On November 22, 2019 Zymeworks Inc. (NYSE: ZYME), a clinical-stage biopharmaceutical company developing multifunctional therapeutics, reported updated Phase 1 data for single agent ZW25 in heavily pretreated patients with HER2‑expressing solid tumors in a mini oral presentation by Dr. Do-Youn Oh, study investigator and Professor at Seoul National University, at the ESMO (Free ESMO Whitepaper) Asia 2019 Congress, taking place November 22 – 24 in Singapore (Press release, Zymeworks, NOV 22, 2019, View Source [SID1234551595]). Zymeworks and its collaborator BeiGene, Ltd. plan to advance ZW25 into potentially registration-enabling global studies in HER2-expressing biliary tract cancer (BTC) and gastroesophageal adenocarcinoma (GEA), based on these durable and consistent clinical data.

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"The promising ZW25 data at ESMO (Free ESMO Whitepaper) Asia further build momentum for the expanding footprint of our ZW25 clinical development program with BeiGene," said Ali Tehrani, Ph.D., President and CEO of Zymeworks. "Cancer is a global fight, and this strong collaboration helps us to rapidly execute on upcoming late-stage studies for people with HER2-expressing cancers worldwide."

"The encouraging clinical data on ZW25 supports further evaluation of this bispecific antibody in HER2-expressing solid tumors," said John V. Oyler, Co-Founder, CEO, and Chairman of BeiGene. "We’re enthusiastic about the meaningful progress of ZW25 since we established the collaboration with Zymeworks one year ago and look forward to leveraging our unique strengths and expertise to advance ZW25 clinical development globally."

The updated single agent results of the ongoing Phase 1 trial of ZW25 in patients with HER2‑expressing solid tumors include additional safety and anti-tumor activity data from those presented at the ESMO (Free ESMO Whitepaper) 2019 Congress.

ZW25 Clinical Results Presented Today

Safety, Anti-Tumor Activity, and Biomarker Results of the HER2-Targeted Bispecific Antibody ZW25 in HER2-Expressing Solid Tumors (Presentation# 61O, Mini Oral on Friday, November 22 at 3:30 pm SGT)

Data were reported from 69 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. Overall, patients received a median of three prior systemic therapies. Those with BTC, GEA, and colorectal cancer (CRC) received a median of 4.5, 3, and 5.5 prior systemic therapies, respectively. Forty-one (59%) patients received prior HER2‑targeted therapies, including 93% of GEA patients. Eleven patients were diagnosed with BTC, 28 with GEA, 14 with CRC, and 16 with other HER2‑expressing cancers, including endometrial, ovarian, pancreatic, and salivary gland.

Fifty-seven of 69 patients were response evaluable at the time of data cut-off. Overall, the disease control rate (DCR) was 70%, comprising 25 (44%) partial responses and 15 (26%) with stable disease, and 18 (32%) patients experienced disease control for greater than six months. In the nine evaluable biliary tract cancer patients, the DCR was 78%, and the objective response rate (ORR) was 67%. In the 13 CRC and 23 GEA patients, ORRs were 46% and 39%, respectively. Notably, confirmed responses were seen across additional tumor types, including a 100% decrease in target lesions in a patient with pancreatic cancer. The overall median progression-free survival was 5.5 months and is still evolving.

Among all patients, ZW25 was well tolerated as an outpatient therapy. The most common treatment-related adverse events (TRAE) were diarrhea (43%), infusion-related reaction (26%), and nausea (13%). All TRAEs 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. More information about ZW25 clinical trials can be found at clinicaltrials.gov.

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.