St. Paul, Minnesota-based medical device company NxThera, Inc. has raised $21.6 million in series B equity financing, the company announced last week. (A percentage of the money raised will be funded after certain milestones are met.)

Funds raised will be used to obtain European CE Mark approval and U.S. Food and Drug Administration clearance for a clinical study for the Rezum vapor ablation device in Europe, Canada and the United States, and to develop additional endourology devices.

Rezum treats benign prostatic hyperplasia via vapor injections and thermal energy, which kill tissue. Benign prostatic hyperplasia, or enlarged prostate,affects more than 32 million men in the United States, including more than 70 percent of men over the age of 60.

Investors in this second series B closing include American Medical Systems and a group of venture capital investors led by Dr. David Adair, Mitsui & Co. Global Investment, Premier Asia Capital together with Lance Wallin and Brooks Wallin, and Prolog Ventures together with Alafi Capital.

Investors for the initial series B closing included Arboretum Ventures, Aberdare Ventures and GDN Holdings.