Zymeworks with updated single agent data for HER2-targeted bispecific antibody ZW25 at ESMO

Zymerowks’ data for HER2-targeted biospecific antibody ZW25, which will be presented at ESMO, support the Initiation of a Registration-Enabling Phase 2 Trial of the ZW25 in second-line HER2-expressing biliary tract cancers.

BARCELONA, Spain–(BUSINESS WIRE)–Zymeworks Inc. (NYSE/TSX: ZYME), a clinical-stage biopharmaceutical company developing multifunctional therapeutics, today announced updated data from the ongoing multi-center Phase 1 clinical trial evaluating ZW25 in patients with HER2‑expressing solid tumors, including biliary tract cancer (BTC), colorectal cancer (CRC), gynecological cancers, and gastroesophageal adenocarcinoma (GEA), in a poster discussion presentation at the ESMO 2019 Congress, taking place September 27 – October 1 in Barcelona, Spain.

“The data presented today at ESMO confirm previous findings that ZW25 monotherapy can provide durable disease control in patients with a variety of HER2-expressing solid tumors that have progressed following standard of care therapies, including HER2-targeted agents,” said Diana Hausman, M.D., Chief Medical Officer at Zymeworks. “Notably, the single agent objective response rate in biliary tract cancer is highly encouraging given the poor prognosis and limited treatment options for these patients. We are working closely with regulatory agencies to initiate a registration-enabling Phase 2 trial in second-line HER2‑expressing biliary tract cancer with the goal of bringing ZW25 to patients as quickly as possible.”

Based on the data from the ongoing Phase 1 study, Zymeworks has initiated a broad clinical development program for ZW25 in multiple HER2-expressing cancers. In addition to the Phase 2 BTC trial announced today, Zymeworks is continuing to evaluate ZW25 as a potential treatment for patients with other HER2-expressing cancers, including CRC and gynecological cancers (Phase 1; NCT02892123). For patients with HER2-expressing GEA, ZW25 is being developed as a first-line treatment in combination with standard of care chemotherapy (Phase 2; NCT03929666). Zymeworks also plans to initiate a Phase 2 study of ZW25 in combination with a CDK4/6 inhibitor and hormone therapy in third-line HER2-expressing, HR-positive breast cancer.

ZW25 Clinical Results Presented Today

The Safety, Efficacy and Biomarker Results of the HER2-Targeted Bispecific Antibody ZW25 in HER2-Expressing Solid Tumors (Abstract# 3575, Poster Discussion on Saturday, September 28 at 4:30 pm CEST)

Findings from this ongoing Phase 1 study of ZW25 in patients with HER2-expressing solid tumors were last presented at the 2018 EORTC-NCI-AACR Symposium. The updated results were presented today by Dr. Funda Meric-Bernstram, M.D., Clinical Investigator and Chair of the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center.

Data were reported from 58 patients diagnosed with HER2-expressing solid tumors other than breast cancer who received ZW25 at the recommended dose of either 10 mg/kg weekly or 20 mg/kg every other week. Patients had a median age of 61 years and received a median of four prior therapies. Thirty-two (55%) patients received prior HER2‑targeted therapies including 87% of GEA patients. Of all patients, 23 were diagnosed with GEA, 13 with CRC, nine with BTC, and 13 with other HER2‑expressing cancers, including endometrial, ovarian, pancreatic, and salivary gland.

At the time of data cut-off, 46 of 58 patients were response evaluable. Overall, the majority of patients experienced a decrease in their target lesions with a disease control rate of 72%, comprising 16 (35%) patients with partial responses and 17 (37%) with stable disease. The objective response rate in the six evaluable biliary tract cancer patients was 67%, with the majority of patients experiencing disease control greater than six months. In the 11 CRC and 19 GEA patients, the objective response rates were 36% and 32%, respectively. The overall median progression-free survival was 5.2 months, with 27 (47%) of the 58 total patients still on study at the time of data cut-off.

Among all patients, ZW25 was well tolerated as an outpatient therapy. The most common adverse events were diarrhea, infusion-related reaction, and nausea. All treatment-related adverse events occurring in 10% or more of patients were Grade 1 or 2.

About the Phase 1 Clinical Trial

Zymeworks’ Phase 1 study has three parts. From part one of the study (the dose-escalation phase), the recommended single-agent dose was determined to be 20 mg/kg once every two weeks or 10 mg/kg weekly. In the second part of the study (the cohort expansion phase), additional patients are being enrolled to further assess ZW25’s single-agent tolerability and anti-tumor activity against a variety of cancer types in different settings. The third part of the study (the combination phase) is underway and evaluating ZW25 in combination with selected chemotherapy agents in gastroesophageal and breast cancer patients with HER2 high or lower HER2 expression levels.

About ZW25

ZW25 is being evaluated in Phase 1 and Phase 2 clinical trials across North America and South Korea. It is a bispecific antibody, based on Zymeworks’ Azymetric™ platform, that can simultaneously bind two non-overlapping epitopes of HER2, known as biparatopic binding. This unique design results in multiple mechanisms of action including dual HER2 signal blockade, increased binding and removal of HER2 protein from the cell surface, and potent effector function leading to encouraging anti-tumor activity in patients. Zymeworks is developing ZW25 as a HER2-targeted treatment option for patients with any solid tumor that expresses HER2. The FDA has granted Fast Track designation to ZW25 for first-line gastroesophageal adenocarcinoma in combination with standard of care chemotherapy and Orphan Drug designation to ZW25 for the treatment of both gastric and ovarian cancers.