Archemix Corp. completed a Series A round that began more than a year ago, raising an additional $37 million to continue developing its aptamer therapeutics.

The company, founded in May 2001 with $8.25 million, extended its round in December with an additional $6.5 million, before continuing with the latest addition to raise a total of $51.75 million.

The money will be used, said Martin Stanton, Archemix president and a company founder, "most simply, to develop the aptamer therapeutics."

"We will develop drugs for ourselves, as well as develop partnerships," Stanton told BioWorld Today just before leaving to attend a company retreat.

The latest tranche, he said, should carry the company 30 months.

In November 2001, Cambridge, Mass.-based Archemix licensed the aptamer technology from Gilead Sciences Inc., of Foster City, Calif., for $17.5 million. (See BioWorld Today, Nov. 7, 2001.)

Aptamers are 3-dimensional nucleic acids that bind to molecular targets in a manner similar to antibodies, Archemix said, and could be applicable to drug discovery, target validation and affinity reagents. The company said that aptamers could be developed that bind to a particular protein or disease-related target, thereby changing the activity of that protein and generating a therapeutic effect.

Certain nucleic acids are the base for the aptamers, or drugs, and also Archemix's tools for drug discovery, called RiboReporter technology. RiboReporters, the company said, have the ability to act as molecular switches to link molecular recognition to the generation of a range of detectable signals.

The Series A funding was led by Schroder Ventures Life Sciences, of Boston; Atlas Venture, of Boston; and Prospect Venture Partners, of Palo Alto, Calif.

Atlas, Prospect and Rho Ventures, of New York, provided the initial capital to launch Archemix, and Rho also continued its support in the Series A. Other investors included Care Capital, of Princeton, N.J.; MDS Capital, of Toronto; Posco BioVentures, of Carlsbad, Calif.; and US Trust Private Equity, of Palo Alto, Calif.