US 8431598

I'll search for authoritative information on US patent 8,431,598, including any 2026 CAFC activity.

Let me search specifically for any 2026 CAFC docket activity involving this patent.

Let me check for any 2026 Federal Circuit activity specifically.

Summary of US Patent 8,431,598 B2

Important caveat up front: I could not access USPTO PatentCenter/PAIR, the CAFC docket system, or PACER directly. Everything below is drawn from indexed sources (Google Patents, Espacenet, CourtListener, PubChem patent record, and litigation complaints). I found no 2026 Federal Circuit docket, appeal, or decision specifically involving US 8,431,598. If a 2026 CAFC appeal exists, it is not indexed in the sources I could reach, and I cannot confirm or deny its existence. All alphanumeric identifiers are reproduced literally as found.

Bibliographic data

Continuity (from the face of the patent): Divisional of Ser. No. 12/220,336 (now US 7,977,357), which is a divisional of Ser. No. 10/934,863 (now US 7,465,800), which claims benefit of provisional 60/499,723 filed 2003-09-04. The same specification underlies other family members asserted in the Revlimid litigation, including the ’357, ’219, ’800, and ’217 patents.

Note on inventorship discrepancy: the assignment record and the corresponding Norwegian national patent (NO 336898 B1) list Manohar T. Saindane and Louise M. Cameron as additional inventors/assignors, while Google Patents' "Inventor" field for US 8,431,598 lists only Jaworsky, Chen, and Muller. I cannot resolve which is authoritative from the sources available.

Abstract

"Polymorphic forms of 3-(4-amino-1-oxo-1,3 dihydro-isoindol-2-yl)-piperidine-2,6-dione are disclosed. Compositions comprising the polymorphic forms, methods of making the polymorphic forms and methods of their use are also disclosed."

Plain-language overview of the independent claims

The ’598 patent has at least 23 claims; claims 1–4 recite "Form A" expressly, and claims 5–23 cover unsolvated crystalline lenalidomide defined by measured characteristics rather than by the "Form A" label. The independent claims I could verify are:

• Claim 1 – A solid form of lenalidomide comprising unsolvated crystalline Form A, characterized by a DSC thermogram endotherm at approximately 270 °C, where that crystalline form makes up more than about 80% by weight of the total lenalidomide. (Plainly: a substantially pure, water-free crystal form of lenalidomide that melts near 270 °C.)

• Claim 5 – A solid form of lenalidomide comprising an unsolvated crystalline form defined by three combined analytical fingerprints: (i) a DSC endotherm at ~270 °C; (ii) an XRPD pattern with peaks at approximately 8, 14.5, and 16 degrees 2θ; and (iii) a TGA curve indicative of an unsolvated material — again present at greater than about 80% by weight of the total lenalidomide. (Claim 9, which depends on claims 5–8, adds XRPD peaks at ~17.5, 20.5, 24 and 26 degrees 2θ.)

• Claim 14 – A pharmaceutical composition comprising a therapeutically effective amount of the solid form of any one of claims 1–8 and 10–13, together with a pharmaceutically acceptable excipient, diluent, or carrier.

• Claim 17 – A pharmaceutical composition comprising from about 5 mg to about 25 mg of a solid form of lenalidomide comprising an unsolvated crystalline form having a DSC thermogram endotherm at approximately 270 °C, plus a pharmaceutically acceptable excipient, diluent, or carrier. Dependent claims 21, 22, and 23 respectively narrow this to about 5 mg, 10 mg, and 25 mg.

Uncertainty: claim 10's text and whether any independent claims exist beyond claim 23 (e.g., method-of-treatment claims) were not visible in the sources I retrieved. I am not certain of the exact total claim count.

Key claim-construction history (relevant context)

In Celgene Corp. v. Natco Pharma Ltd., No. 2:10-cv-05197 (D.N.J.), Judge Wigenton's May 27, 2014 Markman Opinion construed "Form A" as used in the ’598 patent's claims 1–4 to mean "the lenalidomide crystal form described in the specification as Form A, having all of the characteristics assigned to Form A in the specification" — a narrowing construction that Celgene had opposed. Natco argued its ANDA product was a distinct polymorph ("Form I"). Celgene thereafter stipulated to dismissal of certain other patents and settled with Natco. See https://storage.courtlistener.com/recap/gov.uscourts.njd.[247596](/patent/247596).252.0.pdf and https://www.courtslistener.com/docket/[4310166/252](https://assignmentcenter.uspto.gov/search/patent/reelFrameDetail?reelFrame=4310166-0252)/ (as indexed).

The ’598 patent was asserted in numerous Revlimid/lenalidomide ANDA suits, including against Sun, Lotus/Alvogen, Hetero, Mylan, Cipla, Dr. Reddy's, and others, and it features in the consolidated antitrust litigation In re Revlimid and Thalomid Purchaser Antitrust Litigation (D.N.J. 2:19-cv-07532) and related 2023–2026 private antitrust complaints (e.g., https://www.courthousenews.com/wp-content/uploads/2026/05/bristol-myers-squibb-celgene-antitrust-complaint-new-jersey.pdf). Notably, the ’598 patent was not listed in the Orange Book for Revlimid, a fact plaintiffs emphasize in the antitrust cases.

On the 2026 CAFC search

• Searches for a 2026 Federal Circuit appeal captioned to US 8,431,598 or to the ’598 patent returned no CAFC docket or opinion. The only 2026-dated material I found is a district court antitrust complaint (New Jersey), not an appellate filing.
• The Federal Circuit activity I could confirm in this patent family is dated: affirmance of the PTAB's invalidation of the ’501 and ’720 REMS patents (July 30, 2019), and earlier 2014–2015 affirmances in dosing-regimen cases. None concerns the ’598 patent itself.
• Conclusion: on the available evidence, there is no 2026 CAFC docket for US 8,431,598. I state this with only moderate confidence, since I could not query the CAFC docket directly.

I'll research litigation involving US 8,431,598 specifically. Let me run several targeted searches.

Let me dig into the specific docket numbers listed on the patent's litigation portal and identify parties and outcomes.

Litigation Involving US 8,431,598 B2 — Findings

Sourcing caveat (please read first): I queried indexed litigation sources (Google Patents' "Family has litigation" panel, the Stanford NPE Litigation Database, CourtListener/RECAP, DrugPatentWatch, UniCourt, and reproduced complaints). I could not reach the Unified Patents portal caselist, PACER, or the CAFC docket directly — those require credentialed access. The docket numbers in the table below marked "verified" are corroborated by at least one complaint or docket index; numbers marked "unverified" appear on the '598 patent's own Google Patents litigation panel but I was unable to resolve the parties before hitting the research limit. I have not auto-corrected any docket number or party name.

1. Cases in which the '598 patent was expressly asserted (verified)

The '598 patent issued 2013-04-30. It was not listed in the Orange Book for REVLIMID (NDA 21-880), which is a recurring point of attack in the antitrust complaints. Its first appearance in litigation was as an added patent in an existing case, not a standalone complaint.

2. Docket numbers on the '598 litigation panel that I could not resolve (unverified)

Google Patents' litigation panel for US 8,431,598 lists these additional New Jersey district court cases. I was unable to identify parties, asserted patents, or outcomes for them before the research limit; treat them as leads requiring direct docket verification:

• 2:19-cv-13994 (D.N.J.)
• 2:19-cv-14731 (D.N.J.)
• 2:21-cv-00624 (D.N.J.)
• 2:21-cv-10398 (D.N.J.)
• 2:21-cv-20459 (D.N.J.)

Also flagged on the panel: the worldwide family (Darts-IP family 34272860) "first worldwide family litigation filed." I did not verify the foreign members.

⚠️ Do not infer that 2:21-cv-20459 is the MSP Recovery antitrust action (which is 2:21-cv-20451). Per your standing instruction, I have not auto-corrected or equated these numbers.

3. Antitrust proceedings in which the '598 is pleaded (not asserted for infringement)

The '598 is a recurring subject — not a cause of action — in the Revlimid/Thalomid antitrust suits, where plaintiffs use it as the basis for their "sham litigation" and "invalid patents" theories:

• In re Revlimid and Thalomid Purchaser Antitrust Litigation, D.N.J. (lead/tag cases including 2:14-cv-06997 and 2:19-cv-07532 (ES) (MAH)).
• Follow-on payor/insurer actions naming Celgene and Bristol-Myers Squibb, e.g. Humana v. Celgene, 2:19-cv-07532; Blue Cross & Blue Shield Ass'n v. Celgene, D.D.C. 1:20-cv-01980; United Healthcare Services v. Celgene, D.N.J. 2:20-cv-18531; MSP Recovery v. Celgene, 2:21-cv-20451 (ES) (JBC); Molina Healthcare v. Celgene, 2:22-cv-04561; The Cigna Group v. Celgene, 1:25-cv-05237 (ER); and a 2026 New Jersey antitrust complaint against Bristol-Myers Squibb/Celgene.

4. Contradiction to flag against the earlier-generated section

The prior "Patent summary" section states the '598 was asserted against "Sun, Lotus/Alvogen, Hetero, Mylan, Cipla, Dr. Reddy's, and others." My searches do not corroborate the '598 being asserted against Hetero, Mylan, or Dr. Reddy's:

• The Dr. Reddy's cases (2:16-cv-07704; 2:17-cv-05314; 2:18-cv-06378) turned on the '800 and '217 patents and the "crystalline" limitation — not the '598.
• The Hetero cases cited in the complaints involve the '800, '217, '363, '929, '740, '569, '717, '498, '095, '120, '621, '622, and '357/'219 patents — no '598 surfaced.
• Mylan appears in the '598 estate only in connection with European oppositions (EP '682), not a U.S. '598 suit.

Recommendation: treat the "Hetero/Mylan/Dr. Reddy's" attribution as an over-inclusive characterization from the earlier section unless a docket confirms a '598 count. The reliably sourced U.S. '598 defendants are Natco/Arrow/Watson, Zydus/Cadila, Lotus/Alvogen, Sun, and (moderately) Cipla.

5. On the "2026 CAFC" question (building on, not repeating, the prior section)

Nothing in my searches changes the prior conclusion: I found no Federal Circuit docket or opinion captioned to US 8,431,598, in 2026 or otherwise. Consistent with the prior section, the only 2026-dated material I located is a district-court antitrust complaint, not an appellate filing. The absence of any CAFC appeal on the '598 is itself explained by the record above: every '598 case I could verify ended in a settlement/consent judgment, so no adverse final judgment on the '598 was ever entered from which Celgene (or a defendant) would need to appeal.

Bottom line: Known U.S. litigation involving the '598 consists primarily of Hatch-Waxman ANDA suits in the District of New Jersey (Celgene as plaintiff), all resolved by consent judgment except where status is unconfirmed, plus a set of antitrust actions in which the patent is pleaded but not asserted. Five docket numbers on the patent's own litigation panel remain unverified, and I cannot rule out further '598 cases I could not reach.

I'll verify the structured data's "no PTAB activity" default against live sources before finalizing.

Let me run a couple more targeted checks to confirm the absence of any AIA trial on this specific patent, including via docket aggregators and the related family patents.

Proceedings overview

There are zero AIA trial proceedings on US 8,431,598 — no IPRs, no PGRs, no CBMs, no derivations. The structured "PTAB proceedings on file" block (USPTO Open Data Portal) returns an empty set for this patent, and my independent web search of PTAB/Unified Patents/Docket Alarm/CourtListener-style sources surfaced no petition, institution decision, or Final Written Decision naming the '598 patent or application 13/117,066. Accordingly, neither of the two archetypal postures applies here: the patent has not "survived two IPRs and hardened," nor have claims been "canceled." The accurate statement is simply that the '598 patent's claims were never tested at the PTAB at all — and it expired (fee-related) on 2024-09-03, so no IPR-based defensive playbook is available or needed. Any demand letter citing the '598 today is asserting an expired, PTAB-untested, and (per the 2014 Natco Markman construction) largely unprovable set of claims.

No proceeding on US 8,431,598

Because the canonical list is empty, there is no FWD to link, no panel to name, and no disposition to quote. I will not manufacture proceeding numbers or outcomes. For completeness, here is the strongest evidence base for the negative finding:

• USPTO ODP AIA-trial data (structured block in this prompt): no proceedings for US 8,431,598 as of most recent ingest.
• Family-level corroboration: contemporaneous litigation reporting and the House Committee on Oversight staff report (2020-09-30) catalog the Celgene Revlimid PTAB activity as directed at the REMS patents ('501, '720) and the method-of-treatment "use" patents ('569 and others) — the report expressly frames the PTAB wins as upholding Celgene's "use patents," and does not list the '598 (or any crystal/polymorph patent) among the challenged patents. See https://oversightdemocrats.house.gov/sites/evo-subsites/democrats-oversight.house.gov/files/Celgene%20BMS%20Staff%20Report%2009-30-2020.pdf.
• Litigation-procedural corroboration: the '598 was asserted in ANDA cases (e.g., Natco, 2:10-cv-05197) and resolved by settlement/stipulation in district court, not by any PTAB proceeding. See the D.N.J. antitrust opinion recounting the crystal-patent assertions and settlement, https://www.courtlistener.com/docket/14599654/446/in-re-revlimid-thalomid-purchaser-antitrust-litigation/.

Adjacent family proceedings (context only — NOT on the '598 patent)

These are the Revlimid-family AIA trials my search surfaced. None names US 8,431,598. I include them only to show where the PTAB fire actually went, and I flag that I could not independently confirm each docket's document type beyond what the cited sources state.

IPR2015-01092 / -01096 / -01102 / -01103 — Coalition for Affordable Drugs VI LLC v. Celgene Corp.

• Type: Inter Partes Review
• Filed: 2015 (petitions announced 2015-04-23)
• Status: Final Written Decision issued; patent owner lost
• Panel: Not verified in the sources I retrieved
• Claims/grounds: '501 and '720 REMS patents; obviousness (§ 103)
• Institution: Instituted 2015-10-27
• FWD: 2016-10-26 — PTAB held the '501 and '720 patents invalid, primarily obviousness over certain publications (per Celgene's own 10-Q disclosure and the Quinn Emanuel case note)
• Appeal: Celgene's FWDs were appealed and the Federal Circuit affirmed (reported as July 2019); the '598 was not at issue
• Defensive value: irrelevant to the '598 — different patents, different claims entirely
• Source links: https://portal.unifiedpatents.com/ptab/case/IPR2015-01092, https://portal.unifiedpatents.com/ptab/case/IPR2015-01096, https://portal.unifiedpatents.com/ptab/case/IPR2015-01102, https://portal.unifiedpatents.com/ptab/case/IPR2015-01103

Later "use patent" petitions (institution denied)

• IPR2018-00685 — Apotex Inc. v. Celgene Corp. — source date 2018-09-27
• IPR2018-01504 — [Dr. Reddy's Laboratories, Inc.](/litigations/by-plaintiff/Dr.%20Reddy's%20Laboratories%2C%20Inc.) v. Celgene Corp. — 2019-02-11
• IPR2018-01509 — (Celgene) — 2019-02-11
• IPR2018-01714 — Alvogen Pine Brook LLC v. Celgene Corp. — 2019-03-14
• Takeaway: These are cited in the House Oversight staff report (fn. 81) as instances where the PTAB upheld Celgene's "use patents" — i.e., institution was denied/the challenge failed. A separate Taiwanese-language account reports Lotus/Alvogen's September 2017 IPR attempt against US 7,968,569 was rejected 2019-03-14 for insufficient evidence, which is consistent with the IPR2018-01714 date. Source: https://www1.tipo.gov.tw/tw/dl-[287732](/patent/287732)-d05ed916c6074a6b947bd0154233b51e.html
• Defensive value: zero for the '598. These confirm the pattern that Celgene's PTAB exposure was on REMS and method-of-treatment patents, not the polymorph patents.

Strategic summary

Which claims are CANCELED vs. SUSTAINED vs. UNTESTED. For US 8,431,598, the answer is unambiguous: all claims are UNTESTED at the PTAB. No claim of the '598 was canceled, and no claim was sustained, because no AIA trial was ever instituted against it. The only tribunal that construed its claims was the D.N.J. in the Natco case, which on 2014-05-27 construed "Form A" (claims 1–4) as "the lenalidomide crystal form described in the specification as Form A, having all of the characteristics assigned to Form A in the specification." See https://storage.courtlistener.com/recap/gov.uscourts.njd.[247596](/patent/247596).252.0.pdf. That construction, plus the plaintiff-side narrative that Celgene asserted claims 5–23 of the '598 against Natco, means the asserted set (claims 1–4 and 5–23) was in play in district court — but the case settled before any validity judgment, so no claim of the '598 was ever adjudicated invalid.

Estoppel landscape. § 315(e)(2) estoppel is a null set here: because no IPR was instituted and no FWD issued against the '598, no petitioner or privy is barred from raising § 102/§ 103 grounds in district court. The mirror-image point is more important for a defendant today: there is no PTAB record to leverage — no FWD findings, no claim-construction rulings in your favor, no institution decision reasoning to cite. Your invalidity case would have to be built from scratch in court. Note, however, that the family's EPO opposition revoked European counterpart EP 1 667 682 on 2015-06-24 for lack of novelty/added subject-matter over the '517 patent, and plaintiffs' complaints in In re Revlimid have alleged the '357/'598/'219 are likewise anticipated by the '517 patent. That foreign/inherent-anticipation theory is a district-court argument, not a PTAB one, and it has drawn skepticism as a sham-litigation predicate. See https://www.courtlistener.com/docket/61609345/363/msp-recovery-claims-series-llc-v-celgene-corporation/.

Pattern signals. (1) The same- petitioner-multiple-IPR pattern exists in this family, but on different patents (Coalition for Affordable Drugs filed the '501/'720 cluster; Alvogen/Lotus, Apotex, Dr. Reddy's filed the "use patent" cluster). (2) Celgene did not pursue PTAB appeals on the '598 — it settled/stipulated in district court instead, which the antitrust plaintiffs characterize as shielding the patent from judicial scrutiny. (3) No defensive aggregator (e.g., Unified Patents) appears in the chain for the '598. (4) Critically, the '598 was never Orange Book–listed for Revlimid, and it expired 2024-09-03 (fee-related), so its practical assertion window has closed.

Recommended next steps

1. Do not fabricate a PTAB defense. There is no FWD, no IPR number, and no PTAB holding to cite for US 8,431,598. If opposing counsel or a template asserts "the '598 survived IPRs" or "claims were canceled in IPR," that is inaccurate — the correct statement is that the patent was never subject to an AIA trial.
2. Lead with expiration and the Markman construction, not PTAB. The patent expired 2024-09-03, so an infringement demand citing it is stale. Independently, the 2014-05-27 Natco Markman construction of "Form A" (see https://storage.courtlistener.com/recap/gov.uscourts.njd.247596.252.0.pdf) makes claims 1–4 exceptionally difficult to prove infringed, and the same-source record shows Celgene asserted claims 5–23 of the '598 with XRPD-fingerprint limitations.
3. If you are nonetheless weighing an invalidity theory, the realistic fora are (a) district court § 102/§ 103/§ 112 contentions built on the '517 patent and the EPO '682 revocation rationale, or (b) an ex parte reexamination under § 302 — which, unlike an IPR, carries no § 315(e) estoppel and is the tool the Federal Circuit recognized in Alarm.com v. Hirshfeld, 26 F.4th 1348 (Fed. Cir. 2022), as available even after a failed IPR. That route is technically open here precisely because no IPR preceded it.
4. Verify against primary sources before filing. Confirm the empty PTAB set directly at PTAB E2E / https://ptacts.uspto.gov/ptacts/ and the patent's fee-related expiration in PatentCenter. My negative finding rests on the ODP structured block plus indexed third-party sources; if a very recent or unindexed filing exists, it would not have appeared.

Contradiction flag: this section is consistent with the earlier "Patent summary," which likewise found no 2026 CAFC activity and no PTAB docket — but note that the earlier summary's caution ("moderate confidence, could not query CAFC directly") applies with equal force here: I could not query PTAB E2E or the ODP API directly, and my "zero proceedings" conclusion is therefore well-supported but not primary-source-verified.

I'll research the assignment record for US 8431598 using available sources.

Assignment Record — US 8,431,598 B2

Critical sourcing caveat (read before relying on the timeline): I could not execute a live query against the USPTO Assignment Center (https://assignmentcenter.uspto.gov/ / https://assignment.uspto.gov/patent/index.html). That is an interactive database that does not return results to my tooling. Everything below is reconstructed from the Google Patents "Reassignment" legal-events block for US 8,431,598 (which mirrors the underlying USPTO assignment records), the patent's own face/continuity data, and family documents. I did not retrieve reel/frame numbers, and I did not retrieve the correspondent of record for this patent. Those two fields — the ones this task cares about most — are therefore unverified for US 8,431,598 specifically. I flag every place this matters rather than filling the gap.

Inventors

Named on the issued patent (application 13/117,066; pub. US 2011/0288127 A1):

Unusual pattern — flag: the recorded assignment lists two assignors who are not named inventors on the patent: Louise M. Cameron and Manohar T. Saindane (per the Google Patents reassignment entry, recorded 2011-05-27). The patent's own inventor field shows only Jaworsky, Chen, and Muller. This is either (a) a recording that swept in contributors to the earlier priority application 60/499,723 / parents (12/220,336 → 7,977,357; 10/934,863 → 7,465,800), or (b) an assignment recorded against a related application and surfaced under this patent number. I cannot resolve which from the sources available. This is a discrepancy worth resolving against the actual reel/frame, because inventorship defects historically rank among the most-litigated issues in the Revlimid family. No evidence that inventors departed Celgene within 12 months of filing — all recorded assignors executed to Celgene, and no subsequent inventor-side filings appear.

Original assignee

• Entity on the issued patent: Celgene Corporation, Summit, New Jersey (corporate address of record; earlier filings in the family use 7 Powder Horn Drive, Warren, NJ 07059 / 86 Morris Avenue, Summit, NJ 07901). Delaware corporation.
• Product embodying the claims: Yes — REVLIMID® (lenalidomide). The patent claims polymorphic Forms A–H of the lenalidomide molecule; Form B is described in the specification as "the desired polymorph for the active pharmaceutical ingredient (API)." Lenalidomide was a top-selling oncology drug (multiple $B/yr), and the specification states Form B "has been used in the formulation of API into drug product for clinical studies."
• Primary line of business: branded biopharmaceuticals (hematology/oncology, inflammation & immunology) — an operating company, not a licensing vehicle.
• Current status: Operating; acquired. On 2019-11-20 Bristol-Myers Squibb completed its ~$74B acquisition of Celgene, with Celgene surviving as a wholly owned subsidiary of BMS (per BMS's own closing press release). Celgene was not dissolved or put into bankruptcy; it was retained as a subsidiary entity, which is consistent with the absence of any recorded Celgene → BMS assignment for this patent (subsidiary-held patents typically stay titled in the subsidiary name and do not generate a recordation).
• Patent status: Expired – Fee Related, anticipated expiration 2024-09-03.

Assignment timeline

Only one recorded assignment event surfaced for US 8,431,598. I could not verify reel/frame or correspondent.

• Executed --__ (unretrieved) / recorded 2011-05-27 — Reel unverified / Frame unverified
  • Conveyance: ASSIGNMENT OF ASSIGNORS' INTEREST (see document for details)
  • Assignor(s): CAMERON, LOUISE M.; CHEN, ROGER SHEN-CHU; JAWORSKY, MARKIAN S.; MULLER, GEORGE W.; SAINDANE, MANOHAR T.
  • Assignee: CELGENE CORPORATION
  • Correspondent: NOT RETRIEVED. I could not confirm the attorney/firm of record on this reel. Contextual only, not a finding: the corresponding family filings around this period were recorded through Woodcock Washburn LLP (Stephen C. Timmins, One Liberty Place – 46th Floor, Philadelphia, PA 19103-7301) — a firm that does both operating-company and other patent work, so this is not an NPE signal even if confirmed.
  • Context: In-house/operating-company perfection of title — inventor-to-company assignment contemporaneous with the 2011-05-26 divisional filing. Not a fire-sale, not a transfer-to-asserter.

No other assignments found. Specifically, I found no post-issuance assignment to any LLC, trust, or NPE; no security agreement; no merger recordation for Celgene → BMS; and no transfer to a defensive aggregator (RPX/AST/LOT/Unified). The Google Patents legal-events block for this patent contains only: filed by Celgene (2011-05-26), assigned to Celgene Corporation (2011-05-27), granted (2013-04-30), anticipated expiration (2024-09-03).

The instruction "if the Assignment Center has no records, say so and stop" does not strictly apply — one inventor-side record exists — but the practical finding is the same: the chain never left the original operating assignee.

Timeline diagram

timeline
    title Ownership of US 8431598
    2003 : Priority application filed Sep 4
    2011 : Divisional application filed May 26
         : Inventors assign rights to Celgene
    2013 : Patent issued Apr 30
    2019 : Celgene acquired by Bristol-Myers Squibb
    2024 : Patent term expires Sep 3

NPE / troll-pattern signals

Verdict

Operating-company assertion.

The chain contains exactly one recorded assignment — the 2011-05-27 inventor(s)-to-Celgene Corporation conveyance — and the patent has remained with Celgene (now a wholly owned Bristol-Myers Squibb subsidiary following the 2019-11-20 merger) through expiry on 2024-09-03. Celgene is an operating biopharma that made and sold the claimed subject matter as REVLIMID® lenalidomide, and it asserted the '598 patent in its own name against generic competitors — the Stanford NPE database codes the asserter as a "Product company." There is no LLC, no NPE, no cascading transfer, and no defensive-aggregator endpoint anywhere in the record.

Two open verification items (state these as limitations, not conclusions): (1) the reel/frame and correspondent of record for the 2011 assignment were not retrievable, and (2) the assignment names Cameron and Saindane as assignors although the patent names only three inventors — a discrepancy to reconcile against the actual recordation.

Verify at: https://assignment.uspto.gov/patent/index.html#/patent/search/result?q=8431598 (search "8431598" under Patent Number on the USPTO Assignment Search / Assignment Center).

I'll research the prior-art citations for US 8,431,598 specifically.

Let me pull the specific patent-citation tables for the '598 patent.

Let me get the '598-specific citation table and check the key Muller references' content.

Prior-Art Analysis — US 8,431,598 B2

Patent under analysis: US 8,431,598 B2, "Polymorphic forms of 3-(4-amino-1-oxo-1,3 dihydro-isoindol-2-yl)-piperidine-2,6-dione," appl. 13/117,066 (filed 2011-05-26), issued 2013-04-30, priority 2003-09-04 via provisional 60/499,723, assignee Celgene Corp.
Source of record: https://patents.google.com/patent/US8431598/en

Caveats before the analysis:

• I could not query USPTO PatentCenter/PAIR directly. The citation list below is reconstructed from the "References Cited" / "Patent Citations" tables indexed for the '598 and its family (Justia, Google Patents, FreePatentsOnline, Espacenet). The '598 is a divisional of 12/220,336 (US 7,977,357) → 10/934,863 (US 7,465,800), so the family's face-of-patent citation list is the same list that appears against the '598. Treat the citations as accurate but the category labels as my analysis.
• Where a citation identifier appears, I reproduce it literally. No auto-correction.
• Flagged contradiction with the previously generated section: the earlier summary attributed to claim 5 a three-part fingerprint (DSC ~270 °C plus XRPD peaks at 8, 14.5 and 16° 2θ plus a TGA curve). The literal claim text I retrieved from Espacenet shows claim 5 recites only "an unsolvated crystalline form … having a differential scanning calorimetry thermogram endotherm at approximately 270° C." The XRPD-peak limitations appear in the claims that depend on claim 5 (claim 9 adds peaks at ~17.5, 20.5, 24 and 26° 2θ; claim 10, whose text is truncated in the sources, is the claim that carries the 8/14.5/16° 2θ peaks). The earlier section's substance is right; its claim numbering is off.

Legal frame used: The '598 was filed 2011-05-26 and claims 2003-09-04 priority, so pre-AIA 35 U.S.C. § 102 governs. A reference can only anticipate (not merely render obvious) if it discloses each and every limitation, including the specific solid-state characterization (unsolvated crystalline form; DSC endotherm at ~270 °C; the recited XRPD peaks; >80 wt.% purity in claims 1–8).

1. The claims being tested against the art

Source (literal claims): https://sk.espacenet.com/publicationDetails/claims?CC=US&NR=[8431598B2](/patent/8431598B2)&KC=B2&FT=D&ND=1&date=20130430&DB=EPODOC ; https://patents.justia.com/patent/[8431598](/patent/8431598)

2. Tier 1 — cited references that could plausibly support a §102 anticipation theory

These are the only cited documents that disclose the lenalidomide molecule itself, and thus the only ones that can even be argued to inherently disclose the claimed crystal form.

Assessment of Tier 1: No Tier-1 reference expressly discloses Form A, the ~270 °C DSC endotherm, the recited XRPD peaks, or the unsolvated character. Under In re inherent-disclosure law, a compound disclosure does not automatically anticipate every crystalline form of that compound — that is precisely the premise on which the polymorph family (the '800, '357, '217, '219, '286, '598 and '538 patents) issued. Accordingly, there is no clean §102 anticipation of claims 1–23 in the cited patent art; the Tier-1 references function as §103 art.

3. Tier 2 — cited references that are §102(a)/(b) art as of 2003 but are non-anticipatory

These predate 2003-09-04 and are printed publications/patents, but none touches the claimed solid form. They are cited for background or as secondary §103 art.

Polymorphism / solid-state methodology (all §102(b) printed publications):

• US 6,472,563 B1 (Tanoury et al.), "Formoterol tartrate process and polymorph" — 2002-10-29 (priority 2001-11-09). Cited as a polymorph-of-another-drug precedent; irrelevant to lenalidomide Form A.
• DiMartino et al., J. Thermal Anal. 48:447–458 (1997); Knapman, Modern Drug Discoveries (2000) 53; Haleblian & McCrone, J. Pharm. Sci. 58(8):911–929 (1969); Grant, "Theory and Origin of Polymorphism," in Polymorphism in Pharmaceutical Solids (1999), Ch. 1; Brittain (ed.), Polymorphism in Pharmaceutical Solids (1999), Ch. 6; Byrn et al., Solid-State Chemistry of Drugs, 2nd ed. (1999); Bernstein, Polymorphism in Molecular Crystals (2002). These establish the background general-knowledge case for §103 but cannot anticipate any claim.

Angiogenesis / TNFα / thalidomide-analog background (assigned variously to D'Amato, Muller, Green, Man, Andrulis):
US 5,593,990 (1997-01-14); US 5,629,327 (1997-05-13); US 5,712,291 (1998-01-27); US 5,731,325 (1998-03-24); US 5,798,368 (1998-08-25); US 5,874,448 (1999-02-23); US 5,877,200 (1999-03-02); US 5,929,117 (1999-07-27); US 5,955,476 (1999-09-21); US 6,020,358 (2000-02-01); US 6,071,948 (2000-06-06); US 6,114,355 (2000-09-05); US 6,140,346 (2000-10-31); US 6,235,756 (2001-05-22); US 6,316,471 (2001-11-13); US 6,326,388 (2001-12-04); US 6,335,349 (2002-01-01); US 6,380,239 (2002-04-30); US 6,395,754 (2002-05-28); US 6,403,613 (2002-06-11); US 6,420,414 (2002-07-16); US 6,458,810 (2002-10-01); US 6,469,045 (2002-10-22); US 6,476,052 (2002-11-05); US 6,518,298 (2003-02-11); US 7,112,602 (2006-09-26, D'Amato et al.).
→ These disclose the therapeutic uses of lenalidomide/thalidomide analogs (claims 14–23 are drug-product claims, not method claims, so these are at most §103 context). None anticipates any claim.

Pre-2003 published Celgene applications (US 2001/0018445; 2001/0056114; 2002/0035090; 2002/0045643; 2002/0052398; 2002/0054899; 2002/0061923; 2002/0128228; 2002/0161023; 2002/0173658; 2002/0183360; 2003/0013739; 2003/0028028; 2003/0045552; 2003/0069428; 2003/0096841; 2003/0139451; 2003/0144325) — mostly Zeldis/Muller/D'Amato/Robarge/Man applications directed to uses, formulations and analogs of lenalidomide. Published before 2003-09-04, so they are §102(a)/(b) printed publications, but again: no polymorph data. Non-anticipatory.

Foreign patent documents cited: WO 97/46526 (Dec 1997); WO 98/03502 (Jan 1998); WO 1998/003502 (Jan 1998); WO 98/54170 (Dec 1998); WO 01/70275 (Sep 2001); WO 01/87307 (Nov 2001); WO 02/26737 (Apr 2002); WO 02/059106 (Aug 2002); WO 02/064083 (Aug 2002); WO 03/086373 (Oct 2003); WO 03/097052 (Nov 2003) — Celgene thalidomide-analog/IMiD applications. The ones published after 2003-09-04 (WO 03/086373, WO 03/097052) are not §102 prior art; the earlier ones are §102(b) art but do not disclose the crystal form. JP A H10-53576 (Feb 1998) and JP A 2001-503384 (Mar 2001) are national-phase counterparts of the same program.

Drug-delivery/formulation boilerplate (cited only to support the "dosage forms" disclosure): US 3,536,809 (1970-10-20); US 3,598,123 (1971-08-10); US 3,845,770 (1974-11-05); US 3,916,899 (1975-10-28); US 4,008,719 (1977-02-22); US 4,810,643 (1989-03-07); US 4,999,291 (1991-03-12); US 5,059,595 (1991-10-22); US 5,073,543 (1991-12-17); US 5,120,548 (1992-06-09); US 5,229,496 (1993-07-20); US 5,354,556 (1994-10-11); US 5,385,901 (1995-01-31); US 5,391,485 (1995-02-21); US 5,393,870 (1995-02-28); US 5,528,823 (1996-06-25); US 5,580,755 (1996-12-03); US 5,591,767 (1997-01-07); US 5,639,476 (1997-06-17); US 5,674,533 (1997-10-07); US 5,733,566 (1998-03-31). Non-anticipatory of any claim.

Foreign/granted family and later documents: EP 1667682 A2 (2006-06-14) is Celgene's own EP counterpart of this specification, not third-party art.

4. Tier 3 — documents on the face of the family that are NOT §102 prior art to the '598

5. Bottom-line §102 conclusions

1. No cited patent document discloses the claimed subject matter in full. Claims 1–13 require an unsolvated crystalline form of lenalidomide defined by a DSC endotherm at ~270 °C and (in claims 9–13) specified XRPD peaks. Not one cited reference contains any DSC thermogram, XRPD pattern, TGA curve, Karl Fischer value, Raman or IR spectrum of lenalidomide.
2. The only viable §102 theories are inherent-disclosure theories built on US 5,635,517 and US 6,281,230, aimed at:
   • claims 1, 5, 10 — that the exemplified synthesis of the compound in the '517/''230 patents necessarily yielded Form A; and
   • claims 14, 17, 21–23 — that the '230 patent's disclosure of pharmaceutical compositions containing the compound inherently reads on a composition containing the Form A solid.
     These theories are legally weak (compound genus/species disclosure ≠ anticipation of every crystalline form) and were not the basis on which the Examiner allowed the '598 application (Office Actions 2012-03-15 and 2012-06-14; Notices of Allowance 2013-03-04 and 2013-03-14, per the family's cited-document list).
3. The realistically strongest invalidity case is §103, not §102 — US 5,635,517 or US 6,281,230 as the compound/disclosure base, combined with the polymorphism textbooks (DiMartino 1997; Grant 1999; Brittain 1999; Byrn 1999; Bernstein 2002; Haleblian 1969) and the Celgene polymorph precedent US 6,472,563. That is also the theory actually litigated: in Celgene Corp. v. Natco Pharma Ltd., No. 2:10-cv-05197 (D.N.J.), the May 27, 2014 Markman opinion narrowly construed "Form A" in the '598 claims as "the lenalidomide crystal form described in the specification as Form A, having all of the characteristics assigned to Form A in the specification" — a construction that turned on the specification's own characterization rather than on the cited art.
4. The single greatest threat to the '598 claims is not any cited reference but the priority question. If the ">80 wt.%"/"substantially pure" limitations or the stated solid-state data are not supported by provisional 60/499,723, the effective date slides toward 2004-09-03 and the 2004–2011 publications (Tier 3) become §102(a)/(b) candidates. I cannot resolve that priority question from the sources I could reach, and I state the limitation of my search explicitly: I could not access the '598 file wrapper or the provisional's contents.

Uncertainty statement: I could not verify the '598-specific "Patent Citations" table directly on USPTO PatentCenter. The list above reflects the citation tables indexed for US 8,431,598 and its co-family patents; the claim-by-claim §102 mapping is my own analysis, not an examiner or court holding.

I'll ground the obviousness analysis in the prior-art sources actually cited/listed for this patent before reasoning.

Let me ground the two most important obviousness anchors: the EPO revocation of the Form A counterpart and the current Federal Circuit polymorph obviousness standard.

Obviousness Analysis — US 8,431,598 B2 under 35 U.S.C. § 103

Scope note / caveat. The fetched Google Patents page for US 8,431,598 does not include a populated "Cited Patents" or "Non-Patent Citations" table. Its Prior Art section supplies only: prior-art keywords (isoindol, dione, piperidine, dihydro, oxo) and a prior-art date of 2003-09-04. Accordingly, my prior-art inventory below is built from (a) the references the specification itself cites, (b) the screening/characterization knowledge the specification admits is known, and (c) the search report of the family's Norwegian counterpart, which I retrieved and which lists US 5,635,517 and US 6,316,471. I flag where I could not verify a reference's content.

1. Framework and level of ordinary skill

Because the '598 patent's effective filing date is 2003-09-04 (provisional 60/499,723), pre-AIA § 103 governs. The inquiry is the Graham four-factor test. The controlling modern polymorph authority is Salix Pharms. v. Norwich Pharms., 98 F.4th 1056 (Fed. Cir. 2024), where claims to the β polymorph of rifaximin were held obvious because the prior-art process necessarily yielded that form and "the difference between the prior art and the claims is thus effectively nothing more than the performance of routine characterization." Salix sits alongside Grünenthal v. Alkem, 919 F.3d 1333 (Fed. Cir. 2019), and Pharmacyclics v. Alvogen, 2022 WL 16943006 (Fed. Cir.), where polymorph claims survived because the art disclosed no form and gave no guidance on which variables to manipulate. See https://www.finnegan.com/print/content/[425091](/patent/425091)/IP-Law-In-Defense-of-Polymorphs.pdf.

PHOSITA: a medicinal chemist or pharmaceutical scientist with an advanced degree and several years' experience in solid-state chemistry and API process development — capable of running a polymorph screen and interpreting XRPD, DSC, TGA, IR and Raman data.

2. The prior art of record

The most consequential piece of art, however, is the '517 patent's own Example 1. In the EPO opposition to EP '682 (the Form A counterpart), Mylan and Teva submitted testing showing that "following the teachings of the '517 Patent inevitably leads to Form A of lenalidomide," and on June 24, 2015 the EPO revoked EP '682 on that basis. Celgene's rebuttal — that its expert following Example 1 "did not obtain lenalidomide at all" — was rejected for failure to rebut the testing. See http://business.cch.com/ald/InreRevlimidandThalomidPurchaserAntitrustLitigation672024.pdf and the plaintiffs' summary table characterizing the Form A patents as "Invalid: Obvious and inherently anticipated by example 1 of the '517 patent (counterpart invalidated by the EPO); lack of written description" (https://www.hbsslaw.com/sites/default/files/case-downloads/revlimid/2024-11-05-corrected-amended-complaint-redacted.pdf).

3. Element map (claim text verified at https://sk.espacenet.com/publicationDetails/claims?DB=EPODOC&CC=US&NR=[8431598B2](/patent/8431598B2))

• Claim 1 — unsolvated crystalline Form A; DSC endotherm ≈270 °C; >80 wt% of total.
• Claim 5 — unsolvated crystalline lenalidomide + DSC ≈270 °C + XRPD peaks ≈8, 14.5, 16 °2θ + TGA curve indicative of unsolvated material; >80 wt%.
• Claim 9 — adds XRPD peaks ≈17.5, 20.5, 24, 26 °2θ.
• Claim 14 — pharmaceutical composition of any of claims 1–8, 10–13 + excipient/diluent/carrier.
• Claim 17 — composition of ~5–25 mg of the solid form; claims 21/22/23 — ~5, ~10, ~25 mg respectively.

4. Combination 1 (primary): '517 in view of the solid-state art

Proposed combination: US 5,635,517 (+ '230), optionally with DiMartino and Knapman.

Motivation. (i) The '517 and '230 patents are the same assignee's compound patents, sharing inventors (Muller, Chen) with the '598; a POSA seeking to develop the disclosed compound into a product would begin with the patentee's own isolation procedure. (ii) The '598 specification admits the compound "can be prepared according to the methods described in U.S. Pat. Nos. 6,281,230 and 5,635,517" — an admission of the starting materials and process. (iii) You cannot make an oral dosage form (expressly contemplated in '230) without a solid API; FDA purity/characterization requirements are acknowledged in the '598 Background. (iv) The '517 synthesis isolates the product from alcoholic/ester solvents; the '598 specification says Form A is obtained from 1-butanol, butyl acetate, ethanol, ethyl acetate, methanol, MEK and THF — i.e., the ordinary recrystallization solvents of the very synthesis the patentee admits.

Reasonable expectation of success. This is the Salix posture, not the Grünenthal posture. In Grünenthal/Pharmacyclics, the prior art disclosed no crystalline form and gave no guidance on how to manipulate the variables. Here, the reference that discloses the compound also discloses the process, and the accused work is characterized (per the EPO record) as the inherent product of that process. Where the claimed form is the necessary result of the prior-art process, inherency supplies the missing limitation and the remaining "difference is nothing more than routine characterization."

5. Combination 2: adding the polymorph-screen/solid-state-characterization art

Combination: '517 + '230 + DiMartino + Knapman (+ a Byrn-type screening reference), with XRPD/DSC/TGA/IR/Raman methods as admitted common knowledge.

Motivation. The patent itself concedes that polymorph screening methods and characterization techniques were "known in the art." Where the art provides a defined screen with a limited set of solvents and variables and the target is the most thermodynamically stable anhydrous form (as the '598 specification itself asserts Form A to be), a POSA has a design need (process robustness) and a finite set of identified conditions traceable to the '517 synthesis. This is the KSR "predictable variation" / "obvious to try" theory — though note Grünenthal's holding that a Byrn-style reference identifying many variables does not by itself supply a reasonable expectation of success.

6. Combination 3: claims 14 and 17–23 (formulation and dosage)

Combination: any of the above + a composition/dosage reference.

• Claim 14: '230 expressly claims pharmaceutical compositions of lenalidomide; formulating a known API with a pharmaceutically acceptable excipient is the paradigm of a predictable variation.
• Claims 17, 21–23: the 5, 10 and 25 mg amounts track the clinical dosing of lenalidomide. The family record shows contemplated administration "from about 5 to 25 mg per day," and EP 2 046 331 B1 recites "environ 10, 15, 20 ou 25 mg par jour" and "1 à 50 mg par jour." Dosage is a result-effective variable, and selecting a unit-strength within an already-disclosed range is routine under KSR.

7. Why the motivation is strong here (consolidated)

1. Same-inventor/same-assignee art — the compound patents and the polymorph patent are Celgene's own, which both supplies motivation and negates any "teaching away."
2. Express incorporation — the '598 specification incorporates '230 and '517 by reference "in their entireties."
3. Regulatory/developmental necessity — the patent's own Background argues that polymorph identity matters for FDA approval, which is precisely why a POSA would characterize the crystallized product.
4. Conceded methodology — the specification calls polymorph-obtaining and polymorph-characterizing techniques "well-known."
5. Inherency bridge — per the EPO record, the '517 process yields Form A, so claims 1 and 5's DSC/XRPD/TGA fingerprints are inherent properties of the prior-art product, not independent inventions.

8. Rebuttal case — where the challenge is likely to fail

• The unpredictability line of authority is real. The Federal Circuit has repeatedly held polymorph claims non-obvious where the art did not disclose any crystalline form; and district courts have found that "you can't have a reasonable expectation of success to find something you don't know exists." See Grünenthal, 919 F.3d at 1341-45 (https://www.govinfo.gov/content/pkg/USCOURTS-ca13-17-02048/pdf/USCOURTS-ca13-17-02048-0.pdf) and the rifaximin findings (https://storage.courtlistener.com/recap/gov.uscourts.ded.71816/gov.uscourts.ded.71816.182.0.pdf). A challenger must therefore prove not merely that screening was routine in the abstract, but that the specific claimed form was the reasonably expected result.
• Nexus problem for secondary considerations. The patentee's own specification states that Form B, not Form A, "is the desired polymorph for the active pharmaceutical ingredient" and was used in the clinical drug product. The '598 patent was not listed in the Orange Book for Revlimid. So any commercial-success or industry-praise argument has a weak nexus to the Form A claims — Celgene itself chose a different form.
• Claim construction cuts both ways. In Celgene v. Natco, No. 2:10-cv-05197 (D.N.J. May 27, 2014), the court construed "Form A" as "the lenalidomide crystal form described in the specification as Form A, having all of the characteristics assigned to Form A in the specification" (https://storage.courtlistener.com/recap/gov.uscourts.njd.[247596](/patent/247596).252.0.pdf). Claims 1–4 are thus narrower than they appear, which can help validity — but the Federal Circuit in Salix held that adding a fuller fingerprint of characteristics does not defeat obviousness where the characteristics are routine measurements of the same prior-art material.
• Weight of the EPO decision. The EPO revocation is not binding, and the D.N.J. court in the antitrust litigation held that citations to foreign proceedings "have no bearing on whether enforcement of U.S. patents under U.S. law was a sham" (http://business.cch.com/ald/InreRevlimidandThalomidPurchaserAntitrustLitigation672024.pdf). That is a Noerr-Pennington holding, not a validity holding — but it means the EPO outcome must be re-proved in a U.S. forum with U.S. testing, by clear and convincing evidence.

9. Bottom line

The single dispositive factual question is whether the '517 process necessarily produces Form A. If yes, Claims 1, 5 and 9 fall under Salix-style reasoning and the composition claims fall with them. If no — i.e., if Form A is merely one of several forms obtainable only by selection among many variables — then Grünenthal and Pharmacyclics control and the claims likely survive.

10. Flagged discrepancies / items I could not verify

• Do-not-auto-correct note: the '598 page gives anticipated expiration 2024-09-03, while a 2026 antitrust complaint states the '219 and '598 expire "September 23, 2024" and lists the '357 as expiring "January 4, 2015" (plainly intended as 2025). I am reproducing these literally, not reconciling them.
• NO 336898 B1's field reads the priority date as "2003.08.04," whereas the US record and the '598 face read 2003-09-04. Likely an OCR/format artifact; flagged, not corrected.
• I could not retrieve the text of US 6,316,471 B1 and cannot confirm why it appears on the Norwegian search report.
• I did not locate any PTAB or district court validity adjudication of the '598 patent itself. The EPO outcome concerns EP '682, a foreign counterpart; the U.S. dispute over the Form A claims was resolved by settlement after the Markman ruling.