ACS Medicinal Chemistry Letters
Page 4 of 5
catabolite, with the majority of the catabolite found to be the fully
DIPEA, N,N-Diisopropylethylamine; DMF, dimethylformamide;
DCM, dichloromethane; DMA< dimethylacetmide; DCE,
dichloroethane; Et3N, trimethylamine; EDC, 1-Ethyl-3-(3-
dimethylaminopropyl)carbodiimide; HOBt, hydroxybenzotriazole;
TFA, triflouoroacetic acid; EEDQ, N-ethoxycarbonyl-2-ethoxy-
1,2-dihydroquinoline; SEC, size-exclusion chromatography; CR,
complete regression.
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dipeptide cleaved aniline 13 which is known to be exquisitely
potent (4-20 pM) in many cell lines.12 Furthermore, aniline 13 was
identified as the only catabolite found when SCID mice bearing
FR tumors were treated with anti-FR IGN ADC 11a when those
tumors were excised, homogenized, and the catabolites were
extracted. Taken together, the presence of this cell permeable and
highly potent catabolite both in vitro and in vivo leads to the
observed high bystander and exceptional antitumor activity
described above.
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9
In conclusion, we prepared ADCs of IGNs possessing all four
diastereomers (11a-d) of an ala-ala dipeptide linker attached at a
central aniline of the potent catabolite 13. All ADCs, regardless of
stereochemistry, were found to be potent in vitro in high antigen
expressing cell lines, however, in lower expressing cell lines and in
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI:.
Detailed experimental procedures for all compounds, ADCs,
and catabolite studies. (PDF)
AUTHOR INFORMATION
Corresponding Author
Present Address
†Pharmaron, Inc., Waltham, MA 02451. ‡H3 Biomedicine,
Cambridge, MA 02139. §Foley Hoag, LLP, Boston, MA 02210-
2600. ⊥Takeda Pharmaceuticals, Cambridge, MA 02139.
Author Contributions
The manuscript was written through contributions of all authors.
All authors of submitting affiliation have given approval to the
final version of the manuscript.
Funding Sources
This study was supported by ImmunoGen, Inc.
ABBREVIATIONS
ADC, antibody-drug conjugate; PBD, pyrrolobenzodiazepine;
IGN, indolinobenzodiazepine; NHS, N-hydroxysuccinimide ester;
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