Showing that old Europe can sometimes be flexible, the European Medicines Agency (EMEA) announced last week that it had reversed its decision on Amgen's (NASDAQ:AMGN) cancer drug Vectibix, allowing it on the market for a limited patient population.  

Vectibix has been approved for use as a treatment for colorectal cancer in the U.S. for nearly a year, but in May the EMEA rejected the drug for "not [having] sufficient evidence" of a benefit and for having risks of side effects that outweighed its limited benefits.

In its lone phase 3 trial for which data was available, Vectibix treated patients with late-stage refractory colorectal cancer. There was a statistically significant 36-day improvement in progression-free survival versus placebo. That's not exactly overwhelming efficacy data, considering that other colorectal cancer treatments like Genentech's (NYSE:DNA) Avastin have produced more than four months of progression-free survival advantage versus placebo, albeit in a different patient population.

Due to the way that Amgen structured its phase 3 trial, though, the overall data for Vectibix looks worse than it likely would have if the drugmaker had used a traditional study. Amgen allowed placebo patients in the 463-person study the option to cross over and use Vectibix after their disease had progressed. This may explain why the drug failed to show a statistically significant overall survival advantage in the study.

Considering that other drugs like ImClone Systems' (NASDAQ:IMCL) Erbitux and Genentech's Tarceva have already validated the class of therapies that inhibit the epidermal growth factor receptor (EGFR), in some ways the EMEA's May rejection of Vectibix was punishing Amgen for making Vectibix available to placebo patients in the study and muddying up its statistical data.

Amgen appealed the ruling, and the new EMEA decision will allow Vectibix on the market for patients whose tumors contain a gene which appears to affect Vectibix's effectiveness. Patients can be screened to see if they have this gene, so it will be easy to determine which patients will benefit from the drug - yet another example of personalized medicine. The agency's approval is conditional on pending new data about the safety and efficacy of Vectibix.

Earlier in the year, Vectibix failed in a phase 3 trial as a frontline treatment for metastatic colorectal cancer, and it hasn't been a big hit for Amgen, with sales of $96 million in the first six months of the year. Getting it approved in some form in the European Union is at least a small victory in a year full of disappointments for Amgen.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool's disclosure policy never disappoints.