Rapid and efficient tetrazine-induced drug release from highly stable benzonorbornadiene derivatives

Abstract

A novel class of bioorthogonal release reactions based on benzonorbornadiene derivatives was developed. These carrier molecules are highly stable at physiological conditions, but react rapidly with 1,2,4,5-tetrazines, and near-quantitatively release cargo molecules such as drugs and optical reporters.

Stable Pyrrole‐Linked Bioconjugates through Tetrazine‐Triggered Azanorbornadiene Fragmentation

“…This value is similar to the one determined for iEDDA ligation between DPTz and azanorbornene of type C (Scheme ) . Similar reaction rates were also reported for iEDDA reactions with aza/oxabenzonorbornadienes . Finally, [2.2.1]bicyclic analogues ( 7 — 9 ) reacted with 10 in a similar manner to 2 (see Scheme S3).…”

“…More recently, an alternate strategy (in which a specific bond is cleaved instead of formed) has been proposed and used for the controlled activation of proteins and prodrugs in cells and animals . The reaction between aza‐ and oxa‐benzonorbornadienes with tetrazines to afford isoindoles and isobenzofurans, respectively (Scheme ), which was reported by Warrener in the 1970’s, was further developed as a bioorthogonal bond‐cleavage reaction, and used for drug activation and signal amplification in nucleic acid templated detection of microRNA . This transformation proceeds through a three‐step cascade reaction that is initiated by ligation between the strained alkene of the heterobenzonorbornadiene system A and a tetrazine by means of an iEDDA reaction (Scheme ).…”

Dissociative Bioorthogonal Reactions

“…Isoindoles and isobenzofurans are high‐energy molecules, and we hypothesized that leaving groups connected via a methylene to the heterocyclic ring would spontaneously dissociate. We designed benzonorbornadienes with carbamate leaving groups attached via a methylene linker to the bridgehead position (Scheme ) . These molecules are stable in serum but readily react with tetrazines to eliminate the corresponding leaving group from the isoindole/isobenzofuran intermediate.…”

“…We designed benzonorbornadienes with carbamate leaving groups attached via am ethylene linker to the bridgehead position( Scheme 8). [66] These molecules are stable in serum but readily react with tetrazines to eliminate the corresponding leaving group from the isoindole/isobenzofurani ntermediate. Although the bimolecular reactionw as slower (k 2 0.2 m À1 s À1 ) than that of tetrazinesr eacting with trans-cyclooctene or isocyanides, the releasew as rapid and high-yielding.…”

The Emerging Role of Tetrazines in Drug‐Activation Chemistries

“…Franzini reported an alternative approach using benzonorbornadiene derivatives that were linked through a carbamate to doxorubicin (Scheme ) . Strained benzonorbornadiene dienophiles displayed high stability under physiological conditions and similar reactions rates to the vinyl ethers ( k 2 =0.004–0.190 m −1 s −1 ).…”