Molecular Templates Announces FDA Acceptance of IND Application for MT-5111, An Engineered Toxin Body Targeting HER2
This Phase I study is an open-label, dose escalation and expansion study of MT-5111 given as monotherapy in subjects with HER2-positive solid tumors. The primary objective of the trial is to evaluate the safety and tolerability of MT-5111 and determine the recommended Phase II dose in subjects with advanced HER2-positive solid tumors.
“We are excited to be advancing MT-5111, which utilizes our proprietary de-immunized toxin scaffold, into the clinic for the treatment of patients with HER2-positive cancers. HER2 is a well validated target that is central to disease and when existing HER2-targeting therapies fail, the target persists, suggesting that a HER2-targeted therapy with a new mechanism of action has good potential to provide benefit to patients,” said
MT-5111 is an ETB consisting of a single chain variable fragment (scFv) with affinity for HER2, fused to the enzymatically active de-immunized Shiga-like toxin-A subunit (SLTA). MT-5111 specifically binds and kills HER2 expressing cells in a manner consistent with SLTA mediated cellular cytotoxicity. MT-5111 has been specifically designed to avoid competition with and to overcome the primary mechanisms of tumor resistance to current HER2 targeted therapies. To accomplish this, first, MT-5111 binds a HER2 domain that is distinct from the trastuzumab and pertuzumab binding sites, which results in MT-5111 HER2-mediated binding and cell kill even in the presence of these monoclonal antibodies. As such, MT-5111 may have the potential to be combined with other HER2 targeted therapies. Second, SLTA is a large molecule protein and is not a substrate of drug efflux transporters such as MDR1 which has been demonstrated to be one of the primary mechanisms of resistance to the antibody drug conjugate, T-DM1. Third, MT-5111 mediated ribosomal inhibition and cell death take place intracellularly so changes in the tumor microenvironment which inhibit immune-mediated mechanisms such as antibody-dependent cell-mediated cytotoxicity (ADCC) are not expected to inhibit MT-5111 activity. Finally, mutations to the HER2 kinase domain that can induce constitutive downstream signaling to drive tumor proliferation are not expected to interfere with MT-5111 activity, given that its mechanism of action is not dependent upon kinase domain binding and MT-5111 works directly on ribosomes to mediate ribosomal inhibition and cell death. Based on these mechanisms, MT-5111 represents a novel HER2 targeted therapy which could provide benefit in subjects with HER2-positive cancers and potentially overcome mechanisms of tumor resistance to existing HER2 targeted therapies.
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Source: Molecular Templates, Inc.