Probiotic throwdown continues w/factual dispute over clinical studies

ExeGi Pharma, LLC v. VSL Pharmaceuticals, Inc., 2026 WL 2144541, No. 19-cv-02479-LKG (D. Md. Jul. 27, 2026)

This is the latest opinion in a long and tangled sequence.

ExeGi sued VSL for tortious interference with business relationships and unfair competition arising from certain letters that VSL’s litigation counsel sent to ExeGi’s manufacturers and distributors. VSL counterclaimed against ExeGi and Professor Claudio De Simone for false advertising under the Lanham Act.

The facts involve “an eight-strain, high-potency probiotic formulation.” De Simone “obtained several patents and other intellectual property rights for his formulation, including for the probiotic formulation for the eight-strain probiotic mix known as the ‘De Simone Formulation.’” He first licensed this to VSL and it was sold under the name “VSL#3.”

He also caused samples of the eight bacterial strains comprising the De Simone Formulation to be deposited with the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH (DSMZ), which is a depository for the storage of strains and microorganisms, and not a depository for strains for industrial production. DSMZ assigns each deposit a unique alphanumeric designation. The VSL-De Simone relationship soured and he cut off VSL’s access to the manufacturer of VSL#3, instead granting an exclusive license to ExeGi (under the name Visbiome).

ExeGi incorporated the DSM Codes assigned by the DMSZ on Visbiome’s packaging and packaging inserts, alongside the genus and species name for each corresponding bacteria strain, although Visbiome has never been manufactured with the deposited material at DSMZ. Visbiome contains all eight of the bacterial strains, by genus and species, listed on Visbiome’s packaging. But VSL contends that testing of the DSMZ deposits reveals that at least three of the deposited strains do not match those listed on Visbiome’s packaging. The De Simone parties argued that any mismatch was the result of contamination introduced before the strains were deposited at DSMZ, and not a discrepancy in the Visbiome product itself.

Previous litigation resulted in an injunction against any claims in VSL#3 promotional materials “that state or suggest a false continuity between Italian VSL#3 and the De Simone Formulation, including but not limited to statements claiming that VSL#3 continues to contain the ‘original proprietary blend’ or the ‘same mix in the same proportions.’ ” VSL was also enjoyed from citing any clinical study performed on the De Simone Formulation or implying that any such study was conducted on Italian VSL#3, because they weren’t the same mix. [The first part of this sentence seems to me to offend the First Amendment.]

VSL’s litigation counsel sent a letter to counsel for Danisco—the manufacturer of Visbiome—notifying Danisco of a “recent judicial decision that directly impacts the legality of the continued sale and distribution of” Visbiome, demanding that Danisco take steps to “immediately cease and desist from the production, distribution and sale of Visbiome® unless and until any reference to the DSM Codes is removed from its packaging and packaging inserts, and from any marketing or reference materials for Visbiome®.” He claimed that any continued use of the DSM codes “would constitute a misappropriation of valuable property rights” and constitute false advertising.

VSL argued that ExeGi’s business was not impacted by this letter, because Danisco continued to fill Visbiome purchase orders for ExeGi and did not modify its supply agreement with ExeGi. ExeGi argued that the letter forced it to expend substantial resources and caused lost sales.

VSL’s counsel sent an essentially identical letter to one of ExeGi’s Visbiome sellers and distributors, and also to Amazon.

Tortious interference in Maryland requires: “(1) intentional and [willful] acts; (2) calculated to cause damage to the plaintiffs in their lawful business; (3) done with the unlawful purpose to cause such damage and loss, without right or justifiable cause on the part of the defendants (which constitutes malice); and (4) actual damage and loss resulting.” Relatedly, common-law unfair competition requires deception.

Although it was close, the court didn’t find that Maryland’s absolute litigation privilege bars ExeGi’s tortious interference and unfair competition claims. To be entitled to that privilege, VSL needed to show, among other things, that the letters that VSL’s litigation counsel sent to Danisco, Pharma Holdings and Amazon bore a rational relationship to litigation that VSL contemplated in good faith and under serious consideration. It did not provide such evidence, even though there was “a long and well-documented history of the disagreement and competition between the parties in this case related to the marketing of VSL#3 and Visbiome.”

However, ExeGi couldn’t show any damages. Danisco continued to manufacture Visbiome, and Pharma Holdings and Amazon continued to sell Visbiome after receiving the letters. There was no expert testimony about any damages. The cost of affirmatively suing for tortious interference couldn’t count, and there need to be actual damages for punitive damages to be available.

False advertising under the Lanham Act:  

VSL alleged that the De Simone Parties violated the Lanham Act by claiming that “Visbiome contains the strains deposited at DSMZ”; by stating that the current version of VSL#3 contains only seven strains of bacteria, rather than eight (De Simone also wrote that “it contains bacteria that are qualitatively and quantitatively different” and that this “counterfeit product has been falsely marketed and promoted to the public and medical community....”); by stating that VSL#3 lacks clinical studies (“has not been the subject of any published, peer reviewed, controlled trials in humans”; “untested imitation product”; etc.); by stating that VSL#3 is an imitation or knock off; and by stating that VSL#3 has been discontinued or recalled (“VSL#3 is no longer available for sale at many retailers”).

Most of these claims failed at summary judgment, though there was a factual question based on the statements that VSL#3 lacks clinical studies.

Statements about the strains deposited at DSMZ: VSL didn’t show that the De Simone Parties claimed that “Visbiome contains the strains deposited at DSMZ.” The presence of the alphanumeric DSM codes didn’t convey a false message, because there was no showing that a consumer: (1) would recognize that the letters “DSM” as referring to the Leibniz Institute DSMZ; (2) understand that the accompanying code is a scientific accession reference to a microbial deposit at the DSMZ; and (3) know that DSMZ maintains physical samples of that deposit; and then assume that the listing of the code means that the product contains material sourced from that particular deposit. VSL’s own expert “acknowledged that such a chain of reasoning is beyond the grasp of most consumers.”

Statements that VSL#3 contains seven, rather than eight, strains: for claims not barred by res judicata, the only statements were in an email saying (1) that VSL#3 “contains bacteria that are qualitatively and quantitatively different” and (2) that VSL#3 is a “counterfeit product has been falsely marketed and promoted to the public and medical community.” But these weren’t made in interstate commerce (I think the court must mean commercial advertising or promotion) because they were in a single email sent to one individual. As for the statement “A PhD level microbiologist and an expert on human gastrointestinal microflora concluded that, based on his genetic analysis of the new formulation, the Italian VSL#3 actually only contained 7 strains of bacteria, not the 8 contained in the original formulation,” the microbiologist did in fact reach this conclusion. Thus, this was literally true, not literally false.

Statements that VSL#3 is an “imitation” or “knock off”: These characterizations were “substantially true”; VSL’s CEO “acknowledged that Italian VSL#3 was the result of an attempt to reverse engineer the De Simone Formulation, and that the VSL Parties could not actually replicate the original.”

Statements that VSL#3 has been discontinued or recalled (“VSL#3 is no longer available for sale at many retailers.”): Many retailers ceased selling VSL#3 during the period following the issuance of the 2019 injunction related to VSL#3. So the explicit statement wasn’t false.

Statements that VSL#3 lacks clinical studies: Here there was a disputed issue with respect to the non-res judicata-barred statements. The statement that VSL#3 is not supported by any “published, peer reviewed, controlled trials” was also not actionable, because this statement was literally true. But other statements, e.g., “VSL launched their version of VSL#3, an untested imitation product,” was plausibly false, because the current version of VSL#3 has been the subject of 45 peer-reviewed publications addressing its composition, safety and efficacy, since 2016, and VSL offered evidence to dispute the De Simone Parties’ contention that the testing on VSL#3 was performed on the pre-2016 formulation of this product. VSL also had expert testimony about deceptiveness. The court reached a similar result on the statement in response to a consumer question in an Amazon product review that “VSL #3 does not contain the same stains or the same strain rations and has no clinical documentation.”