Development of MGD007, a gpA33 x CD3-Bispecific DART Protein for T-Cell Immunotherapy of Metastatic Colorectal Cancer

Abstract

We have developed MGD007 (anti-glycoprotein A33 x anti-CD3), a DART protein designed to redirect T cells to target gpA33 expressing colon cancer. The gpA33 target was selected on the basis of an antibody-based screen to identify cancer antigens universally expressed in both primary and metastatic colorectal cancer specimens, including putative cancer stem cell populations. MGD007 displays the anticipated-bispecific binding properties and mediates potent lysis of gpA33-positive cancer cell lines, including models of colorectal cancer stem cells, through recruitment of T cells. Xenograft studies showed tumor growth inhibition at doses as low as 4 μg/kg. Both CD8 and CD4 T cells mediated lysis of gpA33-expressing tumor cells, with activity accompanied by increases in granzyme and perforin. Notably, suppressive T-cell populations could also be leveraged to mediate lysis of gpA33-expressing tumor cells. Concomitant with CTL activity, both T-cell activation and expansion are observed in a gpA33-dependent manner. No cytokine activation was observed with human PBMC alone, consistent with the absence of gpA33 expression on peripheral blood cell populations. Following prolonged exposure to MGD007 and gpA33 positive tumor cells, T cells express PD-1 and LAG-3 and acquire a memory phenotype but retain ability to support potent cell killing. In cynomolgus monkeys, 4 weekly doses of 100 μg/kg were well tolerated, with prolonged PK consistent with that of an Fc-containing molecule. Taken together, MGD007 displays potent activity against colorectal cancer cells consistent with a mechanism of action endowed in its design and support further investigation of MGD007 as a potential novel therapeutic treatment for colorectal cancer. .

Redirection of Cord Blood T Cells and Natural Killer Cells for Elimination of Autologous HIV-1-Infected Target Cells Using Bispecific DART® Molecules

“…It is important to note that Thome and collaborators also identified higher frequencies of T regulatory cells in pediatric blood and tissues relative to adults (40). The CD4 + T regulatory cells may act to either limit the cytolytic activity of infant T cell responses, or may themselves serve as effector cells for CD3 DART molecule-mediated lysis of target cells as has been previously shown (55). Thus, accurate characterization of the cytolytic activity of pediatric tissue-resident T cells when recruited by HIV × CD3 DARTs will likely require in vivo testing using a biologically relevant model, such as infant rhesus macaques.…”

“…However, there are dozens of bispecific antibody-based molecules in various stages of development, and clinical testing, against multiple types of cancers (71,72). This includes several DART molecules being evaluated for potential use in treatment of leukemias and lymphomas (73,74), colorectal cancer (55), and solid tumors (75). The majority of bispecifics in development are intended to recruit T cells via an anti-CD3 arm, however NK cell recruitment by anti-CD16 targeting is also being explored (76,77).…”

Expanding the Boundaries of Biotherapeutics with Bispecific Antibodies

“…DART-Fc molecules have shown improved half-lives ranging between 70 h [ 115 ] and 105 h [ 76 ] in mice, an improvement over the regular version of DARTs with half-life values ranging from 2.4 to 3.6 h [ 73 ]. An extended half-life of ~ 6.5 days has also been observed in cynos [ 116 ]. BiTEs (bispecific T-cell engagers) are the fragments with the shortest half-life among bispecific fragments, thus they are the ones that benefit the most from half-life extending efforts.…”

Summary of a workshop on preclinical and translational safety assessment of CD3 bispecifics

“…An unbiased screen for mAbs broadly reactive against all categories of CRC was used to identify gpA33 as a target. The gpA33-specific DART V R (MGD007) is a diabody with an Fc fusion to increase half-life (Moore et al 2018). MGD007 has demonstrated in vitro cytotoxicity with multiple subsets of T-cells, including suppressive T-cell populations, and is able to induce killing of cancer stem cells.…”