Novartis (NYSE: NVS) agreed to buy U.S. biotech Mariana Oncology Inc. to strengthen its pipeline of drugs that can specifically target cancer cells.

Mariana is a clinical-stage biotech with a portfolio of experimental drugs to treat a range of solid tumors, such as breast, prostate and lung cancer. The deal adds to a Novartis portfolio of targeted radioactive therapies that are led by Pluvicto, a prostate cancer treatment. The Swiss company said it will pay $1 billion upfront for the Watertown, Mass.-based firm, with an additional $750 million of milestone payments if certain targets are reached.