HGSI's Hepatitis Drug Zalbin: When an FDA Rejection Is Good News
The FDA is none too pleased with Human Genome Sciences' (HGSI) new hepatitis C drug Zalbin (albinterferon alfa-2b), but that may be a blessing in disguise given entrenched competition and changing treatment landscape marring the drug's commercial potential.
Although the FDA isn't set to rule officially on Zalbin's approval until October, the agency sent HGSI a letter yesterday expressing concerns about the drug's risk/benefit ratio and warning that approval at the current dose is unlikely.
The setback wasn't entirely unexpected. In April, HGSI's partner Novartis (NVS) withdrew its European approval bid for the drug after receiving similar feedback.
The problem is this: HGSI was hoping Zalbin would tap into the multi-billion-dollar pegylated interferon market for hepatitis C, which is currently led by Roche's Pegasys (pegylated interferon alpha-2a) and Merck's PegIntron (pegylated interferon alpha-2b). Zalbin offers the benefit of dosing every two weeks rather than every week, but while it was technically not inferior to Pegasys in Phase III trials, it had lower virus-killing power. And in hepatitis C, killing the virus is everything.
Another problem: serious pulmonary adverse events forced HGSI to drop its highest dose part-way through the trial. And while Phase III discontinuations and serious respiratory adverse event rates were similar for Zalbin and Pegasys, the numbers were a little worse for Zalbin.
Even if Zalbin did gain FDA approval, that data could make it tough for the drug to compete against Pegasys and PegIntron. Less frequent dosing is nice, but is it worth slightly worse efficacy and side effects? And insurers might well have passed, given a trend toward requiring me-too drugs to show not just added convenience but improved clinical benefit.
There's also the issue of the changing hepatitis C treatment landscape. Other alternatives to interferon are moving through Phase II trials, with some showing a reduction in side effects. And it might still be a ways off, but many experts believe combinations of antiviral drugs will one day render interferon obsolete. At the very least, new antivirals are expected to shorten the treatment duration of interferon.
Why is any of this good news for HGSI? If Zalbin faces an uncertain commercial future, perhaps it's better to find out now instead of once HGSI has dropped a ton of money on marketing. Although HGSI hasn't revealed next steps for Zalbin, dropping or deprioritizing the drug might also please the company's investors by removing some risk.
Analysts had predicted Zalbin might generate $400 million annually -- which is more than just pocket change down the drain if HGSI doesn't advance the drug. But it pales in comparison to the $4 billion analysts expect from annual sales of the company's lupus drug Benlysta (belimumab), which is also under FDA review, and is now HGSI's absolute top priority.
Rejected photo by Flickr user smemon87, CC 2.0