US 8906847

I'll search for authoritative records on this patent number before summarizing.

Let me check for litigation/PTAB/CAFC activity and the full claim set.

Let me pull the full claim set to identify independent claims accurately.

US Patent 8,906,847 — Analyst Summary

Verification note: I grounded this on the authoritative full text supplied in the prompt (Google Patents rendering), plus cross-checks against PubChem's patent record, FreePatentsOnline, and DrugPatentWatch. Where those secondary sources disagree or appear to contain transcription anomalies, I flag it explicitly rather than silently correcting.

1. Bibliographic data (as listed)

Notable commercial relevance: Third‑party Orange Book databases list US 8,906,847 as protecting YUVIWEL (navepegritide, NDA 219164) and YORVIPATH (palopegteriparatide, NDA 216490). This is consistent with the patent's role as a foundational Ascendis "TransCon" self‑cleaving linker filing, but I present the product linkage as a database assertion, not something I independently verified at the FDA.

2. Abstract (verbatim, from Google Patents)

"The present invention relates to a prodrug or a pharmaceutically acceptable salt thereof comprising a drug linker conjugate D‑L, wherein D is an amine containing biologically active moiety; and L is a non‑biologically active linker moiety L1 represented by formula (I), wherein the dashed line indicates the attachment to the amine of the biologically active moiety and wherein R1, R1a, R2, R2a, R3, R3a, X, X1, X2, X3 have the meaning as indicated in the description and the claims and wherein L1 is substituted with one to four groups L2‑Z and optionally further substituted, provided that the hydrogen marked with the asterisk in formula (I) is not replaced by a substituent; wherein L2 is a single chemical bond or a spacer; and Z is a carrier group. The invention also relates to A‑L, wherein A is a leaving group, pharmaceutical composition comprising said prodrugs and their use as medicaments."

3. Plain‑language overview of the technology

The patent claims a carrier‑linked prodrug in which a drug bearing a primary or secondary amine is hooked to a polymer carrier (PEG, hydrogel, protein, alkyl chain, etc.) through a linker that cuts itself loose after administration.

Mechanism, in words:

1. The linker is attached to the drug's nitrogen through a cleavable amide bond (the "prodrug bond") and to the carrier through a permanent bond.
2. The linker also contains an amine‑containing nucleophile plus a second, different amide bond whose nitrogen carries a hydrogen.
3. The nucleophile raises the nucleophilicity of that neighbouring amide nitrogen, which attacks the prodrug amide carbonyl, generating a cyclic imide (substituted succinimide or glutarimide) and ejecting the intact, unmodified drug. Cleavage is therefore intramolecular/autocatalytic and enzyme‑independent, which the specification presents as the fix for inter‑patient variability seen with esterase‑dependent prodrugs.

The specification reports half‑lives of hydrolysis in buffer at pH 7.4/37 °C of 1 h to 3 months, with buffer/plasma correlation, and a worked Exendin‑4 example showing in vitro/in vivo half‑lives of 120 h (13a) and 160 h (13b) against measured in vivo values of 115 h and 160 h (FIG. 3). This directly solves the stated problem of residual linker "handles" left on the released drug by earlier bicine‑ and maleamic‑acid‑based systems.

4. Independent claims

Caveat on completeness: The full text supplied in this session ends mid‑sentence in the description ("…and wherein R3aa, R3aa") and does not include the printed claim set. FreePatentsOnline's page confirms claims numbered at least into the high 30s (a listing of 10–15, 25–31, 34–37 appears), but the claim bodies were not retrievable in my searches. I cannot state the exact number or text of every independent claim with confidence.

Claim 1 (as rendered by DrugPatentWatch — closest available to the granted text)

A prodrug or pharmaceutically acceptable salt comprising a cleavable drug‑linker conjugate D‑L, configured so the D–L bond is cleaved after administration to release drug D‑H; wherein:

• ‑D is a nitrogen‑containing biologically active moiety;
• ‑L is a non‑biologically active linker moiety ‑L1 that comprises an amine‑containing nucleophile and is of formula (I);
• the dashed line is the attachment to the drug's nitrogen via an amide bond;
• X = C(R4R4a), N(R4), O, C(R4R4a)–C(R5R5a), C(R5R5a)–C(R4R4a), C(R4R4a)–N(R6), N(R6)–C(R4R4a), C(R4R4a)–O, or O–C(R4R4a);
• X1 = C or S(O); X2 = C(R7R7a) or C(R7R7a)–C(R8R8a); X3 = O, S, or N–CN;
• R1–R8a = H or C1‑4 alkyl, with optional pairings forming a chemical bond, C3‑7 cycloalkyl, 4–7‑membered heterocyclyl, or a ring A;
• optionally R3/R3a cyclise with their nitrogen into a 4–7‑membered heterocycle;
• A = phenyl, naphthyl, indenyl, indanyl, tetralinyl, C3‑10 cycloalkyl, 4–7‑membered heterocyclyl, or 9–11‑membered heterobicyclyl;
• L1 is substituted with one to four L2‑Z groups, where L2 is a single bond or a spacer and Z is a carrier group (with the proviso that the asterisk‑marked hydrogen is not replaced).

Transcription caution: the DrugPatentWatch rendering contains apparent OCR/typing anomalies (e.g., a duplicated "C(R4R4a)" and a "—C(R5R5a)C(R5R5a)—C(R4R4a)" fragment, and "R8" listed twice). The grant‑date wording should be confirmed against USPTO PatentCenter / the printed patent before being relied on verbatim.

Other independent claims — inferred from the specification, exact numbers unverified

The description recites four further statutory‑category inventions that in this family are typically claimed as separate independents. I flag these as inferred, not confirmed:

1. A prodrug precursor of formula Act‑L (specification renders it "A‑L"), where the linker carries a leaving/activating group rather than the drug. The specification defines Act as: chloride, bromide, fluoride, nitrophenoxy, imidazolyl, N‑hydroxysuccinimidyl, N‑hydroxybenzotriazolyl, N‑hydroxyazobenzotriazolyl, pentafluorophenoxy, 2‑thiooxo‑thiazolidinyl, or N‑hydroxysulfosuccinimidyl. This is the "reagent" claim used to capture manufacture/sale of the linker before conjugation.
2. A pharmaceutical composition comprising the prodrug (or a pharmaceutically acceptable salt) together with a pharmaceutically acceptable excipient.
3. The prodrug / composition for use as a medicament.
4. A method of treating, controlling, delaying or preventing one or more conditions in a mammalian patient by administering a therapeutically effective amount of the prodrug/composition/salt.

Claim 1 is the only independent claim I can attribute with reasonable confidence; treat items 2–4 as a roadmap of the disclosure rather than a verified claim listing.

5. Litigation / PTAB / CAFC check (as of 2026)

No 2026 Federal Circuit appeal decides US 8,906,847 itself. Here is what I found, with the distinctions made explicitly because the underlying disputes involve different patents:

• Ascendis Pharma A/S v. BioMarin Pharmaceutical Inc., No. 2026‑1026 (Fed. Cir. Mar. 26, 2026) — precedential opinion by Judge Stoll, joined by Lourie and Chen. Affirmed denial of a mandatory stay under 28 U.S.C. § 1659(a)(2), holding Ascendis could not reset the 30‑day clock by voluntarily dismissing and refiling its declaratory‑judgment action. This appeal concerns BioMarin's RE48,267 (CNP variants), not 8,906,847.
• N.D. Cal. Ascendis Pharma A/S v. BioMarin Pharmaceutical Inc., No. 4:25‑cv‑05696 (filed 2025‑07‑07, terminated 2025‑09‑09) — a third‑party litigation database lists the patents in that docket as 8,198,242; 8,906,847; and RE48,267, linking 8,906,847 to the navepegritide/YUVIWEL product page. I cannot confirm from the retrieved sources what role — if any — 8,906,847 played as an asserted or counterclaimed patent in that action; it may simply be a portfolio patent indexed to the same product/docket. This is an uncertainty, not a finding.
• ITC Inv. No. 337‑TA‑1447 — BioMarin's § 337 action against Ascendis over RE48,267; merits hearing April 20–24, 2026, ALJ initial determination due August 21, 2026, Commission target December 21, 2026. Again RE48,267, not 8,906,847.
• PGR2026‑00013, Ascendis Pharma A/S v. BioMarin Pharmaceutical Inc. — challenges BioMarin's US 12,233,106 B2, not 8,906,847.
• UPC CFI, Local Division Munich, 2 April 2025 — BioMarin v. Ascendis on EP 3 175 863 B1; unrelated to 8,906,847.

I found no IPR, PGR, or CBM petition against US 8,906,847, and no CAFC 2026 docket in which 8,906,847 is the patent on appeal. If such a proceeding exists, it is outside what my searches surfaced, and I would not assert its absence as fact.

6. Confirmed vs. uncertain — summary

High confidence: title, patent number, application number, filing/priority/issue dates, inventor list, assignee chain, abstract, the self‑immolative cyclic‑imide linker mechanism, the Act leaving‑group list, the GLP‑1/Exendin‑4 and hydrogel embodiments, and the 2031‑04‑30 adjusted expiration.

Moderate confidence: current assignee of record (Ascendis Pharma GmbH / Ascendis Pharma A/S — Google Patents reflects a 2018 chain of assignments to Ascendis Pharma GmbH and then Ascendis Pharma A/S, plus a 2023 confirmatory assignment); Orange Book listing for YUVIWEL/YORVIPATH.

Low confidence / explicitly flagged: the exact granted wording of claim 1 (secondary‑source transcription anomalies) and the complete set and numbering of independent claims. Anyone relying on claim scope for a freedom‑to‑operate, validity, or infringement purpose should pull the grant‑date claim set from USPTO PatentCenter (https://patents.google.com/patent/US8906847/en, USPTO PatentCenter for application 12/865,693) rather than the aggregator text.

Sources

• https://patents.google.com/patent/US8906847/en
• https://pubchem.ncbi.nlm.nih.gov/patent/US-8906847-B2
• https://www.freepatentsonline.com/8906847.html
• https://www.drugpatentwatch.com/p/patent-claims/8906847
• https://www.drugpatentwatch.com/p/patent/8906847
• https://www.drugpatentwatch.com/p/litigation/casename/index.php?query=Ascendis+Pharma+A%2FS+v.+Biomarin+Pharmaceutical+Inc.%7C4%3A25-cv-05696
• https://www.alston.com/en/insights/publications/2026/04/patent-case-summaries-march-27-2026
• http://business.cch.com/ipld/AscendisPharmaBiomarinPharmaceuticalFedCir20260326032726.pdf
• https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1558718](/patent/1558718)/download-documents

I'll research litigation involving US patent 8906847 across patent litigation databases.

Let me search litigation-specific databases for this patent.

Let me check patent litigation databases directly for this specific patent number.

Summary: No litigation found asserting US 8,906,847

Based on my searches of patent‐litigation resources (including the Unified Patents portal, Docket Alarm, RPX Insight, court records surfaced from PACER/archives, FreePatentsOnline, and DrugPatentWatch), I did not find any litigation (district court action, ITC investigation, or PTAB proceeding) that specifically asserts or challenges US Patent 8,906,847.

What I verified about the patent itself

• US 8,906,847 B2 – "Prodrug comprising a drug linker conjugate"
• Application US 12/865,693; filed 2009‑01‑30; priority 2008‑02‑01; granted 2014‑12‑09
• Inventors: Felix Cleemann, Ulrich Hersel, Silvia Kaden, Harald Rau, Thomas Wegge
• Assignee: Ascendis Pharma A/S (originally Ascendis Pharma AS; later assignments to Ascendis Pharma GmbH and Ascendis Pharma A/S)
• Status: Active, adjusted expiration 2031‑04‑30
• It is listed as an Orange Book patent covering Ascendis's Yuviwel® (navepegridite; TransCon CNP) product (GreyB/Pharsight; DrugPatentWatch).

Adjacent Ascendis litigation I did find (NOT involving US 8,906,847 — flagged so it is not mistaken for this patent)

These are real Ascendis disputes, but they concern different patents (not 8,906,847), so they do not qualify as "litigation involving US 8,906,847":

1. BioMarin Pharmaceutical Inc. v. Ascendis Pharma – ITC Inv. No. 337‑TA‑1447 (filed April 1, 2025) and related N.D. Cal. actions 4:25‑cv‑03302 and 4:25‑cv‑05696‑YGR. These assert U.S. Reissue Patent No. 48,267 (CNP variants), not 8,906,847. The N.D. Cal. case was stayed (mandatory § 1659/ITC stay). This concerns the same Ascendis product family (TransCon CNP/Yuviwel) but a different patent.

2. Kaleo Inc. v. Ascendis Pharma Endocrinology Inc. – 1:25‑cv‑01210 (D. Del.), concerning autoinjector patents (e.g., the '610 and '827 patents), not 8,906,847.

Note that DrugPatentWatch's page for patent 8,906,847 contains a generic hyperlink ("See patent lawsuits and PTAB cases for patent 8,906,847"), but I could not retrieve a populated case list, and no case was identified in any source reviewed.

Caveats / confidence

• I could not access the live Unified Patents litigation case-list query results filtered to this exact number, so my conclusion rests on the aggregated searches above.
• Because US 8,906,847 is Orange‑Book‑listed for a recently launched product (Yuviwel), future assertion is plausible; but as of the sources available to me, no such litigation is known.

Bottom line: No litigation is known involving US Patent 8,906,847. The Ascendis patent suits in the news (BioMarin/ITC and Kaleo) involve other patents. If you need an authoritative negative‑infringement‑style confirmation, the definitive check would be a PACER/Docket Alarm and Unified Patents portal query run directly against "8,906,847," which I recommend running to confirm this result.

I'll verify the structured data against live sources before drafting.

Proceedings overview

Total AIA trial proceedings on US 8906847: 0. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns no IPR, PGR, or CBM proceeding for this patent, and my independent web checks surfaced none either — so the breakdown by status is 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution-denied. Bottom-line defensive posture: this is not a "hardened-by-IPR" patent in the sense of surviving an AIA trial — it is an unchallenged patent. All claims as issued on 2014-12-09 are intact, there is no cancellation record, and there is therefore no IPR/estoppel foothold a defendant can borrow. The countervailing point is that the patent has also never been battle-tested at the Board, so nothing about claim 1's validity has been "blessed." Absence of IPR activity is a signal that assertion pressure to date has run through a different Ascendis patent family (see the RE'267 / CNP dispute below), not through the '847 prodrug claims.

No per-proceeding sections follow, because there are no proceedings to report. I will not manufacture proceeding numbers.

Verification trail (what I searched, and what I actually found)

One flagged lead, expressly not attributed to this patent: PTAB E2E shows a post-grant review petition docketed under petition ID 1558718 (PTAB E2E document download), in which the petitioner argues the Director should institute a PGR on a "'106 patent" claiming a method of treating skeletal dysplasia in patients "about 0 month to about 2 years old" by administering a CNP variant (vosoritide/Voxzogo art). That is the BioMarin–Ascendis CNP dispute, a different patent family from US 8906847 (whose claims are directed to a drug–linker conjugate prodrug and a leaving-group reagent A-L, not to CNP dosing methods). I could not confirm the challenged patent number or the party alignment from the retrieved text, so treat this strictly as a lead to pull from PTAB E2E by petition ID — do not represent it as a proceeding on the '847 patent.

Important limitation, stated plainly: I could not retrieve a PTAB E2E docket listing or a CAFC docket search for the '847 patent itself within my search budget. My "zero proceedings" conclusion rests on (a) the ODP structured block, which is the canonical source, and (b) negative web results. If you need a belt-and-suspenders confirmation, run the party-name search (Ascendis Pharma as patent owner) on PTAB E2E and on the CAFC docket for 2015–2026 before relying on it in a brief.

Strategic summary

Claim status: all claims UNTESTED — none canceled, none sustained. US 8906847 issued 2014-12-09 from application US12/865,693 (filed 2009-01-30, priority 2008-02-01) with a statutory/terminal posture of "Active, expires 2031-04-30" (adjusted expiration per the ODP record). Because no AIA trial was ever instituted, every claim — claim 1 (the D-L prodrug with the amine-containing nucleophile L¹ bearing one to four L²-Z carrier groups), the dependent claim set, and the Act-L reagent claims — stands on the presumption of validity under 35 U.S.C. § 282, un-narrowed by any Board cancellation. There is no FWD to cite, no certificate of cancellation, and no claim-level estoppel record. Practical consequence: if you receive a demand letter or an infringement contention citing the '847 patent, you cannot respond with "claim X is already dead." You must defeat it on your own merits.

Estoppel landscape: § 315(e)(2) estoppel is a nullity here — and that cuts for you. Because no IPR/PGR was ever filed on this patent, no petitioner or privy is estopped from raising any ground, and equally, you are not bound by anybody else's earlier art or claim-construction positions. Grounds you raised in a different matter (e.g., the BioMarin↔Ascendis RE'267/CNP litigation or ITC Investigation 337-TA-1447) are not automatically estopped as to the '847 patent, but you should assume Ascendis will argue issue-preclusion-style "you already had your shot" equities if you repackage the same references — note that BioMarin has made exactly that argument against Ascendis regarding the PTO reissue protest in the CNP fight. Available statutory windows if you do file: the '847 patent is pre-AIA (filed 2009-01-30), so PGR is unavailable (PGR reaches only first-inventor-to-file patents) and CBM is unavailable both substantively (this is a prodrug/linker chemistry patent, not a "covered business method," and the technological-invention exception would likely defeat eligibility) and temporally (the CBM transition program sunset on 2020-09-16). That leaves IPR under § 311 — § 102/§ 103 on patents and printed publications only — as the sole AIA vehicle, and a § 315(b) one-year clock that starts running only if and when Ascendis serves you with a complaint on this patent.

Pattern signals. Ascendis is a sophisticated, well-funded patent owner with an in-house IP strategy (over 465 granted patents in the portfolio as of 2025-12-31) and it litigates hard — it filed its own DJ action in N.D. Cal. (Ascendis Pharma A/S et al. v. BioMarin Pharmaceutical Inc., No. 4:25-cv-03302-YGR) rather than waiting to be sued, and it has pursued appeals in Europe (EPO opposition appeal on EP 3175863 B1). But the observable combat zone is the CNP/RE'267 family and its foreign counterparts (UPC Munich ACT_1613/2025, ITC 337-TA-1447, Danish Maritime and Commercial High Court BS-14603/2025-SHR) — not the TransCon '847 linker patent. No defensive aggregator (Unified Patents, RPX, etc.) appears anywhere in the chain for this patent. Note also that the '847 patent is Orange-Book-listed for both YUVIWEL (navepegritide) and YORVIPATH (palopegteriparatide), so if either product becomes the subject of an ANDA/505(b)(2)-style challenge or a biosimilar-style attack, IPR activity on this patent could appear quickly — its 2031-04-30 expiry makes it a live target for roughly the next five years.

Recommended next steps

• If you are a defendant facing assertion of US 8906847: there is no FWD to link to and no canceled claim to lean on. Build your invalidity case from scratch under § 102/§ 103 using the references already cited on the face of the patent and in its prosecution (the specification itself cites Sohma et al., J. Med. Chem. 46 (2003) 4124–4135; Garman & Kalindjan, FEBS Lett. 223 (1987) 361–365; WO-A 2004/108070 (bicine linkers); WO-A 2006/136586; Shan et al., J. Pharm. Sci. 86 (1997) 765–777; Gomes et al., Molecules 12 (2007) 2484–2506) — these are exactly the "cyclization-activated prodrug" teachings the patent distinguishes, and they are the natural § 103 backbone. Core claim 1 is a Markush-heavy genus with a functional "configured so that the bond … is cleaved" limitation, which is fertile ground for § 112 written-description/enablement and indefiniteness attacks (note that the corresponding CNP dispute shows Ascendis itself is a willing § 112 challenger when the shoe is on the other foot — BioMarin's brief recounts Ascendis's reissue protest raising "lack of adequate written description").
• Timing: no § 315(b) clock is running against you on this patent until service. If suit is filed, the IPR petition is due within one year of service; institution decision ~6 months from filing, FWD within 12 months of institution (35 U.S.C. § 316(a)(11)), with a possible 6-month extension for good cause.
• If you are monitoring rather than defending: set a docket watch on PTAB E2E for "Ascendis Pharma" as patent owner and on the CAFC docket. The Orange Book linkage to YUVIWEL and YORVIPATH means an IPR on the '847 patent post-dating this memo would not be a surprise; re-verify the ODP block before finalizing any opinion, and confirm the status of PTAB petition 1558718 directly in PTAB E2E to close out the one open lead identified above.
• Cite with care: no PTAB Final Written Decision, institution decision, settlement, or Federal Circuit appeal exists for US 8906847 as of 2026-09-29. Any brief or opinion letter stating otherwise would be incorrect.

I'll research the assignment record for US 8906847 across the sources available to me.

Let me try to pull the actual assignment records and any litigation history.

Let me try to locate the specific reel/frame records and correspondent data.

US 8,906,847 — Ownership & Assignment Analysis

Patent: US 8,906,847 B2 — "Prodrug comprising a drug linker conjugate"
Application: 12/865,693 · filed 2009-01-30 · priority 2008-02-01 · granted 2014-12-09 · adjusted expiry 2031-04-30.

Data-limitation note (read before the timeline). The USPTO Assignment Center (assignmentcenter.uspto.gov) and the legacy assignment.uspto.gov index are JavaScript/API-driven and could not be queried with the tooling available to me; my web queries returned no reel/frame strings for this patent. The assignment events below are reconstructed from the Google Patents "Legal Events" / assignment record for US 8,906,847 (which mirrors the Assignment Center dataset), plus corroborating litigation and Orange Book sources. I could not retrieve reel/frame numbers or the "correspondent of record" field, and I will not invent them. Every reel/frame and correspondent slot below is marked [not retrievable]. Treat those as verification tasks to run manually in Assignment Center.

Inventors

Unusual-pattern check: Not present. There is no evidence of the inventors departing the original assignee within 12 months of filing. All five executed assignments in favour of an Ascendis entity (2010, 2018, 2023), and at least Hersel, Rau and Cleemann continue to appear as inventors on later Ascendis filings into the 2019–2022 period — evidence of continued employment inside the Ascendis group, the opposite of a pre-fire-sale exodus. The only anomaly is the inconsistent assignee naming across recordings (AS vs. GmbH vs. A/S), discussed below — a chain-of-title hygiene issue, not an inventor-behaviour signal.

Original assignee

Ascendis Pharma AS / Ascendis Pharma A/S (Tuborg Boulevard 12, 2900 Hellerup, Denmark) — the Danish parent of the Ascendis Pharma group. The application-published front page (US 2011/0053848 A1) names Ascendis Pharma AS; the granted patent face and Google Patents "Current Assignee" name Ascendis Pharma AS / A/S alongside Ascendis Pharma GmbH.

• Primary line of business: clinical-stage-to-commercial biopharmaceutical company (TransCon prodrug technology platform). Publicly listed on Nasdaq: ASND.
• Does it ship a product embodying the claims? Yes — strongly supported. US 8,906,847 is listed among the Orange Book / drug-patent families covering Yorvipath (palopegteriparatide) and Yuviwel (navepegritide / TransCon CNP), both Ascendis commercial products (Yuviwel FDA-approved 2026-02-27). The patent claims the TransCon self-cleaving drug-linker conjugate — i.e. the core of Ascendis's marketed platform.
• Current status: Operating, going concern, publicly traded, with US subsidiaries (Ascendis Pharma, Inc., Delaware; Ascendis Pharma Growth Disorders A/S).

Assignment timeline

Reel/frame and correspondent-of-record were not retrievable through the sources available to me. Recording dates are as surfaced by the Google Patents legal-events mirror of the assignment record. Execution dates could not be confirmed and are therefore not asserted.

• executed [not retrievable] / recorded 2010-10-08 — Reel [not retrievable]/[not retrievable]

  • Conveyance: Assignment (Assignment of Assignors' Interest)
  • Assignor: Hersel, Ulrich; Kaden, Silvia; Rau, Harold; Cleeman, Felix; Wegge, Thomas (the named inventors)
  • Assignee: Ascendis Pharma AS
  • Correspondent: [not retrievable]. Note: the prosecution attorney of record on the patent face is Alston & Bird LLP (per the printed front page) — this is the patent-prosecution correspondent, which is not the same field as the assignment-recording correspondent and should not be conflated.
  • Context: Ordinary inventor-to-company assignment on a corporate-filed application — the founding link of the chain.

• executed [not retrievable] / recorded 2018-08-08 — Reel [not retrievable]/[not retrievable]

  • Conveyance: Assignment
  • Assignor: Kaden-Vagt, Silvia; Wegge, Thomas; Rau, Harald; Cleeman, Felix; Hersel, Ulrich (inventors)
  • Assignee: Ascendis Pharma GmbH
  • Correspondent: [not retrievable]
  • Context: Internal group chain-of-title correction / restructure — re-records the inventors' rights in favour of the German operating subsidiary. Contradicts the 2010 recording (which named Ascendis Pharma AS as assignee), so it reads as a corrective/confirmatory instrument rather than a new, arm's-length transfer.

• executed [not retrievable] / recorded 2018-08-08 — Reel [not retrievable]/[not retrievable]

  • Conveyance: Assignment
  • Assignor: Ascendis Pharma GmbH
  • Assignee: Ascendis Pharma A/S
  • Correspondent: [not retrievable]
  • Context: Internal reorg / upstream transfer of the German subsidiary's rights to the Danish parent (same-day as the preceding recording).

• executed [not retrievable] / recorded 2023-01-05 — Reel [not retrievable]/[not retrievable]

  • Conveyance: Confirmatory Assignment
  • Assignor: Kaden, Silvia; Cleemann, Felix; Hersel, Ulrich; Wegge, Thomas; Rau, Harald
  • Assignee: Ascendis Pharma A/S
  • Correspondent: [not retrievable]
  • Context: Chain-of-title cleanup consolidating full ownership in Ascendis Pharma A/S (note the corrected spelling "Cleemann" vs. "Cleeman" in 2010). Confirmatory instruments of this type are commonly executed to put the record owner in a clean position ahead of enforcement/licensing.

No security agreements, mergers, licenses, releases, or third-party transfers appear anywhere in the record. The chain never leaves the Ascendis Pharma corporate family.

Timeline diagram

timeline
    title Ownership of US 8906847
    2008 : Priority filing
    2009 : US application filed by Ascendis Pharma AS
    2011 : Application published
    2014 : Patent granted as US 8906847
    2018 : Inventors assign rights to Ascendis Pharma GmbH
         : GmbH assigns to Ascendis Pharma A S
    2023 : Confirmatory assignment to Ascendis Pharma A S
    2025 : DJ action against BioMarin in N D Cal
    2026 : Yuviwel approved in the US

NPE / troll-pattern signals

1. Shell-entity transfer — NOT PRESENT. Every assignee in the chain is an Ascendis Pharma group operating entity (recorded 2010-10-08, 2018-08-08 ×2, 2023-01-05). No "IP / Licensing / Holdings / Ventures" suffix, no registered-agent service address, no single-purpose LLC. The recorded addresses are corporate HQ addresses (Hellerup, DK / Heidelberg, DE).

2. Known asserter in the chain — NOT PRESENT. None of Acacia, Marathon, Intellectual Ventures, IPNav, Wi-LAN, Conversant/Mosaid, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation, or any Spangenberg entity appears at any recorded link. Assignee of record throughout is Ascendis Pharma AS / GmbH / A/S.

3. Repeat correspondent across the chain — UNCLEAR (not determinable). I could not retrieve the correspondent-of-record field for any of the four recordings, so no recurrence claim can be made. Two testable leads if you run this in Assignment Center manually: (a) Alston & Bird LLP appears on the patent face as attorney/agent of record (prosecution) — check whether the same firm is the recording correspondent on the 2014-era and 2018/2023 records; (b) Ascendis's trademark enforcement counsel has been Holland & Knight LLP (Daniel C. Neustadt / Paul F. Kilmer, per 2023 TTAB filings) — different field entirely, but useful for mapping Ascendis's outside-counsel relationships. Single or non-recurring appearances are expressly not treated as a signal here.

4. Cascading transfers — NOT PRESENT. The 2018 pair of recordings is a single formalized transfer path (inventors → GmbH → A/S) recorded on the same date, plus one later confirmatory assignment in 2023 — i.e. roughly one substantive event plus cleanup across 13 years, not a chain of unrelated LLCs passing the patent in <24-month hops.

5. Pre-litigation transfer — NOT PRESENT. The last recorded assignment (2023-01-05, confirmatory) predates the earliest litigation touching this patent (Ascendis Pharma A/S v. BioMarin Pharmaceutical Inc., N.D. Cal. 4:25-cv-05696, filed 2025-07-07) by roughly 30 months — well outside the 6-month window. Moreover the case is a declaratory-judgment action filed by Ascendis, not an NPE assertion campaign, and the related ITC action (337-TA-1447, filed 2025-04-01) was brought by BioMarin against Ascendis on BioMarin's RE48,267 — two operating companies in a two-way platform fight.

6. Bankruptcy fire-sale — NOT PRESENT. No Chapter 7/11 event, no trustee/sale conveyance, and no distressed-seller signature in the chain. Ascendis Pharma A/S is a solvent, Nasdaq-listed going concern (SEC-reporting; 10-K risk-disclosure language about enforcing its own IP confirms it holds and enforces this portfolio itself).

7. Privateering — NOT PRESENT. Ascendis never conveyed the patent out to an assertion vehicle. It retains sole ownership (post-2023) and litigates in its own name — the inverse of privateering, where the operating company hides behind an NPE.

8. Defensive aggregator (anti-NPE) — NOT PRESENT. The chain does not terminate at RPX, AST, LOT Network, Unified Patents, or OIN. It terminates at the original operating-company family.

Verdict

Operating-company assertion.

US 8,906,847 never left the Ascendis Pharma corporate family: recorded events are the initial inventor→Ascendis Pharma AS assignment (2010-10-08), an internal restructure recorded as 2018-08-08 (inventors→Ascendis Pharma GmbH, then GmbH→Ascendis Pharma A/S), and a confirmatory assignment to Ascendis Pharma A/S recorded 2023-01-05 — with no NPE, no security interest, and no third-party transfer at any link. The current assignee is a Nasdaq-listed operating biopharma (ASND) that ships products embodying the claims (Yorvipath/palopegteriparatide; Yuviwel/navepegritide, FDA-approved 2026-02-27) and is in litigation with a direct competitor, BioMarin (N.D. Cal. 4:25-cv-05696, filed 2025-07-07) — the textbook operating-company posture, and the precise opposite of every NPE signal tested.

Caveat on completeness: reel/frame numbers and the correspondent-of-record were not retrievable with my tools, and the execution dates are unknown. This verdict rests on the assignee identities and the corporate relationships between them, both of which are well-evidenced; the missing fields are unlikely to change it, since a repeat correspondent is only a signal when paired with shell recipients, and there are none here.

Verify at: https://assignmentcenter.uspto.gov/ — search by patent number 8,906,847 (also try application 12/865,693) and record the reel/frame + correspondent for the four events dated 2010-10-08, 2018-08-08 (×2), and 2023-01-05. Google Patents legal events for this patent: https://patents.google.com/patent/[US8906847B2](/patent/US8906847B2)/en

I'll research US patent 8906847 and its prior art citations.

Let me get the complete citation list from the patent's front page.

Let me get the precise front-page reference lists for US8906847.

Prior-Art Analysis — US Patent 8,906,847 B2

1. Patent Identification (interpreted literally)

Methodological caveat (stated up front): I could not directly query USPTO PatentCenter/PAIR in this session; the reference list below is drawn from the machine-readable citation tables for US 8,906,847 (PubChem patent record US-8906847-B2 and Google Patents/FreePatentsOnline), supplemented by the background-art discussion in the patent's own specification. The exact "[56] References Cited" front-page split between examiner-cited and applicant-cited documents is therefore reconstructed from those sources. Where I am not certain of a bibliographic detail I flag it. Anticipation conclusions are preliminary and based on the disclosures as summarized; a definitive § 102 analysis requires the full text of each reference.

2. References Cited on / Against US 8,906,847

The listed citations are a mix of patent documents and non-patent literature (NPL). Because the application has a 2008 priority / 2009 filing date (pre-AIA), all of these published documents (2000–2006) qualify as prior art under 35 U.S.C. § 102(b) (published more than one year before filing).

A. Patent / Published-Application References

1. WO 2004/108070 A2 — Enzon, Inc.

• Title: Releasable polymeric conjugates based on aliphatic biodegradable linkers
• Publication date: 16 Dec 2004 (applicant-cited)
• Description: Polymeric (PEG) conjugates of amine-containing drugs in which the drug is attached through a bicine-type (N,N-bis(2-hydroxyethyl)glycine) linker bearing two water-soluble polymer carriers. Release proceeds by cyclization-activation / cyclic imide formation at the drug–linker amide bond. This is the reference the US 8,906,847 specification explicitly criticizes as the "bicine" system.
• § 102 relevance: This is the closest structural/mechanistic reference. It discloses every functional element of the invention concept (carrier-linked prodrug; amine drug attached via amide; self-immolative cleavage by cyclic imide formation). It therefore potentially anticipates any claim drafted broadly enough to cover carrier-linked, imide-cyclization prodrugs generally. However, because the bicine linker is not the specific N,N′-biscarboxamide / amine-nucleophile linker of formula (I), a properly limited claim 1 (which requires the formula (I) linker with the mandatory –N(R3R3a) nucleophile and the secondary amide) is most likely not literally anticipated but is squarely § 103 obviousness art. I would treat it as the single most dangerous reference and would expect it to be asserted against the genus-level claims (claim 1 and its dependent claims to L1 as a genus) rather than against the specific species.

2. WO 2006/136586 A2 — Complex Biosystems / Ascendis lineage

• Title: Aliphatic prodrug linker (published 28 Dec 2006; applicant-cited)
• Description: A second-generation bicine/aliphatic prodrug-linker system (the "Another bicine-based system" cited in the US 8,906,847 background). Discloses carrier-linked prodrugs with self-cleavable aliphatic linkers and cyclic-imide-type release.
• § 102 relevance: Same analysis as WO 2004/108070 — potentially anticipatory only for broad genus claims; realistically § 103 art against claim 1 and the dependent claims defining linker L1 and the L2–Z carrier substitution.

3. WO 2006/003014 A2

• Publication date: 12 Jan 2006 (applicant- and search-cited)
• Description: Hydrogel-based (carrier) delivery systems. The US 8,906,847 specification expressly incorporates this document for its definition of "hydrogel."
• § 102 relevance: Relevant to the claims in which Z is a hydrogel (e.g., the hydrogel/GLP-1 embodiment claims and claim 31's "Z is a hydrogel," as visible in the claim text retrieved from Justia). It potentially anticipates the carrier/hydrogel subgenus claims if it discloses an amine drug amide-linked to a hydrogel via an analogous linker; otherwise it is § 103 art for the Z = hydrogel limitations.

4. WO 00/69900 A2 — applicant-cited; polymer–drug conjugate technology (published ~23 Nov 2000). General carrier-conjugate background; § 102 impact low (likely § 103 only, for the carrier-conjugate concept).

5. WO 2006/047451 A2 (published ~4 May 2006) — applicant-cited; prodrug/linker background.

6. US 2006/0115865 A1 (published ~1 Jun 2006; applicant- and search-cited) — polymeric prodrug/self-immolative linker background.

7. WO 2006/073396 A1 (published ~13 Jul 2006; search-cited) — prodrug-linker background.

8. WO 2006/115865 A2 (published ~2 Nov 2006; applicant-cited) — polymeric prodrug background.

(Items 4–8: I have only the citation data, not confirmed full texts. On the summaries available, they appear to be § 103 obviousness references supporting the general concept of polymer-linked, self-cleaving prodrugs rather than point-by-point § 102 anticipatory art. I flag this as lower-confidence.)

B. Non-Patent Literature (NPL)

9. Belikov, V. G., Farmatsevticheskaya Khimiya (Pharmaceutical Chemistry), Moscow: Vysshaya Shkola, 1993, Vol. 1, pp. 43–47.

• Description: A general Russian pharmaceutical-chemistry textbook. Cited almost certainly for basic prodrug/salt/physicochemical principles (supporting the pharmaceutically-acceptable-salt and prodrug definitions).
• § 102 relevance: No § 102 anticipation value — it is a general textbook, not enabling for the claimed linker. At most § 103 background.

10. Bernkop-Schnürch, A. (NPL; the citation string in the record is truncated as "Bernkop-Schnu-rch, 1…")

• Description: Author known for work on thiomers / mucoadhesive and polymeric drug-delivery chemistry; cited for general polymer-conjugate/prodrug background.
• § 102 relevance: No anticipation; general background/§ 103 at most. (I could not confirm the exact article title/volume from the record — flagged.)

C. Background Art Discussed in the Specification (not necessarily in [56], but citable art)

• Y. Sohma et al., J. Med. Chem. 2003, 46, 4124–4135 — ester-based prodrugs of KNI-727 using cyclization-activation by cyclic imide formation. The patent distinguishes this by moving from ester to amide prodrug bonds. § 102: does not anticipate the amide-linked claims; § 103: key art because it teaches the very mechanism (cyclic-imide cyclization) the claims exploit.
• A. J. Garman & S. B. Kalindjan, FEBS Lett. 1987, 223(2), 361–365 — PEG5000-maleic anhydride reversible amino-group modification (maleamic acid linkage; t½ ≈ 6.1 h at pH 7.4). Distinguished by the patent for pH instability. § 102: no anticipation.
• D. H. Lee et al., J. Control. Release 2003, 92, 291–299 — side reactions of amino-containing drugs with carrier degradation products. Background; no § 102 value.

3. Bottom Line on § 102 Anticipation

1. No cited reference literally anticipates the specific species claims (the compounds of formula (I) with the defined L1/L2–Z linker and exendin-4 / GLP-1 / hydrogel species, and claim 32's Act–L precursor), because none of the located references discloses the claimed N,N′-biscarboxamide linker with an –N(R3R3a) amine nucleophile and an N–H secondary amide in the exact structural form recited.
2. The best § 102 candidates for the broad/genus-level claims are WO 2004/108070 A2 (Enzon) and WO 2006/136586 A2, both of which disclose carrier-linked prodrugs that release an amine drug by cyclic imide cyclization. These are the references most likely to be argued as anticipating claim 1 (and its genus-dependent claims) — but on the disclosures as summarized they are more accurately characterized as § 103 obviousness art, since anticipation requires that a single reference disclose the formula (I) linker with all limitations, including the mandatory amine-nucleophile and secondary-amide features.
3. WO 2006/003014 A2 is the reference most relevant to the hydrogel-carrier limitations (Z = hydrogel) recited in, e.g., the hydrogel/GLP-1 embodiment claims and the hydrogel claim visible in the claim set.
4. The remaining patent documents and the two NPL items (Belikov; Bernkop-Schnürch) are general background references and do not, on their own, anticipate any claim.

Recommended next steps for a definitive analysis: (a) pull the certified "[56] References Cited" and any § 102/§ 103 rejections from the US 12/865,693 file wrapper in USPTO PatentCenter; (b) obtain full texts of WO 2004/108070 A2 and WO 2006/136586 A2 to element-map them against claim 1; and (c) confirm the exact bibliographic details of the two NPL citations, which are truncated in the public record.

Note: I have interpreted the patent number literally as US 8,906,847 and excluded unrelated results (e.g., the French application FR 8906847 and Brazilian BR 8906847, which share the numeric string but are different documents).

I'll gather the prior-art references cited in this patent's background and check the claim structure before building the § 103 analysis.

Let me check for any PTAB/litigation or EPO opposition decisions on this family, which often contain the parties' actual § 103 arguments.

Obviousness Analysis — U.S. Pat. No. 8,906,847 B2

"Prodrug comprising a drug linker conjugate" (Ascendis Pharma A/S)

Analyst's note / scope: This is a technical § 103 assessment based on the prior-art references identified on the patent page (background/description citations and the page's "Prior art keywords": group, alkyl, prodrug, mmol, poly). It is not a legal opinion. As an issued U.S. patent, US 8,906,847 enjoys the presumption of validity under 35 U.S.C. § 282, and invalidity must be proven by clear and convincing evidence. Because the application was filed 2009‑01‑30 with a 2008‑02‑01 priority date, pre‑AIA § 102/103 governs.

1. Bibliographic posture (grounding)

Sources: Google Patents US8906847B2; DrugPatentWatch claims page; DrugPatentWatch details page.

⚠️ Transcription caution (rule: interpret literally, do not auto-correct). The claim text circulating on DrugPatentWatch reproduces claim 1's X definition as "C(R4R4a), N(R4), O, C(R4R4a), —C(R5R5a)C(R5R5a)—C(R4R4a), C(R4R4a)—N(R6)…", whereas the patent specification defines "X is C(R4R4a); N(R4); O; C(R4R4a)—C(R5R5a); C(R5R5a)—C(R4R4a); …". I flag this as an apparent transcription/OCR discrepancy and do not resolve it; the granted printed claim controls.

2. Claim 1 decomposed into limitations

From the transcribed claim 1 (DrugPatentWatch; text also mirrored at FreePatentsOnline):

• (A) A prodrug (or salt) comprising a cleavable drug‑linker conjugate D‑L, "configured so that the bond between D and L is cleaved after administration so as to release a drug D‑H" (functional/result language).
• (B) D is a nitrogen‑containing biologically active moiety.
• (C) The dashed line = attachment to the nitrogen of D by forming an amide bond — i.e., the drug is attached through a cleavable amide.
• (D) L is a non‑biologically active linker L¹ which "comprises an amine‑containing nucleophile" and is a member of the Markush formula (I) (variables X = C(R⁴R⁴ᵃ)/N(R⁴)/O/…–C(R⁴R⁴ᵃ)–N(R⁶)–…; X¹ = C or S(O); X² = C(R⁷R⁷ᵃ) or C(R⁷R⁷ᵃ)–C(R⁸R⁸ᵃ); X³ = O, S or N–CN; R¹–R⁸ = H/C₁₋₄ alkyl; optional ring/cycloalkyl/heterocyclyl closures).
• (E) L¹ is substituted with one to four L²‑Z groups; L² = single bond or spacer; Z = carrier group.
• (F) Proviso: the asterisked hydrogen is not replaced.

The specification frames the invention as the N,N′‑biscarboxamide / cyclic‑imide self‑activation motif: "the presence of an amine‑containing nucleophile in the linker structure and another amide bond which is not the amide prodrug bond but an amide bond substituted with a hydrogen atom," where the permanent amide nitrogen attacks the prodrug amide carbonyl to generate a succinimide or glutarimide ring (FIG. 1). Dependent claims add carrier identities (Z = polymer ≥500 Da or C₈₋₁₈ alkyl; PEG 2,000–150,000 Da; hydrogels; proteins such as albumin/transferrin/Ig), drug lists, L² spacers (MW 14–750 g/mol), and a "prodrug precursor A‑L" with a leaving group Act (NHS, p‑nitrophenoxy, etc.).

3. The prior art of record (and its § 102 status)

All of the following predate 2008‑02‑01 and are § 102(b)/(a) art, fully usable in a § 103 combination (the pre‑AIA § 103(c) common‑ownership exclusion applies only to art that is prior art solely under § 102(e), (f) or (g) — it does not shelter § 102(b) publications, even the assignee's own).

Ancillary note on the family: the '847 linker is later described by Ascendis itself, alongside WO 2006/136586 A2, as one of the "reversible prodrug linker moieties … known in the art" (US 2022/0305136 A1), corroborating that REF‑1 and the '847 patent sit in one continuous technical lineage.

4. Element-by-element mapping and the three strongest combinations

4.1 Ref‑1 (WO 2006/136586) alone maps most of claim 1

REF‑1 therefore renders limitations (A)–(C) and the carrier/spacer/nucleophile architecture expressly disclosed. The question reduces to whether the specific linker scaffold (a succinimide/glutarimide‑forming N,N′‑biscarboxamide bearing the carrier) would have been obvious — and REF‑2 supplies exactly that.

4.2 Ground 1 — REF‑1 (WO 2006/136586) in view of REF‑2 (Sohma 2003), optionally + REF‑4 (Suggs 1997)

Why the combination is motivated:

1. Same field, same problem, same mechanism family. Both references are carrier/solubilizer‑linked prodrugs of amine‑containing drugs whose release is non‑enzymatic and driven by intramolecular nucleophilic attack forming a cyclic imide/amide. The '847 background itself concedes the shared field ("enzyme‑independent autocatalytic cleavage… is preferred").
2. The references articulate the exact deficiency the '847 patent claims to cure. REF‑1 and REF‑3 both criticize the bicine amide bond's slow hydrolysis (t½ > 3 h) and the risk of releasing a "linker‑modified prodrug intermediate" with altered PK/PD. That criticism is a design incentive to seek a different activating group — the classic KSR "identified problem in the same art."
3. REF‑2 supplies the alternative with a demonstrated, tunable mechanism. Sohma shows that an amide‑bearing spacer with a pendant amine nucleophile self‑cleaves via imide formation, regenerating the parent drug in vivo and in vitro, with t½ adjustable 4 min → 34 h by "attenuat[ing] the five‑membered ring intermediate formation." Ring‑size homologation (five‑ vs six‑membered imide; succinimide ↔ glutarimide) is explicitly identified as the rate‑governing variable — which is precisely what formula (I)'s X² = C(R⁷R⁷ᵃ) vs C(R⁷R⁷ᵃ)–C(R⁸R⁸ᵃ) encodes.
4. The skilled artisan's change is a known equivalent substitution. Sohma's prodrugs attach the self‑cleavable spacer to the drug through an ester to the drug's hydroxyl; REF‑1/REF‑3 teach that the same activating chemistry is used for drugs bearing an amine, through an amide. Where the drug has only an amine (no hydroxyl), using an amide is not merely convenient — it is the only available conjugation handle, and REF‑3/REF‑4 teach that amides alpha to an amine nucleophile are hydrolytically labile rather than "highly resistant."
5. Finite, predictable solution set. The artisan faces a small set of known activating groups (bicine-type N‑hydroxyethyl amine; Sohma-type imide-forming spacer; maleamic acid) and known rate‑tuning knobs (ring size, amine basicity). KSR's "finite number of identified, predictable solutions" rationale applies squarely.

Predicted claim chart (Ground 1): REF‑1 supplies (A), (B), (C), (E); REF‑2 supplies the L¹ scaffold of (D) (amine nucleophile + permanent amide + two carbonyls in α/β relationship → succinimide/glutarimide), the substitution of L²‑Z onto that scaffold being the routine placement of the polymer taught by REF‑1.

4.3 Ground 2 — REF‑2 (Sohma 2003) in view of REF‑3 (WO 2004/108070 / Greenwald 2004 / US 2004/0037802) and REF‑4 (Suggs 1997)

This ground is the most structurally precise. Paring the formulas:

• Sohma's motif: amine nucleophile — amide (N–H) — spacer — C(=O)—O–drug (ester to drug) — plus a small solubilizing amine terminus.
• '847 formula (I) motif: amine‑containing nucleophile — amide (N–H) — spacer (X/X¹/X²) — C(=X³)—N(drug) (amide to drug) — plus a carrier‑bearing group (L²‑Z).

The delta is two-fold: (i) the atom linking the electrophilic carbonyl to the drug (O → N, ester → amide); and (ii) the identity of the pendant terminus (small solubilizing amine → carrier‑bearing group). Both changes are directly taught:

• REF‑3/REF‑4 teach (i) by establishing that the drug's amine is the normal attachment point in carrier prodrugs and that the resultant amide is accelerated, not prohibited, by an N‑hydroxyethyl/amine neighbor group. REF‑3 states the conclusion in terms of the very compound class (bicine = "amino acid" amide) where "amide bonds are known to be highly resistant" is expressly qualified.
• REF‑1/REF‑3 teach (ii) by disclosing PEG carrier(s) conjugated to the linker and, in REF‑1, a permanent carrier‑linker bond so released drug is unmodified.
• REF‑5 provides the art‑recognized reason to move away from pH‑fragile reversible linkages (maleamic acid) toward a linker "which can be stored at lower pH" — a stated advantage of the '847 prodrugs.

Motivation, in one sentence: A POSA seeking a non‑enzymatically cleaving, carrier‑linked prodrug of an amine drug that releases the unmodified drug (the express goal of REF‑1 and REF‑3) would have been led by Sohma's demonstrated imide‑cyclization self‑cleavage — coupled with Greenwald/Suggs' teaching that the drug can be amide‑bound and that amide cleavage is neighbor‑group accelerated — to construct the succinimide/glutarimide‑forming, carrier‑substituted linker of formula (I), with a reasonable expectation of success because every functional element (cleavable amide, amine nucleophile, cyclization to imide, permanent carrier attachment) had been separately reduced to practice.

4.4 Ground 3 (dependent claims and secondary features)

5. Claim-by-claim obviousness assessment

6. Arguments the patentee would (and should) make

The obviousness case is not a foregone conclusion. The strongest rebuttals:

1. Unexpected result / teaching away. The specification asserts it "was surprisingly found, that the scope of cyclization‑activation by cyclic imide formation can be extended from ester to even carrier‑linked amide prodrugs, despite the much greater stability of the amide bond." REF‑3 says outright that "amide bonds are known to be highly resistant to hydrolysis." A POSA reading Sohma (ester‑only) + Greenwald (slow bicine amide, t½ > 3 h) would plausibly conclude amide‑linked, carrier‑bearing systems cleave too slowly to be therapeutically useful. This is a genuine "teaching away" argument, and it should be pressed.
2. Failure of the closest art. The bicine systems (REF‑1, REF‑3) suffer slow release and release of a linker‑modified intermediate; Garman's maleamic acid system is pH‑fragile. That is a documented long‑felt need with prior failures.
3. Unpredictability of the specific rates. Sohma demonstrates that t½ varies 500‑fold (4 min–34 h) across closely analogous structures. The patentee will argue that the rate behavior of any given linker within generic formula (I) could not be predicted, so the claimed genus is not "obvious to try" in any outcome‑predictable sense.
4. Excellent in vivo/in vitro correlation is asserted as a measured property (t½ 115 h/160 h in vivo vs. 120 h/160 h in vitro; FIG. 3), not merely an inherent expectation — arguably probative of unexpected results, though REF‑2's own in vivo/in vitro data weakens this.
5. Secondary considerations. Commercial success of YORVIPATH (approved 2024‑08‑09) and YUVIWEL (approved 2026‑02‑27) is substantial evidence of non‑obviousness if a nexus to the claimed linker can be shown — and given the drugs are marketed as the claimed conjugates ("a CNP moiety transiently conjugated to … mPEG via a proprietary TransCon® Linker," released by "auto‑cleavage … at physiological pH and temperature"), a nexus argument is strong. Note, however, that the products' FDA exclusivity and their separate CNP‑specific patent estate (US 10,835,578; 11,154,593; 11,311,604; etc.) must be disentangled from the '847 linker claims for nexus purposes.
6. Secondary reference date risk. REF‑1's priority is 2005‑06‑22 (pub. 2006‑12‑28) and REF‑3's is 2003‑05‑30; both are comfortably pre‑critical‑date, so the patentee cannot disqualify them on date grounds — but the patentee may argue REF‑1 is a bicine reference whose disclosure, fairly read, points only to bicine (and, indeed, REF‑1's own framing treats bicine as the solution, not the problem).

7. Bottom line

• Claim 1 and the preferred‑embodiment/carrier‑dependent claims are highly vulnerable under § 103, most plausibly via: (i) WO 2006/136586 A2 (REF‑1) in view of Sohma 2003 (REF‑2); or (ii) Sohma 2003 (REF‑2) in view of WO 2004/108070 / Greenwald 2004 / US 2004/0037802 (REF‑3) and Suggs 1997 (REF‑4); with Garman 1987 (REF‑5) and WO 2006/003014 (REF‑6) available for the pH‑stability and hydrogel limitations.
• The decisive issue will be whether the asserted "surprising" extension of imide‑cycization activation from an ester (Sohma) to a carrier‑linked amide (claim 1) is a patentable discovery, or merely the predictable application of a known self‑activation mechanism to the only available conjugation handle on an amine drug — where REF‑3/REF‑4 already teach that amine‑adjacent amides hydrolyze far faster than ordinary amides.
• Specific‑compound claims (e.g., the exendin‑4/BNP‑32 conjugates and claims reciting their measured release kinetics) are materially more defensible than the genus.

8. Explicit limitations of this analysis

• I could not verify any PTAB/IPR proceeding or invalidity judgment directed specifically at US 8,906,847. DrugPatentWatch's "See patent lawsuits and PTAB cases" link is a placeholder I could not open. The only litigation I located in the family's vicinity is the BioMarin v. Ascendis (ITC/CAFC) dispute, which concerns BioMarin's RE'267 patent and Ascendis's invalidity defenses against BioMarin — it is not a validity challenge to the '847 patent. (BioMarin brief, CAND 3:24?452409, Dkt. 75)
• I did not independently verify the full text/claims of WO 2005/099768 A2, which Ascendis's later filings list as another known reversible prodrug linker; if it predates 2008‑02‑01 (it appears to, publishing Oct. 2005) it would be an additional § 102(b) reference worth pulling. Content is unconfirmed here.
• The full set of USPTO‑cited references (the IDS/"Citations" section) was not retrievable from the fetched page; this analysis uses only the references expressly discussed in the patent's own background plus the mechanistic references cited within those documents (Suggs 1997, Greenwald 2004).
• I have applied the pre‑AIA framework; if any claim is entitled to a post‑AIA effective date, the § 102/103 framework and the treatment of the assignee's own WO 2006/136586 publication would need to be re‑run.