Now that

Idenix Pharmaceuticals


has found a partner for its HIV drug candidate, can

Ardea Biosciences


do the same?

On Friday, Idenix licensed rights to its HIV drug IDX899 to


(GSK) - Get Report

in a deal potentially valued at $450 million.

Next up should be Ardea, which has indicated to investors that a development partner is being sought for the company's HIV drug RDEA806.

Both IDX899 and RDEA806 are oral, once-daily drugs that belong to a class of HIV medicines known as non-nucleoside reverse transcriptase inhibitors, or NNRTIs, designed to block an enzyme HIV needs to invade healthy cells and reproduce.

The leading NNRTI today is Sustiva, marketed by

Bristol-Myers Squibb

(BMY) - Get Report

, with 2008 sales of $1.15 billion, up 20% from the previous year. Sustiva is one of the three drugs that make up Atripla, the first-ever single-pill, once-daily HIV treatment. (The other two drugs in Atripla are Viread and Emtriva from

Gilead Sciences

(GILD) - Get Report


Sustiva is susceptible to mutations in the HIV virus that make the drug lose efficacy relatively quickly, which is why new drugs in the NNRTI class are needed.

Idenix shares fell 5% to $6.14 Friday after the licensing deal with Glaxo was announced. The stock's negative reaction was due in part to the fact that investors had been anticipating a licensing deal and therefore sold once it was announced. There may have also been some investors disappointed over the $34 million upfront payment (half in cash, half in an equity investment) made to Idenix by Glaxo as part of the licensing deal for IDX899.

With Glaxo seemingly out of the HIV partnering picture for now, Ardea's challenge will be to entice one of the remaining large HIV drug players to bite for RDEA806. The list of potential licensors isn't that long and probably includes


(MRK) - Get Report



(PFE) - Get Report

and Bristol-Myers Squibb.

Johnson & Johnson

(JNJ) - Get Report

is developing its own NNRTI, currently in phase III studies, so it probably isn't interested in Ardea's drug. Gilead Sciences also probably isn't in the market for a new NNRTI, mainly because the company is focusing its research efforts in HIV on the so-called "Quad" pill, which would combine Viread and Emtriva with two new experimental drugs (elvitegravir and GS9350) into a single, once-daily pill. If approved, the Quad would be the first complete HIV treatment to be marketed by a single company.

Other companies with HIV drug candidates potentially seeking partners include

Achillion Pharmaceuticals

(ACHN) - Get Report


Progenics Pharmaceuticals

(PGNX) - Get Report


Ardea shares were 0.9%. or 11 cents, to $12.38, in recent trading.

At the time of publication, Feuerstein's Biotech Select model portfolio was long Gildead Sciences.

Adam Feuerstein writes regularly for In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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