Population Pharmacokinetics of Adalimumab in Juvenile Idiopathic Arthritis Patients: A Retrospective Cohort Study Using Clinical Care Data.

BACKGROUND AND OBJECTIVE: Juvenile idiopathic arthritis (JIA) is a chronic autoimmune disorder that primarily affects the joints in children. Notably, it is known to co-occur with uveitis. Adalimumab, a monoclonal anti-TNF antibody, is effective in treating both conditions. A deeper understanding of the pharmacokinetics (PK) of adalimumab in JIA is crucial to advance in more personalized treatment approaches. The objective of this study is to evaluate the population PK profile of adalimumab in JIA and to explain causes for its variability. MATERIALS AND METHODS: Adalimumab and antidrug antibody concentrations were retrospectively retrieved from the charts of patients with JIA. Initially, five literature-based population PK models of adalimumab were evaluated to assess their ability to describe the observed concentration-time profiles in the JIA cohort. These models included one specifically for the pediatric Crohn's disease population and four derived from studies in adult populations in healthy subjects and rheumatoid arthritis patients. Subsequently, a novel population PK model tailored to the JIA population was developed using NONMEM software. Monte Carlo simulations were then conducted utilizing the final PK model to visualize the concentration-time profile of adalimumab in patients with JIA and the impact of covariates. RESULTS: A cohort of 50 patients with JIA with 78 available adalimumab samples was assessed. The mean age was 11.8 ± 3.9 years, with a median body weight of 49 kg (interquartile range 29.4-59.8 kg). All literature models adequately described the concentration-time profiles in JIA. The best model, which was developed in patients with rheumatoid arthritis during the maintenance phase of treatment, served as a basis for estimating clearance in JIA, resulting in a value of 0.37 L per day per 70 kg. Patient body weight, antidrug antibodies, methotrexate use, CRP level, and comorbidity of uveitis were found to have a significant impact on adalimumab clearance, and these reduced the inter-patient variability from 58.6 to 28.0%. On steady state in the simulated patient population, the mean trough level was 7.4 ± 5.5 mg/L. The two dosing regimens of 20 and 40 mg every other week, based on patients' body weight, resulted in comparable simulated overall drug exposure. CONCLUSIONS: Five literature models effectively described adalimumab PK in this pediatric cohort, highlighting the potential for extrapolating existing models to the pediatric population. The new JIA model confirmed the effect of several known covariates and found a novel association for drug clearance with methotrexate use (lower) and uveitis (higher), which might have clinical relevance for personalized dosing in JIA.

First validation of the childhood lupus low disease activity state (cLLDAS) definition in a real-life longitudinal cSLE cohort.

OBJECTIVES: To validate the childhood lupus low disease activity state (cLLDAS) definition in cSLE by describing differences in time to reach first adult LLDAS (aLLDAS) versus cLLDAS. Secondly, to analyse positive and negative predictors for maintaining cLLDAS for at least 50% of follow-up time (cLLDAS-50) and for the occurrence of damage. METHODS: Prospective longitudinal data from a cSLE cohort were analysed. Used definitions were: aLLDAS according to Franklyn, cLLDAS by cSLE treat-to-target (T2T) Task Force, disease activity score by SLEDAI -2 K and damage by SLICC damage index. RESULTS: Fifty cSLE patients were studied, with a median follow-up of 3.1 years. Each patient reached aLLDAS and cLLDAS at least once. Mean time to reach first aLLDAS/cLLDAS was 8.2/9.0 months, respectively. For 22/42 patients the mean steroid-dose related delay to reach first cLLDAS was 6.2 months. 58% of patients were able to maintain cLLDAS-50. Time to first cLLDAS (OR 0.8, p = 0.013) and higher number of flares (OR 0.374, p = 0.03) were negative predictors to maintain cLLDAS-50. Damage occurred in 34% of patients (23.5% steroid-related), in 64.7% within one year after diagnosis. African/Afro-Caribbean ethnicity, neuropsychiatric involvement and ever use of a biologic were significant predictors for damage. CONCLUSION: Time to reach cLLDAS in cSLE differs from time to (a)LLDAS, which validates the new cLLDAS definition. Attaining cLLDAS-50 was difficult in real-life. This cohort shows the high risk for early damage in cSLE. T2T with earlier focus on steroid-tapering and starting steroid-sparing drugs seems important to prevent (steroid-related) damage in cSLE.

Pharmacodynamics of rituximab in paediatric immune mediated diseases: B cell depletion and repopulation, effects on immunoglobulin levels and risk for infections.

OBJECTIVES: Rituximab (RTX), used for treatment in paediatric immune-mediated diseases, can lead to hypogammaglobulinaemia and thus to an increased risk of infection, but data on these adverse effects in children are scarce. We aimed to describe the pharmacodynamics of RTX by time to B cell repopulation in paediatric immune-mediated diseases and to assess whether low post-RTX immunoglobulin levels were associated with frequency and severity of infections. METHODS: Data of children with autoimmune diseases (AID), immune dysregulation (ID), haematological diseases (HD) and renal diseases (RD), including immunoglobulin levels pre-/post-RTX and occurrence of infections, who had received RTX at our centre were retrospectively collected. B cell depletion was defined as B cells <10 cells/µl. RESULTS: Post-RTX B cell depletion was achieved in 45/49 patients. In 30/45 patients with B cell repopulation, median time to repopulation was 166 days (IQR 140-224): AID group (n=9) (183 days (IQR 156-239), ID group (n=6) 170 days (IQR 128-184), HD group (n=7) 139 days (IQR 127-294), RD group (n=7) 160 days (IQR 121-367). Severe infections leading to hospitalisation occurred in 7/52 (13.5%) patients: ID (n=3), HD (n=1), RD (n=3). After RTX treatment, 13/52 patients (25%) had low IgG levels for their age at least once, 11/13 had an infection during low IgG but only 2/13 had a severe infection. Low IgG was not associated with severe infection (p=0.459). CONCLUSIONS: Time to B cell repopulation post-RTX ranged individually but did not significantly differ between paediatric patient groups. Severe infections were non-frequent and not associated with low (post-RTX) IgG levels.

Correlations between capillary density and degree of skin pigmentation in healthy children analysed by nailfold video capillaroscopy.

Background: Nailfold video capillaroscopy (NVC) is a simple, non-invasive diagnostic tool but studies with normal values for capillary density in healthy children are rare. Ethnic background seems to play a role in capillary density; however, this is not well substantiated yet. In this work, we set out to evaluate influence of ethnic background/skin pigmentation and age on capillary density reading in healthy children. Secondary aim was to investigate whether there is a significant difference in density between different fingers within the same patient. Methods: Between 2016 and 2021, healthy children from schools around AUMC were approached, by convenience sampling. In this cross-sectional study, capillaroscopic images were obtained in a one-time videocapillaroscopy (×200 magnification) addressing the capillary density (i.e., number of capillaries per linear millimetre in the distal row). This parameter was compared to age, sex, ethnicity, skin pigment grade (I-III) and between eight different fingers, excluding the thumbs. Density differences were compared by ANOVAs. Correlations between capillary density and age were calculated with Pearson correlations. Results: We investigated 145 healthy children with mean age of 11.03 years (SD 3.51). The range of capillary density was 4-11 capillaries per millimetre. We observed a lower capillary density in the 'grade II' (6.4±0.5 cap/mm, P<0.001) and 'grade III' (5.9±0.8 cap/mm, P<0.001) pigmented-classified groups compared to the 'grade I' group (7.0±0.7 cap/mm). We did not find a significant correlation between age and density in the overall group. The fifth fingers on both sides had a significantly lower density compared to the other fingers. Conclusions: Healthy children <18 years with higher degree of skin pigmentation show a significantly lower nailfold capillary density. In subjects with an African/Afro-Caribbean and North-African/Middle-Eastern ethnicity, a significantly lower mean capillary density was observed compared to subjects with the Caucasian ethnicity (P<0.001, and P<0.05, respectively. There were no significant differences between other ethnicities. No correlation was found between age and capillary density. The fifth fingers on both hands displayed lower capillary density compared to the other fingers. This needs to be taken into account when describing lower density in paediatric patients with connective tissue diseases.

Nailfold capillary scleroderma pattern may be associated with disease damage in childhood-onset systemic lupus erythematosus: important lessons from longitudinal follow-up.

OBJECTIVES: To observe if capillary patterns in childhood-onset SLE (cSLE) change over time and find associations between a capillary scleroderma pattern with disease activity, damage or scleroderma-like features. METHODS: Clinical and (yearly) capillaroscopy data from a longitudinal cohort of patients with cSLE (minimum of four Systemic Lupus International Collaborating Clinics (SLICC) criteria, onset <18 years) were analysed. Disease activity was measured by Systemic Lupus Erythematosus Activity Index (SLEDAI) and disease damage by SLICC Damage Index. A scleroderma pattern was defined according to the 'fast track algorithm' from the European League Against Rheumatism Study Group on Microcirculation in Rheumatic Diseases. An abnormal capillary pattern, not matching a scleroderma pattern, was defined as 'microangiopathy'. RESULTS: Our cohort consisted of 53 patients with cSLE with a median disease onset of 14 years (IQR 12.5-15.5 years), median SLEDAI score at diagnosis was 11 (IQR 8-16), median SLEDAI at follow-up was 2 (IQR 1-6). A scleroderma pattern (ever) was seen in 18.9%, while only 13.2% of patients had a normal capillary pattern. Thirty-three patients had follow-up capillaroscopy of which 21.2% showed changes in type of capillary pattern over time. Type of capillary pattern was not associated with disease activity. Raynaud's phenomenon (ever) was equally distributed among patients with different capillaroscopy patterns (p=0.26). Anti-ribonucleoprotein antibodies (ever) were significantly more detected (Χ2, p=0.016) in the scleroderma pattern subgroup (n=7 of 10, 70%). Already 5 years after disease onset, more than 50% of patients with a scleroderma pattern had SLE-related disease damage (HR 4.5, 95% CI 1.1 to 18.8, p=0.034), but they did not develop clinical features of systemic sclerosis at follow-up. Number of detected fingers with a scleroderma pattern was similar between cSLE, juvenile systemic sclerosis and juvenile undifferentiated connective tissue disease. CONCLUSION: This longitudinal study shows that the majority of capillary patterns in cSLE are abnormal and they can change over time. Irrespective of disease activity, a capillary scleroderma pattern in cSLE may be associated with higher risk of SLE-related disease damage.

Rarities in rare: illuminating the microvascular and dermal status in juvenile localised scleroderma. A case series.

OBJECTIVES: To assess the (structural and functional) characteristics of the microvascular and dermal status in juvenile localised scleroderma (jLoS), using novel non-invasive standardised research tools commonly used in adult systemic sclerosis (SSc). METHODS: Ten consecutive patients with a confirmed jLoS diagnosis were studied cross-sectionally in this two-centre case series. For each patient, the most prominent lesion (i.e., "target lesion") was chosen for further examination of the centre, edge and contralateral unaffected site. High-frequency ultrasonography was used to determine dermal thickness, durometer for skin hardness, and laser speckle contrast analysis (LASCA) for a dynamical evaluation of the microcirculation. The structure of the microcirculation was evaluated at the nailfolds of the 2nd-5th finger bilaterally, using nailfold videocapillaroscopy (NVC). RESULTS: 6 linear and 4 plaque subtype jLoS lesions were included. Dermal thickness was thinner at the centre of the "target lesions" vs. the edges (p<0.001) and control sites (p<0.001). Skin hardness was harder at the centre of the "target lesions" vs. the edges (p=0.012) and control sites (p=0.003). A higher perfusion was found in the centre of the "target lesion" (124.87±66.40 PU) vs. the edges (87.27±46.40 PU; p<0.001) and control sites (67.85±37.49; p<0.001). Of note, all patients had a "non-scleroderma" pattern on NVC. CONCLUSIONS: This case series suggests the supportive value of both microcirculatory and dermal assessments of skin lesions using novel non-invasive research tools, adopted from adult SSc, for (j)LoS.

Reliable detection of subtypes of nailfold capillary haemorrhages in childhood-onset systemic lupus erythematosus.

OBJECTIVES: In systemic lupus erythematosus (SLE), it is necessary to obtain biomarkers that predict cardiovascular complications due to premature atherosclerosis, which is related to endothelial dysfunction. Nailfold capillary abnormalities might be a biomarker for endothelial dysfunction. In adults and children with SLE, nailfold capillary haemorrhages have shown to be significantly correlated with disease activity. Recently, different subtypes of capillary haemorrhages have been described in childhood-onset SLE (cSLE). The aim of the current study was to assess the inter- and intra-rater reliability of observations of different subtypes of haemorrhages in cSLE patients. METHODS: Five raters blindly evaluated 140 capillaroscopy images from 35 cSLE-patients (diagnosed according to the 2012 SLICC criteria). The images were assessed qualitatively (present or absent) and quantitatively (total number) on four different subtypes of haemorrhages: 1) punctate extravasations, 2) perivascular haemorrhage, 3) large confluent haemorrhage and 4) non-definable. As subgroups 1) and 2) were interpreted as a continuous spectrum, a post-hoc analysis with "merged" (mean) kappa/ICC was additionally calculated as one sub-group. RESULTS: Qualitative assessment showed a kappa 0.65 (95% CI: 0.60-0.70) for "punctate extravasations and perivascular haemorrhages merged" and a kappa 0.78 (95% CI: 0.72-0.83) for large confluent haemorrhages. For the quantitative assessment, ICC was 0.82 (95% CI: 0.76-0.87) for the "merged groups" and ICC 0.93 (95% CI: 0.91-0.95) for large confluent haemorrhages. CONCLUSIONS: Our study shows that different subtypes of capillary haemorrhages in cSLE-patients could be reliably reproduced by different raters. This confirms our recent observation of perivascular extravasations as a subgroup of capillary haemorrhage in cSLE that might reflect endothelial dysregulation.

Nailfold capillary abnormalities in childhood-onset systemic lupus erythematosus: a cross-sectional study compared with healthy controls.

OBJECTIVES: For selection of high-risk systemic lupus erythematosus (SLE) patients it is necessary to obtain indicators of disease severity that predict disease damage. As in systemic sclerosis, nailfold capillary abnormalities could be such a biomarker in SLE. The primary objective of this cross-sectional study is to describe capillary abnormalities in childhood-onset SLE (cSLE) cohort (onset < 18 years) and compare them with matched healthy controls. The secondary objective is to correlate the observed capillary abnormalities with demographical variables in both cohorts and with disease-specific variables in cSLE patients. METHODS: Healthy controls were matched for ethnic background, age and gender. Videocapillaroscopy was performed in eight fingers with 2-4 images per finger. Quantitative and qualitative assessments of nailfold capillaroscopy images were performed according to the definitions of the EULAR study group on microcirculation in Rheumatic Diseases. RESULTS: Both groups (n = 41 cSLE-patients and n = 41 healthy controls) were comparable for ethnic background (p = 0.317). Counted per mm, cSLE-patients showed significantly more 'giants' (p = 0.032), 'abnormal capillary shapes' (p = 0.003), 'large capillary hemorrhages' (p < 0.001) and 'pericapillary extravasations' (p < 0.001). Combined 'abnormal capillary shapes and pericapillary extravasations' (in the same finger) were detected in 78% (32/41 patients). By qualitative analysis, 'microangiopathy' was detected in 68.3% (28/41) and a 'scleroderma pattern' in 17.1% (7/41) of the cSLE-patients (without scleroderma symptoms). The difference of percentage positive anti-RNP antibodies in the group with or without a scleroderma pattern was not significant (p = 0.089). The number of 'abnormal capillary shapes per mm' was significantly correlated with treatment-naivety. The number of 'large pathological hemorrhages per mm' was significantly correlated with SLEDAI score and presence of nephritis. Compared to healthy controls, 'pericapillary extravasations' were found in significantly higher numbers per mm (p < 0.001) as well as in percentage of patients (p < 0.001). CONCLUSIONS: Our observations confirm that giants, abnormal capillary morphology and capillary hemorrhages are also observed in cSLE, as was already known for adults with SLE. Number of capillary hemorrhages in cSLE was significantly correlated with disease activity. A high frequency and total amount of "pericapillary extravasations" was observed in cSLE patients, possibly revealing a new subtype of capillary hemorrhage that might reflect endothelial damage in these pediatric patients.