PURPOSE: To obtain a methotrexate derivative-containing medicine effective for glomerular nephritis and autoimmunity diseases such as systemic lupus erythematosus.

CONSTITUTION: A methotrexate derivative-containing medicine contains a compound of the formula (R1 is CH2, CH2CH2, CH2O, CH2S, CH2SO; R2 is H, a 1-4C lower alkyl, benzyl; R3 is COOR4, NHCOR5, CONR6R7, PO3H2, SO3H; R4 is H, a lower alkyl; R5 is phenyl; R6 is H, a lower alkyl; R7 is a lower alkyl, phenyl, etc.; n is 1-4) or its salt as an active ingredient. The medicine may orally or parenterally be administered, but the oral administration is preferable. The administration dose of the medicine is 0.01-100mg/day/adult. The compound of the formula includes N-(1-((2,4-diamino-6-pteridinyl)methyl) methyl)-3,4-dihydro-2H-1,4-benzothiazine-7-carbonyl)-L-α-aminoadipic acid.