Elena Ho

Differential Inhibition of Inducible T Cell Cytokine Secretion by Potent Iron Chelators

Effector functions and proliferation of T helper (Th) cells are influenced by cytokines in the environment. Th1 cells respond to a synergistic effect of interleukin-12 (IL-12) and interleukin-18 (IL-18) to secrete interferon-gamma (IFN-γ). In contrast, Th2 cells respond to interleukin-4 (IL-4) to secrete IL-4, interleukin-13 (IL-13), interleukin-5 (IL-5), and interleukin-10 (IL-10). The authors were interested in identifying nonpeptide inhibitors of the Th1 response selective for the IL-12/IL-18-mediated secretion of IFN-γ while leaving the IL-4-mediated Th2 cytokine secretion relatively intact. The authors established a screening protocol using human peripheral blood mononuclear cells (PBMCs) and identified the hydrazino anthranilate compound 1 as a potent inhibitor of IL-12/IL-18-mediated IFN-γ secretion from CD3+ cells with an IC50 around 200 nM. The inhibitor was specific because it had virtually no effect on IL-4-mediated IL-13 release from the same population of cells. Further work established that compound 1 was a potent intracellular iron chelator that inhibited both IL-12/IL-18- and IL-4-mediated T cell proliferation. Iron chelation affects multiple cellular pathways in T cells. Thus, the IL-12/IL-18-mediated proliferation and IFN-γ secretion are very sensitive to intracellular iron concentration. However, the IL-4-mediated IL-13 secretion does not correlate with proliferation and is partially resistant to potent iron chelation

Identification of orally bioavailable, non-amidine inhibitors of Urokinase Plasminogen Activator (uPA)

In this Letter we report the synthesis and evaluation of a series of non-amidine inhibitors of Urokinase Plasminogen Activator (uPA). Starting from compound 1, a significant change provided compounds in which the amidine, binding in the S1 pocket, was replaced with a primary amine. Further modifications led to the identification of potent, selective, and orally bioavailable uPA inhibitors.

Anti-tumor efficacy of the nucleoside analog 1-(2-deoxy-2-fluoro-4-thio-β-D-arabinofuranosyl) cytosine (4′-thio-FAC) in human pancreatic and ovarian tumor xenograft models

1‐(2‐Deoxy‐2‐fluoro‐4‐thio‐β‐D‐arabinofuranosyl) cytosine (4′‐thio‐FAC) is a deoxycytidine analog that has been shown previously to have impressive anti‐proliferative and cytotoxic effects in vitro and in vivo toward colorectal and gastric tumors. In our present studies, the pharmacokinetic behavior in nude mice and the effectiveness of 4′‐thio‐FAC against human pancreatic and ovarian tumor growth were assessed in comparison with standard chemotherapeutic agents. Potent in vitro anti‐proliferative effects were observed against pancreatic (Capan‐1, MIA‐PaCa‐2, BxPC‐3) and ovarian (SK‐OV‐3, OVCAR‐3, ES‐2) cancer cell lines with IC50 of 0.01–0.2 μM. In vivo anti‐tumor activity was evaluated in nude mice bearing subcutaneously (s.c.) implanted human pancreatic tumor xenografts or intraperitoneally (i.p.) disseminated human ovarian xenografted tumors. Oral daily administration of 4′‐thio‐FAC for 8–10 days significantly inhibited the growth of gemcitabine‐resistant BxPC‐3 pancreatic tumors and induced regression of gemcitabine‐refractory Capan‐1 tumors. 4′‐Thio‐FAC was also a highly effective inhibitor of ovarian peritoneal carcinomatosis. In the SK‐OV‐3 and ES‐2 ovarian cancer models, 4′‐thio‐FAC prolonged survival to a greater extent than that observed with gemcitabine. Furthermore, the superiority of 4′‐thio‐FAC to carboplatin and paclitaxel was demonstrated in the ES‐2 clear cell ovarian carcinoma model. Studies provide evidence that 4′‐thio‐FAC is a promising new alternative to gemcitabine and other chemotherapeutic drugs in the treatment of a variety of tumor indications, including pancreatic and ovarian carcinoma.

Design, synthesis, and biological activity of novel factor Xa inhibitors: 4-aryloxy substituents of 2,6-diphenoxypyridines.

A novel series of triaryloxypyridines have been designed to inhibit factor Xa, a serine protease strategically located in the coagulation cascade. Inhibitor 5e has a K(I) against factor Xa of 0.12nM and is greater than 8000- and 2000-fold selective over two related serine proteases, thrombin and trypsin, respectively. The 4-position of the central pyridine has been identified as a site that tolerates various substitutions without deleterious effects on potency and selectivity. This suggests that the 4-position of the pyridine ring is an ideal site for chemical modifications to identify inhibitors with improved pharmacokinetic characteristics. This investigation has resulted in inhibitor 5d, which has an oral availability of 6% in dogs. The synthesis, in vitro activity, and in vivo profile of this class of inhibitors is outlined.

Discovery of selective urokinase plasminogen activator (uPA) inhibitors as a potential treatment for multiple sclerosis

We report here the design and synthesis of a novel series of benzylamines that are potent and selective inhibitors of uPA with promising oral availability in rat. Further evaluation of one representative (ZK824859) of the new structural class showed that this compound lowered clinical scores when dosed in either acute or chronic mouse EAE models, suggesting that uPA inhibitors of this type could be useful for the treatment of multiple sclerosis.