Background/Purpose: Psoriatic Arthritis (PsA) is a chronic progressive inflammatory condition associated with significant direct and indirect costs. Tofacitinib is an oral Janus kinase inhibitor for the treatment of PsA. Economic evaluations, alongside clinical data, help inform payers and formulary decisions in the USA. To better understand the impact of including tofacitinib on US payer formularies for treatment of patients (pts) with moderately to severely active PsA with a previous inadequate response (IR) to a conventional synthetic disease-modifying antirheumatic drug (csDMARD), a decision tree model was designed to estimate and compare total costs, clinical responses, and per member per month (PMPM) costs between treatment sequences with and without tofacitinib.

Methods: The decision tree model was designed to estimate costs and outcomes from a third-party US payer perspective. In the base case, it was assumed the payer insured 1,000,000 individuals. The number of insured csDMARD-IR PsA pts was estimated from drug utilization and PsA epidemiology data. The analytical horizon was 2 years, with decision points for continuing/switching treatments occurring quarterly based on efficacy or occurrence of adverse events. The decision tree allowed for the comparison of multiple treatment strategies, each with up to four lines of advanced therapy for PsA. The base case compared a ‘tofacitinib treatment sequence’ (tofacitinib, adalimumab, etanercept, apremilast) vs a comparator sequence (adalimumab, etanercept, apremilast, secukinumab). Efficacy was measured using ACR20/50/70 and adverse event data were taken from US product information or published randomized clinical trials. The estimated total costs include the costs of treatment, monitoring, administration, and adverse events.

Results: Among 1,000,000 insurants, it was estimated that 274 csDMARD-IR PsA pts would receive an advanced therapy. The ‘tofacitinib treatment sequence’ was estimated to reduce total costs by $5,223,990 vs the comparator sequence without tofacitinib, with estimated total 2-year costs of $31,225,220 and $36,449,210, respectively; the PMPM cost of the ‘tofacitinib treatment sequence’ was $1.30 vs $1.52 for the comparator sequence. Over 2 years, it was estimated that 261 (95%), 171 (62%), and 81 (30%) patients in the ‘tofacitinib treatment sequence’ will achieve ACR20/50/70 responses, respectively, vs 252 (92%), 169 (62%), and 81 (30%) patients in the comparator sequence, respectively. Sensitivity analyses on treatment sequences and key parameters including drug cost, efficacy, and switching probability showed the model results to be robust with treatment sequences including tofacitinib consistently being cost-saving vs sequences excluding tofacitinib.

Conclusion: This model suggests including tofacitinib in treatments for csDMARD-IR PsA pts is a cost-saving alternative to treatment sequences without tofacitinib. The inclusion of tofacitinib on formulary for a payer insuring 1,000,000 individuals could reduce payer costs for PsA advanced therapies by more than $5 million.