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Selective Drug Delivery Using Targeted Enzymes For Prodrug Activation
Published in Siegfried Matzku, Rolf A. Stahel, Antibodies in Diagnosis and Therapy, 2019
Nathan O. Siemers, Peter D. Senter
One of the more exciting prospects for mAb–enzyme/prodrug therapy is the production of catalytic antibodies (known as abzymes) that are capable of effecting prodrug activation. Typically these agents are created by immunization of mice with a transition state analog of the reaction that is desired, followed by isolation of active antibodies by hybridoma techniques. The first report described a catalytic antibody capable of releasing chloramphenicol from an ester prodrug (Miyashita et al., 1993). Other workers have reported catalytic antibodies capable of activating prodrugs of 5-fluorodeoxyuridine and nitrogen mustards (Campbell et al., 1994; Wentworth et al., 1996).
Positive Selection of B-Cell Repertoire, Idiotype Networks and Immunological Memory
Published in Maurizio Zanetti, J. Donald Capra, The Antibodies, 2002
Maryse Brait, Georgette Vansanten, Annette Van Acker, Carl De Trez, Chantal Masungi Luko, Christian Wuilmart, Oberdan Leo, Robert Miller, Roy Riblet, Jacques Urbain
Also some recent examples using abzymes are particularly striking [31]. BALB/C mice were immunized with Bacillus ß-lactamase. From 150 monoclonal antibodies, one was chosen to immunize, an MAb that significantly inhibited the enzyme. All antibodies induced were accompanied by a significant increase of ß-lactamase activity. One isolated hybridoma from Ab2 was able to hydrolyze peni-cillinic and cephalosporinic substrates with Michaelis-Menten kinetics. So starting with an enzyme antigen, it is possible to obtain anti-idiotypic antibodies, which exhibit enzymatic properties.
Some Underlying Physical Principles
Published in Clive R. Bagshaw, Biomolecular Kinetics, 2017
Assuming that the bond-breaking or forming step associated with S being converted to P has the same natural vibration frequency in the two pathways (on the order of 1013 s−1), the observation that the overall rate of the enzyme-catalyzed reaction, limited by ES to EP in our example, is faster than the uncatalyzed S to P rate indicates that the concentration of ES‡ must exceed S‡ (note the use of S for substrate and S for entropy). Hence, although entry into the transition state is unfavorable in both cases, . This in turn requires that E binds to S‡ more tightly than to S to maintain thermodynamic balance around the cycle . Therefore, the enzyme active site must be complementary to the transition-state rather than the substrate. From consideration of the reverse reaction, it also follows that E binds more tightly to ES‡ than P. It is evident that if the enzyme were complementary to P, the formation of EP might be favored when starting with S, but EP would show little tendency to dissociate, so the net rate of the catalytic cycle would be less than optimal. The argument that enzymes are complementary to the transition state was put forward by Pauling [110] and was tested by the development of tight-binding inhibitors of specific enzyme-catalyzed reactions based on the expected structure of the transition-state [94]. Furthermore, antibodies raised against such model transition state-like molecules display some enzyme activity toward the original substrate [111]. The realization of such abzymes supports the principles of transition-state stabilization, but their catalytic activity is much poorer than natural enzymes, indicating that other factors are important in enhancing the reaction rate [85]. Note that for an enzyme that has two substrates, A and B, which form a ternary complex EAB prior to the chemical step (Section 4.2), a transition-state analog of the form of an A----B complex will likely have a higher affinity for E than A or B alone, as discussed in Figure 3.2. Resolving the increase in affinity due to the resemblance to the transition state from that arising from its bifunctional nature is not straightforward.
Prodrugs for targeted cancer therapy
Published in Expert Review of Anticancer Therapy, 2019
Carla Souza, Diogo Silva Pellosi, Antonio Claudio Tedesco
The antibody-directed abzyme prodrug therapy (known as ADAPT) has been applied for this purpose. It avoids any additional antibody purification stages and reduces the enzymatic activity of the antibody with the conjugate [3,131]. In this case, bacterial enzymes are replaced with catalytic antibodies (known as abzymes) using recombinant DNA technology, producing a fusion protein with specific characteristics to activate the prodrug. The conjugate antibody-ß-lactamase fusion protein, for example, for the activation of cephalosporin prodrugs, was developed by fusion of ß-lactamase to a single-chain fragment (scFv) based on antibody CC49. In addition, a cyclic RGD4C peptide was fused into the NH2 terminus of ß-lactamase, known to target integrin αvβ3 [3]. This conjugate demonstrates lower immunogenicity than intact antibodies, better tissue penetration, and more specific activation of the prodrug, which results in a high local concentration of the drug in the cancer tissue.