William Hagopian, MD, PhD, Robert J. Ferry Jr, MD, Nicole Sherry, MD, David Carlin, PhD, Ezio Bonvini, MD, Syd Johnson, PhD, Kathryn E. Stein, PhD, Scott Koenig, MD, PhD Anastasia G. Daifotis, MD, Kevan C. Herold, MD, Johnny Ludvigsson, MD, PhD for the Protégé Trial Investigators* Pacific Northwest Diabetes Research Institute, Seattle, WA; the Division of Pediatric Endocrinology and Metabolism, Le Bonheur Children’s Hospital and University of Tennessee Health Science Center, Memphis, TN; the Massachusetts General Hospital, Boston, MA; MacroGenics, Rockville, MD; Departments of Immunobiology and Internal Medicine, Yale University, New Haven, CT; and the Division of Pediatrics, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping University, Linköping, Sweden *A list of all investigators appears online in the Appendix

Protégé was a phase 3, randomized, double-blind, parallel, placebo-controlled 2-year study of three intravenous teplizumab dosing regimens, administered daily for 14 days at baseline and again after 26 weeks, in new-onset type 1 diabetes. We sought to determine efficacy and safety of teplizumab immunotherapy at 2 years and to identify characteristics associated with therapeutic response. Of 516 randomized patients, 513 were treated, and 462 completed 2 years of follow-up. Teplizumab (14-day full-dose) reduced the loss of C-peptide mean area under the curve (AUC), a prespecified secondary end point, at 2 years versus placebo. In analyses of prespecified and post hoc subsets at entry, U.S. residents, patients with C-peptide mean AUC >0.2 nmol/L, those randomized ≤6 weeks after diagnosis, HbA1c <7.5% (58 mmol/mol), insulin use <0.4 units/kg/day, and 8–17 years of age each had greater teplizumab-associated C-peptide preservation than their counterparts. Exogenous insulin needs tended to be reduced versus placebo. Antidrug antibodies developed in some patients, without apparent change in drug efficacy. No new safety or tolerability issues were observed during year 2. In summary, anti-CD3 therapy reduced C-peptide loss 2 years after diagnosis using a tolerable dose.

AVEO Pharmaceuticals, Cambridge, MA 02139. Novartis Institute for Biomedical Research, Cambridge, MA 02139. Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229-3039. Independent Consultant, Gettysburg, PA 17325. Independent Consultant, Natick, MA 01760. To whom correspondence should be addressed at Biologics Research and Development, Genzyme Corporation, 5 Mountain Road, Framingham, MA 01701-9322. Fax: (508) 661-1854. E-mail: laura.andrews@genzyme.com.

Fc receptors are a critical component of the innate immune system responsible for the recognition of cross-linked antibodies and the subsequent clearance of pathogens. However, in autoimmune diseases, these receptors play a role in the deleterious action of self-directed antibodies and as such are candidate targets for treatment. GMA161 is an aglycosyl, humanized version of the murine antibody 3G8 that targets the human low-affinity Fcγ receptor III (CD16). As CD16 expression and sequence have high species specificity, preclinical assessments were conducted in mice transgenic for both isoforms of human CD16, CD16A, and CD16B. This transgenic mouse model was useful in transitioning into phase I clinical trials, as it generated positive efficacy data in a relevant disease model and an acceptable single-dose safety profile. However, when GMA161 or its murine parent 3G8 were dosed repeatedly in transgenic mice having both human CD16 isoforms, severe reactions were observed that were not associated with significant cytokine release, nor were they alleviated by antihistamine administration. Prophylactic dosing with an inhibitor of platelet-activating factor (PAF), however, completely eliminated all signs of hypersensitivity. These findings suggest that (1) GMA161 elicits a reaction that is target dependent, (2) immunogenicity and similar adverse reactions were observed with a murine version of the antibody, and (3) the reaction is driven by the atypical hypersensitivity pathway mediated by PAF.

Background Findings of small studies have suggested that short treatments with anti-CD3 monoclonal antibodies that are mutated to reduce Fc receptor binding preserve beta-cell function and decrease insulin needs in patients with recent-onset type 1 diabetes. In this phase 3 trial, we assessed the safety and efficacy of one such antibody, teplizumab.Methods In this 2-year trial, patients aged 8-35 years who had been diagnosed with type 1 diabetes for 12 weeks or fewer were enrolled and treated at 83 clinical centres in North America, Europe, Israel, and India. Participants were allocated (2:1:1:1 ratio) by an interactive telephone system, according to computer-generated block randomisation, to receive one of three regimens of teplizumab infusions (14-day full dose, 14-day low dose, or 6-day full dose) or placebo at baseline and at 26 weeks. The Protege study is still underway, and patients and study staff remain masked through to study closure. The primary composite outcome was the percentage of patients with insulin use of less than 0.5 U/kg per day and glycated haemoglobin A(1c) (HbA(1c)) of less than 6-5% at 1 year. Analyses included all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov, number NCT00385697.Findings 763 patients were screened, of whom 516 were randomised to receive 14-day full-dose teplizumab (n=209), 14-day low-dose teplizumab (n=102), 6-day full-dose teplizumab (n=106), or placebo (n=99). Two patients in the 14-day full-dose group and one patient in the placebo group did not start treatment, so 513 patients were eligible for efficacy analyses. The primary outcome did not differ between groups at 1 year: 19.8% (41/207) in the 14-day full-dose group; 13.7% (14/102) in the 14-day low-dose group; 20.8% (22/106) in the 6-day full-dose group; and 20.4% (20/98) in the placebo group. 5% (19/415) of patients in the teplizumab groups were not taking insulin at 1 year, compared with no patients in the placebo group at 1 year (p=0.03). Across the four study groups, similar proportions of patients had adverse events (414/417 [99%] in the teplizumab groups vs 98/99 [99%] in the placebo group) and serious adverse events (42/417 [10%] vs 9/99 [9%]). The most common clinical adverse event in the teplizumab groups was rash (220/417 [53%] vs 20/99 [20%] in the placebo group).Interpretation Findings of exploratory analyses suggest that future studies of immunotherapeutic intervention with teplizumab might have increased success in prevention of a decline in beta-cell function (measured by C-peptide) and provision of glycaemic control at reduced doses of insulin if they target patients early after diagnosis of diabetes and children.

Human CD32B (Fc gamma RIIB), the low-affinity inhibitory Fc gamma receptor (Fc gamma R), is highly homologous in its extracellular domain to CD32A (Fc gamma RIIA), an activating Fc gamma R. Available monoclonal antibodies (mAb) against the extracellular region of CD32B recognize both receptors. Through immunization of mice transgenic for human CD32A, we generated a set of antibodies specific for the extracellular region of CD32B with no cross-reactivity with CD32A, as determined by enzyme-linked immunosorbent assay and surface plasmon resonance with recombinant CD32A and CD32B, and by fluorescence-activated cell sorting analysis of CD32 transfectants. A high-affinity mAb, 2B6, was used to explore the expression of CD32B by human peripheral blood leucocytes. While all B lymphocytes expressed CD32B, only a fraction of monocytes and almost no polymorphonuclear cells stained with 2B6. Likewise, natural killer cells, which express CD32C, a third CD32 variant, did not react with 2B6. Immune complexes co-engage the inhibitory receptor with activating Fc gamma receptors, a mechanism that limits cell responses. 2B6 competed for immune complex binding to CD32B as a monomeric Fab, suggesting that it directly recognizes the Fc-binding region of the receptor. Furthermore, when co-ligated with an activating receptor, 2B6 triggered CD32B-mediated inhibitory signalling, resulting in diminished release of inflammatory mediators by Fc epsilon RI in an in vitro allergy model or decreased proliferation of human B cells induced by B-cell receptor stimulation. These antibodies form the basis for the development of investigational tools and therapeutics with multiple potential applications, ranging from adjuvants in Fc gamma R-mediated responses to the treatment of allergy and autoimmunity.

Bioanalytical assessments of anti-drug antibodies (ADAs) provide an understanding of the immunogenicity of biological drug molecules. The potential to induce ADAs after treatment with biologics is a safety issue that has become an important consideration in the development of biologics and a critical aspect of regulatory filings. US and European regulatory agencies are recommending that sponsors study immunogenicity using a risk-based approach, encouraging sponsors to formulate and implement their own risk management plans and to conduct discussions with the agencies when necessary. It follows from this that the greater the safety risks of ADAs, the more diligently one should clarify the immunogenicity of the product. Here we propose a general strategy to broadly assign immunogenicity risk levels to biological drug products, and present risk level–based 'fit-for-purpose' bioanalytical schemes for the investigations of treatment-related ADAs in clinical and nonclinical studies.

Viral safety is a predominant concern for monoclonal antibodies (mAbs) and other recombinant proteins (RPs) with pharmaceutical applications. Certain commercial purification modules, such as nanofiltration and low-pH inactivation, have been observed to reliably clear greater than 4 log(10) of large enveloped viruses, including endogenous retrovirus. The concept of "bracketed generic clearance" has been proposed for these steps if it could be prospectively demonstrated that viral log(10) reduction value (LRV) is not impacted by operating parameters that can vary, within a reasonable range, between commercial processes. In the case of low-pH inactivation, a common step in mAb purification processes employed after protein A affinity chromatography, these parameters would include pH, time and temperature of incubation, the content of salts, protein concentration, aggregates, impurities, model protein pI, and buffer composition. In this report, we define bracketed generic clearance conditions, using a prospectively defined bracket/matrix approach, where low-pH inactivation consistently achieves >or=4.6 log(10) clearance of xenotropic murine leukemia virus (X-MLV), a model for rodent endogenous retrovirus. The mechanism of retrovirus inactivation by low-pH treatment was also investigated.

Although thymus-matured T cells are not necessary for in vivo B cell responses to a class of antigens designated T-independent (TI) 1 (1, 2), we wished to determine whether T cells could influence the nature of the antibody produced. It was our hypothesis that in a TI antigen system in which there is no obligate need for carrierspecific helper T cell triggering signals, T cells may still exert subtle regulatory effects on the B cell antibody response via a distinct population of Ig-specific regulatory cells (3-9). If this were indeed the case, such a system might be ideal for studying the regulatory effects of Ig-speeific T cells independently of carrier-specific T cells. The characteristics of Ig-specific T cell interactions with B cells could thus be elucidated and compared with the known characteristics of carrier-specific T cell-B cell interactions. In testing for T cell influences on B cell responses to TI antigens, our emphasis has been to search for possible effects of isotype-specific T cells. Our approach has been to determine whether T cells could differentially regulate the levels of the various isotypes of antibody made by the B cell population responding to a subset of TI antigens, designated type 2 TI (TI-2) antigens. These antigens are characterized by their lack of polyclonal activating activity and their inability to stimulate B cells from neonatal mice or mice with the CBA/N immune defect (10). We here demonstrate that the in vivo B cell response to TI-2 antigens can be influenced by T lymphocytes and that this influence is restricted to only some of the Ig isotypes produced, namely the IgG2a, and, to a lesser extent, the IgG2b subclasses.

Previous studies demonstrated that the diversity of the antibody response of mice to the inulin (In) determinant of bacterial levan is regulated by the gene Spectrotype Regulation 1 ( Sr1). BALB/c mice produce a monoclonal anti-In response as shown by isoelectric focusing analysis. In contrast, the anti-In antibody response of (BALB/cxC57BL/6)F1 mice is significantly more heterogeneous. We performed a backcross and a genome-wide scan with microsatellite markers and found that Sr1 is tightly linked to D14Mit121 on chromosome (Chr) 14. This location for Sr1 was supported by analysis of CXB Recombinant Inbred strains. We further confirmed this by finding that the Chr 14 congenic mouse strain B6.C-H8 lacks the C57BL/6 allele of the Sr1 gene, indicating that Sr1 is located in the segment of Chr 14 replaced with BALB/c donor DNA. These data place Sr1 near to or coincident with the Tcra/Tcrd T-cell receptor gene complex and suggest a role for T cells in diversifying the anti-In response.

Using current monoclonal antibody technology one can now produce a humanized antibody to virtually any target antigen that can be identified. Consequently, one would expect there to be more approved monoclonal antibody products. Inadequate product development at both the preclinical and clinical stages has contributed to the overall lack of success. This article discusses some of the obstacles to successful product development and offers suggestions to overcoming them. The key to monoclonal antibody development, as with other biological products, is understanding the properties of the product itself, to have some proof of concept before embarking on clinical studies, and to adequately design and power the pivotal trial.

Our previous studies of 102 mAb from mice injected with bacterial levan (BL), a beta(2-->6) linked polyfructosan with beta(2-->1) branch points (inulin determinant, In) showed that BALB/c and CBA/Ca mAb differed in VH and VL gene family usage and fine specificity. We now show that BALB/c and CBA/Ca mAb used different VHJ606 germ-line genes in response to BL: V14A in BALB/c and a previously unidentified gene in CBA/Ca. CBA/Ca mice were found to lack the BALB/c V14A gene. Also, we have compared the responses to one (primary, 1 degree) or two (secondary, 2 degrees) injections of polysaccharide. The secondary BALB/c anti-BL panel has been expanded to a total of 22 mAb, and we report here the isotype, fine specificity, and VH/VL usage of the new mAb. Eight of nine primary BALB/c In-binding mAb were germ-line, whereas both secondary BALB/c In-binding mAb that were sequenced differed from the BALB/c germ-line gene V14A. Germ-line primary mAb were low avidity whereas all five secondary mAb and the one non-germ-line primary were high avidity. There was also a repertoire shift from approximately 90% VHJ606/V kappa 11 in primary mAb to only 50% in secondary mAb (p = 0.002). The data presented provide evidence that avidity maturation and repertoire shifts, features usually associated with a memory response to thymus-dependent Ags, also can occur in response to a second immunization with a thymus-independent type 2 polysaccharide Ag.

Mice with the x-linked immunodeficiency mutation (xid) are unresponsive to polysaccharide antigens, lack a subset of B cells, and have low serum IgM (2–20% of normal) and IgG3 (3% of normal). Because of the disproportionate reduction of IgG3, the ability of B cells from xid mice to switch to γ3 was examined. Switching was indirectly measured by comparing IgG3 production and Cγ3 mRNA steady state levels of purified B cells activated to switch to IgG3 by LPS in bulk culture. Direct measurement of switching was achieved by enumerating on a percentage basis switched cells in a filter disk culture assay and by FACS analysis. In both bulk culture and the filter disk assay, switching to γ3 was equivalent between xid and non-xid B cells.

The principle that infants can be protected from invasive diseases caused by encapsulated organisms has been proved with the introduction of Haemophilus influenzae type b conjugate vaccines. The use of glycoconjugates to implement some of the goals of the Children's Vaccine Initiative requires a clear delineation of the chemical and immunological specifications for optimal vaccines.