Comparing medical utilization and cost outcomes in oral versus injectable immunotherapy users with chronic inflammatory joint and skin diseases

Abstract

Background: Rheumatoid arthritis (RA), psoriatic arthritis (PsA), and psoriasis (PSO) are immune-mediated systemic, chronic inflammatory conditions. Moderate to severe disease is treated with conventional disease-modifying antirheumatic drugs (DMARDs) such as methotrexate, sulfasalazine, or leflunomide. If a patient does not respond to these firstline treatments, then tumor necrosis factor inhibitor (TNFi) or non-TNFi immunotherapy agents are administered via infusion, injection, or taken orally. Although the effectiveness of established infusion, injection, and newer oral therapies are known, the relative effectiveness among the routes of administration is not well understood.

Objective: To compare drug use, health care resource utilization, and costs among patients who are treatment-naive to oral immunotherapy and injectable biologic immunotherapy.

Methods: This retrospective observational study used claims data from a large U.S. health plan to identify new users of oral and injectable immunotherapy, diagnosed with a joint (RA or PsA), skin (PSO), or joint and skin condition from July 1, 2014, to June 30, 2017. The index date was the first claim for an oral or injectable medication. Medicaid, Medicare Advantage, and commercial plan patients aged 19-89 years with continuous enrollment 6 months before and 12 months after the index date were included in the study. Outcomes were adjusted using propensity score by inverse probability of treatment weighting. Treatment discontinuation, switching, health care resource utilization, and costs were measured during the post-index period.

Results: Oral versus injectable users with joint (n = 458 vs. 3,875), skin (n = 265 vs. 951), or joint and skin (n = 171 vs. 805) conditions were identified. For drug utilization outcomes, no differences in discontinuation rates were observed between oral and injectable groups for any of the cohorts. However, those in skin and joint and skin cohorts had higher rates of switching to other immunotherapies in patients initiated on orals compared with injectables. Health care resource utilization outcomes were mixed. While mean outpatient and physician office visits were significantly higher in oral compared with injectable groups across all 3 cohorts, no differences were observed for inpatient stays. Total costs (medical plus pharmacy) were lower for oral groups across all 3 cohorts. Pharmacy costs were lower for oral groups, but medical costs were higher for oral groups across all 3 cohorts.

Conclusions: This is the first population-level study at a route-of-administration level, which compared switching, health care resource utilization, and costs across several conditions. Switching drugs was more likely in the oral group, which may indicate lower effectiveness or tolerability of oral immunotherapies relative to injectables. Health care resource utilization was higher in the oral group, but total costs were lower, which was likely driven by the lower costs of oral drugs.