On December 12, 2019 Zhejiang Medicine, NovoCodex and Ambrx reported positive interim topline data from the ongoing "111" trial (CTR20171162) evaluating ARX788, a novel anti-HER2 ADC, in heavily pretreated patients with metastatic HER2 positive breast cancer (Press release, Zhejiang Medicine, DEC 12, 2019, View Source [SID1234552312]). All patients enrolled had failed prior therapy with trastuzumab and 47% had failed therapy with trastuzumab and lapatinib.
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ARX788 was well tolerated at all dose levels with just two ≥ Grade 3 drug related reversible adverse events observed amongst 51 enrolled patients. ARX788 showed an excellent safety profile with dose escalation continuing. No DLT or MTD was observed as of the November 20, 2019 cut-off date.
Response rates correlated with increased dose levels. As of the cut-off date, the highest dose tested was 1.5mg/kg every three weeks. This cohort, which continues dosing and remains under observation, had already achieved a 63% overall response rate. Prior cohorts at 0.88, 1.1 and 1.3 mg/kg demonstrated overall response rates of 14%, 36% and 56% respectively. Further, the substantial increases in efficacy observed at higher doses was achieved with only mild increases in toxicity.
These data originate from the Fudan University Shanghai Cancer Center in China and are part of a broader global ARX788 development program (NCT03255070 and CTR20171162) that includes clinical sites in China, USA and Australia.
The 42nd Annual San Antonio Breast Cancer Symposium Poster is available at www.ambrx.com
Zhejiang Medicine licensed the commercial rights to ARX788 in China in 2013. The promising clinical data for ARX788 serves as a solid foundation to the second and more recent collaboration. Earlier this year, Ambrx and Zhejiang Medicine (via its subsidiary NovoCodex) entered into their second collaboration to develop and commercialize ARX305 in China. ARX305 is an anti-CD70 Antibody Drug Conjugate for the potential treatment of Renal Cell Carcinoma, Multiple Myeloma, and other solid tumors.
About HER2-Positive Breast Cancer
Almost 300,000 new cases of HER2 positive breast cancer may be diagnosed in 2020 in the US alone (approximately 15-20% of breast cancers are HER2 positive). HER2 positive breast cancer tends to be aggressive and more likely to recur than HER2 negative. There are currently no approved therapies demonstrating progression-free survival or overall survival benefit for the treatment of patients with HER2 positive metastatic breast cancer after progression on T-DM1 (which is not approved in China).