ImmunoCellular Therapeutics Ltd. has decided to voluntarily delist its shares from the New York Stock Exchange and to curtail its operations because of “significant obstacles to its continued operations which cannot be overcome,” the Calabasas biotechnology firm announced Monday.

In connection with decision to delist, ImmunoCellular Chief Executive Dr. Anthony Gringeri, Chief Financial Officer David Fractor and Senior Vice President of Research Dr. Steven Swanson resigned from the company effective Oct. 15.

It’s unclear what form the company will take going forward. Citing its weakening financial position, lack of financing, expenses related to ongoing litigation and challenges to stay complaint with the stock exchange, ImmunoCellular said it may continue to pursue partnerships, sales and licensing of its intellectual property but that “there can be no assurances that any actions will be taken as a result of these efforts.”

Last year, the NYSE notified ImmunoCellular that it was out of compliance with the exchange’s guidelines, which require stockholders' equity for a listed company to be at least $6 million if that company has sustained losses in its five most recent fiscal years. ImmunoCellular had until Dec. 23 to regain compliance, but its board of directors instead decided the company had “no other alternative than pursuing the delisting and deregistration course and curtailing operations.”

After the announcement Monday, the company’s shares dropped 77 percent to a fraction of a cent. Its stock now trades on the over-the-counter market.