GlaxoSmithKline Biologicals SA v. Pfizer Inc., No. 24-cv-512 (GBW) (D. Del. June 22, 2026), full opinion (PDF)
An ESI protocol that requires parent-child relationships to be preserved does not permit a producing party to strip out the attachments it deems non-responsive and drop slipsheets in their place. That is the holding of a special master's memorandum opinion and order in the Delaware mRNA vaccine patent litigation, and it arrives with a number attached: more than 110,000 withheld attached and embedded files, which the special master ordered produced within fourteen business days of the order.
The order also turns on the protocol's drafting history. Pfizer and BioNTech had proposed language that would have allowed exactly what they later did, GSK objected, and they dropped it to close the negotiation. The special master held them to that.
What happened
GSK sued in April 2024 on patents relating to mRNA vaccine technology. The court entered the parties' ESI protocol in June 2025. Paragraph 5(h) of that order addresses attachments and embedded files and provides that "[t]he parent-child relationships, i.e., the association between an attachment or embedded file and its parent document, must be preserved." The same paragraph permits a narrow carve-out, stating that "logos, junk files, and blank HTM files may be excluded from production," and gives the receiving party a route to request a specific withheld file on a good-faith showing of need.
Pfizer and BioNTech read that provision to let them withhold any attachment they considered non-responsive. Pfizer replaced more than 98,000 attachments with slipsheets and BioNTech more than 14,000. GSK, reading the same clause, reviewed and produced its own non-responsive, non-privileged family members. It then moved to compel.
The court's analysis
The dispute had already been decided once. In a consolidated opinion docketed in this case, Judge Williams had rejected an identical slipsheet proposal by Moderna under an identically worded provision, agreeing that such omissions may "render documents and email families incomprehensible, or nearly incomprehensible, and therefore useless." The special master found that ruling directly on point and saw no basis to depart from it, noting that its appearance on this docket put Pfizer and BioNTech on "unequivocal notice" of the court's views.
The defendants' fallback was to demand specificity, arguing that GSK had never identified a single document rendered incomprehensible by the missing attachments. The special master rejected the burden-shift. Judge Williams's ruling was prospective, and the rationale that non-responsive family members supply context "applies categorically, not document by document." Requiring GSK to prove incomprehensibility for each withheld file "would effectively shift PBNT's discovery obligations to GSK," and in any event GSK "has no reliable way to identify which of the more than 110,000 missing attachments might provide important context because it has never seen those documents."
Then the drafting history. The special master found that the defendants had proposed language permitting exclusion of non-responsive family members, that GSK objected, and that the defendants agreed to remove it. Having dropped the provision in negotiation, their reading of the order was, the special master held, "not well-founded and unpersuasive."
The burden arguments fared no better. The defendants had withheld the attachments without review because the files did not hit the agreed search terms. An attachment that misses a search term may still be relevant to understanding the responsive email it rode in on, and the special master held that a search-term miss, "without more, is not a sufficient basis to forgo further review." As for the compressed timeline, he found the burden "largely of PBNT's own making."
Why it matters
Family integrity clauses are boilerplate in ESI protocols, and they are usually negotiated as a technical detail about how documents are produced. This opinion treats one as a substantive obligation with teeth. Where a protocol enumerates the excludable categories, that enumeration is the limit, and a producing party's own responsiveness judgment about a child document is not a hidden additional exclusion.
The negotiation record is the sharper lesson. Language that a party proposes and then withdraws does not survive as an interpretive gloss on the language that replaced it. Counsel who trade away a provision to close out a protocol should assume the other side will produce the redline when the issue resurfaces, and should plan their production accordingly rather than reclaiming the point by construction two years later.
There is also a workflow point that outlives this case. Culling attachments by search-term hit treats a term match as a responsiveness determination. It is not one, and a protocol that requires families to travel together does not care whether the child document would have been produced on its own.
The full opinion is available as a PDF.
