Suppression of NK Cell Activation by JAK3 Inhibition: Implication in the Treatment of Autoimmune Diseases.

Natural killer (NK) cell is an essential cytotoxic lymphocyte in our innate immunity. Activation of NK cells is of paramount importance in defending against pathogens, suppressing autoantibody production and regulating other immune cells. Common gamma chain (γc) cytokines, including IL-2, IL-15, and IL-21, are defined as essential regulators for NK cell homeostasis and development. However, it is inconclusive whether γc cytokine-driven NK cell activation plays a protective or pathogenic role in the development of autoimmunity. In this study, we investigate and correlate the differential effects of γc cytokines in NK cell expansion and activation. IL-2 and IL-15 are mainly responsible for NK cell activation, while IL-21 preferentially stimulates NK cell proliferation. Blockade of Janus tyrosine kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway by either JAK inhibitors or antibodies targeting γc receptor subunits reverses the γc cytokine-induced NK cell activation, leading to suppression of its autoimmunity-like phenotype in vitro. These results underline the mechanisms of how γc cytokines trigger autoimmune phenotype in NK cells as a potential target to autoimmune diseases.

A randomized, controlled single, and multiple ascending dose trial of the safety, pharmacokinetics and pharmacodynamics of SN1011 in healthy subjects.

The purpose of this study was to investigate the safety, tolerability, pharmacokinetics, and pharmacodynamics of SN1011, a novel Bruton tyrosine kinase (BTK) inhibitor, and food effects in healthy subjects. In this phase I trial, subjects received single ascending doses (SADs) of SN1011 (100 to 800 mg), multiple ascending doses (MADs) of SN1011 (200 to 600 mg), or placebo q.d. Additionally, 12 subjects randomly received a single dose of SN1011 600 mg under fasting states and then fed states, vice versa. Safety was assessed per Common Terminology Criteria for Adverse Events version 5.0. Pharmacokinetic parameters were calculated by noncompartmental analysis and BTK receptor occupancy in peripheral blood monocytes was determined. Seventy-one healthy subjects were dosed in five SAD cohorts, three MAD cohorts, and one food effect cohort, with 57 receiving SN1011 and 14 receiving placebo. No serious adverse events (AEs) were reported. There was no correlation between AE occurrences and SN1011 exposure. The three most frequent AEs with SN1011 were increased blood triglycerides, decreased neutrophil count, and decreased leucocyte count. SN1011 exhibited a dose-proportional increase in maximum plasma concentration and area under the time concentration curve following single and multiple dose administrations, with an accumulation ratio of 1.5 to 2.2 after multiple dose administrations. No difference in SN1011 exposure was observed between fed states. BTK receptor occupancy remained above 83% over 24 h after single administration and remained above 80% for the MAD groups for 10 days of continuous q.d. administration. SN1011 was well-tolerated and safe after single or multiple exposures to healthy subjects, supporting further clinical development of SN1011 for treatment of autoimmune diseases.

Interleukins 4 and 21 Protect Anti-IgM Induced Cell Death in Ramos B Cells: Implication for Autoimmune Diseases.

Interleukins 4 (IL-4) and 21 (IL-21) belong to the common gamma chain cytokine family which are highly involved in the progression of autoimmune diseases. While IL-4 is well known to be involved in the suppression of apoptosis of autoreactive B cells, the role played by IL-21 remains unclear. In the current study, we activated the human Burkitt's lymphoma Ramos B cells with anti-IgM to mimic B cell hyperactivation observed in patients of autoimmune diseases. Consistent with other reported findings, anti-IgM led to the downregulation of proteins involved in B cell survival and proliferation, as well as the activation of caspase 3 activity and DNA damage, resulting in apoptotic cell death after 48-hour treatment. Although both IL-4 and IL-21 reversed anti-IgM-induced apoptosis and cell cycle arrest, they did so via different mechanisms: while IL-4 could directly suppress anti-IgM-induced caspase 3 activation and marker indicative of DNA damage, IL-21 could induce B cell proliferation in the presence of anti-IgM. Importantly, IL-21 also suppressed activation induced cell death in human primary B cells. Pre-treatment with clinically validated JAK inhibitors completely reversed the effects of IL-4 and IL-21 to rescue anti-IgM induced cell death and DNA damage. The results indicate the underlying mechanisms of how IL-4 and IL-21 differentially promote survival of hyperactivated B cells and provide hints to treat autoimmune diseases.

SM03, an anti-human CD22 monoclonal antibody, for active rheumatoid arthritis: a phase II, randomized, double-blind, placebo-controlled study.

OBJECTIVE: SM03, a novel chimaeric mAb specific to B cell-restricted antigen CD22, has been developed to treat RA and other B-cell-related diseases. This 24-week phase II randomized, double-blind, multi-dose, placebo-controlled study aimed to evaluate the efficacy and safety of SM03 in moderately-to-severely active RA patients in China. METHODS: One hundred and fifty-six patients on background MTX were randomized in a 1:1:1 ratio to receive a cumulative dose of 3600 mg (high dose, 600 mg × 6 infusions at weeks 0, 2, 4, 12, 14 and 16) or 2400 mg SM03 (low dose, 600 mg × 4 infusions at weeks 0, 2, 12 and 14) or the placebo. The primary outcome was the 24-week ACR 20% improvement criteria (ACR20) response rate. Safety was also assessed. RESULTS: The 24-week ACR20 response rate was significantly higher with high- (65.3%, P = 0.002) and low-dose SM03 (56.9%, P = 0.024) than with placebo (34.0%), but comparable between the high- and low-dose group. The rate of adverse events was not statistically different among the high-dose group (35.3%), the low-dose group (51.9%) and the placebo group (34.6%). Thirteen (12.6%) patients receiving SM03 reported treatment-emergent infections, including 3.9% patients in the high-dose group. No patients reported severe treatment-emergent infections or malignancies. CONCLUSIONS: In active RA Chinese patients receiving background MTX, SM03 at a cumulative dose of both 2400 mg and 3600 mg is efficacious and well-tolerated throughout the 24 weeks of treatment. Moreover, SM03 has demonstrated a good safety profile. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT04192617.

An open-label, multiple-dose study to assess the preliminary pharmacokinetics, pharmacodynamics, clinical activity, and safety of human mouse chimeric anti-CD22 monoclonal antibody (SM03) in patients with rheumatoid arthritis.

BACKGROUND: The pharmacokinetics, safety, and clinical activity of antibodies targeting CD22 have been evaluated in systemic lupus erythematosus (SLE) and non-Hodgkin lymphoma (NHL) patients, however, there have been no reports for the rheumatoid arthritis (RA) population. SM03 is a novel chimeric IgG1 monoclonal antibody which targets the B-cell-restricted antigen CD22. This is the first study of the anti-CD22 antibody in RA patients. OBJECTIVES: This study was designed to preliminarily evaluate the pharmacokinetics, pharmacodynamics, safety, and clinical activity profiles of the anti-CD22 monoclonal antibody SM03 in Chinese patients with active RA. MATERIALS AND METHODS: This study was an open phase I study in 8 RA patients. Eligible patients received two 600 mg doses of SM03 administered through intravenous infusions given 2 weeks apart and were monitored over an 84-day observation period for pharmacokinetics, pharmacodynamics, immunogenicity, safety, and clinical responses. RESULTS: After multiple doses of SM03, the maximum serum concentration of SM03 was reached within 2 - 4 hours. Mean elimination half-life was 16 days (range: 13 - 22 days). Half of the patients responded according to ACR and DAS28 assessments, and CD19+ B lymphocyte counts decreased. Upper respiratory tract infections and headaches were the most common adverse events (AEs). No drug-related serious AEs were reported. CONCLUSION: This study is the first to report on the preliminary pharmacokinetics, pharmacodynamics, clinical activity, and safety of SM03 in RA patients. All AEs were mild or moderate in severity. SM03 showed potential efficacy in RA patients.

Pharmacokinetics, Pharmacodynamics and Preliminary Observations for Clinical Activity and Safety of Multiple Doses of Human Mouse Chimeric Anti-CD22 Monoclonal Antibody (SM03) in Chinese Patients with Systemic Lupus Erythematosus.

BACKGROUND AND OBJECTIVES: SM03 is a novel recombinant, human/mouse chimeric immunoglobulin G1 monoclonal antibody directed against the CD22 antigen on human B lymphocytes. This was the first study to investigate the pharmacokinetics, pharmacodynamics, immunogenicity, safety and clinical activity of SM03 in patients with systemic lupus erythematosus (SLE). METHODS: This study was an open, multiple-centre, parallel-group, multiple-ascending-dose, phase I study in 29 SLE patients. Pharmacokinetic assessment was conducted in 22 of these patients. Eligible patients received multiple intravenous infusions of SM03 for 4 weeks (240 mg/m2, 600 or 900 mg, once weekly) and were monitored over an 84-day observation period for pharmacokinetics, pharmacodynamics, immunogenicity, safety and clinical response. RESULTS: After multiple-dose SM03, the maximal serum concentration of SM03 was reached within 3-7 h. The mean elimination half-life was 15 days. The average accumulation ratios of the area under the time-concentration curve and the maximum concentration after the fourth administration of SM03 were 2.0 and 1.5. CD19+ B-lymphocyte counts were decreased. Infections were the most common adverse events. No drug-related serious adverse events were reported. The therapeutic benefit of SM03 was observed mainly in patients with moderate-to-severe disease activity. CONCLUSION: Pharmacokinetic exposure increased in a lower-than-dose-proportional manner up to 900 mg. SM03 was well tolerated at doses ranging from 240 mg/m2 to 900 mg, with no new safety signals identified. SM03 has potential efficacy in Chinese patients with SLE.

Surrogate target cells expressing surface anti-idiotype antibody for the clinical evaluation of an internalizing CD22-specific antibody.

SM03, a chimeric antibody that targets the B-cell restricted antigen CD22, is currently being clinically evaluated for the treatment of lymphomas and other autoimmune diseases in China. SM03 binding to surface CD22 leads to rapid internalization, making the development of an appropriate cell-based bioassay for monitoring changes in SM03 bioactivities during production, purification, storage, and clinical trials difficult. We report herein the development of an anti-idiotype antibody against SM03. Apart from its being used as a surrogate antigen for monitoring SM03 binding affinities, the anti-idiotype antibody was engineered to express as fusion proteins on cell surfaces in a non-internalizing manner, and the engineered cells were used as novel "surrogate target cells" for SM03. SM03-induced complement-mediated cytotoxicity (CMC) against these "surrogate target cells" proved to be an effective bioassay for monitoring changes in Fc functions, including those resulting from minor structural modifications borne within the Fc-appended carbohydrates. The approach can be generally applied for antibodies that target rapidly internalizing or non-surface bound antigens. The combined use of the anti-idiotype antibody and the surrogate target cells could help evaluate clinical parameters associated with safety and efficacies, and possibly the mechanisms of action of SM03.

Generation of anti-idiotype scFv for pharmacokinetic measurement in lymphoma patients treated with chimera anti-CD22 antibody SM03.

Pre-clinical and clinical studies of therapeutic antibodies require highly specific reagents to examine their immune responses, bio-distributions, immunogenicity, and pharmacodynamics in patients. Selective antigen-mimicking anti-idiotype antibody facilitates the assessment of therapeutic antibody in the detection, quantitation and characterization of antibody immune responses. Using mouse specific degenerate primer pairs and splenocytic RNA, we generated an idiotype antibody-immunized phage-displayed scFv library in which an anti-idiotype antibody against the therapeutic chimera anti-CD22 antibody SM03 was isolated. The anti-idiotype scFv recognized the idiotype of anti-CD22 antibody and inhibited binding of SM03 to CD22 on Raji cell surface. The anti-idiotype scFv was subsequently classified as Ab2γ type. Moreover, our results also demonstrated firstly that the anti-idiotype scFv could be used for pharmacokinetic measurement of circulating residual antibody in lymphoma patients treated with chimera anti-CD22 monoclonal antibody SM03. Of important, the present approach could be easily adopted to generate anti-idiotype antibodies for therapeutic antibodies targeting membrane proteins, saving the cost and time for producing a soluble antigen.