Kathleen Wilson, MPH

: To compare estimated actual dosing of etanercept and ustekinumab in patients with psoriasis and/or psoriatic arthritis with recommended dosing, and to estimate annual cost of these psoriasis treatments.

: Retrospective, observational cohort study.

: Administrative claims data from a commercial claims database from January 1, 2010, through December 31, 2013, were analyzed. Patients had a diagnosis of psoriasis and/or psoriatic arthritis, and continuous enrollment with medical and pharmacy benefits for the 12-month preindex period and the 12-month post index follow-up period. Dosing was determined with actual-to-expected dose ratios computed while patients were persistent to therapy. Expected dose was calculated according to US Package Inserts; expected weight-based dosing of ustekinumab was estimated using random weight assignment based on starting dose. Annual psoriasis-related costs consisting of biologics, nonbiologic psoriasis therapies, and psoriasis-related healthcare utilization were calculated.

: Data from 2997 patients (2128 etanercept, 869 ustekinumab) were analyzed. Actual-to-expected dose ratios (SD) for etanercept and ustekinumab were 0.939 (0.304) and 1.169 (0.687), respectively, for all patients; 1.012 (0.295) and 1.164 (0.666) for patients with psoriasis but without psoriatic arthritis; and 0.783 (0.261) and 1.203 (0.813) for patients with psoriatic arthritis. Annual costs (SD) for all patients were $28,291 ($13,296) and $37,537 ($17,209) for etanercept and ustekinumab, respectively; for psoriasis patients without psoriatic arthritis, they were $29,712 ($13,988) and $36,976 ($16,817), respectively; and for patients with psoriatic arthritis, they were $25,246 ($11,084) and $41,068 ($19,199), respectively.

Conclusions: Actual-to-expected dosing ratios and annual costs were lower for etanercept than for ustekinumab in patients with psoriasis and/or psoriatic arthritis.

Actual use of medications is important for payers to predict the cost of a treatment. Low variation between actual versus expected dosing can reduce the uncertainty of drug expenses, which can be beneficial from the payer’s budgeting perspective. There is a lack of evidence on actual dosing versus expected dosing patterns and costs of biologic therapies used for psoriasis and/or psoriatic arthritis. Drugs that possess the combined characteristics of low expected cost and minimal uncertainty of such cost would be optimal to payers.

Etanercept (a tumor necrosis factor inhibitor) and ustekinumab (an interleukin [IL]-12 and IL-23 blocker) are commonly used biologic therapies for the treatment of moderate to severe plaque psoriasis, with both drugs being efficacious in treating psoriatic arthritis. Etanercept for psoriasis is administered subcutaneously (SC) at a starting dose of 100 mg/week for 12 weeks followed by a maintenance dose of 50 mg/week.

 Ustekinumab is administered SC based on weight: 45 mg for patients weighing ≤100 kg (220 lbs) and 90 mg for patients >100 kg, with the first 2 doses 4 weeks apart followed by a dose every 12 weeks.

 These biologics are expected to be generally representative of biologics used to treat plaque psoriasis that use standard dosing and weight-based dosing.

A study by Thayer et al that examined actual versus expected dosing with etanercept showed that patients with psoriasis and/or psoriatic arthritis used 89% to 107% of the expected dose based on claims data from 2003 to 2008.

 This wide range was dependent on whether dosing was based on the psoriasis or psoriatic arthritis indication. Actual versus expected dosing patterns and costs for ustekinumab or other biologics used to treat moderate to severe plaque psoriasis have not been reported to date. The objective of this study was to estimate current actual dosing of etanercept and ustekinumab in patients with psoriasis and/or psoriatic arthritis and compare it with the recommended dosing in the US Package Inserts (USPIs), and to estimate annual psoriasis-related costs.

Data for this analysis were obtained from the Truven Health MarketScan Commercial Claims and Encounters Database. This database contains the annual inpatient, outpatient, and outpatient prescription drug experience of 30 million commercially insured US patients. Enrollees are covered under a variety of fee-for-service and managed care health plans, including exclusive provider organizations, preferred provider organizations, point-of-service health insurance plans, indemnity plans, and health maintenance organizations.

This was a retrospective, observational cohort study based on US administrative claims data from the Truven Health MarketScan® Commercial Database. Data were collected from January 1, 2010, through December 31, 2013 (Figure 1). The first new claim for etanercept or ustekinumab (index agent) between January 1, 2011, and December 31, 2012, was the index event/date. The baseline period comprised the 12 months prior to the index date, and the follow-up period was the 12 months after the index date. Patients were new to any biologic and had no outpatient medical claim or prescription claim for any biologic approved prior to initiation of the index agent.

Inclusion criteria were: an outpatient medical or prescription claim for etanercept or ustekinumab between January 1, 2011, and December 31, 2012; continuous enrollment with medical and pharmacy benefits for the 12-month baseline period and the 12-month follow-up period; aged 18 to 63 years on index date; and a diagnosis of psoriasis (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] code 696.1x) and/or a diagnosis of psoriatic arthritis (ICD-9-CM code 696.0x) during the baseline period. Exclusion criteria included a diagnosis for any other indication for etanercept, including rheumatoid arthritis (ICD-9-CM code 714.0x), juvenile idiopathic arthritis (ICD-9-CM code 714.3x), or ankylosing spondylitis (ICD-9-CM code 720.0x); evidence of index biologic medication use during the baseline period; evidence of ≥2 claims for a different biologic on the index date; or evidence of receiving an outlier dose during the follow-up period. Outlier doses for etanercept were <12.25 mg (half the minimum label dose) or >200 mg (double the maximum label dose) per week, and for ustekinumab were <11.25 mg or >180 mg per claim.

Outcomes included the estimate of the ratio of actual dosing to expected dosing as defined by the USPI while persistent on index medication (no gap ≥45 days and no switching) during the follow-up period. For patients on ustekinumab, patient weight was inferred because weight data are not included in the database. Individual patient weight was assigned based on starting dose such that patients who initiated ustekinumab with an initial dose >67.5 mg were assumed to be high-weight patients (>100 kg) who required a dose of 90 mg; the remaining patients who initiated at a dose ≤67.5 mg were considered low-weight (≤100 kg), requiring a dose of 45 mg (weight based on starting dose). A preliminary query of the data indicated that 47.4% of patients initiated a dose closer to 90 mg per claim, while 52.6% of patients initiated with a dose closer to 45 mg per claim. As a sensitivity analysis, weight distributions from similar age and gender groups were derived from clinical trial data,

 where ~69% of psoriasis patients weighed ≤100 kg and 31% weighed >100 kg. Patient weight was assigned as a dichotomous variable so that the distribution of the study sample matched the weight distribution reported by Lebwohl et al (midpoint weight assignment).

These weight distributions were used to inform the expected dose for ustekinumab in this study population, and results for patients on ustekinumab represent the average for the entire cohort.

Annual treatment costs during the follow-up period were calculated. Costs included index biologic costs, total biologic therapy costs (for patients who switched biologics), and total psoriasis-related costs. Psoriasis-related costs included the cost of inpatient, outpatient, emergency department claims with a diagnosis of psoriasis in the primary diagnosis position, and costs of all nonbiologic and biologic agents approved for psoriasis treatment, including topical prescription therapy, phototherapy, and oral or intravenous corticosteroids. Healthcare costs were adjusted to 2013 US dollars using the Medical Care component of the Consumer Price Index.

This study was descriptive only, and no formal hypothesis was tested. Actual dosing data were calculated during the time period when patients were persistent (no gap ≥45 days and no switching). Descriptive results were stratified by diagnosis (all psoriasis patients with or without psoriatic arthritis, psoriasis patients without psoriatic arthritis, and patients with psoriatic arthritis). Chi-square and t tests were used to compare categorical and continuous variables, respectively, between etanercept and ustekinumab.

A total of 2997 eligible patients (2128 etanercept, 869 ustekinumab) were identified in the database. The mean age was 45 years, and slightly more than half of patients were male (Table 1). Patients on etanercept and those on ustekinumab had similar baseline Deyo Charlson Comorbidity Index scores. More patients on etanercept had psoriatic arthritis (n = 677; 31.8%) compared with patients on ustekinumab (n = 119; 13.7%).

For psoriasis patients with or without psoriatic arthritis, the actual mean (SD) dose for etanercept was 2176 (1255) mg and was 195 (130) mg for ustekinumab during the 12-month follow-up. Ratios of actual doses to expected doses were slightly higher for patients on ustekinumab based on random weight assignment than for patients on etanercept (Figure 2). In the sensitivity analysis, ratios were lower for ustekinumab based on midpoint weight assignment compared with weight based on starting dose.

Total psoriasis-related costs were lower for etanercept than for ustekinumab during the 12-month follow-up period (P <.001), including index biologic costs (P <.001) and other psoriasis- or psoriatic arthritis—related costs (P = .034) (Table 2). Annual costs (SD) for all patients were $28,291 ($13,296) and $37,537 ($17,209) for etanercept and ustekinumab, respectively; for psoriasis patients without psoriatic arthritis, they were $29,712 ($13,988) and $36,976 ($16,817); and for patients with psoriatic arthritis, they were $25,246 ($11,084) and $41,068 ($19,199). Across all patients, the annual cost for biologic therapy (SD) was $26,784 ($13,072) for etanercept and $35,686 ($16,897) for ustekinumab.

In this study of real-world etanercept and ustekinumab dosing patterns for moderate to severe plaque psoriasis and/or psoriatic arthritis, we found higher than expected rates of high-dose ustekinumab use. In contrast, actual doses of etanercept were lower than expected across all patients and for those patients with psoriatic arthritis, and were slightly above expected doses among patients with psoriasis only. Managers of healthcare plans that attempt to predict costs of ustekinumab should consider these findings and should not make assumptions on weight-based dosing based on patient populations enrolled in clinical trials.

Trends observed in this study are consistent with an analysis of administrative claims data by Thayer et al

 that evaluated etanercept treatment patterns in psoriasis patients with and without psoriatic arthritis. In the Thayer study, patients with only psoriasis received 107% of the expected dose (compared with 100% in our analysis), and patients with psoriatic arthritis received 89% of the expected dose (compared with 78% in our analysis).

A possible reason for the differences in etanercept and ustekinumab actual-to-expected dosing ratios observed in our study may be due to dose escalations and reductions. An analysis based on administrative claims data showed that patients on etanercept had a higher rate of dose escalation at 12 months of treatment (41.0%) compared with those on ustekinumab (35.9%), but the etanercept cohort also had higher rates of dose reductions (48.7%) compared with the ustekinumab cohort (37.4%).

 A cross-sectional study of a clinical practice in Spain reported dose escalation in 17.9% and 4.2% of patients on ustekinumab and etanercept, respectively, and dose reductions in 46.4% and 41.6%.

 The overall annual mean reduction in dose per patient was 0.9% for ustekinumab and 13.8% for etanercept.

 In a phase 3 trial of ustekinumab, 51% of patients had an increase in dose based on an efficacy algorithm.

 In a randomized controlled trial of etanercept, dose reductions were not associated with a decrease in efficacy.

Limitations of the study were inherent to the use of claims data for retrospective analyses. The results are limited to individuals with commercial health coverage and may not be generalizable to uninsured or underinsured patients, or those on Medicare. Claims could be misclassified and could be subject to data coding and entry errors. Cost data were associated with outpatient medical procedures, and line items could not be identified separately, which may have affected cost estimations. Administrative claims data do not contain information on disease severity or effects of treatment. It is not possible to determine whether patients had only psoriatic arthritis, which may warrant a different dosing regimen. Also, dose and weight distributions were not comparable with the results from the study used to estimate weight distributions.

 In this analysis, a higher proportion of patients (~50%) initiated at 90 mg, resulting in higher than expected doses using the random weight assignment for ustekinumab. It is possible that some patients received ustekinumab at an incorrect weight-based dose (eg, a 45-mg dose for a patient who weighed more than 100 kg).

Patients initiating psoriasis and/or psoriatic arthritis treatment with etanercept had a 20% lower actual-versus-expected dosing ratio while persistent on therapy and 25% lower total annual psoriasis-related costs than did patients initiating ustekinumab. These results suggest that products with variable dosing, such as ustekinumab, can introduce cost-related uncertainties for payers.

Dikran Toroser (Amgen Inc) and Julia R. Gage (on behalf of Amgen Inc) provided medical writing support.

: Truven Health Analytics (MB, KW, AH), Cambridge, MA; Amgen Inc (DHT, DJH, BSS), Thousand Oaks, CA.

: This study was sponsored by Immunex, a wholly owned subsidiary of Amgen Inc, and by Wyeth, which was acquired by Pfizer in October 2009.

: Dr Bonafede, Ms Wilson, and Ms Huang are employees of Truven Health Analytics, which received funding from Amgen Inc, for this study. Dr Tang is a former employee and current shareholder of Amgen Inc.

Drs Harrison and Stolshek are employees and shareholders of Amgen Inc.

: Concept and design (MB, DHT, KW, AH, DJH); acquisition of data (MB, KW, AH); analysis and interpretation of data (MB, DHT, KW, AH, DJH, BSS); drafting of the manuscript (MB); critical revision of the manuscript for important intellectual content (MB, DHT, KW, AH, DJH, BSS); statistical analysis (MB, KW, AH); provision of patients or study materials (MB); administrative, technical, or logistic support (DHT, KW, AH); and supervision (DHT, BSS).

 Machaon Bonafede, PhD, MPH, Truven Health Analytics, 150 Cambridge Park Dr, Cambridge, MA 02140. E-mail: 

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Articles

For patients with psoriasis and/or psoriatic arthritis, actual-to-expected dosing ratios and costs were lower for etanercept than for ustekinumab.