Pharmacokinetics of oral and subcutaneous methotrexate in red and white blood cells in patients with early rheumatoid arthritis: the methotrexate monitoring trial

Abstract

ObjectiveTo investigate the pharmacokinetics of methotrexate polyglutamate (MTX-PG) accumulation in red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs) in patients with early rheumatoid arthritis (RA) after oral and subcutaneous MTX treatment.MethodsIn a clinical prospective cohort study (Methotrexate Monitoring study), newly diagnosed patients with RA were randomised for oral or subcutaneous MTX. At 1, 2, 3 and 6 months after therapy initiation, blood was collected and RBCs and PBMCs were isolated. MTX-PG1-6concentrations were determined by mass spectrometry methods using stable isotopes of MTX-PG1-6as internal standards.Results43 patients (mean age: 58.5 years, 77% female) were included. PBMCs and RBCs revealed disparate pharmacokinetic profiles in both absolute MTX-PG accumulation levels and distribution profiles. Intracellular MTX-PG accumulation in PBMCs was significantly (p<0.001) 10-fold to 20-fold higher than RBCs at all time points, regardless of the administration route. MTX-PG distribution in PBMCs was composed of mostly MTX-PG1(PG1>PG2>PG3). Remarkably, the distribution profile in PBMCs remained constant over 6 months. RBCs accumulated mainly MTX-PG1and lower levels of MTX-PG2-5at t=1 month. After 3 months, MTX-PG3was the main PG-moiety in RBCs, a profile retained after 6 months of MTX therapy. Subcutaneous MTX administration results in higher RBC drug levels than after oral administration, especially shortly after treatment initiation.ConclusionsThis is the first study reporting disparate MTX-PG accumulation profiles in RBCs versus PBMCs in newly diagnosed patients with RA during 6 months oral or subcutaneous MTX administration. This analysis can contribute to improved MTX therapeutic drug monitoring for patients with RA.Trial registration numberNTR 7149.

Is methotrexate safe for men with an immune-mediated inflammatory disease and an active desire to become a father? Results of a prospective cohort study (iFAME-MTX)

“…MTXpg1–5 were detected in erythrocytes from all participants (figure 1A), consistent with MTX-pg accumulation profiles in erythrocytes of patients under MTX therapy and thus confirming their intake of MTX 12. In seminal fluid, mainly MTX-pg1 was detected with a median concentration of 184 nmol/L (IQR 39–265), whereas MTXpg2,3 were barely noticeable (figure 1B).…”

“…The concentration of testosterone, LH, FSH, inhibin B, sex hormone binding globulin (SHBG) and C reactive protein were evaluated. Erythrocytes and PBMCs were isolated using the protocol previously described 12 15…”

“…Considering that MTX-PG have never been measured in spermatozoa, we opted to measure MTX-PG in erythrocytes as a control measure for MTX adherence. The erythrocyte cell pellets are measured accordingly to our previously described validated LC-MS/MS method using custom-made stable isotopes of MTX-pg1-7 as internal standards 12 15. This method with minor alterations was also used to measure MTX-PG in spermatozoa and seminal fluid.…”

“…Lower FPGS activity and subsequent inefficient polyglutamylation is a well-known phenomenon associated with a rapid efflux of MTX from cells 11. MTX-PG have been detected in several human cells such as erythrocytes or peripheral blood mononuclear cells (PBMCs) and low levels of MTX-PG have been associated with increased resistance to therapy 12 13. In this regards, recent molecular studies have shown that a significant reduction of FPGS activity is associated with aberrant pre-mRNA splicing of this enzyme, including partial retention of intron 8 (8PR) and a higher ratio of FPGS 8PR over FPGS wild type (WT) 14.…”

Methotrexate Polyglutamates Exposure – Response Modeling in a Large Cohort of Rheumatoid Arthritis Patients Starting Methotrexate

“…We enrolled 251 patients from the Treatment in the Rotterdam Early Arthritis Cohort (tREACH) study and 101 MTX in Rotterdam (MTX-R) study patients, and 43 consecutive patients from the Methotrexate Monitoring (MeMo) study (Figure S1). 3,18,19 The selection comprised patients with RA of whom MTX levels were measured. In the MeMo study, patients were administered oral or subcutaneous MTX, whereas in the other two studies, mostly oral MTX was prescribed.…”