NATCO PHARMA LIMITED vs NOVARTIS AG AND ANR

IN THE HIGH COURT OF DELHI AT NEW DELHI
% Judgment delivered on: 24.04.2024
+ FAO(OS) (COMM) 178/2021 and CM Nos.46299/2021, 46300/2021, 46301/2021, 46302/2021, 19118/2022, 19119/2022 and 30850/2022
NATCO PHARMA ….. Appellant
versus
NOVARTIS AG AND ANR. ….. Respondents
Advocates who appeared in this case:

For the Appellant : Mr J. Sai Deepak, Mr G. Nataraj,
Mr Shashikant Yadav, and Mr Rahul
Bhujbal, Advocates.
For the Respondents : Mr Hemant Singh, Ms Mamta Rani Jha,
Mr Siddhant Sharma and Ms Garima
Mehta, Advocates.
CORAM
HON’BLE MR JUSTICE VIBHU BAKHRU
HON’BLE MR JUSTICE AMIT MAHAJAN

JUDGMENT

VIBHU BAKHRU, J
INTRODUCTION
1. The appellant (hereafter referred to as Natco) has filed the present appeal impugning a judgment dated 13.12.2021 (hereafter the impugned judgment) delivered by the learned Single Judge in an application filed by the respondents (hereafter collectively referred to as Novartis) under Order XXXIX Rules 1 and 2 of the Code of Civil Procedure, 1908 (hereafter the CPC) being IA No. 6980/2021 in CS(COMM) 256/2021, seeking an interim relief.
2. The respondents had filed the aforementioned suit, inter alia, seeking a decree of permanent injunction restraining Natco from using, manufacturing, importing, selling, offering for sale, exporting, or dealing in Active Pharmaceutical Ingredient (hereafter API), or formulations containing Eltrombopag bis (monoethanolamine) as may amount to infringement of its suit patent IN 233161 (hereafter also referred to as IN’161 or the suit patent). Novartis also seeks rendition of account of profits earned by manufacture and sale of infringing products; damages based on profits earned by Natco through its infringing activities; and a decree for delivery of stocks of products that infringe the suit patent.
3. The application for interim relief was allowed. In terms of the impugned judgment, the learned Single Judge has restrained Natco from manufacturing, using, selling, distributing, advertising, marketing, exporting, offering for sale, importing or dealing in any manner in API, pharmaceutical products, or formulation containing Eltrombopag bis (monoethanolamine) (hereafter Eltrombopag Olamine or ELT-O) either separately or in combination with any other compound, infringing the suit patent, of respondent no.1 (hereafter Novartis AG), either under the brand “Trombopag” or any other brand.
4. Novartis had filed the afore-mentioned suit alleging infringement of the suit patent, IN’ 161, granted on 27.03.2009 (species patent) pursuant to the Patent Application No.3400/DELNP/2004, which was filed as a national phase entry of Patent Cooperation Treaty (PCT) International Application No.PCT/US2003/16255 dated 21.05.2003. The said application was filed by SmithKline Beecham Corporation (subsequently known as GlaxoSmithKline LLC). GlaxoSmithKline LLC had assigned the suit patent to Glaxo Group Limited on 05.10.2015. On the same date, Glaxo Group Limited had assigned the suit patent to Novartis Pharma AG, which in turn assigned the suit patent to Novartis AG (respondent no.1). Novartis claims that it was constrained to file the suit [CS(COMM) 256/2021] as it had become aware through the field force and medical practitioners that Natco had announced the launch of a pharmaceutical drug product containing ELT-O, which was covered by the suit patent.
5. It is Natco’s defence that ELT-O was covered under an earlier Patent No. IN 213176 (hereafter IN’176), which expired on 24.05.2021. Thus, ELT-O was not entitled to any patent protection after 24.05.2021. Natco has filed its written statement contesting the suit principally on three fronts. First, that the suit is barred under Section 53(4) of the Patents Act, 1970 (hereafter the Act); Novartis has not, prima facie, satisfied the condition that the suit patent is valid and; the suit patent is invalid on several grounds as set out in Section 64(1) of the Act.
6. It is Natco’s case that two separate patents were secured in respect of the same product being ELT-O by suppression and misrepresentation. Whilst, IN’176, which covered the API Eltrombopag (hereafter also referred to as ELT) as well pharmaceutically acceptable salts, expired on 24.05.2021, after expiry of the period of twenty years, the monopoly in respect of the same product is claimed on account of securing the suit patent. Natco claims that this is an attempt to evergreen the patent in respect of ELT.
7. There is no dispute that IN’176 covers the product ELT-O. However, Novartis claims that IN’176 is a Markush claim and discloses Eltrombopag free acid (ELT); it does not disclose ELT-O, which is the subject matter of rights under IN’161.
8. It is not seriously contested that ELT, which is covered under IN’176 is the API in the formulations marketed by Novartis under the brand names PROMACTATM and REVOLADETM. REVOLADETM received marketing approval in India on 05.01.2011. Admittedly, REVOLADETM was covered in IN’ 176.
9. ELT is also the API of Tromobopag (the formulation launched by Natco) and is the subject matter of the interim injunction issued in terms of the impugned judgement. The suit patent, IN’ 161 covers the substance, ELT-O which is a salt form of ELT.
10. The principal controversy that falls for consideration is whether Natco has presented a credible challenge to the validity of IN’161. Natco claims that there is no evidence or material on record to establish that ELT-O has a higher therapeutic efficacy than ELT, which is admittedly disclosed and covered by IN’176. It claims that ELT-O is a new (salt) of a known substance (ELT) and therefore, is not patentable on the anvil of Section 3(d) of the Act. It claims that ELT-O is not an invention and therefore its patent, IN’161 is invalid [Section 64(1)(d) of the Act].
11. Natco also assails the validity of the suit patent on the following grounds:
* Prior claiming [Section 64(1)(a) of the Act] as covered under the expired patent IN’176.
* The claim ELT-O is not an invention [ Section 64(1)(d) of the Act] being a new form (Salt) of a known substance.
* Lack of novelty [ Section 64(1)(e) of the Act]
* Lack of inventive step [ Section 64(1)(f) of the Act]
* Obtained by misrepresentation [ Section 64(1)(j) of the Act]
* Claim not patentable under the Act [ Section 64(1)(k) of the Act]
* Failure to disclose information under Section 8 of the Act [ Section 64(1)(m) of the Act]
12. In the present proceedings, Natco’s principal challenge is founded on ELT-O not being an invention in terms of Section 3(d) of the Act which has been pressed in conjunction with the patent being invalid on account of prior claiming, prior publication, lack of inventive step amongst other grounds.
13. Novartis claims that although, ELT-O is a salt of ELT, it falls within the exception of Section 3(d) of the Act as its therapeutic efficacy is significantly higher than ELT on account of higher bioavailability.
FACTUAL BACKGROUND
14. As noticed above, the controversy in this appeal, essentially, involves the questions whether Natco has laid a credible challenge to the validity of the suit patent and whether Novartis was entitled to an interim injunction restraining Natco from dealing with ELT-O which was launched under the trade name TROMBOPAGTM. The substratal dispute being, whether Novartis is entitled to patent rights in respect of ELT-O, notwithstanding that ELT-O was also covered under IN’176 which expired prior to Natco launching its product.
IN’176
15. Novartis AG is the patentee of the expired patent IN’176. SmithKline Beecham Corporation, a company organised under the laws of Pennsylvania, the United States of America had applied for the said patent in continuation of the US Application No.10/296688 filed on 03.07.2000 claiming priority of International Application No.PCT/US01/16863 filed on 24.05.2001. The same was ultimately assigned to Novartis AG.
16. IN’176 expired on 24.05.2021.
17. The applicant had disclosed that invention related to Thrombopoietin (TPO) mimetics and their use as promoters of thrombopoiesis and megakaryocytopoiesis. The invention ELT, which is the subject matter of IN’176, was claimed to be effective as an agonists of TPO receptor and potent TPO mimetics. ELT is claimed to be useful in enhancing platelet production and is indicated for treatment of chronic idiopathic thrombocytopenia (that is, abnormally low platelet counts), which was noticed in patients suffering from immune system disorders, leukaemia as well as side effects due to certain drugs and surgical procedures.
18. The applicant had made, in all, nine claims. Claim Nos. 1 to 8 consist of substances and Claim no.9 relates to a process for preparing the compound. It is relevant to refer to Claim nos.1 to 8, which are set out below:

IN 213176
Claim 1: A compound represented by the following Formula (II):

wherein:
R, R1, R2 and R3 are each independently selected from hydrogen, C1-6alkyl, -(CH2)pOR4,- C(O)OR4, formyl, nitro, cyano, halogen, aryl, substituted aryl, substituted alkyl, -S(O)nR4, cycloalkyl, -NR5R6, protected -OH, -CONR5R6, phosphonic acid, sulfonic acid, phosphinic acid, – SO2NR5R6, and a heterocyclic methylene substituent as represented by Formula (III),

where
p is 0-6,
n is 0-2,
V, W, X and Z are each independently selected from 0, S, and NR16, where R16 is selected from: hydrogen, alkyl, cycloalkyl; C1-C12aryl, substituted alkyl, substituted cycloalkyl and substituted C1-C12aryl, R4 is hydrogen, alkyl, cycloalkyl, C1-C12aryl substituted alkyl, substituted cycloalkyl, and substituted C1-C12aryl, and R5 and R6 are each independently selected from hydrogen, alkyl, substituted alkyl, C3-6cycloalkyl,
and aryl, or
R5 and R6 taken together with the nitrogen to which they are (attached represent a 5 to 6 member saturated ring containing up to one other heteroatom selected from oxygen and nitrogen;
R15 is selected from the group consisting of alkyl, C1-C12aryl, hydroxy, alkoxy, substituted alkyl, substituted C1-C12aryl and halogen; m is 0-6; and

Y is selected from alkyl, substituted alkyl and a cyclic or polycyclic aromatic ring containing from 3 to 14 carbon atoms and optionally containing from one to three heteroatoms, provided that when the number of carbon atoms is 3 the aromatic ring contains at least two heteroatoms and when the number of carbon atoms is 4 the aromatic ring contains at least one heteroatom, and optionally substituted with one or more substituents selected from the group consisting of: alkyl, substituted alkyl, C1-C12 aryl, substituted cycloalkyl, substituted C1-C12aryl, hydroxy, aryloxy, alkoxy, cycloalkyl, nitro, cyano, halogen and protected -OH; and pharmaceutically acceptable salts, hydrates, solvates and esters thereof; provided that at least one of R, R1, R2 and R3 is a substituted aryl group or a heterocyclic methylene substituent as represented in Formula (III).
Claim 2: A compound represented by Formula (II), as claimed in claim 1, wherein:
either:
R is a substituted aryl and R1 is hydrogen; or:
R is hydrogen; and R1 is a substituted aryl;
and in either case:
R2 and R3 are each independently selected from hydrogen, C1-6 alkyl, C1- 6alkoxy, nitro, cyano, halogen, aryl, substituted aryl, substituted alkyl, cycloalkyl, phosphonic acid, phosphinic acid and sulfonic acid;
R15 is selected from the group consisting of alkyl, substituted alkyl, C1- C12 aryl, alkoxy and halogen;
m is 0-4; and
Y is selected from phenyl, pyridinyl and pyrimidinyl, where the phenyl, pyridinyl and pyrimidinyl are optionally substituted with from one to three substituents selected from the group consisting of: alkyl, substituted alkyl, C1-12aryl, substituted C1-12aryl, alkoxy and halogen; and pharmaceutically acceptable salts, hydrates, solvates and esters thereof.
Claim 3: A compound represented by Formula (II), as claimed in claim 1 or 2, wherein:
R is a substituted C1-C12aryl;
and
R1 is hydrogen;
R2 and R3 are each independently selected from hydrogen; C1-6alkyl, C1-6alkoxy, nitro, cyano, halogen, substituted alkyl and cycloalkyl;
R15 is selected from the group consisting of alkyl, substituted alkyl, C1-C12 aryl, alkoxy and halogen;
m is 0-2; and
Y is selected from phenyl, pyridinyl and pyrimidinyl, where the phenyl, pyridinyl and pyrimidinyl are optionally substituted with from one to three substituents selected from the group consisting of: alkyl, substituted alkyl, C1-C12 aryl, substituted C1-C12 aryl, alkoxy and halogen; and
pharmaceutically acceptable salts, hydrates, solvates and esters thereof.
Claim 4: A compound represented by Formula {II), as claimed in any one of claims 1 to 3, wherein:
R is a substituted phenyl or pyridinyl ring; and
R1 is hydrogen;
R2 and R3 are each independently selected from hydrogen, C1-6alkyl, C1-6 alkoxy, nitro, cyano, halogen, substituted alkyl and cycloalkyl; R15 is selected from the group consisting of alkyl, substituted alkyl, C1- C12aryl and halogen; m is O; and Y is selected from, phenyl, pyridinyl and pyrimidinyl, where the phenyl, pyridinyl and pyrimidinyl is optionally substituted with from one to three substituents selected from the group consisting of: alkyl, substituted alkyl, C1-Cl2 aryl, substituted C1-C12 aryl, alkoxy and halogen; and pharmaceutically acceptable salts, hydrates, solvates and esters thereof.
Claim 6: A compound as claimed in claim 1, which is 3’[(2Z)[1-(3,4 dimethylphenyl)-1,5-dihydro-3-methyl-5-oxo-4H-pyrazol-4-ylidene]hydrazino]-2’-hydroxy-[1,1’-Biphenyl]-3-Carboxylic Acid and pharmaceutically acceptable salts, hydrates, solvates and esters thereof.
Claim 8: A pharmaceutical composition for use in enhancing platelet production which comprises a compound as claimed in claim 1 and a pharmaceutically acceptable carrier.

19. The background of the invention as set out in the patent application indicates that the invention Thrombopoietin (TPO) was found in several studies to increase platelet counts, platelet size, and isotope incorporation into platelets of recipient animals. Since, platelets (thrombocytes) are necessary for blood clotting, patients with low platelet count are at risk of death from haemorrhage. TPO has potentially useful application in both diagnosis and treatment of various haematological disorders. It was stated that ongoing clinical trials with TPO indicate that TPO can be administered safely to patients. Further, studies had provided the basis for projection of efficacy of TPO therapy in the treatment of thrombocytopenia, and particularly thrombocytopenia resulting from chemotherapy, radiation therapy, or bone marrow transplant as a treatment for cancer or a treatment of lymphoma. Thus, it would be desirable for the treatment of thrombocytopenia by acting as a TPO mimetic. The compounds as claimed were discovered as effective, agonists of TPO receptor and are potent TPO mimetics.
IN’161
20. The suit patent is in respect of the following invention:
“3’-[2Z)-[1-(3,4-dimethylphenyl)-1,5-dihydro-3-methyl-5-oxo-4H-pyrazol-4-ylidene]hydrazino]-2’-hydroxy-[1,1’-Biphenyl]-3- Carboxylic Acid bis-(monoethanolamine)”
21. Novartis AG’s predecessor claimed that the aforesaid invention relates to an improved thrombopoietin mimetic. The aforesaid invention is covered under Claim no.1. Claim no.2 is of the aforesaid compound as and when used as a pharmaceutical composition along with the pharmaceutically acceptable carrier or diluents of the kind as described. Claim no.3 related to the process of preparing the compound as claimed in Claim no.1.
22. Claim nos. 1, 2 and 3 in respect of the suit patent IN’161 are reproduced hereinbelow:
IN 233161
The compound 3’[(2Z)[1-(3,4- dimethylphenyl)-1,5-dihydro-3-methyl-5-oxo-4H-pyrazol-4-ylidene]hydrazino]-2’-hydroxy-[1,1’-Biphenyl]-3- Carboxylic Acid bis- (monoethanolamine).
ELT Olamine is represented by the following chemical structure:

A transposition of the substituents from IN’176 is as follows:
R is substituted aryl where the substitution is -COOH:;
R1, R2 and R3 are each -H;
M=0 which leads to only -OH being present at position 5 on the phenyl
R15 is alkyl i.e. methyl ;
Y is phenyl substituted with two alkyl i.e. two methyl moieties
and the sale is a monoethanolamine salt.
Claim 2: A compound as claimed in claim 1 as and when used as a pharmaceutical composition along with the pharmaceutically acceptable carrier or diluents of the kind such as herein described.
Note: Claim 2 of IN’161 specifically stipulates that the diluent/carrier etc are as “herein described”. The preceding description stipulates that the diluents and carriers are conventional and exactly as those used in IN’ 176.
Claim 3: A process for preparing the compound as claimed in claim 1, which process comprises:
i) dissolving 3?-[(2Z)-[1 -(3,4-dimethyiphenyl)- 1,5-dihydro-3- methyl-5-oxo-4H-pyrazol-4- ylidene]hydrazino]-2?-hydroxy-[1,1?- biphenyl]-3-carboxylic acid in an appropriate organic solvent, preferably Tetrahydrofuran (THF) and ethanol to form a solution;
ii) adding two or more equivalents of ethanolamine to the solution; and resulting dark red suspension was stirred and dried at 50ºC in a vacuum oven over night; and
iii) isolating the prepared compound.

23. The detailed description of the invention, as set out, indicates that it expressly incorporates by reference, the entire disclosure made in IN’176 and further claims that Bis-(monoethanolamine), the salt of ELT (which is a free acid) had numerous advantages over the free acid. It is claimed that the free acid (ELT) was poorly soluble in water, which adversely affects its ability to be formulated into a pharmaceutical dosage form and reduce the bioavailability of the compound in vivo. It is claimed that the suit patent (IN’161) had advantages of enhanced solubility and bioavailability. The relevant extract of the detailed description of invention is set out below:
“3′-{N’-[1-(3,4-dimethylphenyl)-3-methyl-5-oxo-1,5-dihydropyrazol-4-ylidene]hydrazino)-2′-hydroxybiphenyl-3-carboxylic acid is a compound which is disclosed and claimed, along with pharmaceutically acceptable salts, hydrates, solvates and esters thereof, as being useful as an agonist of the TPO receptor, particularly in enhancing platelet production and particularly in the treatment of thrombocytopenia, in International Application No. PCT/US01/16863, having an International filing date of May 24, 2001; International Publication Number WO 01/89457 and an International Publication date of November 29, 2001 (Indian Patent application no. IN/PCT/2002, 1666/MUM which is now Indian Patent No. 213176), the entire disclosure of which is hereby incorporated by reference. International Application No. PCT/US01/16863 does not specifically disclose a salt form for any of the compounds disclosed therein.
It has now surprisingly been found that the bis-(monoethanolamine) salt of 3′-[(2Z)-[1-(3,4-dimethylphenyl)-1,5-dihydro-3-methyl-5-oxo-4H-pyrazol-4-ylidene]hydrazino]-2′-hydroxy-[1,1′-biphenyl]-3-carboxylic acid has numerous advantages over the free acid. The free acid is poorly soluble in water (approximately 5 micrograms per milliliter). This poor solubility adversely affects the ability of the free acid to be formulated into pharmaceutical dosage forms and reduces the bioavailability of the compound in vivo.”
24. The structure of ELT is as under:

25. The structure of ELT-O is set out below:

THE IMPUGNED JUDGMENT
26. The learned Single Judge examined the rival contentions in the light of the decisions rendered by the Supreme Court in Novartis AG v. Union of India & Ors.1and the decision of this Court in Merck Sharpe & Dohme v. Glenmark Pharmaceuticals2 and Astrazeneca AB and Anr. v. Intas Pharmaceuticals Ltd. & Ors.3 as well as various other decisions.
27. The learned Single Judge rejected the contention that enhanced bioavailability or solubility absent other factors enhancing the effectiveness of the invention as a drug cannot be used as the basis for claiming enhanced therapeutic efficacy. The learned Single Judge rejected the contention that the decision of the Supreme Court in Novartis v. UoI1 laid down any such proposition4. The learned Single Judge observed that the therapeutic efficacy of API would remain constant. However, if the therapeutic efficacy of API is enhanced by making the ingredient more available to the body, in the modified formulation, the same would be patentable under Section 3(d) of the Act5.
28. After referring to various decisions, the learned Single Judge summarized the principles emanating from the various decisions in Paragraph no. 30 of the impugned judgement. The relevant extracts of the said paragraphs are set out below:
“30. Several stellar principles emanate from a reading of the afore-quoted judicial authorities. So pivotal are these principles to assessment of infringement, and the aspect of vulnerability of the patent alleged to be infringed, that, at the cost of repetition, I deem it appropriate to enumerate the principles, thus:
(i) On patentability
(a) Inventions, alone, are entitled to patents.
(b) An invention must (i) be new, i.e. not anticipated, (ii) involve an inventive step, (iii) be capable of industrial application, i.e. of being made or used in the industry and (iv) entail technical advance over existing knowledge, or have economic significance, rendering the invention not obvious to a person skilled in the art.
(c) The triple test of patentability is, therefore, novelty, the existence of an inventive step and industrial applicability. In Merck v. Glenmark, it was held that these tests stood satisfied by the SFB disclosed in the Markush patent.
(d) The claim in a patent could conceivably encompass embodiments to be invented in future without particularly advantageous properties, provided such inventions employ the technical contribution made by the invention.
(e) “Patentability” requires that the product (a) must be an invention within the meaning of Section 2(j) and (b), must not fall within the exceptions in Section 3.
(f) Section 3(d) is not an exception to Section 2(1)(j). While assessing patentability of a claim for grant of patent, it had to be examined, in the first instance, whether the product was disentitled to patent on any of the grounds envisaged by Section 3(d). The patentability of products would then have to be assessed, for determination of their patentability on the basis of Section 2(1)(j) read with Section 2(1)(j)(a).
(g) A mere claim, without enabling disclosure, as would enable a person skilled in the art to work the invention, is not patentable.
(h) The role of the complete specification accompanying a patent application is to teach what the invention was, how it was to be made, and how it was to be used.
(i) One invention is entitled only to one patent. One patent may, however, cover more than one invention, provided all inventions involved the same inventive steps.
(j) Grant of repeated patents for the same invention results in the malaise of evergreening of a patent beyond its life, which is impermissible.
(ii) Mere grant of a patent is not necessarily a prima facie indicator of its validity.
(iii) Infringement:
(a) Examination of any claim of infringement requires (i) determination of the meaning and scope of the claims in the suit patent and (ii) comparison of the claim so interpreted with the allegedly infringing product of the defendants. The comparison has to be of the defendants’ product vis-a-vis the plaintiffs’ patent and not product-to-product.
(b) This has to be determined on the basis of claim construction. The plea of a defendant that the plaintiff may have itself applied for grant of patent in respect of the allegedly infringing product, and abandoned the claim later, was held, in Merck v. Glenmark, to be irrelevant. In a visible departure, however, where the claim of the plaintiff was rejected, Roche v. Cipla held this to be an indicator, prima facie, that the defendant’s product infringed the suit patent.
(iv) Section 3(d)
(a) Once a patent was granted to an Active Pharmaceutical Ingredient (API), Section 3(d) protects all products of such API, in any form, from grant of a subsequent patent. The manufacture or marketing by any third party of any product-derivative of a patented API would amount to infringement. The API is the molecular entity which exerts the therapeutic effect of medicine and is biologically active. Patent protection is ordinarily granted to the API.
(b) In the case of pharmaceutical products, the derivatives envisaged by Section 3(d) would include (a) prodrugs, which are not active, but are metabolized in the body so as to result in pharmaceutically active substances, (b) combinations of more than one APIs or the combination of an API with an inert carrier and (c) drug delivery systems, which are compositions enabling the constituents to be administered in a particular fashion.
(c) In Novartis, examining the vulnerability of Imatinib Mesylate to invalidity on the ground of Section 3(d), the Supreme Court held that (i) the obtaining of approval for Imatinib Mesylate on the basis of Zimmerman patent, (ii) the obtaining of patent term extension for the Zimmerman patent on the ground of pendency of regulatory approval for Imatinib Mesylate, (iii) the obtaining, by Novartis, of injunction against marketing of Imatinib Mesylate by any third party on the basis of the Zimmerman patent and (iv) the view of the Board of Patent Appeals that the Zimmerman patent had the teaching to convert Imatinib to Imatinib Mesylate, in conjunction, indicated that Imatinib Mesylate was not a “new product”, within the meaning of Section 3(d), vis-à-vis the Zimmerman patent, but merely a “known substance”.
(d) “Efficacy” in Section 3(d) refers to the function, utility and purpose of the product under consideration. Hence, for pharmaceutical products, “efficacy” would mean “therapeutic efficacy”. “Therapeutic efficacy” was required to be judged strictly and narrowly.
(e) Enhanced properties, which were inherent to the forms of the known substance, visualized in the explanation to Section 3(d) would not imply enhanced efficacy. Enhanced therapeutic efficacy was a must.
(f) “Enhanced solubility” is no indicator of enhanced efficacy in pharmaceutical products.
(g) Applying this principle, the admission, by Novartis, that “all indicated inhibitory and pharmacological effects of the ?-crystalline form of Imatinib Mesylate are present in the free base”, was held by the Supreme Court in Novartis, to indicate that the ?-crystalline form of Imatinib Mesylate did not possess enhanced efficacy vis-à-vis the Imatinib free base.
(h) As no research data had been placed by Novartis on record to indicate enhanced therapeutic efficacy of the ?-crystalline form over the Zimmerman patent, except in respect of properties already possessed by the Zimmerman patent, the Supreme Court, in Novartis, that the ?-crystalline form of Imatinib Mesylate did not possess enhanced therapeutic efficacy vis-à-vis the free base or the non crystalline form of Imatinib Mesylate.
(i) Whether increased bioavailability would or would not, result in enhanced therapeutic efficacy had to be decided on the basis of research data, and had to be specifically claimed.
(v) Coverage, claim construction and disclosure
(a) The coverage of a claim, for the purposes of determination the scope of protection under Section 48 of the Patents Act65 had to be determined by claim construction. Claim construction involved reading of the wording of the claim with its enabling disclosures as contained in the complete specifications, as understood by a person skilled in the art, acquainted with the technology in question. A product could be treated as covered by the claim, for the purposes of patent protection if, on the basis of the wording of the claim read with the enabling disclosures in the complete specifications, the person skilled in the art would be in a position to work the invention so as to make it available to the public by the expiry of the patent term.
(b) The qualities of an enabling disclosure were well delineated in the Wands tests. They involved (i) the quantity of experimentation necessary, (ii) the amount of guidance available in the patent, (iii) the presence/absence of working examples, (iv) the nature of invention, (v) the state of prior art, (vi) the related skill of those in the art, (vii) the predictability/unpredictability of the art and (viii) the breadth of the claims.
(c) Some of the principles of claim construction are that (i) the claim defines the scope and territory of the patent, (ii) claims in a patent may be dependent or independent, (iii) different claims in one patent define different embodiments of the same inventive concept, (iv) invalidation must be of each claim separately and independently, (v) where the claim was worded using the expression “comprising of” various elements, the addition of another element would infringe the patent, (f) where, however, the claim was “consisting of” various elements, infringement would require the subsequent patent to have all the elements in the claim and non other, with the addition of any other element defeating infringement and (g) claims were not to be construed on the basis of prior material or subsequent conduct.
(d) In this context, in my opinion, demystification of the concept of “coverage”, when used in the concept of claim construction and claim protection in patent law, is essential, as there is considerable debate on this issue in nearly every case, with Counsel, relying on the same decisions, adopting near irreconciliable stances. There is, in my view, a distinction between the “broad coverage” of a claim in a patent, and the “protected coverage”, i.e. the coverage which would be entitled to patent protection under Section 48. The following passage from Merck v. Glenmark is important in this regard:
“Construction of the patent by this court, to verify its coverage is fundamental. This coverage depends on the nature of the claims made (and enabling disclosures specified) by MSD in its ‘Complete Specification’ under Form 2 of the Act. The words used to describe the claims – as read by a person of ordinary skill in the art – determine the breadth of the monopoly granted by the patent, for which the substantive (and indeed, substantial) rights under Section 48 of the Act are triggered.”
(Emphasis supplied)
Judgements are not to be read like statutes. While referring to a precedent, it is necessary to discern, with care, what exactly the court seeks to convey. The reference to “coverage”, in the afore-extracted passage from Merck v. Glenmark, is, in my view, to be understood as referring not to the “broad coverage” of the claim, but to that coverage which would be entitled to patent protection under Section 48. The Division Bench holds that the coverage encompassed by the claim, as worded, read with the enabling disclosure, would be entitled to protection under Section 48. A case in point is SPM, which was subject matter of consideration in Merck v. Glenmark. The claim in IN 816, as worded, encompassed “Sitagliptin with its pharmaceutically acceptable salts”. Sitagliptin Hydrochloride was specifically exemplified in the complete specifications in IN 816. The SFB, and Sitagliptin Hydrochloride, therefore were, on a plain reading, entitled to patent protection. Paras 38 and 39 of the report in Merck v. Glenmark goes on to suggest that, possibly, enabling disclosure, in respect of SPM, was also to be found in IN 816 (though, later, the judgement leaves this issue open for more detailed analysis). The paragraphs (to the extent relevant) read thus:
“38. … The section ‘Detailed Description of the Invention’, which discloses Formula 1 (reproduced below), corresponds to claim 1 of the patent specification, discloses the following compound structure:
39. This is the Sitagliptin free base. Each element of this structure, and selection of particular elements to reach this structure, is further detailed at pages 5 and 6 of the specification. Page 10 further details the separation of racemix mixtures of the compound to isolate individual enantiomers, including the R form of the compound that is ultimately used in Januvia and Janumet. The term “pharmaceutically acceptable salts” – it is stated – “refers to salts prepared from pharmaceutically acceptable non-toxic bases or acids including” inter alia phosphoric acid, which is the second element in SPM (i.e. the P in SPM). The M – or monohydrate – is indicated by stating that “salts… may also be in the form of hydrates” (page 10 of the Form 2 filing).”
If, thus, the disclosure contained in IN 816 enabled the person skilled in the cart to arrive at SPM, SPM would also be covered by IN 816 so as to be entitled to patent protection under Section 48.” This, then, would, as held in para 38 of Merck v. Glenmark, be the “coverage” which would trigger the protection provided by Section 48.
(e) As against this, the “broad coverage” of the claim in the patent, as worded, may include products for which there is no enabling disclosure. For example, in IN 816, all pharmaceutically acceptable salts of Sitagliptin are within the “broad coverage” of the claim as worded. Assuming, however, that there is, in the complete specifications in IN 816, no enabling disclosure (arguendo) except in respect of SPM – excepting Sitagliptin Hydrochloride, which is claimed by exemplification, such pharmaceutically acceptable salts, which are not disclosed in IN 816, but are, nonetheless, within the coverage of the claim as worded, would not be entitled to patent protection under Section 48. “Coverage”, in this sense, is, therefore, wider than “disclosure”.
(f) While this distinction between “coverage” of a claim, as understood in absolute terms, and the “disclosures” in the complete specifications relating thereto does exist, the gap between coverage and disclosure could not be so wide as to enable an artful draftsman to so draft a claim as to escape coverage by the prior art.
(g) Applying this principle, the contention of Novartis that the Zimmerman patent covered, but did not disclose Imatinib Mesylate, was rejected by the Supreme Court in Novartis. The Supreme Court held that (a) as the Imatinib free base was covered and disclosed in the Zimmerman patent, (b) the Zimmerman patent also claimed pharmaceutically acceptable salts of the Zimmerman free base, (c) Imatinib Mesylate was a “known substance” from the Zimmerman patent and (d) Imatinib Mesylate was a pharmaceutically acceptable salt of the Imatinib free base, Imatinib Mesylate was claimed and disclosed in the Zimmerman patent.
(h) Similarly, in Merck v. Glenmark, even while expressing no final opinion in that regard, it was observed that (a) the disclosure, in the prior art, of the method of isolation of the Sitagliptin free base, (b) the identification of pharmaceutically acceptable salt of Sitagliptin, in the prior art, as including salts made from phosphoric acid and (c) the suggestion, in the prior art, that pharmaceutically acceptable salts of the Sitagliptin free base may also be in the form of hydrates, indicated that SPM was disclosed in the prior art.
(i) Where the attached salt radical was a mere inert career, and pharmaceutical activity was attributable to the free base, the disclosure of the free base in prior art would imply disclosure of the salt, as novelty existed in the free base, even if the combination with the inert salt radical was useful for effective administration of the drug.
(vi) Obviousness:
(a) “Prior disclosure”, for the purposes of obviousness, meant disclosure which, if performed, would infringe the patent.
(b) Prior art, for the purposes of obviousness, was required to have been published before the priority date of the suit patent.
(c) The test of obviousness was whether, if the prior art document was placed in the hands of a competent draftsman endowed with common general knowledge at the priority date, faced with the problem which the patentee solved in the suit patent, but not endowed with the knowledge of the patented invention, the draftsman would have said “this gives me what I want.”
(d) In Roche v. Cipla-I, various combination tests have been approved by the Division Bench, to assess “obviousness”. These are the following:
(i) The first is the triple test of obviousness, involving determination of the scope and content of the prior art, difference between the prior art and the claims and issue and the level of ordinary skill in the pertinent art resolved. Against this background, the obviousness or non-obviousness of the subject matter is determined. Such secondary considerations as commercial success, long felt but unsolved needs, failure of others, etc., might be utilized to give light to the circumstances surrounding the origin of the subject matter sought to be patented.
(ii) The second test involves the following four steps:
(a) identifying the inventive concept embodied in the patent;
(b) imputing to a normally skilled but unimaginative addressee what was common general knowledge in the art at the priority date;
(c) identifying the differences if any between the matter cited and the alleged invention; and
(d) deciding whether those differences, viewed without any knowledge of the alleged invention, constituted steps which would have been obvious to the skilled man or whether they required any degree of invention.
(iii) The third test involves the following five steps:
“Step No. 1 – To identify an ordinary person skilled in the art,
Step No. 2 – To identify the inventive concept embodied in the patent,
Step No. 3 – To impute to a normal skilled but unimaginative ordinary person skilled in the art what was common general knowledge in the art at the priority date.
Step No. 4 – To identify the differences, if any, between the matter cited and the alleged invention and ascertain whether the differences are ordinary application of law or involve various different steps requiring multiple, theoretical and practical applications,
Step No. 5 – To decide whether those differences, viewed in the knowledge of alleged invention, constituted steps which would have been obvious to the ordinary person skilled in the art and rule out a hideside (sic hindsight) approach.”
(e) The reason or motivation for making the choices which would lead the persons skilled in the art to arrive at the suit patent from the prior art, must be apparent in the prior art, i.e. in the claim in the prior art read with its enabling disclosure, for “obviousness” to exist. The “motivation” must include the motivation to select and the motivation to combine.76
(f) The suit patent is obvious from the prior art if the invention claimed in the suit patent, as a whole, would have been obvious, prior to the priority date of the suit patent, to a person skilled in the art, from the claim in the prior art read with its enabling disclosures. In this, the first step is the selection of the prior art as the lead compound.
(g) Clear differences in molecular structure would militate against any inference of obviousness.
(h) In assessing obviousness, hindsight analysis is impermissible. In other words, while assessing whether the suit patent is vulnerable to invalidity on the ground of obviousness, the teachings in the suit patent cannot be used as a guide. If the teachings in the suit patent are required to be referred, it would imply that the exercise is one of hindsight analysis.
(i) The simple test to ascertain whether the suit patent is obvious from the prior art, is, therefore, to arm the mythical person skilled in the art with the complete specifications of the prior art, and the objective which the suit patent ultimately achieved. If the person is able to use the teaching in the prior art to arrive at the suit patent, the suit patent is obvious. If he is not able to do so, it is not.
(j) The “person skilled in the art” is “a person who practices in the field of endeavor, belongs to the same industry as the invention, possesses average knowledge and ability and is aware of what was common general knowledge at the relevant date”.
(k) A claim of infringement, by the product of the defendant, of the suit patent as well as the prior art, would itself defeat, prima facie, the allegation of infringement, as it would imply that the suit patent is obvious from the prior art.
(l) In the case of a Markush patent, and a subsequent patent for a specific entity, where the Markush does not contain any precise enabling disclosure teaching the way to the subsequent patent, the question to be addressed while examining the vulnerability of the subsequent patent as obvious from the Markush, would be as to how far the subsequent patent is subsumed in the earlier Markush patent.
(m) Where the inventor of the prior art and the suit patent is the same, the appropriate test to be applied would be that of “a person in know, rather than a person skilled in the art.”
(vii) Industrial applicability and commercial utility:
(a) On the aspect of industrial applicability, in Merck v. Glenmark, it was held that, once the SFB had been disclosed, alongwith disclosure of its usefulness in treating diseases and the mode of administration of the drug resulting from the free base, the SFB was capable of industrial application.
(b) Capability of industrial application has to be decided on the basis of the API, not on the basis of the particular salt. The requirement of combination of the API with an inert career, for its administration, was irrelevant to the issue of industrial application.
(c) The inert career is not the crux of the invention, as the therapeutic efficacy is attributable to the API alone.
(d) The criteria to assess industrial application are (i) that the patent must disclose its practical application and be of profitable use, (ii) the use of the patent in industrial practice must be derivable directly from the description in the complete specifications read with common general knowledge, (iii) speculative use is insufficient in this regard and (iv) the complete specification, read with common general knowledge, was required to be sufficient to enable a person skilled in the art to exploit the invention without undue burden and without having to carry out a research programme.
(e) In pharmaceutical compounds, generally, a patent is capable of industrial application if (i) the function of the entity is disclosed in the patent and (ii) the function disclosed relates to usefulness of the entity in the medical industry.
(f) Breakthrough inventions, even if not commercially viable at the time of their conceptualization, or invention, are nonetheless useful and industrially applicable. In this context, “commercial utility” must be distinguished from “patentable utility”. “Commercial utility” is not a sine qua non for patentability.
(g) Any challenge to the validity of a patent on the ground of want of commercial utility, in order to succeed, would require the challenger to show that the later commercially successful patent owed nothing to the original patent.
(h) A patent could be treated as lacking commercial utility only if, even if worked as suggested by the complete specifications, it would not yield the promised result. If it does, commercial utility is established.
(viii) Section 8:
(a) The requirement of compliance with Section 8 of the Patents Act is mandatory.
(b) As violation of Section 8 renders the patent vulnerable to revocation, the provision is required to be strictly construed.
(c) Section 8 is applicable only to foreign patents.
(d) The use of the word “may” in Section 8 indicates that, breach does not automatically result in revocation of the patent and that revocation is discretionary.
(e) At the interlocutory stage, it is normally not advisable to reject a request for injunction on the ground of violation, in obtaining the suit patent, of Section 8.
(f) The failure, by the plaintiff, to disclose the earlier application filed by the plaintiff for the patent in respect of the allegedly infringing product later released by the defendant, would not be fatal where, at the time of applying for the suit patent, the plaintiff was of the opinion that the allegedly infringing product was a separate invention. This principle was applied in Roche, in the context of Erlotinib Hydrochloride vis-à-vis polymorph B thereof.”

29. Insofar as Natco’s challenge to the validity of IN’161 on the anvil of Section 3(d) of the Act is concerned, the learned Single Judge held that in the case of Novartis v. UoI1, the Supreme Court had accepted that bioavailability could be an indicator of increased therapeutic efficacy. The learned Single Judge further observed that the decision in the case of Novartis v. UoI1 was in the context of a challenge to the rejection of an application for registration of a patent and thus, the applicant was required to establish the increase in therapeutic efficacy of the invention. However, in the present case since, the patent in respect of ELT-O was granted, the onus would lie heavily on Natco to establish the vulnerability of the suit patent on the ground of invalidity. The learned Single Judge held that the challenge to the validity of patent must be a credible challenge, which occupies a higher pedestal than a challenge, which is worthy of consideration.
30. The learned Single Judge referred to the data provided by Novartis and observed that ELT, when combined with Olamine increases the yield of Eltrombopag (the free acid). The learned Single Judge also, prima facie, accepted the contention that the maximum plasma concentration of ELT-O was thrice the plasma concentration of ELT. The learned Single Judge did not accept that Natco had laid a credible challenge to the validity of IN’161 on the ground that it did not enhance the therapeutic efficacy of ELT.
31. The learned Single Judge also rejected the contention that the suit patent was vulnerable under Section 64(1)(a) of the Act on the ground of anticipation by prior claim. The learned Single Judge held that the suit patent would be vulnerable only if ELT-O as claimed was contained in complete specifications of IN’176. The learned Single Judge held that to sustain the challenge under Section 64(1)(a) of the Act, the claim, the validity of which is challenged, must be identical to the claim in a prior art or of a co-equal extent and amplitude. Since, Claim no.1 in IN’161 specifically claimed ELT-O, it was necessary for Natco to establish that the prior art (IN’176) also specifically claimed ELT-O.
32. It was contended on behalf of Natco that selecting the appropriate compounds as mentioned in the specification in IN’176 would yield ELT-O solubility. However, the said contention was rejected as the learned Single Judge was of the view that the selection of various compounds was by resorting to hindsight deduction. The learned Single Judge was of the view that it was not permissible for Natco to make out a case of vulnerability of IN’161 on the ground of anticipation by prior claiming by “cherry picking substituents from those suggested in the complete specifications in the prior art and substituting them at the appropriate site in the Markush moiety as to arrive at the suit patent.” The learned Single Judge held that for claiming anticipation by prior claiming, the claim in the suit patent must be shown to have been claimed in the prior art.
33. The learned Single Judge sought to draw a distinction between a broad coverage of a claim based on its wording and the coverage of a claim as would entitle patent protection under Section 48 of the Act. The learned Single Judge held that protection under Section 48 of the Act is available only to the coverage of the claim as it emerges from the claim construction read with the enabling disclosure accompanying the claim in the complete specifications. Thus, although Claim no.6 in IN’176 would broadly cover ELT-O as a pharmaceutically acceptable salt of ELT, but it could not be accepted that ELT-O was claimed under Claim no.6 in IN’176 read with the enabling disclosure.
34. The learned Single Judge also rejected the contention that the PTE (Patent Term Extension) and SPC (Supplementary Protection Certificate) applications filed by Novartis for its predecessor in respect of US’870 and EP’378 or the entry in the orange book could constitute the basis for a credible challenge to the suit patent- IN’161.
35. The learned Single Judge did not prima facie accept the contention that ELT-O was claimed and disclosed either in US’870 or in EP’378 merely, because it was stated that the said patents “read on” to the approved drug product (that is, Eltrombopag Olamine). The learned Single Judge held that these are matters, which would require the detailed examination during trial.
36. The learned Single Judge did not accept that Form No.27 filed by Novartis in respect of IN’176 and IN’161 were relevant in determining whether ELT-O was claimed in IN’176.
37. The learned Single Judge did not accept that Natco’s challenge to IN’161 on the ground of obviousness under Section 64(1)(d) of the Act prima facie presented a credible challenge to IN’176. The learned Single Judge held that on a plain comparison of Claim nos.1 to 4 in IN’176 and Claim no. 1 in Suit Patent, IN’161, it is clear that the exercise to show that ELT-O was obvious from the teachings of IN’176 was an exercise of hindsight, which was not permissible. The learned Single Judge held that motivation to select certain compounds out of several compounds provided in the prior art (IN’176) and the motivation to substitute them at the appropriate site so as to achieve the desired purpose, are both required to be shown to exist in the prior art itself. The learned Single Judge held that the exercise undertaken to arrive at Claim no.1 of IN’176 from Claim no.1 to 5 of IN’161 was clearly one of hindsight analysis.
38. The learned Single Judge prima facie accepted the contention that ELT-O was unknown as a pharmaceutically acceptable salt of ELT prior to the priority date of IN’161. Therefore, it was a novel invention. The learned Single Judge, therefore, rejected the contention that Claim no.6 of IN’176 enabled a person skilled in the art to arrive at ELT-O. Natco had cited certain prior arts, which reflected the use of Olamine. Natco had claimed that a person skilled in art could, thus, arrive at a suit patent by using Olamine to form a pharmaceutically acceptable salt of ELT. In view of the above, the learned Single Judge restrained Natco from manufacturing or distributing ELT-O.
REASONS AND CONCLUSION

Standard of Challenge to validity at Interim stage
39. At the outset, it is relevant to note that there is no presumption of validity of a patent by virtue of the same being granted by the Patent Office. Thus, the fact that the examiners have conducted necessary investigations prior to the grant of patent does not render a patent immune from challenge to its validity. The contention that there was no pre-grant or post-grant opposition to IN’161 and therefore, Natco has to cross a very high threshold to assail the validity of the patent, is unmerited. The Act expressly enables a challenge to the validity of a patent at various stages. Section 25(1) of the Act enables any person to challenge the grant of a patent after the application for the patent has been published. This is, essentially, in aid of the examination process6. In terms of Section 25(2) of the Act, an interested person can challenge the grant of a patent on the grounds as set out in the said sub-section, subject to the said challenge being raised within a period of one year from the date of publication of the patent. Section 64(1) of the Act also enables a person to file a petition for revocation of a patent on the grounds as set out in Section 64(1) of the Act. In terms of Section 64(1) of the Act, any person interested, or the Central Government is entitled to apply for revocation of the patent, either, by way of a petition or by way of a counter-claim in a suit for infringement on the grounds as set out in Section 64(1) of the Act. Additionally, in terms of Section 105 of the Act, any person is entitled to institute a suit for declaration, that the use by him of any process, or the making, use or sale of any article by him does not, or would not constitute infringement of a claim of a patent.
40. It is also material to note that there is no statutory provision similar to Section 31 of the Trade Marks Act, 1999, which posits a statutory presumption of validity on grant of a patent. It is also relevant to refer to Section 13(4) of the Act, which expressly provides that the investigation required under Section 12 of the Act – the pre-grant investigations and inquiries leading to the grant of patent – does in any way warrant the validity of any patent.
41. Absent any statutory presumption and given the scheme of the Act, which enables challenge to the validity of a patent at several stages, there is neither any presumption as to the validity of a patent nor renders the patent immune for challenge to its validity.
42. Thus, in an action for infringement of a patent, defence as to the invalidity of the patent on the grounds as provided in Section 64(1) of the Act, is available to the defendant. The court is required to examine the challenge with an open mindset and not from the standpoint of an assumption that the patent is validly granted.
43. Unless there is no real prospect of the defendant to succeed in its challenge and an appropriate application to allow the action is made prior to framing of issues, the questions as to the validity of the patent asserted, are required to be determined at the trial. However, at the stage of interim relief, the defendant has to establish its assertion that its defence is not insubstantial and sets out a credible challenge to the validity of the patent. The defendant is not required to establish that the patent is invalid, it has to merely show that the patent is vulnerable. If the challenge raised to the validity is substantial, the threshold standard for resisting an interim injunction in this regard – subject to other relevant considerations –would be met. In this context, it is relevant to refer to the decision of the Division Bench of this Court in F. Hoffmann-LA Roche Ltd. & Anr. v. Cipla Ltd.7. In the said case, the Division Bench had rejected the contention that the defendant had a heavy burden to discharge and would have to establish a stronger prima facie case than the plaintiff. The Division Bench had also not accepted the contention that since there is a multi-level examination of opposition to the grant of patent, it ought to be accorded the highest weightage. The relevant extract of the said decision is set out below:
“53. The plea of the plaintiff that since there is a multi-layered, multi-level examination of the opposition to the grant of patent it should accorded the highest weightage, is not entirely correct. The contention that there is a heavy burden on the defendant to discharge since it has to establish that it has a stronger prima facie case of the plaintiff is contra indicated of the decisions in the context of Section 13(4). Reference may be made to the decisions in Biswanath Prasad Radhey Shyam v. Hindustan Metal Industries, (1979) 2 SCC 511 : AIR 1982 SC 1444 : Supp (1) PTC 731 (SC), Standipack Pvt. Ltd. v. Oswal Trading Co. Ltd., AIR 2000 Del 23 : (1999) 19 PTC 479 (Del), Bilcare Ltd. v. Amartara Pvt. Ltd., (2007) 34 PTC 419 (Del), Surendra Lal Mahendra v. Jain Glazers, 1980 SCC OnLine Del 219. In Beecham Group Ltd. v. Bristol Laboratories Pty Ltd., (1967-1968) 118 CLR 618 and Australian Broadcasting Corporation v. O’Neill, (2006) 229 ALR 457 it was held that the defendant alleging invalidity bears the onus of establishing that there is “a serious question” to be tried on that issue. In Hexal Australai Pty Ltd. v. Roche Therapeutics Inc., 66 IPR 325 it was held that where the validity of a patent is raised in interlocutory proceedings, “the onus lies on the party asserting invalidity to show that want of validity is a triable question.” In Abbot Laboratories v. Andrx Pharmaceuticals Inc. (decision dated 22nd June 2006 of the U.S. Court of Appeals for the Federal Circuit 05-1433) the Court of Appeals followed its earlier ruling in Helifix Ltd. v. Blok-Lok Ltd. 208 F.3d 1339 where it was held (at 1359): “In resisting a preliminary injunction, however, one need not make out a case of actual invalidity. Vulnerability is the issue at the preliminary injunction stage, while validity is the issue at trial. The showing of a substantial question as to invalidity thus requires less proof than the clear and convincing showing necessary to establish invalidity itself.” (emphasis supplied) In Erico Int’ll Corprn v. Vutec Corprn (U.S. Court of Appeals for the Federal Circuit, 2007-1168) it was held that the “defendant must put forth a substantial question of invalidity to show that the claims at issue are vulnerable.”
54. In the present case, the grant of a patent to the plaintiffs for Erlotinib Hydrochloride as a mixture of Polymorphs A and B will not ipso facto entitle them to an interim injunction if the defendant is able to satisfy the court that there is a serious question to be tried as to the validity of the patent. The use by the learned Single Judge of the expressions “strong credible challenge”, “arguable case” or that the defendants claim being not unfounded, cannot be termed as vague and inconsistent since they convey the same meaning in the context of the strength of the defendant’s challenge.
55. The question before this Court is when can it be said that the defendant has raised a credible challenge to the validity of a patent held by the plaintiff in an infringement action? During the course of the argument it was suggested by counsel that the challenge had to be both strong and credible. Also, the defendant resisting the grant of injunction by challenging the validity of the patent is at this stage required to show that the patent is “vulnerable” and that the challenge raises a “serious substantial question” and a triable issue. Without indulging in an exercise in semantics, the Court when faced with a prayer for grant of injunction and a corresponding plea of the defendant challenging the validity of the patent itself must enquire whether the defendant has raised a credible challenge. In other words, that would in the context of pharmaceutical products, invite scrutiny of the order granting patent in the light of Section 3(d) and the grounds set out in Section 64 of the Patents Act, 1970. At this stage of course the Court is not expected to examine the challenge in any great detail and arrive at a definite finding on the question of validity. That will have to await the trial. At the present stage of considering the grant of an interim injunction, the defendant has to show that the patent that has been granted is vulnerable to challenge. Consequently, this Court rejects the contentions of the plaintiffs on this issue and affirms the impugned judgment of the learned Single Judge”

44. It is also relevant to refer to the decision of the learned Single Judge of this Court in Astrazeneca AB & Anr. v. Intas Pharmaceuticals Ltd.8. In the said case, the learned Single Judge rejected the contention that since the suit patents were old, they should be presumed to be valid. The learned Single Judge did so for two reasons. First, the learned Single Judge found – much like in the present appeal where it is the stated case that ELT-O is covered under both IN’ 176 and the suit patent IN’ 161 – that there was an overlap in the genus patent and the species patent. And second, that the presumption of validity exists only till such time the patent is challenged and the challenge is credible. The relevant extract of the said decision is set out below:
“51. Furthermore, the argument advanced on behalf of the plaintiffs that since the suit patents are old and thus, should be presumed to be valid cannot be accepted for two reasons.
i. First, there is a period of overlap between the genus patent i.e. IN 147 and the species patent i.e. IN 625. The defendants, in this case, chose to wait [in line with arguments advanced in their defence of the suit actions] till such time the validity period of the genus patent i.e. IN 147 expired.
ii. Second, as indicated above, the scheme of the Act does not foreclose the right of the defendants in defence to an infringement action to question the validity of the patent. Section 107 of the Act, expressly confers a right on the defendants to raise, in defence, in an infringement suit, all those grounds on which the patent can be revoked under Section 64 of the very same Act. Therefore, the judgment in Bristol-Myers Squibb Company v. J.D. Joshi, 2015 SCC OnLine Del 10109, if read in context, would demonstrate that it has not emasculated the right of the defendant, as conferred under the Act, to challenge the validity of the patent. The presumption of validity exists only till such time the patent is challenged – a challenge which is credible and no further. In my opinion, if the plaintiffs’ argument was to be accepted, then, it would have to be held that the older the patent, the stronger the firewall. Such an interpretation, in my view, would be contrary to the plain words of the Statute.
[Emphasis added]
45. The appeal against the said decision was dismissed by the Division Bench of this Court as being without any merit.
46. In the present case, the learned Single Judge held that even if a prima facie ground for revocation is made out, revocation is not automatic as the patent authority retains discretion not to revoke the patent if not absolutely necessary. And, the vulnerability to revocation must also be adjudged on the same standard. The learned Single Judge also concluded that this standard is therefore, high rather than low. It was further observed that the credible challenge occupies a higher pedestal than challenge, which is merely worthy of consideration. The learned Single Judge held that “When an infringer seeks to defend infringement on the ground that the patent he infringes is invalid, the onus, to prove such invalidity heavily lies on him. This standard has to be met, when applying the principle of “credibility””. The standard as articulated in the impugned judgement is in clear variance with the decision of the Division Bench of this court in F. Hoffmann-LA Roche Ltd. & Anr. v. Cipla Ltd.7. In the said case, the Division Bench had expressly rejected the contention that the defendant has a heavy burden to discharge as it has to establish a stronger prima facie case. It is apparent that in the present case, the learned Single Judge has applied a higher standard for examining whether a credible challenge to the validity of a patent is made out, than as explained by the Division Bench. In effect, the learned Single Judge has read in a presumption as to the validity of the patent, where none exists. Obviously, a challenge to a patent, that is insubstantial, would be wholly insufficient to resist an order of interdiction. However, if a prima facie ground of revocation is made out, the threshold standard of credible challenge is met notwithstanding the discretion vested with the patent authority in regard to revocation of the patent. The fact that the patent authority may have the discretion not to revoke the patent despite a ground for the same being established, is not a relevant consideration for granting an interim injunction restraining the infringement of a patent on the ground that the defendant has not met the threshold standard of a credible challenge to the validity of the patent, if a prima facie ground for revoking the patent is made out.
47. If the defendant raises a substantial challenge, which merits a trial, the question whether an injunction ought to be granted would necessarily have to be determined on other considerations for grant of such injunctions including balance of convenience and irreparable harm.
Natco’s principal challenge
48. Natco’s principal challenge to the validity of IN’161 is premised on basis that the same substance was claimed and covered in IN’176. As noted at the outset, there is no dispute that ELT-O was covered in IN’176. Novartis also claims that Natco’s product TROMBOPAGTM would also infringe IN’176 during its term. It is Novartis’ contention that although, ELT-O was covered under IN’ 176, it was not disclosed and therefore, Natco’s challenge to IN’161 on the ground of prior claiming and prior publication fails. Additionally, the challenge on the ground of l