. 2016 Apr 1;18:79. doi: 10.1186/s13075-016-0971-8

Table 1.

Release of MTX and MTX-α peptides from DK226

Treatment	pH	Released concentration (ng/mL) MTX MTX-α-Phe MTX-α-Phe-Phe			% of released MTX	% peak area of MTX-α-Phe after 24-h incubation
Synovial tissue homogenate	4.0	8.82	BLQ^b	BLQ^c	1.2	0^e
Synovial tissue homogenate	7.4	BLQ^a	BLQ^b	BLQ^c	0	100
Synovial fluid	4.0	1.14	2.02 (1.53)^d	1.29 (0.783)^d	0.5	80.1
Synovial fluid	7.4	BLQ^a	BLQ^a	BLQ^a	0	100

DK226 was incubated in rabbit synovial tissue homogenate or synovial fluid at pH 4.0 or pH 7.4 for 24 h at 37 °C. Release of MTX and MTX-α peptides was measured by LC/Q-TOF-MS. MTX-α-Phe was used as a reference compound to assess the metabolic stability, and the percent peak area of intact MTX-α-Phe and MTX released from MTX-α-Phe were monitored by LC-UV

MTX methotrexate, Phe phenylalanine, BLQ below lower limit of quantification

^aBLQ (below LLOQ); <1 ng/mL

^bBLQ; <5 ng/mL

^cBLQ; <10 ng/mL

^dMTX-equivalent concentration

^ePercent peak area of MTX-α-Phe after 3-h incubation