Abstract P2-13-09: An investigational next generation ADC (DAN-311) is highly effective in HER2-low breast cancer models
Authors: Wright Ashley P , Wyatt Emily A , Lamm Robert J , Blumenfeld Carl M , Bradley Jodi D , Shrikhande Gayatri , Hagerty Timothy 
Published: March 2022

Background: Nanoparticles (NPs) have been developed to enhance the pharmacokinetic (PK) and biodistribution characteristics of molecules. Many early NPs, including liposomes, dendrimers, and polymeric micelles, were limited in their ability to access target tissue and lacked uniform release rates. A promising nanoparticle therapeutic has been developed utilizing biocompatible polymer chemistry. By covalently attaching chemotherapy to the polymer through linker strategies that allow for modulation of release and PK, polymeric nanoparticles provide advantages over encapsulation nanoparticle strategies. Additionally, a targeting moiety can be added to make a next-generation ADC with the drug-to-antibody-ratio (DAR) well controlled and significantly greater (e.g. DAR=60) compared to traditional ADCs. DAN-311 is a Next-Generation Antibody Drug Conjugate (NG-ADC) with a HER2-targeting agent (trastuzumab) conjugated to a therapeutic nanoparticle with camptothecin (CPT), a topoisomerase I inhibitor. The advantages that DAN-311 offers to the 50% of patients with breast cancer have tumors with low HER2 expression is two-fold: 1) the larger DAR can lead to an enhanced bystander effect where the chemotherapy is effective against the targeted cells and also the neighboring cells, and 2) the nanoparticle is also active against HER2 non-expressing cells through the enhanced permeability and retention (EPR) effect. Here, we present the control and consistency of key DAN-311 NP characteristics that allow for efficient and large scale-manufacture, including particle size, chemotherapy load (DAR), and payload release rate. We also report the enhanced efficacy of DAN-311 in a HER2-low breast cancer (JIMT-1) xenograft mouse model. Methods: Release of CPT from nanoparticles across range of combined properties was evaluated by HPLC in pH 5.5 PBS (endosomal pH), pH 7.4 PBS (physiologic pH), mouse plasma, and human plasma. HER2-low breast cancer tumor cells (JIMT-1) were implanted into female CB.17 SCID mice. Mice were randomized to vehicle or treatment arms until tumors reached 2000 mm3 or day 46. The groups evaluated included trastuzumab, the non-targeted core nanoparticle of DAN-311, and DAN-311. Results: NPs across a wide range in polymer molecular weight and drug loading demonstrate striking consistency in particle size (ca. 30-45 nm), DAR (ca. 60-70 CPT molecules), and demonstrate linear release kinetics in various physiologically-relevant media. DAN-311 exhibited significantly greater tumor growth inhibition compared to vehicle, core particle, and trastuzumab. The non-targeted core particle also demonstrated significant tumor growth inhibition compared to vehicle and trastuzumab, which was sustained for at least 3 weeks after the final dose.

Core particle = same DAN-311 nanoparticle without HER2 targeting. Conclusions: DAN-311, a Next-Generation ADC with a HER2-targeting agent (trastuzumab) on a polymeric nanoparticle conjugated with CPT demonstrated a significant ability to inhibit tumor growth in a HER2-low xenograft mouse model. Importantly, the nanoparticle targeted delivery of CPT for cells with low expression of receptors is highly efficient in cell killing and the large DAR provides greater bystander cell killing capability; and non-HER2-expressing lesions or regions of tumors will additionally be treated by the nanoparticle through EPR. DAN-311 is advancing to clinical study to treat HER2-low metastatic breast cancer patients.

TreatmentDose (mg/kg)Day 22 TGI (%)Day 46 TGI (%)Trastuzumab10 mg/kg Tras629Core particle1 mg/kg CPT3955DAN-31110 mg/kg Tras/1 mg/kg CPT8777

Citation Format: Ashley P Wright, Emily A Wyatt, Robert J Lamm, Carl M Blumenfeld, Jodi D Bradley, Gayatri Shrikhande, Timothy Hagerty. An investigational next generation ADC (DAN-311) is highly effective in HER2-low breast cancer models [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-09.