(Reuters) - Shares of Onyx Pharmaceuticals Inc (ONXX.O), known for its liver cancer drug Nexavar, jumped more than 20 percent on Monday, after Bloomberg reported the company was exploring options, including a possible sale.

The company, which had a market capitalization of $2.4 billion before Monday's gains, is working with Centerview Partners LLP to review alternatives, Bloomberg reported, citing two people with knowledge of the matter.

An Onyx spokeswoman declined to comment on the report. Centerview Partners was not immediately available for a comment.

South San Francisco, California based Onyxx markets its big-selling drug Nexavar under a partnership with German drugmaker Bayer AG (BAYGn.DE). The drug, which is also marketed as a treatment for kidney cancer, is being studied as a potential treatment for breast cancer.

Any potential buyer of Onyxx will have to share rights of Nexavar sales with Bayer and Japanese marketing partner Ono Pharmaceutical Co Ltd (4528.OS).

Last month, Onyx and Bayer reached a settlement over a contested sister compound to Nexavar.

Onyxx is also currently conducting late-stage trials on its experimental multiple myeloma drug carfilzomib, which is a proteasome inhibitor similar to Takeda Pharmaceutical Co Ltd's (4502.T) commonly used Velcade for the same treatment.

Onyxx shares closed up 14 percent at $42.80 on Nasdaq. They had touched a more than two-year high of $46.07 earlier in the day.