NeuroOne Medical Technologies (NMTC) said late Thursday it began a proposed underwritten registered public offering of its shares.

The company will sell all the shares of common stock in the offering.

In addition, the company intends to grant the underwriter a 45-day option to purchase up to an additional 15% of the shares sold in the offering.

Shares NeuroOne Medical were down over 36% in after-hours activity.