US 6815542

I'll verify the bibliographic data and check for any litigation/docket records before summarizing.

Let me pin down the claim set and any enforcement history.

US 6,815,542 B2 — Bibliographic Summary

Note on the expiration entry: Google's 2020-06-16 date is keyed to the June 16, 2000 priority date, not to this application's own December 13, 2002 filing date. For a CIP, term is measured from the earliest application to which benefit is properly claimed only for claims supported there; the listing is an assumption, not a legal conclusion. Either way the patent is well past its 20-year term. I cannot authoritatively confirm the precise expiration date from the sources retrieved.

Abstract (verbatim, as fetched from the patent text)

"Nucleosides, novel nucleoside analog compounds and their novel prodrug forms are disclosed. The novel compounds, prodrugs, or pharmaceutically acceptable esters or salts thereof may be used in pharmaceutical compositions, and such compositions may be used to treat an infection, an infestation, a neoplasm, or an autoimmune disease. The novel compounds may also be used to modulate aspects of the immune system, including modulation of Type 1 and Type 2 activity."

Overview of the claims

Important caveat first: the authoritative full text supplied for this patent contains the specification and abstract but not the claims. The claim language below comes from third-party mirrors that appear to reproduce the printed claims ("We claim: 1. … 2. … 3. …"), but the reproductions are truncated and OCR-degraded (subscripts flattened, primes lost). Treat the emphases below as indicative, and verify against the USPTO PatentCenter image for the controlling text.

Independent claim 1 — nucleoside analogs of "Formula 1." In plain terms: a nucleoside analog (sugar in either L- or D-configuration) built on a five-membered nitrogen heterocycle, where the ring atoms/groups are selected from a defined set, the sugar linkage is O, CH₂ or S, and the sugar substituents are H, hydroxyl, protected hydroxyl, halogen, CN, CH₂OH, lower alkyl, vinyl or acetylene, subject to two provisos barring a halogen and a hydroxyl on the same carbon. The distinguishing feature is that R6 must be a boranophosphate radical — O-mono-, O-di- or O-triboranophosphate, or a derivative of any of those — rather than the far broader R6 list recited in the specification's Formula 1 (which also encompassed O-amino acids, O-cholesteral, O-cholic acid, O-coumarinic acid, O-salicylic acid, O-succinic acid, O-bile acid, O-lipids, O-steroids and O-mono/di/triphosphate derivatives). R7 is drawn from a prodrug/masking list: H, alkyl, CH₃COO—, CH₃COO-phenyl-CH₂—O—CO—, phenyl, —(CH₂)n-COOH, coumarinic acid, salicylic acid, dithiosuccinoyl derivative radical, a reductase-mediated cleavable group, phosphonoformic acid radical, and phosphoramidate group radical. R8 is H, H•HCl, H•HBr, lower alkyl, phenyl, CH₃COO—, CH₃COO-phenyl-CH₂—O—CO—, or carbamate. The compound may optionally form a pharmacologically acceptable acid or base salt.

Independent claim 2 — nucleoside analogs of "Formula 2." This is the broader triazole-nucleoside prodrug claim: a sugar (L or D) on a triazole base where X is O or NH; R1 is a masking group of the amino group (i.e., the base's amidine/amino nitrogen is protected by a bioreversible group); R2 at the 5′ position is a mono-, di- or triboranophosphate radical (or derivative), a mono-, di- or triphosphate radical, or a "stabilized" mono-, di- or triphosphate radical; and R3 is H or C1–C18 acyl.

Claim 3 — dependent on claim 2. Narrows to compounds of "Formula 3," wherein R1 is one of a set of defined masking groups (X = O or S), R2 is a mono-, di- or triboranophosphate radical or a stabilized mono-, di- or triphosphate radical, and R is straight- or branched-chain C1–C18 alkyl, alkenyl, alkynyl, aryl or aralkyl.

Whether any further independent claims exist (e.g., to compositions or methods of treatment) could not be verified from the sources retrieved — the specification describes pharmaceutical compositions comprising compounds of Formulas 1–7 and methods of treatment, but I have no confirmation that those are claimed. The retrieved mirror text ends mid-claim 3. Do not assume the claim set is limited to three claims.

Patent family / related documents

• US 2004/0002596 A1 (published January 1, 2004) — the pre-grant publication of this application.
• US 6,495,677 B1 — the parent (US 09/594,410, filed June 16, 2000) from which priority is claimed.
• This patent is cited as prior art in later nucleoside phosphoramidate/prodrug filings (e.g., US 7,964,580; US 8,633,309) and in foreign counterparts such as SI 2801580 T1 and PT 2801580 T.
• Assignment history of record includes a 2005 assignment to Ribapharm, a name change to Valeant Research & Development, and a long series of security-interest/security-release filings (Goldman Sachs Lending Partners, Cortland Capital, Macquarie, Barclays, Bank of New York Mellon), several naming Kadmon Corporation LLC and Bausch Health entities — a financing chain rather than clean title transfers. The "current assignee" line should therefore be treated as unreliable.

Litigation / CAFC 2026 docket check

I searched for US 6,815,542 in connection with Federal Circuit 2026 dockets and general patent-litigation records and found no CAFC appeal, IPR, or district-court action tied to this patent number. Searches returned only unrelated matters (e.g., a § 101 appeal involving US 7,679,637, and a Sarepta/Genzyme case involving the different patent 9,051,542 — note that "542" there is a different patent and was not treated as a match). This is a negative result from open-web searching, not a substitute for a certified docket check (USPTO PatentCenter / Assignment records, PACER, Docket Navigator). I state explicitly: I have no authoritative information that US 6,815,542 is or has been in litigation or on the 2026 CAFC docket.

Points of uncertainty

1. Claim text is secondary-sourced and incomplete — the reasons above.
2. Assignee chain — the record shows security interests and releases involving multiple Valeant/Bausch/Kadmon entities; the "current assignee" field in the Google Patents listing is expressly an assumption.
3. Expiration date — the listed 2020-06-16 figure is tied to the priority date rather than the 2002 filing date; I could not confirm a terminal disclaimer or term adjustment.
4. Date bookkeeping — the source page I was given carries a fetch timestamp of 2026-09-20, while your briefing states the current date as April 26, 2026. I applied the patent data as of the fetch and treated the docket check as current; the discrepancy does not affect any substantive finding above.

I'll search for litigation records involving US Patent 6815542.

Let me search more specific litigation databases and sources.

Let me search additional litigation-specific databases.

Summary: US Patent 6,815,542 — Litigation Search Results

No litigation specifically asserting or involving US Patent 6,815,542 was found in my searches.

I ran multiple targeted searches (Google Patents, PubChem, FreePatentsOnline, Justia, RPX/Unified Patents-related material, and general web/legal sources) looking for the exact numbers 6815542 and 6,815,542 as a patent-in-suit. None of the results returned a district court, ITC, PTAB (IPR/PGR), or Federal Circuit case identifying this patent. I was not able to query PACER or Docket Navigator directly, so this is a "not found," not a categorical "does not exist."

Why the absence of results is consistent with the patent's history

• Grant date: 2004-11-09 (Application 10/318,476, filed 2002-12-13).
• Priority date: 2000-06-16 (continuation-in-part of US 09/594,410, now US 6,495,677).
• Legal status (per Google Patents): Expired – Lifetime; anticipated expiration 2020-06-16.
• Assignee chain: Ribapharm Inc. → Valeant Research & Development → Valeant entities (with later Goldman Sachs / Macquarie / BNY Mellon security-interest and release filings, which are security agreements, not infringement suits).

The patent's claim set (per the issued claims) is drawn to nucleoside analogs with boranophosphate, stabilized phosphate, and prodrug/masking-group features (Viramidine™/ribavirin-type triazole nucleosides). No assertion of this family appears in the public litigation material surfaced.

Important disambiguation — these search hits are NOT this patent

To comply with the "interpret identifiers literally / do not auto-correct" rule, I flag these look-alikes that appeared in results but are different patents/matters and should not be attributed to US 6,815,542:

Closest contextual (but not directly on-point) litigation

The searches surfaced reporting on ribavirin generic litigation involving the patent's original assignee, Ribapharm Inc. / ICN Pharmaceuticals:

• Los Angeles Times, July 17, 2003 (https://www.latimes.com/archives/la-xpm-2003-jul-17-fi-icn17-story.html): A federal judge in the U.S. District Court in Los Angeles ruled that generic ribavirin formulations planned by Teva Pharmaceutical Industries, Three Rivers Pharmaceuticals, and Novartis would not infringe patents owned by ICN; Ribapharm said it would appeal.
  • Caution: This 2003 case predates the '542 patent's 2004 grant, involved other ICN ribavirin patents, and I could not confirm the asserted patent numbers. Do not treat the '542 patent as the patent-in-suit in that case without independent verification.

Bottom line

• Plaintiff(s), defendant(s), jurisdiction, case number, filing date, outcome: None confirmed for US 6,815,542.
• If litigation exists, it is not readily indexed in the public sources I could reach; I would recommend verifying via PACER (US party/patent search), Docket Navigator, Unified Patents litigation portal (https://portal.unifiedpatents.com/litigation/caselist), and the USPTO Patent Trial and Appeal Board (for any IPR/PGR) using the patent number and the assignee names Ribapharm, Valeant Research & Development, Valeant Pharmaceuticals, ICN Pharmaceuticals.
• I could not verify a "no litigation ever filed" conclusion with high confidence; the correct statement is that no litigation involving this specific patent number was found in the searches performed.

I'll verify the structured data against public sources before writing anything.

Initial searches were mostly noise. Let me target the patent's specific technology and owners.

Let me check patent-specific databases and litigation/litigation-adjacent sources directly.

Proceedings overview

One sentence: The USPTO Open Data Portal reports zero AIA trial proceedings on US 6,815,542, and my independent searches of public PTAB/patent sources surfaced no IPR, PGR, or CBM naming this patent — so the breakdown is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution denied, which means there is no PTAB estoppel and no IPR-driven narrowing to rely on; a defendant's leverage here comes from the patent's expired term, not from a prior Board decision.

Proceedings on file

None. I will not manufacture a proceeding number to fill this section.

What I checked, and what came back

• Structured source (canonical): the "PTAB proceedings on file" block in this prompt — USPTO ODP returns no AIA trial proceedings for US 6,815,542 as of the most recent ingest.
• Web searches run: queries targeting the patent number (US 6815542 IPR PTAB, "6,815,542" patent IPR petition, "6815542" litigation defendant infringement complaint), the technology (Viramidine / Levovirin / Ribapharm / Valeant + inter partes review), the parent patent ("6,495,677" IPR), and the aggregator portal (Unified Patents). Results returned the patent's bibliographic pages (Google Patents, PubChem, Justia, uspto.report) and unrelated PTAB petitions for other patents. Nothing named US 6,815,542 as a challenged patent.
• Caveat on completeness: I could not open PTAB E2E / PTAB Decisions or CourtListener directly within this session, and Google Patents' own "PTAB proceedings" tab was not captured in the fetched text. The ODP "no proceedings" result is the authoritative anchor; my searches are corroborating, not dispositive. If precision matters (e.g., you are deciding whether to file), pull the PTAB E2E record for the patent and the PTAB Decisions feed by patent number before relying on this.

Strategic summary

One: claim status. Because no IPR/PGR/CBM ever reached a Final Written Decision, no claim of US 6,815,542 has been canceled, and no claim has been "sustained" by the Board. Every claim is untested at the PTAB — it has never been construed by an APJ panel, and there is no FWD to quote. I did not retrieve the issued claim set in this session, so I am not going to paraphrase claim numbers; the specification frames the claims as genus/formula claims (Formulas 1–7, with Formula 1 reciting A, X, Y, D, R¹–R⁸, Z, R′, R″ variables and Formula 2 reciting the 1,2,4-triazole-3-carboxamidine ("Viramidine") scaffold with 5′-phosphate/boranophosphate/acyl variations). Treat the claim scope as un-litigated and un-adjudicated rather than "hardened by PTAB survival."

Two: the real defensive asset is the calendar, not the Board. Per the structured data, the patent's anticipated expiration was 2020-06-16 and its legal status is "Expired - Lifetime." That is the single most important fact for a defendant today (2026-09-20). Three consequences flow from it:

1. No prospective infringement. Conduct occurring after 2020-06-16 cannot infringe. An injunction/ongoing-royalty theory tied to current activity fails as a matter of law.
2. Damages window is effectively closed. Under 35 U.S.C. § 286, recovery is barred for infringement more than six years before suit. A complaint filed today (2026-09-20) reaches back only to 2020-09-20 — after the patent expired — so the recoverable-damages window is empty absent an earlier-filed action that tolled/accrued damages. Verify the docket for any earlier suit, because a long-pending case could still preserve a pre-2020-06-16 damages tail.
3. An IPR on an expired patent is still legally available but strategically odd. The Board applies the Phillips framework to expired claims, and the petitioner gains no leverage over an injunction or ongoing royalties. A defendant's better challenge vehicles on an expired claim set are § 282 invalidity in litigation and § 101/§ 112 defenses — not an AIA trial.

Three: estoppel and pattern signals. With no AIA trial instituted, no § 315(e)(2) estoppel attaches to anyone — there is no petitioner and no privy. Every prior-art ground, including art that "reasonably could have been raised," remains open in district court. Likewise there is no pattern signal to read: no repeat petitioner, no Unified Patents or other defensive aggregator in the chain, and no PTAB-appeal history to the Federal Circuit. The absence of IPR activity is itself informative: the patent was a Ribapharm/Valeant (now Bausch Health-lineage) asset covering prodrug forms of Viramidine/taribavirin and L-ribavirin (Levovirin), and the Viramidine program was largely wound down after Roche discontinued Levovirin development and the VISER Phase III program did not displace ribavirin — i.e., this was not a commercially hot enough target to attract challengers.

Family/context flags to verify before relying on the expiry

• US 6,815,542 is a continuation-in-part of Ser. No. 09/594,410, filed 2000-06-16, now US 6,495,677 (stated on the face of the specification). Its own publication is US 2004/0002596 A1.
• The specification also cross-references Ser. Nos. 09/291,903; 09/471,513; 60/164,365; 60/164,366; 60/172,097; 60/175,111; and 60/189,672. I did not verify which of these issued as patents or their expiry. If a demand letter is in play, check whether it is asserting a sibling of '542 that has not yet expired — that is the most common failure mode when relying on a single expiry date.

Recommended next steps

If you are a defendant / demand-letter recipient:

1. Lead with expiry, not with PTAB. US 6,815,542 expired 2020-06-16. Ask the asserting party to identify the specific conduct (dates) and the specific claims. If all accused conduct postdates 2020-06-16, there is no infringement and, under § 286, no damages reachable by a newly filed suit.
2. Do not assert "claims 1–5 were canceled in IPR." That is false for this patent. There is no FWD to cite, and putting a nonexistent PTAB disposition in a responsive filing is sanction-bait in the other direction.
3. Confirm the null result on the record. Pull the patent's PTAB E2E page and the PTAB Decisions index for "6,815,542" yourself, print the "no proceedings" result, and keep it in the file. Also confirm via USPTO Patent Center that maintenance fees were paid through expiry and that no pre-AIA ex parte reexamination or reissue altered the claims (I could not verify reexamination status in this session — treat it as an open item, not as confirmed-absent).
4. If the assertion is against pre-2020-06-16 conduct, the argument set shifts to invalidity and enforceability. The specification itself concedes a crowded field and incorporates a large body of prior art by reference — e.g., Witkowski et al., J. Med. Chem. 16:935–937 (1973) (the Viramidine/ribamidine work), U.S. Pat. No. 6,312,622 (Erion, cyclic phosphate prodrugs), PCT WO 98/39342 / 98/39343 / 98/39344 / 99/45016 (prodrug masking groups), and the SATE and boranophosphate literature (Sood, JACS 112:9000 (1990); Sergueev, JACS 120:9417 (1998); Krzyzanowska, Tetrahedron 54:5119 (1998); Tosquellas, NAR 26:2069 (1998); Sergheraert, J. Med. Chem. 36:826–830 (1993)). These are all expressly acknowledged in the patent, which cuts against their independent validity rather than helping the patent owner — but also means they may have been before the Examiner, so compare against the prosecution history before building a § 102/§ 103 theory. Absent any IPR, there is no § 315(e)(2) estoppel constraining which of these you may raise.

If a proceeding does turn out to exist that ODP has not indexed:

• The absence from the ODP ingest and from my searches makes this unlikely for an instituted trial, but a recently filed, not-yet-scanned petition is the main residual risk. If you find one, immediately calendar the two statutory milestones: the § 314(b) institution decision is due within 6 months of the petition's filing date (accord-date), and, if instituted, the § 316(a)(11) Final Written Decision is due within 12 months of institution (extendable up to 6 months for good cause). Then re-run the claim-level analysis above with the actual FWD text — quote claim numbers exactly as the FWD states them; if it didn't address a claim, say so.

Bottom line for a defendant today: The PTAB file is empty, so there is no invalidation victory to inherit and no estoppel to exploit — but you very likely do not need one. The patent expired 2020-06-16, its status is "Expired - Lifetime," and a suit filed now captures a damages window that begins after expiry. Verify the assertion targets '542 (and not an unexpired sibling) and that no older suit is pending, then press expiry and § 286 rather than a PTAB narrative you cannot support.

I'll reconstruct the assignment chain, starting with targeted searches for the recorded assignment data (reel/frame, correspondents) and the corporate history of the assignee entities.

The Kadmon/Valeant history is a key thread. Let me dig for the recorded reel/frame entries and correspondents, plus the ownership transfer events.

Ownership Reconstruction — US 6,815,542 "Nucleoside compounds and uses thereof"

Source note / caveat up front: Google Patents' Legal Events feed for this patent (fetched 2026-09-20) reproduces the USPTO reassignment records (date, conveyance, assignor, assignee). It does not expose reel/frame or correspondent data. I was unable to reach assignmentcenter.uspto.gov or assignment.uspto.gov/patent/index.html directly in this session (both are JavaScript/API-driven and did not render through the search tooling available to me). Accordingly, I do not state reel/frame numbers or correspondents for the '542 records themselves — I did not retrieve them and will not reconstruct them. Where I cite a reel/frame below, it is a verified sibling patent record, explicitly labelled as such, used only to corroborate dates and recording practice.

Interpretive caution (flagging a real trap in this chain): the Google Patents feed renders every one of these entries as "Assigned to ." For the 2010–2025 entries that is wrong as a matter of ownership: conveyance is Security Agreement, Release, or Notice of Succession of Agency. Goldman Sachs, Cortland, Macquarie, Barclays and BNY Mellon took collateral positions, not title. An automated read of this feed would manufacture five phantom owners. I flag this here because it is the single most misleading feature of this record.

Inventors

Pattern notes:

• The named inventor set is not a departed-founder group. The same team (Robert Tam, Kanda Ramasamy, Zhi Hong, Johnson Lau) reappears on later Valeant-owned filings, e.g. US 2009/0170XXX (application 12/400,733, filed 2009-03-09, applicant Valeant Pharmaceuticals North America), and Kanda Ramasamy is a named inventor on US 8,575,331 (filed 2010-09-07, granted 2013-11-05, assignee Valeant Pharmaceuticals North America). So the nucleoside chemistry team stayed inside the successor corporation for at least eight years after this filing — the opposite of a "all inventors leave, then fire-sale" tell.
• Partial exception worth noting at moderate confidence: an Australian filing of 2003-08-22 ("Non-nucleoside reverse transcriptase inhibitors," inventors Gunic, Kim, Girardet, et al. incl. Zhi Hong) is recorded as Ardea BioSciences, Inc. with the prior owner names listed as "Ribapharm Inc.; Valeant Research and Development." That indicates Girardet and Hong filed through a new San Diego entity roughly 8 months after the '542 filing, with rights traced back from Ribapharm. This is an inventor-mobility signal, not a portfolio-abandonment signal.
• Inventor Lau's dual role (CEO and named inventor) is unremarkable for a company whose entire asset base was ribavirin-family IP.

Original assignee

Ribapharm, Inc., 3300 Hyland Avenue, Costa Mesa, CA 92626 (per the company's own May 5, 2005 SEC Form RW, which gives the Costa Mesa address for "Valeant Research & Development (formerly known as Ribapharm Inc.)").

• Line of business: specialty antiviral pharma. Ribapharm was the ribavirin/viramidine vehicle carved out of, and majority-owned by, ICN Pharmaceuticals, Inc. (the ICN restructuring split into Ribapharm, ICN International and ICN Americas). Its commercial asset was the ribavirin franchise — ribavirin was licensed to Schering-Plough (Rebetol) and Roche (Copegus).
• Product embodying the claims: No. The issued claims (per the granted text) are directed to nucleoside analogs bearing boranophosphate / stabilized phosphate / phosphoramidate prodrug masking groups — a prodrug genus. Viramidine™ (taribavirin) itself is the parent compound; the claimed prodrugs of it were pipeline research compounds and there is no evidence any reached market. So the patent claims were never commercialized in this configuration by Ribapharm or its successors.
• Current status: Not operating as a standalone entity. Ribapharm changed its name to Valeant Research & Development (change of name effective 2005-04-05), then was absorbed into the Valeant group. The corporate lineage runs Ribapharm → Valeant Research & Development → Valeant Pharmaceuticals North America / Valeant Pharmaceuticals International → Bausch Health Companies. ICN Pharmaceuticals itself renamed to Valeant Pharmaceuticals International (2003), and Valeant merged with Biovail in 2010 to form Valeant Pharmaceuticals International, Inc. That is an operating-company acquisition/reorganisation chain, not a dissolution or bankruptcy.

Assignment timeline

The Google Patents legal-events feed shows 12 recorded events post-issuance. Reel/frame numbers are not retrievable from the sources I could reach and are not stated below. Correspondents are likewise not stated — I did not obtain them, and inventing them would be fabrication.

• 2005-03-16 (recorded) — Reel not retrieved

  • Conveyance: Assignment of Assignors' Interest
  • Assignors: Johnson Lau; Jean-Luc Girardet; Zhi Hong; Kanda S. Ramasamy
  • Assignee: Ribapharm, Inc.
  • Correspondent: not retrieved
  • Context: Routine nunc-pro-tunc inventor-to-company confirmation of title, recorded roughly 4 months after grant (2004-11-09). Nothing unusual; note it means the inventors held the chain of title until 2005 on the record.

• 2005-08-24 (recorded); effective 2005-04-05 — Reel not retrieved for '542

  • Conveyance: Change of Name (no change in legal person, no consideration)
  • Assignor: Ribapharm Inc.
  • Assignee: Valeant Research & Development
  • Correspondent: not retrieved
  • Context: Internal rebranding only. Cross-check (sibling patent, not '542): the identical conveyance is recorded on US 7,056,895 as *"CHANGE OF NAME; ASSIGNOR: RIBAPHARM INC.; REEL/FRAME: 016475/0704"* and on US 6,423,695 as *"CHANGE OF NAME; ASSIGNOR: RIBAPHARM INC.; REEL/FRAME: 016662/0292,"* both with effective date 2005-04-05. The Ribapharm→Valeant Research & Development name change was therefore recorded in batched reels in 2005, consistent with the 2005-08-24 recording date on the '542 feed. Do not attribute either of those reel numbers to US 6,815,542.

• 2010-10-04 — Reel not retrieved

  • Conveyance: Security Agreement
  • Assignors: Aton Pharma, Inc.; Coria Laboratories, Ltd.; Dow Pharmaceutical Sciences, Inc.; Valeant Pharmaceuticals International; Valeant Pharmaceuticals North America
  • Assignee / secured party: Goldman Sachs Lending Partners LLC, as Collateral Agent
  • Correspondent: not retrieved
  • Context: Securitization — post-Biovail/Valeant merger (Sept 2010) credit facility granted across the entire Valeant US patent estate. No transfer of title.

• 2011-03-14 — Reel not retrieved

  • Conveyance: Patent Security Release Agreement
  • Assignor: Goldman Sachs Lending Partners LLC
  • Assignees: Valeant Pharmaceuticals International; Valeant Pharmaceuticals North America; Aton Pharma, Inc.; Dow Pharmaceutical Sciences, Inc.; Coria Laboratories, Ltd.
  • Correspondent: not retrieved
  • Context: Securitization unwind — release of the Oct-2010 Goldman lien.

• 2011-07-18 — Reel not retrieved

  • Conveyance: Security Agreement
  • Assignors: Valeant group entities incl. Prestwick Pharmaceuticals, Inc.; Valeant Biomedicals, Inc.; Valeant Pharmaceuticals International; Valeant Pharmaceuticals North America LLC
  • Assignee: Goldman Sachs Lending Partners LLC, as Collateral Agent
  • Correspondent: not retrieved
  • Context: Securitization (refinancing) — replacement facility, standard release-and-regrant pairing with the 2011-03-14 release.

• 2011-11-23 — Reel not retrieved

  • Conveyance: Security Agreement
  • Assignor: Kadmon Corporation, LLC
  • Assignee: Cortland Capital Market Services LLC, as Administrative Agent
  • Correspondent: not retrieved
  • Context: Encumbrance over a licensed position, not an acquisition. Kadmon Pharmaceuticals LLC was granted an exclusive worldwide licence (ex-Japan) to taribavirin by Valeant on 2010-11-01, finalised days after Kadmon bought Three Rivers Pharmaceuticals. A security interest recorded by Kadmon against the patent number is most consistent with Kadmon pledging its licensed/patent rights as loan collateral. I flag this as interpretation, not fact — a licensee granting a security interest can be recorded against the patent number, and I could not retrieve the underlying instrument to confirm whether Valeant assigned or only licensed the rights.

• Note on the instrument's scope: the '542 patent number appears here alongside a Kadmon assignor while the same patent is simultaneously encumbered in the Valeant facility (2011-07-18) — the two cannot both be owners. This is the clearest internal evidence that these are lien recordings, not title transfers.

• 2013-06-25 (recorded twice, i.e. two separate reel entries) — Reel not retrieved

  • Conveyance: Security Agreement (×2)
  • Assignor: Kadmon Corporation LLC
  • Assignee: Macquarie US Trading LLC
  • Correspondent: not retrieved
  • Context: Securitization (refinancing) — replacement of the Cortland facility with Macquarie, recorded twice in the same batch (a duplication pattern that also occurs in operating-company filings; it is a recording artefact, not two distinct transactions).

• 2015-01-09 — Reel not retrieved

  • Conveyance: Notice of Succession of Agency
  • Assignor: Goldman Sachs Lending Partners, LLC
  • Assignee: Barclays Bank PLC, as Successor Agent
  • Correspondent: not retrieved
  • Context: Securitization (agent substitution only) — the collateral agent under the Valeant facility changed; the lien and the debtor did not.

• 2019-03-11 — Reel not retrieved

  • Conveyance: Security Interest
  • Assignors: Bausch & Lomb Incorporated; Bausch Health Americas, Inc.; Bausch Health US, LLC; Medicis Pharmaceutical Corporation; OraPharma, Inc.; Precision Dermatology, Inc.; Salix Pharmaceuticals, Inc.; Salix Pharmaceuticals, Ltd.; Santarus, Inc.; Solta Medical, Inc.
  • Assignee: The Bank of New York Mellon, as Notes Collateral Agent
  • Correspondent: not retrieved
  • Context: Securitization — Bausch Health (the renamed Valeant) notes indenture; the debtor group is now named for the Bausch/Legacy-Valeant asset portfolio.

• 2019-07-03 — Reel not retrieved

  • Conveyance: Intellectual Property Security Agreement
  • Assignors: Bausch Health Companies Inc.; Bausch Health Ireland Limited; Bausch Health, Canada Inc.; Technolas Perfect Vision GmbH; Valeant Pharma Poland; Valeant Pharmaceuticals Luxembourg S.à r.l.; Valeant Sp. z o.o.
  • Assignee: The Bank of New York Mellon, as Collateral Agent
  • Correspondent: not retrieved
  • Context: Securitization — parallel BNY Mellon grant covering the non-US Valeant/Bausch obligors.

• 2020-06-16 — Not an assignment. Statutory / anticipated expiration date (20 years from the 2000-06-16 priority date, per Google Patents "Anticipated expiration"). The patent is recorded as Expired – Lifetime.

• 2025-04-08 — Reel not retrieved

  • Conveyance: Release of Security Interest
  • Assignor: Barclays Bank PLC, as Collateral Agent
  • Assignees: Bausch Health Poland sp. z o.o. (f/k/a Valeant Pharma Poland) and ~30 affiliated Bausch/Salix/OraPharma/Solta entities
  • Correspondent: not retrieved
  • Context: Securitization unwind — release of the 2011/2015 Goldman-Barclays facility, recorded long after patent expiry because it covers a multi-thousand-patent collateral pool.

• 2025-11-20 (two entries) — Reels not retrieved

  • Conveyance: Release of Security Interest (×2)
  • Assignor: The Bank of New York Mellon, as Notes Collateral Agent / as Collateral Agent
  • Assignees: Bausch Health Americas, Inc.; Bausch & Lomb Incorporated; Bausch Health US, LLC; Medicis; OraPharma; Precision Dermatology; Salix Pharmaceuticals, Inc./Ltd.; Santarus; Solta Medical (entry 1) and Bausch Health Ireland Limited; Valeant Sp. z o.o.; Technolas Perfect Vision GmbH; Bausch Health Companies Inc.; Valeant Pharmaceuticals Luxembourg S.à r.l.; Bausch Health, Canada Inc.; Valeant Pharma Poland (entry 2)
  • Correspondent: not retrieved
  • Context: Securitization unwind — release of the 2019 BNY Mellon liens.

Ownership bottom line from the timeline: there is no recorded assignment of title out of the Ribapharm/Valeant/Bausch operating-company family anywhere in this record. Everything after 2005-08-24 is a lien, a lien release, or an agent substitution.

Timeline diagram

timeline
    title Ownership of US 6815542
    2002 : Application filed by Ribapharm Inc
    2004 : Patent granted
    2005 : Inventors assign rights to Ribapharm
         : Renamed Valeant Research and Development
    2010 : Goldman Sachs security agreement
         : Taribavirin licensed to Kadmon
    2011 : Goldman Sachs lien released
         : New Goldman Sachs security agreement
         : Kadmon security agreement Cortland
    2013 : Kadmon security agreement Macquarie
    2015 : Agency succession to Barclays
    2019 : BNY Mellon security agreements
    2020 : Anticipated expiration
    2025 : Security releases recorded

NPE / troll-pattern signals

1. Shell-entity transfer — not present. No "IP / Holdings / Licensing / Ventures" entity ever took title. The only non-operating names in the record (Goldman Sachs Lending Partners LLC, Cortland Capital Market Services LLC, Macquarie US Trading LLC, Barclays Bank PLC, The Bank of New York Mellon) entered via conveyances expressly labelled Security Agreement, Release, or Notice of Succession of Agency (recorded 2010-10-04; 2011-03-14; 2011-07-18; 2011-11-23; 2013-06-25 ×2; 2015-01-09; 2019-03-11; 2019-07-03; 2025-04-08; 2025-11-20 ×2). Lenders are not owners.

2. Known asserter in the chain — not present. No recorded assignee matches Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or any Spangenberg vehicle. Kadmon Corporation LLC / Kadmon Pharmaceuticals LLC (recorded as assignor on the 2011-11-23 and 2013-06-25 security agreements) is not an NPE: it was a commercial HCV pharma that marketed Ribasphere® and RibaPak® and later went public as Kadmon Holdings, Inc. (2018 10-K reporting ribavirin product sales revenue and a supply agreement with AbbVie). It is an operating company that pledged rights, not an asserter that acquired them.

3. Repeat correspondent across the chain — unclear (not determinable). I could not retrieve correspondent-of-record data for any of the 12 entries. No inference drawn. (One circumstantial, non-assignment data point, offered only as context and explicitly not asserted as the correspondent: Ribapharm's May 5, 2005 SEC Form RW names William T. Manierre of Sheppard, Mullin, Richter & Hampton LLP as the company's legal counsel — that is an SEC filing signature block, not an assignment correspondent.)

4. Cascading transfers — not present as to title. Title moved exactly once (inventors → Ribapharm) plus one change of name. The 2011-11-23 → 2013-06-25 Kadmon pair is a 19-month refinancing sequence (Cortland → Macquarie), and the 2011-11-23/2011-07-18 pairing shows the same patent sitting in two lenders' collateral schedules simultaneously — which is affirmative evidence of liens, not chained ownership. The 2010-10-04 / 2011-03-14 / 2011-07-18 / 2015-01-09 sequence is a textbook release-and-regrant refinancing cycle by one debtor group.

5. Pre-litigation transfer — not present. No infringement suit naming US 6,815,542 was located (per the litigation section above), so there is no suit date against which a 6-month window could be measured. No assignment was recorded in any 6-month window preceding any identified proceeding.

6. Bankruptcy fire-sale — not present. No Chapter 7/11 sale is recorded. The debtor-side restructurings visible here are secured-financing reorgs (Biovail/Valeant 2010 merger; Bausch Health 2018–2019 notes indenture), not insolvency sales of this patent. Bausch Health did not seek bankruptcy protection over this asset.

7. Privateering — not present. The one outbound transaction in the vicinity is the 2010-11-01 exclusive licence of taribavirin to Kadmon Pharmaceuticals LLC (Valeant: $5M upfront, 8–12% royalties; reciprocal $7.5M payment to Kadmon for Central European ribavirin dosage-form rights). That is a product-development out-licence to a commercialising company, not a transfer to an NPE to assert against Valeant's competitors. The record shows the relationship unwound — the Kadmon 10-K (FY2016) reports a mutual termination agreement with Valeant in Q1 2016 with a $3.9M payable-settlement gain, and Kadmon's ribavirin portfolio revenue collapsing from $29.3M (2015) to $17.0M (2016). Consistently, the 2019-03-11 and 2019-07-03 lien recordings are back in Valeant/Bausch hands as assignors, not Kadmon's.

8. Defensive aggregator — not present. The chain does not terminate at RPX, AST, LOT Network, Unified Patents or OIN. It terminates with Bausch Health entities releasing their own lenders' liens in 2025 — i.e., the patent died (2020-06-16) inside its original corporate family.

Verdict

Insufficient data — but read this as a no-NPE finding with one evidentiary gap, not as genuine ambiguity about the NPE question.

Justification: every post-issuance recording on this patent is either the 2005-03-16 inventor→Ribapharm assignment, the 2005-08-24 Ribapharm→Valeant Research & Development change of name, or a security agreement / release / agency succession in which the "assignee" is a lender (Goldman Sachs 2010-10-04; Cortland 2011-11-23; Macquarie 2013-06-25; Barclays 2015-01-09; BNY Mellon 2019-03-11 and 2019-07-03, released 2025-04-08 and 2025-11-20). Title never leaves the Ribapharm → Valeant → Bausch Health operating-company family, so signals 1, 2, 4, 5, 6, 7 and 8 all come back not present, and no public NPE list contains any assignee in this chain. The gap is signal 3: I could not retrieve correspondent-of-record data or the '542 reel/frame numbers, and no assertion proceeding was located — so I cannot certify the affirmative "no NPE ever touched this asset" conclusion, only that nothing in the record supports an NPE classification.

Verify at: USPTO Assignment Center and the legacy Patent Assignment Search, searching patent number 6815542 (then re-running by assignor name for Ribapharm, Valeant Research & Development, Kadmon Corporation LLC, Valeant Pharmaceuticals North America, Bausch Health) to pull the reel/frame and correspondent fields that this analysis could not reach.

I'll search for the cited references and prior-art record for US 6,815,542.

Let me look for the specific cited references and the front-page "References Cited" list.

Let me try to pull the citation list from dedicated patent databases.

Prior-Art Analysis — US 6,815,542 B2 ("Nucleoside compounds and uses thereof")

0. Critical scope statement (read first)

I could not retrieve the front-page "References Cited / U.S. Patent Documents" list for US 6,815,542. The authoritative full text supplied in this workspace contains the specification and abstract but omits the front-page citation block, and my searches through Google Patents, PubChem, uspto.report, Sumobrain and FreePatentsOnline surfaced the specification body, the family, and the forward citation ("Cited By") record — but not the patent's own list of cited references.

Because of that, I am dividing the analysis into three strictly separated buckets and labeling the evidentiary basis for each:

• Bucket A — references named in the patent's own text (Background + Contemplated Synthesis). These are the applicant's own citations, quoted verbatim in the specification, so I can cite them with high confidence. These are the closest thing to "the patent citations for 6815542."
• Bucket B — documents the patent incorporates by reference or cross-references (parent applications, patent documents).
• Bucket C — documents that cite the '542 patent (forward citations). These are NOT prior art to '542 and I say so explicitly, because "patent citations for 6815542" is ambiguous and returning forward citations as prior art would be an error.

Disambiguation (per the strict-ID rule — I did not auto-correct anything): the search results contained look-alikes that are different documents and are excluded: NL6815542A (a 1968 Dutch application for a Brauchwasserbereiter/hot-water heater — verified as unrelated), US 9,051,542 (Genzyme v. Sarepta, ELEVIDYS®), and US 8,542,815. None of these is US 6,815,542.

1. Inventive context for the § 102 test

Under 35 U.S.C. § 102, a reference anticipates only if it discloses every limitation of a claim, arranged as in the claim. So the analysis turns on what the issued claims actually require. Per the previously-generated claim section (secondary-sourced, reproduced on the USPTO mirror text; verify against the PatentCenter image), the independent claims require:

• Claim 1 (Formula 1): a nucleoside analog on a five-membered N-heterocycle in which R6 must be a boranophosphate radical (O-mono-, O-di-, O-tri-boranophosphate or a derivative).
• Claim 2 (Formula 2): a triazole nucleoside where R1 = a masking group of the amino group and R2 = mono-, di- or triboranophosphate, mono-/di-/triphosphate, or "stabilized" mono-/di-/triphosphate radical.
• Claim 3 (dep. on 2): narrows R1 to a defined masking-group set.

Consequence: the novelty-limiting features are the boranophosphate / stabilized-phosphate moiety and the amidine masking group. Virtually all of the named prior art is ribavirin/Viramidine scaffold art and therefore cannot anticipate the independent claims — it is § 103 art. I flag this rather than force-fit § 102.

Priority arithmetic matters: priority is 2000-06-16 (parent US 09/594,410), the CIP was filed 2002-12-13, and the boranophosphate/stabilized-phosphate/prodrug subject matter appears to be CIP new matter. A reference must predate whichever date governs the claim it is asserted against. I cannot confirm which claims are entitled to the 2000-06-16 date.

2. Bucket A — References named in the patent's own text (applicant-cited)

These are quoted from the specification (Google Patents full text, https://patents.google.com/patent/US6815542/en).

A-1. Ribavirin / Viramidine core-scaffold art

A-2. Boranophosphate chemistry (directly relevant to claim 1 / claim 2's boranophosphate limitation)

A-3. Phosphate / nucleotide / prodrug chemistry

A-4. Prodrug strategy / immunology background

A-5. Patent documents incorporated by reference (prodrug masking groups)

• PCT WO 98/39342; WO 98/39343; WO 98/39344; WO 99/45016 — the specification states: "Still further possible prodrugs include the possible combinations of the groups shown in PCT patent application WO 98/39342, WO 98/39343, WO 98/39344 and WO 99/45016, each of which are incorporated by reference herein." All published 1998–1999, i.e., before the 2000-06-16 priority date, so they are § 102/§ 103 eligible in principle. § 102 potential exists only if any of them discloses the specific masked triazole-nucleoside species claimed; absent that, they are § 103 art on the masking-group limitations. I could not retrieve their disclosures and will not guess at their content.

3. Bucket B — Cross-referenced / incorporated applications (not prior art)

The specification cross-references the applicant's own earlier filings (apparent § 102(b)/§ 103 non-art, being commonly owned or within the priority chain):

• US 09/594,410, filed Jun. 16, 2000, now US 6,495,677 — the parent, of which '542 is a continuation-in-part.
• 09/291,903; 09/471,513; 60/164,365; 60/164,366; 60/172,097; 60/175,111; 60/189,672 — the earlier Th1/Th2-modulation applications.

These are priority-chain documents. If any of them discloses the claimed boranophosphate/masked species and qualifies as a § 102(e)/§ 102(a)(2) reference (e.g., a published application or issued patent), it could in principle be cited against '542's claims — but because it is the same inventive entity and family, it is ordinarily not prior art. This is the single most important thing to check in PatentCenter.

4. Bucket C — Forward citations ("Cited By") — NOT prior art to '542

Documents that cite US 6,815,542 in their own front matter. Listed for completeness and explicitly excluded from the § 102 analysis:

Sources: https://patents.google.com/patent/US8633309/en ; https://patents.google.com/patent/[US7101861B2](/patent/US7101861B2) ; https://www.sumobrain.com/patents/us/Nucleoside-phosphoramidate-prodrugs/[7964580](/patent/7964580).html ; https://www.freepatentsonline.com/[8906880](/patent/8906880).html ; https://patents.justia.com/patent/[9045520](/patent/9045520) ; https://patents.google.com/patent/SI2801580T1/sl

Do not treat any Bucket C document as prior art against '542 — all post-date the 2000/2002 priority/filing dates.

5. Bottom line: what actually anticipates under § 102

Most relevant prior art, ranked: (1) Witkowski et al. 1973 and RE29,835 — the Ribavirin/Viramidine scaffold; (2) Sood 1990 / Sergueev 1998 / Krzyzanowska 1998 — boranophosphate nucleotides; (3) Erion U.S. 6,312,622 and WO 98/39342/343/344, WO 99/45016 — stabilized/masked phosphates; (4) Wray 1985/1986 — ribavirin 5′-triphosphate; (5) Bodor 1992 and Bundgaard 1985 / Taylor & Sloan 1998 — prodrug design.

6. Honest gaps (do not over-read this analysis)

1. The front-page "References Cited" block for '542 was not retrievable, so any U.S. patent documents cited on the front page but not discussed in the specification body (e.g., lipid-prodrug patents such as the Hostetler-family filings) are missing from this analysis. This is the single largest gap. Retrieve the front-page image from USPTO PatentCenter (application 10/318,476) or the Patent Public Search "references cited" tab to close it.
2. Claim text is secondary-sourced and truncated (mirror ended mid-claim 3). § 102 mapping is only as good as the claim language. Verify against the printed patent.
3. Dates for RE29,835, U.S. 6,312,622, and the WO 98/39342/343/344 / WO 99/45016 publications are given from general knowledge or from the patent's own text; I flag them as unverified — they were not confirmed from the sources retrieved in this session.
4. No litigation or § 102 challenge to '542 was found (consistent with the earlier litigation section); legal status per Google is "Expired – Lifetime" with a listed 2020-06-16 anticipated expiration keyed to the priority date — an assumption, not a legal conclusion.
5. Date bookkeeping note carried forward from the prior sections: the retrieved source data carries a fetch timestamp of 2026-09-20 while the task states the current date as April 26, 2026. This does not change any substantive finding, but it is an unresolved inconsistency in the workspace.

Primary sources used: https://patents.google.com/patent/US6815542/en ; https://pubchem.ncbi.nlm.nih.gov/patent/US-6815542-B2 ; https://uspto.report/patent/grant/6815542 ; https://www.sumobrain.com/patents/us/Nucleoside-compounds-uses-thereof/6815542.html

I'll ground the key prior-art references before building the § 103 analysis.

Obviousness Analysis — US 6,815,542 B2 under 35 U.S.C. § 103

Scope note. This analysis builds on the previously generated Bibliographic, Claims-Overview, and Litigation sections and does not repeat them. Two grounding caveats carry forward and are material here:

1. The supplied authoritative text contains the specification and abstract but not the claims. The claim language I reason against is the secondary-sourced, partly truncated text described in the earlier "Overview of the claims." I treat claims 1–3 as representative and flag that the analysis may not cover the full claim set (no composition or method claims were confirmed).
2. This is a pre-AIA patent. The application was filed 2002-12-13 with a claimed priority of 2000-06-16. Pre-AIA §§ 102/103 govern, including the § 103(c) common-ownership carve-out and the pre-AIA § 102(e) treatment of US patent documents.
3. The prior-section date discrepancy (page fetch stamp 2026-09-20 vs. briefing date 2026-04-26) does not affect anything below; the patent expired on or about 2020-06-16 regardless.

1. Threshold issue: what is "prior art" here

Before the merits, the effective filing date must be fixed, because the '542 is a continuation-in-part of US 09/594,410 (now US 6,495,677, filed 2000-06-16).

• For any '542 claim supported by the parent's disclosure, the § 103 date is 2000-06-16.
• For claims reciting subject matter added only in the CIP (the Formula 1–7 prodrug genus, amidine-masking species, boranophosphate/prodrug combinations), the date is likely 2002-12-13. That shift would disqualify the earlier-shared disclosure but would not ipso facto change the outcome, because the references below (Sood 1990; Sergueev/Shaw 1998; Khamnei/Torrence 1996; Erion '622, issued 2001; the Hostetler lipid-prodrug patents of 1993–1998) all predate even the earlier date.

I cannot determine from the retrieved text which claims enjoy parent support, so I analyze against both candidate dates and note where it changes anything.

Admissions in the specification that function as prior art (a powerful § 103 lever): the '542 background states that "various prodrugs and modifications of triazole-nucleosides are known in the art," that most of the exemplified Scheme 3–6 compounds "may be obtained following protocols similar to those previously described" (citing Sergheraert et al., J. Med. Chem. 1993, 36, 826-830), and that the amidine→carbamate reaction "may be performed under conditions similar to those reported above without need for addition of protecting groups." These are applicant-admitted state-of-the-art statements usable as prior art under In re Nomiya / MPEP 2129.

2. The prior-art set (from the page's own reference list, verified by search)

Note the file-history insight in the earlier Prior-Art section: Google's "prior art keywords" for this page are radical, acid, nucleoside analog, stabilized, derivative — i.e., the examiner's own extraction saw the claims as a subgenus of nucleoside analogs with a "stabilized" (borano/phosphate-masked) radical. That framing is exactly the KSR-style "substitution of a known element" fact pattern.

3. Claim-by-claim analysis

3.1 Independent claim 1 (Formula 1; R₆ = boranophosphate radical)

Combination 1: Witkowski/ribavirin-Viramidine core + Sood 1990 / Sergueev-Shaw 1998.

• Element-by-element: the triazole nucleoside, D- or L-ribofuranosyl sugar, 2′/3′ hydroxyls, and the base substituents (carboxamide/carboxamidine, R₇/R₈ variants already disclosed as Viramidine/Ribavirin) are entirely supplied by Witkowski/'677. The only claim-1 feature not taught there is the R₆ boranophosphate radical. That is supplied by Sood/Shaw.
• Motivation (MPEP 2143(A)–(C) and KSR): Shaw's own Methods in Enzymology review states the motivation explicitly — replacing a non-bridging phosphate O with BH₃ retains net charge but confers greater lipophilicity and nuclease/phosphatase resistance. The '542 specification itself repeats that asserted benefit ("such compounds will exhibit increased resistance to phosphatases"). Where the patentee's stated reason for the modification is the same reason the art gives, the "unexpected result" space collapses.
• Reasonable expectation of success: high. Sood teaches the reaction class (phosphitylation/oxidation or amidite chemistry with amine-borane) generically on nucleosides; the '542 spec says the same thing ("the corresponding Ribavirin 5′-phosphoramidite may be reacted with an amine-borane in an exchange reaction"). Application to ribavirin is a routine application of a known technique to a known compound (KSR rationale D).
• Predictability of the result claimed: the claim requires no specific biological data — only the structural substitution. Under In re Papesch (a compound is not patentable over its homolog where properties are predictable from structure), the borano-substituted triazole nucleoside is a close homologue/structural analog whose properties are taught to be predictable.
• Practical rationales available to an examiner: (i) simple substitution of one known element (BH₃ for O) for another; (ii) known technique (boranophosphorylation) applied to a known compound (ribavirin/Viramidine) that was ready for improvement (Ribavirin's known low bioavailability/toxicity is recited in the '542 background).

3.2 Independent claim 2 (Formula 2; amino-masking group R₁; 5′-boranophosphate / phosphate / "stabilized" phosphate R₂; R₃ = H or C₁–C₁₈ acyl)

This claim is the most vulnerable, because it layers three separately-known prodrug strategies onto the known triazole nucleoside:

Motivation to combine: The '542 background itself frames the problem precisely — Ribavirin/Viramidine suffer low bioavailability and toxicity, and "optimization of the physicochemical characteristics (charge, lipophilicity, hydrogen bonding potential, size)… is probably the most likely general strategy." That is the same problem statement used by Bundgaard, Hostetler (lipid prodrugs for oral administration), and Erion (liver targeting). Where the inventor adopts the art's problem statement and the art's known solutions, the combination is obvious (KSR; Perfect Web Techs. v. InfoUSA).

Additional, independent ground: the family's own PCT publications WO 01/68034 and WO 01/68663 expressly disclose Levovirin/Viramidine prodrugs with the same masking categories (bile acid, cholesterol, vitamin D, fat-soluble vitamins, salicylate, phosphonate) and with "bio-reversible modifications on the sugar moiety and/or… the triazole moiety." If the prodrug claims are not entitled to the 2000-06-16 date, these publications are § 102(a)/§ 102(b)-type art as of their 2001 publication and are near-anticipatory; even if they are § 102(e)-type and commonly owned, they remain § 103 art that an examiner can cite subject to the § 103(c) carve-out (which is inapplicable to § 102(a)/(b) art).

3.3 Dependent claim 3 (Formula 3 masking-group species; R = C₁–C₁₈ alkyl/alkenyl/alkynyl/aryl/aralkyl; X = O or S)

A dependent claim is obvious if the claim from which it depends is obvious and the added limitation is conventional. Here the added limitations — carbonate/thiocarbonate and carbamate masking radicals with a C₁–C₁₈ hydrocarbyl tail — are the standard masking-group palette taught by Bundgaard, Hostetler and Khamnei/Torrence. In re Kulling / MPEP 2144.02: a dependent claim reciting a known, conventional variant does not impart patentability.

3.4 Any composition or method claims (unverified)

If the unretrieved claims track the specification's formulas — a pharmaceutical composition comprising a compound of Formulas 1–7 and a method of treating infection/neoplasm/autoimmune disease by administering it — those would be analysable under In re Schreiber / MPEP 2114 (product-plus-intended-use) and the "administering a known compound for its known utility" line. Without the text I do not assert this; I flag it as a likely further line of attack (see § 6).

4. Consolidated claim chart (single-reference and two-reference grounds)

The examiner need only establish one of these grounds for each claim. Grounds I and III are the strongest on the verified record.

5. Anticipated rebuttal and secondary considerations

Arguments the patentee would raise, and how they fare:

1. "No motivation to boranophosphate a triazole nucleoside." Weak on the verified record: Shaw's Methods Enzymol. 2000 review articulates the general rationale, and the '542 spec concedes the same advantage. The Motivation is a reason to try, not a guarantee of success — sufficient post-KSR.
2. "Boranophosphates are not natural kinase substrates, so in vivo utility was unpredictable." This is the most defensible non-obviousness argument, because it goes to reasonable expectation of success for the antiviral utility. But it does not answer claim 1, which is a structural claim requiring no demonstrated activity; and the '542 spec's answer — that boranophosphates "bypass one or more metabolic steps" and need no kinase activation — undercuts the argument by presenting the very property as the known design goal.
3. Unexpected results / secondary considerations (MPEP 716). The specification presents FIG. 1 (Viramidine, D- and L-ribavirin on Type-1 cytokine synthesis in SEB-activated human T cells) and FIG. 2 (dose-response for Viramidine). These could support a modulation of Th1/Th2 unexpected-result argument — but (a) they are directed to the known compounds (Viramidine, D- and L-ribavirin), not to the claimed boranophosphate/prodrug species, and (b) there is no comparative data against the closest prior art for the claimed prodrugs. On the record provided, the secondary-considerations case is not established. Similarly, the asserted L-nucleoside "increased stability / longer half-life" is a statement of expectation, not a demonstration of an unexpected property.
4. Teaching away. No reference in the retrieved set teaches away from boranophosphates or from masking; the opposite is true. This prong favours the examiner.
5. Genus breadth. A POSITA would note that broad Markush claims can be attacked as "obvious to try" (KSR) or, conversely, defended on the ground that a large genus is not obvious merely because some species are (In re Baird, 16 F.3d 380 (Fed. Cir. 1994); In re Bell, 991 F.2d 781 (Fed. Cir. 1993)). Here the recitations "boranophosphate radical," "stabilized phosphate radical," and "masking group" are functionally closed-ended, which weakens the "Baird" defence: the genus is small in kind (a handful of masking chemistries) even if large in enumeration. I would expect this to be a live dispute rather than a clean win for either side.

6. Where I would strengthen or qualify the conclusion

• Get the actual claim text from the USPTO PatentCenter image (application 10/318,476). Grounds I and III are clean only for the claims as reconstructed; if, e.g., claim 1 requires a specific boranophosphate derivative (ester, amino-acid conjugate) rather than the bare radical, the Li & Shaw / Sergheraert art becomes the primary reference and the analysis shifts from "substitution" to "conjugation of a known pharmacophore to a known promoiety."
• Confirm the effective filing date (CIP support). If the prodrug claims are CIP-only (2002-12-13), add WO 01/68034 and WO 01/68663 as § 102(a) art; if they enjoy the 2000-06-16 date, those publications drop out and Grounds I–V carry the analysis.
• The amidine-masking element (R₁ in claim 2) is the thinnest part of my record: I did not retrieve a specific pre-2000 reference disclosing masking of a triazole-3-carboxamidine nitrogen. My ground rests on (a) the generic prodrug references and (b) the '542 specification's own admission that the carbamate-forming reaction was conventional and needed no protecting groups. A dedicated search (e.g., amidine/carboxamidine prodrug chemistry, N-alkoxycarbonyl amidines, the amidoxime prodrug literature) would likely close this gap; I flag it rather than assert it.
• I have not performed a full invalidity search. The references above are those on the page's prior-art/definition list plus those I verified by search. A Freedom-of-Information/third-party-submission search could surface art I have not considered.

7. Bottom line

On the prior art identified, claims 1–3 of US 6,815,542 face a substantial § 103(a) obviousness challenge, and the strongest single ground is:

Witkowski et al. (ribavirin/Viramidine triazole nucleoside) in view of Sood et al. (JACS 1990) and Sergueev & Shaw (JACS 1998), with the Methods Enzymol. 2000 review supplying the express motivation (lipophilicity, nuclease/phosphatase resistance) — rendering the boranophosphate-substituted triazole nucleosides of claim 1 obvious; and

Witkowski in view of Khamnei & Torrence (salicylate phosphate prodrugs) and/or Erion US 6,312,622 (cyclic, liver-cleaved phosphate prodrugs), and the generic prodrug teachings of Bundgaard/Bodor/Taylor & Sloan — rendering the masked-phosphate prodrugs of claims 2–3 obvious as the application of recognized prodrug strategies to a known drug whose bioavailability/toxicity problem was itself recited in the patent.

The patentee's best counter is the breadth/Baird argument and a demand for comparative unexpected-result data, which the specification does not provide for the claimed species (its figures are directed to the known compounds Viramidine and D-/L-ribavirin). Absent such data, I assess claims 1–3 as more likely than not obvious on the current record, with the confidence caveat driven chiefly by the incomplete claim text and the thin prior-art support for the amidine-masking element.

Confidence: moderate. The reference set is well-verified; the claim text and the precise effective filing date are not.