Identifying lupus Patient Subsets Through Immune Cell Deconvolution of Gene Expression Data in Two Atacicept Phase II Studies.

OBJECTIVE: To use cell-based gene signatures to identify patients with systemic lupus erythematous (SLE) in the phase II/III APRIL-SLE and phase IIb ADDRESS II trials most likely to respond to atacicept. METHODS: A published immune cell deconvolution algorithm based on Affymetrix gene array data was applied to whole blood gene expression from patients entering APRIL-SLE. Five distinct patient clusters were identified. Patient characteristics, biomarkers, and clinical response to atacicept were assessed per cluster. A modified immune cell deconvolution algorithm was developed based on RNA sequencing data and applied to ADDRESS II data to identify similar patient clusters and their responses. RESULTS: Patients in APRIL-SLE (N = 105) were segregated into the following five clusters (P1-5) characterized by dominant cell subset signatures: high neutrophils, T helper cells and natural killer (NK) cells (P1), high plasma cells and activated NK cells (P2), high B cells and neutrophils (P3), high B cells and low neutrophils (P4), or high activated dendritic cells, activated NK cells, and neutrophils (P5). Placebo- and atacicept-treated patients in clusters P2,4,5 had markedly higher British Isles Lupus Assessment Group (BILAG) A/B flare rates than those in clusters P1,3, with a greater treatment effect of atacicept on lowering flares in clusters P2,4,5. In ADDRESS II, placebo-treated patients from P2,4,5 were less likely to be SLE Responder Index (SRI)-4, SRI-6, and BILAG-Based Combined Lupus Assessment responders than those in P1,3; the response proportions again suggested lower placebo effect and a greater treatment differential for atacicept in P2,4,5. CONCLUSION: This exploratory analysis indicates larger differences between placebo- and atacicept-treated patients with SLE in a molecularly defined patient subset.

Population pharmacokinetics of atacicept in systemic lupus erythematosus: An analysis of three clinical trials.

B cell stimulating factor (BLyS) and a proliferation-inducing ligand (APRIL) are targets for novel treatments in patients with systemic lupus erythematosus (SLE). Atacicept is a recombinant, soluble fusion protein that blocks BLyS and APRIL activity. This study characterized the pharmacokinetic (PK) profile of atacicept using a population PK model and identified covariates explaining the PK variability. Total atacicept concentrations from a phase I study in healthy volunteers and two phase II studies in patients with SLE, using subcutaneous administration, were modeled using a quasi-steady-state approximation of the target-mediated drug disposition model with first-order absorption. The model included 3640 serum atacicept concentration records from 37 healthy volunteers and 503 patients with SLE and described total atacicept concentrations of the three trials, providing precise estimates of all parameters. Body weight and baseline BLyS concentration were the only statistically significant covariates, whereas no differences were found between patients and healthy volunteers. Apparent clearance and volume of the central compartment increased with body weight and initial target concentration increased with baseline BLyS. The change on atacicept exposure was moderate, with a difference in area under the curve compared with the median of 20%-32% for body weight, and 7%-18% for BLyS. Therefore, the effects of these covariates on atacicept exposure are not expected to be clinically relevant. The model described the complete total atacicept concentration-time profiles without finding any differences between healthy subjects and patients with SLE and supports the 150 mg once weekly dose for further trials.

Applying Modeling and Simulations for Rational Dose Selection of Novel Toll-Like Receptor 7/8 Inhibitor Enpatoran for Indications of High Medical Need.

Dual toll-like receptor (TLR) 7 and TLR8 inhibitor enpatoran is under investigation as a treatment for lupus and coronavirus disease 2019 (COVID-19) pneumonia. Population pharmacokinetic/pharmacodynamic (PopPK/PD) model-based simulations, using PK and PD (inhibition of ex vivo-stimulated interleukin-6 (IL-6) and interferon-α (IFN-α) secretion) data from a phase I study of enpatoran in healthy participants, were leveraged to inform dose selection for lupus and repurposed for accelerated development in COVID-19. A two-compartment PK model was linked to sigmoidal maximum effect (Emax ) models with proportional decrease from baseline characterizing the PD responses across the investigated single and multiple doses, up to 200 mg daily for 14 days (n = 72). Concentrations that maintain 50/60/90% inhibition (IC50/60/90 ) of cytokine secretion (IL-6/IFN-α) over 24 hours were estimated and stochastic simulations performed to assess target coverage under different dosing regimens. Simulations suggested investigating 25, 50, and 100 mg enpatoran twice daily (b.i.d.) to explore the anticipated therapeutic dose range for lupus. With 25 mg b.i.d., > 50% of subjects are expected to achieve 60% inhibition of IL-6. With 100 mg b.i.d., most subjects are expected to maintain almost complete target coverage for 24 hours (> 80% subjects IC90,IL-6  = 15.5 ng/mL; > 60% subjects IC90,IFN-α  = 22.1 ng/mL). For COVID-19, 50 and 100 mg enpatoran b.i.d. were recommended; 50 mg b.i.d. provides shorter IFN-α inhibition (median time above IC90  = 13 hours/day), which may be beneficial to avoid interference with the antiviral immune response. Utilization of PopPK/PD models initially developed for lupus enabled informed dose selection for the accelerated development of enpatoran in COVID-19.

Partial STAT5 signaling is sufficient for CD4+ T cell priming but not memory formation.

Signal transducer and activator of transcription 5 (STAT5) plays an important role in regulating gene expression in response to cytokines of the common (γc) chain family. In this capacity, STAT5 promotes CD8+ effector and memory T cell survival and regulatory T cell development. However, its function in conventional CD4+ T cells is less clear. In this study, the requirement of intact STAT5 signaling for CD4+ effector and memory T cell generation and maintenance was investigated by using DO11.10 TCR transgenic T cells that are genetically deficient in STAT5A or B, as well as by transducing DO11 T cells with a dominant-negative STAT5 to temporally block STAT5 function. We found that the presence of STAT5A or B alone was sufficient for primary CD4+ effector T cell generation, but not for establishing a long-lived memory cell population. Similarly, blocking STAT5 signaling during priming did not prevent initial T cell activation, but inhibited the generation of memory cells. Surprisingly, blocking STAT5 post-priming did not impact the long-term survival of CD4+ memory T cells in vivo. Mechanistically, intact STAT5B, but not STAT5A, was required for IL-7Rα re-expression in activated T cells, which is an important cytokine receptor for CD4+ memory generation. These data show that fully functional STAT5 is essential to deliver an early, non-redundant signal for memory programming during the primary CD4+ T cell response, while partial STAT5 signaling is sufficient for effector differentiation. Our results have implications for the precise use of STAT5 inhibitors to timely inhibit memory T cell responses.

Safety and clinical activity of atacicept in the long-term extension of the phase 2b ADDRESS II study in systemic lupus erythematosus.

OBJECTIVES: Atacicept reduced SLE disease activity in the phase 2b ADDRESS II study, particularly in patients with high disease activity (HDA; SLEDAI-2K ≥10) at screening. We assessed long-term safety and efficacy of atacicept in the long-term extension (LTE) of ADDRESS II. METHODS: In the 24-week, randomized, double-blind, placebo-controlled ADDRESS II study, patients received weekly atacicept (75 or 150 mg) or placebo. Atacicept was continued at the same dose in atacicept-treated patients in the LTE; placebo-treated patients switched to atacicept 150 mg. Long-term safety was the primary endpoint. Secondary endpoints included SLE responder index (SRI)-4 and SRI-6 response rates and flares. RESULTS: In total, 253 patients entered the ADDRESS II LTE; 88 received atacicept 150 mg, 82 atacicept 75 mg and 83 placebo/atacicept 150 mg. Median active treatment duration in the LTE was 83.8 weeks. Frequencies of treatment-emergent adverse events (TEAEs) were similar across groups (90.4-93.2%), and 12.5%, 14.6% and 21.7% of patients in the atacicept 150 mg, atacicept 75 mg and placebo/atacicept 150 mg groups reported serious TEAEs during the treatment period. The proportions of patients with TEAEs leading to discontinuation were 5.7%, 4.9% and 10.8%, respectively. SRI-4 and SRI-6 response rates were maintained with atacicept in the modified intent-to-treat and HDA populations and those on continuous 150 mg had a reduced risk of first severe flare and longer time to first severe flare vs those who initially received placebo. CONCLUSION: Long-term treatment with atacicept 150 mg in SLE patients had an acceptable safety profile, with durable efficacy. TRIAL REGISTRATION: ClinicalTrials.gov, http://clinicaltrials.gov, NCT02070978.

STRATUS: A Phase II Study of Abituzumab in Patients With Systemic Sclerosis-associated Interstitial Lung Disease.

OBJECTIVE: To investigate the effects of abituzumab in systemic sclerosis-associated interstitial lung disease (SSc-ILD). METHODS: STRATUS was a phase II, double-blind, parallel-group, multicenter trial (ClinicalTrials.gov: NCT02745145). Adults (≤ 75 yrs) with SSc-ILD on stable mycophenolate were randomized (2:2:1) to receive intravenous abituzumab 1500 mg, abituzumab 500 mg, or placebo every 4 weeks for 104 weeks. The primary endpoint was the annual rate of change in absolute forced vital capacity. RESULTS: STRATUS was terminated prematurely due to slow enrollment (n = 75 screened, n = 24 randomized), precluding robust analysis of efficacy. Abituzumab was well tolerated; no new safety signals were detected. CONCLUSION: Further investigation of abituzumab for treatment of SSc-ILD is required.

Attainment of treat-to-target endpoints in SLE patients with high disease activity in the atacicept phase 2b ADDRESS II study.

OBJECTIVE: Low disease activity (LDA) and remission are emerging treat-to-target (T2T) endpoints in SLE. However, the rates at which these endpoints are met in patients with high disease activity (HDA) are unknown. Atacicept, which targets B lymphocyte stimulator and a proliferation-inducing ligand, improved disease outcomes in SLE patients with HDA (SLEDAI-2K ≥10) at baseline in the phase 2b ADDRESS II study. This is a post hoc analysis of T2T endpoints in these patients. METHODS: Patients received weekly atacicept (75 or 150 mg s.c.) or placebo for 24 weeks (1:1:1 randomization). Attainment of three T2T endpoints, LDA (SLEDAI-2K ≤ 2), Lupus Low Disease Activity State (LLDAS) and remission (clinical SLEDAI-2K = 0, prednisone-equivalent ≤5mg/day and Physician's Global Assessment <0.5), was assessed and compared with SLE Responder Index (SRI)-4 and SRI-6 response. RESULTS: Of 306 randomized patients, 158 (51.6%) had baseline HDA. At week 24, 37 (23.4%) HDA patients attained LDA, 25 (15.8%) LLDAS and 17 (10.8%) remission. Each of these endpoints was more stringent than SRI-4 (n = 87; 55.1%) and SRI-6 (n = 67; 42.4%). Compared with placebo (n = 52), at week 24, patients treated with atacicept 150 mg (n = 51) were more likely to attain LDA [odds ratio (OR) 3.82 (95% CI: 1.44, 10.15), P = 0.007], LLDAS [OR 5.03 (95% CI: 1.32, 19.06), P = 0.018] or remission [OR 3.98 (95% CI: 0.78, 20.15), P = 0.095]. CONCLUSION: At week 24, LDA, LLDAS and remission were more stringent than SRI-4 and SRI-6 response, were attainable in the HDA population and discriminated between treatment with atacicept 150 mg and placebo. These results suggest that T2T endpoints are robust outcome measures in SLE clinical trials and support further evaluation of atacicept in SLE. TRAIL REGISTRATION: ClinicalTrials.gov, http://clinicaltrials.gov, NCT01972568.

Combining anti-IL-7Rα antibodies with autoantigen-specific immunotherapy enhances non-specific cytokine production but fails to prevent Type 1 Diabetes.

Autoantigen-specific methods to prevent and treat Type 1 Diabetes (T1D) carry high hopes to permanently cure this disease, but have largely failed in clinical trials. One suggested approach to increase the efficacy of islet antigen-specific vaccination is to combine it with a modulator of the T cell response, with the goal of reducing effector differentiation and promoting regulatory T cells (Tregs). Here we asked if addition of antibodies that block the IL-7/IL-7Rα pathway altered the T cell response to islet antigen vaccination and prevented T1D in non-obese diabetic (NOD) mice. Anti-IL-7Rα monoclonal antibodies (mAbs) reduced the numbers of islet antigen-specific T cells generated after vaccination with islet peptides and alum. However, addition of anti-IL-7Rα antibodies to peptide/alum vaccination unexpectedly increased non-specific IFN-γ, IL-2 and IL-10 cytokine production and did not result in improved prevention of T1D onset. In a second approach, we used a conjugate vaccine to deliver islet autoantigens, using Keyhole Limpet Hemocyanin (KLH) as a carrier. Islet antigen-KLH vaccination led to a significant expansion of antigen-specific Tregs and delayed diabetes onset in NOD mice. These outcomes were not further improved by addition of anti-IL-7Rα antibodies. To the contrary, blocking IL-7Rα during vaccination led to non-specific cytokine production and reduced the efficacy of a KLH-conjugated vaccine to prevent T1D. Our study thus revealed that adding anti-IL-7Rα antibodies during autoantigen immunization did not improve the efficacy of such vaccinations to prevent T1D, despite altering some aspects of the T cell response in a potentially advantageous way. Further refinement of this approach will be required to separate the beneficial from the adverse effects of anti-IL-7Rα antibodies to treat autoimmune disease.

Ongoing clinical trials and treatment options for patients with systemic sclerosis-associated interstitial lung disease.

SSc is a rare CTD that affects multiple organ systems, resulting in substantial morbidity and mortality. Evidence of interstitial lung disease (ILD) is seen in ∼80% of patients with SSc. Currently there is no approved disease-modifying treatment for ILD and few effective treatment options are available. CYC is included in treatment guidelines, but it has limited efficacy and is associated with toxicity. MMF is becoming the most commonly used medication in clinical practice in North America and the UK, but its use is not universal. Newer agents targeting the pathogenic mechanisms underlying SSc-ILD, including fibrotic and inflammatory pathways, lymphocytes, cell-cell and cell-extracellular membrane interactions, hold promise for better treatment outcomes, including improved lung function, patient-related outcomes and quality of life. Here we review ongoing trials of established and novel agents that are currently recruiting patients with SSc-ILD.

On How Fas Apoptosis-Independent Pathways Drive T Cell Hyperproliferation and Lymphadenopathy in lpr Mice.

Fas induces massive apoptosis in T cells after repeated in vitro T cell receptor (TCR) stimulation and is critical for lymphocyte homeostasis in Fas-deficient (lpr) mice. Although the in vitro Fas apoptotic mechanism has been defined, there is a large conceptual gap between this in vitro phenomenon and the pathway that leads to in vivo development of lymphadenopathy and autoimmunity. A striking abnormality in lpr mice is the excessive proliferation of CD4+ and CD8+ T cells, and more so of the double-negative TCR+CD4-CD8-B220+ T cells. The basis of lpr T cell hyperproliferation remains elusive, as it cannot be explained by Fas-deficient apoptosis. T cell-directed p21 overexpression reduces hyperactivation/hyperproliferation of all lpr T cell subtypes and lymphadenopathy in lpr mice. p21 controls expansion of repeatedly stimulated T cells without affecting apoptosis. These results confirm a direct link between hyperactivation/hyperproliferation, autoreactivity, and lymphadenopathy in lpr mice and, with earlier studies, suggest that Fas apoptosis-independent pathways control lpr T cell hyperproliferation. lpr T cell hyperproliferation could be an indirect result of the defective apoptosis of repeatedly stimulated lpr T cells. Nonetheless, in this perspective, we argue for an alternative setting, in which lack of Fas would directly cause lpr T cell hyperactivation/hyperproliferation in vivo. We propose that Fas/Fas ligand (FasL) acts as an activation inhibitor of recurrently stimulated T cells, and that its disruption causes overexpansion of T cells in lpr mice. Research to define the underlying mechanism of this Fas/FasL effect could resolve the phenotype of lpr mice and lead to therapeutics for related human syndromes.

Broad induction of immunoregulatory mechanisms after a short course of anti-IL-7Rα antibodies in NOD mice.

BACKGROUND: Type 1 diabetes is an autoimmune disease caused by T cell-mediated destruction of the insulin-producing ß-cells in the pancreas. Therefore, approaches that effectively halt the pathogenic T cell response are predicted to have preventive or therapeutic benefit for type 1 diabetes patients. We previously demonstrated that long-term blocking of IL-7 signaling, which is critical for the survival and function of T cells, prevented and reversed type 1 diabetes in non-obese diabetic mice. However, such persistent inhibition of T cell responses raises concerns about causing immunodeficiency. Here, we asked whether a reduced duration of the treatment with anti-IL-7Rα antibodies retained efficacy in preventing diabetes. Moreover, we sought to identify immunoregulatory mechanisms induced by anti-IL-7Rα administration. RESULTS: Anti-IL-7Rα antibodies were administered to prediabetic NOD mice for 3 weeks and blood samples were taken at the end of treatment and 2 weeks later to analyze changes in T cell phenotypes in response to IL-7Rα blockade. We found that the co-inhibitory receptors LAG-3, Tim-3 and PD-1 were increased on peripheral blood CD4+ and CD8+ T cells from anti-IL-7Rα-treated mice. Expression of these receptors contributed to reduced T cell cytokine production in response to TCR stimulation. In addition, the frequency of Tregs within the circulating CD4+ T cells was increased at the end of anti-IL-7Rα antibody treatment and these Tregs showed a more activated phenotype. In vitro restimulation assays revealed that effector T cells from anti-IL-7Rα-treated mice were more sensitive to co-inhibitory receptor induction after TCR stimulation. Importantly, these changes were accompanied by delayed type 1 diabetes disease kinetics. CONCLUSIONS: Together, our data show that short-term blockade of IL-7Rα induces detectable changes in co-inhibitory receptor expression and Treg frequencies in peripheral blood of NOD mice. These changes appear to have long-lasting effects by delaying or preventing type 1 diabetes incidence. Hence, our study provides further support for using anti-IL-7Rα antibodies to modulate autoreactive T cell responses.

Distinct p21 requirements for regulating normal and self-reactive T cells through IFN-γ production.

Self/non-self discrimination characterizes immunity and allows responses against pathogens but not self-antigens. Understanding the principles that govern this process is essential for designing autoimmunity treatments. p21 is thought to attenuate autoreactivity by limiting T cell expansion. Here, we provide direct evidence for a p21 role in controlling autoimmune T cell autoreactivity without affecting normal T cell responses. We studied C57BL/6, C57BL/6/lpr and MRL/lpr mice overexpressing p21 in T cells, and showed reduced autoreactivity and lymphadenopathy in C57BL/6/lpr, and reduced mortality in MRL/lpr mice. p21 inhibited effector/memory CD4(+) CD8(+) and CD4(-)CD8(-) lpr T cell accumulation without altering defective lpr apoptosis. This was mediated by a previously non-described p21 function in limiting T cell overactivation and overproduction of IFN-γ, a key lupus cytokine. p21 did not affect normal T cell responses, revealing differential p21 requirements for autoreactive and normal T cell activity regulation. The underlying concept of these findings suggests potential treatments for lupus and autoimmune lymphoproliferative syndrome, without compromising normal immunity.