OBJECTIVES: To investigate the cost per retention year for ustekinumab (UST) relative to infliximab (INF) in first line treatment of psoriatic arthritis (PsA) in Russian plaque psoriasis patients (PSO). METHODS: A 10 year Markov model was constructed with UST and INF as first line biologic therapies and a two-step rescue therapy consisting of adalimumab (ADA) as the second line biologic for both treatment arms and non-biologic supportive care of oral methotrexate 15mg/week (BSC) if the patient fails ADA. Transition probabilities were obtained from PSOLAR, an observational longitudinal study studying the safety of biologics in PSO and PsA, by fitting 5-year time-on-treatment data for self-identified PsA patients with confirmed PSO to a Weibull model and extrapolating over 10 years. All patients were assumed to have failed prior non-biologic therapy and retention on therapy was used as the target endpoint. Direct treatment costs were calculated from the perspective of the Russian Ministry of Health, converted to 2014 euros (1 RUB = € 0.0197) and discounted at 5%, as per Russian pharmacoeconomic guidelines.  RESULTS: Over a 10 year horizon, INF-ADA-BSC was associated with a higher cost and a lower amount of retention years while the UST-ADA-BSC treatment line gives an additional 0.68 biologic retention years per patient and a potential savings of € 29370 per patient with ustekinumab as first-line biologic treatment. However, these results were sensitive to changes in biologic drug prices and by extension, the market share of biosimilars.  CONCLUSIONS: An increased retention time is usually correlated with higher patient satisfaction levels as well as response and safety. According to our model, initiating biologic therapy with ustekinumab is cost saving compared to the current first choice biologic, infliximab.  However, further research has to be initiated to quantify the relationship between increased patient retention and additional gain in treatment response and safety.