No.24-48

July 1, 2024
Eisai Co., Ltd.

EISAI ANNOUNCES MOVE TO SOLO DEVELOPMENT AND COMMERCIALIZATIONOF FARLETUZUMAB ECTERIBULIN (FZEC) ANTIBODY DRUG CONJUGATE (ADC)
Strategic collaboration with Bristol Myers Squibb ended
Eisai Co., Ltd. (Headquarters: Tokyo, CEO: Haruo Naito, “Eisai”) announced today that it has agreed toend its global strategic collaboration with Bristol Myers Squibb for the co-development andco-commercialization of farletuzumab ecteribulin (FZEC), formerly known as MORAb-202, a folate receptoralpha (FRα)-targeting antibody drug conjugate (ADC) due to ongoing portfolio prioritization efforts within
Bristol Myers Squibb. Based on the agreement, Eisai now owns all rights to FZEC and will solely conduct
the global development and commercialization of the agent. Eisai will accelerate the development of theagent as a high priority with the hope to deliver it to patients as early as possible. Eisai plans to refund apart of the unused portion of the $200 million payment it received towards research and development
expenses from Bristol Myers Squibb under the collaboration agreement and record the remaining as otherincome.
FZEC is Eisai’s first ADC and is composed of Eisai’s in-house developed farletuzumab, a humanized IgG1
monoclonal antibody that binds to the FRα, and Eisai’s in-house developed anticancer agent eribulin, using
an enzymatically cleavable linker. Currently, three clinical studies are ongoing: Eisai’s Phase 1/2 study forsolid tumors (NCT04300556), and Bristol Myers Squibb’s Phase 2 studies for ovarian, peritoneal andfallopian tube cancers (NCT05613088) and non-small cell lung cancer (NCT05577715).
Eisai positions oncology as a key franchise area and aims to contribute toward the cure of cancers byexploring the depths of human biology. FZEC development for refractory cancers is a testament of ourdedication to addressing the unmet medical needs of patients with cancer. Eisai will make continuous
efforts to increase the benefits provided to patients with cancer and their families.

Media Inquiries:
Public Relations Department,
Eisai Co., Ltd.
+81-(0)3-3817-5120

[Notes to editors]
1.

Farletuzumab ecteribulin (FZEC, formerly known as MORAb-202)

FZEC is Eisai’s first antibody drug conjugate (ADC) and that is composed of Eisai’s in-house developed farletuzumab, ahumanized IgG1 monoclonal antibody that binds to the folate receptor alpha (FRα), and Eisai’s in-house developed
anticancer agent eribulin, using an enzymatically cleavable linker. After FZEC enters the target FRα-positive cancer cells, itis thought that the linker is enzymatically cleaved, releasing eribulin from the antibody leading to its antitumor activity. Whenthe anticancer agent and antibody components of an ADC are separated inside a targeted antigen-positive cancer cell, it istheorized that the released anticancer agent also has a bystander effect on neighboring antigen-negative cancer cells andthe component cells of the tumor microenvironment. In pre-clinical studies, FZEC demonstrated a bystander effect*, withantitumor activity on the FRα-negative cancer cells surrounding the FRα-positive cancer cells.
The payload eribulin was the first in the halichondrin class of microtubule dynamics inhibitor. Structurally, eribulin is a
simplified and synthetically produced version of halichondrin B, a natural product isolated from the marine sponge
Halichondria okadai, and functions by inhibiting the growth phase of microtubule dynamics which prevents cell division.
Eribulin has been approved in countries including Japan, the United States, China, in Europe and in Asia for use in thetreatment of advanced breast cancer and liposarcoma (soft tissue sarcoma in Japan).
*Bystander effect: When the anticancer agent and antibody parts of an ADC are separated inside a targeted antigen-positivecancer cell, the released anticancer agent also affects neighboring antigen-negative cancer cells and the component cellsof the cancer microenvironment.

2