Methods for Measuring Dose Escalation in TNF Antagonists for Rheumatoid Arthritis Patients Treated in Routine Clinical Practice

Transcription

1 Methods for Measuring Dose Escalation in TNF Antagonists for Rheumatoid Arthritis Patients Treated in Routine Clinical Practice Gu NY 1, Huang XY 2, Globe D 2, Fox KM 3 1 University of Southern California, Los Angeles, CA USA 2 Amgen, Inc., Thousand Oaks, CA USA 3 Strategic Healthcare Solutions, LLC., Monkton, MD USA

2 Acknowledgement This project was funded by Amgen and completed through the collaborative efforts of researchers from Amgen, Inc., Strategic Healthcare Solutions, LLC. and the USC Department of Clinical Pharmacy and Pharmaceutical Economics and Policy.

3 Introduction Subcutaneous (SC) injectable TNF antagonists such as Enbrel (etanercept) and Humira (adalimumab) are routinely prescribed for the treatment of moderate to severe rheumatoid arthritis (RA) According to product labels the recommended dose (RD) for etanercept is 50 mg/week administered as one SC injection or two 25 mg SC injections per week 4 the recommended dose (RD) for adalimumab is 40 mg every other week as one SC injection 5

4 Introduction It has been reported that to achieve adequate clinical response, dose increase may be needed for some RA patients 1,2,3 Dose increases will have cost implications given the linear relationship between dose and drug cost To date, there is no consensus on best/standard method to estimate dose increase

5 Study Objectives To compare rates of dose increase as determined in claims data of TNF antagonists for the treatment of RA, utilizing different analytic methods Assess the strengths, weaknesses and potential biases associated with each method and determine the most generalizable approach

6 Data The Medstat MarketScan administrative claims databases, Commercial Claims and Encounters and Medicare Supplemental and COB databases, 01/01/ /31/2004 Includes person-specific specific clinical utilization, expenditures and enrollment across inpatient, outpatient, prescription drug and carve-out services from approximately 45 large employers, health plans, and government organizations

7 Methods Index date was defined as patients first Rxs filled between 07/01/02 to 12/31/03 Baseline period was defined as 6 months prior to the index date Follow-up period was defined as 12 months post the index date

8 Study Design Study Intake Period Index Date 01/01/02 07/01/02 12/31/03 12/31/04 6-Month Baseline 12-Month Follow-Up

9 Inclusion Criteria Methods Claims from patients who had no biologic use in baseline period had at least one ICD - 9 diagnosis code for RA had 2 2 claims for the same biologic were continuously enrolled in the healthcare plan 6 months prior to (baseline) and 12 months post (follow- up) the index prescription

10 Exclusion Criteria Methods Claims from patients who were prevalent user of biologics (prescription for biologics within 6 months prior to the index date) switched biologics since the initial Rx were diagnosed with any of the following: Crohn s s disease Psoriasis Psoriatic arthritis Ankylosing spondylitis

11 Methods Method 1: Point estimate approach Comparing last Rx to the index Rx A patient was classified as having dose increase if the weekly dose of the last Rx was greater than the weekly dose of the index Rx Method 2: Average dose approach A patient was classified as having dose increase if the average weekly dose was greater than the RD Average weekly dose = total dispensed quantities in the study period / total days supply (in weeks)

12 Method 3: Comprehensive approach Methods Taking all Rxs and time into account Comparisons between the weekly dose of subsequent Rxs and the weekly dose of the index Rx Method 3a: Patient level approach A patient was classified as having dose increase if there were 2 incidences where the weekly dose of subsequent Rxs were greater than the weekly dose of the index Rx

13 Method 3: Method 3b: Patient level approach Method 3c: Methods A patient was classified as having dose increase if weekly dose of a subsequent Rx was greater than a predetermined percent of the index Rx (15%, 30% and 50%) Exposure adjusted approach Dose increase was estimated at each week based on patientweeks at risk and patient-weeks with dose increase (greater than the index Rx) Patient-weeks with dose increase/ Patient-weeks at risk

14 A few technical details Methods Weekly dose was calculated as: Dispensed metric quantities / Days supply in weeks To eliminate entry error, extreme doses were excluded Etanercept: weekly dose 15mg and 115mg Adalimumab: weekly doses 10mg and 50mg Separate analyses were conducted for patients initiated with high doses for both drugs High dose was considered as weekly dose greater than the RD defined in product labels

15 Results Table 1 Patient Characteristics Age, mean (SD) Gender, % female Patient residence, % Northeast North Central South West Unknown Insurance type, % Commercial Medicare Etanercept (n=1369) 50 ( 10.9 )* 989 (72.2%) 131 (9.6%) 459 (33.5%) 510 (37.2%) 266 (19.4%) 3 (0.2%) 1335 (97.5%)* 34 (2.5%) Adalimumab (n=461) 52 ( 9.4 ) 353 (76.6%) 37 (8.0%) 161 (34.9%) 178 (38.6%) 84 (18.2%) 1 (0.2%) 442 (96.1%) 18 (3.9%) *P<0.05

16 Results Table 2 Initial Dose Evaluation Initial Dose RD > RD Etanercept (n=1369) 97.2%* 2.8%* *P<0.001 RD: recommended dose according to product labels Adalimumab (n=461) 88.1% 11.9%

17 Results Method 1: 1 point estimate approach 16% 14% 12% 10% 13.5% 13.8% Dose Increase 8% 6.7% 6.2% 6% 4% 2% 0.0% 1.8% 0% All RD > RD Etanercept Adalimumab

18 Results Method 2: average dose approach 97.4% 98.2% 100% 80% 60% Dose Increase 40% 33.6% 24.9% 20% 10.3% 7.8% 0% All RD > RD Etanercept Adalimumab

19 Results Method 3a: patient level approach ( 2( 2 incidences) 20% 17.1% 18.7% 15% Dose Increase 10% 7.9% 8.1% 5.5% 5% 0.0% 0% All RD > RD Etanercept Adalimumab

20 Results Method 3b: patient level approach (>15% of index dose) 20% 16.9% 18.5% 15% Dose Increase 10% 7.5% 7.7% 5.5% 5% 0.0% 0% All RD > RD Etanercept Adalimumab

21 Results Method 3b: patient level approach (>30% of index dose) 20% 16.9% 18.5% 15% Dose Increase 10% 7.2% 7.4% 5.5% 5% 0.0% 0% All RD > RD Etanercept Adalimumab

22 Results Method 3b: patient level approach (>50% of index dose) 20% 15% 14.8% 16.0% Dose Increase 10% 5.5% 5.6% 5.5% 5% 0.0% 0% All RD > RD Etanercept Adalimumab

23 Results Method 3c: exposure adjusted approach 8% 7% 6% 5% Etanercept Adalimumab Dose Increase 4% 3% 2% 1% 0% Week of Therapy

24 Summary Table: Methods 1-31 Results All RD >RD Etanercept Adalimumab Etanercept Adalimumab Etanercept Adalimumab Method 1 6.7% 13.5% 6.2% 13.8% 0.0% 1.8% Method % 33.0% 7.8% 24.9% 97.4% 98.2% Method 3 >15% 7.9% 17.1% 8.1% 18.7% 0.0% 5.5% >30% 7.5% 16.9% 7.7% 18.5% 0.0% 5.5% >50% 5.5% 14.8% 5.6% 16.0% 0.0% 5.5%

25 Results Combining exposure adjusted estimates with % patient initiated on high dose 25% Etanercept Adalimumab 20% 15% % on High Dose 10% 5% 0% Week of Therapy

26 Study Limitations This study is subject to limitations associated with using administrative claims database Disease severity information was not available and hence not adjusted in the analysis

27 Conclusions Estimate of dose escalation is method dependent Simple approaches such comparing the last and first Rx were unable to capture all aspects of dose escalation Use of multiple methods in measuring dose escalation is recommended as some methods may better address the dosing patterns than the others Comprehensive approach such as Method 3 not only takes all Rxs into account, but also allows one to examine the dosing patterns over time

28 References 1. Schellekens H. Immunogenicity of Therapeutic Proteins: Clinical Implications and Future Prospects. Clin Ther ; 24: Sidiropoulos P., Boumpas D. Differential Drug Resistance to Anti-tumor tumor Necrosis Factor Agents in Rheumatoid Arthritis. Ann Rheum Dis 2006; 65: Finckh A. et al. Evidence for Differential Acquired Drug Resistance to Anti-tumor tumor Necrosis Factor Agents in Rheumatoid Arthritis. Ann Rheum Dis 2006; 65: etanercept (etanercept) Prescribing Information, Immunex Corporation, Thousand Oaks, CA adalimumab (adalimumab) Prescribing Information, Abbott Laboratories, North Chicago, IL 2007

29 Thank You!