Background/Purpose: We have previously reported the efficacy and safety results of ustekinumab (UST), an IL-12/23 p40 inhibitor, in patients with active psoriatic arthritis (PsA) up to 2yrs of UST treatment from the PSUMMIT 1&II trials. Here, we describe the sustained effects of UST using the modified Psoriatic Arthritis Response Criteria (PsARC) response. Although not validated, the modified PsARC has been widely used in PsA clinical trials and clinical practice. Methods: Adult PsA patients with active disease (≥5 SJC and ≥5 TJC; CRP≥0.3mg/dL [ULN 1.0 mg/dL]) despite DMARD and/or NSAID therapy (PSUMMIT 1, n=615; PSUMMIT 2, n=312 [of which 180 pts were previously treated with DMARD and/or NSAID, and prior anti-TNFα therapy]) were randomized to UST45mg, 90mg, or PBO at wks 0, 4, and q12wks, thereafter. PBO-treated pts were crossed over to UST45mg at wks24 and 28 followed by q12wk dosing. At wk16, patients with <5% improvement in TJC & SJC entered blinded early escape [EE] (PBO→UST45mg; UST45mg→90mg; 90mg→90mg). No concomitant DMARDs with the exception of MTX (approx 50% of patients in each study) were permitted.  Patients were considered a responder using the modified PsARC if improvement was demonstrated in ≥ 2 (including≥1 of the joint criteria) of the following criteria and no deterioration was noted in the other criteria:  ≥30% decrease in the swollen joint count, ≥30% decrease in the tender joint count, ≥20% improvement in the patient’s overall assessment (VAS), and ≥20% improvement in the physician’s overall assessment (VAS). The proportion of patients who were modified PSARC responders and ACR 20 non-responders at wk28 were assessed.

Results:  Modified PSARC results are summarized in Table 1.  Statistically significantly higher PSARC response rates were observed as early as wk4 for both UST groups vs PBO in the PSUMMIT 1 trial and statistically significantly higher responses were also observed at wks 8, 12 and 24 for both UST dose groups vs PBO in both trials.  Responses in both UST dose groups continued to increase after wk24, reached a plateau at wk28 and were maintained through wk52.  Patients who were initially randomized to PBO and crossed over to 45mg achieved similar responses to those originally randomized to UST. Higher PSARC responses were consistently observed at wk8-24 for both UST groups vs PBO regardless of baseline MTX status. The early onset of PSARC responses observed was consistent with early onset of ACR20 responses. UST was generally well-tolerated.

Conclusion:   Significantly higher PSARC responses were observed as early as wk4-8 for both UST dose groups vs PBO. Improvements observed at wk24 continued to increase at wk28 and were sustained through wk52.