Antibody-carboxypeptidase G2 Conjugate

As a professional service provider in antibody-directed enzyme prodrug therapy (ADEPT) design and preparation, Creative Biolabs offers customized antibody-carboxypeptidase G2 conjugate development services with optimized enzyme and antibody conjugation strategies.

Carboxypeptidase G2

Carboxypeptidase G2 (CPG2) is a bacterial, zinc-dependent exopeptidase with a molecular weight of 41.8 kDa. Two subunits of it form a natural homodimer, each of which contains two zinc ions which are essential for catalysis. CPG2 has a natural affinity for the hydrolysis of folates, which has made it ideal for controlling the side effects of high-dose chemotherapy with methotrexate. Some pioneering work with antibody-CPG2 conjugates has confirmed the potential of ADEPT from bench to bedside. The prodrug para-N-bis (2-chloroethyl) aminobenzoyl glutamic acid and its benzoic acid mustard derivative, para-N-bis (2-chloroethyl) aminobenzoic acid, were synthesized by a modification of the method in 1962. Cleavage of the glutamic acid moiety was performed with CPG2 conjugated to a monoclonal antibody to yield a potent drug to kill tumor cell specifically.


CPG2 could catalyze the hydrolytic cleavage of L-glutamic acid from folates. It’s worth saying that CPG2 could avoid the risk of prodrug activation at nontumour sites as no human analogue existed. The prodrug 4-[N, N-bis(2-chloroethyl) amino] benzoyl-L-glutamic acid is cleaved by CPG2 and thus yields the glutamic acid and 4-[N, N-bis(2-chloroethyl) amino] benzoic acid. The drug is a bifunctional alkylating agent in which the activating effect of the ionized carboxyl function is masked through an amide bond to the glutamic acid residue. The prodrug is designed to be activated to their corresponding bifunctionally alkylating benzoic acid derivatives at the tumor site by prior administration of a monoclonal antibody-enzyme conjugate.

Benzoic acid mustard prodrugs that are substrates for CPG2. A) Mechanism of cleavage of benzoic acid mustards by CPG. B) Alternative mustard functional groups. Fig.1 Benzoic acid mustard prodrugs that are substrates for CPG2. A) Mechanism of cleavage of benzoic acid mustards by CPG. B) Alternative mustard functional groups. (Melton, 1996)

Carboxypeptidase G2-based ADEPT

The use of CPG2 as the enzyme of ADEPT is under active development and evaluation.

The specific targeting capability of a monoclonal antibody scFv mAb is realized by a distinctive ADEPT which is composed of a humanized monoclonal antibody. It could target tumor cell antigen residues with a nontoxic prodrug which is administered and activated by the enzyme to the toxic drug at the tumor site. A single chain Fv (scFv) antibody against carcinoembryonic antigen (CEA) has been constructed to achieve ADEPT in CEA-producing tumors. It has been demonstrated that intravenous injection of purified MFE-23: CPG2 into nude mice bearing CEA-positive LS174T human colon adenocarcinoma xenografts has the potential to improve clinical efficiency for ADEPT.

Mechanism of ADEPT action. Fig.2 Mechanism of ADEPT action.

Creative Biolabs is dedicated to helping clients develop antibody-CPG2 conjugate using readily available or customized linkers in a timely and cost-effective manner. Our high-quality services and products will contribute greatly to the success of your projects. Creative Biolabs also provides other various services regarding ADEPT development. Please contact us for more information and a detailed quote.


  1. Melton, R. G.; Sherwood, R. F. Antibody-enzyme conjugates for cancer therapy. JNCI: Journal of the National Cancer Institute. 1996, 88(3-4), 153-165.

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