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. 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 BLQb BLQc 1.2 0e
7.4 BLQa BLQb BLQc 0 100
Synovial fluid 4.0 1.14 2.02 (1.53)d 1.29 (0.783)d 0.5 80.1
7.4 BLQa BLQa BLQa 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

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