PTAB

IPR2020-01060

DR Reddy's Laboratories Inc v. Merck Sharp & Dohme Corp

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1. Case Identification

2. Patent Overview

  • Title: Phosphoric acid salt of a dipeptidyl peptidase-IV inhibitor
  • Brief Description: The ’708 patent is directed to the dihydrogenphosphate salt of sitagliptin, a potent inhibitor of dipeptidyl peptidase-IV (DP-IV) useful for treating Type 2 diabetes. The claims cover the salt, its specific (R) and (S) stereoisomers, a crystalline monohydrate form, and related pharmaceutical compositions and methods of treatment.

3. Grounds for Unpatentability

Ground 1: Anticipation by WO ’498 - Claims 1-3, 17, 19, and 21-23 are anticipated by WO ’498.

  • Prior Art Relied Upon: WO ’498 (International Publication No. WO 03/004498).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that WO ’498, which the ’708 patent’s specification admits is prior art, discloses every element of the challenged claims. WO ’498 explicitly claims sitagliptin and its "pharmaceutically acceptable salts thereof" as one of 33 compounds in its claim 15. The specification of WO ’498 further provides a finite list of eight "particularly preferred" acids for salt formation, which explicitly includes "phosphoric." Petitioner contended that the combination of a primary, closed list of compounds (including sitagliptin) and a secondary, closed list of preferred salt-formers (including phosphoric acid) constitutes a direct and unambiguous disclosure of sitagliptin phosphate. This disclosure was argued to anticipate claim 1. Further, WO ’498 was asserted to teach the claimed (R)-configuration (anticipating claim 2), teach that both optical isomers are within the invention's scope (anticipating claim 3), and disclose the claimed pharmaceutical compositions, methods of treatment, and processes for making the salt (anticipating claims 17, 19, and 21-23).

Ground 2: Anticipation by the ’871 Patent - Claims 1-3, 17, 19, and 21-23 are anticipated by the ’871 patent.

  • Prior Art Relied Upon: The ’871 patent (Patent 6,699,871).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that the ’871 patent is prior art under 35 U.S.C. § 102(e)(2) because its application was filed before the invention date of the ’708 patent. The petition highlighted that the specifications of the ’871 patent and WO ’498 are identical in all material respects, as they both claim priority to the same provisional application. Therefore, Petitioner argued that the ’871 patent inherently provides the same anticipatory disclosure as WO ’498. It teaches (R)-sitagliptin and its pharmaceutically acceptable salts and separately lists phosphoric acid as a "particularly preferred" acid for salt formation. For the same reasons articulated in Ground 1, this disclosure was argued to anticipate claims 1-3, 17, 19, and 21-23.

Ground 3: Obviousness over WO ’498 and Bastin - Claims 1-3, 17, 19, and 21-23 are obvious over WO ’498 in view of Bastin.

  • Prior Art Relied Upon: WO ’498 and Bastin (a 2000 journal article titled Salt Selection and Optimisation Procedures for Pharmaceutical New Chemical Entities).

  • Core Argument for this Ground:

    • Prior Art Mapping: WO ’498 discloses sitagliptin as a weakly basic compound (due to its amine group) and provides an example of its hydrochloride salt. Bastin provides a general, well-established framework for salt selection for weakly basic drug substances, teaching that salts of inorganic acids—specifically listing hydrochloride, sulfate, and phosphate—are routinely considered to enhance properties like aqueous solubility.
    • Motivation to Combine: A POSA starting with sitagliptin from WO ’498 would be motivated by standard pharmaceutical development practices to optimize its salt form. Petitioner argued that Bastin provides the exact roadmap for this routine optimization. A POSA would combine WO ’498’s disclosure of sitagliptin with Bastin’s teachings on common salt forms to identify a candidate with superior physicochemical properties. Both references identify hydrochloride and phosphate as preferred options, motivating a POSA to consider phosphate as a direct and logical alternative to the exemplified hydrochloride salt.
    • Expectation of Success: Given that both WO ’498 and Bastin identify phosphate/phosphoric acid as a preferred and common choice for forming salts of basic compounds, a POSA would have had a high expectation of success in preparing sitagliptin phosphate using conventional methods. Petitioner framed this as a classic "obvious to try" scenario, where a finite number of identified and predictable solutions (i.e., common pharmaceutical salts) were available to the skilled artisan for a known purpose.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including that claims 3, 17, 19, and 21-23 are obvious over WO ’498 alone (contingent on a finding that claim 2 is anticipated). Petitioner also argued that claim 4 (crystalline monohydrate) is obvious over combinations including WO ’498, Bastin, and Brittain (a reference teaching the prevalence of monohydrates among pharmaceutical solids).

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial would be improper. Under §325(d), it was argued that the petition was not cumulative because the Examiner raised no prior art rejections during prosecution, making the petition's arguments necessarily different. Under §314(a), Petitioner contended that because it sought joinder with an already-instituted IPR (IPR2020-00040), the Patent Owner would face no prejudice from a second proceeding. Petitioner further noted that the parallel district court proceedings were in their early stages and that Petitioner had not yet been sued, mitigating any concerns of unfair tactical advantage.

5. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-4, 17, 19, and 21-23 of Patent 7,326,708 as unpatentable.