Ambrx Biopharma Highlights Preclinical Data From Studies in Kidney, Prostate Cancer

Ambrx Biopharma Inc (NASDAQ:AMAM) announced new preclinical data from ARX517 and ARX305 studies at the 2023 American Association for Cancer Research (AACR) Annual Meeting.
The stability of ARX517 was demonstrated in a non-human primate (monkey) study.
Pharmacokinetic measurements confirm the high stability of ARX517 in circulation with an extended half-life of 11 or 15 days.
The main metabolite of ARX517 cytotoxic linker payload, pAF-AS269, was barely measurable (0.2 ng/mL) in the serum in a repeat dosing study.
At the highest non-severely toxic dose (HNSTD), ARX517 serum exposure was greater than ARX517 exposure at a pharmacologically active dose in mice, showing a clear therapeutic index.
In an enzalutamide-sensitive mouse model of prostate cancer, ARX517 demonstrated anti-tumor activity. Further, the combination of 3 mg/kg ARX517 plus 10 mg/kg enzalutamide delivered an 86% reduction in tumor size.
In an enzalutamide-resistant prostate cancer model, three weekly doses of 3 mg/kg of ARX517 significantly inhibited tumor growth by 79% in a dose-dependent manner.
Ambrx is investigating ARX517 in the APEX-01 Phase 1 study in adult subjects and enrolling patients with advanced prostate cancer whose tumors have progressed following at least two FDA-approved treatments.
In a renal cell carcinoma (RCC, 786-OS3) xenograph model, ARX305 dose-dependently inhibited tumor growth and outperformed sunitinib.
In another RCC (Caki-1) xenograph model, weekly administration of ARX305 resulted in significant, dose-dependent, anti-tumor activity.
Pharmacokinetic studies of ARX305 in mice confirm the high ADC stability in circulation with a long terminal half-life of 16.5 days.
Price Action: AMAM shares are down 2.07% at $11.13 on the last check Wednesday.

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