AB0251 INCREASED ACCUMULATION OF ERYTHROCYTE METHOTREXATE POLYGLUTAMATES DURING EARLY PHASE SUBCUTANEOUS VERSUS ORAL METHOTREXATE TREATMENT OF RHEUMATOID ARTHRITIS PATIENTS
Authors: R. Hebing, I. Muller, M. Lin, S. Mahmoud, S. Heil, W. Lems, M. Nurmohamed, R. De Jonge, G. Jansen
Journal: Annals of the Rheumatic Diseases (2021)

Background: Optimal dosing of methotrexate (MTX) for individual rheumatoid arthritis (RA) patients to achieve adequate disease control is an ongoing challenge. Assessment of erythrocyte MTX-polyglutamates (PGs) levels has been employed as a tool to monitor clinical response of RA patients in the first 3-12 months of treatment and MTX-PG 2-4 and total MTX-PGs were associated with a lower DAS28 over 9 months. 1 However, data from earlier time points, MTX-PG 6 and per route of administration are unavailable. Objectives: To investigate the pharmacokinetics and -dynamics of erythrocyte MTX-PG accumulation in RA patients receiving oral or subcutaneous MTX in the early phase (1, 2, and 3 months) of MTX treatment initiation. Methods: In a clinical prospective cohort study (MeMo study (NTR7149)), newly diagnosed RA patients were administered oral (n=24) or subcutaneous (n=22) MTX, mostly according to the COBRA-light schedule (start 10 mg MTX, increased to 25 mg MTX in 8 weeks). At 1, 2, and 3 months after start of therapy, blood was collected and individual MTX-PGs (MTX-PG 1 – MTX-PG 6 ) were analyzed in erythrocytes at a minimal detection limit of 1 nmol/L, using a validated UHPLC-MS/MS method with labeled internal standards. 1 Dosing, concomitant treatments and DAS28-ESR assessments were in conformity with clinical practice. Adverse events were recorded. Results: 46 consecutive patients were included in this study; 76% female, mean age: 57.8 years, BMI: 25.8, 20% smokers, mean baseline DAS28-ESR: 3.5. Notwithstanding marked interpatient variability, patients starting subcutaneous MTX had accumulated significantly higher (approximately 2-fold) long chain MTX-PGs (MTX-PG 4-6 ) when compared to patients in the oral MTX group at 1 and 2 months (Figure 1A, Table 1). Similarly, MTX-PG 1-6 and MTX-PG 3 accumulation were higher in subcutaneous MTX-users at month 1 (p=0.022 and p=0.011) compared to the oral group (median 68.6 nmol/L (IQR:40.5) vs 51.9 (55.6) and 17.4 (11.1) vs 11.2 (15.6), respectively (Figure 1B, Table 1). Table 1. Linear regression of MTX-PG levels and administration route, corrected for age, baseline DAS28, smoking, BMI, eGFR and MTX dose. month ß (P-value ) 1 ß (P-value ) 2 ß (P-value ) 3 MTX-PG 1-6 1.65 (0.022) 1.51 (0.073) 1.30 (0.233) MTX-PG 1,2 1.13 (0.599) 1.19 (0.470) 1.12 (0.623) MTX-PG 3 1.75 (0.011) 1.51 (0.071) 1.19 (0.439) MTX-PG 4-6 1.97 (0.036) 2.04 (0.033) 1.55 (0.136) Mean MTX dose at baseline was 10.5mg (SD 1.5) for both groups, 15.4 (4.4) and 16.8 (1.8) at 1 month and 22.8 (3.9) and 22.4 (5.2) at 2 months for oral and subcutaneous use respectively. DAS28 decreased with 1.6 in the oral group and 1.1 in the subcutaneous group (p=0.382). With and without corrections for age, baseline DAS28, eGFR, MTX dose (1 month before sampling), smoking and BMI, no significant relation between MTX-PG concentrations and DAS28 was observed during the first 3 months of treatment. 43 patients reported any side effect, mostly headache and dizziness, which was similar in both groups and uncorrelated with MTX-PG levels. No association was found between MTX-PG 1 levels and number of days between timing of blood withdrawal and last administration. Figure 1. Erythrocyte long chain MTX-PG ( A ) and total MTX-PG ( B ) accumulation in RA patients of the first 3 months of oral ( C ) or subcutaneous ( D ) MTX administration. At 3 months, 18 patients using oral and 18 patients using subcutaneous MTX were still continuing MTX treatment. Medians and IQR are depicted. Conclusion: This study shows the feasibility of measuring erythrocyte MTX-PGs early on in the treatment of RA patients with MTX and demonstrated significantly higher accumulation of MTX-PGs following subcutaneous versus oral MTX administration. Early phase erythrocyte MTX-PG analyses may hold potential for positioning in optimizing individual patient MTX dose scheduling. References: [1]de Rotte MC, et al. Methotrexate polyglutamates in erythrocytes are associated with lower disease activity in patients with rheumatoid arthritis. Ann Rheum Dis 2015(74):408-14. Acknowledgements: We would like to thank all participating patients and Pfizer (grant 53233663 / WI230458). Disclosure of Interests: Renske Hebing Grant/research support from: Pfizer, Ittai Muller: None declared, Marry Lin: None declared, Sohaila Mahmoud: None declared, Sandra Heil: None declared, WIllem Lems: None declared, Michael Nurmohamed: None declared, Robert De Jonge: None declared, Gerrit Jansen: None declared