Evaluation of the safety, efficacy, and mechanism of action of obexelimab for the treatment of patients with IgG4-related disease: an open-label, single-arm, single centre, phase 2 pilot trial

BACKGROUND

Obexelimab is a bifunctional, non-cytolytic, humanised monoclonal antibody that binds CD19 and Fc gamma receptor IIb to inhibit B cells, plasmablasts, and CD19-expressing plasma cells. We aimed to evaluate the safety, clinical efficacy, and pharmacodynamic effects of obexelimab in patients with active IgG4-related disease.

METHODS

We conducted an open-label, single-arm, single centre, phase 2 pilot trial at the Massachusetts General Hospital in Boston, MA, USA. Eligible patients were aged 18-80 years and had active IgG4-related disease confirmed by an IgG4-related disease responder index score of 3 or more. Patients received 5 mg/kg of obexelimab intravenously every 2 weeks for 24 weeks. Patients on glucocorticoids at baseline were expected to discontinue usage within 2 months following enrolment. The primary endpoint was the proportion of patients with a decrease of 2 or more from baseline in the IgG4-related disease responder index at day 169 (ie, primary responders). Patients who achieved a decrease of 2 or more at any visit were designated as responders. Adverse events were graded on a scale of 1-5 (ie, mild, moderate, severe, life-threatening, or death) according to the Common Terminology Criteria for Adverse Events grading scale (version 4.3). Exploratory analyses were quantification of B-cell CD19 receptor occupancy, plasmablast, total B-cell and CD4+ cytotoxic T-cell count by flow cytometry, and immunoglobulin concentrations by nephelometry. This study is registered with ClinicalTrials.gov, NCT02725476.

FINDINGS

Between Feb 24, 2016, and Dec 21, 2016, we enrolled 15 patients. The median age was 63 years (IQR 52-65). Ten (67%) of 15 patients were male, five (33%) were female, and 12 (80%) were White. At baseline, 12 (80%) of 15 patients had an elevated median serum IgG4 concentration of 220 mg/dL (IQR 124-441), and the median IgG4-related disease responder index score was 12 (IQR 7-13). 12 (80%) of 15 patients achieved the primary endpoint (ie, primary responders), 14 (93%) were defined as responders. Reductions from baseline in serum B cells and plasmablasts were observed following treatment with obexelimab. However, in most patients with follow-up data, serum B cells recovered to 75% of baseline concentrations within 42 days of the final obexelimab dose. 13 (87%) of 15 patients reported adverse events, one of which (an infusion reaction) resulted in treatment discontinuation.

INTERPRETATION

All patients except for one had clinical responses to obexelimab treatment. Both reductions in circulating B cells without evidence of apoptosis during obexelimab treatment and their rapid rebound after treatment discontinuation suggest that obexelimab might lead to B-cell sequestration in lymphoid organs or the bone marrow. These results support the continued development of obexelimab for the treatment of IgG4-related disease.

FUNDING

Xencor, Zenas BioPharma, National Institute of Arthritis and Musculoskeletal and Skin Diseases, and National Institute of Allergy and Infectious Diseases.

An optimal antitumor response by a novel CEA/CD3 bispecific antibody for colorectal cancers

BACKGROUND

CD3-based bispecific T cell engagers (bsTCEs) are one of the most promising bispecific antibodies for effective cancer treatments. To elicit target-specific T cell-mediated cytotoxicity, these bsTCEs contain at least one binding unit directed against a tumor antigen and another binding unit targeting CD3 in T cell receptor complex. Development of CD3-based bsTCEs, however, has been severely hampered by dose-limiting toxicities due to cytokine release syndrome. To address this limitation, we developed a novel functionally trivalent T cell engager (t-TCE) antibody containing affinity-reduced CD3 binding unit positioned to ensure monovalent CD3 engagement, in combination with bivalent tumor antigen binding of carcinoembryonic antigen (CEA).

METHODS

We modeled the variable region of anti-CD3 in the complementarity-determining regions of the heavy chain and obtained CD3 binders with reduced binding affinity. Two optimized versions CEA/CD3-v1 and CEA/CD3-v2 were identified and generated in tetravalent format, characterized and compared in vitro and in vivo for functional activity.

RESULTS

Our lead candidate, CEA/CD3-v2, demonstrated subnanomolar binding and picomolar potency against a panel of CEA-expressing cancer cell lines. In addition, we detected reduced T cell cytokine release with potent cytotoxic activity. Our t-TCE CEA/CD3-v2 molecule demonstrated strong antitumor effect in a dose-dependent manner in human peripheral blood mononuclear cell (PBMC) xenograft model. Furthermore, combination of CEA/CD3-v2 with atezolizumab provided synergistic antitumor effect.

CONCLUSIONS

Because of its effective tumor cell killing in vitro and in vivo with reduced cytokine release, CEA/CD3 bsTCE may greatly benefit in CEA-positive cancer immunotherapy.

IκB kinase β (IKBKB) mutations in lymphomas that constitutively activate canonical nuclear factor κB (NFκB) signaling

Somatic mutations altering lysine 171 of the IKBKB gene that encodes (IKKβ), the critical activating kinase in canonical (NFκB) signaling, have been described in splenic marginal zone lymphomas and multiple myeloma. Lysine 171 forms part of a cationic pocket that interacts with the activation loop phosphate in the activated wild type kinase. We show here that K171E IKKβ and K171T IKKβ represent kinases that are constitutively active even in the absence of activation loop phosphorylation. Predictive modeling and biochemical studies establish why mutations in a positively charged residue in the cationic pocket of an activation loop phosphorylation-dependent kinase result in constitutive activation. Transcription activator-like effector nuclease-based knock-in mutagenesis provides evidence from a B lymphoid context that K171E IKKβ contributes to lymphomagenesis.

[Determination of lead in whole blood by graphite furnace atomic absorption spectrometry with matrix modifier and L'vov platform]

Lead in whole blood has been determined by graphite furnace atomic absorption spectrometry with matrix modifier and L'vov platform. It's found that addition of the mixture solution of 0.6% NH4H2PO4 and 0.4% NH4NO3 as matrix modifier, the ash temperature will increase up to 900 degrees C. 750 degrees C is practically used for ash temperature. D2 lamp is used for background correction. Lead in whole blood was directly determined after addition of 0.3% Triton X-100 without digestion. The analytical results of six whole samples is satisfactory. The recoveries are 93%-106%. The relative standard deviations are 3%-7%. The sensitivity of characteristic mass is 6.0 pg/1%.