Transient Low-Dose Methotrexate Induces Tolerance to Murine Anti-Thymocyte Globulin and Together They Promote Long-Term Allograft Survival

Abstract

Rabbit anti-thymocyte globulin (Thymoglobulin) effectively treats transplant rejection but induces anti-rabbit Ab responses, which limits routine readministration. Aiming to tolerize anti-rabbit responses, we coadministered a brief methotrexate regimen with a murine version of Thymoglobulin (mATG) for effects on anti-mATG Abs and cardiac allotransplantation in mice. Although both single and three courses of methotrexate could significantly inhibit anti-drug Ab titers to repeated mATG treatment, surprisingly, the single course given at the first mATG administration was most effective (>99% reduction). The transient methotrexate treatment also significantly improved pharmacokinetics and pharmacodynamics of repeated mATG administration. In the cardiac allograft model, the combination of transient mATG and methotrexate given only at the time of transplant dramatically improved allograft survival (>100 d) over either agent alone (<30 d). Anti-drug Ab titers were reduced and mATG exposure was increased which resulted in prolonged rather than enhanced mATG-mediated effects when combined with methotrexate. Moreover, methotrexate administration significantly reduced alloantibodies, suggesting that methotrexate not only decreases anti-drug Ab responses but also reduces Ab responses to multiple tissue-derived alloantigens simultaneously. These data suggest that mATG and methotrexate together can provide long-term allograft survival potentially through the induction of immune tolerance.

Transient Low-Dose Methotrexate Generates B Regulatory Cells That Mediate Antigen-Specific Tolerance to Alglucosidase Alfa

“…In the context of murine-specific antithymocyte globulin (mATG), a single cycle of three daily doses of methotrexate at the initiation of monthly mATG treatment more effectively reduced ADA and enhanced mATG pharmacodynamic activity than three consecutive cycles of methotrexate (29). Our present investigation of single-versus threecycle methotrexate in rhGAA tolerance demonstrated equivalent ADA reduction by both regimens.…”

“…Recently, low-dose, methotrexate induction treatment has been shown to induce immune tolerance to protein therapies in several different mouse models (27)(28)(29). In the context of murine-specific antithymocyte globulin (mATG), a single cycle of three daily doses of methotrexate at the initiation of monthly mATG treatment more effectively reduced ADA and enhanced mATG pharmacodynamic activity than three consecutive cycles of methotrexate (29).…”

“…Starting at week 12, each group of animals was also treated monthly with mATG (5 mg/kg, i.p.). Monthly treatments of mATG in C57BL/6 mice generate robust Ab responses (29), and thus enabled our investigation of the Ag-specific nature of methotrexate-induced immune tolerance. Methotrexate reduced anti-rhGAA-specific titers by 78% as measured by AUC ( Fig.…”

“…Our laboratory previously demonstrated that a low-dose induction regimen of methotrexate can reduce ADA responses against different protein therapies in mice and induce immune tolerance in normal and disease settings (27)(28)(29). Low-dose methotrexate induction treatment was subsequently included in a clinical immune tolerance protocol that coadministered the B cell-depleting agent, Rituximab, with optional IVIG (30)(31)(32).…”

Fatal Thrombotic Thrombocytopenic Purpura in a Psoriasis Patient Treated with Ustekinumab and Methotrexate

“…MTX, indeed has been shown to reduce the immunogenicity in response to monoclonal antibody therapies in chronic inflammatory diseases (10,11). The mechanism whereby MTX acts on the immune response has not been fully demonstrated; however, suppression of early T-and B-cell expansion may be responsible for modulation of the immune response (12).…”