Zenflow raises $52M with Cook leading its prostate implant rollout

Zenflow has closed a $52 million Series D to expand Spring, a removable implant that urologists place during an office procedure to relieve urinary obstruction caused by an enlarged prostate. Cook Medical led the financing and signed on as Zenflow’s exclusive United States distributor, pairing fresh capital with an established route into urology practices.

The Spring is a small, coil-like nitinol implant. A clinician delivers it through a single-use flexible cystoscope, uses an integrated balloon to position it and chooses among three sizes. Once placed, the implant props open the urethra without cutting, burning or removing prostate tissue; it can later be retrieved if another treatment is needed.

Zenflow is trying to occupy the gap between medication and more invasive procedures. The company reported that 99% of participants in its pivotal study avoided a post-procedure catheter and that their mean International Prostate Symptom Score improved 37%. Those are clinical-trial results from Zenflow, not evidence of performance across a broad commercial rollout.

Commercialization had already started before this round. Zenflow said in September that four United States centers had completed their first Spring procedures after the device won FDA approval in December 2025. The new capital is funding expansion of an approved product, rather than the regulatory work that defined its prior financing.

Cook also led Zenflow’s $24 million Series C in 2024, when the money was earmarked for an FDA submission and launch preparation. ClavystBio joined the new round, while Invus Opportunities, F-Prime and Medtech Venture Partners returned. Zenflow also named HSBC Bank USA and Trinity Capital as venture-debt providers, but didn’t disclose the equity-debt split.

Cook’s role now extends beyond lead investor to sole United States distributor. The agreement gives Zenflow access to Cook’s existing urology relationships as it moves beyond four early sites, while Zenflow contributes the operational and clinical work around the implant.