A T-cell engaging bispecific antibody with a tumor-selective bivalent folate receptor alpha binding arm for the treatment of ovarian cancer

The use of T-cell engagers (TCEs) to treat solid tumors is challenging, and several have been limited by narrow therapeutic windows due to substantial on-target, off-tumor toxicities due to the expression of low levels of target antigens on healthy tissues. Here, we describe TNB-928B, a fully human TCE that has a bivalent binding arm for folate receptor alpha (FRα) to selectively target FRα overexpressing tumor cells while avoiding the lysis of cells with low levels of FRα expression. The bivalent design of the FRα binding arm confers tumor selectivity due to low-affinity but high-avidity binding to high FRα antigen density cells. TNB-928B induces preferential effector T-cell activation, proliferation, and selective cytotoxic activity on high FRα expressing cells while sparing low FRα expressing cells. In addition, TNB-928B induces minimal cytokine release compared to a positive control TCE containing OKT3. Moreover, TNB-928B exhibits substantial ex vivo tumor cell lysis using endogenous T-cells and robust tumor clearance in vivo, promoting T-cell infiltration and antitumor activity in mouse models of ovarian cancer. TNB-928B exhibits pharmacokinetics similar to conventional antibodies, which are projected to enable favorable administration in humans. TNB-928B is a novel TCE with enhanced safety and specificity for the treatment of ovarian cancer.

Abstract 6244: A T cell engaging bispecific antibody utilizing a bivalent tumor-selective folate receptor alpha binding arm for the treatment of ovarian cancer

The use of T cell engagers (TCEs) to treat solid tumors in humans is challenging, and several have been limited by narrow therapeutic windows due to substantial toxicity. Dose-limiting toxicities of TCEs include cytokine release syndrome (CRS) and on-target, off-tumor toxicities since many solid tumor target antigens are also expressed in healthy tissues, albeit at lower levels. While there have been improvements in the clinical management of immune-mediated toxicities such as CRS, on-target, off-tumor effects remain one of the primary challenges of using TCEs for treatment of solid tumors. Here, we describe TNB-928B, a novel fully human TCE that is bivalent for folate receptor alpha (FRα) that selectively targets FRα overexpressing tumor cells yet avoids targeting cells that express low levels of FRα found in normal human cells. Selectivity is conferred by an avidity effect of the FRα targeting arm in combination with a unique low-affinity CD3 arm and is anticipated to reduce the risk of adverse events in normal cells expressing low levels of FRα. TNB-928B induces preferential effector T cell activation, proliferation, and cytotoxic activity with minimal cytokine release, compared to a positive control containing OKT3, thereby improving the therapeutic index. Moreover, TNB-928B exhibits substantial ex vivo tumor cell lysis using endogenous T cells and is effective in vivo promoting T cell infiltration and tumor regression in mouse models of ovarian cancer. Together, these results demonstrate TNB-928B represents a novel next generation immunotherapy modality with enhanced safety and specificity for the treatment of ovarian cancer.

Citation Format: Brian C. Avanzino, Kirthana Prabhakar, Pranjali Dalvi, Sharon Hartstein, Hannes Kehm, Aarti Balasubramani, Andrew A. Boudreau, Ben Buelow, Karen Chang, Laura M. Davison, Suhasini Iyer, Vidyut Kalwit, Harbani Malik-Chaudhry, Will Pierson, Geovanni Pineda, Udaya S. Rangaswamy, Sowmya Saiganesh, Ute Schellenberger, Harshad S. Ugamraj, Roland Buelow, Jocelyn Chapman, Nathan D. Trinklein, Katherine E. Harris. A T cell engaging bispecific antibody utilizing a bivalent tumor-selective folate receptor alpha binding arm for the treatment of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6244.

A bispecific antibody agonist of the IL-2 heterodimeric receptor preferentially promotes in vivo expansion of CD8 and NK cells

The use of recombinant interleukin-2 (IL-2) as a therapeutic protein has been limited by significant toxicities despite its demonstrated ability to induce durable tumor-regression in cancer patients. The adverse events and limited efficacy of IL-2 treatment are due to the preferential binding of IL-2 to cells that express the high-affinity, trimeric receptor, IL-2Rαβγ such as endothelial cells and T-regulatory cells, respectively. Here, we describe a novel bispecific heavy-chain only antibody which binds to and activates signaling through the heterodimeric IL-2Rβγ receptor complex that is expressed on resting T-cells and NK cells. By avoiding binding to IL-2Rα, this molecule circumvents the preferential T-reg activation of native IL-2, while maintaining the robust stimulatory effects on T-cells and NK-cells in vitro. In vivo studies in both mice and cynomolgus monkeys confirm the molecule's in vivo biological activity, extended pharmacodynamics due to the Fc portion of the molecule, and enhanced safety profile. Together, these results demonstrate that the bispecific antibody is a safe and effective IL-2R agonist that harnesses the benefits of the IL-2 signaling pathway as a potential anti-cancer therapy.

TNB-486 induces potent tumor cell cytotoxicity coupled with low cytokine release in preclinical models of B-NHL

The therapeutic potential of targeting CD19 in B cell malignancies has garnered attention in the past decade, resulting in the introduction of novel immunotherapy agents. Encouraging clinical data have been reported for T cell-based targeting agents, such as anti-CD19/CD3 bispecific T-cell engager blinatumomab and chimeric antigen receptor (CAR)-T therapies, for acute lymphoblastic leukemia and B cell non-Hodgkin lymphoma (B-NHL). However, clinical use of both blinatumomab and CAR-T therapies has been limited due to unfavorable pharmacokinetics (PK), significant toxicity associated with cytokine release syndrome and neurotoxicity, and manufacturing challenges. We present here a fully human CD19xCD3 bispecific antibody (TNB-486) for the treatment of B-NHL that could address the limitations of the current approved treatments. In the presence of CD19+ target cells and T cells, TNB-486 induces tumor cell lysis with minimal cytokine release, when compared to a positive control. In vivo, TNB-486 clears CD19+ tumor cells in immunocompromised mice in the presence of human peripheral blood mononuclear cells in multiple models. Additionally, the PK of TNB-486 in mice or cynomolgus monkeys is similar to conventional antibodies. This new T cell engaging bispecific antibody targeting CD19 represents a novel therapeutic that induces potent T cell-mediated tumor-cell cytotoxicity uncoupled from high levels of cytokine release, making it an attractive candidate for B-NHL therapy.