Catherine A. Fleener

Assessment of belatacept-mediated costimulation blockade through evaluation of CD80/86-receptor saturation.

Background. The selective inhibitor of T-cell costimulation, belatacept, blocks CD28-mediated T-cell activation by binding CD80 and CD86 on antigen-presenting cells. Understanding the extent to which belatacept binds to its targets in patients may enable correlation of belatacept exposure to receptor saturation as a pharmacodynamic measure of costimulation blockade. Methods. Flow cytometry-based receptor competition assays were developed to monitor concentration-dependent occupancy of CD80 and CD86 receptors in whole blood and dendritic cell cultures in vitro. Receptor occupancy was correlated with inhibition of mixed leukocyte reactions and clinical validation was obtained by comparing receptor saturation in whole blood from healthy volunteers and in de novo renal transplant recipients participating in studies comparing cyclosporine and belatacept-based immunosuppression. Results. Belatacept saturated CD80 and CD86 receptors in whole blood and dendritic cell cultures, although the belatacept concentrations required for CD86-receptor saturation were approximately 10-fold higher than those required for CD80 saturation (IC50=0.102 &mgr;g/mL vs. 0.009 &mgr;g/mL). Primary alloresponses were inhibited at the belatacept concentration required for CD86-receptor saturation, but not at the lower concentration needed to saturate CD80. Whole blood from belatacept-treated patients had significantly lower levels of free CD86 receptors versus pretransplant levels, healthy volunteers, or cyclosporine-treated patients. CD86-receptor saturation correlated with belatacept dose/dose frequency and remained consistently more than 80%. Conclusions. These results suggest that belatacept-mediated inhibition of alloresponses involved in transplant rejection correlates with CD86 saturation, indicating that CD86-receptor occupancy may be a valid pharmacodynamic measure of costimulation blockade and provide the first direct clinical evidence that belatacept binds to one of its targets.

Rapid synthesis of triazine inhibitors of inosine monophosphate dehydrogenase

A series of novel triazine-based small molecule inhibitors (IV) of inosine monophosphate dehydrogenase was prepared. The synthesis and the structure-activity relationships (SAR) derived from in vitro studies are described.

Identification of novel and potent isoquinoline aminooxazole-Based IMPDH inhibitors

Screening of our in-house compound collection led to the discovery of 5-bromo-6-amino-2-isoquinoline 1 as a weak inhibitor of IMPDH. Subsequent optimization of 1 afforded a series of novel 2-isoquinolinoaminooxazole-based inhibitors, represented by 17, with single-digit nanomolar potency against the enzyme.

A Monovalent Anti-Human CD28 Domain Antibody Antagonist: Preclinical Efficacy and Safety

Targeting the CD28-CD80/86 pathway with an anti-CD28 antagonist is a promising alternative to current therapies for autoimmunity. However, attempts at generating conventional anti-CD28 mAbs lacking stimulatory activity has been challenging. In this study, we describe anti-human CD28 receptor antagonist domain Abs (dAbs) that are specific for human CD28. These dAbs are potent inhibitors of T cell activation, with an EC50 of 35 ± 14 ng/ml for inhibition of proliferation. The EC50 of 53 ± 11 ng/ml in an ex vivo CD28 receptor occupancy assay corresponds with in vitro functional activity, suggesting a direct correlation. The anti-CD28 dAb is equipotent in the inhibition of CD80- and CD86-mediated T cell proliferation and does not interfere with CTLA-4–mediated downmodulation of CD86 expression on APCs. The anti-CD28 dAbs are monomeric and do not demonstrate any evidence of agonism or costimulatory activity. In cynomolgus monkeys, the anti-CD28 dAb demonstrated pharmacodynamic activity, as measured by the inhibition of a T cell–dependent Ab response, without evidence of T cell depletion or cytokine release. Furthermore, there was a strong correlation between systemic exposure, duration, and extent of CD28 receptor occupancy, and pharmacodynamic activity. Taken together, these data support clinical evaluation of this novel anti-CD28 dAb for the treatment of autoimmune diseases.

Inhibitors of inosine monophosphate dehydrogenase: SARs about the N-[3-Methoxy-4-(5-oxazolyl)phenyl moiety

The first reported structure-activity relationships (SARs) about the N-[3-methoxy-4-(5-oxazolyl)phenyl moiety for a series of recently disclosed inosine monophosphate dehydrogenase (IMPDH) inhibitors are described. The syntheses and in vitro inhibitory values for IMPDH II, and T-cell proliferation (for select analogues) are given.

3-Cyanoindole-based inhibitors of inosine monophosphate dehydrogenase: synthesis and initial structure–Activity relationships

A series of novel small molecule inhibitors of inosine monophosphate dehydrogenase (IMPDH), based upon a 3-cyanoindole core, were explored. IMPDH catalyzes the rate determining step in guanine nucleotide biosynthesis and is a target for anticancer, immunosuppressive and antiviral therapy. The synthesis and the structure-activity relationships (SAR), derived from in vitro studies, for this new series of inhibitors is given.

A survey of cyclic replacements for the central diamide moiety of inhibitors of inosine monophosphate dehydrogenase.

A series of heterocyclic replacements for the central diamide moiety of 1, a potent small molecule inhibitor of inosine monophosphate dehydrogenase (IMPDH) were explored The synthesis and the structure-activity relationships (SARs), derived from in vitro studies, for these new series of inhibitors is given.

Novel diamide-based inhibitors of IMPDH

A series of novel amide-based small molecule inhibitors of inosine monophosphate dehydrogenase is described. The synthesis and the structure-activity relationships (SARs) derived from in vitro studies are presented.

Novel guanidine-based inhibitors of inosine monophosphate dehydrogenase.

A series of novel guanidine-based small molecule inhibitors of inosine monophosphate dehydrogenase (IMPDH) was explored. IMPDH catalyzes the rate determining step in guanine nucleotide biosynthesis and is a target for anticancer, immunosuppressive and antiviral therapy. The synthesis and the structure-activity relationships (SARs), derived from in vitro studies, for this new series of inhibitors is given.

The TosMIC approach to 3-(Oxazol-5-yl) indoles: application to the synthesis of indole-based IMPDH inhibitors

A modified approach to the synthesis of 3-(oxazolyl-5-yl) indoles is reported. This method was applied to the synthesis of series of novel indole based inhibitors of inosine monophosphate dehydrogenase (IMPDH). The synthesis and the structure-activity relationships (SARs), derived from in vitro studies, for this new series of inhibitors is given.