FormalPara Key Summary Points

Why carry out this study?

Patients with systemic lupus erythematosus (SLE) are at increased risk for organ damage, reduced health-related quality of life (HRQoL), and increased mortality.

Real-world studies have confirmed the positive clinical benefits of achieving Definition Of Remission In SLE (DORIS) remission or Lupus Low Disease Activity State (LLDAS) in all these domains. More recently, data from randomized controlled trials (RCTs) have confirmed benefits in HRQoL. This supports the need to evaluate the treat-to-target approach utilizing DORIS remission and LLDAS in future SLE RCTs and clinical practice.

What was learned from this study?

Studies show that treatment with novel biologic therapies for patients with SLE can increase attainment of DORIS remission and LLDAS. This has the potential to reduce disease progression, improve HRQoL, lower mortality, and lower healthcare costs.

DORIS remission and LLDAS are suitable for use as primary or secondary endpoints in future RCTs.

Introduction

Despite significant advances in the pathophysiologic understanding of systemic lupus erythematosus (SLE) and the development of novel therapies, patients with SLE are still at risk of progressive organ damage [1], have reduced health-related quality of life (HRQoL) [2], and significantly increased mortality [1, 3]. Assessment of SLE disease activity is challenging due to the complex and diverse disease manifestations, requiring composite disease-activity measures (e.g., Systemic Lupus Erythematosus Disease Activity Index 2000 [SLEDAI-2K]) that may not accurately evaluate SLE activity [4].

Though remission is the recommended treatment target in SLE, low disease activity is a more clinically feasible treatment target that conveys clinical benefits similar to remission [5, 6]. Here we summarize the evolution of remission and low disease activity definitions in SLE, the evidence supporting the clinical benefits associated with attainment, and the implications for a treat-to-target (T2T) approach in clinical practice utilizing remission and low disease activity as targets.

This article is based on previously conducted studies and does not contain any new studies with human participants or animals performed by any of the authors.

Past: Defining Remission and Low Disease Activity in SLE

Definition Of Remission In SLE (DORIS), developed by the DORIS task force, is the widely adopted set of remission criteria in SLE [7]. DORIS remission is defined as achieving a clinical SLEDAI-2K = 0 and a Physician’s Global Assessment (PGA) < 0.5, irrespective of serology, with permitted use of antimalarials, low-dose glucocorticoids (GCs; prednisolone ≤ 5 mg/day), and/or stable doses of immunosuppressants, including biologics (Table 1) [7]. Thus, DORIS remission reflects the absence of clinical disease activity. Some experts have referred to the absence of clinical and serological activity as a “complete remission” [8]. Other remission definitions with different stringencies, such as no treatment or normal serology, are attained even less often, and studies do not suggest they offer significant operational advantages over DORIS remission [7]. Prior to the development and validation of the DORIS remission definition, several definitions of remission were utilized, but none were universally accepted [9].

Table 1 DORIS remission and LLDAS definitions
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While remission (based on DORIS or other definitions) remains the recommended treatment target, few patients in real-world SLE cohorts achieve remission [10,11,12,13]. In the longitudinal Hopkins Lupus Cohort (including 1356 patients with SLE), patients spent 27% and 13% of their follow-up time in DORIS remission on-treatment and off-treatment, respectively [11]. In a multinational longitudinal cohort study of 1707 patients with SLE in the Asia Pacific region, patients were in DORIS remission on treatment for 36.1% of time and remission off treatment for 10.8% of time [14]. In the Peking University First Hospital SLE (PKUFHS) cohort, 30.2% (56/185) achieved DORIS remission, 25.4% (47/185) achieved complete remission, both on treatment, while no patients achieved DORIS remission off treatment [13]. Among 218 patients in the PKUFHS cohort with treatment-naïve SLE, DORIS remission or complete remission on treatment (67.9% and 43.1%, respectively) was more common compared with clinical or complete remission off treatment (10.6% and 8.3%, respectively) [10]. Similarly, in an analysis of 115 patients from the Pisa SLE cohort, 45% experienced DORIS remission on treatment (including 26% with complete remission on treatment) and 12% experienced remission off treatment (including 2% with complete remission) [12]. Given that remission is not feasible for most patients with SLE, especially based on more stringent definitions, a low disease activity definition was necessary to provide a practical SLE treatment goal [15].

The Lupus Low Disease Activity State (LLDAS) was developed in 2013 and the initial definition was published in 2016 by the Asia Pacific Lupus Collaboration (APLC) as an intentionally less stringent state compared with remission, which can define a ceiling for acceptable disease and treatment burden [5, 15, 16]. LLDAS is defined as a SLEDAI-2K ≤ 4, with no activity in major organ systems and no new features of activity compared to previous assessment, and PGA ≤ 1, while receiving a prednisolone (or equivalent) dose of ≤ 7.5 mg/day and standard maintenance doses of immunosuppressive drugs and approved biological agents (Table 1) [15]. In 2019, a longitudinal study provided validation for LLDAS, and sensitivity analysis supported a simplified definition of LLDAS that removed the requirement to exclude gastrointestinal and hematological activity [16]. Other studies have included a more stringent variation termed LLDAS5, which includes patients with LLDAS and a GC dosage ≤ 5 mg/day [10, 12].

Evidence suggests that LLDAS is a more stringent goal compared with other traditional treatment response measures, such as British Isles Lupus Assessment Group–based Composite Lupus Assessment (BICLA) and SLE Responder Index of 4 (SRI[4]) [17, 18]. In an analysis of phase 3, placebo-controlled trials of anifrolumab, LLDAS was achieved by 58.5% of BICLA responders and 53.4% of SRI(4) responders [17]. A post hoc analysis of pooled phase 3 trials with 10 mg/kg of belimumab showed that 12.5–14.4% of patients attained LLDAS [18]. Importantly, a longitudinal study found that achieving LLDAS, but not SRI(4), was highly associated with treatment de-escalation, suggesting that LLDAS can better correlate with clinical decisions in a real-world setting [19].

Present: Applying DORIS Remission and LLDAS Definitions

In recent years, DORIS remission and LLDAS T2T endpoints have been included as secondary or exploratory endpoints or in post hoc analyses of randomized controlled trials (RCTs) of SLE therapies (Table 2).

Table 2 SLE RCTs with DORIS remission and LLDAS endpoints
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DORIS remission and LLDAS have also been applied in analyses of different SLE subpopulations and real-world patient cohorts. The cumulative evidence from RCTs and real-world SLE cohorts supports the favorable clinical outcomes in terms of disease activity and progression, treatment response, HRQoL, and health-care costs in patients achieving DORIS remission or LLDAS.

Disease Activity and Progression

Attainment of LLDAS and DORIS remission is associated with slowing or halting of disease progression and reduced mortality. For instance, a recent study established a direct association between DORIS remission or LLDAS rates and reduction in disease damage accrual in patients with SLE from a primarily Mestizo population [20]. In a longitudinal study of 3384 patients from the APLC cohort, failure to attain LLDAS was associated with significantly higher disease activity, higher GC dosing, and increased mortality [21]. In another longitudinal analysis of 3811 patients with SLE from the APLC cohort, mortality risk was significantly reduced in patients who achieved LLDAS at any given visit or were in LLDAS for at least 50% of the observed time (LLDAS-50) (adjusted hazard ratio (HR) [95% confidence interval (CI)]: 0.20 [0.11–0.38] and 0.51 [0.31–0.85], respectively) [22]. Protection from mortality was similar for the attainment of DORIS remission compared to LLDAS, but interestingly was superior for remission with lower cutoffs of prednisolone dose, and especially GC-free remission [22]. The long-term historical study of the Milan Systemic Lupus Erythematosus Consortium (SMiLE) cohort demonstrated that DORIS remission and LLDAS rates steadily increased from disease onset through 20 years of follow-up, and patients who attained either treatment target at the 20-year timepoint had about half the flare risk in the next 10 years compared with those who did not [9].

The time spent in DORIS remission and LLDAS is an important determinant in disease outcomes. Patients achieving LLDAS-50 had significantly better survival and a lower risk of developing severe disease damage over time compared with patients not achieving LLDAS in an analysis of 206 patients with SLE in the Tromsø Lupus Cohort [23]. In the SMiLE cohort, long-term sustained DORIS remission or LLDAS status was protective against increased late flare risk [9]. A longitudinal cohort study of 185 Chinese patients with SLE also demonstrated that those who achieved and spent more time in DORIS remission or LLDAS had a significantly higher flare-free survival rate compared with patients who spent less time in those states [13].

Treatment Response

Several RCTs in patients with SLE have failed to achieve prespecified endpoints due to an inability to discriminate between active treatments and placebo using traditional single-index primary endpoints [24, 25]. DORIS remission and LLDAS, however, can robustly discriminate between clinical benefits observed with treatment vs. placebo in RCTs (Table 3).

Table 3 DORIS remission and LLDAS outcomes in SLE RCTs
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In post hoc analyses of the phase 2b MUSE and phase 3 TULIP-1 and TULIP-2 trials, a significantly higher proportion of patients receiving anifrolumab 300 mg plus standard of care (SoC), compared with placebo plus SoC, achieved LLDAS by week 52 [17, 26]. Anifrolumab treatment was associated with earlier time to first LLDAS attainment (HR [95% CI]: 1.76 [1.35–2.30]), more cumulative time spent in LLDAS thresholds of ≥ 20% and ≥ 50% (odds ratio (OR) [95% CI]: 2.1 [1.5–2.9] and 2.6 [1.6–4.3], respectively), and a higher chance of sustained LLDAS for at least 3, 5, or 7 consecutive visits (OR [95% CI]: 2.0 [1.4–2.8]; 2.1 [1.4–3.3], or 2.8 [1.6–4.9], respectively) compared with placebo [17]. In the TULIP long-term extension (LTE) post hoc analysis, pooled data were analyzed from TULIP-1/TULIP-2 baseline through week 208 in patients with moderate to severe SLE treated with anifrolumab 300 mg plus SoC [27]. Anifrolumab treatment resulted in more cumulative time (months) in LLDAS (least squares [LS] mean difference: 5.26 [95% CI: 2.34–8.17]) and more sustained LLDAS for at least 3, 5, 7, or 9 consecutive visits (OR [95%]: 1.8 [1.1–2.9]; 1.7 [1.0–2.9]; 2.0 [1.0–3.8]; and 2.2 [1.0–4.6], respectively) compared with placebo during the 4-year TULIP-LTE period [28].

In the pooled phase 3 data of the BLISS-52 and BLISS-76 trials, LLDAS achievement was significantly greater in patients receiving belimumab 10 mg/kg compared with placebo at week 52 [18]. Treatment with deucravacitinib (3 or 6 mg twice daily or 12 mg daily) in the phase 2 PAISLEY trial also led to greater LLDAS achievement compared with placebo at week 48 [29]. In an analysis of 158 patients with high disease activity (HDA; defined as a SLEDAI-2K ≥ 10) in a phase 2b RCT, attainment of LLDAS was significantly higher in patients receiving atacicept 150 mg compared with placebo [30]. However, LLDAS rates between treatment and placebo arms were similar in the phase 3 trials of baricitinib (SLE-BRAVE-I, -II) and belimumab (BLISS-BELIEVE), and the phase 2b trial of atacicept 75 mg (ADDRESS II) [30,31,32].

DORIS remission rates were significantly higher in patients receiving anifrolumab 300 mg compared with placebo in a pooled post hoc analysis of TULIP-1/TULIP-2 (Table 3) [17]. Patients receiving anifrolumab spent more cumulative time and percentage of time in DORIS remission compared with placebo in a TULIP post hoc analysis [33]. Patients treated with anifrolumab spent more cumulative time in remission thresholds of ≥ 20% (OR [95% CI]: 2.2 [1.3–3.7]) and ≥ 50% (2.7 [1.0–7.0]) and were more likely to be in sustained remission for at least 3, 5, or 7 consecutive monthly visits (2.4 [1.4–3.9]), 3.0 [1.5–6.1], or 2.6 [1.1–6.4], respectively) [33]. No significant differences in DORIS attainment between atacicept or belimumab vs. placebo were observed in post hoc analyses of ADDRESS II or BLISS-BELIEVE, respectively [30, 31]. Data on DORIS remission rates with other SLE biologic therapies under investigation have not yet been reported.

DORIS remission and LLDAS have also been evaluated in small studies of chimeric antigen receptor (CAR) T-cell therapy in patients with SLE. In a study assessing the efficacy of a CD19 CAR T-cell therapy, five patients with SLE refractory to other treatments achieved DORIS remission within 3 months of treatment [34]. In a separate study of four patients with SLE treated with CD19 CAR T-cells, all patients met LLDAS criteria and were able to discontinue all SLE-specific medication, including GCs [34].

HRQoL and Healthcare Costs

DORIS remission and LLDAS attainment significantly improve HRQoL outcomes in patients with SLE. In BLISS-52/-76, DORIS remission and LLDAS attainment were associated with better self-reported HRQoL outcomes on the 36-item Short Form Health Survey (SF-36) [35]. Better HRQoL in patients attaining LLDAS was also reported in a post hoc analysis of the anifrolumab phase 2 trial [26]. In two longitudinal analyses of patients from the APLC cohort, SF-36 scores were higher in patients who attained LLDAS compared with those who did not [36, 37]. In a single-center study in Australia, the annual direct medical cost for patients achieving LLDAS-50 was significantly reduced by 25.9% compared with patients not attaining LLDAS-50 [38]. As targeted treatments such as biologics improve the ability to attain LLDAS and DORIS remission, in part through reducing disease activity and GC use, they have also been shown to improve HRQoL in patients with SLE [18, 26, 39].

Future: Clinical Trial Endpoints Using DORIS Remission and LLDAS

The consistent incorporation of DORIS remission and LLDAS criteria in future RCTs may improve the quality of clinical data and facilitate comparability across trials. Currently, there are several ongoing clinical trials of SLE therapies or therapeutic approaches that include DORIS remission or LLDAS as primary or secondary endpoints.

LLDAS is the primary endpoint and DORIS remission is a secondary endpoint in the single-arm, 24-week pilot study investigating the efficacy of belimumab treatment in 16 patients with early SLE [40]. Another ongoing pilot study of belimumab in early SLE is using both DORIS remission and LLDAS as secondary endpoints [41], and LLDAS is included as a secondary outcome measure in phase 3 trials of deucravacitinib [42].

DORIS remission is a secondary endpoint in a trial examining the effectiveness of a rapid GC tapering method in up to 120 patients with SLE with associated immune thrombocytopenia [43]. Similarly, a longitudinal study examined GC tapering on frequency and determinants of disease flare in 185 patients with SLE who achieved DORIS remission or LLDAS [13]. Likewise, LLDAS and DORIS are primary endpoints in an RCT evaluating the utility of telemedicine follow-ups in 144 adults with SLE [43].

Future: Adoption of DORIS Remission and LLDAS as T2T Objectives in Clinical Practice

T2T is a therapeutic strategy that proactively identifies and directs treatment adjustments with the goal of achieving a practical, clinically relevant target. T2T approaches have demonstrated capability to alleviate the long-term outcomes and reduce the clinical risks of chronic conditions, while also driving real-world clinical decision making. The T2T approach has been adopted in other rheumatological disease states, including rheumatoid arthritis, psoriatic arthritis, spondyloarthropathies, and gout [6, 44, 45]. The TICORIA trial was the first randomized controlled longitudinal study to investigate the T2T approach in rheumatology, as it showed that T2T approaches to reduce disease activity were associated with improved responses to therapy in patients with rheumatoid arthritis and higher remission rates [6, 46].

To date, various SLE T2T strategies have been proposed; however, few have been assessed (Table 4) [47,48,49,50]. The ongoing LUPUS-BEST study will be the first RCT to directly compare the impact of T2T approaches (either DORIS remission- or LLDAS-targeted T2T) with standard care on SLE disease and HRQoL outcomes [50]. This approach will allow for benefit–risk comparisons between treatment targets and may provide crucial insights for the utilization of T2T in clinical practice moving forward.

Table 4 Summary of recent and ongoing T2T investigations and studies
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Implementing T2T for patients with SLE will require a clear consensus regarding which measures will be used to track disease activity. Given the clinical advantages demonstrated with attaining DORIS remission or LLDAS, these are the current highest priority recommendations for T2T implementation [5].

SLE Disease Course

Given that relapses are common during the SLE disease course [51], potential T2T targets should include a proposed target duration based on the minimum time required in DORIS remission or LLDAS states to experience positive clinical outcomes. Current evidence supports 2–3 years as an important minimum duration of DORIS remission needed to protect against disease damage accrual, as no significant differences were observed between patients achieving 3-year vs. 5-year DORIS remission in a study following patients with SLE for over 41 years [47, 52]. Much larger observational cohort studies had sufficient statistical power to detect protective effects of shorter durations of LLDAS attainment [52], but this may not translate to everyday practice and the minimum protective duration of LLDAS is yet to be defined. The minimum duration of time patients spent in DORIS remission or LLDAS to achieve minimal clinically important differences (MCIDs) in the SF-36 and other HRQoL measures ranged from 16 to 68 weeks, depending on the HRQoL measure and if time spent in these states was cumulative or consecutive [35]. A shorter time in DORIS remission compared with LLDAS was needed to attain MCIDs in HRQoL measures, except when DORIS and LLDAS were sustained, in which the benefit with both targets was achieved within a shorter time [35].

Measuring DORIS Remission and LLDAS in the Clinic

DORIS remission and LLDAS criteria require regular SLEDAI-2K assessments, which are currently not recorded by all rheumatologists in clinical practice [53]. However, measuring a patient’s SLEDAI-2K score is simple, with low administrative burden [54], and its implementation in clinics should be encouraged.

T2T treatment approaches also require more frequent patient evaluations than may be undertaken in current clinical practice. Digital tools may help accommodate the greater frequency of evaluations necessary and could help alleviate the need for an increased number of in-person visits.

Without formal measurement, there is the potential for discordance between physician opinion of remission/low disease activity and DORIS remission/LLDAS criteria, respectively. In a study of 304 patients treated in real-world clinical practice, 70.4% of patients who did not fulfill LLDAS criteria were classified by their physicians as having low disease activity or remission, suggesting that LLDAS can be more stringent than a physician’s opinion of disease activity [55]. In another study comparing physician judgment with formal definition, survey responses from physicians were collected before publication of the operational LLDAS definition, and a third of cases not in LLDAS/remission were misclassified by experienced clinicians [56].

Achieving Individual DORIS Remission and LLDAS Components

Several rate-limiting factors in the achievement of all DORIS remission or LLDAS components have been identified. A single center cross-sectional study of 233 patients with SLE demonstrated that the most common reasons for patients not achieving DORIS remission were PGA ≥ 0.5 (43.0%), clinical SLEDAI-2K > 0 (11.0%), and daily prednisone doses > 5 mg/day (8.0%) [57]. In a separate study of 79 patients with severely active SLE, 8 patients (10.1%) did not attain LLDAS within 1 year of follow-up, primarily due to not meeting the criteria for prednisolone dose ≤ 7.5 mg/day (87.5%) or SLEDAI-2K ≤ 4 with no new organ involvement (62.5%) [49]. Similar findings were reported in a post hoc analysis of non-attainment of LLDAS in the phase 3 anifrolumab studies, as lower proportions of patients met the SLEDAI-2K or PGA criteria compared with other LLDAS components at week 52 [17].

Treatment Selection and Adherence

Implementation of a T2T strategy is likely to involve changing therapies more frequently than standard care. This may have an impact on treatment adherence, especially when approved treatment options are limited and patients may exhaust available options without reaching their target. Shared decision making between patients and physicians is recommended by the European Alliance of Associations for Rheumatology (EULAR) and may help to manage these issues [5], and setting a less stringent target such as LLDAS as an initial target might be beneficial.

A T2T strategy may lead to patients who are not at target to discontinue treatments that are moderately effective in favor of an alternative treatment that may prove less effective. Patients with SLE who achieve LLDAS may still benefit from additional medication to further reduce disease activity[40]. Therefore, after achieving LLDAS, patients should continue to be treated with the aim of sustaining the target to maximize clinical benefit.

Conclusions

Achievement of DORIS remission or LLDAS can significantly reduce disease progression, improve HRQoL, lower mortality, and lower healthcare costs for patients with SLE. LLDAS could be a pragmatic goal for T2T in the clinic. Studies show that novel therapies such as biologics can make LLDAS and DORIS remission attainable clinical targets, reducing disease activity and GC use as well as improving HRQoL in patients with SLE. Further, sufficient evidence supports the utility of DORIS remission and LLDAS as robust and reliable endpoints for use as secondary, if not primary, endpoints in future SLE RCTs.

Implementation of a T2T strategy in SLE is now abundantly supported by data and is moving towards clinical reality. Widespread adoption of DORIS remission and LLDAS as T2T objectives may help overcome obstacles with T2T implementation and translate to better clinical outcomes for more patients.