Ambrx Inc. completed its second private placement, raising $23.4 million to advance its first product, a human growth hormone, into clinical development.

Founded two years ago on protein biosynthesis technology developed at the Scripps Research Institute in La Jolla, Calif., the company has raised a total of $35.9 million to date. The recent financing added several new investors, including New York-based Maverick Capital, San Francisco-based CMEA Ventures, Indianapolis-based Twilight Venture Partners and Pasadena, Calif.-based Alexandria Real Estate Equities. In connection with the financing, David Singer, of Maverick Capital, will join Ambrx's board.

Existing investors Tavistock Life Sciences, of San Diego; 5AM Ventures and Versant Ventures, both of Menlo Park, Calif.; and Aravis Ventures, of Zurich, Switzerland, also participated.

"All of our investors have been very supportive," said Troy Wilson, chief business officer of Ambrx, who also co-founded the company along with Chief Scientific Officer Thomas Daniel and Scripps professor and board member Peter Schultz in April 2003.

"We closed our first financing in September of that year and it's been off to the races ever since," Wilson told BioWorld Today.

San Diego-based Ambrx's technology involves the genetic engineering of proteins with amino acid building blocks - beyond the 20 naturally occurring amino acids - to create therapeutics designed to be pharmacologically superior to existing protein-based products.

"Protein therapeutics have been around for almost a century, starting with insulin, but most of them are pretty limited in terms of their efficacy as drugs," Wilson said.

The technology combines protein therapeutics with medicinal chemistry to optimize the properties of proteins "in a manner that's analogous to what's been done for 40 or 50 years in small molecules," he added, to modify protein structure and improve therapeutic performance.

Ambrx's lead preclinical product is a PEGylated version of human growth hormone, aimed at providing therapeutic efficacy with a longer half-life that would require less-frequent dosing. PEGylated products, such as Thousand Oaks, Calif.-based Amgen Inc.'s cancer drug, Neulasta, "have really taken the market share and are much better products," Wilson said.

But there are no PEGylated products in the $2 billion growth hormone market, leaving a substantial opportunity for Ambrx, and Wilson said the company is optimistic about developing a product that requires a once-weekly, or even less-frequent, subcutaneous administration.

The company expects to file an investigational new drug application for its growth hormone product during the second half of 2006, with an initial indication in growth hormone deficiency.

Ambrx will continue preclinical work for other potential products, and plans to look at extending its technology to other applications, such as antibodies. The company also will consider partnerships to apply its technology to other companies' molecules and "build up a portfolio of candidates," Wilson said.

The recent financing is expected to sustain Ambrx for at least 18 to 21 months, but, Wilson said, the company has "some pretty exciting business development activities" and is encouraged that the funding could end up "taking us beyond that."

As well as honing the technology, Ambrx also has spent the past two years building up a solid management team. In addition to Daniels, who had served as vice president of research at Amgen and senior vice president of discovery and research at Seattle-based Immunex Corp., the company has recruited "heavyweight scientific and drug development talent," Wilson said, such as Chairman Richard DiMarchi, who, as vice president for biotechnology and products with Indianapolis-based Eli Lilly and Co., oversaw biologics and multiple product approvals.

"We're excited to have the fund raising done," Wilson said, "and looking forward to the months ahead as we continue to try to grow the business and grow the opportunity."