Cougar Biotechnology Inc. said it has entered into private placement agreements with institutional investors to sell 2.5 million shares of common stock at $20 per share, with total gross proceeds to the company of $50 million.

Net proceeds from the financing announced Thursday will be used for ongoing clinical development of Cougar’s drug candidates. The company’s oncology portfolio includes CB7630, which is in phase 2 clinical trials for prostate cancer; CB3304, which is in a phase 1 trial in hematological malignancies; and CB1089, which is being tested for several types of solid tumors.

Sale of the unregistered securities is expected to close on May 8. Leerink Swann & Company was the placement agent for the offering.

Cougar shares were up $1.65, or 7 percent, to $22.90, in mid-day trading Thursday.