Abstract P1-11-12: Soluble TNFα blockade enhances trastuzumab deruxtecan antitumor effect in HER2-positive breast cancer model
Authors: Bruni Sofia , Mauro Florencia , Proietti Cecilia , Cordo-Russo Rosalia , Florencia Mercogliano María , Schillaci Roxana 
Published: March 2023

Abstract
Background. Clinical trials have demonstrated that trastuzumab deruxtecan (T-DXd) provides a durable responses for patients with HER2-positive and HER2 low metastatic breast cancer (BC). With T-DXd treatment, approximately 50% of patients with HER2+ metastatic BC were still alive and progression-free at 24 months (DESTINY-Breast03). We previously shown that mucin 4 (MUC4) expression is an independent predictor of poor response to trastuzumab in HER2-positive BC patients. We also showed that MUC4 is upregulated by soluble TNFα (sTNFα) secreted by the tumor, which confers primary trastuzumab resistance since it hides trastuzumab epitope on the HER2 molecule, reducing its binding and diminishing its therapeutic effects. In preclinical models of de novo trastuzumab-resistant tumors, we proved that administration of the sTNFα blocking agent INB03 (DN) together with trastuzumab inhibited tumor growth and induced an innate immune response in the tumor microenvironment (TME). DN is a dominant-negative inhibitor of sTNFα that is not immunosuppressive because it does not affect transmembrane TNFα. Our goal is to study whether neutralizing sTNFα can improve T-DXd effects in a multiple HER2-targeted therapy-resistant model. Methods JIMT-1 is a HER2-positive BC cell line resistant to trastuzumab, pertuzumab and lapatinib, which expresses MUC4. JIMT-1 tumor-bearing nude mice were treated with (1) IgG 5 mg/kg, (2) T-DXd 5 mg/kg, (3) T-DXd 2.5 mg/kg, (4) T-DXd 1.25 mg/kg, (5) DN 10 mg/kg, (6) T-DXd 5 mg/kg +DN, (7) T-DXd 2.5 mg/kg +DN and (8) T-DXd 1.25 mg/kg +DN. T-DXd and IgG were administered i.v. on days 0, 7 and 14. DN was administered i.p. twice a week for 3 weeks. Tumor growth was monitored regularly. Tumor-infiltrating macrophages, NK cells and myeloid-derived suppressor cells (MDSCs) were evaluated by immunofluorescence and flow cytometry. Results The dose-response curve of T-DXd exhibited tumor growth inhibitions of 83% (5 mg/kg), 61% (2.5 mg/kg) and 37% (1.25 mg/kg) vs IgG-treated tumors. DN alone had no antitumor effect. Combination of T-DXd with DN resulted in a reinforced antitumor effect, as the tumor growth inhibition escalated to 98% (T-DXd 5 mg/kg+ DN), 81% (T-DXd 2.5 mg/kg+DN) and 73% (T-DXd 1.25 mg/kg+DN). Moreover, we observed that addition of DN to T-DXd 1.25 and 5 mg/kg enhances the infiltration of resident macrophages (p &lt; 0.05 and p&lt;0.01, respectively) and promotes polarization to the M1-like phenotype (p &lt; 0.05 and p&lt;0.001, respectively). While T-DXd 2.5 and 5 mg/kg alone achieved a decrease in M2-like macrophages (p &lt; 0.05), combination of T-DXd 1.25mg/kg+DN impaired M2-like polarization at similar levels of that observed with 2.5 and 5 mg/kg T-DXd (p &lt; 0.05). Notably, the M1/M2 ratio escalated from 10.9% to 51.5% when DN was added to the lowest T-DXd dose (p &lt; 0.01). In addition, T-DXd 2.5 and 5 mg/kg induce an increase in the proportion of NK cells in TME (p &lt; 0.001 and p&lt;0.05, respectively), which T-DXd 1.25 mg/kg+ DN treatment mimicked (p &lt; 0.05). Although an increase in NK cell activation was observed with 1.25 and 2.5 mg/kg treatments (p &lt; 0.05 and p&lt;0.001, respectively), adding DN did not further improved this effect. Only the highest dose of T-DXd in combination with DN was able to increase NK cell degranulation (p &lt; 0.05), compared to T-DXd alone. Finally, the percentage of MDSCs population decreases with the addition of DN to the T-DXd 2.5 and 5 mg/kg. Conclusions Our results suggest that sTNFα blockade is able to enhance T-DXd effect in a multiple HER2-targeted therapy resistant model. Notably, the administration of T-DXd 1.25 mg/kg+DN achieved a similar antitumor effect to T-DXd 5 mg/kg alone and also transforms the TME to an antitumor one with a reinforced immune response. This finding highlights that sTNFα and MUC4 expression are important variables in the response to T-DXd. Neutralization of sTNFα may open new therapeutic strategies for treatment of patients who present with MUC4 expression or have progression on T-DXd therapy.
Citation Format: Sofia Bruni, Florencia Mauro, Cecilia Proietti, Rosalia Cordo-Russo, Mercogliano María Florencia, Roxana Schillaci. Soluble TNFα blockade enhances trastuzumab deruxtecan antitumor effect in HER2-positive breast cancer model [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-11-12.