Glaukos Corporation (NYSE: GKOS) has completed patient enrollment in a prospective U.S. pivotal study of the PRESERFLO MicroShunt in adults with primary open-angle glaucoma whose intraocular pressure remained inadequately controlled after previous medical and surgical treatment. The multicentre, single-arm study enrolled at least 110 patients at clinical sites in the United States and Canada and will assess its primary effectiveness endpoint 12 months after implantation.
The announcement marks the completion of recruitment, not the completion of the study, disclosure of clinical results or submission of a marketing application. PRESERFLO remains investigational in the United States, and Glaukos intends to use the eventual study results to support a future submission to the United States Food and Drug Administration.
That distinction is central to the commercial and regulatory interpretation of the update. Enrollment completion removes an operational uncertainty by confirming that Glaukos has recruited the intended difficult-to-treat population, but the device’s U.S. prospects will depend on the quality of the 12-month pressure-control data, the medication results and the safety profile recorded during follow-up.
The study is also targeting a more challenging population than patients receiving their first glaucoma procedure. Participants had previously undergone unsuccessful incisional or cilioablative glaucoma surgery and continued to have inadequately controlled intraocular pressure despite pressure-lowering medication. That makes the trial relevant to a group in which conjunctival scarring, previous procedural failure and advanced disease may complicate the outcome of another filtration procedure.
What is the PRESERFLO pivotal study designed to establish in previously treated glaucoma patients?
The primary effectiveness endpoint requires a reduction of at least 20% in mean diurnal intraocular pressure from baseline at 12 months, without an increase in the number of pressure-lowering medication classes. This is a clinically relevant composite because it asks whether the surgical intervention can lower pressure without relying on additional medication to produce the reported result.
Mean diurnal intraocular pressure is based on measurements taken at different points during the day, offering a broader assessment than a single clinic reading. For glaucoma specialists, however, the eventual interpretation will need to extend beyond whether the study crosses the prespecified 20% threshold.
The achieved postoperative pressure will matter because a percentage reduction can have different clinical implications depending on the starting value and the severity of optic-nerve damage. Patients with advanced glaucoma may require a substantially lower target pressure than those with less severe disease, particularly when vision has continued to deteriorate despite earlier treatment.
Medication burden, repeat procedures, bleb-related interventions and the distribution of individual patient responses will therefore be important parts of the evidence package. A study can meet its primary endpoint while still revealing meaningful variation in pressure control, postoperative management or the need for additional surgery.
The single-arm design also limits the conclusions that can be drawn about comparative performance. Because all participants receive PRESERFLO, the trial will not directly establish whether the device is superior or non-inferior to trabeculectomy, conventional tube-shunt surgery or another glaucoma implant in this particular population.
Instead, Glaukos will seek to generate the clinical and performance data required for a future regulatory submission. The FDA will ultimately determine whether the complete package supports the proposed indication and the applicable 510(k) substantial-equivalence standard.
Why is enrollment completion not the same as regulatory de-risking for PRESERFLO MicroShunt?
A 510(k) submission asks the FDA to determine whether a device is substantially equivalent to a legally marketed predicate device. The assessment considers the intended use, technological characteristics, performance, safety and whether any differences raise new questions of safety or effectiveness.
Glaukos described the programme as a 510(k) pivotal study, but the July 27 announcement did not identify the intended predicate device or provide a firm submission date. It also did not disclose interim efficacy or safety findings.
The company must first complete the required patient follow-up, close and analyse the database and assemble the regulatory package. Because the primary endpoint is measured at 12 months, the final participant enrolled will need to reach that point before the complete primary analysis can be conducted.
This means PRESERFLO is not yet under FDA review and has not been cleared for commercial distribution in the United States. Enrollment completion is a necessary step toward a possible application, but it does not predict whether the study will meet its endpoint, whether the evidence will satisfy the agency or how the final indication may be worded.
The trial’s eventual safety analysis will be particularly important because PRESERFLO is a bleb-forming drainage implant used through an ab-externo surgical approach. Its risk and postoperative-management profile cannot be inferred simply from the device’s small dimensions or the company’s description of the procedure as minimally invasive.
Clinicians will be interested in complications such as hypotony, bleb leakage, infection, device obstruction or exposure, choroidal events, corneal endothelial effects and the need for needling, revision or additional glaucoma surgery. The present announcement did not report any of these outcomes because follow-up is continuing.
How does PRESERFLO MicroShunt differ from Glaukos’ established angle-based glaucoma devices?
PRESERFLO is an 8.5-millimetre flexible drainage device constructed from poly(styrene-block-isobutylene-block-styrene), commonly known as SIBS. The implant is designed to divert aqueous humour from the anterior chamber to a subconjunctival bleb, creating an alternative drainage pathway intended to reduce intraocular pressure.
Its planar fins are designed to assist tissue fixation, maintain positioning and reduce leakage around the device. The surgical approach is ab externo, meaning the device is implanted from outside the eye through the conjunctival and scleral tissues.
This places PRESERFLO in a different procedural category from the angle-based micro-invasive glaucoma surgery devices with which Glaukos built much of its commercial franchise. Angle-based implants generally work through the eye’s conventional outflow system and are frequently used earlier in the treatment pathway, sometimes alongside cataract surgery.
PRESERFLO instead creates a subconjunctival filtration route and is being studied in patients who have already failed medical and surgical treatment. Its closest practical comparisons are therefore likely to involve other bleb-forming procedures, trabeculectomy and tube-shunt surgery rather than only the company’s existing iStent portfolio.
That distinction affects training, patient selection and postoperative care. Results from filtration surgery can be influenced by wound healing, conjunctival condition, surgical technique and the intensity of follow-up. The device may standardise some elements of aqueous drainage, but it does not eliminate the biological and operational complexity associated with a subconjunctival bleb.
What does earlier PRESERFLO evidence reveal about efficacy and the trade-off with trabeculectomy?
PRESERFLO has been evaluated in randomized, prospective and observational studies outside the new pivotal programme. The evidence shows that the device can lower intraocular pressure and reduce medication use, but it also indicates that the balance between pressure reduction, postoperative intervention and complications can vary according to the population and comparator.
A previous prospective randomized multicentre study assigned 395 patients to the MicroShunt and 132 to trabeculectomy. At one year, the probability of meeting the study’s surgical-success endpoint was 53.9% with the MicroShunt and 72.7% with trabeculectomy.
Mean intraocular pressure declined from 21.1 mmHg to 14.3 mmHg in the MicroShunt group and from 21.1 mmHg to 11.1 mmHg in the trabeculectomy group. Medication use fell substantially in both groups, although trabeculectomy produced the lower average postoperative pressure.
The trade-off was not one-sided. Postoperative interventions were reported less frequently in the MicroShunt arm, while transient hypotony was more common after trabeculectomy. Vision-threatening complications were uncommon in both groups during the reported one-year period.
These results do not determine the outcome of the newly enrolled study. The populations are different, and the current programme specifically includes patients whose previous incisional or cilioablative surgery was unsuccessful. Outcomes from eyes undergoing an initial filtration procedure cannot be assumed to apply directly to eyes with previous surgical failure.
Published observational evidence in refractory or previously operated eyes has produced mixed but informative results. Some studies have reported meaningful pressure and medication reductions, while also documenting needling, revision or repeat-surgery requirements. The current pivotal study is therefore important because it is designed around the specific U.S. population and regulatory use Glaukos intends to pursue.
The central clinical question is unlikely to be whether PRESERFLO can lower pressure in at least some patients. Existing evidence already supports that possibility. The more demanding question is whether the magnitude, consistency and durability of pressure control in previously treated eyes are sufficient when weighed against postoperative interventions and device-related risks.
Where could PRESERFLO fit within the treatment pathway for advanced glaucoma?
Patients with glaucoma are generally treated progressively with topical medication, laser therapy, sustained drug-delivery approaches and surgical procedures, depending on disease severity, pressure control, treatment tolerance and risk of further vision loss.
For patients requiring substantial pressure lowering after earlier treatments have failed, trabeculectomy and tube-shunt procedures remain established options. These surgeries can provide strong pressure control but may involve intensive postoperative management and clinically significant complications.
Glaukos is positioning PRESERFLO as another ab-externo surgical option for advanced glaucoma rather than as a universal replacement for conventional filtration surgery. Its potential role would depend on whether surgeons believe it offers an acceptable balance of pressure reduction, procedural predictability, safety and postoperative workload.
The enrolled population gives the company a commercially relevant but clinically difficult entry point. A device that performs adequately after previous surgical failure could extend Glaukos’ portfolio into later-stage glaucoma care and create a pathway beyond its angle-based implants and intracameral drug-delivery franchise.
Adoption would nevertheless require more than FDA clearance. Glaucoma specialists would need training and confidence in the implantation technique, patient-selection criteria and bleb-management requirements. Hospitals and ambulatory surgery centres would also assess reimbursement, purchasing arrangements, procedural time and the economic consequences of postoperative interventions.
PRESERFLO is already commercialized in markets including Canada and Australia. Glaukos holds exclusive development and commercialisation rights in the United States, Australia, New Zealand, Canada, Brazil and Mexico under a licensing agreement with Santen Pharmaceutical Co., Ltd.
Experience outside the United States can inform training and commercial planning, but it cannot substitute for the evidence required for the proposed U.S. indication. Differences in clinical practice, reimbursement, patient selection and surgeon experience can affect how real-world results translate between markets.
How important is PRESERFLO to Glaukos Corporation’s broader commercial strategy?
PRESERFLO is strategically complementary rather than central to Glaukos’ near-term revenue outlook. The company’s current growth is being driven primarily by its established glaucoma business, including iDose TR, alongside the commercial development of Epioxa for keratoconus.
Glaukos reported first-quarter 2026 net sales of $150.6 million, an increase of 41% from the corresponding period in 2025. Glaucoma sales reached $129.3 million, while U.S. glaucoma sales increased to $93.5 million.
The company raised its full-year 2026 sales guidance to between $620 million and $635 million. It ended March with approximately $280.5 million in cash, cash equivalents, short-term investments and restricted cash and reported no debt, although it remained loss-making with a first-quarter net loss of $19.8 million.
That financial position gives Glaukos the capacity to complete the PRESERFLO programme without depending on an immediate U.S. launch. It also means the company can treat the device as a portfolio-expansion opportunity while its existing products support commercial growth.
A future clearance could deepen the company’s presence across the glaucoma continuum. Glaukos would then have offerings spanning angle-based surgery, sustained intracameral drug delivery and a bleb-forming implant intended for more advanced or previously treated disease.
The commercial advantage of that breadth will depend on whether the company can create genuine clinical segmentation rather than overlapping products without clear positioning. PRESERFLO must demonstrate where it belongs, which patients are most likely to benefit and how it changes the decision between another filtration procedure and a conventional tube shunt.
What does Glaukos stock performance indicate about investor expectations?
Glaukos shares closed at $153.58 on July 24, the last completed trading session before the July 27 enrollment announcement. The stock had declined approximately 3.1% over five trading days but remained about 10.6% higher over one month.
The shares were trading near the upper end of their 52-week range of $73.16 to $161.53, giving Glaukos a market capitalisation of approximately $9 billion. That performance indicates that investors were already assigning substantial value to the company’s accelerating commercial growth and broader ophthalmology pipeline.
Because the PRESERFLO announcement was issued before completion of the pivotal follow-up period, it is best viewed as an incremental pipeline milestone rather than a near-term earnings catalyst. The study has not produced results, and a U.S. submission remains a future step.
Investor attention is also likely to focus more immediately on Glaukos’ second-quarter financial results scheduled for July 29, particularly the pace of iDose TR adoption, Epioxa execution, operating expenses and any revision to full-year guidance.
PRESERFLO could become more material to valuation once Glaukos reports the pivotal results, provides a submission timeline or receives an FDA decision. Until then, the programme adds strategic optionality but contributes limited visibility on the timing or scale of U.S. revenue.
What are the next measurable milestones for the PRESERFLO MicroShunt programme?
The first major milestone is completion of 12-month follow-up for the enrolled population. Glaukos will then need to analyse whether the study met its primary endpoint and disclose enough supporting information to evaluate the magnitude and consistency of the response.
The most useful dataset would include baseline and postoperative mean diurnal intraocular pressure, medication use, the percentage of patients meeting the primary endpoint and the proportion requiring additional intervention. Safety reporting should distinguish device-related events, procedure-related events, serious complications and subsequent glaucoma surgery.
Subgroup information may also be important because the enrolled patients could have different forms of previous surgical failure. However, any subgroup analysis will need cautious interpretation, particularly if the number of patients in each category is small or the analyses were not prespecified.
After the clinical analysis, Glaukos must prepare and submit its marketing application. The FDA will then assess whether PRESERFLO meets the substantial-equivalence requirements for the proposed use and whether the clinical, technical, manufacturing and labelling package is adequate.
Enrollment completion is therefore a credible step forward, but it is not the decisive milestone. PRESERFLO’s U.S. opportunity will be determined by whether the 12-month results show durable pressure control, stable or reduced medication use and an acceptable intervention and complication profile in patients whose glaucoma has already resisted previous treatment.
