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.

Safety, pharmacokinetics, and biologic activity of pateclizumab, a novel monoclonal antibody targeting lymphotoxin α: results of a phase I randomized, placebo-controlled trial.

INTRODUCTION: Pateclizumab (MLTA3698A) is a humanized mAb against lymphotoxin α (LTα), a transiently expressed cytokine on activated B and T cells (Th1, Th17), which are implicated in rheumatoid arthritis (RA) pathogenesis. This study was conducted to assess the safety, tolerability, < NOTE: For clarity and per AMA/S-W Style, please restore the use of Oxford/serial commas (ie: David likes vanilla, strawberry, and chocolate ice cream) throughout. and biologic activity of single and multiple doses of intravenous (IV) or subcutaneous (SC) pateclizumab in RA patients. METHODS: The single ascending dose (SAD) phase in patients with stable RA consisted of six cohorts (4:1 active:placebo at 0.3 mg/kg IV, 1.0 mg/kg IV, 1.0 mg/kg SC, 3.0 mg/kg IV, 3.0 mg/kg SC, and 5.0 mg/kg IV; n = 5/cohort). In the multiple ascending dose (MAD) phase, patients with prespecified RA disease activity received three doses of pateclizumab or placebo (4:1) every 2 weeks (1.0 mg/kg SC, n = 10; 3.0 mg/kg SC, n = 20; or 5.0 mg/kg IV, n = 5). Safety and tolerability were assessed throughout, and clinical activity was determined after three doses (Week 6). RESULTS: We observed no serious adverse events (AEs) or dose-limiting toxicities, and the majority of AEs were mild to moderate. The pharmacokinetic profiles were linear, and clearance was independent of dose. Reductions in levels of serum CXCL13 were observed, supporting the biologic activity of pateclizumab on the LTα pathway. Patients receiving pateclizumab in the 3.0 mg/kg MAD group (3.0 mg/kg SC) demonstrated ACR20, ACR50, and ACR70 response rates at week 6 of 75%, 56% and 25%, respectively, compared with 57%, 29%, and 0% in the placebo group. The median Disease Activity Score in 28 joints, C-reactive protein, reduction was 28% for pateclizumab, versus 8.4% for placebo. CONCLUSIONS: Pateclizumabwas generally well-tolerated in RA patients. Preliminary evidence of clinical activity was observed in active RA patients at the dose level targeted for clinical effect.

Modified representational difference analysis: isolation of differentially expressed mRNAs from rare cell populations.

Representational difference analysis of cDNAs (cDNA-RDA) is a sensitive subtractive hybridization technique capable of isolating rare mRNAs differentially expressed in two cell populations. cDNA-RDA can detect sequences represented at 0.0001% in the starting mRNA. By using reverse transcriptase polymerase chain reaction (PCR), cDNA-RDA also lends itself to studies in which samples are derived from limited numbers of cells. Standard cDNA-RDA protocols depend upon the presence of specific restriction enzyme sites in each cDNA, typically enzymes with four base recognition sequences. These sites are used to reduce the cDNA size range and provide primer sites for subsequent PCR amplification. Consequently, transcripts containing fewer than two of the chosen restriction sites are undetectable by cDNA-RDA. We have developed a restriction enzyme site-independent cDNA-RDA protocol called modified RDA (MRDA). We constructed MRDA test sequences from random hexamer-primed cDNA, thereby increasing the representation of mRNAs which are excluded by cDNA-RDA protocols. MRDA is also more efficient than cDNA-RDA at removing highly expressed housekeeping genes during the subtractive hybridization process, thereby allowing more efficient isolation of preferentially expressed mRNAs. Using MRDA, we isolated cDNAs differentially expressed between limited numbers of human CD4(+) naive and memory T lymphocyte subsets and skin- and gut-homing memory T cell subsets.