'The Street' contributor Adam Feuerstein on IDX184...

The Street.com's  Adam Feuerstein puts his 2 cents in on Idenix's IDX184 nucleoside analog, who came back from the dead after the FDA suspended a trial involving IDX184 and protease inhibitor IDX320 (plus peg and riba) in September of 2010 after three healthy volunteers experienced elevated liver enzymes. It's now clear that IDX184 appears to be safe, but there are questions regarding it's potency, especially in light of recent data from Pharmasset's PSI-7977 and Inhibitex's INX-189 which may put it at a possible competitive disadvantage. To throw my 2 cents in and add to the kitty, 'safe' is really a good thing in this space looking at the Phase II wasteland of HCV drugs. All these second generation drugs still have a way to go in development. If developers are betting on a 'nuc' backbone, the drug that ultimately has the best safety profile may garner itself a competitive advantage, even if it takes a bit longer to clear virus

Idenix Pharma's Hep C Drug Safe But Slow (And Ready For Sale)

SAN FRANCISCO (TheStreet) -- Idenix Pharmaceuticals'(IDIX_) experimental hepatitis C drug IDX184 looks to be safe (whew!) but doesn’t appear to work particularly fast (uh oh….)

On Monday morning, relief over the apparently clean safety report for IDX184 combined with a healthy dose of hepatitis C drug takeover speculation was all the fuel needed to send Idenix shares up $2.84, or 43%, to $10 in the pre-market session. [Achillion Pharmaceuticals(ACHN_) share, likewise, are up 35% to $10.65 on takeover speculation and positive data reported on its pipeline of hepatitis C drugs.]

Idenix's lead drug, IDX184, belongs to the same "nucleoside" or "nuc" class of oral Hep C drugs as Pharmasset's PSI-7977 and Inhibitex's INX-189. Since both were acquired for huge premiums recently, popular thinking is that Idenix's turn at the altar is imminent.

After 31 hepatitis C patients completed 28 days of treatment with IDX184 in combination with weekly interferon and ribavirin, no serious adverse events were reported and an independent safety monitoring board recommended that more patients can be enrolled in the phase II study, Idenix said Monday.
Based on this clean safety report, Idenix plans to ask U.S. regulators to remove a clinical hold on IDX184 put in place last year. The company reported the new IDX184 in advance of its presentation this afternoon at the J.P. Morgan Healthcare Conference.

Idenix said that 73% of patients treated with a 100 mg dose of IDX184 reported undetectable levels of the hepatitis C virus after 28 days. At a median treatment duration of 8 weeks in the study, 87% of these patients are now undetectable.

For patients treated with a lower, 50 mg dose of IDX184, 63% were undetectable at 28 days and 94% were undetectable at a median treatment duration of 8 weeks. None of these patients in the study have so far reported a re-emergence of the hepatitis C virus in their systems.

These efficacy data suggest that IDX184 works slower and perhaps is not as potent as the competing "nucs" being developed by Pharmasset and Inhibitex. For example, Pharmasset's PSI-7977 demonstrated a 4-week early response rate of 98% in a similar setting and patient population. Moreover, Idenix enrolled relatively healthier hepatitis C patients for this initial IDX184 study, suggesting that the drug may further underperform when hepatitis C patients with more advanced disease are treated.

"For us, this trial was about solidifying the safety profile of IDX184 as much as anything else. We believe we have demonstrated that and hope the FDA agrees with us. Our goal is to get to interferon-free regimens as soon as possible," said Idenix CEO Ron Renaud, in an email.

Renaud downplayed questions about the speed at which IDX184 can clear the hepatitis C virus, arguing that combinations of different types of oral drugs will likely be needed ultimately, but it's not clear yet what those combinations might be.

It's certainly true that big players in the race to develop an all-oral hepatitis C therapy --Bristol-Myers Squibb, Gilead Sciences most prominently -- are betting on a "nuc" being the backbone of whatever regimen emerges. And right now, Idenix is sitting on a nuc -- IDX184 -- that appears safe and is certainly available to any interested bidder for the right price.