Severe pleural effusion associated with nilotinib for chronic myeloid leukaemia: cross-intolerance with tyrosine kinase inhibitors.

Nilotinib is used as standard treatment in managing chronic myeloid leukaemia (CML). A 23-year-old man with CML and on nilotinib was admitted to the intensive care unit due to respiratory failure. Three years prior, he developed pleural effusion from dasatinib therapy thus, his CML regimen was changed to nilotinib. Although the pleural effusion had once improved, the chest imaging revealed left-dominant bilateral pleural effusion. Endotracheal intubation and left thoracic drainage were performed. Nilotinib treatment was discontinued, and approximately 60 hours later, nilotinib concentrations of 927 and 2092 ng/mL were determined in his blood and pleural effusion, respectively. Severe pleural effusion may be induced in patients administering nilotinib, and nilotinib concentrations in blood and pleural effusion can be elevated in patients with nilotinib-related pleural effusion. Cross-occurrence of pleural effusions needs to be monitored precisely, especially in patients who are switched to other tyrosine kinase inhibitors after dasatinib treatment.

Crystal structures of a bacterial dipeptidyl peptidase IV reveal a novel substrate recognition mechanism distinct from that of mammalian orthologues.

Dipeptidyl peptidase IV (DPP IV, DPP4, or DAP IV) preferentially cleaves substrate peptides with Pro or Ala at the P1 position. The substrate recognition mechanism has been fully elucidated for mammalian DPP IV by crystal structure analyses but not for bacterial orthologues. Here, we report the crystal structures of a bacterial DPP IV (PmDAP IV) in its free form and in complexes with two kinds of dipeptides as well as with a non-peptidyl inhibitor at 1.90 to 2.47 Å resolution. Acyl-enzyme intermediates were observed for the dipeptide complexes of PmDAP IV, whereas tetrahedral intermediates were reported for the oligopeptide complexes of mammalian DPP IVs. This variation reflects the different structural environments of the active site Arg residues, which are involved in the recognition of a substrate carbonyl group, of mammalian and bacterial enzymes. A phylogenetic analysis revealed that PmDAP IV is a closer relative of dipeptidyl peptidases 8 and 9 (DPP8 and DPP9, DPP IV-family enzymes) than DPP IV. These results provide new insights into the substrate recognition mechanism of bacterial DAP IVs and may assist in the development of selective inhibitors for DAP IVs from pathogenic asaccharolytic bacteria, which utilise proteins or peptides as an energy source.

Periplasmic form of dipeptidyl aminopeptidase IV from Pseudoxanthomonas mexicana WO24: purification, kinetic characterization, crystallization and X-ray crystallographic analysis.

Dipeptidyl aminopeptidase IV (DAP IV or DPP IV) from Pseudoxanthomonas mexicana WO24 (PmDAP IV) preferentially cleaves substrate peptides with Pro or Ala at the P1 position [NH2-P2-P1(Pro/Ala)-P1'-P2'…]. For crystallographic studies, the periplasmic form of PmDAP IV was overproduced in Escherichia coli, purified and crystallized in complex with the tripeptide Lys-Pro-Tyr using the hanging-drop vapour-diffusion method. Kinetic parameters of the purified enzyme against a synthetic substrate were also determined. X-ray diffraction data to 1.90 Šresolution were collected from a triclinic crystal form belonging to space group P1, with unit-cell parameters a = 88.66, b = 104.49, c = 112.84 Å, α = 67.42, ß = 68.83, γ = 65.46°. Initial phases were determined by the molecular-replacement method using Stenotrophomonas maltophilia DPP IV (PDB entry 2ecf) as a template and refinement of the structure is in progress.