The tyrosine kinase inhibitor imatinib (imatinib, STI571, Glivec, and Gleevec) is increasingly used in patients undergoing allogeneic transplantation for leukemia. However, little is known regarding its potential immunoregulatory effects. Here, we investigate the effect of imatinib on T-cell receptor ( IntroductionImatinib mesylate (imatinib, STI571, Glivec, and Gleevec; Novartis, Basel, Switzerland) is a potent selective inhibitor of the tyrosine kinases (TKs) ABL, ARG, PDGFR ␣ and ␤, and c-KIT. It has proven clinical efficacy in the treatment of malignancies characterized by constitutive activation of these TKs: chronic myeloid leukemia (CML), Philadelphia chromosome-positive (Ph ϩ ) acute lymphocytic leukemia (ALL), myleoproliferative disorders due to chromosomal rearrangements in the PDGF-R locus and gastrointestinal stromal tumors (GIST) with mutations in c-KIT. [1][2][3][4][5] Imatinib can induce reversible dose-dependent hematologic side effects, predominantly neutropenia and thrombocytopenia. 3,6 In CML, this may in part be attributed to compromised normal hematopoiesis in addition to suppression of the BCR-ABLpositive clone that can dominate myelopoiesis. An additional mechanism may be inhibition of c-KIT in normal hematopoietic progenitor cells, which could account for the mild imatinib-induced myelosuppression observed in some patients with GIST. 2 However, these mechanisms are unlikely to account fully for the observed lymphopenia and hypogammaglobulinemia in patients with CML on long-term imatinib therapy. In one study, 25% of patients with CML on 400 mg imatinib daily developed mild lymphopenia and a gradual reduction in serum immunoglobulin levels over 3 to 12 months of therapy. 7 Another recent study found an inhibitory effect of imatinib on the development of progenitor cell-derived dendritic cells (DCs) and demonstrated that DCs exposed to imatinib were less potent at inducing primary cytotoxic T-cell reactions against tumor antigens and recall antigens in vitro. 8 The molecular target of imatinib in DCs was not defined but a role for c-KIT inhibition appeared unlikely. This raises the possibility that imatinib could affect normal hematopoiesis and immune function through inhibition of additional TKs.Effects of imatinib on T-cell activation and function have not been well defined. However, TKs play a prominent role in T-cell receptor (TCR) signal transduction and thus it is conceivable that imatinib may interfere with this process. Physiologic activation of T lymphocytes in response to antigen is controlled by the TCR. 9,10 The TCR is comprised of ␣ and ␤ chains, the signaling subunits CD3 ⑀, ␥, and ␦ chains, and TCR . TCR binding to cognate foreign peptide bound to major histocompatibility complex (MHC) molecules on the surface of antigenpresenting cells (APCs) triggers a signaling cascade that includes activation of the TKs LCK and FYN. 11 LCK phosphorylates the immunoreceptor tyrosine-based activation motifs (ITAMs) on the TCR subunits to which ZAP70 is recruited. LCK activates ZAP70, which...

Purpose: The dual BCR-ABL/SRC kinase inhibitor dasatinib entered the clinic for the treatment of chronic myeloid leukemia and Ph + acute lymphoblastic leukemia. Because SRC kinases are known to play an important role in physiologicT-cell activation, we analyzed the immunobiological effects of dasatinib on T-cell function. The effect of dasatinib on multiple T-cell effector functions was examined at clinically relevant doses (1-100 nmol/L); the promiscuous tyrosine kinase inhibitor staurosporine was used as a comparator. Experimental Design: Purified human CD3 + cells and virus-specific CD8 + Tcells from healthy blood donors were studied directly ex vivo ; antigen-specific effects were confirmed in defined T-cell clones. Functional outcomes included cytokine production (interleukin-2, IFNg, and tumor necrosis factor a), degranulation (CD107a/b mobilization), activation (CD69 up-regulation), proliferation (carboxyfluorescein diacetate succinimidyl ester dilution), apoptosis/necrosis induction, and signal transduction. Results: Both dasatinib and staurosporine inhibited T-cell activation, proliferation, cytokine production, and degranulation in a dose-dependent manner. Mechanistically, this was mediated by the blockade of early signal transduction events and was not due to loss of T-cell viability. Overall, CD4 + T cells seemed to be more sensitive to these effects than CD8 + Tcells, and naBve Tcells more sensitive than memoryT-cell subsets. The inhibitory effects of dasatinib were so profound that all T-cell effector functions were shut down at therapeutically relevant concentrations. Conclusion: These findings indicate that caution is warranted with use of this drug in the clinical setting and provide a rationale to explore the potential of dasatinib as an immunosuppressant in the fields of transplantation and T-cell^driven autoimmune diseases.

The synthesis, biological, and pharmacological evaluations of 14beta-O-phenylpropyl-substituted morphinan-6-ones are described. The most striking finding of this study was that all of the compounds from the novel series of differently N-substituted 14beta-O-phenylpropylmorphinans acted as powerful opioid agonists. Even with N-substituents such as cyclopropylmethyl and allyl, which are usually associated with distinct antagonist properties, only agonists were obtained. Compared to morphine, the N-cyclopropylmethyl derivative 15 showed considerably increased potency in the in vivo assays in mice (600-fold in the tail-flick assay, 60-fold in the paraphenylquinone writhing test, and 400-fold in the hot-plate assay). Remarkably, most of the new ligands were nonselective and exhibited binding affinities in the subnanomolar range at opioid receptors (mu, kappa, delta), with the N-propyl derivative 19 displaying the highest affinity for the mu-receptor (K(i) = 0.09 nM).

Phenotypic differences in analgesic sensitivity to codeine (3-methoxymorphine) results from polymorphisms in cytochrome P450 -2D6, which catalyzes O-demethylation of codeine to morphine. However, O-demethylation reportedly is not required for analgesic activity of the 7,8-saturated codeine congeners dihydrocodeine, hydrocodone, and oxycodone. This study determined the potency and efficacy of these compounds and their demethylated derivatives to stimulate -and ␦-opioid receptor-mediated G-protein activation using agonist-stimulated guanosine 5Ј-O-(3-[35 S]thio)triphosphate ([ 35 S]GTP␥S) binding. Results showed that 7,8-saturated codeine congeners were more efficacious than codeine in activating -receptors, but only dihydrocodeine was more efficacious at ␦-receptors. Hydrocodone and oxycodone were ϳ10-fold more potent than codeine and dihydrocodeine at either receptor. Morphine-like compounds with a 3-hydroxy group were ϳ30-to 100-fold more potent than their 3-methoxy analogs at the -receptor, and these compounds generally exhibited greater efficacy (e.g., morphine produced 2-fold greater maximal stimulation than codeine). Removal of the N-methyl group did not affect efficacy or potency of codeine congeners to activate -receptors, whereas this modification generally increased efficacy but decreased potency of morphine congeners. At the ␦ receptor, morphine congeners showed greater potency and structuredependent differences in efficacy compared with codeine congeners, whereas removal of the N-methyl group had effects similar to those observed at the -receptor. These results demonstrate that 7,8-saturated codeine congeners are more efficacious than codeine, which may explain their lack of requirement for 3-O-demethylation in vivo. Nonetheless, because all 7,8-saturated codeine congeners were significantly less potent than their morphine derivatives, further research is needed to understand the relationship between metabolism and in vivo activity of these compounds.The opioid analgesic, codeine (3-methoxymorphine), undergoes several metabolic routes including N-and O-demethylation, as well as glucuronidation (Dayer et al., 1988;Mikus et al., 1991;Caraco et al., 1996;Yu et al., 2002). It is well established that codeine must be O-demethylated to morphine to produce analgesia in both humans (Chen et al., 1991) and rats (Mikus et al., 1991;Cleary et al., 1994). In humans, cytochrome P450 -2D6 (CYP-2D6) catalyzes this reaction, and individuals with dysfunctional allelic variants of this gene are phenotypically described as poor metabolizers (PMs) and are less sensitive to codeine. Individuals expressing multiple copies of active CYP-2D6 are extensive metabolizers (EMs) and are more sensitive to codeine. EMs can exhibit the PM phenotype, however, when codeine is coadministered along with a CYP-2D6 inhibitor such as quinidine. The requirement for O-demethylation is not surprising given that the reported K i values for binding to -opioid receptors is 200 times higher for codeine than for morphine (Chen et al., 1991...

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