Novel Acid Labile COL1 Trityl-Linked Difluoronucleoside Immunoconjugates: Synthesis, Characterization, and Biological Activity
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- 作者：Vinod F. Patel ; Julie N. Hardin ; John M. Mastro ; Kevin L. Law ; John L. Zimmermann ; William J. Ehlhardt ; Joseph M. Woodland ; and James J. Starling
- 刊名：Bioconjugate Chemistry
- 出版年：1996
- 出版时间：July 1996
- 年：1996
- 卷：7
- 期：4
- 页码：497 - 510
- 全文大小：336K
- 年卷期：v.7,no.4(July 1996)
- ISSN：1520-4812
文摘
LY207702 (1) is a difluorinated purine nucleosidethat exhibits impressive antitumor activity inpreclinical models. This agent, however, also possessescardiotoxicity which limits the potential clinicalutility of this novel drug candidate. We therefore developedlinker chemistry whereby regioselectiveN6-tritylation of LY207702 (1) allowed this drug to becoupled to 
on.gif" BORDER=0 >-lysine amino groups of mAb'sreactive with human tumor-associated antigens. The resultingimmunoconjugates 3 possessedconjugation ratios ranging from 5 to 7 mol of LY207702/mol of mAb,minimal aggregate content (5-10%), and good immunoreactivity. The electronic nature ofsubstituents on the aromatic rings of thetrityl group dictated the degree of acid lability of the trityl linker.Increased electronic stabilizationof the transient trityl carbocation led to increase in the release rateof free drug, i.e., m-DMT 10a =p-DMT 10b > p-MMT 10d >p-T 10f. Consequently, the more acid labileDMT conjugates 3a and 3bproved to be the most potent cytotoxic agents, and the most stablep-T conjugate 3f exhibited theleast antitumor activity when evaluated in vitro andin vivo. p-MeT-linked conjugate3e, the moststable construct that retained excellent in vivo antitumoractivity, was selected for more extensiveevaluation. No detectable free drug or metabolite was observed inmouse plasma at a singleintravenous dose of p-MeT conjugate 3e, which wasconsistent with its predicted stability underphysiological conditions. This construct did, however, exhibitsignificant antigen-mediated antitumoractivity in vivo. No cardiotoxicity was detected inmice dosed with conjugate 3e (6 mg/kg free drugcontent per day for 21 days) equivalent to ~8 times the total doserequired for complete regression ofwell-established (~1 g) HC1 human colon tumor xenografts in nudemice. Cardiotoxicity was inducedin 20% of free drug 1 treated group at the equivalent dose.Cardiomyopathy was, however, observedwhen the dose of conjugate 3e was increased to 8 mg/kg perday for 21 days. These data suggest thatantitumor activity of LY207702 (1) was maintained and itscardiotoxic potential reduced when thisagent was administered to human tumor xenograft bearing nude mice asCOL1-N6-p-MeT-207702conjugate 3e.
on.gif" BORDER=0 >-lysine amino groups of mAb'sreactive with human tumor-associated antigens. The resultingimmunoconjugates 3 possessedconjugation ratios ranging from 5 to 7 mol of LY207702/mol of mAb,minimal aggregate content (5-10%), and good immunoreactivity. The electronic nature ofsubstituents on the aromatic rings of thetrityl group dictated the degree of acid lability of the trityl linker.Increased electronic stabilizationof the transient trityl carbocation led to increase in the release rateof free drug, i.e., m-DMT 10a =p-DMT 10b > p-MMT 10d >p-T 10f. Consequently, the more acid labileDMT conjugates 3a and 3bproved to be the most potent cytotoxic agents, and the most stablep-T conjugate 3f exhibited theleast antitumor activity when evaluated in vitro andin vivo. p-MeT-linked conjugate3e, the moststable construct that retained excellent in vivo antitumoractivity, was selected for more extensiveevaluation. No detectable free drug or metabolite was observed inmouse plasma at a singleintravenous dose of p-MeT conjugate 3e, which wasconsistent with its predicted stability underphysiological conditions. This construct did, however, exhibitsignificant antigen-mediated antitumoractivity in vivo. No cardiotoxicity was detected inmice dosed with conjugate 3e (6 mg/kg free drugcontent per day for 21 days) equivalent to ~8 times the total doserequired for complete regression ofwell-established (~1 g) HC1 human colon tumor xenografts in nudemice. Cardiotoxicity was inducedin 20% of free drug 1 treated group at the equivalent dose.Cardiomyopathy was, however, observedwhen the dose of conjugate 3e was increased to 8 mg/kg perday for 21 days. These data suggest thatantitumor activity of LY207702 (1) was maintained and itscardiotoxic potential reduced when thisagent was administered to human tumor xenograft bearing nude mice asCOL1-N6-p-MeT-207702conjugate 3e.