Mersana Therapeutics (MRSN) said Friday that the US Food and Drug Administration recently granted an additional Fast Track designation to XMT-1660 for the treatment of advanced or metastatic breast cancer in patients with human epidermal growth factor receptor 2 low or HER2-negative disease, including triple-negative breast cancer, who have received a prior topoisomerase-1 inhibitor antibody-drug conjugate, the company said.

The FDA previously granted the drug Fast Track designation for the treatment of adult patients with advanced or metastatic recurrent triple-negative breast cancer.

The company also said that the World Health Organization has approved emiltatug ledadotin as XMT-1660's international nonproprietary name.

Shares of the company were up more than 15% in Friday's premarket activity.