It appears Alfred Mann still has faith in MannKind. That is, MannKind Corp. of Valencia.

Mann, chief executive of the pharmaceutical developer, recently upped his stake in the company to nearly 50 percent, showing confidence in his company that has been down a bumpy road with the Food and Drug Administration.

It’s a sign that MannKind is still moving forward in its development of an inhalable insulin treatment for patients with diabetes, even though Mann has said his patience has its limits.

Matthew Pfeffer, chief financial officer for MannKind, said Mann’s recent investment is proof he’s still optimistic.

“Clearly he’s a believer in the product and its potential,” Pfeffer said.

That company’s determination stands in contrast with New York’s Pfizer; Bagsvaerd, Denmark’s Novo Nordisk; and Indianapolis’ Eli Lilly & Co., which all pulled out of the inhalable insulin market.

Investor interest peaked in early 2011 when MannKind’s inhaler, Afrezza, was expected to win FDA approval. But instead, the agency told the company to conduct more tests.

MannKind is convinced that Afrezza will prove to be better than other attempts at inhalable insulin, and Mann increased his stake in the company by converting $77 million of debt into equity.

Mann’s move will buoy the company’s funding through the fourth quarter and help MannKind pay off part of a $350 million promissory note that had previously been issued by Mann Group LLC, which Mann oversees.

Jason Butler, analyst at JMP Securities LLC in New York, said the move gives MannKind better potential to raise more money in the future.

Keith Markey, an equity analyst at Griffin Securities Inc. in New York, said the additional funding could explain some recent volatility in the stock price.

After the July 3 announcement, shares rose from $2.46 to trade briefly at $2.91 on July 10. On July 11, however, they plunged to $2.42, down about 6 percent for the week. The S&P 500 fell 2.4 percent for the week.

Tom Russo, a Robert W. Baird & Co. analyst in Chicago, said he wouldn’t be surprised if the stock dropped below the $2 mark. More than any other stock he knows, MannKind trades on sentiment and faith in the leadership.

Mann made his fortune founding 17 companies in his career. Nine were acquired at a combined total of almost $8 billion.

Better than Exubera?

The company’s fortunes depend on Afrezza, an inhalable insulin prototype.

Only one inhalable insulin device has made it to market, Pfizer’s Exubera. The product was eventually axed, costing Pfizer nearly $3 billion. Diabetic patients thought it was bulky and wasn’t much of an improvement over injectable insulin.

But Pfeffer said Afrezza is better than Exubera. It fits in the palm of a hand, is cheaper and acts more quickly.

MannKind is enrolling trial participants for its final hurdle toward drug approval. Trial data is expected to be completed in early 2013. Results will then be released to the public and then resubmitted to the FDA.

“We’re getting closer to the finish line here, and I think over time that’s going to have some effect on the stock price,” Pfeffer said.

Markey said investors aren’t excited about MannKind because there won’t be any news on the tests for some time.

“News flow is crucial to maintaining investors’ interest in stock when a company doesn’t have earnings,” he said.

But he believes the company will prevail.

“Because of unique characteristics of Afrezza, I think they’re going to win a significant portion of the market share,” he said.