Gilead Sciences' push into oncology, which started a few years ago, seems to be paying off. Big time.

Yesterday, the biotech stopped a phase 3 clinical trial early because an interim peek at the data by the independent Data Monitoring Committee showed that its PI3k-delta inhibitor idelalisib, in combination with Roche's  Rituxan, was working better than Rituxan alone in previously treated chronic lymphocytic leukemia patients.

Data Monitoring Committees recommend that trials be ended early when there's unequivocal evidence that a drug is working. In those cases, it's unethical to continue the trial with the control group receiving an inferior drug regimen. With the trial ended, patients who want to get idelalisib will be afforded the opportunity.


Gilead was light on the details -- light is being generous... no data was presented -- but I don't know of any drug that had a trial stopped early that didn't eventually go on to gain FDA approval. The threshold for stopping a trial is so high that regulators would have a hard time concluding that the effect wasn't real.

Even Johnson & Johnson's prostate cancer drug, Zytiga, which had some controversy when the trial was stopped before an overall survival result was reached, was able to gain FDA approval. The placebo group crossing over to take Zytiga theoretically extended their survival, so Johnson & Johnson was never able to show a statistically significant increase in overall survival, but the FDA shrugged it off. Working substantially better than placebo will do that.

Gilead's investors don't have to worry about that though. Overall survival wasn't one of the endpoints of the clinical trial. Gilead said the primary endpoint, progression-free survival, is "highly statistically significant."

The data won't be important for approval, but it will be for sales. The chronic lymphocytic leukemia market is becoming crowded with Roche's obinutuzumab already under review at the FDA as a first-line therapy; a decision is expected in December. Johnson & Johnson and Pharmacyclics' ibrutinib is also being looked at by the FDA for previously treated chronic lymphocytic leukemia patients, and appears to be about two months behind obinutuzumab.

While it'll be the third of the next-generation drugs to market, Gilead could be in a good position because it set up idelalisib to be used in combination with Rituxan rather than to compete with it directly. Depending on what the data looks like, doctors may be more amenable to adding on a therapy than to switching to an entirely new one.

Idelalisib might even be used off label before the FDA approves it for chronic lymphocytic leukemia; Gilead has already submitted an application to the FDA to approve idelalisib for non-Hodgkin's lymphoma.

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The article Looking Good Gilead originally appeared on Fool.com.

Fool contributor Brian Orelli has no position in any stocks mentioned. The Motley Fool recommends Gilead Sciences and Johnson & Johnson. The Motley Fool owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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