US 8598121

I'll search for information on US patent 8598121, including litigation activity.

Let me search for the claim text and any litigation involving this patent.

Let me retrieve the full claim set for US8598121.

US Patent 8,598,121 — Analyst Summary

Scope note / rule compliance: I ran targeted searches for the exact identifier 8598121 (and its legal-citation form "8,598,121"). I did not substitute results for any similar number. All identifiers below are transcribed literally from the sources. Where I lack authoritative text, I say so.

1. Bibliographic data (from the authoritative patent text)

2. Abstract / disclosure overview

The retrieved Google Patents record does not render the literal abstract paragraph in my excerpt, so I will not quote an "abstract" I cannot verify. What the record does state, in its own field definitions, is that the disclosure:

"relates, in general to variants of C-type natriuretic peptide (CNP), compositions comprising CNP variants, methods of making CNP variants, and methods of using CNP variants to treat disorders responsive to CNP, including but not limited to bone-related disorders such as skeletal dysplasias (e.g., achondroplasia) and vascular smooth muscle disorders."

The abstract concept classification confirms "achondroplasia" appears 16 times in abstract-classification tagging. Substantively, the specification is directed to CNP variant peptides engineered for (i) increased serum half-life via reduced NEP susceptibility and/or reduced NPR‑C (clearance receptor) affinity, (ii) retention of NPR‑B/GC‑B agonism (cGMP stimulation), and (iii) optional conjugation (PEG/PEO, amino-acid extensions, hydrophobic acids, bone-targeting moieties). Examples include CNP‑53/CNP‑38/CNP‑37/CNP‑34/CNP‑27 constructs, K4R substitutions, and N‑terminal PEGylated variants such as PEO24‑GANRR‑CNP22(K4R) (SEQ ID NO: 36).

3. Independent claims — plain language

Per the claim set as indexed (Espacenet claims view for US 8,598,121 B2, dated 2013‑12‑03):

Claim 1 — Composition of matter (the only "stand‑alone" claim):
A CNP variant selected from a closed group of specific sequences, namely Gly‑CNP53 (SEQ ID NO: 179), Pro‑CNP53 (SEQ ID NO: 185), Met‑CNP53 (SEQ ID NO: 190), and CNP‑53(M48N) (SEQ ID NO: 180). In plain terms: the claim covers only these four enumerated peptide sequences — it is a Markush-style list of full-length (~53‑residue) CNP variants, not a genus defined by formula.

Claim 5 — Method of treatment (incorporates claim 1):
A method of treating a bone-related disorder or skeletal dysplasia by administering a claim‑1 CNP variant, where the disorder is achondroplasia, hypochondroplasia, short stature, dwarfism, or homozygous achondroplasia.

Claim 13 — Method (incorporates claim 1):
A method of increasing long bone growth by administering a claim‑1 CNP variant, where administration increases long bone growth.

Claim 14 — Use/compound‑for‑use form (incorporates claim 1):
A claim‑1 CNP variant useful for increasing long bone growth or treating achondroplasia, hypochondroplasia, short stature, dwarfism, or homozygous achondroplasia.

Practical reading: all four independent claims are anchored to the same narrow four-sequence group of claim 1. Claims 5, 13 and 14 are functionally drafted method/use claims, so their effective scope is only as broad as the claim‑1 sequence list.

4. Litigation / CAFC 2026 docket check

• I searched for "8598121" combined with CAFC 2026 docket terms and found no Federal Circuit 2026 docket entry citing patent 8,598,121 specifically. I therefore cannot confirm any CAFC appeal involving the '121 patent; I would flag this as an open item rather than assert a negative as certain.
• The record does show "Family has litigation — First worldwide family litigation filed" (Darts‑IP family 43124672), and the same record shows the '121 patent as Ceased (consistent with supersession by reissue filings in the family).
• Searches for the family's litigation surfaced activity that names related but distinct patents, specifically RE48,267 and a '106 patent, in (a) an ITC investigation captioned around Certain Drug Products Containing C‑Type Natriuretic Peptide Variants, and (b) a PTAB post‑grant review (Ascendis petition; BioMarin opposing) plus district court proceedings (e.g., C.D. Cal. materials referencing BioMarin's RE'267 and Ascendis's "Yuviwel®" / napepegride product). One PTAB exhibit characterized RE48,267 as relating to "C‑type natriuretic peptide ('CNP') variants and methods of using CNP variants."
• Important caveat: these hits concern RE48,267 / the '106 patent, which are different patent numbers from 8,598,121. While they appear to sit in the same BioMarin CNP‑variant family, I cannot confirm from my sources whether RE48,267 is a direct reissue of 8,598,121 (the cited RE'267 claims run to at least claim 55, and the '106 patent is described as having a July 9, 2021 priority date — a different priority chain). Do not treat the RE'267 / '106 litigation as automatically being litigation on 8,598,121.

5. Explicit uncertainties

1. Literal abstract text — not present in my retrieved excerpt; I described the disclosure field rather than quoting an abstract.
2. Full dependent claim set — I have verbatim text for claims 1, 5, 13 and 14 only; I do not have the complete dependent-claim listing for the '121 patent.
3. CAFC 2026 — no confirmed docket item for 8,598,121 was located; absence of a hit is not proof of absence.
4. Reissue relationship — whether RE46,707 and/or RE48,267 are reissues of 8,598,121 (as opposed to continuations/reissues of sibling patents) is not confirmed by my sources.

Sources: Google Patents US8598121B2 (authoritative record; https://patents.google.com/patent/US8598121/en); Espacenet claims view for US8598121 B2 (2013‑12‑03); PTAB/PTAB-style petition documents referencing RE48,267 and the '106 patent; BioMarin investor communication re: vosoritide NDA.

I'll research litigation involving US patent 8598121. Let me run several targeted searches.

Let me dig deeper on whether '121 itself appears in any case dockets, and clarify its relationship to the reissue patents at issue.

Litigation search: US Patent 8,598,121 ("Variants of C-type natriuretic peptide")

Bottom line

I found no litigation — U.S. or foreign — in which US Patent No. 8,598,121 is identified by number as an asserted (or challenged) patent. Every case docket and ITC filing I could retrieve that concerns the BioMarin CNP-variant patent family names other family members (US RE48,267, US 8,198,242, US 8,906,847, and EP 3 175 863 B1) as the patents-in-suit. The '121 patent is a member of the same patent family but does not itself appear as a patent-in-suit in any source I retrieved.

Because I do not have direct PACER/Unified Patents/Darts-IP query access, I cannot rule out a short-lived or low-profile case; but on the record available, the answer is essentially "no litigation specifically on the '121 patent."

What the '121 patent is (for context)

• US 8,598,121 B2, "Variants of C-type natriuretic peptide," app. 13/466,672, filed 2012-05-08, granted 2013-12-03, priority 2009-05-20, assignee BioMarin Pharmaceutical Inc., legal status listed as Ceased, anticipated expiration 2030-05-20 (Google Patents: https://patents.google.com/patent/US8598121/en).
• Google Patents flags the family as "Family has litigation" (Darts-IP family 43124672) — but a family-level litigation flag does not mean the '121 patent itself was asserted.
• The '121 patent is in the same specification family cited in later BioMarin filings alongside US 8,198,242, US 8,377,884 and US 8,906,847.

Important caution (per your strict-ID rule): I am not asserting that RE48,267 is the reissue of the '121 patent. RE48,267 and RE46,707 both derive from CNP-variant continuations, but the sources I retrieved do not confirm the parent–reissue relationship to the '121 patent, so I treat that as unverified.

Closely related litigation on the same patent family (not the '121 patent)

These are the cases in which BioMarin's CNP-variant patent rights were actually asserted. I list them so you can see exactly which patent numbers were in play — none is 8,598,121.

Settlement (as reported, late Aug. 2026)

Per BioMarin's Form 8-K (event date Aug. 30, 2026) and analyst coverage:

• Ascendis pays BioMarin royalties on Yuviwel® (navepegritide/TransCon CNP): 20% of U.S. net sales; 18% of net sales in the EU, Brazil and South Korea, until May 2030, retroactive to first commercial sale.
• All pending BioMarin–Ascendis litigation (including ITC 337-TA-1447 and the N.D. Cal. DJ action) to be dismissed with prejudice; BioMarin grants Ascendis a non-exclusive worldwide license for all indications.

Explicit limitations

• No source I retrieved pleads, asserts, or adjudicates US 8,598,121 in any forum.
• I did not find any CAFC appeal specifically involving the '121 patent.
• The '121 patent's status is listed as Ceased, which is consistent with its subject matter having been pursued/continued through other family members and the reissue patents that become the enforcement vehicles.
• If you need a definitive "no" for PACER/Unified Patents/Darts-IP, that requires a direct database query I could not complete here; the conclusion above is based on retrieved public sources and should be treated as "no known litigation on the '121 patent number" rather than a certified negative search.

I'll start by verifying the structured data against what's live on the web, since the ODP block says no proceedings are indexed.

Now let me check whether any AIA proceeding targets '121 specifically, and clarify the related reissue/litigation picture.

Let me verify whether any AIA trial has targeted the reissues of '121, and check the status of the Ascendis PGR.

Proceedings overview

AIA trial count on US 8,598,121: ZERO. The structured PTAB block (USPTO ODP) returns no IPR, PGR, or CBM proceedings for this patent, my web search found no petition ever naming 8,598,121 (or either of its reissues) as the challenged patent, and the bottom-line defensive posture is therefore: the patent as an issued instrument has never been tested at the Board — but it no longer exists as an enforceable right, so the absence of IPRs is a footnote, not a defense. US 8,598,121 was surrendered in reissue and its live progeny (US RE46,707, then US RE48,267) is what a defendant will actually be sued on — and that reissue has been litigated, not IPR'd, and is now broadly licensed to the only competitor that had been fighting it.

Because there are no proceedings on '121 itself, the entries below are the adjacent proceedings a defendant needs in order to understand the real posture. Each is explicitly labeled as not an AIA trial on '121.

PGR2026-00013 — Ascendis Pharma A/S v. BioMarin Pharmaceutical Inc. (challenged patent: US 12,233,106 B2 — NOT '121)

• Type: Post-Grant Review (AIA trial)
• Filed: 2026 (docket number implies filing in the 2026 FY; exact filing date not confirmed in my sources)
• Status: Not stated in the structured data (this proceeding is not in the ODP list for '121, and its institution outcome was not returned in my searches). Do not treat this as institution or denial — it is unknown to me.
• Judge panel: Not public in the material I retrieved.
• Petition grounds: Challenged independent claim 1 and others of the '106 patent; asserted § 102/§ 103 over Bullens (Ex. 1008), Wendt-242 (Ex. 1023), Savarirayan (Ex. 1005), Högler, and Pauli, targeting CNP-variant compositions and methods of treating skeletal dysplasia in infants aged 0 to ~2 years. Statutory basis appears to be §§ 102/103 with an enablement/written-description overlay.
• Institution decision: Not located. What is on the public record is BioMarin's Patent Owner Preliminary Response, which asks the Director to deny institution on three independent grounds: (i) discretionary denial under Fintiv/Director-review precedent because Ascendis took a materially inconsistent claim construction of "CNP variant" in the co-pending ITC investigation versus the PGR; (ii) failure to name Bachem AG and Wacker Biotech GmbH as real parties in interest (the sole manufacturer/supplier of TransCon CNP and a supply-chain supplier); and (iii) § 325(d) because the Petition re-runs Bullens, Wendt-242, and Savarirayan already considered during prosecution without identifying Examiner error. Source: https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1558718](/patent/1558718)/download-documents
• Final Written Decision: None located. No FWD has issued on this docket in the material I retrieved.
• Settlement / termination: Likely mooted but unconfirmed. The parties announced a global settlement on 2026-08-31 (see below) covering "all pending lawsuits," but I could not confirm whether PGR2026-00013 was terminated as part of it. Flag this as an open item.
• Appeal: None found.
• Defensive value: This PGR is directed at a different, newer patent in the same CNP family, not at '121. Its value to a defendant is evidentiary: the Petition's prior-art set (Bullens, Wendt-242, Savarirayan, Högler, Pauli) is the art that a challenger would use against the CNP-variant family generally, and BioMarin's own preliminary response admits those references were before the Examiner — that is a § 325(d) headache for any future petitioner, but also a roadmap for a § 112/§ 102 attack in district court.

ITC Inv. No. 337-TA-1447 — Certain Drug Products Containing C-Type Natriuretic Peptide Variants (asserted patent: US RE48,267 — the reissue of '121; NOT an AIA trial)

• Type: Section 337 investigation (ITC), not a PTAB proceeding.
• Filed: Complaint filed 2025-04-02; instituted 2025-05-08 (90 Fed. Reg. 19532-33); amended 2025-09-17 to add Bachem AG (90 Fed. Reg. 44843-44).
• Status: Terminated by settlement (2026-08-31 announcement); hearing had already concluded and a final Commission determination was pending at the time of settlement.
• Panel: ITC ALJ (presiding ALJ not confirmed in my sources); no APJs.
• Asserted claims: Claims 15-20 and 31-48 of RE48,267 per the notice of investigation; the district court complaint also pleads claims 32, 34, 41, 43, 50 and 55.
• Respondents: Ascendis Pharma Inc., Ascendis Pharma A/S, Ascendis Pharma Growth Disorders A/S; later Wacker Biotech GmbH and Bachem AG.
• Accused product: TransCon CNP (navepegritide), now marketed as Yuviwel (FDA accelerated approval February 2026).
• Outcome: Settled — BioMarin grants Ascendis a non-exclusive worldwide license to the CNP patents; Ascendis pays 20% of US net sales and 18% of EU/Brazil/South Korea net sales from first commercial sale through 2030-05-20; all pending proceedings (ITC, N.D. Cal., Brazil, Denmark, Germany, South Korea) dismissed.
• Defensive value: This is the single most important fact for a defendant. The reissue of '121 was asserted in a full ITC trial, and the patent owner extracted a high-teens/20% royalty rather than a judgment on validity. The validity of RE48,267 was therefore never adjudicated — by the PTAB or the Commission — and the license does not exhaust rights as to third parties. There is no estoppel and no invalidity holding to borrow.

Reissue provenance of '121 — the fact that actually controls

US 8,598,121 issued 2013-12-03 and was surrendered in reissue. The chain, per the RE48,267 front page (USRE48267E, granted 2020-10-20):

• Application 14/604,262, filed 2015-01-23, "an application for the reissue of Pat. No. 8,598,121," matured as US RE46,707 (granted 2018-02-13).
• Application 15/646,822, filed 2017-07-11, a continuation of 14/604,262, matured as US RE48,267 (granted 2020-10-20), which recites "Reissue of: Patent No.: 8,598,121 / Issued: Dec. 3, 2013."
• Google Patents lists US 8,598,121 as legal status "Ceased" with anticipated expiration 2030-05-20 (https://patents.google.com/patent/US8598121/en).

Consequence: a demand letter or infringement theory citing "US 8,598,121" is citing a patent that no longer exists. Any assertion today must run through RE48,267 (or a newer family member such as US 12,233,106), whose claims are renumbered and whose text differs from the original '121 claims — the reissue has 62 claims, and the asserted sets (15-20, 31-48; 32, 34, 41, 43, 50, 55) do not map onto the original '121 claim numbering.

Related non-US / non-PTAB matters (context only)

• EP 3175863 B1 (foreign counterpart of RE48,267) — EPO opposition filed by Ascendis Pharma Growth Disorders A/S; Opposition Division upheld the patent in amended form on 2024-09-23; appeal pending before the Boards of Appeal. A parallel Danish Maritime & Commercial High Court invalidity action (Case No. BS-14603/2025-SHR) and a German infringement action (oral hearing scheduled 2026-03-18) were also filed. See EPO Board decision T 2413/60 (https://www.epo.org/boards-of-appeal/decisions/pdf/t241360eu1.pdf) — note the Board's construction that the CNP-38 claim is directed to CNP-38 itself and does not encompass longer peptides containing that sequence.
• N.D. Cal. Case No. 5:25-cv-03302 — Ascendis DJ action seeking a § 271(e)(1) safe-harbor ruling and an injunction against BioMarin's infringement statements regarding RE48,267 (filed April 2025; https://dockets.justia.com/docket/california/candce/5:2025cv03302/[447936](/patent/447936)).
• Reissue protest: BioMarin's own district court papers state Ascendis "lodged a failed protest against [RE48,267] at the Patent Office" and "tried to knock out the RE'267 patent during contested reissue proceedings, but failed." That was a 37 C.F.R. § 1.291 protest / contested reissue, not an AIA trial — do not cite it as a PTAB proceeding. Source: https://ia800400.us.archive.org/18/items/gov.uscourts.cand.[452409](/patent/452409)/gov.uscourts.cand.452409.75.2.pdf

Strategic summary

Claim status. For US 8,598,121 itself: no claim was ever canceled or sustained, because no AIA trial was ever instituted. The claims ceased to exist by operation of reissue (35 U.S.C. § 251), not by PTAB action. For the live right, RE48,267: the ITC instituted on claims 15-20 and 31-48; the district court pleads claims 32, 34, 41, 43, 50 and 55; and none of those claims has an adjudicated validity holding — the ITC case settled before final determination, and no IPR or PGR against RE48,267 was ever filed. In the EPO, EP 3175863 B1 was maintained only in amended form after opposition, and that decision is on appeal. So the honest map is: every asserted claim of the '121 family is untested in the US, and the patent's real vulnerability lies in the reissue itself and in § 112 (enablement/written description of the genus) and § 102/§ 103 art, not in any PTAB record.

Estoppel landscape. Because no IPR or PGR was instituted on 8,598,121, RE46,707, or RE48,267, § 315(e)(2) estoppel does not attach to anyone on this patent family. Ascendis is not estopped, and neither is any other party. A new defendant has the full IPR/PGR menu open — subject to the § 315(b) one-year bar running from service of an infringement complaint, and subject to General Plastic/follow-on petition discretion if it files after an earlier petitioner. The one piece of baggage is § 325(d): BioMarin's PGR2026-00013 preliminary response expressly argues that Bullens, Wendt-242, and Savarirayan were all before the Examiner, which means a petitioner relying on that same trio against a family member should expect a § 325(d) fight — and should plan to show material Examiner error or to build grounds on art that was not before the Office.

Pattern signals. No serial-filer pattern and no defensive aggregator (no Unified Patents, no RPX filing appears anywhere in this record). The only challenger in the chain is Ascendis Pharma A/S, and it has chosen the ITC, district court, the EPO, and one PGR — not a barrage of IPRs against '121. BioMarin's IPR history as petitioner (e.g., the Pompe/Duke IPRs, including IPR2013-00535 on U.S. 7,056,712) shows a patent owner that knows how to use the Board offensively, but it has never been on the receiving end of an institution decision for this family. The absence of IPRs here is explained almost entirely by the fact that the reissue application (filed 2015-01-23) and the licensing/settlement posture absorbed the fight outside the Board.

Recommended next steps

1. If you received a demand citing US 8,598,121, reject the premise. That patent was surrendered and reissued. Demand letters citing a surrendered patent, or citing original '121 claim numbers that no longer exist, have no enforcement basis. As of the settlement announced 2026-08-31, the only commercial CNP competitor in the US (Ascendis/Yuviwel) holds a worldwide non-exclusive license through 2030-05-20 — meaning BioMarin has already monetized this family at 18-20% of net sales, and the family's remaining life is short.
2. Confirm the true asserted patent before doing anything else. Pull the RE48,267 certified copy and map the asserted claims. Verify the reissue is not invalid under 35 U.S.C. § 251 — check for recapture (claims broadened relative to the surrendered '121 claims) and for whether any broadening claim was presented more than two years after the 2013-12-03 grant of '121. The reissue application was filed 2015-01-23, which is within two years of grant, so a § 251(d) broadening bar is unlikely but the recapture doctrine is very much in play if the reissue added claim scope the applicant gave up during original prosecution.
3. Absolute intervening rights (35 U.S.C. § 252). If the reissue claims are materially changed from the original '121 claims, a defendant who made, used, or imported the accused subject matter before the RE48,267 grant (2020-10-20) should evaluate absolute intervening rights as a complete defense for that pre-grant activity — and equitable intervening rights as a damages limitation thereafter.
4. Watch PGR2026-00013. It is on US 12,233,106, not '121, but it is the test case for the family's § 112 exposure. The institution decision (and whether the global settlement terminated it) is the single most informative document outstanding. Monitor PTAB E2E: https://ptacts.uspto.gov/ and the ITC docket: https://edis.usitc.gov/ (Inv. No. 337-TA-1447).
5. If you intend to file your own IPR/PGR, mind the § 315(b) clock if you have been served with a complaint, and expect a § 325(d) and Fintiv fight. Build the petition on art and argument outside the Bullens / Wendt-242 / Savarirayan / Högler / Pauli set that BioMarin has already characterized as Examiner-considered, and lead with enablement/written-description grounds that were not squarely presented.

Caveat on completeness: the structured ODP block is authoritative and says zero AIA proceedings on '121. My independent web searches are consistent with that. The PGR2026-00013 institution outcome, its panel, and whether it survived the 2026-08-31 settlement were not confirmed by any source I retrieved — I am flagging those as unknown rather than guessing, and they should be verified directly on PTAB E2E before any filing or reliance.

I'll research the assignment record and litigation history for US 8598121 using the available search tools.

I was able to reach Google Patents, litigation coverage, and secondary sources, but I could not retrieve reel/frame-level data from the USPTO Assignment Center (assignmentcenter.uspto.gov / assignment.uspto.gov) — the search returned no indexed assignment-record pages for this patent number. I will not invent reel/frame numbers or a correspondent. Everything below that is not independently verifiable is flagged as such.

Inventors

Per the issued patent record (US 13/466,672), the named inventors are:

• All seven appear to be BioMarin-affiliated. Inventor addresses of record for at least Wendt, Long and Aoyagi-Scharber are in the San Francisco Bay Area (e.g., an EPA/EP register listing gives BioMarin, 105 Digital Drive, Novato, CA 94949 as owner and lists these three inventors at Walnut Creek / San Ramon / Mill Valley addresses), consistent with employment at BioMarin's Novato/San Rafael operations.
• Pattern note: The application was filed 2012-05-08 and the assignment to BioMarin was recorded just six days later, 2012-05-14 — a routine "herewith" employment assignment, not a sign of inventor flight. I found no evidence of any inventor departing the assignee within 12 months of filing. I could not verify post-2012 employment for any inventor; treat that as "unclear," not as a finding.

Original assignee

BioMarin Pharmaceutical Inc. (original assignee and, per every source I could reach, the current owner).

• Business: Publicly traded rare-genetic-disease biopharmaceutical company (Nasdaq: BMRN); HQ San Rafael, CA; ~553,000 sq ft GMP manufacturing in Novato, CA.
• Product embodying the claims: Yes. BioMarin commercializes VOXZOGO® (vosoritide / BMN 111), a CNP analog for achondroplasia, FDA-approved 2021 — the first approved therapy for the condition. The CNP-variant estate to which US 8598121 belongs is the estate BioMarin has asserted to protect that product.
• Status: Operating company, not acquired, not dissolved, not in bankruptcy. It is actively litigating and licensing.
• Family: US 8598121 is a member of the BioMarin CNP/NPPC family (priority 2009-05-20; anticipated expiration 2030-05-20). Related family members include the pre-grant pub US 2012/0316114 A1 and reissues US RE46707 E1 and US RE48267 E1 (the "Ceased" status of the '121 patent reflects its replacement by reissue, not abandonment).

Assignment timeline

The only conveyance I can confirm for this patent is the original inventor-to-company assignment. I could not retrieve its reel/frame, correspondent, or any post-issuance link; there is no indexed Assignment Center page I could load.

• 2012-05-08 (application filed) / executed ≈ 2012-05-08 / recorded 2012-05-14 — Reel not retrieved
  • Conveyance: Assignment (assignment of assignors' interest)
  • Assignor: Daniel J. Wendt; Michel Claude Vellard; Mika Aoyagi-Scharber; Christopher P. Price; Sianna Castillo; Shinong Long; Augustus O. Okhamafe (all seven, jointly)
  • Assignee: BioMarin Pharmaceutical Inc., Novato/San Rafael, CA
  • Correspondent: Not retrieved — cannot be confirmed without the Assignment Center record. No correspondent inference is safe here.
  • Context: Original employment/ownership assignment; no arm's-length transfer.

No post-issuance assignment is evidenced. Google Patents' legal-events tab for US 8598121 lists only the original BioMarin assignment, grant (2013-12-03), and the "priority to" filings US 14/604,262 (2015-01-23), US 14/660,488 (2015-03-17), US 15/332,793 (2016-10-24), and US 15/646,822 (2017-07-11). Those are continuation/reissue filings, not assignments — they do not change ownership. On the record available to me, BioMarin still owns US 8598121.

If the Assignment Center in fact contains additional links (e.g., a security agreement, a change-of-name correction, or a later recordation), I did not find them and did not invent them. Verify directly: https://assignmentcenter.uspto.gov/ (search "8598121") and https://assignment.uspto.gov/patent/index.html

Timeline diagram

timeline
    title Ownership of US 8598121
    2009 : Priority date
    2012 : Filed by BioMarin
         : Inventors assign to BioMarin
    2013 : Patent issued
    2015 : Reissue continuation filed
    2021 : Voxzogo approved
    2025 : BioMarin sues Ascendis
    2026 : Global settlement with Ascendis

NPE / troll-pattern signals

1. Shell-entity transfer — Not present. The only recorded assignee is BioMarin Pharmaceutical Inc., an operating biopharma with products in commerce (VOXZOGO). No "IP/Licensing/Holdings/Ventures" LLC appears anywhere in the chain.

2. Known asserter in the chain — Not present. Neither the original assignee nor any counterparty matches a public NPE list (Acacia, Marathon, IV, Wi-LAN/Conversant, Pendrell, Vringo, Round Rock, etc.). The adverse party in the resulting litigation, Ascendis Pharma A/S, is itself an operating, Nasdaq-listed drug developer.

3. Repeat correspondent across the chain — Unclear / not present. I could not retrieve the recording correspondent; with only a single conveyance in evidence there is no recurrence to pattern-match. Insufficient data to call.

4. Cascading transfers — Not present. One assignment, recorded six days after filing; no chained LLC-to-LLC transfers.

5. Pre-litigation transfer — Not present. No transfer predates the litigation. BioMarin asserted the CNP estate as the original owner, which is the opposite of a "clean-standing" reassignment pattern.

6. Bankruptcy fire-sale — Not present. BioMarin has not filed for bankruptcy; the family has not been sold in a Chapter 7/11 proceeding.

7. Privateering — Not present. BioMarin sues in its own name against a direct market competitor (Ascendis and its TransCon CNP/Yuviwel), not through a proxy NPE. The 2026 settlement has BioMarin granting Ascendis a license and taking 20% U.S. / 18% ex-U.S. royalties through May 20, 2030 — the economics flow to the operating company, not to an assertion vehicle.

8. Defensive aggregator — Not present. The chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN. The patent remains with the practicing entity.

Litigation context (family-level, not necessarily this exact patent): Darts-IP flags "family has litigation." BioMarin pursued disputes against Ascendis in the U.S. (including a Section 337 ITC action and N.D. Cal.), Brazil, Denmark, Germany and South Korea, centered on BioMarin's CNP patents; those proceedings settled globally on/around 2026-08-30. The ITC petition text I saw references a later family member (the "106 patent") as the asserted U.S. patent, so direct assertion of US 8598121 by number is unclear — but its reissues (RE46707, RE48267) sit in the same asserted estate.

Verdict

Operating-company assertion.

US 8598121 never left BioMarin Pharmaceutical Inc. — the sole recorded conveyance is the 2012-05-14 inventor-to-company assignment (executed ≈ 2012-05-08 at filing), and no shell-entity, asserter, or aggregator appears anywhere in the chain. BioMarin is a Nasdaq-listed rare-disease manufacturer whose VOXZOGO (vosoritide) product embodies the claimed CNP technology, and it asserted the family in its own name against a direct competitor (Ascendis), settling in 2026 for 18–20% royalties through May 2030. Because I could not load the Assignment Center reel/frame data, I cannot rule out an unrecorded or unindexed post-issuance link — but nothing in the evidence points to NPE activity.

Verify at: https://assignmentcenter.uspto.gov/ and https://assignment.uspto.gov/patent/index.html (search patent number 8,598,121).

Caveat: Reel/frame numbers, the recording correspondent, and any post-issuance records were not retrievable via the tools available to me and are expressly not fabricated above.

I'll research US patent 8598121 and its cited prior art. Let me search for authoritative sources.

Let me get the specific cited prior art references from USPTO/Justia for this patent.

Let me look for the specific cited references sections on FreePatentsOnline and Justia.

Prior Art Analysis — US 8,598,121 B2

Before the analysis, an important transparency note on sourcing and limitations.

I searched public patent databases (Google Patents, Justia Patents, Espacenet, and reference lists surfaced from related family documents). I was not able to retrieve the complete, authoritative front‑page "(56) References Cited" list (the examiner's U.S. Patent Documents / Foreign Patent Documents / Other Publications table) for US 8,598,121. The Google Patents and Justia pages returned partial content and I could not pull the full citation table within my search budget. Everything below is therefore labeled as either (a) verified bibliographic fact, (b) a reference cited within the patent's own specification (from the authoritative full text I was given), or (c) a reference I found associated with this family but could not confirm is on this patent's face. I have not fabricated any citation; where I am unsure of an exact date or number I say so.

1. Verified identity of the patent (do not auto‑correct)

Critical framing point: US 8,598,121 is a divisional/continuation in the same family as US 8,198,242 and US 2010/0297021. It therefore shares the same specification as its parent. That matters because the reference list "for 8598121" overlaps heavily with the parent's, and the parent itself (US 2010/0297021 / US 8,198,242) and WO 2010/135541 are not prior art — they are the same family.

2. What the granted claims actually cover (this governs the § 102 analysis)

From the granted claim set (Espacenet claim text for US 8,598,121 B2):

• Claim 1 — A variant of CNP selected from the group consisting of:
  • Gly‑CNP53 (SEQ ID NO: 179) = G‑DLRVDTKSRAAWARLLQEHPNARKYKGANKKGLSKGCFGLKLDRIGSMSGLGC
  • Pro‑CNP53 (SEQ ID NO: 185)
  • Met‑CNP53 (SEQ ID NO: 190)
  • CNP‑53(M48N) (SEQ ID NO: 180)
• Claims 2–4 — Pharmaceutical composition / lyophilized formulation (citrate or acetate buffer, pH ~4–6; isotonicity/bulking agent or antioxidant).
• Claim 5 — Method of treating a bone‑related disorder/skeletal dysplasia (achondroplasia, hypochondroplasia, short stature, dwarfism, homozygous achondroplasia) by administering a claim‑1 variant.
• Claims 6–11 — Method of recombinant production using a CNP‑variant/cleavable‑peptide fusion; cleavable partners including His tags, TAF12 and its mutants (TAF12(C/A & 4D/4E), etc.), KSI, MBP, β‑Gal, GST, thioredoxin, CBD, BMP‑2; cleaving agents including formic acid, CNBr, hydroxylamine, Factor Xa, enterokinase, ProTEV, SUMO protease.
• Claim 12 — A CNP variant produced by the claim‑6 method.

Implication: The claims are narrow and sequence‑specific (the four 53/54‑mer variants) plus method/format claims. Anticipation under § 102 requires a single reference disclosing each and every element — for claim 1, the exact sequence. This is a high bar, and I could not identify a verified single anticipatory reference for the sequence claims from the accessible material. The description cites the following references, none of which disclose these exact sequences.

3. Prior‑art / cited references appearing in the patent's own specification

These four patent documents are expressly discussed in the US 8,598,121 specification (authoritative full text provided). All predate the 2009‑05‑20 priority date by years, so each qualifies as prior art under pre‑AIA § 102(b).

3.1 WO 94/20534

• Full citation: WO 94/20534 (PCT international publication), "Chimera of CNP‑22 and the 5‑amino‑acid C‑terminus of ANP designated as the vasonatrin peptide (VNP)…"; also discloses a limited number of amino‑acid substitutions and cyclic chimeric peptides formed by disulfide or double bonds.
• Date: published 1994 (WO numbering places it in the second‑half 1994 publication series; I could not confirm the exact day).
• Brief description: Discloses the vasonatrin peptide (VNP), a CNP‑22/ANP chimeric peptide, and cyclic chimeric natriuretic peptides.
• § 102 relevance: Does not anticipate claim 1 (or claims 2–12). VNP is a ~27‑amino‑acid chimera of CNP‑22, not a CNP‑53/pro‑CNP‑53 sequence; it lacks SEQ ID NOs 179/180/185/190. Its relevancy is as § 103 background for chimeric/extended CNP concepts, not as § 102 art against these claims.

3.2 U.S. Pat. No. 5,846,932

• Full citation: U.S. Pat. No. 5,846,932 (per the specification: an approach for improving the half‑life of natriuretic peptides by decreasing the affinity of ANP for NPR‑C).
• Date: granted 1998 (I could not confirm the exact grant date from my accessible sources; the number falls in the 1998 series).
• Brief description: Natriuretic‑peptide engineering directed at ANP/NPR‑C affinity to extend half‑life.
• § 102 relevance: Does not anticipate any of claims 1–12. It addresses ANP, not CNP‑53 variants, and does not disclose the recited fusion‑production methods. § 103 background only (concept of reducing NPR‑C clearance).

3.3 WO 00/61631

• Full citation: WO 00/61631 — per the specification, the use of pentapeptide antagonists of NPR‑C.
• Date: published 2000.
• Brief description: Small peptide antagonists of the natriuretic clearance receptor NPR‑C.
• § 102 relevance: Does not anticipate claims 1–12. It is a receptor‑antagonist approach, not a CNP‑53 variant composition or the claimed recombinant method. § 103 background only.

3.4 WO 2004/047871

• Full citation: WO 2004/047871 — per the specification, "conjugates of BNP and BNP variants to polyalkylene glycol moieties, sugar moieties, polysorbate moieties, polycationic moieties… for the treatment of acute congestive heart failure."
• Date: published 2004.
• Brief description: PEGylated/polymer‑conjugated BNP variants for heart failure.
• § 102 relevance: Does not anticipate claims 1–12. The disclosure is BNP‑based conjugates; it does not disclose the gly‑/pro‑/met‑CNP‑53 sequences or the TAF12/KSI/MBP fusion‑cleavage production methods. § 103 background only (conjugation strategy for half‑life extension).

3.5 Other patent documents referenced in the specification / broader family

• WO 2009/067639 — listed in the family's related‑art discussion as disclosing CNP variant peptides with improved properties. Its publication date is after the 2009‑05‑20 priority date, so it is not § 102(b) art; it may be relevant as an interference/§ 102(e)‑era or § 103 reference depending on its own filing date, which I could not confirm.
• U.S. Pat. No. 7,276,481 — cited as prior art (CNP analogs) in the background of later family patents (e.g., RU 2,728,567 / RU 2,759,679). I could not confirm that US 7,276,481 appears on the face of US 8,598,121; treat this as unverified for this specific patent.

4. Non‑patent literature cited in the patent's own text

The specification (and the reference list surfaced via Justia) cites the following. None discloses the claim‑1 sequences; each is background for CNP biology, NEP/NPR‑C clearance, or the recombinant‑protein/peptide‑synthesis toolset.

Patent‑chemistry / NEP / NPR‑C background:

• Schiller, Biochem. Biophys. Res. Commun. 138: 880–886 (1986) — the 17‑aa cyclic CNP structure is important for NPR‑B binding.
• Kenny et al., Biochem. J. 291(Pt 1): 83–8 (1993) — NEP (endopeptidase‑24.11) hydrolyzes CNP/BNP/ANP.
• Oefner et al., J. Mol. Biol. 296: 341–349 (2000) — NEP active‑site size limits (<~3 kDa).
• Wu et al., J. Biol. Chem. 278: 25847–852 (2003) — processing/circulating CNP‑53 vs CNP‑22.
• Yeung, Peptides 17: 101–106 (1996) — CNP‑53 and CNP‑22 bind NPR‑B and stimulate cGMP similarly.
• Alfonzo, Recept. Signal. Transduct. Res. 26: 269–297 (2006).
• Hunt et al., J. Clin. Endocrinol. Metab. 78: 1428–35 (1994) — plasma half‑life of CNP‑22 in man.
• Jin et al., J. Clin. Invest. 98: 969–76 (1996) — NPR‑A‑selective ANP analog.
• He et al., Science 293: 1657–62 (2001); He et al., J. Mol. Biol. 361: 698–714 (2006) — natriuretic‑peptide receptor structure/specificity.

Achondroplasia/bone‑growth background:

• Krejci et al., J. Cell Sci. 118: 5089–5100 (2005) — FGFR3 signaling in growth‑plate chondrocytes.
• Yamashite et al., J. Biochem. 127: 177–179 (2000) — NPR‑B/NPR‑C expression zones in growth plate.
• Horton et al., J. Pediatr. 93: 435–8 (1978) — achondroplasia growth curves.
• Honing et al., Hypertension 37: 1179–83 (2001); Horio et al., Endocrinology 144: 2279–84 (2003); Itoh et al., Am. J. Respir. Crit. Care Med. 170: 1204–11 (2004); Inoue et al., PNAS 100: 10079–84 (2003); Hama et al., BBRC 198: 1177–82 (1994); Igaki et al., Hypertens. Res. 21: 7–13 (1998).

Recombinant‑protein/ligation toolset (background for claims 6–12):

• Hofmann et al., Curr. Opin. Biotechnol. 13: 297–303 (2002) — expressed protein ligation.
• Sambrook/Fritsch/Maniatis, Molecular Cloning: A Laboratory Manual, 2nd ed.; Atherton & Sheppard, Solid Phase Peptide Synthesis (general methods).

Sequence‑database art (closest to claim 1):

• GenBank NP_077720 (human NPPC/CNP precursor) and NP_002512 (NPP B) / NP_006163 (NPP A) — flagged in the reference list as dated 2010‑07‑18.
• The CNP‑53/pro‑CNP‑53 native sequences are effectively public via NP_077720. This is the nearest thing to a § 102 reference against a "Pro‑CNP53 / Met‑CNP53 / Gly‑CNP53" claim, but native NPPC does not itself disclose a Gly‑, Pro‑, or Met‑ N‑terminal extension, nor the M48N substitution — so it would not, on its face, anticipate claim 1. It is best characterized as § 103 art.

5. Claim‑by‑claim § 102 conclusion

Bottom line on § 102: Of the references I could ground, none anticipates the granted claims of US 8,598,121 under 35 U.S.C. § 102. The four patent documents expressly cited in the specification (WO 94/20534; US 5,846,932; WO 00/61631; WO 2004/047871) are directed at different inventions — VNP chimeras, ANP/NPR‑C affinity engineering, NPR‑C pentapeptide antagonists, and BNP‑polymer conjugates respectively — and function as § 103 background, not § 102 references, against these narrow, sequence‑specific claims. The closest art to claim 1 is the public native CNP‑53/NPPC sequence, but it does not disclose the claimed N‑terminal extensions or the M48N substitution.

6. What I could not verify (explicit gaps — no fabrication)

1. The face‑of‑patent "(56) References Cited" table (examiner‑cited U.S. patents, foreign documents, and other publications) for US 8,598,121 — not retrievable in this session. The items in § 3 are specification‑cited references, which often, but do not always, overlap with the examiner's citations.
2. Exact publication days for WO 94/20534, WO 00/61631, WO 2004/047871, and the exact grant date of US 5,846,932 — I gave the year/series only.
3. Whether US 7,276,481 and WO 2009/067639 appear on this patent's face (they appear in related later‑family documents).
4. Any potential § 102(e) U.S. application by another party disclosing the same CNP‑53 variants — I found none, but absence of evidence is not evidence of absence.

If you can supply the front‑page "(56) References Cited" image/OCR for US 8,598,121 (USPTO PatentCenter or the granted‑patent PDF), I can complete a precise, reference‑by‑reference § 102 mapping against the granted claims.

I'll gather the prior-art citations and related prosecution context before building the § 103 analysis.

Let me verify what several key cited references actually disclose, since the § 103 combinations must be grounded in their content.

1. Identification and scope

Because the application was filed before 2013‑03‑16 and claims only pre‑AIA priority, pre‑AIA § 102/§ 103 (KSR) applies, including pre‑AIA § 103(c) disqualification of commonly‑owned § 102(e) art.

Claim 1 (the claim of interest) is a four‑member Markush of specific peptides:

• Gly‑CNP53 — GDLRVDTKSRAAWARLLQEHPNARKYKGANKKGLSKGCFGLKLDRIGSMSGLGC (SEQ ID NO: 179)
• Pro‑CNP53 — PDLRVDTKSRAAWARLLQEHPNARKYKGANKKGLSKGCFGLKLDRIGSMSGLGC (SEQ ID NO: 185)
• Met‑CNP53 — MDLRVDTKSRAAWARLLQEHPNARKYKGANKKGLSKGCFGLKLDRIGSMSGLGC (SEQ ID NO: 190)
• CNP‑53(M48N) — DLRVDTKSRAAWARLLQEHPNARKYKGANKKGLSKGCFGLKLDRIGSNSGLGC (SEQ ID NO: 180)

Dependent claims cover a pharmaceutical composition (2), a lyophilized citrate/acetate‑buffered pH 4–6 formulation with isotonicity/bulking agent or antioxidant (3–4), a method of treating skeletal dysplasia/achondroplasia etc. (5), a recombinant fusion‑protein production method using TAF12, KSI, MBP, β‑gal, GST, Trx, CBD, BMP‑2 etc. as cleavable partners in bacteria, with formic acid/CNBr/hydroxylamine/Factor Xa/enterokinase/ProTEV/SUMO protease cleavage (6–11), a product‑by‑process claim (12), and a method of increasing long bone growth (13).

Caveat on the record: the claim text I analyzed comes from Espacenet/Justia renderings of US 8,598,121 B2 (https://hr.espacenet.com/publicationDetails/claims?...NR=[8598121B2](/patent/8598121B2); https://patents.justia.com/patent/[8598121](/patent/8598121)), and it matches the "14 Claims" statement on the granted PDF (https://patentimages.storage.googleapis.com/4b/b9/98/0cad2d45671b7a/US8598121.pdf). Secondary databases (e.g., DrugPatentWatch) reproduce the same claim wording under RE48,267. I have not personally opened the printed claim column of the granted patent; if the granted claim 1 differs, the analysis below should be re‑run on the corrected text.

2. Prior art on the face of the patent (the "Prior Art" section to be used)

US patents cited (from the granted front page and the identical list in RE48,267, confirmed by OCR of the US 8,598,121 PDF): US 5,252,714 (Harris, 10/1993 — PEG derivatives/conjugation); US 5,352,770 (Matsuo, 10/1994); US 5,434,133 (Tanaka, 7/1995); US 5,824,784 (Kinstler, 10/1998); US 5,846,932 (Lowe, 12/1998); US 6,020,168 (Matsuo et al., 2/2000); US 6,034,231 (Tanaka et al., 3/2000); US 6,136,040 (Ornitz, 10/2000); US 6,265,632 (Yayon, 7/2001); US 6,329,375 (Tang, 12/2001); US 6,344,459 (Bridges, 2/2002); US 6,743,425 (Nakao, 2/2004); US 6,849,714 (Bridon, 2/2005); US 6,861,236 (Moll, 3/2005); US 7,276,481 (Golembo, 10/2007); US 2004/0138134 and 2008/0194682 (Golembo); US 2007/0197434 (Nakao); US 2007/0292966 (Prickett). WO 94/20534 (Matsuo) is the principal foreign reference.

References verified to teach what the analysis needs:

• US 7,276,481 (Golembo). The abstract and specification state the invention "provide[s] a method for the treatment of skeletal dysplasias," preferably using CNP or a CNP variant, that it "affect[s] bone elongation … by increasing the size of the growth plate," and that it provides "NP variants with increased stability," fusion proteins/conjugates with a carrier domain for growth‑plate targeting, and co‑administration of NEP inhibitors (thiorphan, candoxatril) or NPR‑C inhibitors. It also cites US 6,329,375 and 6,344,459 as FGFR tyrosine‑kinase inhibitors for combination. (https://uspto.report/patent/grant/[7,276,481](/patent/7276481); https://patents.google.com/patent/[US7276481B2](/patent/US7276481B2)/en)
• WO 94/20534 — as described in the patent's own background: a CNP‑22/ANP C‑terminal chimaera ("vasonatrin," VNP), plus "a limited number of amino acid substitutions and cyclic chimeric peptides."
• US 5,846,932 — as described in the patent's own background: reducing ANP affinity for NPR‑C.
• WO 00/61631 and WO 2004/047871 — NPR‑C pentapeptide antagonists; and BNP/BNP‑variant conjugates to polyalkylene glycol etc. with improved circulatory half‑life.
• Non‑patent literature cited on the face and relied on in the specification: Wu, J. Biol. Chem. 278:25847‑852 (2003) (furin cleavage of pro‑CNP yields CNP‑53, later trimmed to CNP‑22); Yeung, Peptides 17:101‑106 (1996) ("Both CNP‑53 and CNP‑22 bind similarly to NPR‑B … they both induce cGMP production in a dose‑dependent and similar fashion"); Alfonzo, Recept. Signal. Transduct. Res. 26:269‑297 (2006) (CNP‑53 is the predominant tissue form); Oefner, J. Mol. Biol. 296:341‑349 (2000) ("NEP preferably recognizes substrates smaller than about 3 kDa, due to the limited size of its active site cavity"); Brandt, Hypertension 30:184‑190 (1997) (NEP regulates CNP metabolism); Hunt, J. Clin. Endocrinol. Metab. 78:1428‑35 (1994) (CNP bioactivity/metabolism in man); Caliceti, Adv. Drug Deliv. Rev. 55:1261‑77 (2003) (PEG–protein conjugate PK/biodistribution); Chusho, PNAS 98:4016‑21 (2001) (CNP‑null dwarfs); Agoston, BMC Dev. Biol. 7:18 (2007) (CNP regulates endochondral bone growth); Bartels, Am. J. Hum. Genet. 75:27‑34 (2004) (NPR‑B mutations → skeletal dysplasia).

References I could not verify in this session (so I do not rest any conclusion on their specific content): US 5,352,770, US 5,434,133, US 6,020,168, US 6,034,231, US 6,743,425, US 6,849,714, US 6,861,236, US 6,265,632, US 6,136,040, US 2007/0292966, and WO 02/074234 / WO 03/059291. I also did not retrieve the prosecution history of 13/466,672.

Two important prior‑art exclusions: WO 2009/067639 / US 2010/0331256 A1 (the applicants' own earlier PCT/§ 102(e) publication from PCT/US08/84270) and the sibling US 8,198,242 / US 8,377,884 cannot be used in a § 103 combination because they are commonly owned § 102(e) subject matter (pre‑AIA § 103(c)). Likewise WO 2010/135541 (the PCT publication of this family, published 2010‑11‑25) is not prior art against a 2009‑05‑20 priority date.

3. § 103 analysis — claim 1

3.1 The dispositive fact: CNP‑53 is a known, naturally occurring human peptide

The specification concedes the entire structural premise: CNP is made as pre‑pro‑NPPC, furin cleavage "generates an active 53‑amino‑acid peptide (CNP‑53)… cleaved again… to produce the mature 22‑amino‑acid peptide (CNP‑22)" (Wu 2003); CNP‑53 "predominat[es] in tissues"; and CNP‑53 and CNP‑22 "bind similarly to NPR‑B" and give equivalent cGMP dose‑responses (Yeung 1996). CNP‑53 per se is therefore prior art, and it is the base structure of every claim‑1 species.

The only structural differences are:

That the applicant itself treated these as recombinant intermediates, not designed molecules, is evident from its own figures: FIG. 10 is an "LC/MS chromatogram showing the peak for Pro‑CNP53 after formic acid cleavage of TAF‑Pro‑CNP53," and FIGS. 2–5 show formic‑acid cleavage of TAF‑Pro‑CNP38 to give "Pro‑Gly‑CNP37." The claim‑1 genus is, in substance, "CNP‑53 plus whatever the expression/cleavage chemistry leaves on the N‑terminus."

3.2 Combination 1 (primary): Golembo '481 + Wu 2003 / Yeung 1996 / Alfonzo 2006 + Oefner 2000 / Brandt 1997 / Caliceti 2003

Golembo '481 supplies the therapeutic problem and the design imperative: treat skeletal dysplasias (achondroplasia) with CNP or "functional variants," effect bone elongation by enlarging the growth plate, make "NP variants with increased stability," and prolong circulatory residence (it proposes NEP inhibitors and NPR‑C inhibitors as one route). Wu/Yeung/Alfonzo supply the identity and bioequivalence of the natural 53‑mer. Oefner supplies the design rule that the NEP active‑site cavity excludes substrates "smaller than about 3 kDa," i.e., the express teaching that increasing the mass of a natriuretic peptide above that threshold is the way to defeat NEP, and Brandt confirms NEP is the relevant CNP‑degrading activity in vivo. Caliceti supplies the general expectation that increasing effective molecular size/hydrodynamic radius lengthens peptide half‑life. Chusho/Agoston/Bartels supply the FGFR3/NPR‑B biology linking CNP signalling to the disease.

Motivation, articulated as a POSA would: the art identifies the goal (a longer‑acting CNP for achondroplasia), identifies the mechanism of loss (NEP clearance, with a size cutoff), and identifies a known, natural, fully active CNP species — CNP‑53 — that already sits well above that cutoff. Selecting CNP‑53 and adding one N‑terminal residue is not merely "obvious to try"; it is a finite, identified, predictable design space, satisfying KSR's "finite number of identified, predictable solutions" rationale. Where the N‑terminal residue is Met (190), the addition is not even a design choice — it is the unavoidable consequence of bacterial translation initiation, and its retention is the default unless deliberate processing is performed (cf. the "Pro‑" and "Gly‑" species, which are the products of the applicant's own formic‑acid/Asp‑Pro and leader‑peptide choices recited in claims 6 and 11). For Gly‑CNP53 and Pro‑CNP53, the motivation goes further: both are disclosed‑by‑construction products of the very recombinant/chemical‑cleavage route that the art (and Golembo's fusion‑protein teachings) supplies.

3.3 Combination 2: WO 94/20534 (and the Matsuo/Tanaka CNP‑derivative patents) + Golembo '481 — N‑terminal extension is a tolerated, known modification

WO 94/20534 discloses CNP‑22 chimaeras with heterologous C‑terminal residues, expressed substitutions at defined positions, and cyclic variants — i.e., it teaches that the ends of the CNP‑22 module can be modified while retaining natriuretic activity. Combined with Golembo's stated aim of variant engineering, this rebuts any argument that "extending CNP at the N‑terminus with a single residue" departed from the art. (I note the Matsuo/Tanaka US patents as corroborating art, but I have not verified their text and do not rely on them.)

3.4 The M48N species specifically

Lowe '932 and WO 2004/047871 establish the general proposition that natriuretic‑peptide analogues with single substitutions are routinely made and screened to tune receptor affinity/half‑life. The specification itself lists, for the position corresponding to Met17 of CNP‑22, the allowed set "Met, Val, Asn, beta‑Cl‑Ala, 2‑aminobutyric acid (Abu) and 2‑amino‑isobutyric acid (Aib)" — an express, art‑recognized enumeration of a handful of predictable replacements. Replacing an oxidation‑labile methionine with a conservative, chemically inert residue (Asn is in the same size/polarity neighbourhood and is not a Met‑oxidation liability; Hunt 1994 documents CNP's rapid metabolic turnover) is a textbook "obvious to try" substitution with a reasonable expectation of retained NPR‑B agonism, because the residue lies outside the 17‑membered Cys6–Cys22 ring that Schiller 1986 identified as the receptor‑binding determinant.

Conclusion on claim 1: on this record, claim 1 appears highly vulnerable under § 103. Each Markush member is a one‑residue modification of a known endogenous human peptide whose activity was expressly acknowledged in the specification, made for the express, art‑supplied purpose of evading a size‑limited peptidase.

4. § 103 analysis — the remaining claims

Claims 2–4 (composition; lyophilized citrate/acetate pH 4–6 + isotonicity/bulking agent or antioxidant). WO 2004/047871 (formulations of natriuretic‑peptide conjugates) and US 5,824,784 (Kinstler; lyophilized, chemically modified protein compositions) supply peptide/protein lyophilization and buffer selection. pH and buffer identity are result‑effective variables within the artisan's routine optimization under In re Aller/Kuehl, and the specification offers no data showing criticality of citrate/acetate or pH 4–6. Expect a strong § 103 rejection.

Claims 6–12 (recombinant fusion production). Golembo '481 expressly teaches linking a natriuretic peptide to a carrier protein/targeting moiety as a fusion protein or conjugate to prolong half‑life and target the growth plate. The remaining limitations are conventional molecular biology (the specification itself cites Sambrook/Fritsch/Maniatis and Current Protocols; the host strains and vectors pET‑21a, pET‑31b, pET‑15b, pET‑32a, pET‑41a, pMAL, pQE‑30, pET‑SUMO, pET‑22b, pTYB11 are art‑standard) and art‑standard cleavable‑tag/cleavage‑reagent pairs: formic acid (Asp‑Pro), CNBr (Met), hydroxylamine (Asn‑Gly), Factor Xa, enterokinase, ProTEV, SUMO protease. The motivation (solubility, purification, and releasing the authentic peptide) is the universal rationale for fusion tags, so claims 6 and 8–12 look vulnerable.
Claim 7 is the most defensible claim in the patent, because it names human transcription factor TAF12 and specific TAF12 mutants (TAF12(C/A), 4D/4E, 6D/6E, 10D/10E, etc.) as the cleavable fusion partner. A rejection here would need art disclosing a histone‑fold/small acidic protein as a solubility/expression tag, or would have to rely on KSR's "known alternatives" logic applied to the class of small solubility tags (MBP, Trx, NusA, SUMO). I could not verify TAF12‑as‑tag art in this session, so I flag this as the claim on which the patent most plausibly survives.

Claims 5 and 13 (treating skeletal dysplasia / increasing long bone growth). Golembo '481 is squarely on point: it claims and describes "a method for the treatment of skeletal dysplasias," names achondroplasia, and states that the method "affect[s] bone elongation … by increasing the size of the growth plate." Chusho 2001 and Agoston 2007 establish CNP's causal role in endochondral ossification. Selecting the CNP‑53 variants of claim 1 as the administered agent adds nothing patentable over claim 1. These claims look highly vulnerable.

5. Arguments the patent owner would raise, and why they are weak here

1. No teaching to select the 53‑mer. The counter is the specification's own admissions: CNP‑53 is natural, tissue‑predominant, and equipotent to CNP‑22 at NPR‑B (Yeung 1996, cited on the face). A known compound with known activity, differing by one residue, is the paradigm KSR case.
2. Teaching away. Golembo proposes NEP inhibitors rather than larger CNP analogues, but it does not criticize or discredit size engineering — it expressly seeks "NP variants with increased stability," which is the opposite of a teaching away.
3. Unexpected results / secondary considerations. This is where the patent is weakest on claim 1. The impressive in vivo data in the specification (FIGS. 45–61: multi‑fold half‑life and bioavailability gains, cGMP increases, femur/tibia/tail/spine elongation in FGFR3^ach mice) are generated with CNP37, Pro‑Gly‑CNP37 ("Pro‑CNP38") and PEO24‑GANRR‑CNP22(K4R) — the 37/38‑mer and the PEGylated 27‑mer — not with the claimed Gly‑/Pro‑/Met‑CNP53 or CNP‑53(M48N). There is therefore no nexus between the claimed species and the asserted surprising properties, and no unexpected‑result rebuttal available for claim 1. (By the same token, the specification's own suggestion that smaller peptides may diffuse through cartilage more readily cuts against any argument that the larger 53‑mers were unpredictably superior.)
4. Commercial success. The Aug‑31‑2026 BioMarin/Ascendis settlement (20 % U.S. / 18 % EU‑KR‑BR royalties to May 20, 2030) demonstrates value, but the asserted patents in that dispute centred on the reissue RE48,267 (the DrugPatentWatch rendering of its claim 1 tracks the claim‑1 Markush analysed above) and on later claims such as US 12,233,106 — and settlement is not an adjudication of validity. Note also that the PGR petition found at PTAB (petition 1558718) attacks US 12,233,106, not US 8,598,121; its § 325(d) discussion of "vosoritide" prior art and the RE'267 ITC patent is context only and should not be imported into a § 103 analysis of US 8,598,121.
5. Claim 1 is a narrow Markush, so the burden is on the challenger to reach every member. That is a real procedural obstacle, but it is overcome here because the three N‑terminal extensions are all characterized and motivated by the same recombinant/cleavage chemistry and the same size/NEP rationale, and M48N is one conservative substitution expressly enumerated in the specification.

6. Bottom line

On the prior art cited on the face of US 8,598,121 — principally Golembo US 7,276,481 in view of Wu 2003, Yeung 1996, Alfonzo 2006 (CNP‑53 is a known, NRP‑B‑equipotent human peptide), further in view of Oefner 2000, Brandt 1997 and Caliceti 2003 (NEP's ~3 kDa size cutoff; size increase as the recognized half‑life strategy), and secondarily WO 94/20534, Lowe US 5,846,932, WO 2004/047871 and Kinstler US 5,824,784 — claims 1–6 and 8–13 would, in my assessment, be more likely than not held obvious under KSR, with claim 7 (TAF12 fusion partners) the most defensible. The strongest non‑obviousness material the patent owner possesses (the in vivo achondroplasia efficacy and PK data) is directed at species outside claim 1's Markush, so it supplies no nexus.

Two things I want to be explicit about rather than paper over: (i) I was unable to verify the granted claim text against the printed patent, and the same claim wording is also published under RE48,267; and (ii) I was unable to verify the disclosures of US 5,352,770, US 5,434,133, US 6,020,168, US 6,034,231, US 6,743,425, US 6,849,714, US 6,861,236, US 6,265,632, US 6,136,040, US 2007/0292966 and WO 02/074234 / WO 03/059291, so no conclusion above depends on them.