Franklin Fuh

CS1, a Potential New Therapeutic Antibody Target for the Treatment of Multiple Myeloma

Purpose: We generated a humanized antibody, HuLuc63, which specifically targets CS1 (CCND3 subset 1, CRACC, and SLAMF7), a cell surface glycoprotein not previously associated with multiple myeloma. To explore the therapeutic potential of HuLuc63 in multiple myeloma, we examined in detail the expression profile of CS1, the binding properties of HuLuc63 to normal and malignant cells, and the antimyeloma activity of HuLuc63 in preclinical models. Experimental Design: CS1 was analyzed by gene expression profiling and immunohistochemistry of multiple myeloma samples and numerous normal tissues. HuLuc63-mediated antimyeloma activity was tested in vitro in antibody-dependent cellular cytotoxicity (ADCC) assays and in vivo using the human OPM2 xenograft model in mice. Results: CS1 mRNA was expressed in >90% of 532 multiple myeloma cases, regardless of cytogenetic abnormalities. Anti-CS1 antibody staining of tissues showed strong staining of myeloma cells in all plasmacytomas and bone marrow biopsies. Flow cytometric analysis of patient samples using HuLuc63 showed specific staining of CD138+ myeloma cells, natural killer (NK), NK-like T cells, and CD8+ T cells, with no binding detected on hematopoietic CD34+ stem cells. HuLuc63 exhibited significant in vitro ADCC using primary myeloma cells as targets and both allogeneic and autologous NK cells as effectors. HuLuc63 exerted significant in vivo antitumor activity, which depended on efficient Fc-CD16 interaction as well as the presence of NK cells in the mice. Conclusions: These results suggest that HuLuc63 eliminates myeloma cells, at least in part, via NK-mediated ADCC and shows the therapeutic potential of targeting CS1 with HuLuc63 for the treatment of multiple myeloma.

Anti-CD22-MCC-DM1: An antibody-drug conjugate with a stable linker for the treatment of non-Hodgkin's lymphoma

Antibody-drug conjugates (ADCs) are potent cytotoxic drugs linked to antibodies through chemical linkers, and allow specific targeting of drugs to neoplastic cells. The expression of CD22 is limited to B-cells, and we show that CD22 is expressed on the vast majority of non-Hodgkins lymphomas (NHLs). An ideal target for an ADC for the treatment of NHL would have limited expression outside the B-cell compartment and be highly effective against NHL. We generated an ADC consisting of a humanized anti-CD22 antibody conjugated to the anti-mitotic agent maytansine with a stable linker (anti-CD22-MCC-DM1). Anti-CD22-MCC-DM1 was broadly effective in in vitro killing assays on NHL B-cell lines. We did not find a strong correlation between in vitro potency and CD22 surface expression, internalization of ADC or sensitivity to free drug. We show that anti-CD22-MCC-DM1 was capable of inducing complete tumor regression in NHL xenograft mouse models. Further, anti-CD22-MCC-DM1 was well tolerated in cynomolgus monkeys and substantially decreased circulating B-cells as well as follicle size and germinal center formation in lymphoid organs. These results suggest that anti-CD22-MCC-DM1 has an efficacy, safety and pharmacodynamic profile that support its use as a treatment for NHL.

A humanized monoclonal antibody targeting the β7 integrin selectively blocks intestinal homing of T lymphocytes

BACKGROUND AND PURPOSE rhuMAb Beta7 is a humanized anti‐human β7 monoclonal antibody currently in phase I in inflammatory bowel disease. rhuMAb Beta7 binds the β7 subunit of the integrins α4β7 and αEβ7, blocking interaction with their ligands. These integrins play key roles in immune cell homing to and retention in mucosal sites, and are associated with chronic inflammatory diseases of the gastrointestinal tract. The goal of this study was to evaluate the mucosal specificity of rhuMAb Beta7.

DCDT2980S, an Anti-CD22-Monomethyl Auristatin E Antibody–Drug Conjugate, Is a Potential Treatment for Non-Hodgkin Lymphoma

Antibody–drug conjugates (ADC), potent cytotoxic drugs linked to antibodies via chemical linkers, allow specific targeting of drugs to neoplastic cells. We have used this technology to develop the ADC DCDT2980S that targets CD22, an antigen with expression limited to B cells and the vast majority of non-Hodgkin lymphomas (NHL). DCDT2980S consists of a humanized anti-CD22 monoclonal IgG1 antibody with a potent microtubule-disrupting agent, monomethyl auristatin E (MMAE), linked to the reduced cysteines of the antibody via a protease cleavable linker, maleimidocaproyl-valine-citrulline-p-aminobenzoyloxycarbonyl (MC-vc-PAB). We describe the efficacy, safety, and pharmacokinetics of DCDT2980S in animal models to assess its potential as a therapeutic for the treatment of B-cell malignancies. We did not find a strong correlation between in vitro or in vivo efficacy and CD22 surface expression, nor a correlation of sensitivity to free drug and in vitro potency. We show that DCDT2980S was capable of inducing complete tumor regression in xenograft mouse models of NHL and can be more effective than rituximab plus combination chemotherapy at drug exposures that were well tolerated in cynomolgus monkeys. These results suggest that DCDT2980S has an efficacy, safety, and pharmacokinetics profile that support potential treatment of NHL. Mol Cancer Ther; 12(7); 1255–65. ©2013 AACR.

Mass cytometry panel optimization through the designed distribution of signal interference

Mass cytometry is capable of measuring more than 40 distinct proteins on individual cells making it a promising technology for innovating biomarker discovery. However, in order for this potential to be fully realized, best practices in panel design need to be further defined in order to achieve consistency and reproducibility in data analysis. Of particular importance are controls that reveal, and panel design principles that mitigate the effects of signal interference or overlap. We observed a disparity between the staining profiles of two noncompeting anti‐ integrin β7 mAbs and hypothesized that signal interference was responsible. A mass‐minus‐one (MMO) control was applied and demonstrated that signal overlap caused the perceived interclonal discrepancy in β7 expression. Panel redesign in consideration of mass‐cytometry specific interference dynamics dramatically improved concordance between both mAbs by redistributing background signals caused by overlap. These studies visualize how signal overlap can complicate mass cytometry data interpretation and demonstrate how the rational distribution of interference can greatly improve panel design and data quality.

Pharmacokinetic and Pharmacodynamic Modeling of Serum Etrolizumab and Circulating β7 Receptor Occupancy in Patients With Ulcerative Colitis

Etrolizumab, a humanized monoclonal antibody, specifically binds to the β7 subunit of the heterodimeric integrins α4β7 and αEβ7. Pharmacokinetic (PK) and pharmacodynamic (PD) data were collected from an etrolizumab phase 1 trial in patients with moderate to severe ulcerative colitis (UC). We developed a mechanism‐based model to simultaneously describe the kinetics of serum etrolizumab concentration and free β7 receptors on circulating intestinal‐homing CD4+ T lymphocytes. Included in the analysis were 38 phase 1 UC patients who received single or 3 monthly doses of etrolizumab intravenously or subcutaneously across a dose range of 0.3 to 10 mg/kg. A quasi–steady‐state target‐mediated drug disposition model was developed to describe the dynamic interaction between serum etrolizumab concentration and free β7 receptors on intestinal‐homing CD4+ T lymphocytes in UC patients. The time profiles of serum etrolizumab and absolute counts of β7+ lymphocytes (expressed as percentage of baseline level) were well described by the quasi–steady‐state target‐mediated drug disposition model. The model was able to characterize the maximum drug occupancy of β7 receptors on intestinal‐homing CD4+ T lymphocytes and the concentration‐dependent duration of occupancy. The 90% effective concentration for etrolizumab to saturate the β7 receptors on intestinal homing CD4+ T cells was 1.3 μg/mL. PK and PD profiles predicted by the model were consistent with observations from a subsequent phase 2 study. In conclusion, an integrated PK/PD model developed in this analysis reasonably described serum etrolizumab PK profiles and the relationship between PK and PD (free β7 receptors on circulating intestinal‐homing CD4+ T lymphocytes) in UC patients.

Anti-CD22 and anti-CD79b antibody-drug conjugates preferentially target proliferating B cells.

CD22 and CD79b are cell‐surface receptors expressed on B‐cell‐derived malignancies such as non‐Hodgkins lymphoma (NHL). An anti‐mitotic agent, monomethyl auristatin E, was conjugated to anti‐CD22 and anti‐CD79b antibodies to develop target‐specific therapies for NHL. The mechanism of action (MOA) and pharmacological and pharmacokinetic (PK) profiles of these antibody‐drug conjugates (ADCs) were investigated in cynomolgus monkeys.