Zenflow, Inc.

Zenflow is a South San Francisco medical device company that built the Spring, a small nitinol coil implanted through a flexible cystoscope to prop open the urethra and relieve the symptoms of an enlarged prostate (benign prostatic hyperplasia). Spun out of Stanford's Biodesign program in 2014, the company won FDA approval in December 2025 for a first-line interventional therapy that requires no catheter afterward, preserves sexual function, and can be reversed. It has raised roughly $85 million across multiple rounds and ran the multinational BREEZE pivotal trial to get there.