Preclinical Activity of Datopotamab Deruxtecan, an Antibody-Drug Conjugate Targeting Trophoblast Cell-Surface Antigen 2, in Uterine Serous Carcinoma

Abstract

Uterine serous carcinoma (USC) is a rare subset of endometrial cancer with a poor prognosis and high recurrence rate. Datopotamab deruxtecan (Dato-DXd) is a novel antibody-drug conjugate (ADC). The objective of this study was to evaluate the preclinical activity of Dato-DXd in USC in vitro against primary USC cell lines with various trophoblast cell-surface antigen 2 (TROP2) expression and in vivo in TROP2-overexpressing cell line-derived mice xenografts. USC primary tumor cell lines were treated with Dato-DXd and a control ADC (CTL ADC) to evaluate cell viability following exposure. Antibody-dependent cell-mediated cytotoxicity against TROP2-overexpressing and -nonexpressing cell lines was evaluated using a 4-hour chromium release assay. USC xenografts in mice were treated with Dato-DXd, CTL ADC, datopotamab, and vehicle to assess the in vivo effects via retro-orbital Dato-DXd administration. We found USC cell lines with TROP2 overexpression to be significantly more sensitive to killing induced by Dato-DXd compared with CTL ADC in vitro (e.g., IC50: 0.11 µmol/L vs. 30.07 µmol/L, P = 0.0074 and 0.11 µmol/L vs. 48.95 µmol/L, P = 0.0127, respectively). Dato-DXd induced antibody-dependent cell-mediated cytotoxicity in the presence of peripheral blood lymphocytes from healthy donors. TROP2-nonexpressing cell lines demonstrated minimal killing by Dato-DXd; however, when admixed with TROP2-overexpressing cells, a significant bystander effect was appreciated. In vivo, mice xenografts overexpressing TROP2 treated with Dato-DXd demonstrated tumor growth suppression and longer overall survival compared with CTL ADC-treated xenografts. These data demonstrate Dato-DXd to be highly active against TROP2-overexpressing USC in vitro and in vivo. Our preclinical activity results warrant future clinical trials for patients with advanced or recurrent USC.

Significance: Targeted treatment of USC using the biomarker TROP2 represents a significant opportunity for further treatment options for patients already resistant to other lines of treatment. In this study, we present data showing preclinical evidence of effectiveness of this biomarker-targeted therapy in USC.

Figure 1

IC₅₀ value dose–response curves of Dato-DXd and CTL ADC in USC cell lines with variable TROP2 expression. A, TROP2 3+ ARK2 USC cell line: the mean IC₅₀ value of Dato-DXd was 0.11 μg/mL vs. 30.07 μg/mL for CTL ADC (P = 0.0074). B, TROP2 3+ ARK20 USC cell line: the mean IC₅₀ value of Dato-DXd was 0.11 μg/mL vs. 48.95 μg/mL for CTL ADC (P = 0.0127). C, TROP2 1+ ARK7 USC cell line: the mean IC₅₀ value of Dato-DXd was 80.38 μg/mL vs. 61.79 μg/mL for CTL ADC. D, TROP2 ARK1 USC cell line: the mean IC₅₀ value was 18.49 μg/mL vs. 17.12 μg/mL for CTL ADC (P = 0.65).

Figure 2

Bystander antitumor effect of TROP2-nonexpressing USC cells (ARK-4) when cocultured with TROP2 3+ USC ARK2 cell line treated with 0.5 μg/mL of Dato-DXd vs. CTL ADC. Dato-DXd had little effect on ARK-4 when they were cultured alone (83% lives cells); however, when ARK-4 was cocultured with TROP2 3+ ARK2, Dato-DXd induced significantly more ARK-4 cell killing (64.8% live cells, P = 0.0231). CTL ADC did not have significant cell killing with coculture (95% live cells).

Figure 3

ADCC results of Dato-DXd, datopotamab, rituximab, and CTL ADC in representative (A) ARK2 USC TROP2 3+, (B) ARK20 USC TROP2 3+, and (C) ARK1 USC TROP2-nonexpressing cell lines.

Figure 4

DNA breakage induced from cell internalization of DXd represented by the phosphorylation of H2AX. Greater staining at doses of 5 μg/mL seen with Dato-DXd treatment compared with CTL ADC.

Figure 5

Antitumor activity in mice inoculated with TROP2 3+ USC ARK2 xenograft tumor models (CDXs). A, CDX tumor volumes after treatment with Dato-DXd, datopotamab, CTL ADC, and vehicle control (PBS). Dato-DXd demonstrates significant tumor growth inhibition compared with datopotamab, CTL ADC, and vehicle CTL. B, OS in CDX after a single retro-orbital treatment with Dato-DXd compared with datopotamab, CTL ADC, and vehicle. OS was significantly prolonged among Dato-DXd–treated groups compared with other treatment groups.