Background/Purpose: The purpose of this study was to compare treatment patterns in the 2 years following the initiation of TNF inhibitor (TNFi) in AS patients.

Methods:  Adult patients with ≥ 2 AS diagnostic codes (ICD-9: 720.0 and ICD-10:M45.x) were included in this retrospective analysis of data from the Truven MarketScan Commercial Claims database. Patients who newly initiated a TNFi from 01/01/2009-12/31/2013 were indexed on their first TNFi. Patients were required to have a 1-year pre-index clean period of TNFi and continuous enrollment 1-year pre-index and 2-years post-index. Patients were excluded if they had ≥2 diagnostic codes for the following conditions: RA, juvenile idiopathic arthritis, PsA, Crohn’s disease, ulcerative colitis, plaque psoriasis, hidradenitis suppurarativa, or uveitis. Demographic, clinical, and treatment patterns were analyzed. Treatment patterns included switching to a new TNFi, discontinuation (≥90-day gap in therapy), or persistence (no gaps in therapy ≥90-days) during the 2-year follow-up period. Logistic regression analyses predicting persistent vs. non-persistent and switching vs. discontinuation were conducted.

Results: 1,372 AS patients (846 M/ 526 F) met the inclusion criteria for this study. Males (M) had a mean age of 44.29 years, while females (F) had a mean age of 42.31 years. Adalimumab was the first biologic for the majority of patients (44.6% M/ 43.3% F), followed by etanercept (40.4% M/ 41.6% F), infliximab (10.4% M/ 10.8% F), golimumab (4.6% M/ 3.8% F), and certolizumab pegol (0.0% M/ 0.4% F). During the follow-up period, 32.6% of males were persistent on their first TNFi, while only 22.8% of females were persistent. The majority of male (67.4%) and female patients (77.2%) discontinued their first TNFi during the 2-year follow-up period. Patients prescribed cDMARDs were more likely to be persistent, while females and opioid users were less likely to be persistent on their first TNFi (Table 1). Among those that discontinued their first TNFi, 32.8% (n=187) of males and 43.6% (n=177) of females switched to a 2^nd TNFi. Females, cDMARD users, and non-opioid analgesic users were more likely to switch to a 2^nd TNFi (Table 2).

Conclusion: This study suggests that approximately 67% of male AS patients and 77% of female AS patients newly initiating a TNFi do not remain on the index therapy 2 years post initiation. In this AS population, the proportion of female patients switching to a second TNFi is higher than the proportion of male patients.

Table 1. Logistic regression analyses predicting persistent vs. non-persistent to first TNFi

Table 2. Logistic regression analysis predicting switching TNFi vs. discontinuing TNFi