Last week, Vertex Pharmaceuticals (NASDAQ:VRTX) concluded one of the most important quarters in its history, with the announcement of its second-quarter financial results. Like the vast majority of biotech drugmakers, Vertex's financials proved less crucial than the clinical trial results from the drugmaker's pipeline.

During the quarter, we all got a better glimpse of the excellent data for Vertex's second large phase 2 study of its lead drug, telaprevir, in hepatitis C genotype 1 patients. The study, called PROVE-2, should signal to all investors that Vertex and partner Johnson & Johnson (NYSE:JNJ) have a compound with very high odds of eventually gaining marketing approval worldwide.

Unfortunately, we also found out in the second quarter that Vertex (in the U.S.) and Johnson & Johnson (in Europe) likely won't be filing marketing applications to get telaprevir onto the market until after their phase 3 studies in newly diagnosed hepatitis C patients are completed in 2010. Add some necessary time to collect all the data and submit the drug for regulatory review, and telaprevir most likely won't be on the market for newly diagnosed hepatitis C patients in the U.S. or Europe until the first half of 2011.

Today, Vertex's main rival in hepatitis C treatments, Schering-Plough (NYSE:SGP), announced excellent new phase 2 data for its competing compound, boceprevir. In response, Vertex shares fell 10%. I've always argued that telaprevir will face stiffer-than-expected competition from drugmakers like Schering, Gilead Sciences (NASDAQ:GILD), Novartis (NYSE:NVS), and Roche. In addition, other compounds in early development from drugmakers like InterMune (NASDAQ:ITMN) and Pharmasset (NASDAQ:VRUS) look similarly promising.

With so many top hepatitis C drugmakers pouring large amounts of resources into their own (or partnered) antiviral drug programs, telaprevir will inevitably face direct competition in the future. Nonetheless, telaprevir has produced the most robust data by far, in the largest number of patients, of all the hepatitis C compounds currently in testing.

Investors can't ask for much more than a near-certain approval for a drugmaker's lead candidate. Vertex and its strong telaprevir data almost definitely provided this in the second quarter. As long as no major safety issues pop up in phase 3 tests, we should see telaprevir start producing sales and royalty revenue for Vertex no later than 2011.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. Johnson & Johnson is an active Income Investor pick. The Fool has an A+ disclosure policy.