Development and validation of an ELISA method for quantification of the anti-HER3 antibody HMBD-001 in human serum.

Background: HMBD-001 is an IgG1 humanized monoclonal antibody specifically targeting HER3, a receptor highly expressed on cancer cells in certain tumors. A bioanalytical method was required to quantify HMBD-001 in human serum, with high selectivity and without interference from HER3. Methods and results: A bridging ELISA using an anti-idiotypic monoclonal capture and detection was developed and validated for quantitative measurement of HMBD-001 in human serum. The assay is sensitive, with a lower limit of quantification of 250 ng/ml, has a broad dynamic range of 250-7000 ng/ml HMBD-001, and exhibits excellent precision and overall accuracy. Conclusion: We have developed and validated a sensitive and selective method for measuring HMBD-001 in human serum. This assay is now being used in a clinical trial setting.

Anti-IL-7 receptor α monoclonal antibody (GSK2618960) in healthy subjects - a randomized, double-blind, placebo-controlled study.

AIM: Interleukin (IL)-7 signalling modulates T cell activity and is implicated in numerous autoimmune diseases. The present study investigated the safety, pharmacokinetics, target engagement, pharmacodynamics and immunogenicity of GSK2618960, an IL-7 receptor-α subunit (CD127) monoclonal antibody. METHODS: A double-blind (sponsor-unblind) study of a single intravenous infusion of either GSK2618960 (0.6 mg kg-1 or 2.0 mg kg-1 ) or placebo was carried out in 18 healthy subjects over 24 weeks. RESULTS: GSK2618960 was well tolerated; there were no serious or significant adverse events. The observed half-life was 5 (±1) days (2.0 mg kg-1 ), with nonlinear pharmacokinetics. Full receptor occupancy (>95%) was observed until day 8 (0.6 mg kg-1 ) and day 22 (2.0 mg kg-1 ). Maximal inhibition of IL-7-mediated signal transducer and activator of transcription 5 (STAT5) phosphorylation was observed in 5/6 subjects until day 22 (2.0 mg kg-1 ). Mean circulating IL-7 and soluble receptor (CD127) levels were increased above baseline during days 2 and 15 (0.6 mg kg-1 ) and days 2 and 22 (2.0 mg kg-1 ). No meaningful changes were observed in absolute numbers or proportions of immune cell populations or inflammatory cytokine profiles (IL-6, tumour necrosis factor-α, interferon-γ, IL-2). Persistent antidrug antibodies (ADAs) were detected in 5/6 subjects administered a dose of 0.6 mg kg-1 (neutralizing in 2/6) and in 6/6 subjects administered 2.0 mg kg-1 (neutralizing in 5/6). CONCLUSION: GSK2618960 was well tolerated and blocked IL-7 receptor signalling upon full target engagement. Although there was no discernible impact on peripheral T cell subsets in healthy subjects, GSK2618960 may effectively modulate the autoinflammatory activity of pathogenic T cells in diseased tissue. A relatively short half-life is likely the result of target-mediated rather than ADA-mediated clearance.

Evaluation of B cell maturation antigen as a target for antibody drug conjugate mediated cytotoxicity in multiple myeloma.

B-cell maturation antigen (BCMA, also termed TNFRSF17) is an attractive therapeutic target due to its restricted expression on normal and malignant plasma cells (PC). GSK2857916 (or J6M0-MMAF) is a BCMA-specific antibody conjugated to the microtubule-disrupting agent monomethyl auristatin F (MMAF) via a protease-resistant linker. To evaluate the clinical potential of this agent, tumour cells from seventy multiple myeloma (MM) patients were assessed for BCMA expression by immunohistochemistry and flow cytometry. All patients tested expressed BCMA, at varying levels, and both surface and intracellular expression were observed. BCMA expression is maintained through relapse, extramedullary spread and in residual disease post therapy. BCMA levels may also be prognostically useful as higher levels of BCMA were associated with poorer outcomes, even taking into account genetic risk. We observed rapid internalization of surface BCMA and newly expressed protein by 1 h, suggesting a mechanism for J6M0-MMAF activity even with low surface antigen. J6M0-MMAF mediated cytotoxicity of MM cells varied with dose and antigen levels, with clonogenic progenitors killed at lower doses than mature cells. In comparison, J6M0-MMAF killing of primary CD138(+) myeloma cells occurred with slower kinetics. Our observations support BCMA to be a promising therapeutic target in MM for novel therapies such as J6M0-MMAF.

B-cell depletion attenuates white and gray matter pathology in marmoset experimental autoimmune encephalomyelitis.

This study investigated the effect of CD20-positive B-cell depletion on central nervous system (CNS) white and gray matter pathology in experimental autoimmune encephalomyelitis in common marmosets, a relevant preclinical model of multiple sclerosis. Experimental autoimmune encephalomyelitis was induced in 14 marmosets by immunization with recombinant human myelin oligodendrocyte glycoprotein in complete Freund adjuvant. At 21 days after immunization, B-cell depletion was achieved by weekly intravenous injections of HuMab 7D8, a human-anti-human CD20 antibody that cross-reacts with marmoset CD20. In vivo magnetic resonance imaging showed widespread brain white matter demyelination in control marmosets that was absent in CD20 antibody-treated marmosets. High-contrast postmortem magnetic resonance imaging showed white matter lesions in 4of the 7 antibody-treated marmosets, but these were significantly smaller than those in controls. The same technique revealed gray matter lesions in 5 control marmosets, but none in antibody-treated marmosets. Histologic analysis confirmed that inflammation, demyelination, and axonal damage were substantially reduced in brain, spinal cord, and optic nerves of CD20 antibody-treated marmosets. In conclusion, CD20-postive B-cell depletion by HuMab 7D8 profoundly reduced the development of both white and gray matter lesions in the marmoset CNS. These data underline the central role of B cells in CNS inflammatory-demyelinating disease.

Late B cell depletion with a human anti-human CD20 IgG1κ monoclonal antibody halts the development of experimental autoimmune encephalomyelitis in marmosets.

Depletion of CD20(+) B cells has been related to reduced clinical activity in relapsing-remitting multiple sclerosis. The underlying mechanism is not understood, because serum IgG levels were unaltered by the treatment. We report the effect of late B cell depletion on cellular and humoral immune mechanisms in a preclinical multiple sclerosis model (i.e., experimental autoimmune encephalomyelitis [EAE] in the common marmoset). We used a novel human anti-human CD20 IgG1κ mAb (HuMab 7D8) that cross-reacts with marmoset CD20. EAE was induced in 14 marmosets by immunization with recombinant human myelin oligodendrocyte glycoprotein (MOG) in CFA. After 21 d, B cells were depleted in seven monkeys by HuMab 7D8, and seven control monkeys received PBS. The Ab induced profound and long-lasting B cell depletion from PBMCs and lymphoid organs throughout the observation period of 106 d. Whereas all of the control monkeys developed clinically evident EAE, overt neurologic deficits were reduced substantially in three HuMab 7D8-treated monkeys, and four HuMab 7D8-treated monkeys remained completely asymptomatic. The effect of HuMab 7D8 was confirmed on magnetic resonance images, detecting only small lesions in HuMab 7D8-treated monkeys. The infusion of HuMab 7D8 arrested the progressive increase of anti-MOG IgG Abs. Although CD3(+) T cell numbers in lymphoid organs were increased, their proliferation and cytokine production were impaired significantly. Most notable were the substantially reduced mRNA levels of IL-7 and proinflammatory cytokines (IL-6, IL-17A, IFN-γ, and TNF-α). In conclusion, B cell depletion prevents the development of clinical and pathological signs of EAE, which is associated with impaired activation of MOG-reactive T cells in lymphoid organs.