San Diego’s Ambrx Files for IPO to Advance Antibody-Drug Conjugates

5/5/14Follow @bvbigelow

[Corrected 5/6/14, 11 am. See below.] San Diego-based Ambrx, a biotech company with a new approach to developing protein therapeutics for treating, cancers, diabetes, and other diseases and disorders, plans to raise as much as $86 million in an IPO, according to a regulatory filing that was made public Friday. The company submitted its IPO plans confidentially on March 28th.

Using recombinant DNA-based protein biosynthesis, Ambrx can insert non-native amino acids at precisely selected sites in native proteins as they are being made within the cells. The technology enables Ambrx to impart new functionality to biotherapeutic compounds, and Ambrx has focused in particular on antibody-drug conjugates (ADCs).

Ambrx has an internal ADC drug program that includes a number of anti-cancer compounds, as well as long-acting proteins for growth hormone deficiency, weight management, and other disorders.

The company’s lead ADC product is a preclinical biotherapeutic targeting cancer cells that express human epidermal growth factor 2 (HER2). The antibody protein is conjugated with a cytotoxic drug payload, and is intended for the treatment of breast cancer and other solid tumors that express and over-express HER2. Ambrx says it expects to begin clinical trials next year with the drug, known as ARX788.

Ambrx was founded in 2003, and has raised more than $106 million in venture capital. The company says it has raised more than $200 million in non-dilutive funding by collaborating with pharmaceutical companies on particular drug development programs. The partners include Bristol-Myers Squibb, Merck, Eli Lilly, Zhejiang Medicine, and others in deals that also could eventually lead to additional milestone payments as well as royalties on the sale of collaboration products.

[Corrected to show $80 million in accumulated deficits, instead of debt.] The company has about $61.6 million in available cash, slightly more than $80 million in accumulated deficits, and 74 employees. Ambrx plans to list on the NASDAQ market under the symbol AMBX.

The biggest shareholders (followed by the size of their pre-IPO stakes) are: Tavistock BIO (19.3 percent), Maverick Capital (17.4 percent), Apposite Healthcare Fund (9.5 percent), Versant Ventures (7.5 percent), 5AM Ventures (6.9 percent), Roche (6.2 percent), and Merck (5.2 percent).

Bruce V. Bigelow is the editor of Xconomy San Diego. You can e-mail him at bbigelow@xconomy.com or call (619) 669-8788 Follow @bvbigelow

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