What happened

Shares of Cassava Sciences (SAVA -2.76%) were up 14.9% for the week, according to data provided by S&P Global Market Intelligence. The healthcare stock closed at $16.64 last week, fell to a 52-week low of $16.40, and then rose to as high as $19.31 on Friday. The stock is still down more than 34% so far this year.

So what

There were several factors in the clinical-stage biotech stock's rise this week. First, investors saw a potential bargain when the stock hit a two-year low, and those investors included several Cassava insiders.

On Tuesday, four Cassava executives made large buys. Company founder and CEO Remi Barbier bought 450,000 shares, chief medical officer James Kupiec bought 150,000 shares, chief financial officer Eric Schoen bought 150,000 shares, and senior vice president and general counsel Robert Cook bought 50,000 shares.

The company also shared some good news on Monday after the markets closed when it said that it had completed the enrollment for one of its phase 3 trials for simufilam to treat Alzheimer's patients. The 12-month pivotal trial includes 804 Alzheimer's patients.

Cassava said it expects to reach the target enrollment of 1,100 patients in another phase 3 trial for simufilam to evaluate the safety and efficacy of the drug in Alzheimer's patients with dementia. That study is expected to complete its enrollment in the fourth quarter, the company said.

Now what

Simufilam, an oral tablet, is the company's lead therapy, and there is legitimate excitement about its possibilities to treat Alzheimer's. Financially, though, there are concerns about the company. In the second quarter, Cassava reported it had $168.4 million in cash and no debt, but it doesn't have any product revenue, and it had a net loss of $19.3 million in the quarter. At its current burn rate, the company would run out of cash to fund operations in around three years.