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Determination of chemically reduced pyrrolobenzodiazepine SJG‐136 in human plasma by HPLC‐MS/MS: application to an anticancer phase I dose escalation study
Author(s) -
Wade Calcutt M.,
Lee Wooin,
Puzanov Igor,
Rothenberg Mace L.,
Hachey David L.
Publication year - 2008
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1268
Subject(s) - chemistry , chromatography , high performance liquid chromatography , dimer , pharmacokinetics , stereochemistry , pharmacology , organic chemistry , medicine
SJG‐136 1,1′‐[[(propane‐1,3‐diyl)dioxy]bis[(11a S )‐7‐methoxy‐2‐methylidene‐1,2,3,11a‐tetrahydro‐ 5H ‐pyr‐ rolo[2,1‐ c ][1,4]benzodiazepin‐5‐one]] (NSC 694501), is a bifunctional pyrrolobenzodiazepine (PBD) dimer that forms selective, irreversible, interstrand DNA cross‐links via exocyclic N2 atoms of two guanine bases, with a preference for 5′PuGATCPy binding sites. SJG‐136 is highly cytotoxic in human tumor cells in vitro and in human tumor xenograft models in vivo at subnanomolar concentrations and is currently in anticancer phase I clinical trials in the United Kingdom and United States. To support correlative pharmacokinetics studies, a highly sensitive HPLC‐MS/MS assay was developed and validated for the reliable quantitation of SJG‐136 in human plasma, using the structurally similar PBD dimer DSB‐120 as an internal standard. Chemical reduction of SJG‐136 to its corresponding amine (SJG‐136‐H 4 , [M + H] + m / z 561) improved HPLC peak resolution and sensitivity by minimizing complications that arose from the reactivity of the labile imine moieties. Plasma samples were processed by protein precipitation and centrifugal membrane dialysis; components were separated by HPLC using an Agilent Rapid Resolution HT 1.8 mm (2.1 mm × 50 mm) analytical column. The total analysis time from injection to injection was 11 min. Electrospray MS/MS detection of SJG‐136‐H 4 was based on the selected reaction monitoring (SRM) transition [M + H] + m / z 561 → 301. The analytical response ratio was linearly proportional to the plasma concentration of SJG‐136 over the nominal concentration range of 25 pg/ml to 250 ng/ml, with a coefficient of determination of r ≥ 0.999. The intrarun absolute % RE was ≤19.6, 14.2, and 14.0% at 0.056, 2.83, and 56.3 ng/ml, respectively. The corresponding % RSD was ≤14.9%, 9.01, and 4.59%. The interday % RSD was ≤2.72, 3.46, and 5.20%. The lower and upper limits of quantitation were 0.056 and 56 ng/ml, respectively; recovery of SJG‐136 from plasma was ≥ 62% across the validated concentration range. The sensitivity of the validated assay was sufficient to detect SJG‐136 in human subjects for up to 6 h after intravenous administration of 6 µg/m 2 , the starting dose of an NCI‐sponsored dose escalation study. Copyright © 2007 John Wiley & Sons, Ltd.