerosis. Neurology. 2013;81:184-192.
- Medicaid and CHIP Payment and Access Commission. Medicaid enrollment changes following the ACA. www.macpac.gov/subtopic/medicaid-enrollment-changes-following-the-aca/. Accessed August 9, 2019.
- National Multiple Sclerosis Society. Disease-modifying therapies for MS. Updated November 2019. www.nationalmssociety.org/NationalMSSociety/media/MSNationalFiles/Brochures/Brochure-The-MS-Disease-Modifying-Medications.pdf. Accessed August 9, 2019.
- McCool R, Wilson K, Arber M, et al. Systematic review and network meta-analysis comparing ocrelizumab with other treatments for relapsing multiple sclerosis. Mult Scler Relat Disord. 2019;29:55-61.
- US Food and Drug Administration. FDA Drug Safety Communication: new risk factor for progressive multifocal leukoencephalopathy (PML) associated with Tysabri (natalizumab). February 13, 2018. www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-new-risk-factor-progressive-multifocal-leukoencephalopathy-pml#hcp. Accessed August 9, 2019.
- Sagonowsky E. Teva’s patent failure gives long-acting Copaxone generics free rein. FiercePharma. October 15, 2018. www.fiercepharma.com/pharma/facing-generics-from-mylan-and-novartis-teva-loses-patent-appeal-copaxone. Accessed August 9, 2019.
- Abbas MZ. Evergreening of pharmaceutical patents: a blithe disregard for the rationale of the patent system. J Generic Med. 2019;15:53-60.
- Schondelmeyer SW, Purvis L. Rx Price Watch Report: Trends in Retail Prices of Specialty Prescription Drugs Widely Used by Older Americans, 2006 to 2015. Washington, DC: AARP Public Policy Institute; September 2017. www.aarp.org/content/dam/aarp/ppi/2017/08/trends-in-retail-prices-of-specialty-prescription-drugs-widely-used-by-older-americans.pdf. Accessed 9, 2019.
- Bin Sawad A, Seoane-Vazquez E, Rodriguez-Monguio R, Turkistani F. Price analysis of multiple sclerosis disease-modifying therapies marketed in the United States. Curr Med Res Opin. 2016;32:1783-1788.
- Grabowski HG, Guha R, Salgado M. Regulatory and cost barriers are likely to limit biosimilar development and expected savings in the near future. Health Aff (Millwood). 2014;33:1048-1057.
- Yue X, Guo JJ, Wigle PR. Trends in utilization, spending, and prices of smoking-cessation medications in Medicaid programs: 25 years empirical data analysis, 1991-2015. Am Health Drug Benefits. 2018;11(6):275-285.
- Almalki ZS, Yue X, Xia Y, et al. Utilization, spending, and price trends for quinolones in the US Medicaid programs: 25 years’ experience 1991–2015. Pharmacoecon Open. 2017;1:123-131.