In view of the limited data on the extent of treating-to-target (T2T) recommendations in the Asian spondyloarthritis (SpA) patient cohort, the Asia-Pacific League of Associations for Rheumatology (APLAR) SpA Special interest Group (SIG) established a multicenter registry for understanding the unmet needs and accessing the long-term clinical outcomes of T2T in patients.¹ Ultimately, the group aimed to improve disease management and advocate healthcare policy in Asia-Pacific countries with a strong supporting dataset.¹ In the 24^th APLAR Congress, Professor Tam, Lai-Shan from the Chinese University of Hong Kong discussed the up-to-date clinical analysis of T2T in the SpA population.¹

Patients who fulfilled the Classification Criteria for Psoriatic Arthritis (CASPAR) 2006 classification criteria for psoriatic arthritis (PsA) or 2009 The Assessment of Spondyloarthritis International Society (ASAS) criteria for axial SpA (axSpA) were recruited, regardless of prior disease-modifying antirheumatic drugs (DMARDs) treatment.¹ The registry comprised phase 1 as the cross-sectional study and phase 2 as the longitudinal study.¹

The phase 1 cross-sectional study provided a snapshot of baseline characteristics, including socioeconomic profile, disease activity, and medication use of participants enrolling in the APLAR SpA registry.¹ Some 351 individuals, including 129 PsA patients and 222 axSpA patients across 12 Asian countries were enrolled to receive 1-year intensive treatment using the  T2T approach with a follow-up every 3-6 months.¹ The primary outcomes of the proportion of patients who achieved the treatment targets were reviewed at 1 year.¹ Besides, axSpA was a predominantly male disease (81%), with the majority of patients testing human leukocyte antigen B27 (HLA-B27)-positive (84%) and imaging the presence of sacroiliitis in X-ray (84%), and magnetic resonance imaging (MRI) (66%).¹ PsA patients, however, had a higher prevalence of developing dactylitis.¹ In terms of treatment target achievement, 33% and 45% of PsA patients achieved minimal disease activity (MDA) and disease activity in psoriatic arthritis (DAPSA) low disease activity (LDA); while 26% and 65% of axSpA patients achieved ankylosing spondylitis disease activity (ASDAS)-LDA and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) <4.¹ Non-steroidal anti-inflammatory drugs (NSAIDs) and conventional synthetic DMARDs (csDMARDs) were the most commonly prescribed drugs to axSpA patients (80%) and PsA patients (79%), respectively.¹ For individuals who were on biologic or target synthetic DMARDs (b/tsDMARDs), 84% and 10% of axSpA patients were prescribed tumor necrosis factor (TNF) inhibitors and interleukin (IL)-17A/23 inhibitors, in comparison with 55% and 32% of PsA patients.¹

When the baseline characteristics were further compared with other PsA registries, patients from the APLAR SpA registry showed a lower achievement rate of MDA than the PsA International Database (PsArt-ID) (33% vs. 40%) but a higher rate of DAPSA-LDA (57% vs. 46%) than the CorEvitas PsA Registry.¹The prevalence of bDMARD use was similar in the APLAR SpA registry (38%) and PsArt-ID (40%) but lower than the CorEvitas PsA Registry (59%).¹ Indeed, patients who were on bDMARDs had a higher achievement rate of DAPSA-LDA than non-bDMARD users (69% vs. 52%, p=0.097).¹ The comparison between APLAR and the Netherlands SpA registries not only showed that the lower prevalence of bDMARD use achieved higher BASDAI <4 in the former (43%) than in the latter (56%), but also reported a higher proportion of patients on b/tsDMARDs achieving the treatment targets of BASDAI <4, (74% vs. 60%; p=0.029) and ASDAS-LDA (60% vs. 32%, p<0.001) than non-bDMARD users across the APLAR SpA registry and the Netherland SpA registry.¹ Conclusively, SpA patients have lower disease activities, better function, and are more prone to achieving the treatment targets with bDMARDs.¹

The phase 2 longitudinal study recruited 43 PsA patients and 49 axSpA patients across 5 Asia-Pacific regions.¹ This longitudinal study performed yearly follow-up up to 5 years to conduct an early assessment, measure diagnostic accuracy, and perform the protocol-driven tight control treatment targeting disease activity index (i.e., MDA or DAPSA for PsA patients; ASDAS-LDA for axSpA patients).¹ After the 1-year follow-up, no PsA patients showed the presence of sacroiliitis in X-ray and MRI or HLA-B27-positive, but a high prevalence of these disease features was continuously reported from the axSpA patient subgroups (i.e., 85%, 63% and 98%, respectively).¹ Notably, there was a significant reduction of tender joint count, swollen joint count, and dactylitis (26%-2%) in PsA patients.¹ The use of csDMARDS and b/tsDMARDs in PsA patients increased from 63% and 19% at baseline to 74% and 40% at a 1-year checkpoint, respectively; while the use of NSAIDs (40%-33%) and glucocorticoid (9% -5%) were reduced.¹ Comparatively, the use of csDMARDS in axSpA patients was less frequent (32%-19%), but b/tsDMARDs was >1.8-fold higher.¹ Regarding b/tsDMARDs, the use of anti-TNF was slightly dropped in both PsA and axSpA patients, while more patients were prescribed with anti-IL-17A/23 instead.¹ Patients with PsA reported lower disease activities by achieving MDA and DAPSA-LDA from 33% and 44% at baseline to 49% and 55% at 1-year follow-up, respectively.¹ Patients with axSpA showed a better outcome, with 79% achieving BASDAI <4 and 63% achieving ASDAS-LDA 1 year later.¹ The T2T achievement rates of MDA and DAPSA-LDA in PsA patients who used bDMARDs were 7% higher and 20% lower than that in non-bDMARD users, while axSpA patients on the bDMARDs treatment showed a higher prevalence of achieving ASDAS-LDA than non-bDMARD users (70% vs. 57%), regardless of the small sample size in this longitudinal study.¹

In conclusion, the APLAR SpA registry has proven a strong capacity to adopt the T2T strategy, with a significant improvement in disease activity over the Asia-Pacific region after 1-year treatment.¹ The use of b/tsDMARDs might be a good predictor of achieving the treatment targets, particularly when more supporting data are made available in the future.¹