Professor Claudio De Simone M.D.

In the early 1990s, I invented the 8-strain, high-potency probiotic which was ultimately studied and sold with the brand name VSL#3®* from 2002 to 2016. This product was previously distributed under a commercial agreement between VSL Pharmaceuticals, Inc., and myself.

For more than two decades, I have protected the secret formula required to produce this probiotic (also known as the “De Simone Formulation”) to ensure that patients can receive a dependable, high-quality product.

When I terminated my business relationship with the VSL company, my former partners attempted to create a “knock-off” version of my original formulation and began selling it using the same VSL#3® brand name without disclosing that the knock-off was different from the original formulation. This issue became the subject of recent litigation in U.S. Federal Court. During the course of the trial, extensive scientific data were presented to show that this new VSL#3® formulation was qualitatively and quantitatively different from my original invention.

On November 20, 2018, a federal jury unanimously found that Alfasigma USA was liable for false advertising when selling the new VSL#3® to the public.

My original formulation is now available in the U.S. and Canada only under the brand name Visbiome®. Visbiome® is distributed by ExeGi Pharma, LLC.

As a result of the litigation, VSL#3® is no longer available for sale at many retailers.

Visbiome®, however, is widely available in retail locations as well as directly on our website at

It is my commitment to you that we will continue to distribute these products in their original form, with the highest quality manufacturing processes available, and to ensure that patients and healthcare practitioners can rely on this formulation for decades to come.

I ask that you share this information with anyone whom you think should be made aware of these recent developments.


Professor Claudio De Simone

*VSL#3® is a registered trademark and is manufactured exclusively for, VSL Pharmaceuticals, Inc. Visbiome® is manufactured exclusively for ExeGi Pharma, LLC and is not affiliated with, endorsed by, or distributed by VSL Pharmaceuticals, Inc. ExeGi Pharma, LLC and VSL Pharmaceuticals, Inc. are different companies and have no affiliation with each other.