Abstract C132: SGN-35T: A novel CD30-directed antibody-drug conjugate for the treatment of lymphomas
Authors: Hamblett Kevin J , Jin Steven , Yumul Roma , Chen Yufei , Kwon John , Simmons Jessica , Henderson Clark , Sun Hao , Schrum Jason P , Lim Andrea R , Bindman Noah A , Conerly Melissa , Clarke Astrid 
Published: December 2023

Abstract
Antibody-drug conjugates (ADCs) employing the vedotin drug linker are effective anti-cancer agents in multiple indications including Hodgkin lymphoma, cervical cancer, and bladder cancer. While vedotin ADCs have demonstrated efficacy for the treatment of a wide variety of solid and hematologic cancers, some side effects, including dose-limiting neutropenia, are commonly observed. To improve the tolerability while leveraging the known activity of brentuximab vedotin, an ADC approved for the treatment of advanced classical Hodgkin lymphoma and other CD30-expressing lymphomas, alternative ADC structural components are under exploration. A novel cleavable linker containing a tripeptide molecule comprised of D-leucine-alanine-glutamate (DLAE) was developed and used to generate SGN-35T, an anti-CD30 ADC with the same mAb backbone and cytotoxic monomethyl auristatin E (MMAE) payload as brentuximab vedotin. SGN-35T was investigated for both anti-tumor activity and effects on hematopoiesis using in vitro and in vivo assays. SGN-35T displayed comparable activity to brentuximab vedotin against three lymphoma cell lines in vitro, and complete or near-complete tumor growth inhibition in five lymphoma xenograft models including a CD30-heterogeneous model. SGN-35T led to cell cycle arrest at the G2/M phase leading to apoptosis, in concordance with the established mechanism of action of MMAE. Introduction of the tripeptide linker in SGN-35T maintained the induction of immunogenic cell death hallmarks observed with brentuximab vedotin and other vedotin-based ADCs. SGN-35T demonstrated reduced potency on hematopoiesis compared to brentuximab vedotin in a human bone marrow colony-forming unit assay. In cynomolgus monkey toxicity studies, administration of SGN-35T had a reduced impact to neutrophils counts at matched dose levels and a two-fold improvement in tolerability compared to brentuximab vedotin, with a highest non-severely toxic dose (HNSTD) of 6 mg/kg versus an HNSTD of 3 mg/kg for brentuximab vedotin when administered Q3Wx4. Together, these data demonstrate that SGN-35T exhibits anti-tumor activity in preclinical models and may reduce the severity of hematopoietic toxicities while retaining anti-tumor activity observed with brentuximab vedotin. A Phase 1, first-in-human study is planned to evaluate the safety and anti-tumor activity of SGN-35T in lymphoid malignancies.
Citation Format: Kevin J Hamblett, Steven Jin, Roma Yumul, Yufei Chen, John Kwon, Jessica Simmons, Clark Henderson, Hao Sun, Jason P Schrum, Andrea R Lim, Noah A Bindman, Melissa Conerly, Astrid Clarke. SGN-35T: A novel CD30-directed antibody-drug conjugate for the treatment of lymphomas [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C132.