Dendreon expects to spend up to $50 million to expand its therapeutic biotechnology-processing facility in Morris Plains, N. J., the company said Monday...

Dendreon expects to spend up to $50 million to expand its therapeutic biotechnology-processing facility in Morris Plains, N.J., the company said Monday in a regulatory filing.

The Seattle biotech — which is seeking Food and Drug Administration (FDA) approval for its prostate-cancer immunotherapy, Provenge — has hired The Henderson Corp. to manage construction of a two-phase expansion of its Morris Plains facility.

The plant is where a patient’s immune cells would be processed to increase the body’s ability to fight prostate cancer, before being reinfused into the patient.

Additional quality-control laboratories, data center, training areas, infrastructure and offices are scheduled to by done by mid-December. The final phase, with additional manufacturing clean-room work stations, production-support areas, warehouse, infrastructure and offices, is to be substantially complete by late April.

Dendreon finished the initial build-out of its 158,000-square-foot facility in July 2006, before its FDA application was tabled to await additional clinical results.

Last month, Dendreon raised net proceeds of $221 million by selling nearly 12 million shares at $19.20 apiece. The company’s stock fell $1.54, or 5.9 percent, to $24.54 Monday.