Unique Mechanism and Targeted Therapy Strategy of ASP2138

Astellas Pharma and Xencor are jointly developing ASP2138, a bispecific T-cell engager (BiTE) antibody that simultaneously binds to Claudin 18.2 (CLDN18.2) and the CD3 protein on T cells. This drug employs an innovative mechanism by physically bringing together CLDN18.2-expressing cancer cells and T cells, inducing the T cells to directly kill the cancer cells. It utilizes Xencor's proprietary XmAb platform technology, featuring a 2+1 structure (CLDN18.2 di-binding and CD3 mono-binding), designed to maximize targeting of cancer cells while minimizing side effects caused by excessive immune responses. This approach can elicit a faster and more potent immune response compared to monoclonal antibodies, potentially revolutionizing pancreatic cancer treatment.

Introduction of Neoadjuvant/Adjuvant Design

The initiated Phase 1b clinical trial (NCT07024615) is an innovative clinical design that tests a neoadjuvant/adjuvant treatment protocol in patients with resectable pancreatic ductal adenocarcinoma (PDAC). Patients will receive ASP2138 via subcutaneous injection for two weeks before surgery, aiming to reduce tumor size and inhibit micrometastasis. After surgery, they will receive a researcher-selected standard chemotherapy regimen as adjuvant therapy, employing a multifaceted strategy to eliminate any remaining microscopic residual cancer cells. By intervening early and actively, the trial aims to improve resectability, reduce the risk of recurrence, and significantly improve survival rates.

Combination with Standard Chemotherapy and Assessment of Safety/Tolerability

In the adjuvant phase after surgery, patients will receive either mFOLFIRINOX or gemcitabine-based standard chemotherapy in combination with ASP2138, depending on their condition. The primary objective of the Phase 1b trial is to evaluate the toxicity induced by this combination therapy and to determine the maximum tolerated dose (MTD) and safety in the context of pancreatic cancer treatment, where elderly patients are common. The intention is to proactively control potential adverse reactions that may arise from combining potent chemotherapy with immunotherapy, thereby increasing the likelihood of clinical success. Astellas plans to identify the optimal dosage that can be safely administered to patients in the early, resectable stage.

Expansion of Astellas' CLDN18.2 Portfolio and Synergy

Astellas has already demonstrated market leadership by developing Vyloy (zolbetuximab-clzb), its first CLDN18.2-targeting monoclonal antibody, which received FDA approval on October 18, 2024. The initiation of this Phase 1b trial for ASP2138 reflects Astellas' commitment to expanding its portfolio with a more advanced modality, bispecific antibodies, and extending its reach into the pancreatic cancer area, which has significant unmet needs, building upon the success of Vyloy. This is more than just securing a single treatment; it is about creating a pipeline that can provide the optimal targeted cancer therapy lineup based on the characteristics of the cancer and establishing a presence in the related diagnostics market. The CLDN18.2 biomarker validation and clinical experience accumulated through the already approved Vyloy are expected to have a positive synergistic effect on the accelerated development of ASP2138.

Background of the Technology Licensing Agreement and Significance of the Partnership

The development of ASP2138 is based on a joint research and license agreement for oncology bispecific antibodies signed between Astellas and Xencor in April 2019. Under the terms of the agreement, Xencor received an upfront payment of $15 million and is eligible for milestone payments of up to $240 million and royalties ranging from the high single digits to the low double digits, based on future clinical progress, approval, and commercial performance. The entry of this Phase 1b trial marks an important milestone, demonstrating that the partnership between the two companies has moved beyond the research stage and is entering a tangible commercialization path. The combination of Xencor's XmAb bispecific antibody engineering technology and Astellas' global clinical and commercial capabilities will enable them to become a leading player in the next-generation immuno-oncology market.