By this spring or early summer, the addition of 12 weeks of treatment with Vertex's telaprevir to a shortened, six-month course of interferon and ribavirin will boost cure rates to 75% to 80%. Telaprevir+interferon+ribavirin will be the new standard of care for Hep C. Merck's boceprevir plus standard of care should be in the mix, too.

Look ahead a few more years. Pharmasset is dangling the prospect of an even simpler Hep C regimen: Two pills, taken once a day for six months providing odds of a cure as good as, perhaps even better, than what's achieved with the triple-drug telaprevir regimen.

As an encore of sorts, Pharmasset also wowed the EASL crowd with strong antiviral response data from studies combining PSI7977 with interferon and ribavirin. PSI7977 may be four or so years away from the market, but it's already looking like the next Hep C treatment standard bearer.

Little wonder Pharmasset shares continue to surge even after EASL ended. The stock closed Wednesday at $98.68 but was off 2% to $96 in mid-day trading Thursday. Still, remember Pharmasset shares were worth $50 one month ago.

Vertex emerged from EASL under more pressure to make the most of telaprevir commercially before competition arrives on the scene. Telaprevir is a major advance in Hep C treatment and the drug should pass easily through an April 28 FDA advisory panel and receive agency approval on or before May 23. As effective as the drug is for treatment-naive Hep C patients, the drug will have an even more beneficial effect for the hundreds of thousands of patients with Hep C virus that wasn't cured by the current standard of care.

Vertex's dilemma is that investors know this story well and have baked much of telaprevir's potential into the company's valuation already. What concerns investors today and perhaps even more post-EASL is that the slope of the expected telaprevir revenue tail may be steeper than previously appreciated. Investors are also raising questions about what Vertex is doing to sustain its Hep C franchise in 2015 and beyond when new drugs are expected to enter the market.

If you liked this article you might like

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

Hep C Deal-A-Palooza: Bristol-Myers Buys Inhibitex for $2.5 Billion

Inhibitex Shares Whipsawed by Cautious Analyst Comment

5 Big Surprise Stock Winners of 2011

5 Big Surprise Stock Winners of 2011

'Fast Money' Recap: Beaten-Up Financials Eyed