Simultaneous Quantification of Ivacaftor, Tezacaftor, and Elexacaftor in Cystic Fibrosis Patients' Plasma by a Novel LC-MS/MS Method.

The new breakthrough cystic fibrosis (CF) drug combination of ivacaftor (IVA), tezacaftor (TEZ), and elexacaftor (ELX), namely "caftor" drugs, directly modulates the activity and trafficking of the defective CF transmembrane conductance regulator protein (CFTR) underlying the CF disease. The role of therapeutic drug monitoring (TDM) of caftor drugs in clinical settings has recently been established. The availability of reliable and robust analytical methods for the quantification of IVA, TEZ, and ELX is essential to support dose-concentration-effect studies. We have developed and validated a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the rapid and simultaneous quantification of IVA, TEZ, and ELX from the plasma of CF patients. The method was based on a rapid extraction protocol from 50 µL human plasma and separation on a reversed-phase C-18 HPLC column after the addition of deuterated internal standards. Accurate analyte quantification using multiple reaction monitoring (MRM) detection was then obtained using a Thermofisher Quantiva triple-quadrupole MS coupled to an Ultimate 3000 UHPLC. The method has been validated following international (EMA) guidelines for bioanalytical method validation and has been tested on plasma samples from 62 CF patients treated with the three-drug combination IVA/TEZ/ELX, marketed as Kaftrio® or Trikafta®, in steady-state condition. The assay was linear over wide concentration ranges (0.008-12 mg/L) in plasma for IVA, TEZ, and ELX, suitable for a broad range of plasma concentrations, and accurate and reproducible in the absence of matrix effects. The stability of analytes for at least 30 days at room temperature could allow for cost-effective shipment and storage. On the same day of sample collection, a sweat test was evaluated for 26 associated patients' samples, FEV1 (%) for 58, and BMI was calculated for 62. However, Spearman correlation showed no correlation between Cthrough plasma concentrations of analytes (IVA, TEZ, ELX) and sweat test, FEV1 (%), or BMI. Our method proved to be suitable for TDM and could be helpful in assessing dose-concentration-response correlations in larger studies.

Clinical characterization, long-term follow-up, and response to treatment of patients with syndrome of undifferentiated recurrent fever (SURF).

OBJECTIVES: To describe a homogeneous group of patients with undifferentiated recurrent fevers followed-up in a tertiary referral center for systemic autoinflammatory diseases (SAIDs). METHODS: Patients with undifferentiated recurrent fevers seen at our Center from 2008 to 2021 and followed-up for at least one year were included in a retrospective study. Monogenic recurrent fevers, patients carrying variants of unknown origin and PFAPA (Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis) syndrome were excluded. RESULTS: Fifty patients (34 male, 16 female) were included in the study. The median age at onset was 3 years, and the median follow-up was 3.3 years. At baseline, arthralgia (70%) and abdominal pain (65%) were the most frequent manifestations. NSAIDs or steroids on demand had a variable and transient effect. Tonsillectomy was ineffective in the 10 patients (20%) that underwent surgery. Forty-eight patients (96%) were treated with colchicine. A complete response (absence of fever) was achieved in 31 patients (64.6%). Nine patients (18%) showed a partial response, with a median reduction of fever episodes per year of 72%. Nine patients (16.7%) were considered resistant to colchicine. The presence of generalized lymphadenopathy and, to a lesser extent, exudative tonsillitis was associated with a lack of response to colchicine. CONCLUSIONS: We describe the largest series of patients with syndrome of undifferentiated recurrent fever (SURF) reported in the literature so far. SURF should be considered as a distinct clinical entity in the context of multifactorial autoinflammatory diseases.