Investigation and Management of Immunoglobulin M- and Waldenström-Associated Peripheral Neuropathies.

The immunoglobulin M (IgM)-associated peripheral neuropathies (PN) are a heterogeneous group of disorders representing most paraproteinemic neuropathy cases. They are associated with IgM monoclonal gammopathy of undetermined significance (MGUS) or Waldenström macroglobulinemia. Establishing a causal link between a paraprotein and neuropathy can be challenging but is necessary to adopt an appropriate therapeutic approach. The most common type of IgM-PN is Antimyelin-Associated-Glycoprotein neuropathy, but half of the cases are of other causes. Progressive functional impairment is an indication for treatment, even when the underlying disorder is IgM MGUS, involving either rituximab monotherapy or combination chemotherapy to achieve clinical stabilization.

Development and clinical validation of a simple and fast UPLC-ESI-MS/MS method for simultaneous quantification of nine kinase inhibitors and two antiandrogen drugs in human plasma: Interest for their therapeutic drug monitoring.

Kinase inhibitors (KIs) and antiandrogen drugs (AAs) are oral anticancer drugs with narrow therapeutic index that exhibit high inter- and intra-individual variability. We describe here a UPLC-MS/MS method for the simultaneous quantification of nine KIs: cobimetinib, dasatinib, ibrutinib, imatinib, nilotinib, palbociclib, ruxolitinib, sorafenib and vemurafenib; two active metabolites of them: N-desmethyl imatinib, N-oxide sorafenib; and two AAs: abiraterone and enzalutamide; with short pre-treatment and run time in order to be easily used in clinical practice for their therapeutic drug monitoring (TDM) and facilitating pharmacokinetics and pharmacokinetics/pharmacodynamics studies. Plasma samples were prepared by a single-step protein precipitation. Analytes were separated on a Waters Acquity UPLC® T3 HSS C18 column by non-linear gradient elution; with subsequent detection by Xevo® TQD triple quadrupole tandem mass spectrometer in a positive ionization mode. Analysis time was 2.8 min per run, and all analytes eluted within 1.46-1.97 minutes. The analytical performance of the method in terms of specificity, sensitivity, linearity, precision, accuracy, matrix effect, extraction recovery, limit of quantification, dilution integrity and stability of analytes under different conditions met all criteria for a bioanalytical method for the quantification of drugs. The calibration curves were linear over the range of 1-500 ng/mL for abiraterone, dasatinib and ibrutinib; 5-500 ng/mL for cobimetinib and palbociclib; 10-5,000 ng/mL for imatinib, N-desmethyl imatinib, nilotinib, sorafenib, N-oxide sorafenib and ruxolitinib; 100-50,000 ng/mL for enzalutamide and 100-100,000 ng/mL for vemurafenib with coefficient of correlation above 0.995 for all analytes. This novel method was successfully applied to TDM in clinical practice.