Staurosporine

Actinomycetes are prolific producers of pharmacologically important compounds accounting for about 70% of the naturally derived antibiotics that are currently in clinical use. In this study, we report on the isolation of Streptomyces sp. strains from Mediterranean sponges, on their secondary metabolite production and on their screening for anti-infective activities. Bioassay-guided isolation and purification yielded three previously known compounds namely, cyclic depsipeptide valinomycin, indolocarbazole alkaloid staurosporine and butenolide. This is the first report of the isolation of valinomycin from a marine source. These compounds exhibited novel anti-parasitic activities specifically against Leishmania major (valinomycin IC(50) < 0.11 microM; staurosporine IC(50) 5.30 microM) and Trypanosoma brucei brucei (valinomycin IC(50) 0.0032 microM; staurosporine IC(50) 0.022 microM; butenolide IC(50) 31.77 microM). These results underscore the potential of marine actinomycetes to produce bioactive compounds as well as the re-evaluation of previously known compounds for novel anti-infective activities.

For a long time necrosis was thought to be an uncontrolled process but evidences recently have revealed that necrosis can also occur in a regulated manner. Necroptosis, a type of programmed necrosis is defined as a death receptor-initiated process under caspase-compromised conditions. The process requires the kinase activity of receptor-interacting protein kinase 1 and 3 (RIPK1 and RIPK3) and mixed lineage kinase domain-like protein (MLKL), as a substrate of RIPK3. The further downstream events remain elusive. We applied known inhibitors to characterize the contributing enzymes in necroptosis and their effect on cell viability and different cellular functions were detected mainly by flow cytometry. Here we report that staurosporine, the classical inducer of intrinsic apoptotic pathway can induce necroptosis under caspase-compromised conditions in U937 cell line. This process could be hampered at least partially by the RIPK1 inhibitor necrotstin-1 and by the heat shock protein 90 kDa inhibitor geldanamycin. Moreover both the staurosporine-triggered and the classical death ligand-induced necroptotic pathway can be effectively arrested by a lysosomal enzyme inhibitor CA-074-OMe and the recently discovered MLKL inhibitor necrosulfonamide. We also confirmed that the enzymatic role of poly(ADP-ribose)polymerase (PARP) is dispensable in necroptosis but it contributes to membrane disruption in secondary necrosis. In conclusion, we identified a novel way of necroptosis induction that can facilitate our understanding of the molecular mechanisms of necroptosis. Our results shed light on alternative application of staurosporine, as a possible anticancer therapeutic agent. Furthermore, we showed that the CA-074-OMe has a target in the signaling pathway leading to necroptosis. Finally, we could differentiate necroptotic and secondary necrotic processes based on participation of PARP enzyme.

Relationships between ligand binding and the shapes of the binding sites in families of homologous enzymes are investigated by comparing matrices of distances between key binding site atoms. Multiple linear regression is used to help identify key distances that influence ligand binding affinity. In order to illustrate the utility of this generic approach, we study protein kinase binding sites for ATP and the promiscuous competitive inhibitor, staurosporine. We show that the size of the gatekeeper residue and the closure between the first glycine of the GXGXXG motif and the aspartate of the DFG loop act together to promote tight binding. Our web-based tool, 'mapping analogous hetero-atoms onto residue interactions' (MAHORI), indicates that the greater the number of hydrogen bonds made by the kinase around the methylamine group of staurosporine, the tighter the binding. The conservation of surrounding atoms identified using our novel grid-based method clearly demonstrates that the most structurally conserved part of the binding site for staurosporine is the main chain of the hinge region. The critical role of interactions that are not dependent on side-chain identities is consistent with the promiscuous nature of this inhibitor.

To determine midostaurin and posaconazole plasma concentrations and investigate adverse events (AEs) resembling drug-drug interactions (DDI) when both drugs were administered concomitantly during induction chemotherapy for acute myeloid leukemia (AML). Patients with FLT3-mutated AML who received midostaurin and posaconazole concomitantly between May 2019 and December 2022 were included and followed up to March 2023. Twice-weekly trough levels for midostaurin and posaconazole were measured with validated liquid chromatography-tandem mass spectrometry methods. Potential DDIs were independently reviewed by two physicians and attributed using the Drug Interaction Probability Scale (DIPS). Population pharmacokinetics analysis was done via nonlinear mixed-effect modeling. In 29 patients, concentrations ranged from 0.6 to 24.5 mg/L for midostaurin and from <30 to 2,572 µg/L for posaconazole. A total of 375 AEs in 66 midostaurin cycles, with 280 AEs classified as grade ≥3, were recorded. Probable DDI with a DIPS score of ≥5 was attributed in 14/375 AEs; no highly probable AEs were registered. Eight AEs led to dose modification or discontinuation of midostaurin in seven patients. Clearance for midostaurin during co-administration with posaconazole was 0.52 L/h (95% CI, 0.42-0.62 L/h). A breakthrough fungal infection was recorded in eight patients (27.5%). DDI of midostaurin and posaconazole is clinically meaningful but infrequent. High inter- and intra-individual variabilities of midostaurin and posaconazole plasma exposure were observed. Midostaurin clearance was delayed during co-administration. Midostaurin therapeutic drug monitoring may serve for decision-making when DDI with CYP3A4 inhibitors is suspected.