Provectus Biopharmaceuticals, Inc. and VisiRose, Inc., its subsidiary, have secured a U.S. patent covering a topical rose bengal sodium (RB) ophthalmic formulation for treating a form of bacterial keratitis.
First, refresh is in order.
We’ll start with Provectus: The Tennessee-based clinical-stage biotechnology is developing immunotherapy medicines based on a class of synthetic small-molecule immuno-catalysts: halogenated xanthenes (HXs).
- Notably, its lead molecule in ophthalmology is RB (background on it here)
- And its lead investigational candidate is PV-305 (with an indication for infectious keratitis)
- This is essentially a light-activated version of RBS.
Tell me more about rose bengal sodium.
This is designed as a bioactive synthetic small molecule and active pharmaceutical ingredient (API) as part of a class of Provectus-developed small molecules (those aforementioned HXs).
The lead molecule’s potential lies in its antibacterial effect, which can kill drug-resistant bacterial strains across an extensive number of disease areas, including in ophthalmology.
- For a closer look at these capabilities, check out its supporting clinical data.
Anything else to know?
Yes. In 2024, Provectus launched a global licensing agreement with the University of Miami (MiamiU) to utilize its photodynamic antimicrobial therapy (PDAT) intellectual property (IP) to treat eye infections.
To note: Rose bengal PDAT (RB-PDAT) was actually developed and investigated by MiamU researchers as a form of crosslinking and an emerging adjunct treatment for infectious keratitis.
As such, this agreement sought to develop and commercialize MiamiU’s PDAT medical device in combination with an RB formulation (as RB-PDAT)—as well as establish a start-up company to focus on its advancement.
Before we talk about that start-up, tell me more about RB-PDAT?
This investigational, non-invasive, and topically-administered therapy combines a light-based device with RBS API. More background can be found here and here.
How it works: The therapy is activated with light to target bacterial, fungal, and parasitic eye infections—including drug-resistant organisms—with the goal of achieving full resolution without surgery.
Gotcha. Now circling back to that start-up—that’s VisiRose, right?
Indeed it is. The biotech company was jointly-founded in late 2024 by Provectus and MiamiU with that aforementioned global licensing agreement’s purpose as its primary goal.
More specifically: It’s focused on commercializing RB-PDAT (using Provectu’s RB) for the treatment of eye infections such as infectious keratitis—all by utilizing Provectus’s RBS API and lead asset (PV-305).
- Related: ViRose actually raised $3 million in early 2025 to advance this RB-PDAT therapeutic toward regulatory approval (among other pipeline plans).
Alrighty, I’m updated—now to this patent.
Its name: Halogenated Xanthene-Containing Topical Anti-Gram-Positive Bacterial Ophthalmic Composition and Method (U.S. Patent No. 12,661,335).
What it covers: RBS API (as a topical formulation) for treating Gram-positive bacterial keratitis, including drug-resistant strains such as:
- Methicillin-resistant Staphylococcus aureus (MRSA)
- Vancomycin-resistant Enterococcus (VRE)
Also worth noting: VisiRose will hold the patent’s exclusive ophthalmic license, enabling it to develop and commercialize ophthalmic applications under its field license from Provectus.
So what is it protecting, exactly?
This is essentially broadening the intellectual prosperity (IP) of RBS beyond the PV-305 / RB-PDAT platform to include a light-independent use of RBS API as a topical eye drop that doesn’t rely on that aforementioned light device.
Gotcha … and what else does it cover?
Five key areas pertaining to this platform therapeutic’s capabilities.
- Works without light. It kills bacteria even without needing light to activate it.
- Fights resistant germs. It's effective against tough, drug-resistant bacteria like MRSA and resistant strains of E. faecalis and E. faecium—bugs that standard antibiotics often can't beat.
- Breaks down biofilms. Many stubborn, recurring eye infections are protected by biofilms that resist normal antibiotics. This formulation clears biofilms whether or not light is present.
- Formulated for the eye. Its concentration, acidity, thickness, and salt balance are all set to match natural tears, supporting eye safety and FDA review.
- Good safety margin. In lab testing, it took much higher doses to harm healthy cells than to kill the resistant bacteria, suggesting room for repeated use as an eye drop.
So … what potential market implications might this therapeutic have?
The companies addressed this, noting its “light-independent formulation” as a typical eye drop potentially enables it to be prescribed, dispensed, and self-administered in a similar manner to that of other antibiotic eye drops.
However, where it differs is in its ability to target “resistant-organism infections” that those broad-spectrum drops are unable to reliably treat.
- Among these: bacterial keratitis (BK), chronic and recurrent blepharitis and conjunctivitis, as well as contact lens-associated infections.
Definitely sounds like a potential game-changer …
Indeed. And while the companies emphasized that this IP “further strengthens” the case for their proprietary RBS as a platform molecule, it’s not clear how this light-independent formulation will fit into Provectus and VisiRose’s current pipelines—or ongoing clinical trials.
As always, stay tuned for updates from both companies as they continue pursuing regulatory advancements for RB-PDAT, PV-305, and this new topical drop.