International consensus on dose reduction of biologics for patients with psoriasis: The DR. Delphi study

Abstract

Background

Dose reduction (DR) of biologics for psoriasis is already applied in clinical practice but without clear guidelines, while dermatologists addressed the need for guidance. An international consensus may contribute to optimal implementation of biologic DR in clinical psoriasis practices.

Objectives

This consensus study aims for international consensus on DR of biologics in adult patients with psoriasis among dermatologists worldwide.

Methods

An international, modified eDelphi consensus study was performed among dermatologists worldwide. A total of 11 statements on biologic DR were generated by the international steering committee, based on a previous literature review. Invitations were distributed via international dermatological societies. Participants rated their level of agreement per statement on a 9‐point Likert scale. A maximum of three consensus rounds and one (digital) consensus meeting were expected. Statements reached consensus if ≥70% agreed and <15% disagreed; otherwise, statements were revised for a next consensus round.

Results

In total, 62 dermatologists from Europe, South America, Asia, North America, Africa and Australia completed the eDelphi. After one round, 9 out of 11 statements reached consensus. The remaining 2 statements were adapted and reached consensus in the second round. Participants agreed on criteria when to consider and initiate/(dis)continue DR and on a two‐step DR algorithm for adalimumab, etanercept and ustekinumab. Participants agreed that this two‐step DR strategy can also be considered for IL‐17 and IL‐23 inhibitors while awaiting more scientific evidence on DR of these newer biologics.

Conclusions

Dermatologists worldwide reached consensus on when and how to initiate and (dis)continue DR of biologics, and on a two‐step DR algorithm for adalimumab, etanercept and ustekinumab in adult patients with psoriasis. DR of IL‐17 and IL‐23 inhibitors was deemed feasible; however, underlying evidence is still limited. This first international consensus provides essential information for uptake and implementation of biologic DR for psoriasis on a global scale.

Plain Language Summary

Psoriasis is a chronic immune‐mediated disease causing erythematous, scaly, itchy patches interfering with a patient's quality of life. Psoriasis affects 2%–3% of the world population.

• Biologics like TNFα, IL‐12/23, IL‐17 and IL‐23 inhibitors (i) are highly effective treatments improving quality of life. However, as these drugs are prescribed in a fixed, registered dose, patients with controlled disease might be overtreated. Dose reduction (DR) of biologics might reduce avoidable overtreatment, reduce costs and possibly avoid adverse events. DR is already applied in daily practice but without clear (inter)national guidelines, while dermatologists addressed the need for more guidance in previous studies. This study aims for international consensus on DR of biologics in adult patients with psoriasis among dermatologists worldwide.

• In this international, modified eDelphi consensus study, a total of 62 dermatologists rated their level of agreement on a total of 11 statements on criteria for biologic DR. Statements reached consensus if ≥70% agreed and <15% disagreed; otherwise, statements were revised for a next voting round. It was expected that a maximum of three voting rounds and one (digital) consensus meeting was necessary to reach consensus on all statements.

• After two rounds, all statements reached consensus. Dermatologists agreed on criteria when to consider and initiate/(dis)continue DR, and on a two‐step DR algorithm for adalimumab, etanercept (TNFαi) and ustekinumab (IL‐12/23i). The two‐step DR strategy was also deemed feasible for IL‐17i and IL‐23i; however, underlying evidence remains limited.

• This international consensus contributes to a clearer and safer uptake of biologic DR in clinical practice globally.

Dermatologists worldwide reached consensus on criteria for dose reduction (DR) of biologics for psoriasis resulting in a DR algorithm for adalimumab, etanercept and ustekinumab. DR of IL‐17 and IL‐23 inhibitors was deemed feasible as well. This first international consensus provides essential information for uptake of biologic DR for psoriasis globally.

Why was the study undertaken?

Biologics are highly effective and improve quality of life in patients with psoriasis. However, as these drugs are prescribed in a fixed, registered dose, patients with controlled disease might be overtreated. Dose reduction (DR) of biologics might reduce avoidable overtreatment, reduce costs and possibly avoid adverse events. DR is already applied in daily practice but without clear (inter)national guidelines, while dermatologists have addressed the need for more guidance in previous studies.

What does this study add?

This international, modified eDelphi consensus study aims for international consensus on biologic DR in adult patients with psoriasis among dermatologists worldwide. This study provides the first international consensus on criteria when to consider, initiate, continue or discontinue DR, and a clear DR algorithm for adalimumab, etanercept and ustekinumab. Participants agreed that the DR strategy can already be considered for IL‐17 and IL‐23 inhibitors while awaiting more scientific evidence.

What are the implications of this study for disease understanding and/or clinical care?

This international consensus contributes to a clearer and safer uptake and implementation of biologic DR in clinical practice on a global scale, which can be incorporated in future guidelines. Future research on the efficacy and safety of DR of IL‐17 and IL‐23 inhibitors is needed to reach consensus on a more specified DR strategy of these biologics in the near future.

INTRODUCTION

Biologic treatment of patients with psoriasis has become a mainstay over the past years as biologics are highly effective and improve quality of life in patients with psoriasis. On the other hand, biologics are expensive drugs often prescribed in a fixed, registered dose and patients with a good response might be overtreated. Dose reduction (DR) of biologics might reduce avoidable overtreatment, reduce costs and possibly avoid adverse events. Previous studies tested DR strategies of mainly TNFα inhibitors (i) (adalimumab, etanercept) and the IL‐12/23i (ustekinumab) in adult patients with psoriasis and showed that this is (cost‐)effective and safe. ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ , ¹⁵ In addition, when the DR strategy failed, retreatment with the standard dose or previous effective dose resulted in regaining an adequate treatment response. ⁸ , ⁹ , ¹⁶ Studies on DR of IL‐17i and IL‐23i remain scarce, especially randomized controlled trials. ¹⁵ In previous international (questionnaire) studies, dermatologists expressed the need for consensus or a guideline regarding biologic DR as it is currently applied in clinical practice without clear guidelines. ¹⁷ , ¹⁸ , ¹⁹ Therefore, this international eDelphi consensus study aims for consensus on biologic DR by interval prolongation in adult patients with psoriasis among dermatologists worldwide, contributing to optimal implementation of an effective and safe biologic DR strategy in clinical practice.

MATERIALS AND METHODS

To achieve international consensus regarding criteria for biologic dose reduction (DR), an online modified Delphi procedure (eDelphi) was conducted from September to November 2024. The ACCORD (ACcurate Consensus Reporting Document) guideline was used to report on this eDelphi ²⁰ ; for extended methods see Appendix S1.

The eDelphi consisted of multiple rounds of statements on biologic DR, which were rated anonymously by an expert panel. The statements were developed by an expert Steering Committee (SC) including the main investigators (EdJ, JvdR, CvR and LvdS), board members of the Skin Inflammation and Psoriasis International Network (SPIN) (WHB, JL, PS), and a patient member of the International Federation of Psoriasis Associations (IFPA) and the Dutch Patient Federation (‘Psoriasispatiënten Nederland’) (IvE). Statements were based on a literature search (end date July 2023) on DR of biologics in psoriasis, ¹⁵ , ²¹ , ²² and on expert opinion.

In total, 11 statements were generated and each statement was accompanied with a summary of available evidence. Additional to the statements, multiple choice questions (MCQs) on criteria of initiating and discontinuing DR were added as they could provide additional information for future research for refining DR algorithms. Appendix S2 shows the used questionnaires.

Before the questionnaires went live, they were piloted by the SC and one independent researcher.

Recruitment of the expert panel

Dermatologists or dermatology residents worldwide, experienced with biologic treatment of adult patients with psoriasis, were asked to participate in the eDelphi expert panel; recruitment took place between September and November 2024. An information leaflet was sent by e‐mail to all members of SPIN, the International Psoriasis Council (IPC) and the European Academy of Dermatology and Venerology (EADV) Task Force Psoriasis, consisting of several hundred experts from around the globe with a special interest in inflammatory diseases, including current leading psoriasis experts. Invitations were also shared via social media channels of SC members, SPIN and IPC. Informed consent was obtained from all participants.

Data collection

After registration, each participant was pseudonymized prior to voting. A subject identification log was only accessible for the main investigators for study purposes only. Each round, participants received the link to the questionnaires from the online system Castor EDC. ²³ The statements and the summary of available evidence were in English, but the menu and navigational buttons could be translated to the participant's preferred language. In case of incomplete questionnaires, automatic reminders were sent weekly, up to a maximum of 4 weeks. If a questionnaire remained incomplete, the participant was encouraged to complete the questionnaire via a personal email.

Per round, each statement was rated on a 9‐point Likert scale, with 1 to 3 labelled ‘not important/disagree’, 4–6 ‘important but not critical/neither agree nor disagree’ and 7–9 ‘critical/agree’, and each was provided with a blank text box for additional comments. In case any rating level of agreement of 1–3 (not important/disagree) was selected, participants were asked to explain/justify their response. The additional MCQs asked participants' preferred physician‐ and/or patient‐reported outcome(s) to guide DR, and which scores of these outcomes they preferred as thresholds to initiate and (dis‐)continue DR. The first round also included questions on participants' demographics. See S2 for the complete questionnaire of round 1 including the MCQs.

The SC aimed for a maximum of 3 rounds of voting and 1 (digital) consensus meeting in case not all statements reached consensus after 3 rounds. After each round, results were analysed to determine whether consensus on statements was reached. To reach consensus, ≥70% of all participants required a rating level of agreement of 7–9 (critical/agree) and <15% required 1–3 (not important/disagree). As there are no universal standards on which level of agreement indicates consensus in eDelphi studies, the consensus definition from previous dermatology studies was used. ²⁴ , ²⁵ , ²⁶ Results of each round were summarized and discussed within the SC. Per statement, individual suggestions and additional comments were grouped to either (i) ‘leave something out of the criteria/lower threshold than stated’, (ii) ‘add something to the criteria/higher threshold than stated’ and (iii) ‘other’. Statements which already reached strong consensus, either agreement or disagreement, would not be included in the subsequent round. The SC reconsidered and/or redefined statements in which no consensus was reached for a subsequent consensus round based on input provided by the participants.

Data analysis and ethics

Data were analysed with IBM SPSS Statistics 29. Descriptive statistics were used to analyse demographic participant data, percentages of voters per level of agreement on consensus statements and the results of the MCQs. As a sensitivity analysis, all analyses were repeated in which the voting members of the SC were now also included.

This study was conducted according to the ICH GCP guidelines and the principles of the Declaration of Helsinki. Data collection was performed in accordance with the Dutch Act on Implementation of the General Data Protection Regulation; in Dutch: ‘Uitvoeringswet AVG’. This study was exempted for the Medical Research Involving Human Subjects Act (WMO) by the Medical Ethical Committee Arnhem‐Nijmegen.

RESULTS

The first round of the eDelphi started September 24, 2024, and ended November 17, 2024. A total of 70 experts registered for participation, of whom 63 completed the first round. Consensus was reached on 9 statements; the 2 statements without consensus were redefined by the SC (Appendix S2). Consensus on both redefined statements was reached in the second round between January 7, 2025 and February 20, 2025 by 62 participants. One participant dropped out during the second round due to time constraints.

Demographic characteristics

Demographic participant data showed that psoriasis experts from Europe, South America, Asia, Africa, North America and Australia participated in the eDelphi (Figure 1).

FIGURE 1.

Overview of participating countries.

Table 1 shows demographic characteristics of the participants in both rounds. Mean age of the participants was 47.7 years and a small majority was male. The majority (71%) worked as a dermatologist in an academic setting. Participants were experienced with biologic treatment for almost 15 years on average and almost all participants were experienced with biologic DR. For around 84% of all participants, dose adjustments were allowed in their country of practice with the majority being allowed to both increase and reduce the dose.

TABLE 1.

Demographic characteristics of the participants per round.

Demographic characteristics of participants
	Round 1 (N = 63)	Round 2 (N = 62)
Age (years)	47.7 (±10.9)	47.7 (±10.9)
Male	34 (54.0%)	33 (53.2%)
Setting
Academic hospital/University medical center	45 (71.4%)	44 (71.0%)
Private hospital/clinic/practice	13 (20.6%)	13 (21.0%)
General hospital	8 (12.7%)	8 (12.9%)
Function
Dermatologist	58 (92.1%)	57 (92%)
Dermatologist in training	4 (6.3%)	4 (6.5%)
Physician assistant	1 (1.6%)	1 (1.6%)
Number of years experienced with biologic treatment	14.6 (±5.6)	14.5 (±5.6)
Number of participants experienced with biologic DR
Yes	57 (90.5%)	56 (90.3%)
No	6 (9.5%)	6 (9.7%)
Dose adjustment allowed in country of practice
Yes	53 (84.1%)	52 (83.9%)
Dose increase	2 (3.8%)	2 (3.9%)
Dose reduction	5 (9.4%)	5 (9.6%)
Dose increase and reduction	46 (86.8%)	45 (86.5%)
No	7 (11.1%)	7 (11.3%)
Not known	3 (4.8%)	3 (4.8%)

Note: Results are presented as mean with standard deviation (±) or frequency (%).

Abbreviation: DR: dose reduction.

Consensus of statements

In the first round, consensus was reached regarding criteria when to consider/initiate, (dis)continue and how to apply DR by interval prolongation (Table 2). Statement 8 and 11 did not reach consensus. Based on participants' comments on these two statements, the revised statement 8 was made less imperative and allowed for personal preferences by adding: ‘In addition, the time between first and potential second step of DR can also be individualized based on physicians' and patients' preferences’ (Table 3). The time schedule included in the original statement, of at least 3 and 6 months between the first and potential second step of DR for, respectively, a short and longer injection interval, was not further extended as it was already a minimum. Comments on statement 11 were mainly about individualization/tailoring of DR of IL‐17i and IL‐23i to the patients' disease activity/preference. Therefore, the phrase ‘…, but the DR steps can be individualized based on physicians' and patients' preferences …’ was added. The scheme of the two‐step interval prolongation for IL‐17i and IL‐23i (first to 67% of the standard dose, subsequently to 50%) was maintained but was made less imperative while awaiting more scientific evidence (Table 3).

TABLE 2.

Overview of the 11 statements of round 1 (N = 63) with the results per statement shown as frequencies (%).

TABLE 3.

Overview of the 2 revised statements of round 2 (N = 62) with the results per statement shown as frequencies (%).

As a sensitivity analysis, votes of the SC (N = 7) were added to the analysis. As a result, statement 8 in its original form would have reached consensus in round 1 already (N = 49 agreed (70.0%) compared to N = 44 (69.8%) without the SC). Although the number of participants that agreed with statement 11 increased to N = 47 (67.1%) when adding the SC responses, consensus was not reached in the first round. In round 2, the revised statements 8 and 11 also reached consensus when the votes of the SC were included (78.3% agreement and 85.1% agreement, respectively). Based on the statements that reached consensus, an internationally agreed algorithm for biologic DR was developed (Figure 2).

FIGURE 2.

Algorithm for biologic dose reduction (DR) in patients with plaque psoriasis. The algorithm is the result of the statements that reached consensus in this international eDelphi study.

Multiple choice questions

In addition to consensus statements, we explored experts' thoughts and beliefs on which physician‐ and/or patient‐reported outcome they would prefer to guide DR by adding MCQs in round 1. It was shown that the majority preferred the absolute Psoriasis Area and Severity Index (PASI) as physician‐reported outcome (N = 52; 82.5%) and the Dermatology Life Quality Index (DLQI) as patient‐reported outcome (N = 52; 82.5%) to guide DR (Table 4). Some experts did not want to include a physician‐ or patient‐reported outcome as they found patient satisfaction more important; also, patient‐reported outcomes were found time consuming and unreliable. Figure 3 shows that experts preferred different absolute PASI scores as thresholds at which they would initiate DR (ranging from ≤0 to ≤3) or return to the standard/previous effective dose (ranging from ≥2 to ≥5). Also, different DLQI scores were preferred at which experts would initiate DR (ranging from ≤0 to ≤3); but the majority would return to the standard/previous effective dose at a DLQI score of ≥5. However, some participants would return to the standard/previous effective dose at a DLQI score >10.

TABLE 4.

Overview of the 2 multiple choice questions of round 1 (N = 63) with the results shown as frequencies (%).

Which physician‐reported outcome on disease activity would you prefer to guide dose reduction? (multiple answers possible)	N (%)
Absolute Psoriasis Area and Severity Index (PASI)	52 (82.5%)
Relative PASI (compared to PASI at the start of the biologic, e.g. PASI90)	10 (15.9%)
Static Physician Global Assessment (PGA)	23 (36.5%)
Body Surface Area (BSA) (absolute)	23 (36.5%)
Other (please specify)	4 (6.3%)
I do not want to include a physician‐reported outcome on disease activity to guide dose reduction (please specify)	2 (3.2%)

Which patient‐reported outcome on quality of life would you prefer to guide dose reduction? (multiple answers possible)	N (%)
Dermatology Life Quality Index (DLQI)	52 (82.5%)
Skindex‐29	2 (3.2%)
Other (please specify)	7 (11.1%)
I do not want to include a patient‐reported outcome on quality of life to guide dose reduction (please specify)	5 (7.9%)

FIGURE 3.

Overview of the scores of the absolute PASI and DLQI at which participants would initiate dose reduction (a, c) and would return to the standard dose or previous effective dose (b, d). Only participants who preferred the absolute PASI as the physician‐reported outcome (N = 52) and those who preferred the DLQI as the patient‐reported outcome (N = 52) were able to respond. DLQI, Dermatology Life Quality Index; N, number of participants; PASI, Psoriasis Area and Severity Index.

Results were comparable for the sensitivity analysis including answers of the SC (N = 7).

DISCUSSION

With this international modified eDelphi study, consensus was reached on criteria regarding dose reduction (DR) by interval prolongation of biologics for adult patients with psoriasis resulting in an internationally agreed algorithm for biologic DR (Figure 2). Psoriasis experts from almost all continents participated and reached consensus on all 11 statements within two rounds. Experts agreed that prior to initiation of biologic DR, disease activity should be controlled for ≥6 months with the same biologic. The decision to initiate DR should be based on shared decision‐making, disease activity and quality of life and a rheumatologist should be consulted in case of concomitant psoriatic arthritis. After initiation, disease activity needs to be monitored by a combination of at least one physician‐ and at least one patient‐reported outcome on disease activity and disease‐related quality of life. Regarding the DR strategy, experts agreed that DR of TNFαi (adalimumab, etanercept) and the IL‐12/23i (ustekinumab) should preferably be applied by two‐step injection interval prolongation, with the first step resulting in 67% of the standard dose (1.5‐fold extension of the interval in standard dose) and the second step resulting in 50% of the standard dose (2‐fold extension of the interval in standard dose). It should be considered to return to the standard or previous effective dose when disease activity increases due to DR, or when patients do not feel comfortable with their lowered dose. In general, experts deemed ≥3 months acceptable as time between the first and second DR step of a biologic with a short interval, but it was agreed that it should be longer (≥6 months) for a biologic with a longer interval. In general, it was stressed by the experts that there should also be room for individualization of the DR schedule. It was deemed acceptable to already apply DR for IL‐17i and IL‐23i in individual cases, in anticipation of more scientific evidence.

The statements on the DR strategy of the two‐step injection interval prolongation specific for adalimumab, etanercept and ustekinumab are based on a large body of evidence regarding safety and efficacy. ¹ , ² , ³ , ⁴ , ⁵ , ⁶ , ⁷ , ⁸ , ⁹ , ¹⁰ , ¹¹ , ¹² , ¹³ , ¹⁴ Additionally, a previous prospective cohort study showed that most patients were able to achieve their prior PASI scores when returning to the standard dose after DR failed. ¹⁶ Also, previous studies on continuous or interrupted treatment of biologics showed that most patients responded adequately to retreatment by the standard dose. ²⁷ , ²⁸ , ²⁹ Infliximab, a TNFαi, was excluded from the statements on purpose as a previous systematic review showed that patients developed increased levels of antidrug antibodies (ADAs) against infliximab when the dose was reduced by interval prolongation. ³⁰ Previous studies on ADA development in patients on DR of adalimumab, etanercept and ustekinumab showed no (relevant) ADA development, nor a significant difference in ADA levels between DR and standard dose for adalimumab (in n = 7 in Benzaquen et al. ³¹ and n = 25 in Atalay et al. ³² ) and ustekinumab (in n = 20 in Atalay et al. ³² and n = 302 in Blauvelt et al. ¹² ). ¹² , ³¹ , ³² The more cautious wording in the statement on DR of the newer biologics (IL‐17i and IL‐23i) is due to the fact that the available evidence prior to this eDelphi, where the statements were based on, was limited to studies each focusing on a single biologic (IL‐17i is secukinumab and brodalumab, and IL‐23i guselkumab, with variable results). ³³ , ³⁴ , ³⁵ After completion of this eDelphi, additional studies on DR of individual IL‐17i and IL‐23i have been published including one randomized controlled trial (RCT). This RCT evaluated early intervention with, and prolonging the injection interval for, guselkumab in super responders and showed non‐inferiority of 100 mg every 16 weeks versus every 8 weeks (GUIDE study). ³⁶ These super responders were patients that achieved PASI 0 at both 20 and 28 weeks with guselkumab, illustrating the specific nature of this group which may hamper the generalizability to the overall population of psoriasis patients on biologics. Other additional studies were case reports or small retro−/prospective cohort studies on secukinumab, ixekizumab, bimekizumab, risankizumab and tildrakizumab. ³⁷ , ³⁸ , ³⁹ , ⁴⁰ , ⁴¹ , ⁴² Despite their lower level of evidence, they all showed promising results of DR; though, larger randomized trials are needed. The results of an international, multicentre, randomized, controlled, non‐inferiority study (the BeNeBio trial) on DR of IL‐17i and IL‐23i are expected to be published in the coming year. ⁴³

The multiple choice questions (MCQs) at the end of the first consensus round were added to provide insight in experts' thoughts and beliefs regarding the use of physician‐ and patient‐reported outcomes to guide DR. The majority preferred the PASI and DLQI to guide DR, which is in line with previous studies. However, the experts of this eDelphi study mainly preferred lower thresholds for PASI and DLQI to initiate DR compared to the thresholds of ≤5 in a Dutch eDelphi, ²² and also lower than most of the PASI scores used as a threshold in previous studies, which had a wide range up to PASI <8. ² , ⁴ , ⁶ , ⁷ , ⁸ , ⁹ , ⁴⁴ , ⁴⁵ Over time, dermatologists could have adjusted their opinion on these thresholds as nowadays they are more experienced with the highly effective biologic treatment of psoriasis. Important to note is that thresholds guiding DR are not treatment goals but serve as upper limits to be able to act in clinical practice and are not goals that need to be achieved when applying DR. It would be valuable to reach consensus on thresholds of physician‐ and patient‐reported outcomes to guide DR, enabling more concise policymaking. However, as the preferred thresholds within the panel varied considerably, the feasibility of such a consensus study in a global context is questionable. Our current algorithm is adaptable to the current leading outcomes and thresholds within a dermatologist's clinical practice making it applicable for everyone.

To our knowledge, this is the first international consensus on DR of biologics for adult patients with psoriasis. One of the strengths is that participants were pseudonymized and blinded for each other's answers during each consensus round to minimize risk of bias. Also, members of the SC participated in both consensus rounds, but to ensure that no bias was introduced, their votes were only included in a sensitivity analysis, which did not result in different results. All continents were represented in this consensus; however, it should be noted that the majority of participants were from Europe/Western countries. This could be due to the greater access to dermatological care and biologics in these countries compared to, for example, Africa, making dermatologists more keen to participate. Not every country allows or reimburses DR, resulting in the continued use of fixed, registered doses of biologics. For these countries in particular, this consensus could contribute to the uptake of DR, as it shows that DR is an accepted part of current scientific and clinical psoriasis practice. In addition, previous studies have shown that dermatologists worldwide are pending consensus or a guideline on biologic DR. This consensus potentially provides a starting point for future guidelines, both nationally and internationally. It is important to note that local guidelines are decisive for local policy, despite (inter‐)national guidelines. Therefore, individual clinics would already be able to implement biologic DR based on this consensus while awaiting (inter‐)national guidelines.

There are also some limitations. This consensus might be less generalizable due to a relatively small number of experts that participated considering the large networks used to invite experts. Despite the smaller panel, the expert panel was above sufficient to generate reliable results as, in general, at least 23 participants who are similarly trained and have a general understanding in the field of interest are considered sufficient for a Delphi consensus study. ⁴⁶ , ⁴⁷ The expert panel of this eDelphi consisted of dermatologists and dermatology residents who were all experienced in the field of psoriasis and biologics, including world‐leading psoriasis experts. In addition, the number of participants remained remarkably consistent throughout the two consensus rounds, thereby enhancing the reliability of the results. Around 10% of the participants had no experience with biologic DR; therefore, their ability to rate the statements could be questioned. However, each statement was accompanied by a summary of available evidence facilitating access to the current literature, enabling every participant to rate the statements.

In conclusion, this eDelphi provides the first international consensus on when and how to apply biologic DR for adult patients with psoriasis including a clear algorithm for DR of adalimumab, etanercept and ustekinumab. To reach future consensus on a specific DR strategy for IL‐17i and IL‐23i, additional high‐quality evidence is needed. This evidence is expected in the near future, possibly enabling an update to this consensus study within the next one to two years. Future research is also needed to identify both thresholds guiding DR and treatment goals separately on a global scale, to enable more concise policymaking regarding biologic DR internationally. This consensus can be the start of an international guideline on biologic DR for psoriasis leading towards international implementation of biologic DR, which would be beneficial for patients, physicians and healthcare systems.

AUTHOR CONTRIBUTIONS

C. A. M. van Riel: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, supervision, validation, visualization, writing—original draft, writing—review and editing. W.‐H. Boehncke: conceptualization, methodology, validation, writing—review and editing. J. L. W. Lambert: conceptualization, methodology, validation, writing—review and editing. P. I. Spuls: conceptualization, methodology, validation, writing—review and editing. L. S. van der Schoot: conceptualization, methodology, validation, writing—review and editing. I. van Ee: conceptualization, writing—review and editing. E. M. G. J. de Jong: conceptualization, funding acquisition, methodology, project administration, supervision, validation, visualization, writing—review and editing. J. M. P. A. van den Reek: conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, supervision, validation, visualization, writing—review and editing.

FUNDING INFORMATION

Funding was (partially) provided by the European Academy of Dermatology and Venereology (EADV).

CONFLICT OF INTEREST STATEMENT

CAMR has no conflicts of interest to disclose. W‐HB has received honoraria as a speaker and/or advisor from AbbVie, Almirall, Eli Lilly, Leo, Novartis and UCB. JLWL has received research grants from and/or acted as consultant/speaker for and has acted as consultant for AbbVie, Almirall, Amgen, Argenx, Eli Lilly, Janssen‐Cilag, LEO Pharma, Novartis, Pfizer and UCB. All funding is not personal and goes to an independent research account of the department of dermatology of Ghent University Hospital, Ghent, Belgium. PS is Chief Investigator (CI) of the systemic and phototherapy atopic eczema registry (TREAT NL/BE) for adults and children and receives departmental independent research grants for TREAT NL/BE registry from Pharma since December 2019. She is member of the TREAT Registry Taskforce (TrT) Executive Committee. The TrT receive research grants for specific projects to combine data of different national registries. PS is involved in performing clinical trials with many pharmaceutical industries that manufacture drugs used for the treatment of, for example psoriasis and atopic dermatitis, for which financial compensation is paid to the department/hospital. PS was involved in the development of one of the HOME core outcome instruments (Recap of atopic eczema (RECAP)), and in the development of the Outcome Measures for VAscular Malformations (OVAMA) questionnaire for vascular malformations. PS is project lead of the governmental funded UPDATE trial to investigate NB‐UVB in atopic dermatitis. She has recently done a consultancy for Takeda (2025). LSS carried out clinical trials for Janssen and Novartis and received speaking fees from Janssen and Eli Lilly. All funding is not personal but goes to the independent Research Fund of the Department of Dermatology of the Radboud University Medical Center Nijmegen, The Netherlands. IE has no conflicts of interest to disclose. EMGJJ has received research grants for the independent research fund of the department of dermatology of the Radboud university medical center Nijmegen, the Netherlands from AbbVie, BMS, Janssen Pharmaceutica, Leo Pharma, Novartis and UCB for research on psoriasis and has acted as consultant and/or paid speaker for and/or participated in research sponsored by companies that manufacture drugs used for the treatment of psoriasis or eczema including AbbVie, Amgen, Almirall, Celgene, Galapagos, Janssen Pharmaceutica, Lilly, Novartis, Leo Pharma, Sanofi and UCB. All funding is not personal but goes to the independent research fund of the department of dermatology of Radboud University medical center Nijmegen, the Netherlands. JMPAR carried out clinical trials for AbbVie, Celgene, Almirall and Janssen and has received speaking fees/attended advisory boards from Zoetis, AbbVie, Janssen, BMS, Almirall, LEO Ph arma, Novartis, UCB and Eli Lilly and reimbursement for attending or chairing a symposium from Janssen, Pfizer, Celgene and AbbVie. All funding is not personal but goes to the independent research fund of the department of dermatology of Radboudumc Nijmegen, the Netherlands.

ETHICAL APPROVAL

This study was conducted according to the ICH GCP guidelines and the principles of the Declaration of Helsinki. Data collection was performed in accordance with the Dutch Act on Implementation of the General Data Protection Regulation; in Dutch: ‘Uitvoeringswet AVG’. This study was exempted for the Medical Research Involving Human Subjects Act (WMO) by the Medical Ethical Committee Arnhem‐Nijmegen.

ETHICS STATEMENT

Consent was obtained from all participants that filled in the questionnaires. All data were pseudonymized.

Supporting information

Appendix S1

Appendix S2

van Riel CAM, Boehncke W‐H, Lambert JLW, Spuls PI, van der Schoot LS, van Ee I, et al. International consensus on dose reduction of biologics for patients with psoriasis: The DR. Delphi study. J Eur Acad Dermatol Venereol. 2026;40:1449–1459. 10.1111/jdv.70447

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.