Long-term reversal of established autoimmunity upon transient blockade of the LFA-1/intercellular adhesion molecule-1 pathway

Transgenic models and administration of mAbs directed against the LFA-1/intercellular adhesion molecule 1 (ICAM-1) pathway have shown that these costimulatory molecules play a key role in generating effector cells mediating inflammatory responses. In this report, durable remission of recent diabetes in nonobese diabetic (NOD) mice was induced by transient expression of an immunoadhesin gene encoding the soluble form of ICAM-1 (sICAM-1/Ig). A single i.v. injection of an adenovirus vector encoding the immunoadhesin gene led to 70% diabetes remission as opposed to 0% in mice injected with a control adenovirus vector. Despite the rapid decline of sICAM-1/Ig serum levels, diabetes remission remained stable in 50% of NOD mice for >6 mo. sICAM-1/Ig expression also led to long-term protection against diabetes in prediabetic NOD mice. sICAM-1/Ig in vitro induced an agonistic effect of T cell activation in a TCR-transgenic model, increasing T cell proliferation and IL-2 secretion. Importantly, protected mice were not immunosuppressed because they rejected skin allografts normally and developed immunity against the adenovirus vector. Rather, sICAM-1/Ig induced active tolerance, as assessed by the persistence of diabetogenic T cells in protected mice and the reversal of protection by immunosuppression with cyclophosphamide.

DQ 65-79, a peptide derived from HLA class II, induces I kappa B expression

A synthetic peptide corresponding to residues 65-79 of the alpha helix of the alpha-chain of the class II HLA molecule DQA03011 (DQ 65-79) inhibits the proliferation of human T lymphocytes in an allele nonrestricted manner. By using microarray technology, we found that expression of 29 genes was increased or decreased in a human CTL cell line after treatment with DQ 65-79. This study focuses on one of these genes, IkappaB-alpha, whose expression is increased by DQ 65-79. IkappaB proteins, including IkappaB-alpha and IkappaB-beta, are increased in T cells treated with DQ 65-79. Nuclear translocation of the NF-kappaB subunits p65 and p50 is decreased in T cells after treatment with DQ 65-79, while elevated levels of p65 and p50 are present in cytosol. DQ 65-79 inhibits the degradation of IkappaB-alpha mRNA and inhibits the activity of IkappaB kinase. These findings indicate that the DQ 65-79 peptide increases the level of IkappaB proteins, thereby preventing nuclear translocation of the transcription factor, NF-kappaB, and inhibiting T cell proliferation.

Design and synthesis of type-III mimetics of ShK toxin

ShK toxin is a structurally defined, 35-residue polypeptide which blocks the voltage-gated Kv1.3 potassium channel in T-lymphocytes and has been identified as a possible immunosuppressant. Our interest lies in the rational design and synthesis of type-III mimetics of protein and polypeptide structure and function. ShK toxin is a challenging target for mimetic design as its binding epitope consists of relatively weakly binding residues, some of which are discontinuous. We discuss here our investigations into the design and synthesis of 1st generation, small molecule mimetics of ShK toxin and highlight any principles relevant to the generic design of type-III mimetics of continuous and discontinuous binding epitopes. We complement our approach with attempted pharmacophore-based database mining.

Olefin self-metathesis as a new entry into xenotransplantation antagonists bearing the Galili antigen

A hexameric disaccharide cluster bearing the terminal Gal alpha related xenotransplantation antigen was constructed using a sequence of ruthenium carbenoid catalyzed olefin self-metathesis of monoallylated tribenzyl pentaerythritol followed, after interconversion of benzyl ethers into para-iodobenzyl ethers, by a single step Sonogashira cross-coupling of six prop-2-ynyl glycosides onto a hexameric aryl iodide scaffold.

Total synthesis of the cyclic heptapeptide Argyrin B: a new potent inhibitor of T-cell independent antibody formation

[structure: see text] The total synthesis of Argyrin B (1) is presented using a synthetic plan that is convergent and flexible and conserves the stereogenic centers. The unusual amino acid 4-methoxy tryptophan (6) was obtained via an enzymatic resolution. Cyclization followed by oxidative elimination of the phenylseleno cysteine to the sensitive dehydroalanine afforded synthetic 1.

Natural products as probes of cell biology: 20 years of didemnin research

The discovery of the didemnin family of marine depsipeptides launched an exciting and intriguing chapter in natural product chemistry. The unusual structure of the didemnin congeners has led to several total syntheses by research groups from around the world. The impressive in vitro and in vivo biological activities of the didemnins resulted in the first human clinical trials in the U.S. of a marine natural product against cancer, and additional clinical trials of a second-generation didemnin, dehydrodidemnin B (aplidine), are underway. As we mark the 20-year anniversary of the discovery of the didemnins, this class of natural products continues to stimulate active research in fields ranging from synthetic and medicinal chemistry to clinical oncology and cell biology. While some progress was made in dissecting the molecular mechanism of action and in establishing structure-activity relationships, there are still more questions than answers. This review covers the recent didemnin literature, highlighting the work directed towards understanding how this group of natural products interact with fundamental processes such as cell proliferation, protein biosynthesis, and apoptosis. The didemnin field illustrates how natural product chemistry may be used as a critical tool for the study of cell biology.

Generation of an LFA-1 antagonist by the transfer of the ICAM-1 immunoregulatory epitope to a small molecule

The protein-protein interaction between leukocyte functional antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) is critical to lymphocyte and immune system function. Here, we report on the transfer of the contiguous, nonlinear epitope of ICAM-1, responsible for its association with LFA-1, to a small-molecule framework. These LFA-1 antagonists bound LFA-1, blocked binding of ICAM-1, and inhibited a mixed lymphocyte reaction (MLR) with potency significantly greater than that of cyclosporine A. Furthermore, in comparison to an antibody to LFA-1, they exhibited significant anti-inflammatory effects in vivo. These results demonstrate the utility of small-molecule mimics of nonlinear protein epitopes and the protein epitopes themselves as leads in the identification of novel pharmaceutical agents.

Chemical modification of chitosan: preparation and lectin binding properties of alpha-galactosyl-chitosan conjugates. Potential inhibitors in acute rejection following xenotransplantation

Water-soluble alpha-galactosyl-chitosan conjugates were prepared by reductive amination of p-formylphenyl beta-melibioside on chitosan in good yield. Strong binding with phytohemagglutinin was demonstrated using Griffonia simplicifolia.

Combinatorial biosynthesis in microorganisms as a route to new antimicrobial, antitumor and neuroregenerative drugs

Combinatorial biosynthesis utilizes the genes of biosynthetic pathways that produce microbial products to create novel chemical structures. The engineering of mondular polyketide synthase (PKS) genes has been the major focus of this effort and has led to the production of analogs of macrolide antibiotics like the erythromycins and their derived ketolides, and of the immunosuppressive macrolide FK-520 (Fujisawa Pharmaceutical Co Ltd). Approaches to making analogs of the promising antitumor compounds known as epothilones are also being explored. Lead compounds for further study have resulted and routes to analogs of other pharmacologically important compounds have been established. To facilitate this work, many new tools for manipulating and studying the multifunctional PKSs have been developed including the development of Escherichia coli as a PKS expression last. These developments have resulted in faster ways of engineering PKS to produce new compounds for the development of chemotherapeutic agents from natural products.

Synthetic study on novel immunosuppressant KF20444

The two new synthetic routes to 6,7-dihydro-10-fluoro-3-(2-fluorophenyl)-5H- benzo[6,7]cyclohepta[1,2-b]-quinoline-8-carboxylic acid (1), a novel immunosuppressant KF20444, are described. The seven-membered ring construction from 2-[4-(2-fluorophenyl)phenyl]-3-(2-carboxyethyl)-4-chloromethyl-6-fluoroquinoline (17c) was achieved by intramolecular Friedel-Crafts reaction under acidic conditions as the key step. Subsequently, the oxidation of 4-chloromethyl group followed by reduction of carbonyl group on the seven-membered ring afforded 1. This route provides a new method for the synthesis of 1.

Cladribine. Ortho Biotech Inc

Cladribine, an adenosine deaminase inhibitor, has been developed and launched by Ortho Biotech in collaboration with The Scripps Research Institute for the treatment of several neoplasms, including acute myelogenous leukemia, chronic lymphocytic leukemia, chronic myelogenous leukemia, cutaneos T-cell lymphoma, hairy-cell leukemia and non-Hodgkin's lymphoma. It was first launched in the US in February 1993. Ortho Biotech and The Scripps Research Institute have since been developing the compound for its potential use in multiple sclerosis (MS). In 1997, Ortho filed air NDA in the US for the use of cladribine in the treatment of relapsing-remitting and secondary progressive MS. An FDA drug advisory committee was planning to meet in January 1999 to discuss the NDA. However, Ortho cancelled the meeting. Following an FDA inspection during December 1998 and January 1999, the Scripps Clinic received a warning letter from the FDA in April 1999 regarding violations in the clinical studies of cladribine for MS, and Ortho withdrew the NDA after concluding that further clinical studies would be necessary. Cladribine has been known since the 1960s as an intermediate for the synthesis of 2-deoxynucleotides and its potential for the treatment of leukemia was disclosed in 1984. The Scripps Research Institute and the Johnson & Johnson group hold several patents claiming preparation methods (US 05208327), and additional indications, such as multiple sclerosis (WO-09316706) and rheumatoid arthritis (US-05310732). The associated patent, WO-09323508, is the only one among those patents that claims the use of unmodified cladribine for the treatment of leukemia, but it focuses particularly on a specific form of the disease, chronic myelogenous leukemia. Analysts at UBS Warburg predicted in October 2001, that the product would make US sales of $50 million in 2004 for its MS indication.

Stereoselective total synthesis of (+)-myriocin from D-mannose

The stereoselective total synthesis of myriocin 1 from D-mannose is described; the carbon framework with three contiguous chiral centers including a tetra-substituted carbon with nitrogen was effectively constructed using Overman rearrangement as the key reaction.

A practical synthesis of (+)-discodermolide and analogues: fragment union by complex aldol reactions

A practical stereocontrolled synthesis of (+)-discodermolide (1) has been completed in 10.3% overall yield (23 steps longest linear sequence). The absolute stereochemistry of the C(1)-C(6) (7), C(9)-C(16) (8), and C(17)-C(24) (9) subunits was established via substrate-controlled, boron-mediated, aldol reactions of the chiral ethyl ketones 10, 11, and 12. Key fragment coupling reactions were a lithium-mediated, anti-selective, aldol reaction of aryl ester 8 (under Felkin-Anh induction from the aldehyde component 9), followed by in situ reduction to produce the 1,3-diol 40, and a (+)-diisopinocampheylboron chloride-mediated aldol reaction of methyl ketone 7 (overturning the inherent substrate induction from the aldehyde component 52) to give the (7S)-adduct 58. The flexibility of our overall strategy is illustrated by the synthesis of a number of diastereomers and structural analogues of discodermolide, which should serve as valuable probes for structure-activity studies.

A novel three-component butenolide synthesis

[reaction: see text]. 5-Acylamino butenolides can be assembled by a multicomponent reaction (MCR) of isocyanides, glyoxals, and acetophosphonic acid diethylesters, followed by a intramolecular Wittig-type reaction. The reaction can be performed either in one pot or with the isolation of the intermediate Passerini product. This versatile reaction offers three independent inputs displayed in the final product. Applications in combinatorial chemistry and natural product synthesis can be envisioned.

Everolimus. Novartis

Everolimus (RAD-001, SDZ RAD, Certican), an analog of sirolimus, is an oral immunosuppressant that inhibits growth factor-induced cell proliferation, under development by Novartis as a potential treatment for transplant rejection. Phase III trials were initiated by the end of 1998 [319337] and were ongoing in February 2001 [400448]. At the end of 2000, Novartis was hoping to file for approval of the compound in 2001 [392881], with a possible launch in mild-2002 [392881], [401979]. Completion of phase III trials in heart transplant patients is expected this year and lung and liver transplants by 2003. In 1999, American Home Products (AHP) initiated an action for infringement of the patent EP-00401747, which covers the use of sirolimus in transplantation in the UK, the Netherlands and Germany, seeking to restrain the clinical trial program for everolimus. Novartis subsequently filed a counterclaim for invalidity. In December 1999, the UK High Court of Justice ruled that everolimus infringes the British counterpart of EP-00401747 [349637]. In contrast, in April 2000, the District Court of The Hague ruled that everolimus does not infringe patent rights licensed to AHP [362823] and in July 2000, The Court of Appeal in the UK came to the same conclusion [376559]. In February 2001, the Opposition Board at the European Patent Office upheld Novartis' European patent for everolimus, which the Board held to be 'inventive' [400448]. In July 2000, Vontobel estimated sales of SFr 80 million in 2002, rising to SFr 800 million in 2004 [378871]. In February 2001, Merrill Lynch predicted sales of SFr 125 million rising to SFr 661 million in 2005 [411704].

A retroviral-derived immunosuppressive peptide activates mitogen-activated protein kinases

The highly conserved region within the retroviral transmembrane envelope proteins has been implicated in a number of retrovirus-associated mechanisms of immunosuppression. CKS-17, a synthetic peptide representing the prototypic sequence of the immunosuppressive domain, has been found to suppress numerous immune functions, disregulate cytokines, and elevate intracellular cAMP. In this report we show that using a human monocytic cell line THP-1, CKS-17 activates mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase 1 and 2 (ERK1/2). Kinetic studies show that CKS-17 induces an acute increase of ERK1/2 activity followed by a rapid decrease and then a second sustained increase of ERK1/2. CKS-17 also activates MAP kinase/ERK kinase (MEK) with a similar induction pattern. Mutant THP-1 cells isolated in our laboratory, in which CKS-17 exclusively fails to activate cAMP, did not show the transient decrease of CKS-17-induced ERK1/2 phosphorylation. Pretreatment of THP-1 cells or mutant THP-1 cells with cAMP analog or forskolin followed by treatment with CKS-17 showed no activation of MEK or ERK1/2. These results indicate that CKS-17 activates the MEK/ERK cascade and that there is a cross-talk between CKS-17-mediated MEK/ERK cascade and cAMP in that the MEK/ERK cascade is negatively regulated by cAMP. These data present a novel molecular mechanism(s) by this highly conserved retroviral immunosuppressive component.

Total synthesis of tricyclic azaspirane derivatives of tyrosine: FR901483 and TAN1251C

A solution to the long-standing problem presented by the oxidative cyclization of a phenolic 3-arylpropionamide to a spirolactam has been developed in this laboratory via oxazoline chemistry. This research was motivated by our interest in some novel tricyclic azaspirane natural products formally derived from tyrosine, such as FR901483 and TAN1251C. In this paper, we disclose full details of the total synthesis of these substances.

N-methoxy-N-acylnitrenium ions: application to the formal synthesis of (+/-)-desmethylamino FR901483

[reaction: see text] The formal synthesis of (+/-)-desmethylamino FR901483 (2) is described. Construction of the unique azatricyclic skeleton of 2 was accomplished by a sequence which involved (i) preparation of dienone 7 by an N-methoxy-N-acylnitrenium ion-induced spirocyclization, (ii) formation of 2-azabicyclo[3.3.1]nonane 5 by the 6-(pi-exo)-exo-trig radical cyclization of 1,7-enyne 6, and (iii) installation of the C-5 p-methoxybenzyl side chain by Lewis acid-mediated alkylation of silyl enol ether 18.

Toward the total synthesis of variecolin

[reaction: see text] An annulative approach toward the total synthesis of the sesterterpenoid variecolin (1) is presented. Synthesis of the key hemiketal, containing the core ABC ring skeleton, has been achieved on a model system by an expeditious route utilizing samarium(II) iodide. Furthermore, enantioselective syntheses of component fragments for the total synthesis have been developed.

Synthesis of lipid A type pyran carboxylic acids with ether chains and their biological activities

Synthesis of lipid A type pyran carboxylic acids having ether chains at both the C-3' and C-4 positions and their bioactivities toward human U937 cells are described.

Total synthesis of the immunosuppressant FR901483 via an amidoacrolein cycloaddition

[reaction: see text]. The total synthesis of the potent immunosuppressant FR901483 is described. In a key step, the intermolecular Diels-Alder cycloaddition of an amidoacrolein with 2-(triisopropylsilyloxy)-1,3-butadiene produced the desired 3-cyclohexene-1-carboxaldehyde. This compound was subjected to basic followed by acidic conditions which effected two sequential aldol cyclizations to deliver the tricyclic ring system of the natural product, suitably functionalized for completion of the total synthesis.

A retro-inverso peptide mimic of CD28 encompassing the MYPPPY motif adopts a polyproline type II helix and inhibits encephalitogenic T cells in vitro

Complete activation of T cells requires two signals: an Ag-specific signal delivered via the TCR by the peptide-MHC complex and a second costimulatory signal largely provided by B7:CD28/CTLA-4 interactions. Previous studies have shown that B7 blockade can either ameliorate experimental autoimmune encephalomyelitis by interfering with CD28 signaling or exacerbate the disease by concomitant blockade of CTLA-4 interaction. Therefore, we developed a functional CD28 mimic to selectively block B7:CD28 interactions. The design, synthesis, and structural and functional properties of the CD28 free peptide, the end group-blocked CD28 peptide, and its retro-inverso isomer are shown. The synthetic T cell-costimulatory receptor peptides fold into a polyproline type II helical structure commonly seen in regions of globular proteins involved in transient protein-protein interactions. The binding determinants of CD28 can be transferred onto a short peptide mimic of its ligand-binding region. The CD28 peptide mimics effectively block the expansion of encephalitogenic T cells in vitro suggesting the potential usefulness of the peptides for the treatment of autoimmune disease conditions requiring down-regulation of T cell responses.

Samarium(II)-mediated 4-exo-trig cyclization. A stereocontrolled approach to the core of pestalotiopsin A

[reaction: see text] Pestalotiopsin A is a structurally unique caryophyllene-type sesquiterpene which has shown immunosuppressive activity and cytotoxicity in preliminary assays. A stereocontrolled approach to the functionalized 2-oxabicyclo[3.2.0]heptane core of pestalotiopsin A is described. The approach includes a samarium(II)-mediated 4-exo-trig cyclization and a trans-lactonization process triggered by the addition of alkylytterbium reagents to a cyclobutanone intermediate.

Aromatic quinolinecarboxamides as selective, orally active antibody production inhibitors for prevention of acute xenograft rejection

The prevention of xenograft rejection is substantially dependent on inhibiting antibodies (Ab) produced by B-cells independently of T-cell signals (TI-1). Due to their ubiquitous biochemical mechanisms of action, the immunosuppressants currently employed not only fail to discriminate between B- and T-cells but also have a narrow therapeutic window and, thus, their prolonged use in complex immunosuppressive regimens is problematic. By capitalizing on the target enzyme-bound (DHODH) structure 1b of one of these compounds, leflunomide, and modulating part of its multiple mechanisms of action to gain selectivity, the quinoline-8-carboxamide 3 was designed as a potentially weak enzyme inhibitor but effective immunosuppressant. Compound 3 fulfilled the mechanistic criteria set and had 10-fold B-cell over T-cell selectivity. Its pyridyl analogue 4 was found to be a highly potent and selective B-cell immunosuppressant with a 75-fold selectivity for B- over T-cells (as judged by the MLR data) and no general cytotoxicity at concentrations up to 160-fold higher than those required to inhibit B-cells. In the mouse, 4 effectively blocked TI-1 Ab production and suppressed Ab-mediated xenograft rejection in a xenotransplantation model under a once-daily dosing regimen, with efficacy down to 0.3 mg/kg/day po. These are the first data demonstrating the feasibility of the development of drugs specific for impeding Ab production.

Synthesis of novel anti-inflammatory peptides derived from the amino-acid sequence of the bioactive protein SV-IV

SV-IV is a basic, thermostable, secretory protein of low Mr (9758) that is synthesized by rat seminal vesicle (SV) epithelium under strict androgen transcriptional control. This protein is of obvious pharmacological interest because it has potent nonspecies-specific immunomodulatory, anti-inflammatory, and pro-coagulant activities. In evaluating the clinical relevance and the possible use in medicine of SV-IV, we became interested in the study of its structure-function relationships and aimed to identify in its polypeptide chain specific peptide fragments possessing the marked anti-inflammatory properties of the protein not associated with other biological activities (pro-coagulation and immunomodulation) typical of this molecule. By using two different experimental approaches (the fragmentation of the protein into peptide derivatives by chemical methods and the organic synthesis on solid phase of selected peptide fragments), data were obtained showing that in this protein: (a) the immunomodulatory activity is related to the structural integrity of the whole molecule; (b) the anti-inflammatory activity is located in the N-terminal region of the molecule, the 8-16 peptide fragment being the most active; (c) the identified anti-inflammatory peptide derivatives do not seem to possess pro-coagulant activity, even though this particular function has been located in the 1-70 segment of the molecule.