Microphysiological systems (MPS) are making advances to provide more standardized and predictive physiologically relevant responses to test articles in living tissues and organ systems. The excitement surrounding the potential of MPS to better predict human responses to medicines and improving clinical translation is overshadowed by their relatively slow adoption by the pharmaceutical industry and regulators. Collaboration between multiorganizational consortia and regulators is necessary to build an understanding of the strengths and limitations of MPS models and closing the current gaps. Here, we review some of the advances in MPS research, focusing on liver, intestine, vascular system, kidney and lung and present examples highlighting the context of use for these systems. For MPS to gain a foothold in drug development, they must have added value over existing approaches. Ideally, the application of MPS will augment in vivo studies and reduce the use of animals via tiered screening with less reliance on exploratory toxicology studies to screen compounds. Because MPS support multiple cell types (e.g. primary or stem-cell derived cells) and organ systems, identifying when MPS are more appropriate than simple 2D in vitro models for understanding physiological responses to test articles is necessary. Once identified, MPS models require qualification for that specific context of use and must be reproducible to allow future validation. Ultimately, the challenges of balancing complexity with reproducibility will inform the promise of advancing the MPS field and are critical for realization of the goal to reduce, refine and replace (3Rs) the use of animals in nonclinical research.

CD40 is a member of the TNF family of receptors that has been shown to play a crucial role in enhancing dendritic cell activity and fostering anti-tumor immune responses. In this study, we demonstrate the in vitro properties and in vivo efficacious activity of the CD40 agonist antibody, CP-870,893. CP-870,893 is a fully human, IgG2 antibody that selectively interacts with CD40 at a site distinct from its ligand-binding region with a KD of 0.4 nM. It enhances the expression of MHC class II, CD54, CD86, and CD23 on human B cells in vitro. CP-870,893 also enhances dendritic cell activity as evidenced by cytokine secretion (IL-12, IL-23, IL-8), the upregulation of CD86 and CD83, and the ability to prime T cells to secrete IFNγ. In SCID-beige mice, a single parenteral injection of CP-870,893 was therapeutically effective against several CD40(pos) human tumors (B-cell lymphoma, breast, colon, and prostate) indicating direct effects on tumor cell survival and/or growth. When mice were co-implanted with human T cells and dendritic cells, the activity of CP-870,893 against CD40(pos) tumors increased, and efficacy was also observed against CD40(neg) and CD40(low) tumors demonstrating the ability of CP-870,893 to enhance anti-tumor immune function in vivo. These studies suggest that CP-870,893 has the potential to be efficacious against a wide range of tumor types through both direct and immune-mediated effects.

709 Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) is a cell surface receptor expressed on activated T cells. The natural B7 ligands for CTLA4 are expressed on antigen-presenting cells. Experimental evidence indicates that binding of B7 to CTLA4 delivers a negative regulatory signal to T cells, and that blocking this negative signal results in markedly enhanced T cell immune function and antitumor activity in animal models. A fully human potent anti-huCTLA4 antagonist IgG2 antibody, CP-675,206, was generated in XenoMouse® mice at Abgenix, Inc. CP-675,206 was tested for its ability to enhance IL-2 production in normal and cancer patient whole blood (WB) and peripheral blood mononuclear cells (PBMC) stimulated with staphylococcal enterotoxin A (SEA) superantigen. WB and PBMC cultures were stimulated with SEA and anti-CTLA4 mAb, or an isotype-matched control mAb, for 72 hours at 37°C and assayed for secreted IL-2 by ELISA. Blood samples were obtained from normal donors and patients with cancers at different stages. Cancer types included prostate, renal, colon, rectal, ovarian, melanoma, Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. The percentage of positive responses, average magnitude of IL-2 enhancement, and average IL-2 fold increase were generally similar for normal and cancer patient WB or PBMC cultures treated with CP-675,206 mAb (30 ug/ml). Remarkably, CP-675,206 concentration response profiles (0.1 to 100 ug/ml) from normal and cancer patient samples were comparable regardless of cancer type or disease stage. Additional studies showed that soluble CTLA4 levels determined by ELISA were undetectable (

3801 Urokinase plasminogen activator (uPA) and its receptor (uPAR) are overexpressed in many cancer types compared to normal tissue. The presence of both uPA and uPAR in cancer tissue may potentially be exploited in cancer therapy for specific and targeted activation of prodrugs. We have constructed a modified form of anthrax protective antigen, PrAg-U2, in which a furin activation site is shifted with an uPA cleavage site. PrAg-U2 administered together with the fusion protein FP59, consisting of lethal factor residues 1–254 and the ADP ribosylation domain of Pseudomonas exotoxin A, constitutes a potent and uPA-activity dependent cytotoxic drug (OTP-001). In vitro binding of pro-uPA to uPAR is necessary for the cytotoxicity of OTP-001 (Liu et al., J. Biol. Chem, 276:17976–84, 2001) and local administration of OTP-001 in mice with transplanted tumors had a potent antitumor effect (Liu et al., PNAS, 100:657–62, 2003). The aim of the present studies was i) To examine the antitumor effect of OTP-001 after systemic administration, ii) To find the optimal ratio between the two components PrAg-U2 and FP59, iii) To define the “therapeutic window” of OTP-001. Five separate in vivo experiments were performed with three different transplanted tumors, Lewis lung carcinoma, T241 fibrosarcoma and B16 melanoma. In all studies, C57BI/6J mice where transplanted with 10 6 tumor cells. When the tumors had reached a volume of approximately 50 mm 3 , a dose range of OTP-001 was administered systemically to the mice at day 0, 3, and 6. Different ratios of PrAg-U2 and FP59 were tested. Tumor sizes were obtained by daily recording of two orthogonal diameters during the growth phase. All experiments unequivocally demonstrated that OTP-001 has significant antitumor effect after systemic administration in mice with transplanted B16, T241 or Lewis lung tumors. These studies showed that OTP-001 displays a clear dose-response relationship with regard to anti-tumor effect and systemic toxicity. The dose-limiting toxicity appears to be due to mucosal reactions in the gut. The anti-tumor effect was most pronounced with a ratio of the two components PrAg-U2 and FP59 of 25:1. Intraperitoneal administration of 30 μg PrAg-U2 and 1.2 μg FP59 day 0, day 3 and day 6 was found to have minimal toxic effects and still had a significant antitumor effect.