ImmunoCellular Therapeutics Ltd., a small Woodland Hills developer of cancer treatments, on Monday said that Chief Executive Manish Singh had resigned, effective immediately.

Founder John S. Yu, the company’s chief scientific officer and chairman of the board, will serve as interim chief executive until a replacement is found.

ImmunoCellular, which licensed its drug screening technology to larger drug makers to raise money for its own drug development projects, did not provide a reason for the departure of Singh, who was a venture capitalist before helping launch the company in 2006.