Freezing-mediated formation of supraproteins using depletion forces

Hypothesis Long-acting formulations such as microparticles, injectable depots and implantable devices can realize spatiotemporally controlled delivery of protein drugs to extend their therapeutic in vivo half-lives. To efficiently encapsulate the protein drugs into such drug delivery systems, (sub)micron-sized protein particles are needed. The formation of micronized supraproteins can be induced through the synergistic combination of attractive depletion forces and freezing. The size of the supraproteins can be fine-tuned from submicron to several microns by adjusting the ice crystallization rate through the freeze-quench depth, which is set by the target temperature. Methods Supraprotein micron structures were prepared from protein solutions under various conditions in the presence and absence of nonadsorbing polyethylene glycol. Scanning electron microscopy and dynamic light scattering were employed to determine the sizes of the supraproteins and real-time total internal reflection fluorescent microscopy was used to follow the supraprotein formation during freezing. The protein secondary structure was measured before and after micronization by circular dichroism. A phase diagram of a protein-polyethylene glycol mixture was theoretically predicted to investigate whether the depletion interaction can elucidate the phase behavior. Findings Micronized protein supraparticles could be prepared in a controlled manner by rapid freeze-drying of aqueous mixtures of bovine serum albumin, horseradish peroxidase and lysozyme mixed with polyethylene glycol. Upon freezing, the temperature quench initiates a phase separation process which is reminiscent of spinodal decomposition. This demixing is subsequently arrested during droplet phase separation to form protein-rich microstructures. The final size of the generated protein microparticles is determined by a competition between phase separation and cooling rate, which can be controlled by target temperature. The experimental phase diagram of the aqueous protein-polyethylene glycol dispersion aligns with predictions from depletion theory for charged colloids and nonadsorbing polymers.

Origin of Anomalously Large Depletion Zones in Like-Charged Colloid-Polyelectrolyte Mixtures

Depletion zones in polyelectrolyte solutions in contact with like-charged flat surfaces are investigated. Using a coupled self-consistent field and Debye-Hückel approach, an explicit expression for the thickness δ of the depletion layer is derived. It is found that δ∼δ_{n}+cκ^{-1}, where δ_{n} is the depletion thickness at a neutral surface, c is a function of the electrostatic characteristics of the system, and κ^{-1} is the Debye length. It is argued that the theory still holds beyond the mean-field approximation, which is confirmed by quantitative agreement between our theoretical results and experiments.

Depletion interaction mediated by semiflexible polymers

We present a simple mean-field theory to describe the polymer-mediated depletion attraction between colloidal particles that accounts for the polymer's chain stiffness. We find that for fixed polymer radius of gyration and volume fraction, the strength of this attraction increases with increasing chain stiffness in both dilute and semidilute concentration regimes. In contrast, the range of attraction monotonically decreases with chain stiffness in the dilute regime, while it attains a maximum in the semidilute regime. The obtained analytical expressions for the depletion interaction were compared with numerical self-consistent field lattice computations and shown to be in quantitative agreement. From the interaction potential between two spheres, we calculated the second osmotic virial coefficient B₂, which appears to be a convex function of chain stiffness. A minimum of B₂ as a function of chain stiffness was observed both in the numerical self-consistent field computations and the analytical theory. These findings help explain the general observation that semiflexible polymers are more effective depletants than flexible polymers and give insight into the phase behavior of mixtures containing spherical colloids and semiflexible polymers.

POS1084 IMPACT OF PSORIASIS REMAINS IMPORTANT IN PSORIATIC ARTHRITIS PATIENTS WITH LOW MUSCULOSKELETAL DISEASE ACTIVITY

Background

Psoriatic arthritis (PsA) is a complex, chronic auto-immune disease that affects health-related Quality of Life (HRQoL). Earlier research showed that general HRQoL in PsA patients is mainly affected by musculoskeletal pain.1 However, psoriasis has also shown to impact HRQoL.2 Therefore, it is of value to know if HRQoL of PsA patients who reached musculoskeletal low disease activity can be further improved by additionally achieving remission of their psoriasis.

Objectives

The aim of this study was to assess HRQoL in patients with active psoriasis who reached musculoskeletal low disease activity one year after their diagnosis.

Methods

Data were collected from the Dutch south west Psoriatic Arthritis cohort. Musculoskeletal low disease activity (LDA) was defined as Disease Activity in Psoriatic Arthritis Low disease activity (DAPSA) ≤14 and active skin at baseline as Psoriasis Area and Severity Index (PASI) >0. Patients who reached DAPSA-LDA after one year were divided based on reaching psoriasis remission (PASI ≤1). General HRQoL, and dermatology-specific HRQoL were compared between both groups.

Results

We included 624 patients, of which 106 (17%) patients had no psoriasis and 518 (83%) had active psoriasis. After one year, 230 (44%) patients with active psoriasis at baseline reached DAPSA-LDA, of which 108 (47%) patients also achieved psoriasis remission. The group of patients with active psoriasis (n=122, 53%) contained significantly more men (63% vs. 48%) and scored lower on the 12-item Psoriatic Arthritis Impact of Disease questionnaire (p=0.012). This group also had significantly lower median (IQR) scores of the psychosocial subscale (1 [0-5]) and symptoms subscale (4 [2-5]) of the dermatology-specific Skindex-17 questionnaire. Clinically, this implies little impairment psychosocially and a few physical symptoms.

Evaluation of the absolute scores of the Skindex-17 subscales in this group showed that 31% of patients experienced moderate to high psychosocial impairment and 28% experienced a lot of symptoms (Figure 1).

Figure 1.

Clinical categories of Skindex-17 psychosocial and symptoms scores of patients with DAPSA-LDA and active psoriasis (PASI>1) one year after diagnosis (n=116)

Conclusion

In daily clinical practice approximately half of PsA patients who reached musculoskeletal low disease activity (DAPSA-LDA) one year after their diagnosis has not reached psoriasis remission. The majority of these patients has a good HRQoL. However, a proportion of them still experiences considerable skin burden. We therefore recommend rheumatologists to always assess and treat psoriasis in order to reduce skin burden, even in PsA patients who achieved musculoskeletal low disease activity.

References

[1]Wervers K, Luime JJ, Tchetverikov I, Gerards AH, Kok MR, Appels CWY, et al. Influence of Disease Manifestations on Health-related Quality of Life in Early Psoriatic Arthritis. J Rheumatol. 2018;45(11):1526-31.

[2]Kasiem FR, Kok MR, Luime JJ, Tchetverikov I, Wervers K, Korswagen LA, et al. The burden of psoriasis in patients with early psoriatic arthritis. Rheumatology (Oxford). 2021.

Acknowledgements

The work described in this article was financially supported by Janssen-Cilag B.V.

Disclosure of Interests

None declared

POS1054 PAIN AND DEPRESSION ARE ASSOCIATED WITH NON-RESPONSE TO METHOTREXATE IN PATIENTS WITH PSORIATIC ARTHRITIS

Background

Psoriatic arthritis (PsA) is a heterogeneous, immune-mediated inflammatory arthritis. Methotrexate (MTX) is the first-line treatment in PsA patients, despite diverse clinical phenotypes and highly varied responses(1). As yet, it is not possible to predict MTX treatment response. The identification of demographic, clinical and psychosocial factors associated with MTX non-response, would facilitate a paradigm shift from a ‘one-size-fits-all’ approach to a more personalized medicine strategy, based on individual patient characteristics.

Objectives

The aim of this study was to identify demographic, clinical and psychosocial factors associated with MTX non-response 3 months after MTX initiation in adult patients with PsA.

Methods

Newly diagnosed, adult PsA patients were recruited to the DEPAR (Dutch southwest Early Psoriatic Arthritis cohort) study. MTX non-response was defined as patients achieving <5/7 point of the Minimal Disease Activity (MDA) criteria after 3 months of MTX therapy. A logistic regression analysis was performed to identify demographic, clinical and psychosocial factors associated with MTX non-response. Demographic characteristics included age, sex, alcohol use, smoking (pack years) and body mass index (BMI). Clinical characteristics included duration of PsA symptoms, swollen and tender joint counts (66/68), Psoriasis Area and Severity Index (PASI) scores, presence of dactylitis and enthesitis scores (Leeds Enthesitis Index/Maastricht Ankylosing Spondylitis. [LEI_MASES]). Psychosocial variables included both subscales of the Hospital and Anxiety Depression Scale (HADS).

Results

Complete data of the variables of interest were available for 174/332 (52%) patients starting MTX monotherapy within the first year of diagnosis. Mean (SD) age was 53 (14) years and 88 patients (51%) were male. A total of 39 patients (22%) achieved MDA after 3 months of MTX therapy. Correlations between the variables and regression statistics are shown in Table 1. A significant correlation was seen between MTX non-response and enthesitis (OR 0.66, CI 0.47-0.94) and depression (OR 0.41, CI 0.25-0.66). Furthermore, the interaction of BMI with tender joint count (OR 0.95, CI 0.91-1.00) was found to be significantly correlated, whereas the independent variables were not.

Table 1.

Final model of the logistic regression analysis of methotrexate non-response 3 months after methotrexate initiation.

Independent variablesOdds Ratio95% CIDemographic variables BMI1.260.61-2.60 BMI31.001.00-1.00Clinical characteristics Tender joint count (68)3.160.94-10.57 Enthesitis (LEI/MASES)0.660.47-0.94 Psoriasis (PASI)1.110.99-1.25 BMI*Tender joint count (68)0.950.91-1.00Patient reported outcomes Depression (HADS)†0.410.25-0.66

Footnotes

Significant values in bold face

† Root transformed

Conclusion

Our results indicate that enthesitis, depression and the combination of a higher BMI with a tender joint count are all associated with MTX non-response 3 months after MTX initiation. Pain may be the common denominator preventing patients from achieving MDA.

References

[1]Gossec L, Baraliakos X, Kerschbaumer A, de Wit M, McInnes I, Dougados M, et al. EULAR recommendations for the management of psoriatic arthritis with pharmacological therapies: 2019 update. Ann Rheum Dis. 2020;79(6):700-12.

[2]den Braanker H, Wervers K, Mus AMC, Bangoer PS, Davelaar N, Luime J, et al. Achieving sustained minimal disease activity with methotrexate in early interleukin 23-driven early psoriatic arthritis. RMD Open. 2020;6(2).

Disclosure of Interests

None declared

AB0884 Disease outcomes in patients with psoriatic arthritis completing 12 months of apremilast treatment - Real-world data from the REWARD study

Background

Patients with moderately active psoriatic arthritis (PsA) and limited joint involvement have considerable disease burden1,2. Recent data shows these patients have a high likelihood of achieving treatment goals if treated with apremilast3. This is the first report of outcomes in patients with PsA who received apremilast for 12 months in Dutch clinical practice.

Objectives

We report disease outcomes, including the PsA Impact of Disease (PsAID) 12-item questionnaire, swollen joint count (SJC), tender joint count (TJC), dactylitis and enthesitis, among patients in the prospective, multicenter, observational REWARD study who completed 12 months of apremilast treatment.

Methods

The ongoing REWARD study enrolled patients who had initiated apremilast for the treatment of PsA in the Netherlands between 13 April 2017 and 24 March 2021, and includes up to 12 months follow-up1,4. We report interim data from patients with data available as of 16 September 2021. Baseline data are summarized separately for patients who discontinued apremilast before their month 12 study visit (stoppers) and patients still receiving apremilast at their month 12 visit (completers). Post baseline data are summarized for completers. Continuous data are summarized using mean and SD, categorical data are summarized using n and percent.

Results

98 patients were included in this interim analysis; 32 had completed 12 months of apremilast treatment (completers), 54 had discontinued apremilast before month 12 (stoppers), 12 were ongoing in the study. Compared with stoppers, completers were more likely to be biologic naïve and have dactylitis, and had lower BSA. All other baseline characteristics were similar (Table 1). Among completers, all PsAID domains improved after 3 months of apremilast treatment and these improvements were maintained through month 12 (Figure 1). Mean SJC and TJC decreased between baseline and month 12 (SJC, 4.2 and 1.0 at baseline and month 12, respectively; TJC, 7.1 and 3.3, respectively). The proportion of completers with SJC, TJC, enthesitis and dactylitis scores of 0 increased from baseline to month 12 (Figure 1B). The proportion of completers reporting at least one adverse event (AE) was comparable to the overall study population (14/32 [44%] and 48/98 [49%], respectively); the reported adverse events were similar to the known safety profile of apremilast.

Table 1.

Baseline characteristics

All=all patients included in this interim analysis; Completers= patients that received apremilast for 12 months; Stoppers= patients that stopped apremilast treatment prior to 12 months.

BMI=Body Mass Index, PsO=Psoriasis, BSA PsO= Body Surface Area Psoriasis, SJC=Swollen Joint Count, TJC=Tender Joint Count, PsAID=Psoriatic Arthritis Impact of Disease, VAS=Visual Analog Scale, CRP= C-reactive protein, cDAPSA=Clinical Disease Activity in Psoriatic Arthritis, Rem=Remission, Mod=Moderate, PsA= Psoriatic Arthritis

Figure 1.

(A) PSAID scores in completers and (B) percentage of completers with no swollen joints, no tender joints, no dactylitis and no enthesitis at baseline (BSL), month 3, 6 and 12 (M3, M6, M12).

Conclusion

In this interim analysis of the REWARD study, patients completing 12 months of apremilast treatment were more likely to be biologic naïve than patients who discontinued apremilast within 12 months of initiation, and had significant decreases in TJC, SJC, dactylitis and enthesis during apremilast treatment. Completed patients also reported decreased PsAID scores during apremilast treatment, indicating improvements in their quality of life.

References

[1]Jansen TL, et al. Ann Rheum Dis. 2019; 78:913 [abstract FRI0442]

[2]Wervers et al. J Rheumatol. 2018;45:1526.

[3]Mease PJ, et al. Arthritis Care Res. 2020; 72, 6, 814–821

[4]Bos R, et al. Ann Rheum Dis. 2021; 80:805 [POS1053]

Acknowledgements

Sylvia de Jong and Claire Desborough, Amgen employees, provided medical writing and editorial assistance.

Disclosure of Interests

Reinhard Bos Consultant of: AbbVie BV, Genzyme Europe, Grant/research support from: Galapagos, Tim Jansen Speakers bureau: Grunenthal, Sobi, Consultant of: AbbVie, Celgene Corporation, Grant/research support from: ReumaNederland, Olatec, Grunenthal, Ian Bridges Shareholder of: Amgen, Employee of: Amgen, Sylvia de Jong Shareholder of: Amgen, Employee of: Amgen, Novartis, Marijn Vis Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer, Grant/research support from: Novartis, Pfizer

POS1051 TO WHAT EXTENT ARE BASELINE CHARACTERISTICS IN BIOLOGIC-EXPERIENCED PATIENTS WITH PSORIATIC ARTHRITIS ASSOCIATED WITH ACHIEVEMENT OF MINIMAL DISEASE ACTIVITY AT WEEK 24 OF GUSELKUMAB TREATMENT: A POST HOC ANALYSIS OF THE PHASE IIIb COSMOS CLINICAL TRIAL

Background

Guselkumab (GUS) is a human monoclonal antibody targeting the interleukin-23p19-subunit. It has demonstrated efficacy at Week 24 in the Phase IIIb COSMOS clinical trial of patients with active psoriatic arthritis (PsA) and inadequate response or intolerance to one or two tumour necrosis factor inhibitors (TNFis).1

Objectives

The aim of this post hoc analysis was to identify predictors of minimal disease activity (MDA) with GUS at Week 24 in patients with active PsA and inadequate response or intolerance to one or two TNFis.

Methods

A multiple logistic regression analysis was performed to identify potential predictors of MDA with GUS at Week 24 in TNFi-refractory patients with PsA. Odds ratios, 95% confidence intervals and p-values were calculated. Baseline characteristics assessed as predictors included age, sex, body mass index (BMI), C-reactive protein (CRP), other medication use and disease duration. Clinical features included tender and swollen joint counts (TJC/SJC), affected joint location, dactylitis, enthesitis, spondylitis, Psoriasis Area and Severity Index (PASI) score and psoriasis (PsO) localisation (Figure 1). Missing data for MDA at Week 24 were imputed as non-response; missing baseline values were imputed for two patients.

Figure 1.

Odds ratios and 95% CIs for potential predictors of minimal disease activity response to guselkumab 100 mg every 8 weeks at Week 24 in patients with PsA and an inadequate response or intolerance to one or two prior TNF inhibitors.

BMI, body mass index; CI, confidence interval; CRP, C-reactive protein; csDMARD, conventional systemic disease-modifying anti-rheumatic drug; HAQ-DI, Health Assessment Questionnaire - Disability Index; MDA, minimal disease activity; PASI, Psoriasis Area and Severity Index; PsA, psoriatic arthritis; PsO, psoriasis; TNF, tumour necrosis factor.

N=187 for all clinical features and baseline characteristics. Negative predictors are indicated by bold text and positive predictors by italicisation (p<0.05).

Results

Of the 187 patients in this study, 54.6% were women and the mean disease duration was 8.3 years. The patients had a mean TJC 0–68 of 21.0, a mean SJC 0–66 of 10.3, a mean PASI score of 11.6 and a mean BMI of 28.9. Furthermore, 67.9% had enthesitis and 35.8% had dactylitis at baseline. One prior TNFi had been received by 88.2% of patients, and two received by 11.8%. At Week 24, 17.1% of patients (32/187) achieved MDA. Wrist involvement (p=0.031) and scalp PsO (p=0.049) were positive predictors of MDA. Women were significantly less likely to achieve MDA (p=0.036) than men; other negative predictors included involvement of shoulder or small joints of the hand, and hand/foot PsO (all p<0.05). Age, BMI, CRP, TJC/SJC, HAQ-DI, PASI, spondylitis, enthesitis, dactylitis, other medication use and number of prior TNFis were not predictive of MDA (Figure 1).

Conclusion

Baseline characteristics and clinical features may be positively (wrist involvement, scalp PsO) or negatively (female sex, involvement of shoulder or small joints of the hand, hand/foot PsO) associated with achieving MDA with GUS at Week 24 in a TNFi-refractory population. Though the low patient number limits the generalisability of this analysis, assessment of Week 48 data may further elucidate potential predictors of MDA after longer-term treatment.

References

[1]Coates C et al. Ann Rheum Dis 2021; 0: 1–11.

Disclosure of Interests

William Tillett Speakers bureau:, Consultant of:, Grant/research support from: William Tillett has received research grants and consulting or speaker fees from AbbVie, Amgen, Celgene, Eli Lilly, Janssen, MSD, Novartis, Pfizer and UCB., Sarah Ohrndorf Speakers bureau: Sarah Ohrndorf has received speaker fees or travel expense reimbursements from AbbVie, BMS, Janssen, Novartis and Pfizer., Julio Ramírez Speakers bureau:, Consultant of: Julio Ramírez has received consulting or speaker fees from AbbVie, Amgen, Eli Lilly, Janssen, Novartis and UCB., Marlies Neuhold Shareholder of: Johnson & Johnson., Employee of: Janssen, Robert Wapenaar Shareholder of: Johnson & Johnson., Employee of: Janssen, Elke Theander Shareholder of: Johnson & Johnson., Employee of: Janssen, Christine CONTRE Shareholder of: Johnson & Johnson., Employee of: Janssen, Mohamed Sharaf Shareholder of: Johnson & Johnson., Employee of: Janssen, May Shawi Shareholder of: Johnson & Johnson., Employee of: Janssen, Marijn Vis Speakers bureau:, Consultant of:, Grant/research support from: Marijn Vis has received research grants and consulting or speaker fees from AbbVie, Amgen, Eli Lilly, Janssen, Novartis, Pfizer, UCB and the Dutch Arthritis Foundation.

POS1055 IDENTIFICATION OF PsA PHENOTYPES WITH MACHINE LEARNING ANALYTICS USING DATA FROM A PHASE 3 CLINICAL TRIAL PROGRAMME OF GUSELKUMAB IN A BIO-NAÏVE PATIENT POPULATION

Background

Psoriatic arthritis (PsA) is typically described by its individual domains or clinical components.1,2

Objectives

This post hoc analysis aimed to identify hypothesis-free phenotype clusters according to patients’ clinical features and baseline (BL) characteristics with data from the Phase 3 DISCOVER-1 and -2 guselkumab (GUS) clinical trials.

Methods

Data from bio-naïve patients with PsA treated with GUS 100 mg every 4 or 8 weeks in DISCOVER-1 and -2 were retrospectively analysed. Non-negative matrix factorisation was used as an unsupervised machine learning technique to identify clusters of PsA phenotypes, with BL characteristics and clinical observations as input features, according to which clusters were described.

Results

Data from 661 patients were pooled and 8 distinct clusters of PsA phenotypes identified (Table 1). Cluster 1 was characterised by lower limb involvement and the lowest rates of severe skin involvement (Figure 1); Cluster 2 by high skin involvement, the lowest proportion of women and highest proportion of overweight patients (body mass index [BMI] 25–<30, 70%); and Cluster 3 by high burden of disease in the hand/wrist. In Cluster 4 all patients had dactylitis and ≥3% body surface area (BSA) psoriasis involvement and the second highest proportion of men. Cluster 5 had the highest BL enthesitis rate; large joint involvement was also common. Cluster 6 had a high level of small joint involvement in the hands/feet, but low mean dactylitis score; nail involvement and BL enthesitis were also common. In Cluster 7, all patients had axial involvement at BL, 49.4% had dactylitis, 69.9% had enthesitis and most had BSA ≥3% (Figure 1). Cluster 8 had limited joint involvement, extensive skin involvement and the highest proportion of obese patients (BMI >30, 67%). Minimal disease activity (MDA) response rates at Week (W)24 and W52 were highest in Cluster 2 and lowest in Cluster 5. Clusters 3 and 4 had low MDA response rates at W24, increasing at W52.

Table 1.

Baseline characteristics of PsA phenotype clusters.

Cluster 1Cluster 2Cluster 3Cluster 4Cluster 5Cluster 6Cluster 7Cluster 8Feet dominantMale, overweight, psoriasis burdenHand dominantDactylitis dominantEnthesitis and large jointsEnthesitis and small jointsAxial dominantFemale, obese, large jointsRandomised and treated patients, n791259538576083124Age, years45.8 (10.4)45.8 (13.2)48.9 (11.8)44.8 (12.3)43.6 (13.3)45.8 (11.6)43.8 (10.4)47.5 (11.1)Female %54.420.060.026.364.941.736.161.3BMI, kg/m229.3 (5.4)27.4 (3.6)29.3 (6.1)26.9 (4.6)28.6 (7.5)29.0 (6.2)28.4 (6.9)32.1 (6.5)CRP, mg/dL1.7 (1.8)1.7 (2.0)1.4 (2.3)2.5 (2.8)1.7 (1.9)1.7 (1.8)2.2 (3.1)1.5 (1.8)Disease duration, years5.0 (5.3)5.1 (4.8)5.8 (6.5)6.1 (5.5)6.8 (7.6)6.1 (5.6)4.7 (4.6)5.2 (6.7)SJC, 0–6613.2 (7.1)8.2 (3.8)15.0 (8.0)18.0 (10.1)10.1 (5.1)17.5 (11.8)9.0 (4.2)8.8 (3.9)TJC, 0–6823.4 (10.1)12.8 (5.9)26.0 (12.0)30.6 (15.3)23.2 (12.6)37.5 (18.6)14.6 (6.5)12.7 (5.2)BSA, %12.6 (19.4)20.7 (19.8)14.8 (19.5)29.7 (26.4)14.6 (21.6)14.5 (18.4)15.2 (19.4)14.4 (15.7)Dactylitis %48.130.442.1100.036.853.349.431.5Dactylitis score3.0 (4.8)1.4 (3.2)2.7 (4.8)27.5 (12.3)2.3 (5.2)3.9 (6.8)2.2 (2.9)1.3 (2.5)Enthesitis %70.949.658.981.696.573.369.945.2LEI score2.0 (1.7)1.0 (1.3)1.7 (1.8)2.9 (1.9)4.2 (1.6)2.7 (2.3)1.3 (1.2)1.0 (1.3)

Data shown are mean (standard deviation) or %. Bold font indicates differentiating features of individual clusters. BMI, body mass index; BSA, body surface area; CRP, C-reactive protein; LEI, Leeds Enthesitis Index; PsA, psoriatic arthritis; SJC, swollen joint count; TJC, tender joint count.

Conclusion

Unsupervised machine learning identified 8 clusters of PsA phenotypes with significant differences in demographic and clinical features, including patterns of domain involvement and MDA responses. These clusters differ in their initial vs. later responses to GUS.

References

[1]Coates C et al. Arthritis Rheumatol 2016; 68: 1060–1071.

[2]Gossec L et al. Ann Rheum Dis 2012; 71: 4–12.

Disclosure of Interests

Pascal Richette Speakers bureau:, Consultant of: Pascal Richette has received fees from AbbVie, Amgen, Celgene, Janssen, Lilly, MSD, Novartis, Pfizer and UCB., Marijn Vis Speakers bureau:, Consultant of:, Grant/research support from: Marijn Vis has received research grants, consulting or speaker fees from AbbVie, Amgen, Eli Lilly, Janssen, Novartis, Pfizer, UCB and the Dutch Arthritis Foundation., Sarah Ohrndorf Speakers bureau: Sarah Ohrndorf has received speaker fees or travel expense reimbursements from AbbVie, BMS, Janssen, Novartis and Pfizer., William Tillett Speakers bureau:, Consultant of:, Grant/research support from: William Tillett has received research grants, consulting or speaker fees from AbbVie, Amgen, Celgene, Eli Lilly, Janssen, MSD, Novartis, Pfizer and UCB., Marlies Neuhold Shareholder of: Johnson & Johnson, Employee of: Janssen, Michel van Speybroeck Shareholder of: Johnson & Johnson, Employee of: Janssen, Elke Theander Shareholder of: Johnson & Johnson, Employee of: Janssen, Wim Noel Shareholder of: Johnson & Johnson, Employee of: Janssen, May Shawi Shareholder of: Johnson & Johnson, Employee of: Janssen, Alexa Kollmeier Shareholder of: Johnson & Johnson, Employee of: Janssen, Alen Zabotti Speakers bureau: AbbVie, Amgen, Eli Lilly, Novartis and UCB, Grant/research support from: Novartis

OP0028 EARLY ACHIEVEMENT OF MINIMAL DISEASE ACTIVITY IN PSORIATIC ARTHRITIS IS ASSOCIATED WITH LONG-TERM IMPROVEMENTS IN QUALITY OF LIFE

Background

Minimal disease activity (MDA) is a treatment target in psoriatic arthritis (PsA) that takes both clinical manifestations (joints, skin and enthesis) and the patient perspective into account (1). In a previous study we have shown that achieving MDA in the first year is associated with better quality of life (QoL) regardless whether this was achieved early or late in the first year (2). However, the impact of achieving MDA within the first year on the long-term is lacking.

Objectives

To compare quality of life at 1, 2 and 3 years between PsA patients who achieve MDA in the first year and those who do not.

Methods

Newly diagnosed, DMARD naïve PsA patients with oligo- or polyarthritis and at least 3 years of follow-up, participating in the Dutch southwest Early PsA cohoRt (DEPAR) were included. In short the DEPAR is an observational cohort of newly diagnosed PsA (3). Study visits took place at 3, 6, 9, 12, 18, 24 and 36 months after diagnosis. Patients were categorized in three groups by achievement of MDA in the first year:

Sustained MDA, includes patients who were in MDA at both their 9- and 12-month visit;

Non-sustained MDA, includes patients who achieved MDA in the first year but did not sustain it at both 9- and 12-months;

No MDA, includes patients who did not achieve MDA in the first year.

To measure QoL at 1, 2 and 3 years the Short form-36 (SF-36) questionnaire was used. Descriptive statistics were used to compare QoL.

Results

We included 243 patients (51% male) of whom 113 (47%) were classified as sustained MDA, 64 (26%) as non-sustained MDA and 66 (27%) as no MDA. At baseline, patients had a mean age of 52.7 years and median symptom duration of 9.3 months. Patients in the no MDA group seemed to be older, were more often female and had a longer symptom duration (Table 1). QoL of sustained MDA patients was comparable to the general Dutch population (4) after 1, 2 and 3 years of follow-up. However, patients who did not achieve MDA in the first year had a lower QoL compared to the sustained MDA group and these differences persist in the years thereafter (Figure 1). The physical as well as the mental QoL domains were worse in the no MDA group compared to the other groups.

Table 1.

Baseline characteristics of patients categorized by MDA group

Sustained MDA (n=113)Non-sustained MDA (n=64)No MDA(n=66)Demographics Age (years)51.8 ± 1351.8 ± 1455.3 ± 13 Sex (male)69 (61)33 (52)21 (32) Symptom duration (months)8.5 (4-24)8.1 (3-28)12.9 (5-51)Disease activity Swollen joint count (66)3 (2-5)4 (1-6)4 (2-8) Tender joint count (68)3 (1-6)4 (2-8)8 (4-13) Psoriasis95 (84)58 (91)56 (85)   BSA in case of psoriasis (%)3 (2-4)3.3 (1-6.5)3 (1.5-6) Enthesitis29 (26)28 (44)38 (58)   LEI in case of enthesitis1 (1-2)2 (1-2)2 (1-4)HAQ0.38 (0.13-0.75)0.75 (0.5-1)1 (0.75-1.38)VAS global31 (15-56)46 (23-65)59 (50-77)VAS pain28 (12-52)50 (26-66)69 (53-80)

Results are shown as mean ± standard deviation, n (%) or median (interquartile range). BSA: Body Surface Area; LEI: Leeds Enthesitis Index; HAQ: Health Assessment Questionnaire; VAS: visual analogue scale.

Figure 1.

(A) 1 year, (B) 2 year and (C) 3 year quality of life scores, measured with the SF-36 domains, for MDA groups and compared with the general Dutch population norms (4), (D) percentage of patients who use biologicals over time per MDA group.

Over the years, treatment was intensified in all groups, with biologicals use after three years at 18%, 25% and 31% in the sustained MDA, non-sustained MDA and no MDA group, respectively.

Conclusion

Failure to achieve MDA in the first year after PsA diagnosis is associated with worse quality of life outcomes that persist over the years despite more intensified treatment.

References

[1]Coates LC et al. Ann Rheum Dis. 2010;69(1):48-53.

[2]Wervers et al. Arthritis Res Ther. 2019;21(1):25.

[3]Kasiem et al. Scand J Rheumatol. 2021;50(2):124-31.

[4]Aaronson et al. J Clin Epidemiol. 1998;51(11):1055-68.

Acknowledgements

This study was funded by UCB Pharma. UCB was involved in the development of the research question. UCB was not involved in the evaluation of the results or drafting of the abstract.

Disclosure of Interests

None declared.

The depletion thickness in solutions of semi-flexible polymers near colloidal surfaces: analytical approximations

We derive a simple, yet accurate approximate mean-field expression for the depletion thickness δ_sf of a solution of dilute semi-flexible polymers next to a hard surface. In the case of a hard wall this equation has the simple form δ_sf = δ₀[1 - tanh(p_sf/δ₀)], where p_sf accounts for the degree of flexibility and δ₀ is the depletion thickness in the case of fully flexible polymers. For fixed polymer coil size, increasing the chain stiffness leads to a decrease in the depletion thickness. The approach is also extended to include higher polymer concentrations in the semidilute regime. The analytical expressions are in quantitative agreement with numerical self-consistent field computations. A remarkable finding is that there is a maximum in the depletion thickness as a function of the chain stiffness in the semidilute concentration regime. This also means that depletion attractions between colloidal particles reach a maximum for a certain chain stiffness, which may have important implications for the phase stability of colloid-polymer mixtures. The derived equations could be useful for the description of interactions in- and phase stability of mixtures of colloids and semi-flexible polymers.

Effects of polymer nonideality on depletion-induced phase behaviour of colloidal disks and rods

Colloidal dispersions composed of either platelets or rods exhibit liquid crystalline phase behaviour that is strongly influenced by the addition of nonadsorbing polymers. In this work we examined how polymer segment-segment interactions affect this phase behaviour as compared to using either penetrable hard spheres (PHS) or ideal ('ghost') chains as depletants. We find that the simplified polymer description predicts the same phase diagram topologies as the more involved polymer descriptions. Therefore the PHS description is still adequate for qualitative predictions. For sufficiently large polymer sizes we find however that the precise polymer description significantly alters the locations of the phase coexistence regions. Especially the stability region of isotropic-isotropic coexistence is affected by the polymer interactions. To illustrate the quantitative effects some examples are presented.

Sex-specific differences and how to handle them in early psoriatic arthritis

Objectives

The prevalence of psoriatic arthritis (PsA) is the same in men and women; however, the latter experience a higher burden of disease and are affected more frequently by polyarthritis. Here, we performed an early PsA cohort analysis to assess sex-related differences in demographics, disease characteristics, and evolution over 1 year including applied treatment strategies.

Methods

Our study is embedded in the Dutch south-west Early Psoriatic Arthritis cohoRt. We described patient characteristics and treatment decisions. For the comparison across sexes and baseline and 1 year follow-up, appropriate tests depending on the distribution were used.

Results

Two hundred seventy-three men and 294 women with no significant differences in age and ethnicity were included. Women reported significantly longer duration of symptoms before diagnosis and significantly higher tender joint count, a higher disease activity, higher levels of pain, and lower functional capacity. Although minimal disease activity (MDA) rates increased over time for both sexes, MDA remained significantly more prevalent among men at 1 year (58.1% vs 35.7%, p < 0.00).

Initially, treatment strategies were similar in both sexes with methotrexate being the most frequently used drug during the first year. Women received methotrexate for a shorter period [196 (93–364) vs 306 (157–365), p < 0.00] and therefore received a lower cumulative dose compared to men. Retention time was shorter for all DMARDs, and women had a delayed start on b-DMARDs.

Conclusion

After 1 year of standard-of-care treatment, women did not surpass their baseline disadvantages. Despite the overall improvement, they still presented higher disease activity, higher levels of pain, and lower functional capacity score than men. The nature of these findings may advocate a need for sex specific adjustment of treatment strategies and evaluation in early PsA patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02680-y.

Multiphase Coexistences in Rod-Polymer Mixtures

Using recently derived analytical equations of state for hard rod dispersions, we predict the phase behavior of athermal rod-polymer mixtures with free volume theory. The rods are modeled as hard spherocylinders, while the nonadsorbing polymer chains are described as penetrable hard spheres. It is demonstrated that all of the different types of phase states that are stable for pure colloidal rod dispersions can coexist with any combination of these phases if polymers are added, depending on the concentrations, rod aspect ratio, and polymer-rod size ratio. This includes novel two-, three-, and four-phase coexistences and isostructural coexistences between dilute and concentrated phases of the same kind, even for the more ordered (liquid) crystal phases. This work provides insight into the conditions at which particular multiphase coexistences are expected for well-defined model colloidal rod-polymer mixtures. We provide a quantitative map detailing the various types of isostructural coexistences, which confirms an early qualitative hypothesis by Bolhuis et al. ( J. Chem. Phys. 107, 1997 1551).

Phase stability of colloidal spheres mixed with semiflexible supramolecular polymers

HYPOTHESIS

Mixtures of colloids and supramolecular polymers may exhibit stimuli-responsive phase behaviour. However, in theoretical descriptions of such systems, the polymers are commonly described either as flexible chains or as rigid rods, while in experimental systems supramolecular polymers usually fall in between these two limits. We expect the flexibility of the polymers to have a profound effect on the stimuli-responsive phase behaviour.

THEORY

We propose a general approach to predict the phase behaviour of colloidal hard spheres mixed with covalent or supramolecular polymers of arbitrary persistence length using free volume theory and an interpolation between flexible and rigid chains.

FINDINGS

The binodals are predicted to shift to lower monomer concentrations as the persistence length is increased, making the polymers more efficient depletants. The persistence length is therefore an additional degree of freedom for manipulating the phase behaviour of colloid-polymer mixtures. We show that by manipulating the persistence length of temperature responsive supramolecular polymers, a wide range of phase diagrams with various topologies can be obtained. For example, we find phase diagrams with a critical point but no triple point or displaying two triple points for temperature-sensitive supramolecular polymers mixed with hard spheres.

Phase separation in mixed suspensions of bacteria and nonadsorbing polymers

The shapes of bacteria can vary widely; they may, for instance, be spherical, rod-like, string-like, or curved. In general, bacilli are highly anisotropic. For research and (bio)technological purposes, it can be useful to concentrate bacteria, which is possible by adding nonadsorbing polymers. The induced phase separation originates from a polymer-mediated depletion interaction, first understood by Asakura and Oosawa. Here, it is shown that free volume theory (FVT) can semi-quantitatively describe the phase transitions observed when adding sodium polystyrene sulfonate polymers to E. coli bacteria [Schwarz-Linek et al., Soft Matter 6, 4540 (2010)] at high ionic strength. The E. coli bacteria are described as short, hard spherocylinders. FVT predicts that the phase transitions of the mixtures result from a fluid-ABC crystal solid phase coexistence of a hard spherocylinder-polymer mixture.

From a eutectic mixture to a deep eutectic system via anion selection: Glutaric acid + tetraethylammonium halides

In pursuit of understanding structure-property relationships for the melting point depression of binary eutectic mixtures, the influence of the anion on the solid-liquid (S-L) phase behavior was explored for mixtures of glutaric acid + tetraethylammonium chloride, bromide, and iodide. A detailed experimental evaluation of the S-L phase behavior revealed that the eutectic point is shifted toward lower temperatures and higher salt contents upon decreasing the ionic radius. The salt fusion properties were experimentally inaccessible owing to thermal decomposition. The data were inter- and extrapolated using various models for the Gibbs energy of mixing fitted to the glutaric-acid rich side only, which allowed for the assessment of the eutectic point. Fitting the experimental data to a two-parameter Redlich-Kister expansion with Flory entropy, the eutectic depth could be related to the ionic radius of the anion. The anion type, and in particular its size, can therefore be viewed as an important design parameter for the liquid window of other acid and salt-based deep eutectic solvents/systems.

POS0151 A PRACTICAL GUIDE FOR THE ASSESSMENT OF PSORIASIS BURDEN IN PATIENTS WITH PSORIATIC ARTHRITIS

Background:

Rheumatologists play an important role in the management of patients with Psoriatic Arthritis (PsA). With PsA being a multifaceted disease, it can be challenging to assess the impact of psoriatic skin symptoms, next to the musculoskeletal complaints. We have previously shown that a dermatology-specific Health-related Quality of Life (HRQoL) questionnaire provides insight into the burden of skin symptoms, in contrast to a general HRQoL questionnaire.1 When treating PsA patients, specific questions on skin symptoms are necessary in order to assess the burden of psoriasis.

Objectives:

To create a set of questions that can easily identify PsA patients with a high psoriasis burden in daily rheumatology clinical practice.

Methods:

Data from patients receiving usual care were used from the Dutch south west Psoriatic Arthritis (DEPAR) cohort, consisting of newly diagnosed PsA patients included between July 2013 and March 2020. The two dermatology-specific HRQoL questionnaires used were the Skindex-17 and Dermatology Life Quality Index (DLQI), both with a one-week recall period.

First, an exploratory principal component analysis (PCA) with varimax rotation was performed on both questionnaires combined, to identify underlying latent traits. Subsequently, items were dichotomized on their median frequencies. And a 2-parameter logistic (2PL) model was fitted for each latent trait. Item characteristic curves were plotted for each latent trait. Item selection took place based on the discrimination and difficulty of the items. Per latent trait, we selected 2 to 3 items distributed far apart across the latent trait. A flowchart was made with the selected questions.

Results:

In total, 413 patients with completed Skindex-17 and DLQI questionnaires at baseline were included. Mean (sd) age was 50.3 (13.4) years and median (IQR) Psoriasis Area and Severity Index (PASI) score 2 (0.5-4.2). The PCA gave the best fit with two underlying clusters of questions, namely psychosocial (n=20) questions and questions regarding physical symptoms (n=7). Three questions were selected to assess psychosocial impact and two for impact of physical symptoms (Figure 1). Questions should be asked in chronological order.

Figure 1.

Flowchart of questions assessing psoriasis burden.

Cluster 1: Psychosocial

The first question is if the patient was embarrassed by their skin condition. If answered with “never”, the patient experienced the lowest burden. When answered with “rarely/sometimes” or “often/always”, continue to the second question. Ask the patient if they tended to stay at home because of their skin condition. If answered with “never”, they experienced a higher burden. If answered with “rarely/sometimes” or “often/always”, continue to the last question. Ask the patient if their skin condition has prevented them from working or studying. If not, the patient experienced a higher burden and if answered with “yes”, they experienced the highest burden in this domain.

Cluster 2: Physical symptoms

First ask the patient how itchy, sore, painful or stinging their skin was. If they answer with “not at all”, they experienced the lowest burden. If answered with “a little/a lot/very much”, continue to the second question. Ask if their skin was irritated. If answered with “never/rarely/sometimes”, they experienced a higher burden. If answered with “often/always”, the patient experienced the highest burden in this domain.

Conclusion:

We have created a practical guide for rheumatologists to distinguish PsA patients with a high psoriasis burden from those with a lower burden. With a minimum of two and a maximum of five questions, both psychosocial burden of psoriasis and burden of physical symptoms can be easily identified in daily clinical practice.

References:

[1]Kasiem FR, Kok MR, Tchetverikov I, Wervers K, Hazes J, Luime J, et al. AB0786 Impact of psoriasis severity on Health-Related Quality of Life in early psoriatic arthritis: results from real world data, the DEPAR study. Annals of the Rheumatic Diseases. 2020;79:1691-2.

Disclosure of Interests:

None declared

POS1057 DISCONNECT BETWEEN TREATMENT SWITCHES AND DISEASE ACTIVITY STATE IN EARLY PSORIATIC ARTHRITIS

Background:

Receiving adequate treatment early in the disease course is one of the most important prognostic factors to achieve optimal disease outcome in most rheumatological conditions. Treat-to-target strategies and early step-up of treatment are important ingredients to accomplish this. While for Rheumatoid Arthritis this is common practice on accepted targets, for Psoriatic Arthritis (PsA) this is less outspoken practice. In PsA multiple domains must be taken into account and also there is a less established practice to use PsA specific targets, such as MDA, although this is associated with a better quality of life.[1,2] Whether this affects optimal disease outcome is not well described

Objectives:

To describe treatment strategies in newly diagnosed PsA with at least one synovitis and, treatment switches over time in those that not achieved MDA.

Methods:

For this study we used data from the DEPAR study between August 2013 and February 2019. The DEPAR study is a cohort that includes newly diagnosed PsA patients and follows them for up to 6 years. Patients are classified at baseline according to their prominent features: mono-, oligo-, polyarthritis, enthesitis, dactylitis or axial phenotype. For this study we used the data from the first 2 years for the patients with an articular phenotype. Methotrexate (MTX) and MTX plus another s-DMARD or GCs were addressed separately as they form the cornerstone of treatment in PsA. Next treatment was grouped in the usual drug classes: sDMARD (conventional), bDMARD and Glucocorticoids (GCs). Descriptive statistics were applied in STATA16 and Tableau 2020.3

Results:

Out of 620 patients, 478 patients had at least one swollen joint at baseline and were included in this analysis. 349 (73%) had data at 1 year and 267 (56%) at 2 years. Average age was 50.3 years(sd 14.1), and 50% was female. Half of the patients had oligo-arthritis, 30% poly-arthritis and 20% mono-arthritis. At baseline, clinical characteristics were 3.8 swollen joints (sd 4.9), 5.5 tender joints (sd 6.2), 3.1 PASI points (sd 3.7, skin), 0.8 entheseal points (LEI; sd 1.2) and 0.1 dacylitis count (basic count of digits; sd 0.6). Treatment was initiated with Monotherapy MTX in 51% of the patients, while 25% did not start any DMARD, 10% started a combination of s-DMARDs, 9% a single s-DMARD, 3% a b-DMARD and 2% GCs. This differed for the different phenotypes as shown in Table 1.

Minimal Disease Activity (MDA) was achieved by 32% after 3 months increasing to 58% at 24 months. Treatment switches in the non-MDA mono-, oligo- and polyarthritis groups are shown in Figure 1. In the patients not in MDA treatment was not switch in: 70% of patients with mono-arthritis, 50-66% with oligo-arthritis and 50% poly-arthritis. Similar observations were found when using the DAS28(<=3.2) or DAPSA(<14), both including only articular disease activity (data not shown).

Conclusion:

Achieving MDA is associated with a better quality of life, though it is not yet common practice to make treatment adjustments based on MDA. Of the newly diagnosed PsA patients not in MDA, more than half of the clinical evaluations did not result in a switch of medication.

References:

[1]Wervers, K, et al ART 2019

[2]Coates, L, et al. Lancet 2015

Figure 1.

Medication change in patients not in MDA at each timepoint (dark bars = change and light bars = no change)

Disclosure of Interests:

Jolanda Luime: None declared, Marc Kok Grant/research support from: Pfizer, Novartis, BMS, Abbvie, Ilja Tchetverikov: None declared, Marijn Vis Grant/research support from: Novartis, CICERO collaboration of rheumatologists: None declared.

POS1053 COMPARISON OF BASELINE CHARACTERISTICS BETWEEN PATIENTS CONTINUING OR DISCONTINUING APREMILAST AT TWELVE MONTHS IN THE REWARD STUDY (THE NETHERLANDS)

Background:

Previous analysis of the REWARD study reported that patients with limited joint involvement have a considerable burden of disease1. Recent data suggest that patients with moderately active psoriatic arthritis (PsA) and a limited joint involvement have a high likelihood of achieving treatment goals when treated with apremilast2. According to EULAR recommendations a PDE4 inhibitor may be considered in patients with mild disease and an inadequate response to at least one csDMARD, in whom neither a bDMARD nor a JAK inhibitor is appropriate and the value of apremilast may be found in treating patients with relatively mild disease (oligoarticular)3.

Objectives:

The objective of this prospective, multicentre, non-interventional study is to describe patient reported outcomes, effectiveness and real-life use of apremilast in patients with PsA. Patients will be followed up for a maximum of 12 months. This interim analysis compared the baseline characteristics and experience on apremilast for two subgroups of patients, those remaining on apremilast versus the ones that discontinued.

Methods:

In this interim analysis we included patients with data available at cut-off date of 03 November 2020. Patient enrollment and follow up of current subjects is ongoing. Descriptive statistics (n’s and percents for categorical data, means for continuous data) were used to summarize the baseline data by subgroup. Kaplan Meier plots are presented to show patients’ experience on apremilast by subgroup.

Results:

85 patients were included in the analysis. 30 patients have completed the study, 39 patients have discontinued and 16 are ongoing. At baseline 22 (26%) patients were biologic experienced and 62 (74%) were biologic naïve. Both groups had a comparable disease activity measured with clinical disease activity in psoriatic arthritis (cDAPSA) scores. Biologic experienced patients had a longer disease duration compared to biologic naïve patients (mean 9.7 vs 6.2 years). Inefficacy of previous medication was the main reason for starting apremilast in both subgroups. Overall, 86% (n=69) of patients were still receiving apremilast at month 3, 60% (n=46) at month 6, and 41% (n=26) at month 12 (Figure 1). Drug survival (length of time until discontinuation of apremilast) for biologic naïve patients was 93% at month 3, 73% at month 6 and 58% at month 12. Drug survival of biologic experienced patients was 67%, 20%, and 0% at months 3, 6, and 12, respectively. At baseline mean values of body mass index (BMI), swollen joint count (SJC), tender joint count (TJC), psoriatic arthritis impact of disease (PsAID) were comparable between both groups (Table 1). Reasons for discontinuation were mainly lack of efficacy (49%) and adverse events (44%). In this analysis the nature and frequency of adverse events is in line with the known profile of apremilast.

Conclusion:

In this interim analysis, patients who were biologic naïve had a better probability to remain on treatment than those who were biologic experienced. Baseline characteristics were similar between the two groups, apart from disease duration that was longer in the biologic experienced group. Best drug survival is achieved when apremilast is prescribed earlier in the PsA treatment course, before biologics and after csDMARDs, as per apremilast EU label.

References:

[1]Jansen TL, et al. Ann Rheum Dis. 2019;78:913 [abstract FRI0442]

[2]Mease PJ, et al. Arthritis Care Res 2020 72 6 814–821

[3]Gossec L, et al. Ann Rheum Dis 2020;79:700–712

Disclosure of Interests:

Reinhard Bos Consultant of: AbbVie BV, Genzyme Europe, Janssen-Cilag, Novartis, Pfizer, Grant/research support from: Galapagos, Tim Jansen Consultant of: AbbVie, Celgene Corporation – consultant, Speakers bureau: Grunenthal, Sobi – speakers bureau, Grant/research support from: ReumaNederland, Olatec, Grunenthal – grant/research support, Sylvia de Jong Shareholder of: Employee of Amgen Inc, Employee of: Employee of Amgen Inc, Antonio Castiglia Shareholder of: Employee of Amgen Inc, Employee of: Employee of Amgen Inc, Marijn Vis Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer, Grant/research support from: Novartis, Pfizer, AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer.

Repulsive and attractive depletion forces mediated by nonadsorbing polyelectrolytes in the Donnan limit

In mixtures of colloids and nonadsorbing polyelectrolytes, a Donnan potential arises across the region between surfaces that are depleted of the polyelectrolyte and the rest of the system. This Donnan potential tends to shift the polyelectrolyte density profile toward the colloidal surface and leads to the local accumulation of polyelectrolytes. We derive a zero-field theory for the disjoining pressure between two parallel flat plates. The polyelectrolyte is allowed to enter the confined interplate region at the cost of a conformational free energy penalty. The resulting disjoining pressure shows a crossover to a repulsive regime when the interplate separation gets smaller than the size of the polyelectrolyte chain, followed by an attractive part. We find a quantitative match between the model and self-consistent field computations that take into account the full Poisson-Boltzmann electrostatics.

Solvent Selectivity Governs the Emergence of Temperature Responsiveness in Block Copolymer Self-Assembly

In highly selective solvents, block copolymers (BCPs) form association colloids, while in solvents with poor selectivity, they exhibit a temperature-controlled (de)mixing behavior. Herein, it is shown that a temperature-responsive self-assembly behavior emerges in solvent mixtures of intermediate selectivity. A biocompatible poly-ethylene(oxide)-block-poly-ε-caprolactone (PEO-PCL) BCP is used as a model system. The polymer is dissolved in solvent mixtures containing water (a strongly selective solvent for PEO) and ethanol (a poorly selective solvent for PEO) to tune the solvency conditions. Using synchrotron X-ray scattering, cryogenic transmission electron microscopy, and scanning probe microscopy, it is shown that a rich temperature-responsive behavior can be achieved in certain solvent mixtures. Crystallization of the PCL block enriches the phase behavior of the BCP by promoting sphere-to-cylinder morphology transitions at low temperatures. Increasing the water fraction in the solvent causes a suppression of the sphere-to-cylinder morphology transition. These results open up the possibility to induce temperature-responsive properties on demand in a wide range of BCP systems.

Lessons learned from clinical phenotypes in early psoriatic arthritis: the real-world Dutch south west Early Psoriatic ARthritis study

Objective: This paper describes the baseline demographics, clinical characteristics, and patient-reported outcomes (PROs) according to clinical phenotype of patients with early psoriatic arthritis (PsA) for the purpose of creating a decision support system for daily clinical practice.Method: Patients with newly diagnosed PsA were included in the Dutch south west Early Psoriatic ARthritis (DEPAR) study. No classification criteria were applied, to ensure collection of real-world data on demographics, medication, clinical characteristics, and PROs. An IT infrastructure facilitated data collection.Results: We described 527 patients, categorized according to the clinical phenotype stated by the rheumatologist at the time of diagnosis, namely monoarthritis (15%), oligoarthritis (40%), polyarthritis (23%), enthesitis (10%), axial disease (2%), and dactylitis (10%). Overall psoriasis severity was mild and 83 patients (16%) had no psoriasis. Short-term sick leave (> 1 day per 4 weeks) was 17% and long-term sick leave (> 4 weeks) was 4%. The group with phenotype enthesitis reported the longest duration of complaints, had the highest fatigue scores, and contained the highest percentage of patients with a Hospital Anxiety and Depression Scale (HADS) anxiety score ≥ 8 and depression score ≥ 8.Conclusion: PsA patients presenting at outpatient clinics in the Netherlands had a mild degree of psoriasis, with impairment of quality of life and work productivity. Most patients presented with phenotype oligoarthritis. Those presenting with phenotype enthesitis more often reported scores suggestive of an anxiety or depression disorder and fatigue. It is important for attending rheumatologists to be aware of these differences when assessing patients with PsA.

Quantification of the Structure of Colloidal Gas-Liquid Interfaces

We have quantified the structure of the colloidal gas-liquid interface using synchrotron X-ray reflectivity measurements on a model colloid-polymer mixture. The interfacial width shows mean-field scaling with the colloid density difference, and the density profiles appear to be monotonic. Furthermore, our measurements allow us to distinguish between different theoretical polymer descriptions commonly used to model colloid-polymer mixtures. Our results highlight the importance of capturing the correct polymer physics in obtaining a quantitative theoretical description of the colloidal gas-liquid interface.

Defying the Gibbs Phase Rule: Evidence for an Entropy-Driven Quintuple Point in Colloid-Polymer Mixtures

Using a minimal algebraic model for the thermodynamics of binary rod-polymer mixtures, we provide evidence for a quintuple phase equilibrium; an observation that seems to be at odds with the Gibbs phase rule for two-component systems. Our model is based on equations of state for the relevant liquid crystal phases that are in quantitative agreement with computer simulations. We argue that the appearance of a quintuple equilibrium, involving an isotropic fluid, a nematic and smectic liquid crystal, and two solid phases, can be reconciled with a generalized Gibbs phase rule in which the two intrinsic length scales of the athermal colloid-polymer mixture act as additional field variables.

Design of Nonideal Eutectic Mixtures Based on Correlations with Molecular Properties

In this work, a statistical analysis was performed to reveal how the molecular properties are correlated with the nonideal behavior observed in eutectic mixtures. From this, a statistical model, combined with theory and experimental results, was developed to predict the nonideal behavior of a specific set of eutectic mixtures, consisting of quaternary ammonium bromides with dicarboxylic acids and polyols. The combination of this analysis and this model can be considered as a first step toward the a priori design of eutectic mixtures. The analysis performed is based on principal components. The descriptors used for this are molecular properties of the constituents of these mixtures. The molecular properties are a combination of experimental, theoretical, and computed properties. The analysis reveals that there are strong correlations between the nonideality of the mixtures and a measure of the acidity of the hydrogen bond donating protons, the displacement of the bromide anion, and the bulkiness of the quaternary ammonium salt. Our analysis highlights the design rules of deep eutectic systems (DES), enabling control over the extent of the liquid window. Our model enables prediction of the eutectic temperature for a range of related mixtures.

AB0784 COMPARABLE IMPACT AND BURDEN OF DISEASE OF PSORIATIC ARTHRITIS PATIENTS WITH LIMITED JOINT INVOLVEMENT VS. THOSE WITH MORE EXTENSIVE JOINT INVOLVEMENT: INTERIM RESULTS FROM THE REWARD STUDY, A PROSPECTIVE, MULTICENTER, REAL-WORLD STUDY IN PATIENTS TREATED WITH APREMILAST

Background:

Psoriatic arthritis (PsA) is associated with a high burden of disease and an increased risk of comorbidities. Recent data suggest that patients with moderate PsA benefit most from apremilast (APR) treatment.1Results from an earlier analysis of the REWARD study suggest that patients with limited joint involvement may benefit from APR treatment, with improvements in the perceived impact of disease.2Patients with limited joint involvement or comorbidities are underrepresented in randomised controlled trials; therefore, evidence from real-world patient cohorts is needed to assess and compare the impact and burden of disease on patients with limited vs. extensive joints who may also have comorbidities.

Objectives:

To compare the burden of disease and comorbidities in patients with PsA who have limited joint involvement with patients with PsA who have extensive joint involvement.

Methods:

The prospective, multicenter, observational REWARD study assessed the impact of using the Psoriatic Arthritis Impact of Disease (PsAID) questionnaire (score range: 0-10), presence of domains of PsA (enthesitis, dactylitis, skin psoriasis, nail psoriasis, axial involvement), and ongoing or history of comorbidities of interest on PsA patients considered for apremilast treatment in The Netherlands. This interim analysis compared results in patients with limited joint involvement (swollen joint count [SJC] ≤4) vs. more extensive joint involvement (SJC >4).

Results:

Currently, 77 patients have been included in the analysis (SJC ≤4: n=53; SJC >4: n=24) (Table 1). Mean baseline PsAID scores were 4.4 vs. 4.8 for the SJC ≤4 vs. SJC >4 groups (Figure 1). The proportions of patients who were not in the PsAID-defined Patient Acceptable Symptom State (PASS) were 58.7% for the SJC ≤4 group and 62.5% for the SJC >4 group. Mean pain visual analog scale (VAS) scores (0-100 mm) were 45.9 vs. 53.4 for the SJC ≤4 group vs. for the SJC >4 group. Mean scores for the individual PsAID domains for the SJC ≤4 vs. SJC >4 groups were generally comparable (Figure 2). Presence of specific manifestations of PsA for patients in the SJC ≤4 group vs. the SJC >4 group, respectively, were: moderate to severe psoriasis (psoriasis-involved body surface area [BSA] >3: 31.4% vs. 21.7%), nail psoriasis (45.3% vs. 41.7%), enthesitis (Leeds Enthesitis Index >0: 43.4% vs. 45.8%), dactylitis (18.9% vs. 33.3%), and axial involvement (3.8% vs 8.3%). Comorbidities in ≥5% of either group (SJC ≤4 vs. SJC >4) included hypertension (30.2% vs. 37.5%), hypercholesterolemia (13.2% vs. 16.7%), uveitis (1.9% vs. 8.3%), malignancy (0.0% vs. 8.3%), heart failure (5.7% vs. 8.3%), and depression (5.7 vs. 4.2%).

Table 1.

Patient Characteristics

DemographicsSJC ≤4n=53SJC >4n=24Age, mean53.154.4Female, %46.266.7Body mass index, mean, kg/m228.628.7PsA CharacteristicsSJC, mean1.210.2TJC, mean4.313.7PsAID, mean4.44.8Pain VAS, mean45.953.4Moderate to severe psoriasis (BSA >3), %31.421.7Dactylitis, %18.933.3Enthesitis, %43.445.8Nail psoriasis, %45.341.7Axial spondyloarthritis, %3.88.3ComorbiditiesHypertension, %30.237.5Hypercholesteremia, %13.216.7Uveitis, %1.98.3Malignancy, %0.08.3Heart failure, %5.78.3Depression, %5.74.2

Conclusion:

In this real-world study, no strong associations between SJC and patient-reported impact of disease or pain were observed. Similar to patients with more extensive joints involvement, patients with limited joint involvement had an associated substantial burden of disease, with more than half not achieving PsAID PASS.

References:

[1]Mease PJ, et al. Arthritis Care Res (Hoboken). 2020 Jan 7. Epub. 2. Jansen TL, et al. Ann Rheum Dis. 2019;78:913. Abstract FRI0442.

Disclosure of Interests:

Tim Jansen Grant/research support from: Olatec, Grunenthal – grant/research support, Consultant of: AbbVie, Celgene Corporation – consultant, Speakers bureau: Grunenthal, Sobi – speakers bureau, Arie Van Vliet Employee of: Amgen Inc. – employment; Celgene – employment at the time of study conduct, Marijn Vis Grant/research support from: Novartis, Pfizer – grant/research support, Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer – consultant

Algebraic equations of state for the liquid crystalline phase behavior of hard rods

Based on simplifications of previous numerical calculations [H. Graf and H. Löwen, Phys. Rev. E 59, 1932 (1999)1063-651X10.1103/PhysRevE.59.1932], we propose algebraic free energy expressions for the smectic-A liquid crystal phase and the crystal phases of hard spherocylinders. Quantitative agreement with simulations is found for the resulting equations of state. The free energy expressions can be used to straightforwardly compute the full phase behavior for all aspect ratios and to provide a suitable benchmark for exploring how attractive interrod interactions mediate the phase stability through perturbation approaches such as free-volume or van der Waals theory.

SAT0442 EVOLVEMENT OF SWOLLEN JOINTS IN THE FIRST YEAR OF EARLY PSORIATIC OLIGOARTHRITIS

Background:

Oligoarthritis and polyarthritis are the predominant phenotypes in PsA. Previous we have shown that patients with oligoarthritis suffer a similar loss in quality of life as polyarthritis patients.1Although oligoarthritis is one of the most prevalent form, ample data is available on this phenotype.2-5

Objectives:

To evaluate the evolution of swollen joint count over the first year since diagnosis and to assess baseline difference in those groups that evolved differently over time.

Methods:

Our study is embedded in the Dutch south-west Early Psoriatic Arthritis (DEPAR) prospective cohort study. We described patient characteristics using simple descriptive analysis techniques. For the comparison across groups univariable multinomial logistic regression was used in STATA15. Oligoarticular disease was defined as 2, 3 or 4 swollen joints,

Results:

175 patients had a complete 12-month evaluation as of February 2019 (80% of all included patients with oligoarthritis). Baseline characteristics are shown in table 1. In total 63 percent of the patients (111/175) had resolution of swollen joints at 1 year. (figure 1). Over the first year, 27 patients had consistently no swollen joints since their 3 month evaluation, 26 had no swollen joint from 6 months and 12 from 9 months and 11 at 12 months. 65 of the 175 (37%) had inconsistently no swollen joints (intermittent) during the first year. In 8% of the patients values were missing to determine to which group they belonged. Univariable multinomial logistic regression of baseline characteristics showed that the group that had resolution of swollen joints ‘early’ (within 6 months) compared to (i) the group that ‘never’ had resolution differed in having fewer tender joints; (ii) the group having ‘late’ resolution of swollen joints (after 6 months) showed little difference and;(iii) the ‘intermittent’ group varied in smoking status, fatigue, being female and age. Multivariable analysis may reveal other patterns, but requires a larger sample than that currently available.

Table 1.

Baseline characteristics of oligo arthritis patients with complete follow-up at 1 year.

n=175sex (% female)45%age51 (39-61)symptom duration (months)10.0BMI28 (24-32)current smoking23%paid employement70%(n=136)tender joint count3.0 (2.0-7.0)PASI2.0 (0.4-4.5)entheses44%dactylitis9%VASglobal42 (21-65)VASpain49 (25-68)HAQ0.63 (0.25-1.13)fatigue (BRAF)18 (10-30)Figure 1.

Evolution of swollen joint count in psoriatic oligo arthritis (n=175) over time expressed in a binary swollen joint count (yes: 0 / no: sjc!==0; mv= missing value),

Conclusion:

In our set of real world data, about one third of the PsA patients with oligoarticular disease had no resolution of swollen joints at 1 year. About half of these patient had consistently inflamed joints over time. Another third of the PsA patients had intermittently inflamed joints. At baseline these groups seems comparable in clinical presentation, demographics and PROMs, although some variation existed between early versus never and early versus intermittent resolution of swollen joints. Both indices provide room for improvement in the management of oligoarticular disease in PsA.

References:

[1]Wervers K et al. 2018 Nov;45(11):1526-1531

[2]Jones SM, et al. Br J Rheumatol. 1994;33(9):834-9

[3]Dönmez S, et al Clin Rheumatol. 2015;34(6):1091-6

[4]Iannone F, et al Scand J Rheumatol. 2015;44(3):192-9

[5]Kruithof E, et al Arthritis Res Ther. 2005;7(3):R569-80

Disclosure of Interests:

Marijn Vis Grant/research support from: Novartis, Pfizer – grant/research support, Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer – consultant, Kok Marc Grant/research support from: Novartis, Pfizer, Celgene, Lilly, UCB, Consultant of: Novartis, Celgene, Speakers bureau: Celgene, Ilja Tchetverikov: None declared, Johanna Hazes: None declared, Jolanda Luime: None declared

AB0786 IMPACT OF PSORIASIS SEVERITY ON HEALTH-RELATED QUALITY OF LIFE IN EARLY PSORIATIC ARTHRITIS: RESULTS FROM REAL WORLD DATA, THE DEPAR STUDY

Background:

Psoriasis is an important feature of psoriatic arthritis (PsA). Psoriasis itself is known to have a significant impact on Health-related Quality of life (HRQoL)1, however its role within PsA is less well understood. In daily practice, assessment of psoriasis may not always be a priority for rheumatologists, having been trained to focus on articular involvement. In order to assess whether psoriasis deserves more attention from rheumatologists, the aim of this study is to evaluate the influence of psoriasis on HRQoL in early PsA patients.

Objectives:

To describe the evolution of psoriasis severity during the first year of follow up in patients with early PsA and to evaluate the impact of psoriasis severity on HRQoL.

Methods:

Real world data were used from the Dutch south west Psoriatic Arthritis cohort (DEPAR) study, consisting of newly diagnosed PsA patients included between July 2013 and February 2019. Psoriasis severity was assessed using the Psoriasis Area and Severity Index (PASI) and categorized in: no psoriasis (PASI 0), mild psoriasis (PASI<7), moderate psoriasis (PASI 7-12) and severe psoriasis (PASI>12). Musculoskeletal disease severity was measured with the Disease Activity in PSoriatic Arthritis (DAPSA) score as contrast for psoriasis severity. DAPSA was categorized in: remission (REM[DAPSA≤4]), low disease activity (LDA[DAPSA≤14]), moderate disease activity (MDA[DAPSA≤28]) and high disease activity (HDA[DAPSA>28]).2

General HRQoL was assesed with the Short-Form 36 (SF-36[Physical component scale and Mental component scale]). Skin-specific HRQoL was measured with the Skindex-17 (psychosocial scale and symptoms scale).

Results:

In total, 435 patients were included. Mean (sd) age was 49.7 (13.4) years and 53% (n=229) was male. Psoriasis severity does not fluctuate much over the course of the first year and the majority of patients had mild psoriasis (Figure 1). HRQoL worsened with increasing psoriasis severity, when measured by the Skindex17. This reduction in HRQoL was not seen when measured with the SF-36 (Figure 2).

Figure 1.

Psoriasis severity categories during the first year of follow up. No psoriasis (PASI 0), mild psoriasis (PASI<7), moderate psoriasis (PASI 7-12) and severe psoriasis (PASI>12).

Figure 2.

A, B: Median Skindex17 psychosocial score and symptoms score per psoriasis severity category and DAPSA category at baseline. C,D: Mean SF36 Physical component scale (PCS) score and Mental component scale (MCS) score per psoriasis severity category and DAPSA category at baseline. No psoriasis (PASI 0), mild psoriasis (PASI<7), moderate psoriasis (PASI 7-12) and severe psoriasis (PASI>12). REM (DAPSA<4), LDA (DAPSA<14), MDA (DAPSA<28) and HDA (DAPSA>28)

Conclusion:

In early PsA patients, psoriasis severity is mostly mild, but considerably impacts HRQoL when measured using a skin specific questionnaire. For optimal management of PsA patients, we therefore recommend rheumatologists to additionally acquire information on the degree of psoriatic involvement. In our opinion, this information is valuable for the adequate assessment of HRQoL.

References:

[1]Strober B, Greenberg JD, Karki C, Mason M, Guo N, Hur P, et al. Impact of psoriasis severity on patient-reported clinical symptoms, health-related quality of life and work productivity among US patients: real-world data from the Corrona Psoriasis Registry. BMJ Open. 2019;9(4):e027535.

[2]Schoels MM, Aletaha D, Alasti F, Smolen JS. Disease activity in psoriatic arthritis (PsA): defining remission and treatment success using the DAPSA score. Ann Rheum Dis. 2016;75(5):811-8.

Disclosure of Interests:

Fazira R. Kasiem: None declared, Marc R Kok Grant/research support from: BMS and Novartis, Consultant of: Novartis and Galapagos, Ilja Tchetverikov: None declared, Kim Wervers: None declared, Johanna Hazes: None declared, Jolanda Luime: None declared, Marijn Vis Grant/research support from: Novartis, Pfizer – grant/research support, Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer – consultant

OP0057 SEX SPECIFIC DIFFERENCES IN EARLY PSORIATIC ARTHRITIS

Background:

Although the prevalence of Psoriatic Arthritis (PsA) is the same in men and women, women experience a higher burden of disease (pain, disability, fatigue) (1).The persistent belief that women tend to over-report their symptoms compared to men may also contribute to under or delayed diagnosis in women. The clinical pattern of PsA also differs, with men presenting more commonly with peripheral and axial joint damage and women being affected more frequently by polyarthritis (2). Furthermore, most disease activity measures contain pain and quality of life measurement metrics that may perform differently by sex. As a result, this may affect the clinician’s perception of disease severity, influence management decisions and subsequently introduce sex bias in prescribing.

Objectives:

To assess sex-related differences in baseline demographics, disease characteristics and evolution over 1 year in patients with newly diagnosed PsA.

Methods:

Our study is embedded in the Dutch south-west Early Psoriatic Arthritis prospective cohort study. We described patient characteristics using simple descriptive analysis techniques. For the comparison across sexes and baseline and 1 year follow up, appropriate tests depending on the distribution were used.

Results:

273 men and 294 women with no significant differences in age and ethnicity were included. Women reported significantly longer duration of symptoms before diagnosis and significantly fewer of them were in paid employment at baseline. Oligoarthritis was the most common pattern of arthritis in both sexes. Polyarthritis and enthesitis were more prevalent in women who also presented at baseline a significantly higher tender joint count (Fig.1) than men but no difference in swollen joint count.

Figure 1.

Longitudinal evolution of TJC68, Pain, VAS global, BRAF for men and women in the first year of PsA.

All composite indices (CPDAI, DAPSA, GRACE, MDA, Psoriatic ArthritiS Disease Activity Score) showed significantly worse results in women at baseline. Women also suffered more frequently from comorbid medical conditions, fatigue and anxiety, and reported more severe limitations in function and worse quality of life.

At 12 months women, despite the improvement they made, reported significantly higher levels of pain compared to men. Although MDA rates increase over time for both sexes,(Fig.2), it remained significantly more prevalent among men (19.0% vs 11.1% at inclusion,p<0.05, and 58.1% vs 35.7%,p<0.00, at T12). DAPSA was significantly higher in women at both timepoints and a significantly higher percentage of men presented remission according to DAPSA score at 12 months.

Figure 2.

Longitudinal evolution of composite measures for men and women in the first year of PsA.

Conclusion:

After 1 year of follow-up women didn’t surpass their baseline disadvantages and despite the improvement, they still present higher disease activity, more pain and lower functional capacity than men. The nature of these findings may advocate a need for sex specific adjustment of treatment strategies and evaluation in psoriatic arthritis as sex-related difference in outcome persisted over time.

References:

[1]Eder L, Thavaneswaran A, Chandran V, Gladman DD. Gender difference in disease expression, radiographic damage and disability among patients with psoriatic arthritis. Annals of the rheumatic diseases. 2013;72(4):578-82.

[2]Orbai AM, Perin J, Gorlier C, Coates LC, Kiltz U, Leung YY, et al. Determinants of Patient-Reported Psoriatic Arthritis Impact of Disease: An Analysis of the Association with Gender in 458 Patients from 14 Countries. Arthritis care & research. 2019.

Disclosure of Interests:

Evangelia Passia: None declared, Marijn Vis Grant/research support from: Novartis, Pfizer – grant/research support, Consultant of: AbbVie, Celgene Corporation, Eli Lilly, Novartis, Pfizer – consultant, Laura C Coates: None declared, Anushka Soni Grant/research support from: Oxford-UCB prize fellowship, Speakers bureau: Janssen and Abbvie, Ilja Tchetverikov: None declared, Andreas Gerards: None declared, Lindy-Anne Korswagen: None declared, Marc R Kok Grant/research support from: BMS and Novartis, Consultant of: Novartis and Galapagos, Wiebo van der Graaff: None declared, Josien Veris-van Dieren: None declared, Natasja Denissen: None declared, F. Fodili: None declared, M. Starmans: None declared, Yvonne Goekoop-Ruiterman: None declared, M. van Oosterhout: None declared, Jolanda Luime: None declared

Oil-in-water emulsions based on hydrophobic eutectic systems

We demonstrate that oil-in-water emulsions can be prepared from hydrophobic eutectic systems (ES). Light microscopy and dynamic light scattering show that droplets are formed and zeta potential measurements indicate sufficient stability against coalescence. We investigate whether Ostwald ripening occurs in these ES-in-water emulsions by following the droplet growth over time and comparing it with an emulsion comprising decane in water. At first sight, the Ostwald ripening rate of the ES-in-water emulsion is expected to be orders of magnitude larger than the ripening of the decane-in-water emulsion due to a much higher solubility of the dispersed phase. However, experimentally we find that the ES-in-water emulsion actually grows a factor of two slower than the decane-in-water emulsion. We attribute this to the two-component nature of the ES, since the growth rate is mainly set by the least-soluble component of the ES. Thus, ESs offer the advantage of creating liquid emulsions of solid components, while setting the emulsion stability through their composition.

Experimental Evidence for Algebraic Double-Layer Forces

According to conventional wisdom, electric double-layer forces normally decay exponentially with separation distance. Here, we present experimental evidence of algebraically decaying double-layer interactions. We show that algebraic interactions arise in both strongly overlapping as well as counterion-only regimes, albeit the evidence is less clear for the former regime. In both of these cases, the disjoining pressure profile assumes an inverse square distance dependence. At small separation distances, another algebraic regime is recovered. In this regime, the pressure decays as the inverse of separation distance.

Activity modelling of the solid–liquid equilibrium of deep eutectic solvents

Compared to conventional solvents used in the chemical industry, deep eutectic solvents (DESs) are considered as promising potentially sustainable solvents. DESs are binary mixtures and the resulting liquid mixture is characterized by a large melting point depression with respect to the melting temperatures of its constituents. The relative melting point depression becomes larger as the two components have stronger attractive interactions, resulting in non-ideal behavior. The compositional range over which such binary mixtures are liquids is set by the location of the solid–liquid phase boundary. Here we present experimental phase diagrams of various recent and new DESs that vary in the degree of non-ideality. We investigate whether thermodynamic models are able to describe the solid–liquid equilibria and focus on relating the parameters of these models to the non-ideal behavior, including asymmetric behavior of the activity coefficients. It is shown that the orthogonal Redlich–Kister-like polynomial (OP) expansion, including an additional first order term, provides an accurate description. This theory can be considered as an extension of regular solution theory and enables physical interpretation of the fit parameters.

Interactions between amphoteric surfaces with strongly overlapping double layers

The entropic repulsion between strongly overlapping electrical double-layers from two parallel amphoteric plates is described via the Donnan equilibrium in the limit of zero electric field. The plates feature charge-regulation and the inter-plate solution is in equilibrium with a reservoir of a monovalent electrolyte solution. A finite electric potential and disjoining pressure is found at contact between the plates, due to a complete discharging of the plates. For low potentials, the decay of potential and pressure is fully governed by a characteristic length scale and the contact potential. Additionally, for large separations we find a universal inverse square decay of disjoining pressure, irrespective of the contact potential. The results of the Donnan theory show quantitative agreement with self-consistent field computations that solve the full Poisson equation.

Interfacial Tension of Phase-Separated Polydisperse Mixed Polymer Solutions

Aqueous two-phase systems provide oil-free alternatives in the formulation of emulsions in food and other applications. Theoretical interpretation of measurements on such systems, however, is complicated by the high polydispersity of the polymers. Here, phase diagrams of demixing and interfacial tensions are determined for aqueous solutions of two large polymers present in a mass ratio of 1:1, dextran (70 kDa) and nongelling gelatin (100 kDa), with or without further addition of smaller dextran molecules (20 kDa). Both in experiments and in calculations from Scheutjens-Fleer self-consistent field lattice theory, we find that small polymers decrease the interfacial tension at equal tie-line length in the phase diagram. After identifying the partial contributions of all chemical components to the interfacial tension, we conclude that excess water at the interface is partially displaced by small polymer molecules. An interpretation in terms of the Gibbs adsorption equation provides an instructive way to describe effects of polydispersity on the interfacial tension of demixed polymer solutions.

Modification of a sonographic enthesitis score to differentiate between psoriatic arthritis and young healthy volunteers

OBJECTIVES

We aimed to describe sonographic structural and inflammatory changes in entheses of patients with recently diagnosed psoriatic arthritis (PsA), patients with established PsA, and young healthy volunteers, and to investigate whether the MAdrid Sonographic Enthesitis Index (MASEI) enables us to distinguish these groups in an extreme comparison.

METHOD

New and established PsA patients and healthy volunteers (aged 20-30 years) were recruited. The triceps, quadriceps, patellar, Achilles and elbow extensor tendon insertion, and plantar fascia entheses were investigated sonographically for structural changes, erosions, calcifications, increased thickness, bursitis, and power Doppler (PD) signal according to the MASEI.

RESULTS

The study included 25 new and 25 established PsA patients, and 25 healthy volunteers. Increased thickness and PD signal in knee entheses were common for patients and healthy volunteers, while changes at other locations predominantly occurred in patients only. PD was recoded (1, one spot; 1.5, two or three spots; 2, confluent signal; 3, severe confluent signal) and thickness of knee entheses excluded. This resulted in different modified MASEI scores between PsA patients and young healthy controls: median (interquartile range) modified MASEI of 13 (10-22.5) in new PsA, 13.5 (9.5-18) in established PsA, and 3 (1-8.5) in healthy volunteers (p = 0.002).

CONCLUSIONS

Structural ultrasound changes and PD in entheses are common in both new and established PsA and healthy controls. MASEI score did not differentiate PsA patients from young healthy volunteers. After recoding of PD severity and excluding thickness of knee entheses, marked differences between PsA patients and healthy controls were observed.

Quantification of the liquid window of deep eutectic solvents

The non-ideality of the eutectic phase diagram is quantified using a single interaction parameter that could be determined directly from the experimental eutectic temperature of the mixture.

Polyelectrolytes adsorbed at water–water interfaces

Interfacial adsorption of polyelectrolytes provides a new strategy for the stabilization of water-in-water emulsions formed by incompatible polymers.

Water-in-Water Emulsions Stabilized by Nanoplates

Ultrathin plate-like colloidal particles are effective candidates for Pickering stabilization of water-in-water emulsions, a stabilization that is complicated by the thickness and ultralow tension of the water-water interface. Plate-like particles have the advantage of blocking much of the interface while simultaneously having a low mass. Additionally, the amount of blocked interface is practically independent of the equilibrium contact angle θ at which the water-water interface contacts the nanoplates. As a result, the adsorption of nanoplates is stronger than for spheres with the same maximal cross section, except if θ = 90°.

Decreased Interfacial Tension of Demixed Aqueous Polymer Solutions due to Charge

Electric charge at the water-water interface of demixed solutions of neutral polymer and polyelectrolyte decreases the already ultralow interfacial tension. This is demonstrated in experiments on aqueous mixtures of dextran (neutral) and nongelling fish gelatin (charged). Upon phase separation, electric charge and a potential difference develop spontaneously at the interface, decreasing the interfacial tension purely electrostatically in a way that can be accounted for quantitatively by Poisson-Boltzmann theory. Interfacial tension is a key property when it comes to manipulating the water-water interface, for instance to create novel water-in-water emulsions.