Xencor Inc., a biotechnology company based in Monrovia, has signed an agreement with Genentech Inc. valued at up to $280 million to develop a drug to battle cancer and other diseases.

The clinical-stage biotech firm announced Feb. 5 it had entered into a research and licensing agreement to develop a range of antibody drugs with the South San Francisco-based subsidiary of Roche Holding AG of Switzerland.

Genentech agreed to pay Xencor an initial $120 million plus up to $160 million for performance milestones to develop an IL-15 immunotherapy known as XmAb24306.

The two companies also entered a two year partnership in which Xencor would get up to $180 million in milestones for each new IL-15 drug candidate that uses Xencor’s antibody technology to stimulate an immune response for the treatment cancer and other illnesses.

“This partnership with Genentech accelerates our immune-oncology work by enabling the exploration of novel XmAb24306 combinations with Genentech’s leading oncology portfolio and our growing internal pipeline of bispecific antibodies,” said Bassil Dahiyat, chief executive of Xencor, in a statement.

The 22-year-old publicly traded biotech company has a pipeline of 12 engineered monoclonal antibodies targeted at treating autoimmune and allergic diseases, asthma and cancer.

In addition to Genentech, Xencor has partnered with drug makers Novartis AG, Amgen Inc., MorphoSys AG, CSL Ltd., Alexion Pharmaceuticals Inc., and Boehringer Ingelheim GmbH.

At the close of the markets Tuesday, shares in XNCR had risen 0.3 percent to $36.54, with a market cap of $2 billion.

Health business reporter Dana Bartholomew can be reached at [email protected]. Follow him on Twitter @_DanaBart.