Clinical trials are all about numbers -- hemoglobin levels, months of extended survival -- the list could go on and on. But the most important number in any trial is the statistical significance. It tells the FDA the likelihood that the results were due to chance alone.

Developmental-stage drugmaker Novacea (NASDAQ:NOVC) reported an increased burn rate yesterday, but the announcement that it plans to increase the number of subjects in its crucial phase 3 clinical trial most likely caused its stock to tumble 9%. The increased number of subjects is a pretty good sign that Novacea doesn't think the trial can achieve statistical significance with its current number of subjects.

The clinical trial is testing the effect of Novacea's lead compound, Asentar, on patients with advanced prostate cancer. The trial was originally designed to enroll 900 subjects, but Novacea has asked the FDA to increase the number to 1,200. That increase signifies that the company thinks it might be on the border of meeting its primary endpoint of overall survival. The increased number of subjects will increase the statistical power of the trial, and it might push it under the magical p-value needed to show statistical significance.

The trial has enrolled more than 770 subjects, at a current rate of about 65 patients per month. With the increased numbers, that would put completion of enrollment at the beginning of next year, so interim results of the trial might be available at the end of next year. All of this is subject to the FDA approving the plan; a more concrete timetable should be announced after Novacea's meeting with the FDA.

The additional subjects will also increase the cost of running the trial, but that's a small price to pay if it means a positive outcome. And it looks as if Novacea can afford it. The company had $46 million in the bank at the end of the quarter, but in late June, Schering-Plough (NYSE:SGP) agreed to become a marketing partner for the drug. The deal provided an infusion of $72 million in cash, including the $12 million worth of stock Novacea sold to Schering. That cash, plus Schering's reimbursement for development costs, should see the company through the next few years without forcing it to scramble for additional capital.

Reading between the lines, Asentar probably won't be an exceedingly potent drug like Onyx Pharmaceuticals (NASDAQ:ONXX) and Bayer's (NYSE:BAY) Nexavar, whose liver cancer trial was stopped earlier this year because it worked so well. But the drug is being tested in combination with Sanofi-Aventis' (NYSE:SNY) already-approved Taxotere, so Asentar won't have to compete with the current treatment for advanced prostate cancer. Provided that Novacea can show that Asentar extends lives further than Taxotere alone, its drug should do well on the market. Hopefully, the increase in the number of subjects will help Novacea achieve that goal.

Want to know the latest drug stock we've picked for the Fool's market-beating Rule Breakers newsletter? Click here to take a look at all our recommendations with a free 30-day trial.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool's disclosure policy is always significant, statistically or otherwise.