Nektar Therapeutics (NKTR) said Monday that data from a 16-week extension period of its phase 2b study of rezpegaldesleukin showed a "deepening of response" in patients with severe-to-very-severe alopecia areata.

The company said participants treated with rezpegaldesleukin during the initial 36-week induction phase had a mean baseline Severity of Alopecia Tool score of 78.5, compared with 76.6 in placebo.

During the extension period from week 36 through week 52, Nektar said 29% of patients at low dose and 31% at high dose achieved new SALT score of 20 or less, compared with none in the placebo arm. A SALT score of up to 20 means a patient has 80% or more of their scalp covered with hair, the company said.

Shares of Nektar Therapeutics surged past 17% pre-bell Monday.