The fate of MannKind could be decided this month, and investors have gone into a frenzy betting on the outcome.

Local billionaire Alfred Mann and his Valencia company, MannKind Corp., have spent years and about $1.5 billion developing an insulin inhaler for diabetics called Afrezza. The Food and Drug Administration’s expected decision Dec. 29 on whether to approve the product could make or break the company.

Trading volume last week was several times higher than average, and the company’s share price has gone up more than 30 percent since the beginning of the month.

“We’re seeing a lot of volatility,” said Jon Lecroy, an analyst at New York’s Hapoalim Securities. “This is a big binary decision for them.”

Adding to the activity has been conjecture that the decision will come out before the expected date as the FDA looks to clear its books before the holidays, Lecroy said.

Mann himself is wagering a huge chunk of his personal fortune that he’ll succeed where others have failed. Pfizer Inc. spent $2 billion developing an insulin inhaler, Exubera, which received FDA approval in 2006 but was pulled off the market the next year due to safety concerns and slow sales. Novo Nordisk and Eli Lilly abandoned similar inhaled insulin therapies soon after.

Mann has said that his product is safer and more convenient to use than the others.

The FDA originally was supposed to come to a decision in January, but instead asked MannKind for more clinical data and other information.

Lecroy, who rates the stock a “sell,” said he expects the FDA to delay its decision again, which would be a blow to a company because observers wonder how much more money Mann will put into the project.

“There have been several concerning signs,” he said. The FDA has not hosted experts’ panels or supplied official minutes of its meetings with MannKind, which have been negative indicators in the past.

Lecroy has set a target price of $1.

Analyst Keith Markey at New York-based Griffin Securities Inc., however, expects the FDA to sign off.

“It’s been a long time coming for this to be approved,” Markey said. “We think it’s going to be a positive assessment because the company has done enormous amounts of work to test the safety and efficacy of the drugs.”

Approval could triple the stock’s worth, he said, but the stock is likely to swing wildly until news from the FDA.

“We’re going to continue to see that volatility,” he said. “It’s all just speculation at this point.”