Merck Sharp & Dohme LLC v. Prinston Pharmaceutical Inc.

I'll research this case thoroughly before drafting the overview.

Let me dig deeper into the MDL context, IPR outcomes, and the settlement.

Case Overview and Background

Merck Sharp & Dohme LLC v. Prinston Pharmaceutical Inc., No. 1:22-cv-01071-RGA (D. Del.), is a Hatch-Waxman (ANDA) infringement action filed August 15, 2022, before U.S. District Judge Richard G. Andrews. Plaintiff Merck Sharp & Dohme LLC is the Merck & Co., Inc. operating subsidiary that holds NDA No. 021995 for JANUVIA® (sitagliptin phosphate) tablets, the first-in-class DPP-4 inhibitor for type 2 diabetes. This is the classic brand-versus-generic posture: a research-based pharmaceutical company defending the last remaining Orange Book patent on a blockbuster product against a Paragraph IV challenger. Defendant Prinston Pharmaceutical Inc. is a Delaware-incorporated generic manufacturer based in Cranbury, New Jersey, and is a U.S. affiliate of Zhejiang Huahai Pharmaceutical Co., Ltd. (Shanghai Stock Exchange: 600521), whose U.S. group also includes Huahai US Inc. and Solco Healthcare LLC (the relationship is described in Merck's own parallel pleadings and in Huahai's corporate filings; see e.g. RPX litigation document). Merck is represented in Delaware by Daniel M. Silver and Alexandra M. Joyce of McCarter & English LLP; Prinston by Dominick T. Gattuso of Heyman Enerio Gattuso & Hirzel LLP (Justia docket).

The accused conduct is Prinston's submission of ANDA No. 216886 seeking FDA approval to market generic sitagliptin phosphate oral tablets (25/50/100 mg) before expiration of the asserted patent. Merck's complaint pleads infringement under 35 U.S.C. § 271(e)(2) and seeks a declaratory judgment of infringement, predicated on Prinston's July 1, 2022 Notice Letter; the docket reports a thirty-month stay deadline of January 1, 2025, and a patent expiration of November 24, 2026 (Complaint, D.I. 1). Notably, Huahai publicly disclosed in October 2024 that ANDA 216886 had received tentative approval — i.e., FDA review complete but final approval withheld pending patent expiry — confirming the patent is the operative barrier to launch (Huahai SSE announcement, Oct. 2024).

The sole patent asserted is U.S. Patent No. 7,326,708, "Phosphoric Acid Salt of a Dipeptidyl Peptidase-IV Inhibitor" (Cypes et al., issued Feb. 5, 2008; June 24, 2003 priority). In one line: it claims the 1:1 (monobasic) dihydrogenphosphate salt of sitagliptin — the specific salt form in JANUVIA® — and, in dependent claims, the crystalline monohydrate of that salt characterized by X-ray powder diffraction, solid-state NMR, TGA and DSC data (see Google Patents; claim construction, 19-md-2902, D.I. 135). It is a salt/polymorph patent, not a compound patent — the sitagliptin compound itself is covered by the earlier U.S. Patent No. 6,699,871, also Orange Book–listed for JANUVIA and JANUMET.

Procedural posture and venue. This case is a follow-on wave of the sitagliptin MDL: the court's docket reflects that the MDL Office was notified of a related case, and the October 7, 2022 stipulation extending Prinston's response deadline was entered jointly with the MDL, In re Sitagliptin Phosphate ('708 & '921) Patent Litigation, No. 1:19-md-02902-RGA (D.I. 8). That MDL consolidated fourteen defendant groups sued in 2019–2020 over the '708 patent (and, for five of them, U.S. Patent No. 8,414,921 on sitagliptin/metformin formulations) as they sought to launch generic JANUVIA®, JANUMET® and JANUMET XR®. Delaware was the natural forum: Prinston is a Delaware corporation (so venue and personal jurisdiction are uncontested under § 1400(b)), virtually every generic sitagliptin filer was already before Judge Andrews, and the MDL framework meant this case was effectively assigned as a tag-along to a judge deeply familiar with the technology. I note that the District of Delaware has no formal divisions; the "1:" prefix denotes the Wilmington courthouse. Prinston's case appears to have run in parallel with a companion Prinston action on the same patent, No. 1:22-cv-01300 (D. Del.), filed October 3, 2022 and closed by a negotiated consent judgment on February 17, 2023 (Patsnap litigation record). Caveat: I could not retrieve a post-October-2022 PACER docket entry showing the specific termination order for 22-cv-01071 itself; the "settled" status in the case metadata is consistent with the consent-judgment pattern used across this MDL, but the precise termination docket number for this case is not verified here.

Why the case is notable. Three things make it more than a routine ANDA suit. First, the '708 patent survived a concerted IPR attack — a rarity for a late-expiring salt-form patent that is often the practical gatekeeper for generic entry. Mylan led IPR2020-00040 (petition filed Oct. 30, 2019; instituted May 12, 2020), with Teva/Watson (IPR2020-01045), Dr. Reddy's (IPR2020-01060) and Sun (IPR2020-01072) as "me-too" joinder petitioners. The Board's Final Written Decision of May 2021 held no challenged claim unpatentable, rejecting the argument that Merck's own earlier WO 03/004498 inherently disclosed the 1:1 sitagliptin dihydrogenphosphate salt (FWD; institution decision). Teva, Sun and Dr. Reddy's noticed appeals in July 2021; I was not able to verify the Federal Circuit's disposition of those appeals in this research, so the appellate outcome should be treated as an open item. Because the IPR failed, generic sitagliptin entry remains blocked until the '708 patent expires — November 24, 2026, extended to May 24, 2027 with pediatric exclusivity — which is precisely why every remaining filer, including Prinston, resolved by consent judgment with agreed entry dates rather than by trial. Second, the commercial stakes are enormous: Huahai's own disclosure cites roughly $5.7 billion in U.S. sitagliptin sales for 2023 (IQVIA data), and the brand franchise was still essentially monopoly-protected at the time Prinston filed. Third, the case illustrates the mature-stage Hatch-Waxman assertion pattern: a patentee that has already won its IPR and settled most of an MDL uses serial, individually captioned ANDA suits against late-arriving filers to impose the same consent-judgment template, conserving the "hard" test case for the lead defendants. It also sits against the backdrop of Zhejiang Huahai's separate U.S. legal exposure in the valsartan/NDMA litigation — unrelated to this patent case, but relevant to assessing Prinston's corporate parent. Finally, the practical effect of the MDL-plus-IPR combination is that the '708 patent has become a rare example of a secondary salt/polymorph patent doing the exclusivity work that a compound patent normally does.

I'll research the docket and related proceedings before drafting the chronology.

Let me dig into the post-2022 docket and the companion case's consent judgment.

Let me look for the specific docket for 22-cv-01071 on CourtListener and check whether a consent judgment was entered.

Key Legal Developments and Outcome

Research caveat up front. The publicly indexed docket for this case (Justia, UniCourt, Docket Alarm) stops at 2022-10-07 (D.I. 8); PACER-only activity after that date is not visible in the free sources I could reach, and I was unable to retrieve a termination order for this docket number by document number. The chronology below therefore distinguishes sharply between (a) docket events I can cite, (b) the closely analogous companion case where the paper trail is public, and (c) well-sourced patent-level facts (PTAB, MDL, FDA) that explain the litigation's trajectory. Nothing below conflicts with the case metadata (D. Del., No. 1:22-cv-01071, '708 patent, status: settled).

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1. Filing and initial pleadings (2022)

On answer and counterclaims: the public docket shows no answer or counterclaims in this action. In the companion case (below) Prinston likewise never answered before a consent judgment resolved the case. Given the "settled" status and the pattern, the most likely reading is that Prinston obtained an extension of its response deadline (consistent with the MDL template) and the case resolved by negotiated judgment before a pleading on the merits was filed. I cannot verify from the free sources whether an answer/counterclaim was ever filed in 22-cv-01071 — treat that as an open item.

2. The companion Prinston action and the "template" (2022–2023)

Two weeks after this suit, Merck filed a second, separately captioned Prinston action on the same '708 patent, No. 1:22-cv-01300-UNA (D. Del.), on 2022-10-03, this one arising from ANDA No. 216885 (generic JANUMET®, sitagliptin/metformin HCl) and an August 19, 2022 notice letter (complaint text via Bloomberg Law; Patsnap case record).

That companion case closed on 2023-02-17 by consent judgment — 137 days after filing, before any Markman or dispositive motion practice. The recorded recital is the standard Merck-MDL settlement template: "the parties … have agreed to terms and conditions representing a negotiated settlement … hereby stipulate and consent to entry of judgment and an injunction", defining a "Prinston Product" as the drug product sold pursuant to the specified ANDA (Patsnap verbatim record, 1:22-cv-01300). This is directly relevant here: it establishes (i) that Prinston was resolving both its sitagliptin ANDAs by negotiated judgment in early 2023, and (ii) the exact consent-judgment architecture Merck used against every remaining sitagliptin filer.

3. Pre-trial motions of substance, Markman, discovery

In this case: none reached. The docket shows no motion to dismiss, transfer, stay pending IPR, or summary judgment, and no scheduling order for Markman or discovery, before the public record goes dark in October 2022. Given the companion case disposed of a same-patent, same-defendant dispute in under five months, the most defensible conclusion is that 22-cv-01071 did not reach claim construction, expert discovery, or trial — it was overtaken by settlement.

Patent-level context that made motion practice unnecessary. The substantive groundwork was already done elsewhere:

• Claim construction of the '708 patent occurred in the MDL, not here — In re Sitagliptin Phosphate ('708 & '921) Patent Litigation, No. 1:19-md-02902-RGA (D. Del.) (see the MDL claim-construction opinion at 19-md-2902, D.I. 135).
• The Bellwether trial was Merck v. Mylan Pharmaceuticals, No. 1:19-cv-00101-IMK (N.D. W. Va.) (transferred/coordinated with the MDL). Four-day bench trial in December 2021; September 2022 post-trial opinion holding that Mylan infringed both the '708 and '921 patents and that both were valid; final judgment entered for Merck under § 271(e)(4)(A) barring FDA approval before patent expiry (Mylan Rule 62.1/indicative-ruling filing, D.I. 205).
• Mylan appealed, then settled on 2023-03-14, agreeing to a license with an entry date before patent expiry; the parties sought a Rule 62.1 indicative ruling to modify the final judgment and then a Rule 12.1 remand and voluntary dismissal of the appeal (same filing; summarized in Salud y Fármacos / Endpoints, May 2023).

This matters to 22-cv-01071 in two ways: it confirms the '708 patent had been adjudicated valid and infringed (trial-level) before Prinston's case matured, and it shows Viatris/Mylan — the one defendant that actually litigated — bought its way in with a pre-expiry licensed entry date. Prinston's settlement almost certainly followed the same commercial logic.

4. Trial, verdict, post-trial motions

None in this case. No verdict, no JMOL/new-trial motion, no § 285 fee motion appears in the public docket. The only § 285 demand is the boilerplate prayer for relief in the complaint (D.I. 1 at prayer ¶ (i)).

5. Final disposition / present posture

Settled. The case metadata records status "settled," and Prinston's own parent-company conduct corroborates a patent-expiry-capped resolution:

• Huahai's SSE disclosure of 2024-10-08/09 states that ANDA No. 216886 received FDA tentative approval — i.e., FDA completed all generic review requirements but withheld final approval "由于专利权或专卖权未到期" (because the patent/exclusivity had not expired), and that Prinston can only market after patent expiry and final FDA approval (SSE announcement; Shanghai Securities News). A tentative approval with no final approval is the signature of a settled ANDA case with an agreed post-expiry (or licensed) entry date.
• The Huahai filing confirms the exclusivity runway: sitagliptin U.S. sales of ~$5.7 billion in 2023 and only the originator product on the U.S. market.

Key dates that frame entry: '708 patent expiry 2026-11-24, extended by pediatric exclusivity to 2027-05-24; Merck's own investor disclosures state that, as a result of settlements with generics on the later-expiring salt/polymorph patent, JANUVIA/JANUMET lost U.S. market exclusivity in May 2026 and JANUMET XR in July 2026 ([Merck 10-Q disclosure

I'll research the plaintiff's counsel of record, building on and verifying the names already identified in the prior section.

Let me verify the signature block on the complaint and check whether Hogan Lovells (Merck's MDL co-counsel) appeared in this specific case.

Let me pull the CourtListener/RECAP docket and the complaint's signature block to confirm exactly who appeared in this case.

Plaintiff's Counsel of Record — Merck Sharp & Dohme LLC

Summary of what the docket actually shows

For 22-cv-01071-RGA itself, the public docket identifies exactly two attorneys of record for the plaintiff, both at McCarter & English's Wilmington, Delaware office. The complaint was filed by McCarter ("The plaintiff is represented by McCarter & English, LLP" — Law Street Media), and the docket's plaintiff-attorney field lists only Silver and Joyce (Justia docket; UniCourt). D.I. 7 (Summons Returned Executed, filed 9/20/2022) was signed by Silver, which is the only plaintiff-side filing in the case.

Plaintiff's counsel of record in this case

Both are Delaware-barred McCarter attorneys performing the classic local/Delaware-counsel function, with substantive national lead counsel drawn from Merck's other outside firms (below). The docket does not designate a "lead counsel" label for this case (D. Del. CM/ECF does not carry the "LEAD ATTORNEY" flag in the Justia/UniCourt renderings).

Merck's broader counsel team in the related proceedings (not confirmed on this docket)

Because 22-cv-01071 was a tag-along to the sitagliptin MDL, the team that prosecuted the '708 patent on the merits elsewhere is instructive — but I want to be precise that I could not verify any of these attorneys entered an appearance in 22-cv-01071:

Important verification caveats

1. No post-October-2022 docket data. Both Justia and UniCourt render the docket as last retrieved October 7 / October 14, 2022 — i.e., after only D.I. 8. Any later appearances (additional McCarter, Williams & Connolly, or in-house attorneys), and the termination/consent-judgment entry, are not reflected in the sources I could reach. The prior section's caveat that the specific termination order for this case is unverified stands; I could not retrieve a CourtListener RECAP docket sheet for 22-cv-01071 to check for a later notice of appearance.
2. The Astellas/Hogan Lovells mix-up risk. You will find McCarter (Silver/Joyce) + Hogan Lovells US LLP (Simon D. Roberts, Jason A. Leonard, Nitya Anand, Chika S. Seidel, Vincent Li, Celine Jimenez Crowson) signing together in D. Del. litigation against Prinston. That is the Astellas mirabegron (MYRBETRIQ®) case (20-cv-01589-JFB-CJB), not a Merck engagement — Astellas, not Merck, was the Hogan Lovells client there. Hogan Lovells should not be listed as Merck's counsel in this case. (Confusingly, in one Aug. 2022 MDL meet-and-confer report the lead counsel designation for the Astellas plaintiffs had migrated to McDermott Will & Emery, with Joyce still Delaware counsel — again a different matter.)
3. Correction to the prior section, minor. The earlier overview says Merck is represented by "Daniel M. Silver and Alexandra M. Joyce of McCarter & English LLP" — that is verified as the complete plaintiff's-counsel roster on this docket. What should be added is that in the parent MDL the McCarter team sat beneath Williams & Connolly as national trial counsel and Michael P. Kelly as the docket-designated lead. Whether that full team (or any of it) formally appeared in 22-cv-01071 before settlement is unverified.
4. Defendant's counsel (for completeness only): Dominick T. Gattuso, Heyman Enerio Gattuso & Hirzel LLP, Wilmington, DE — the only defendant attorney on the 22-cv-01071 docket and the filer of D.I. 8.

I'll research Prinston's counsel of record in this matter, building on the reference to Dominick T. Gattuso in the earlier section.

Let me dig into the specific docket entries and any "of counsel" appearances for Prinston in this case.

Let me check the full docket and Gattuso's firm profile and confirm whether any pro hac vice (of counsel) attorneys appeared.

Counsel of Record for Defendant Prinston Pharmaceutical Inc.

Summary finding

The verified counsel of record for Prinston Pharmaceutical Inc. in Merck Sharp & Dohme LLC v. Prinston Pharmaceutical Inc., No. 1:22-cv-01071-RGA (D. Del.) is a single Delaware attorney: Dominick T. Gattuso of Heyman Enerio Gattuso & Hirzel LLP (HEGH), Wilmington. Both Justia's docket sheet and UniCourt's case profile — the two independent docket aggregators that carry this case's attorney field — list Gattuso as the only defendant-side attorney, matched against Merck's Daniel M. Silver and Alexandra M. Joyce (Justia docket; UniCourt). This is consistent with, and does not contradict, the earlier section's statement that Gattuso represented Prinston here.

Verified counsel of record

The entirety of the defense-side appearance in the retrievable docket runs through Gattuso: the answer deadline was extended by the D.I. 8 stipulation he filed, and the docket (as last captured Oct. 7, 2022) closes there.

Of counsel / non-Delaware counsel — not confirmed in this case

Unlike the companion and MDL cases, I could not verify any pro hac vice admission or "of counsel" entry on the 22-cv-01071 docket. I flag the following as the standard Prinston defense team in parallel matters, which may also have been behind this case but did not appear of record in any docket snapshot I retrieved:

• Hyman, Phelps & McNamara, P.C. (Washington, D.C.) — William A. Rakoczy, Lara E. FitzSimmons, Rachel Pernic Waldron, and Steven J. Birkos. These four were admitted pro hac vice for Prinston in the related Bayer/Janssen v. Prinston, No. 1:24-cv-00336-RGA (D. Del.), via a motion filed by Gattuso and granted May 9, 2024 (Patexia document list). Rakoczy/FitzSimmons likewise appear as Prinston's of-counsel signatories in other ANDA defenses. This is the firm that functions as Prinston's national Hatch-Waxman counsel; its absence from the 22-cv-01071 appearance record is best explained by the case's very short life (it settled), not by any indication it was uninvolved.
• Other Prinston counsel seen in different matters — Haynes and Boone LLP (Kyle Musgrove, Scott Cunning) in the Brisdelle suit; Daignault Iyer LLP (Ronald M. Daignault, Richard Juang) after leaving Goldberg Segalla; Stamoulis & Weinblatt (Stamatios Stamoulis) in the Astellas/Mirabegron MDL — are not shown appearing in this case and should not be attributed to it.

In-house counsel

There is no in-house counsel of record for Prinston on this docket. As is standard in Delaware ANDA practice, corporate/regulatory counsel (Huahai/Prinston legal) would not enter an appearance.

Important limitations — please read

1. Docket snapshot is stale. Justia's sheet was last retrieved Oct. 7, 2022, and UniCourt's data was last updated Oct. 14, 2022 — both showing only D.I. 1–8. Because the case is recorded as settled (and its companion, No. 1:22-cv-01300, was closed by consent judgment on Feb. 17, 2023), any later filings — including a pro hac vice motion, a notice of appearance, or the termination order — would fall after the last captured docket date and are not visible in my research. I therefore cannot rule out that additional counsel entered after October 2022.
2. No PACER pull. I was unable to retrieve a live, current PACER docket sheet for 22-cv-01071 itself; the aggregator listings may not be complete. If a definitive answer is needed, a current PACER/RECAP pull is required.
3. No contradiction with prior sections. The earlier section's statement that "Prinston [is represented] by Dominick T. Gattuso of Heyman Enerio Gattuso & Hirzel LLP" is confirmed. One minor inconsistency within the sources: HEGH's Wilmington address appears as 300 Delaware Avenue, Suite 200 in the Justia/Bloomberg listings and in HEGH's own Delaware filings, but a 2026 HEGH filing in an unrelated Hikma matter lists 222 Delaware Avenue, Suite 900 (archive.org docket copy). I could not resolve whether this reflects a firm relocation or a filing variance; for the 2022 period relevant here, 300 Delaware Avenue, Suite 200 is the address of record.

Bottom line: For this case, the answer is one attorney — Dominick T. Gattuso (HEGH, Wilmington), Delaware/lead counsel of record — with no verified pro hac vice or in-house appearances in the retrievable record.