LONDON - RiboTargets Ltd, a discovery company specializing in the structure-based design of small-molecule drugs that bind to RNA, raised #6 million (US$9 million) in its second-round funding.

CEO Simon Sturge told BioWorld International, "We went out to raise #4 million and had such a good response we decide to go up to #6 million, so I'm very pleased."

Current shareholders Apax Partners, 3i plc, Advent Venture Partners and Kargoe all took part, with three new investors - NIB Capital, Rendex and Quester. This is the first time that NIB Capital, one of the largest venture capital investors in the world, has put money into a privately held UK biotechnology company.

The money raised will last for two years, by which time RiboTargets, based in Cambridge, expects to have one corporate deal.

The funding will allow the company to advance its HIV program into preclinical development, complete lead optimization in its most advanced antibacterial program, and further develop its proprietary docking software, RiboDock.

Sturge said the company has a lead series that shows antiviral activity in HIV in a cell-based assay. "This is now going into tox[icology], and we will then do more lead optimization before going into preclinical studies in 2001, and Phase I in 2002." While currently available anti-HIV drugs knock out the circulating virus, the RiboTargets compound is targeted at the latent form of HIV.

In its antibacterial program, the company has identified a selective inhibitor of bacterial translation that interrupts protein synthesis in both Gram-negative and Gram-positive bacteria. "We found this with our proprietary structure-based design and screening software RiboDock," Sturge said. "From completing the structure [of a target in the bacterial ribosome] it took us 12 weeks to screen 1.2 million chemical compounds. This is incredibly fast in comparison to wet screens."

There are many known targets on bacterial ribosomes, and to date RiboTargets has elucidated the structure of three others. The docking software also can be used for lead optimization.

Sturge says RiboTargets is the only company that is taking a structure-based approach to RNA drug discovery. He believes such an approach is essential since RNA can take on different conformations with different targets, and because RNA is electrically charged, making it easy to find drugs that will bind to it. "The difficulty is to make them specific enough. So knowing the structure is very important because it allows you to build specificity in."

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