A Case Series and Literature Review of Isavuconazole Use in Pediatric Patients with Hemato-oncologic Diseases and Hematopoietic Stem Cell Transplantation.

We analyzed the use of isavuconazole (ISA) as treatment or prophylaxis for invasive fungal disease (IFD) in children with hemato-oncologic diseases. A multicentric retrospective analysis was performed among centers belonging to the Italian Association for Pediatric Hematology and Oncology (AIEOP). Pharmacokinetic (PK) monitoring was applied by a high-performance liquid chromatography-tandem mass spectrometry (HLPC-MS/MS) assay. Twenty-nine patients were studied: 10 during chemotherapy and 19 after allogeneic hematopoietic stem cell transplantation (HSCT). The patients consisted of 20 males and 9 females with a median age of 14.5 years (age range, 3 to 18 years) and a median body weight of 47 kg (body weight range, 15 to 80 kg). ISA was used as prophylaxis in 5 patients and as treatment in 24 cases (20 after therapeutic failure, 4 as first-line therapy). According to European Organization for Research and Treatment of Cancer (EORTC) criteria, we registered 5 patients with proven IFD, 9 patients with probable IFD, and 10 patients with possible IFD. Patients with a body weight of <30 kg received half the ISA dose; the others received ISA on the adult schedule (a 200-mg loading dose every 8 h on days 1 and 2 and a 200-mg/day maintenance dose); for all but 10 patients, the route of administration switched from the intravenous route to the oral route during treatment. ISA was administered for a median of 75.5 days (range, 6 to 523 days). The overall response rate was 70.8%; 12 patients with IFD achieved complete remission, 5 achieved partial remission, 5 achieved progression, and 3 achieved stable IFD. No breakthrough infections were registered. PK monitoring of 17 patients revealed a median ISA steady-state trough concentration of 4.91 mg/liter (range, 2.15 to 8.54 mg/liter) and a concentration/dose (in kilograms) ratio of 1.13 (range, 0.47 to 3.42). Determination of the 12-h PK profile was performed in 6 cases. The median area under the concentration-time curve from 0 to 12 h was 153.16 mg·h/liter (range, 86.31 to 169.45 mg·h/liter). Common Terminology Criteria for Adverse Events grade 1 to 3 toxicity (increased transaminase and/or creatinine levels) was observed in 6 patients, with no drug-drug interactions being seen in patients receiving immunosuppressants. Isavuconazole may be useful and safe in children with hemato-oncologic diseases, even in the HSCT setting. Prospective studies are warranted.

Changes in actin lysine reactivities during polymerization detected using a competitive labeling method.

We have studied the structure of actin by measuring the relative reactivities of lysines with acetic anhydride using a competitive labeling procedure comparing monomeric globular actin. monomeric actin in the presence of salt, and filamentous actin polymerized in 100 mM NaCl and 100 mM NaCl, 2 mM MgCl2. We have identified 12 of the 19 lysines: 18, 50, 61, 68, 113, 191, 237, 290, 315, 325, 327, and 358. In all conditions, Lys (325, 327) is the most reactive. In globular actin, Lys 18, 191, 290, 314. and 358 are less than 20% as reactive as Lys (325, 327); the remaining have intermediate reactivities. On polymerization in the presence of NaCl and Mg2+, lysines 50, 61, 68, 113, and 290 become less reactive relative to Lys (325, 327). The changes in Lys 50, 61, and 113 are due largely to the polymerization event whereas those in Lys 68 and 290 appear to be an effect of Mg2+. Lys 18, 191, and 358 increase in relative reactivity when cation is added to the monomer and then become less reactive in the polymer, showing no large overall change in reactivity relative to the monomer in the absence of salt. Lysines that are reduced in reactivity upon polymerization indicate possible contact regions between actin monomers in the filament in the NH2-terminal third of the protein.

Study of the structure of troponin-I by measuring the relative reactivities of lysines with acetic anhydride.

A competitive labeling method that measures the relative reactivity of lysines was used to study the structure of troponin-I. Troponin-I was acetylated free and complexed with troponin-C and troponin-T in the native state with [3H]acetic anhydride. The [3H]troponin-I was combined with [14C]troponin-I that had been acetylated in 6 M guanidine HCl and completely chemically labeled. Peptides containing labeled lysines were isolated following digestion with trypsin and Staphylococcus aureus protease and identified in the published sequence. The 3H/14C ratio of these peptides was used as a measure of the relative reactivity of the lysines. Troponin-I contains 24 lysines; we have identified 23 of these in 16 peptides. When troponin-I is labeled in a native complex, the lysines in the region from residues 40 to 98 are influenced: five become relatively less reactive (40, 65, 70, 78, and 90) and three become relatively more reactive (84, 87), and 98). All of these changes except Lys 70 can be seen when troponin-I binds to troponin-T. Lys 70 is reduced in reactivity when it binds to troponin-C. The lysines that appear to be important in binding of troponin-I to troponin-T are influenced by the binding of Ca2+ to troponin-C in the native troponin complex (in the presence of 2 mM MgCl2), suggesting for the first time that the troponin-IT interaction is affected by Ca2+.