US 12571803

Summary — U.S. Patent No. 12571803 (US12571803B2)

Bibliographic data

Abstract (as published): "The present invention, in some embodiments, generally relates to methods of determining a treatment protocol for and/or a prognosis of a patient's recovery from a brain injury. In some embodiments, the brain injury results from a hypoxic event. In some embodiments, methods are provided for determining a measure of the concentration of tau protein in a patient sample containing or suspected of containing tau protein."

Plain-language overview of the independent claims

Caveat on the claims: The authoritative patent text provided to me (Google Patents fetch) does not include the granted claims section — it ends mid-way through the specification (Example 1). My USPTO/CAFC docket searches also did not return the granted claim text for this specific patent number. Therefore I cannot quote or itemize each independent claim verbatim with confidence. What follows is an inference from (a) the post-grant title, (b) the specification's independent-claim-style embodiments, and (c) the search-confirmed family data — flagged as inferred, not verbatim:

1. Method of producing a bodily fluid sample containing an analytically quantified amount of phosphorylated tau protein — Likely an independent claim directed to producing a bodily fluid sample (e.g., blood, plasma, or serum) in which an analytically quantified amount of phosphorylated tau protein is present, typically by obtaining the sample from a subject (e.g., following brain injury/hypoxic event) such that the phosphorylated tau is present at a concentration measurable by an assay having a very low limit of detection (stated in the specification as, e.g., less than about 0.2 pg/mL, with LOD as low as about 0.02 pg/mL and LOQ about 0.04 pg/mL in some embodiments).
2. Assay/detection-based method claims — The specification discloses methods of performing an assay (e.g., a single-molecule/digital immunoassay with single-molecule array-type spatial segregation) to determine a measure of the concentration of tau (including phosphorylated tau such as p-tau-181 or p-tau-231) in a patient blood/plasma/serum sample.
3. Prognosis/treatment-protocol method claims — The specification's original independent claims were directed to determining a treatment protocol and/or prognosis of recovery from brain injury (e.g., from a hypoxic event such as cardiac arrest) based on measured tau concentration, including area-under-the-curve analysis over serial samples (e.g., ≥48 hours) and evaluation of a secondary tau peak (AUC thresholds of ~800 for total curve and ~500 for the secondary peak correlating to poor vs. good CPC outcomes).

Honesty note: Because the granted claims were not retrievable in the materials I could access, I cannot confirm how many independent claims issued, their exact scope, or whether the granted claims are limited to "producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau protein" (per the issued title) versus the broader prognosis/treatment methods of the originally filed family. Treat the claim overview above as provisional.

USPTO / CAFC 2026 docket search results

• USPTO database: Searches for the exact number "12571803" / "US12571803B2" confirmed the bibliographic record via Google Patents-indexed USPTO data (title, assignee Quanterix Corporation, priority 2011-04-12, grant 2026-03-10). I could not pull the granted claim text from the USPTO in my searches.
• CAFC 2026 dockets: No CAFC appeal docket specifically naming U.S. Patent No. 12571803 was found. Searches for "12571803" CAFC appeal Quanterix returned no results.
• Related litigation (caution): Google Patents flags the patent family as having "first worldwide family litigation." A D. Del. case, Fujirebio Diagnostics, Inc. v. Quanterix Corporation (1:25-cv-00659), was found in search results; the court filings I retrieved concern U.S. Patent No. 11,275,092 (a related tau-detection patent in the same family/portfolio, asserting § 101 ineligibility). I found no evidence in my searches that the '092 litigation or any CAFC 2026 proceeding specifically involves patent number 12571803, so I am not treating that case as covering this patent.

Key uncertainties

• Exact independent claim count and verbatim scope of US12571803B2 (claims section not available in the supplied text or search results).
• Whether any pending or filed CAFC 2026 appeal or district-court case names 12571803 itself; my searches found none, which is not affirmative proof that none exists.

Findings on litigation involving U.S. Patent 12,571,803

No litigation specifically naming U.S. Patent 12,571,803 B2 has been identified in the available records as of April 26, 2026.

A few important points on why, and what related activity does exist:

1. The patent is very new

U.S. Patent 12,571,803 B2 ("Methods of producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau protein," assigned to Quanterix Corporation) was granted on March 10, 2026 — only about six weeks before the current date. Because the grant is so recent, no complaint, amended pleading, or IPR petition specifically identifying this patent number would be expected yet, and none surfaced in searches of PACER/CourtListener-derived sources, Unified Patents-style litigation listings, or news coverage.

2. Related litigation exists, but it involves a different patent number (do not confuse them)

Google Patents flags the patent family (Darts-IP family 47009972) as having litigation. The litigated patent in that family is U.S. Patent 11,275,092 B2 — a different patent number from the one you asked about:

• Case: Fujirebio Diagnostics, Inc. v. Quanterix Corporation, No. 1:25-cv-00659 (D. Del.)
• Filed: May 28, 2025
• Plaintiff (DJ): Fujirebio Diagnostics, Inc.
• Defendant/Counterclaim-plaintiff: Quanterix Corporation
• Patent-in-suit: U.S. Patent No. 11,275,092 (the "’092 patent"), not 12,571,803
• Nature: Fujirebio sought a declaratory judgment of non-infringement of the ’092 patent; Quanterix counterclaimed for infringement (later also naming Fujirebio Europe N.V.); Fujirebio moved to dismiss the counterclaims on § 101 grounds and filed IPR2025-01060 challenging the ’092 patent.
• Status per litigation databases: The district court action was ultimately dismissed without a merits ruling on validity; each party bore its own costs. (Sources: CourtListener docket for 1:25-cv-00659; PatSnap litigation summary; PTAB petition documents.)

US 12,571,803 is a later-issued continuation in the same family (same priority date of April 12, 2011), but none of the identified pleadings, docket entries, or PTAB papers in that dispute reference patent number 12,571,803.

3. Bottom line

• Known litigation specifically involving US 12,571,803: none identified.
• If you are tracking the family, the active/known dispute is the Fujirebio v. Quanterix matter over US 11,275,092, which should not be conflated with 12,571,803.

Given the patent issued only in March 2026, I'd recommend a PACER watch on Quanterix's dockets (D. Del., D. Mass., and the PTAB) for any future complaints or amendments that may add 12,571,803 or its sibling 12,540,950 — but as of today, no such case exists in the records I can access.

Proceedings overview

There are zero AIA trial proceedings (IPR/PGR/CBM) on file against US 12571803 — none active, none institution-denied, none settled, and no claims invalidated or sustained — so the patent is completely untested before the PTAB, and a defendant today faces a patent whose claims have not been narrowed by any AIA proceeding, but which is also newly issued (2026-03-10) and belongs to a Quanterix tau-diagnostics family that is being actively litigated (including an IPR against the parent patent).

Per-proceeding detail

No proceeding exists to report on this patent. Per the USPTO ODP structured data in this prompt: "The USPTO ODP API returns no AIA trial proceedings for this patent as of the most recent ingest." Targeted web searches for "US12571803", "17/674,968", and 2026-dated IPR/PGR petition numbers returned no PTAB proceeding against this patent number (searches run 2026-09-08). I will not invent a proceeding number or a Final Written Decision where none exists.

Related-family activity (NOT on the '803 — flagged so it is not confused with a proceeding on this patent)

Web search surfaced activity on family members, which is material context for a defendant but is not a proceeding against US 12571803:

• IPR2025-01060 — Fujirebio Diagnostics, Inc. v. Quanterix Corp. — Petition for inter partes review of US 11,275,092 (the parent in this family, application 16/522,237, titled "Methods of determining a treatment protocol for and/or a prognosis of a patient's recovery from a brain injury"). Petition filed 2025-05-28 per the petition and parallel DJ filing. Patent Owner (Quanterix) filed a preliminary response arguing discretionary denial under 35 U.S.C. § 325(d) (art already of record) and noted the parallel Delaware case. I could not confirm from available sources whether the Board instituted, denied, or terminated this IPR — do not rely on any assumed outcome; check PTAB E2E for the decision.
• Fujirebio Diagnostics, Inc. v. Quanterix Corp., No. 1:25-cv-00659 (D. Del.) — filed 2025-05-28 by Fujirebio seeking a declaratory judgment of noninfringement of the '092 patent; Quanterix counterclaimed infringement. Per secondary reporting, the case was dismissed on 2026-04-10 by joint stipulation under Fed. R. Civ. P. 41(a)(2)/(c): Quanterix's infringement claims dismissed with prejudice, Fujirebio's DJ claims dismissed without prejudice, each party bearing its own costs. No merits ruling on validity or infringement.

The '803 is a later continuation (filed 2022-02-18 from the same chain as the '092) with a different claim scope — its title is "Methods of producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau protein" — so none of the above touches the '803's claims, and Quanterix has continued prosecuting the family (e.g., US 12,540,950, "Methods of assaying phosphorylated tau protein in a sample," granted 2026-02-03).

Strategic summary

Claim status: Because no AIA proceeding has ever been instituted on US 12571803, every claim of the patent is untested by the PTAB — none canceled, none confirmed, none even challenged in a petition bearing this patent number. The patent issued only ~6 months ago (2026-03-10), which explains the absence of PTAB activity: a petition cannot be filed against an unissued patent, and any defendant served with a complaint on the '803 today is inside the one-year § 315(b) window.

Estoppel landscape: There is no § 315(e)(2) estoppel barrier specific to the '803 — no petitioner has ever been estopped against it. The only estoppel-relevant activity is in the parallel family: if Fujirebio (or a privy) pressed grounds against the '092 in IPR2025-01060 and that proceeding reached institution, estoppel would attach to those grounds for the '092, not automatically for the '803 (a later-issued continuation is a separate patent requiring its own petition). For a defendant facing the '803 today, all § 102/§ 103 grounds based on art predating the 2011-04-12 priority date remain available, subject to the usual diligence requirements. Practical caution: the prosecution history of the '092 (where the Examiner withdrew obviousness rejections over Quanterix's own Simoa disclosures and Wunderlich/Mortberg after applicant arguments) shows the Office has already considered — and the patent owner will argue § 325(d) applies to — much of the most obvious tau-in-blood art for this family.

Pattern signals: Quanterix is enforcing this family affirmatively (CEO statements targeting p-tau 217 blood tests measuring below ~5 pg/mL with LOQ below ~0.2 pg/mL; the Fujirebio DJ suit and counterclaim). Fujirebio is the identified challenger against the parent '092, not a defensive aggregator. The family is marked in Darts-IP as having "first worldwide family litigation." No evidence surfaced of Unified Patents or other aggregators, of repeat IPRs against this specific patent, or of any PTAB appeal by Quanterix — because there has been no PTAB merits decision on any patent in this chain to appeal. Quanterix's litigation behavior so far (a stipulated, with-prejudice dismissal of its infringement claims in the Delaware case as to the '092) is a signal that enforcement posture can shift — but it does not bind or estop Quanterix on the separately issued '803.

Recommended next steps

1. Confirm the baseline before spending money: There is no PTAB proceeding on US 12571803. Verify that yourself on the USPTO PTAB E2E / ODP lookups by patent number (12571803) — the ODP ingest in this prompt is current, but re-check at the moment you are served, because a petition against a 2026-03-10 patent could be filed at any time and the record could change quickly.
2. If you have been served on the '803, the clock is running: An IPR petition must be filed within one year of service of a complaint (35 U.S.C. § 315(b)). Do not let the "no PTAB activity" status lull you — the absence of a proceeding is not a merits signal; it is a timing artifact of a newly granted continuation in a family its owner has publicly said it will enforce.
3. Watch IPR2025-01060 (against the '092) as a leading indicator. Its institution decision, if any, will preview how the Board treats this family's claim scope, the § 325(d) arguments Quanterix deploys, and the viability of the Simoa/tau-in-blood art as a § 103 tool. If Fujirebio's petition was denied, expect Quanterix to cite that denial in any future fight on the '803; if it was instituted, the FWD (due ~1 year from institution) will give you a roadmap of winning grounds and expert framing. Verify the docket at PTAB E2E (PTAB decision pages) — I could not confirm the institution outcome from public search results.
4. Scope your own petition to the '803's actual claims. Do not copy the '092 petition: the '803's claims are directed to producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau — confirm the exact independent claims from the issued patent (the fetched specification excerpts show concentration/LOD/LOQ limitations, e.g., assay LOD < 0.2 pg/mL and pg/mL concentration bands, but I did not have the claims page in evidence) and build grounds against those precise limitations, with careful attention to prior art dated before 2011-04-12 (the earliest provisional priority date) and to § 325(d) risk given the family's prosecution history.
5. Consider the parallel district-court leverage: In the Delaware case, Quanterix's infringement claims on the '092 were dismissed with prejudice and Fujirebio's DJ claims without prejudice — that asymmetry suggests Quanterix may be willing to resolve rather than litigate. If a demand letter cites the '803, test whether the same commercial dispute is covered by any resolution framework before committing to PTAB spend.

Inventors

Unusual pattern: the named inventors span an operating company (Quanterix) and an academic institution (Gothenburg). There is no evidence that any inventor departed Quanterix and triggered a portfolio fire-sale; the family has been continuously prosecuted and expanded by Quanterix through 2025–2026 (related continuations include US 11,275,092, US 10,393,759, and US 12,540,950, all assigned to Quanterix).

Original assignee

• Quanterix Corporation (Billerica, MA; NASDAQ: QTRX) — named on the issued patent and listed by Google Patents as the current assignee of record.
• Line of business: ultra-sensitive (Simoa®) single-molecule immunoassay instruments, assay kits, and a CLIA-certified laboratory service ("Accelerator"). The company ships products embodying this technology and performs the claimed tau-measurement methods commercially.
• Current status: operating public company. In March 2024 Quanterix publicly announced a licensing program for its tau-patent family (citing US 11,275,092) and stated that parties measuring tau on non-Quanterix platforms "risk infringement." This is an operating company engaged in commercial licensing/enforcement, not a licensing-only shell.

Assignment timeline

I could not pull the USPTO Assignment Center directly in this session (assignmentcenter.uspto.gov / assignment.uspto.gov were not reachable through the search tool). The data below is reconstructed from the USPTO assignment event embedded in Google Patents' legal-event feed for this patent, plus the Google Patents family record. Verify reel/frame details at the USPTO Assignment Center before relying on them.

• 2014-06-02 (executed) / recorded ~2022-02 (reel/frame consistent with the Feb 18, 2022 filing of continuation US 17/674,968) — Reel 058840/0248
  • Conveyance: Assignment of Assignor's Interest (inventors → company)
  • Assignor: David Wilson; John Henrik Zetterberg; Kaj Blennow; and Jeffrey D. Randall ("AND OTHERS")
  • Assignee: Quanterix Corporation (Massachusetts)
  • Correspondent: Not retrievable from the legal-event feed in this session; not verifiable without Assignment Center access.
  • Context: Original ownership transfer from the four inventors to their employer/licensee, executed at national-stage entry of PCT/US2012/033343 and re-recorded against the 2022 continuation file. This is the only assignment event shown for this patent number.

No post-issuance assignments, no mergers, no security agreements, no changes of name, and no transfers to any LLC or third party appear in the available record. The patent remains with the original operating assignee.

Timeline diagram

timeline
    title Ownership of US 12571803
    2011 : Priority provisional filed
    2012 : PCT filed by Quanterix
    2014 : Inventors execute assignment
    2022 : Continuation filed
         : Assignment recorded reel 058840 0248
    2026 : Patent granted March 10
         : Family litigation flagged

NPE / troll-pattern signals

1. Shell-entity transfer — not present. No transfer to any "IP / Holdings / Licensing" LLC. Owner of record is Quanterix Corporation, a public operating company with commercial products.
2. Known asserter in the chain — not present. Quanterix Corporation (NASDAQ: QTRX) does not appear on RPX/Unified Patents NPE directories; it is an operating diagnostics company. Google Patents flags "Family has litigation" via Darts-ip, but the asserting party per the record is the operating assignee itself.
3. Repeat correspondent across the chain — not present / unassessable. Only one recorded assignment exists (reel 058840/0248); the correspondent of record is not visible in the data retrieved, so no recurrence pattern can be established.
4. Cascading transfers — not present. No consecutive LLC-to-LLC assignments exist in the record.
5. Pre-litigation transfer — not present. The only assignment was recorded ~Feb 2022, years before the Mar 2026 grant and the family-litigation flag; no transfer was timed to establish standing for a suit on this patent.
6. Bankruptcy fire-sale — not present. Quanterix is not and has not been in bankruptcy; no insolvency-related patent sale is recorded.
7. Privateering — not present. No operating company handed this patent to an NPE to assert against competitors.
8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN.

Verdict

Operating-company assertion

The only recorded assignment (reel 058840/0248, executed 2014-06-02) moves the patent from the four inventors to Quanterix Corporation, a public (NASDAQ: QTRX) operating company that sells Simoa® instruments/kits and performs the claimed tau assays commercially. No shell LLC, NPE, cascading transfer, or bankruptcy event appears anywhere in the chain, and Quanterix has publicly stated (March 2024) that it will enforce its tau-patent family against parties measuring tau on competing platforms — consistent with an operating company asserting against market rivals rather than a patent troll. Caveats: this analysis relies on the USPTO assignment event as surfaced by Google Patents plus Quanterix's public filings, because the USPTO Assignment Center itself was not directly accessible in this session; the correspondent of record on reel 058840/0248 and the identity of the parties in the flagged family litigation should be confirmed directly.

Verification: search by patent number at https://assignment.uspto.gov/patent/index.html or https://assignmentcenter.uspto.gov/ (patent US12571803); legal events also indexed on Google Patents at https://patents.google.com/patent/[US12571803B2](/patent/US12571803B2)/en.

I'll start by searching for the patent record itself and its cited references.

Let me pull the patent's own front page and citation lists more directly.

Let me try to retrieve the patent's front-page citation list and the parent patent's cited documents.

Prior-Art Analysis — U.S. Patent No. 12,571,803 B2

Search conducted: USPTO-linked records (Google Patents/PubChem indexed USPTO data), PTAB petition record, and the parallel D. Del. / IPR family file. Date: April 26, 2026.

0. Threshold disclosure — read this before the reference list

I could not retrieve the (56) "References Cited" list printed on the face of U.S. 12,571,803 B2 itself. Specifically:

1. The authoritative full patent text supplied for this matter ends mid-Example 1 and contains no claims and no front-page citation list.
2. My searches returned the bibliographic record for US12571803B2 (Title: Methods of producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau protein; assignee Quanterix Corporation; App. 17/674,968; filed 2022-02-18; granted 2026-03-10; priority 2011-04-12) but not its (56) section.
3. My searches returned the (56) list for U.S. 11,275,092 B2 — the parent application (16/522,237) in the same continuation chain — and the prosecution/PTAB record for that family. This is the closest verified proxy, and I use it as such, clearly labeled as proxy data, not as confirmed citations on the '803.

Consequence for the § 102 mapping you asked for: because I do not have the '803's issued claim text, I cannot state "Reference X anticipates claim N." Any such statement would be fabricated. Instead, I map each reference to the claim category/limitation it could reach, and I identify the one limitation that defeats anticipation for each. I also flag that several references commonly listed on this family's face cannot be § 102 art at all against the '803 (date analysis in § 4). Treat the claim-level mapping as provisional pending retrieval of the '803 claim set from USPTO Patent Center (App. 17/674,968).

1. Reference set A — U.S. patent documents on the face of parent US 11,275,092 B2 (proxy for the '803's citation list)

Source: US11275092B2 front matter, p. 4 (https://patentimages.storage.googleapis.com/ab/6d/2e/1366e44f89aaee/US11275092.pdf). Not independently verified as printed on the '803.

Also on the '092 face per the Patent Owner Preliminary Response (IPR2025-01060): US 8,236,574 B2 (Duffy et al.); US 8,415,171 B2 (Rissin et al., Quanterix); US 8,460,878 / 8,460,879 / 8,492,098 (Walt et al., Tufts).

2. Reference set B — Non-patent literature relied on in the family prosecution

Source: the '092 face and the § 325(d) Patent Owner Preliminary Response in IPR2025-01060 (https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1557963](/patent/1557963)/). These are the references the Examiner actually used, and Quanterix's own POPR concedes their content.

3. The § 102 bottom line, limitation by limitation

Because the '803 issued with a "producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau" title, its independent claims almost certainly require, at minimum: (1) a bodily fluid sample (blood/plasma/serum, i.e., peripheral); (2) phosphorylated tau as the analyte; and (3) an analytically quantified amount, meaning an assay with a stated low LOD/LOQ (spec: LOD < about 0.2 pg/mL, down to about 0.02 pg/mL; LOQ ≤ about 0.04 pg/mL).

No single reference I located discloses all elements of the likely independent claims. That is the honest § 102 conclusion. The family's own prosecution history confirms this: the Examiner found every element except tau-in-blood in Duffy, and supplied that element from Quanterix 2010a — i.e., the Office itself treated this as a § 103 combination, not a § 102 anticipation.

4. Critical date analysis — which cited references can even be § 102 art

This is the part most likely to change your bottom line, and it runs against the challenger:

• The '803 is a continuation claiming benefit back to PCT/US2012/033343 (filed 2012-04-12) → U.S. Prov. 61/474,315 (filed 2011-04-12). Under pre-AIA practice, the § 102(b) critical date is one year before the earliest relied-upon filing date, i.e., on or about 2010-04-12.
• Consequence 1: The dozens of 2012–2020 Quanterix patents, publications, and press releases on this family's face (US 9,110,025; 9,551,663; 9,952,237; 10,393,759; 10,640,814; 10,725,032; US 2020/0123592; 2020/0271643; 2020/0393457; the 2012–2014 press releases; Chang 2012/2013) are not § 102 prior art against the '803. They appear on the face because of continuing-application IDS practice, not prior-art status.
• Consequence 2: The references that remain live are Hulstaert/WO 00/14546 (2000), US 2002/019016 A1 (2002), Duffy '407 and US 2010/0075862 (2010), Wunderlich (~2006), Todd (date unverified), and Quanterix 2010a (2010) — with the 2010-dated items landing in § 102(a) (post-2010-04-12) rather than § 102(b), which shifts the burden onto the applicant's invention date and opens Rule 131-style swearing-behind issues.
• Consequence 3 — the inverse risk. If the phosphorylated-tau limitations of the '803's claims lack written-description support in the 2011 provisional/PCT (which disclosed total tau, mentioning p-tau-181/p-tau-231 only in passing), the priority claim for those claims fails and the effective filing date becomes 2022-02-18. AIA § 102/§ 103 would then apply, and the entire 2012–2021 Quanterix corpus becomes available as prior art (subject to § 102(b)(1)(A) grace period — unavailable for 2012–2020 documents — and § 102(b)(2)(C) common ownership, which would not help for the published literature). This deserves independent, priority-of-invention-focused analysis; it is the highest-leverage validity question on this patent.

5. What I will not do, and what to verify next

I will not assign anticipation to specific claim numbers, because the '803's claims were not in the record available to me. Any claim-numbered § 102 assertion written without the claim text is fabrication.

Verify, in this order:

1. USPTO Patent Center, App. 17/674,968 → pull the issued claim set and the complete (56) list for 12,571,803 (not the '092). Everything above is a proxy until this is done.
2. Quanterix 2010a — identify the document the Examiner meant by that label and confirm it discloses tau in a blood sample. Quanterix's own POPR concedes the Examiner read it that way (Ex. 1002 at 498: "Quanterix 2010a 'explicitly teaches the assay can detect tau in a blood sample'").
3. Wunderlich and Todd — obtain full citations and confirm publication dates. Todd's "3-, 6-, 12-hour" teaching is a direct § 102(b) hit on any temporal limitation only if it pre-dates 2010-04-12.
4. Mörtberg — confirm the date. If it is the 2011 cardiac-arrest plasma-tau paper, it is outside § 102 for this patent and should not be counted as anticipatory art.
5. Ding — obtain the citation. It appears to be affirmative evidence of non-obviousness for the patent owner, and Quanterix will use it again.
6. Priority support for the p-tau limitations — see § 4, Consequence 3.

Sources: https://patents.google.com/patent/US12571803B2/en · https://patentimages.storage.googleapis.com/ab/6d/2e/1366e44f89aaee/US11275092.pdf · https://ptacts.uspto.gov/ptacts/public-informations/petitions/1557963/ · https://pubchem.ncbi.nlm.nih.gov/patent/US-2002019016-A1 · https://www.courtlistener.com/docket/70398011/fujirebio-diagnostics-inc-v-quanterix-corporation/

Obviousness Analysis of US 12571803 B2 Under 35 U.S.C. § 103

Preliminary note on the record available

The patent text supplied to me (Google Patents HTML rendered to text) was truncated mid-Example-1 and does not contain the claims, the examiner's "References Cited" list, or the "Non-Patent Literature" (NPL) entries that normally constitute the "Prior Art" section of a Google Patents page. Live-search results were therefore used to reconstruct the relevant art. Because I cannot verify the exact IDS/§ 103 grounds asserted against this specific grant, the analysis below identifies the art that is most plausibly combinable and the rationales an examiner or challenger would advance. Where I am inferring rather than confirming, I say so expressly.

What is confirmed about this patent:

• US 12571803 B2 issued 2026-03-10 from continuation App. 17/674,968, which descends from 16/522,237 → 15/269,142 → 14/111,326 → PCT/US2012/033343 (filed 2012-04-12) → provisional 61/474,315 (2011-04-12). Priority date: 2011-04-12.
• Family litigation exists (Darts-ip family 47009972).
• Family members include US 10,393,759 B2 and US 11,275,092 B2 ("Methods of determining a treatment protocol for and/or a prognosis of a patient's recovery from a brain injury") and US 12,540,950 B2 ("Methods of assaying phosphorylated tau protein in a sample").
• The specification's enabling technology is the Quanterix single-molecule array ("Simoa") digital immunoassay, which the patent describes as achieving tau LODs ≤ ~0.02 pg/mL and LOQs ≤ ~0.04 pg/mL in serum/plasma — roughly three orders of magnitude below conventional ELISA.

A D. Del. litigation document located via search confirms that during prosecution of a family application the Examiner applied pre-AIA § 103(a) rejections over "Duffy '407" in view of "Quanterix 2010a," further in view of "Wunderlich" and separately in view of "Mortberg," plus double-patenting rejections over US 10,393,759 B2. This tells us the art universe the Office was relying on: (i) the ultra-sensitive single-molecule array/digital ELISA patent literature (Duffy et al.), (ii) Quanterix's own 2010 published ultra-sensitive detection applications ("Quanterix 2010a" — consistent with US 2010/0075862 A1 et al., which are incorporated by reference in the specification itself), and (iii) clinical references on brain-injury biomarkers.

Representative claim scope to be tested

Although the granted claims were not reproduced in the text provided, the title ("Methods of producing bodily fluid samples containing an analytically quantified amount of phosphorylated tau protein") and the specification's Summary indicate the claim architecture centers on:

• A method of producing/obtaining a bodily fluid sample (blood, plasma, or serum) containing an analytically quantified amount of tau (including phosphorylated tau);
• by performing an assay having a very low LOD (< ~0.2 pg/mL) and/or LOQ (< ~0.04 pg/mL);
• optionally with capture on beads, spatial segregation into femtoliter-scale reaction vessels, enzymatic signal generation, and digital counting; and
• optionally tied to a brain-injury prognosis/treatment use (total AUC > ~800 pg·h/mL, secondary-peak AUC > ~500, CPC "good"/"poor" classification).

The obviousness analysis therefore turns on: (A) whether the ultra-sensitive assay format was known, (B) whether tau/p-tau as a brain-injury analyte was known, (C) whether combining them into a blood-based quantitative assay with those LOD/LOQ figures was within the grasp of a POSITA, and (D) whether the claimed prognosis/AUC uses add patentable weight.

Prior-art combinations that render the claims obvious

Combination 1: Ultra-sensitive single-molecule assay art (Duffy/Quanterix 2010) + known tau immunoassay reagents

References:

• Duffy '407 and Quanterix 2010a (single-molecule array / digital bead-based ELISA; e.g., the family of US 2010/0075862 A1, US 2010/0075355 A1, WO 2010/039179, and US 2011/0212848, all expressly incorporated in the specification at column 50-52 of the printed patent). These references disclose: capture objects (beads) with capture components, partitioning into femtoliter-scale wells at limiting dilution so each well holds 0 or 1 bead, enzyme-labeled detection antibodies, fluorogenic substrates, and Poisson/digital counting to quantify analyte at fg/mL to sub-pg/mL concentrations.
• Tau immunoassay reagents: by 2011 the INNOTEST hTau and phospho-tau (p-tau181/p-tau231) ELISAs and numerous anti-tau monoclonal antibody pairs (e.g., Tau-5, HT7, BT2, AT270, AT8) were long known for CSF measurement, as were the six tau isoforms (tau 23–tau 40) recited in the patent and the tau-441 epitope constructs.

Prima facie case: The specification's own "Exemplary Assay Methods and Systems" section confirms every element of the claimed assay protocol (bead capture, femtoliter-well arrays, enzymatic turnover, digital counting, background subtraction, Poisson adjustment) is taken from the incorporated Duffy/Quanterix references. The only arguably new variables are (i) applying that platform to tau/p-tau in blood products and (ii) reciting numeric LOD/LOQ performance attributes. Numeric sensitivity limits are inherent functional properties of an assay architecture, not inventive concepts: a POSITA implementing the known digital-ELISA on tau would predictably obtain LOD/LOQ in the sub-pg/mL range because the platform's published performance on other analytes was already at that level. "Producing a bodily fluid sample containing an analytically quantified amount of p-tau" merely describes the routine output of running a known ultra-sensitive assay on tau — an obvious application of a known platform to a known analyte (KSR v. Teleflex: predictable use of known techniques to improve a device; combination of prior-art elements according to known methods yielding predictable results).

Combination 2: + Tau as a peripheral biomarker of brain injury / hypoxia (clinical art)

References:

• Studies (pre-2011) reporting serum tau elevation after cardiac arrest, stroke, or TBI, and CSF tau correlation with outcome (the patent's own Background cites that "Tau is known to be elevated in the CSF of patients with neurodegenerative disease and head injuries" and discusses prior serum-tau studies in stroke patients with LOD ~60 pg/mL).
• Banyan Biomarkers' neurological-condition biomarker filings (e.g., the family ultimately published as US 12,601,749 B2 / US 11,994,522 B2, priority 2008-08-11), which broadly claimed detecting brain-injury biomarkers in blood.
• Zetterberg et al., PLoS One 2011 (same inventor group), showing time-dependent serum biomarker changes after cardiac arrest — demonstrating the clinical motivation.

Prima facie case: A POSITA seeking to diagnose/prognose hypoxic brain injury knew (1) tau is released from injured axons, (2) CSF tau tracks outcome, (3) the only barrier to peripheral measurement was assay sensitivity, and (4) the digital-ELISA platform removed that barrier. The motivation to combine is explicit and well-documented: replace the inadequate 60 pg/mL-LOD conventional immunoassay with the known higher-sensitivity format to measure tau in serum/plasma. Serial sampling over 48–72 hours and computing concentration-versus-time parameters (AUC, peak, slope) are routine pharmacokinetic/biomarker data-analysis techniques taught in standard texts and used in the very clinical literature the inventors cite.

Combination 3: + Phosphorylated tau (p-tau) — the narrowest claim limitation

References:

• Phospho-specific tau antibodies and p-tau CSF assays (p-tau181, p-tau231) were well known pre-2011, as acknowledged in the specification ("tau proteins (including phosphorylated taus such as p-tau-181 or p-tau-231)") and reflected in the classification search (G01N2333/4709).
• If the claims require measuring phosphorylated tau specifically, the only added step is swapping the detection antibody pair for a phospho-epitope-specific pair — a routine reagent substitution with no unexpected result, particularly given the specification itself teaches calibrating with phosphorylated tau constructs (SEQ ID NO: 2) and discloses both total-tau and p-tau detection as interchangeable embodiments.

Motivation-to-combine rationales

1. Known problem, known solution: The Background section candidly states the problem (blood tau "extremely low concentrations that are not reliably measurable by typical conventional immunoassays"). The Duffy/Quanterix digital-ELISA references were published solutions for exactly that problem — quantifying low-abundance proteins in complex fluids at fg/mL levels. A POSITA would combine them as a matter of course.
2. Same field / analogous art: Assay-format patents (Duffy/Quanterix) and clinical biomarker references (tau in brain injury) are both within the immunodiagnostics field; the references are mutually reinforcing, not teaching away.
3. Design choice, not invention: LOD/LOQ cutoffs (0.2 pg/mL, 0.04 pg/mL) track the inherent capabilities of the recited Simoa format. Choosing performance thresholds that the chosen platform already meets is an obvious optimization, not a patentable discovery (In re Applied Materials / In re Peterson: reciting a known result-effective variable).
4. Obvious to try: With a finite number of identified, predictable solutions (single-molecule arrays being the primary one for sub-pg/mL quantification), a POSITA had a reasonable expectation of success in detecting tau in serum. The data in the patent (detection in nearly all patients, with measurable kinetics) confirms the expectation was met.
5. Known analytical techniques: Serial sampling, AUC computation, ROC analysis, and CPC-outcome correlation are standard clinical-trial/biostatistics tools. The "second peak" analysis is a data-characterization choice from data the inventors themselves describe as "unexpected" — but unexpected data, without an unexpected technical result in the assay itself, generally cannot rebut obviousness of a method whose steps are conventional.

Counterpoints / why some claims may survive § 103

• Unexpected kinetic findings: The specification's Example 1 reports a bimodal tau-release profile and claims 100% sensitivity/91% specificity for the secondary-peak AUC in predicting 6-month CPC outcome. If the claims are construed to require selecting the secondary-peak AUC and correlating it to prognosis, an applicant could argue the bimodal kinetics were not predictable from the prior art (prior rat-TBI literature taught a monophasic peak and decline by ~6 h). A challenger would respond that this is a discovery about disease biology, not a new assay technology, and that § 103 protects methods, not data patterns.
• No explicit teaching of blood-based p-tau prognostication: If no single prior-art reference suggested quantifying phosphorylated tau in serum/plasma (as opposed to CSF) for prognosis after hypoxia, the combination becomes more attenuated, and an examiner might rely on improper hindsight. The Banyan and Zetterberg references narrow this gap but may not disclose p-tau-in-blood specifically.
• Secondary considerations: commercial success of the Simoa tau assay and long-felt need for non-invasive brain-injury prognostication (avoiding lumbar puncture and MRI cost) could be advanced, though these are fact-dependent and not in the record before me.

Bottom-line assessment

For the assay-format claims (producing a sample with an analytically quantified amount of tau/p-tau using an assay with LOD < 0.2 pg/mL), a strong prima facie § 103 case exists: Duffy '407 / Quanterix 2010a (digital single-molecule ELISA) combined with known tau/p-tau immunoassay reagents and the known clinical motivation to measure blood tau after brain injury would have been obvious to a POSITA, with a reasonable expectation of achieving exactly the recited sensitivity. The prognosis/AUC-based claims are weaker targets on the technology but stronger targets on the biology; their obviousness depends on claim construction (whether they require the specific bimodal/secondary-peak discovery) and on the weight given to the inventors' reported 100%/91% predictive performance.

Caveat on confidence: I could not access the actual claims or the examiner's cited-references list for US 12571803 B2 from the truncated text or from searches (search-step limit reached). The reference designations "Duffy '407," "Quanterix 2010a," "Wunderlich," and "Mortberg" are taken from a litigation document concerning a family application and are reported here as indicative, not as confirmed citations against this grant. A complete analysis should be re-run against the issued claims and the USPTO file wrapper (USPTO Patent Center for App. 17/674,968) before reliance.