Date: 20220411  
Docket: T-419-20  
Citation: 2022 FC 417  
Toronto, Ontario, April 11, 2022  
PRESENT: The Honourable Madam Justice Furlanetto  
BETWEEN:  
MERCK SHARP & DOHME CORP.  
AND MERCK CANADA INC.  
Plaintiffs  
and  
PHARMASCIENCE INC.  
Defendant  
PUBLIC JUDGMENT AND REASONS  
(Identical to the Confidential Judgment and Reasons  
Issued on March 28, 2022)  
[1]  
This judgment arises from a patent infringement action brought under subsection 6(1) of  
the Patented Medicines (Notice of Compliance) Regulations, SOR/93-133 [PMNOC  
Regulations]. The patent at issue is Canadian Patent No. 2,529,400 [400 Patent]. The innovative  
drug relating to the action is JANUVIA®, which is used to treat type 2 diabetes.  
Page: 2  
Merck Canada Inc. is the “first person” in accordance with the PMNOC Regulations.  
[2]  
Merck Sharp & Dohme Corp. is the registered owner of the 400 Patent and is a party to the  
action pursuant to subsection 6(2) of the PMNOC Regulations.  
[3]  
The Plaintiffs [collectively, Merck] claim that the making, constructing, using or selling  
by the Defendant Pharmascience Inc. [PMS] of its sitagliptin phosphate tablets in strengths of  
25 mg, 50 mg, and 100 mg in accordance with PMS’ Abbreviated New Drug Submission will  
infringe at least one of claims 4-7, 19, 20, 22, 24 and 26 [Asserted Claims] of the 400 Patent.  
PMS asserts in defence that the 400 Patent is invalid for obviousness and/or insufficiency.  
[4]  
The parties agreed to a stipulation that the only issue to be adjudicated at trial was the  
validity of the 400 Patent. The stipulation provided that should the court find any of the Asserted  
Claims of the 400 Patent to be valid, the Order sought by the Plaintiffs in the action should issue  
with the relief requested by the Plaintiffs.  
[5]  
For the reasons that follow, I find the Asserted Claims of the 400 Patent valid and that the  
relief sought should be ordered accordingly.  
I.  
Background  
[6]  
The 400 Patent is listed on the Patent Register in association with the medicine sitagliptin  
phosphate monohydrate. Sitagliptin exists as a dihydrogen phosphate salt in crystalline  
monohydrate form in the tablets sold as JANUVIA®. Sitagliptin is the active ingredient in the  
drug product.  
Page: 3  
[7]  
In type 2 diabetes, cells develop insulin resistance such that the presence of insulin in the  
blood does not stimulate cells to take up glucose, or the pancreas does not produce enough  
insulin to overcome the resistance. Thus, glucose accumulates in the blood.  
[8]  
Sitagliptin inhibits dipeptidyl peptidase-4 [DPP-4, DP-IV or DPP-IV], an enzyme that  
degrades one of the peptides (Glucagon-Like Peptide-1 [GLP-1]) that stimulates the secretion of  
insulin. This inhibitory effect modulates the level of insulin and glucose in the blood. Sitagliptin  
acts only when glucose is elevated in the bloodstream, thereby reducing the risk of hypoglycemia  
caused by low glucose levels.  
[9]  
In 2006, JANUVIA® became the first DPP-4 inhibitor approved by the United States  
Food and Drug Administration [FDA] for the treatment of diabetes. It was approved by Health  
Canada in 2007.  
[10] This action initially alleged infringement of three patents - the 400 Patent, as well as two  
other patents listed on the Patent Register in association with sitagliptin phosphate monohydrate  
Canadian Patent Nos. 2,536,251 [251 Patent] and 2,450,740 [740 Patent]. However, the  
allegations in respect of the 251 Patent and 740 Patent were discontinued prior to trial.  
[11] The 740 Patent is the corresponding Canadian national phase patent of Patent  
Co-operation Treaty [PCT] patent application WO 03/004498 [WO498]. WO498 discloses a  
genus of compounds that includes the chemical compound now known as sitagliptin. It  
specifically exemplifies sitagliptin, amongst other compounds, both as a free base and  
Page: 4  
hydrochloride salt and refers to other salts and crystalline forms as being within its scope.  
WO498 is referenced in the 400 Patent as discussed further below.  
[12] The 400 Patent is directed to the dihydrogenphosphate [DHP] salt of sitagliptin and its  
crystalline monohydrate form, a process for making the DHP salt of sitagliptin as a crystalline  
monohydrate, its formulation as a pharmaceutical composition and its use to treat diseases  
affected by the inhibition of DPP-4, such as type 2 diabetes.  
II.  
Witnesses  
[13] Seven experts gave testimony at the trial; three experts were called by PMS and four by  
Merck. The parties agreed to stipulations as to the expertise of all expert witnesses.  
A.  
PMS Experts  
[14] Dr. Vassil Elitzin obtained his Ph.D. from Stanford University in 2004, specializing in  
the synthesis of naturally occurring chemical compounds. He is currently the Director of  
Chemistry, Manufacturing and Controls and Chief Chemist at LI-COR Biosciences. He was  
previously a principal scientist in the Chemical Development group at GlaxoSmithKline. His  
work focuses on the development of active pharmaceutical ingredients and dosage forms from  
discovery to commercialization. Dr. Elitzin was admitted as an expert in synthetic organic  
chemistry and compound characterization, with particular expertise in developing, making, and  
characterizing different salt and crystalline forms of compounds.  
Page: 5  
[15] Dr. Elitzin provided an opinion on whether the Asserted Claims of the 400 Patent would  
have been obvious to the person skilled in the art [PSA]. He also reviewed some of Merck’s  
internal documents and provided an opinion on the course of conduct taken by the inventors  
towards obtaining the DHP salt of sitagliptin and the crystalline monohydrate.  
[16] PMS highlights Dr. Elitzin’s experience in industry; however, he was not active in  
industry at the relevant date for assessing obviousness of the 400 Patent. His observations as to  
what was happening at the time are limited to his understanding from the literature and from  
lectures attended during his Ph.D. studies. While in general I found Dr. Elitzin’s testimony to be  
helpful to the Court, as highlighted below, he was selective in accepting statements from leading  
authorities as to the common general knowledge in the art, some of which came from  
publications he had relied on for his own report. I have therefore approached his evidence in  
those areas with caution and in some instances have preferred the evidence of Merck’s experts  
over that of Dr. Elitzin in those areas.  
[17] Dr. Mark Hollingsworth is an Emeritus Research Professor at Kansas State University.  
He has worked in academia since 1987, first as an Assistant Professor in the Chemistry  
Department at the University of Alberta, then as an Assistant Professor in the Chemistry  
Department at Indiana University, and later as an Associate Professor in the Chemistry  
Department at Kansas State University, where he worked from 1998 to August 2021 when he  
retired. He has taught and lectured extensively on solid state chemistry and the characterization  
of crystalline forms. Dr. Hollingsworth was admitted as an expert in organic chemistry,  
particularly solid state organic chemistry, including the characterization of the solid state of  
Page: 6  
organic compounds and their properties, with expertise in analytical techniques for  
characterizing organic solids and the crystallization of organic solids. He was further qualified as  
an expert in the fields of crystal growth and crystal engineering with expertise in analytical  
techniques for characterizing organic solids and the crystallization of organic and inorganic  
compounds, including by x-ray crystallography.  
[18] Dr. Hollingsworth provided opinions on claims 4-7, 19, 20 and 24 of the 400 Patent and  
on the elements of the test for obviousness relating to those claims, both before and after a  
review of some of Merck’s internal documents. He also analyzed Merck’s raw data files relating  
to the x-ray powder diffraction [XRPD] characterization work done during Merck’s polymorph  
screening and provided an analysis of this work, including with respect to the limitations found  
in claims 5-7 of the 400 Patent. I found Dr. Hollingsworth to be a knowledgeable and credible  
witness.  
[19] Dr. James E. Foley is a retired clinical research director with experience in drug  
development relating to diabetes treatments. He has worked in the field of diabetes since the  
1970s and began working on DPP-4 inhibitors in 1995. Dr. Foley was involved in the evaluation  
of the Novartis candidate drug DPP-728 as a DPP-4 inhibitor in patients, and in the clinical  
development and profiling of LAF-237 (vildagliptin) as a DPP-4 inhibitor. Dr. Foley was  
admitted as an expert in pharmacology and drug development, including specifically the history  
of development of DPP-4 inhibitors as a treatment for diabetes. He was further admitted as  
having expertise in drug discovery and development, and in lead compound identification.  
Page: 7  
[20] Dr. Foley provided background on the development of Novartis’ DPP-728 and  
vildagliptin compounds as DPP-4 inhibitors. He gave opinions on claims 22 and 26 of the 400  
Patent and on the elements of the test for obviousness as it related to those claims. I found  
Dr. Foley to be a knowledgeable and credible witness.  
B.  
Merck Experts  
[21] Dr. James Wuest is a Professor of Chemistry at the Université de Montréal where he has  
worked since 1981. He is also the Canada Research Chair in Molecular Materials. He was  
previously an Assistant Professor of Chemistry at Harvard University and a Research Fellow at  
Harvard Medical School. Dr. Wuest specializes in molecular design and synthesis of solid state  
forms, including salt forms, crystalline forms and their polymorphs. He has extensive experience  
synthesizing compounds and characterizing their resulting structures and properties. Dr. Wuest  
was admitted as an expert in molecular design and synthesis, with particular expertise in solid  
state organic chemistry, including the characterization of the solid state of organic compounds  
and their properties, with expertise in analytical techniques for characterizing organic solids and  
the crystallization of organic compounds.  
[22] Dr. Wuest provided opinions on claims 4-7, 19, 20, 22 and 24 of the 400 Patent and  
whether those claims would have been obvious at the relevant date. He also responded to the  
opinions of Drs. Elitzin and Hollingsworth.  
[23] PMS highlights that Dr. Wuest has never worked on a drug development team. I note that  
this criticism also applies to PMS’ own expert, Dr. Hollingsworth. While Dr. Wuest’s opinions,  
Page: 8  
like those of Dr. Hollingsworth, must be considered with this limitation in mind, where opinions  
relate to scientific principles and information that can be assessed from knowledge of the  
techniques used and literature available at the time, it does not diminish the weight to be attached  
to the opinions.  
[24] PMS further highlights that Dr. Wuest has testified in a number of cases for innovators,  
including some for Merck, and was retained in litigation in the U.S. relating to the corresponding  
patent to the 400 Patent. It suggests that Dr. Wuest has ties to Merck because Dr. Wuest has met  
Merck’s inventor Dr. Wenslow and had planned to give a lecture at Dr. Wenslow’s company. I  
find these criticisms unpersuasive. Dr. Wuest does not receive any financial support for his  
research from Merck. His involvement in past litigation is not uncommon for an accomplished  
scientist in the field and he is not currently involved in the U.S. proceeding on the corresponding  
400 Patent. As made clear during his cross-examination, Dr. Wuest has not discussed this  
litigation or sitagliptin with Dr. Wenslow and his lecture at Dr. Wenslow’s company is unrelated  
to the litigation. There is no basis on the evidence before me to suggest that Dr. Wuest is not an  
independent, unbiased witness.  
[25] In general, I found Dr. Wuest to be a knowledgeable witness who was of assistance to the  
Court. However, his view of certain background passages in the 400 Patent relating to inhibitory  
activity appeared strained and his positon as to whether he could speak to issues involving the  
potency of compounds and their therapeutic use unclear. I have therefore approached his  
evidence on those issues with caution.  
Page: 9  
[26] Dr. Martyn C. Davies is an Emeritus Professor and pharmaceutical consultant who  
recently retired from the University of Nottingham where he served in various roles, including as  
the Head of the Pharmaceutical Sciences and Pharmacy School. He has worked for many years  
as a consultant and has significant practical experience developing, formulating and  
characterizing pharmaceutical formulations and advanced drug delivery systems. Dr. Davies  
was admitted as an expert in pharmaceutical formulation and drug delivery, including with  
respect to pre-formulation assessment, formulation design and development, manufacture,  
characterization, testing and analysis, including for solid oral dosage forms.  
[27] Dr. Davies provided an opinion on the issue of obviousness with respect to claims 4-7  
and 22 of the 400 Patent from the perspective of the skilled formulator. He also responded to the  
opinion of Dr. Elitzin on those claims from this perspective.  
[28] PMS highlights Dr. Davies history with pharmaceutical litigation on behalf of innovators.  
It also suggests that Dr. Davies attempted to bolster the evidence of other Merck witnesses  
during his testimony. PMS refers to two passages during Dr. Davies cross-examination where  
Dr. Davies refers to testimony of other Merck witnesses when addressing a question asked. In  
one instance, the testimony refers to Dr. Wenslow and in the other instance Dr. Wuest. While I  
agree with PMS’ criticism of the first instance, the second instance appeared to result from  
Dr. Davies being asked about an area not covered by his expertise. In any event, I do not  
consider these two passages to pervade the remaining testimony provided by Dr. Davies. In my  
view, Dr. Davies was a knowledgeable witness and I consider his testimony to be of assistance to  
the Court.  
Page: 10  
[29] Dr. Richard E. Lewanczuk is an endocrinologist and the Senior Medical Director of  
Health System Integration for Alberta Health Services. He has held various roles in that  
organization since the 1990s. He is also a professor of medicine and physiology at the  
University of Alberta with a research background in diabetes, hypertension, chronic disease  
management, therapeutic natural products, and drug-disease interactions. Dr. Lewanczuk was  
admitted as an expert in internal medicine and endocrinology with extensive expertise in  
managing and treating type 2 diabetes. Dr. Lewanczuk was further qualified as an expert in the  
conduct of clinical trials for pharmaceutical agents for use in the treatment of type 2 diabetes.  
[30] Dr. Lewanczuk provided background on type 2 diabetes and the history of different  
therapies used to treat type 2 diabetes, including the role and impact of JANUVIA® and other  
Merck drug products. Dr. Lewanczuk was also asked to respond to Dr. Foley’s opinions  
regarding obviousness and claims 22 and 26 of the 400 Patent.  
[31] PMS criticizes Dr. Lewanczuk for failing to disclose that he had received honoraria from  
Merck for sitting on an advisory panel and giving a lecture. This information was readily  
acknowledged by Dr. Lewanczuk on cross-examination, where he clarified that honoraria from  
pharmaceutical companies are common and thus are not included in his CV due to the abundance  
in which they are provided. Dr. Lewanczuk confirmed that he had never received research  
support from Merck. I do not consider the omission of the honoraria to affect Dr. Lewanczuk’s  
credibility or suggest any form of bias. Overall, I viewed Dr. Lewanczuk as a forthright witness  
who readily acknowledged and helped to clarify these omissions.  
Page: 11  
[32] PMS also criticized Dr. Lewanczuk for providing views on salt selection and whether  
sitagliptin was previously disclosed in the prior art, when this evidence was admittedly outside of  
his expertise. I agree that there were a few instances where Dr. Lewanczuk strayed outside his  
expertise, principally when seeking to respond to comments on these same issues made in  
Dr. Foley’s report. I have not given those aspects of his opinion any weight when reaching my  
decision.  
[33] While I consider Dr. Lewanczuk’s report to have went into unnecessary detail in certain  
areas, his comments on claims 22 and 26 and his response to Dr. Foley’s opinion on those claims  
were of assistance to the court.  
[34] Dr. William R. Roush is the Executive Vice President of Chemistry of IFM  
Therapeutics where he is responsible for leading drug discovery medicinal chemistry research  
activities. He has over 40 years of experience in organic and medicinal chemistry and is an  
Emeritus Professor of Chemistry at the Scripps Research Institute. Between 2005-2017 he was  
the former Executive Director of Medicinal Chemistry in the Drug Discovery Division of  
Scripps’ Translational Research Institute where he directed research for optimizing drug  
candidates for drug discovery projects internal to Scripps. Prior to 2017, he also acted as a  
consultant to pharmaceutical and biotechnology companies. Dr. Roush was admitted as an expert  
in organic and medicinal chemistry, and specifically in the areas of synthesis and  
characterization of organic compounds. Dr. Roush was further qualified as having expertise in  
drug discovery and development and in lead compound identification.  
Page: 12  
[35] Dr. Roush was asked to opine on the 400 Patent and whether the PSA would have chosen  
to investigate sitagliptin or any of its salts as a potential DPP-4 inhibitor for treating type 2  
diabetes as of June 24, 2003, without having the benefit of the 400 Patent. He was also asked to  
respond to Dr. Foley. In doing so, he provides opinions on claims 4, 22 and 26 of the 400 Patent  
and whether claims 22 and 26 are obvious. In providing these opinions, Dr. Roush conducts a  
prior art search and reviews the steps a medicinal chemist would take to identify a lead candidate  
for drug development.  
[36] PMS asserts that Dr. Roush has extensive ties to brand pharmaceutical companies. It  
highlights that at the relevant date Dr. Roush was in academia and not in industry. PMS criticizes  
Dr. Roush for asserting that he had acquired some expertise on DPP-4 inhibitors after preparing  
his report and for dedicating a portion of his report to the success of JANUVIA®, while  
admittedly having no personal knowledge of that success.  
[37] I agree these are critiques that can be made of Dr. Roush’s evidence. However, I do not  
agree that Dr. Roush presented as a biased witness or that these critiques establish that the  
substance of Dr. Roush’s evidence is not credible. Further, I do not consider Dr. Roush’s  
comments on the process involved in lead candidate identification to be affected by the date of  
his experience. The bigger problem the Court has with Dr. Roush’s evidence is that aspects of it  
are from the perspective of the medicinal chemist who is evaluating and directing Structure  
Activity Relationship [SAR] studies on compounds of the prior art to advance the next stages of  
research. As will be discussed further below, this is not a focus of the 400 Patent. While I will  
need to consider whether the PSA would be motivated to move from WO498 to the inventive  
Page: 13  
concept of the 400 Patent, I do not consider a separate medicinal chemist to be a necessary  
member of the skilled team interpreting the 400 Patent. As such, certain aspects of Dr. Roush’s  
evidence are not relevant to my analysis.  
C.  
Fact Witnesses  
[38] There were two fact witnesses introduced by the Plaintiffs. The first, Christine Vincent, is  
a law clerk with the solicitors for the Plaintiffs. She provided an affidavit attaching several  
documents obtained from Health Canada’s website associated with generic submissions  
involving sitagliptin. The affidavit also attached pleadings from the Merck Sharp & Dohme Corp  
v JAMP Pharma Corporation T-667-20 proceeding. The significance of these pleadings to the  
present action was not made known to the Court through the Plaintiffs’ submissions.  
Ms. Vincent’s affidavit was accepted and it was agreed that she would not be cross-examined.  
[39] The second fact witness, Dr. Robert M. Wenslow, is one of the inventors of the 400  
Patent. Dr. Wenslow was the discovery representative for the Plaintiffs and, on agreement of the  
parties, was the only inventor examined under Rule 237(4) of the Federal Courts Rules,  
SOR/98-106 [Federal Courts Rules].  
[40] Dr. Wenslow joined Merck in 1997 as a Senior Research Chemist in the Process  
Research & Development Department. At the time of sitagliptin’s development, Dr. Wenslow  
led a team of scientists in the Physical Measurements group, which was then part of the  
Analytical Research department, and directly supervised the work of his co-inventors  
Drs. Russell Ferlita and Alex Chen, as well as Yaling Wang.  
Page: 14  
[41] The Physical Measurements Group formed part of the broader multi-disciplinary DPP-4  
project team that was involved in sitagliptin’s development. The primary responsibility of the  
Physical Measurements Group was to perform solid state characterization of candidate drug  
compounds, including XRPD, solid state nuclear magnetic resonance [NMR] spectroscopy,  
differential scanning calorimetry [DSC] and thermogravimetric analysis [TGA]. As a lead  
member of the group, Dr. Wenslow regularly discussed and collaborated with the broader DPP-4  
project team and reviewed research reports and data generated on sitagliptin, including those of  
the remaining co-inventors Drs. Karl Hansen, Ivan Lee, Stephen Cypes and Vicky Vydra.  
[42] As admitted by Dr. Wenslow, he was not directly assigned to the sitagliptin project until  
March/April 2002, around the time the phosphate salt was chosen for further development (Trial  
Transcript [TT], Volume [V]4, Page [P]:349 Line [L]:8-13; TT V5, P:190 L:18). As one of his  
primary responsibilities upon joining the group, he reviewed the development work up to that  
point and had discussions with other members of the DPP-4 group to familiarize himself with the  
work that had been completed prior to his joining the project (TT V4, P:349 L:16 P:350 L:1).  
[43] Dr. Wenslow provided an overview of the invention story, both through oral testimony  
and through affidavit evidence, including with reference to various documents outlining the  
history of the invention. PMS accepted all but one of the documents as being authentic and the  
vast majority for the truth of their contents by way of joint agreement of the parties.  
[44] While it was not disputed that Dr. Wenslow could appear at trial and submit an affidavit  
introducing those documents covered by the agreement, large portions of the content of his  
Page: 15  
affidavit were hotly contested as being hearsay, improper opinion evidence, covering subject  
matter beyond the pleadings, and/or being contrary to rules 232 and 248 of the Federal Courts  
Rules. In light of the timing of these objections, and on the basis of their nature and number,  
which in many cases included parsing words and/or sentences from within paragraphs, it was  
determined that the Court would benefit from hearing Dr. Wenslow’s full oral testimony at trial  
and that the admissibility of the objected to portions of his affidavit evidence would be dealt with  
as a preliminary matter as part of this decision. Time was reserved for argument on the motion to  
take place at the close of the evidence. The parties also agreed that counsel for PMS would  
provide an update after Dr. Wenslow testified as to whether any objections would be withdrawn.  
However, in the end, the motion was not narrowed. Instead, PMS sought to add additional  
objections arising from Dr. Wenslow’s oral testimony. PMS was directed to identify the  
additional objections and the impugned portions of the affidavit to which they related.  
[45] As determined by oral ruling during argument on the motion, after-the-fact objections to  
direct testimony not related to impugned portions of the affidavit were rejected as it was viewed  
that the failure of PMS to raise the objection during the testimony precluded Merck from  
properly responding to the objections at the relevant time and potentially curing any deficiency:  
Teva Canada Ltd v Pfizer Canada Inc, 2017 FC 526 (Venlaflaxine 2) at paras 32- 42. Answers  
given on cross-examination were also rejected as being improper objections as such answers  
were elicited by PMS directly. The remaining objections are set out in the Appendix attached to  
this decision. The Appendix lists the original objections to the affidavit, along with the  
objections to the asserted related oral testimony and provides my specific dispositions on each.  
Below, I provide some general comments on the four primary grounds of objection raised.  
Page: 16  
(1)  
Hearsay  
[46] Hearsay evidence is evidence that is adduced for its truth without the contemporaneous  
opportunity to cross-examine the declarant: R v Khelawon, 2006 SCC 57 [Khelawon] at para 35.  
Hearsay evidence is presumptively inadmissible unless it falls under one of the recognized  
exceptions to the hearsay rule: Khelawon at paras 2, 34, and 42; Pfizer Canada Inc v Teva  
Canada Limited¸ 2016 FCA 161 [Venlafaxine] at paras 86-87.  
[47] Hearsay evidence may also be admitted under the principled approach if the party  
adducing it can establish it is necessary and reliable: Khelawon at paras 42; Coldwater First  
Nation v Canada (Attorney General), 2019 FCA 292 [Coldwater] at para 48. A statement is  
reliable if there is no real concern about whether the statement is true because of the  
circumstances in which it was made, or if the circumstances allow its truth and accuracy to be  
sufficiently tested (Khelawon at paras 61-63), such as if it is supported by contemporaneous  
documentary evidence (Coldwater at para 49-50). Necessity is a flexible criterion and is not to be  
equated with the unavailability of a witness: Khelawon at para 78; Coldwater at para 53. The  
nature and practical exigencies of a proceeding can impact the evaluation of necessity  
(Coldwater at paras 54-55), such as avoiding an impracticably large number of affidavits or  
witnesses, and the resulting promotion of speed and efficiency (Coldwater at para 59; R v  
Baldree, 2013 SCC 35 [Baldree] at para 72). One criterion may have an impact on the other  
(Khelawon at paras 46 and 77) such that if the reliability of the impugned evidence is sufficiently  
established, the necessity requirement can be relaxed (Baldree at para 72).  
Page: 17  
[48] This modern approach to hearsay recognizes that evidence may be admissible from  
departmental supervisors or individuals who take on an oversight role and although not  
performing all of the work, have enough personal knowledge to testify about the conduct,  
activities and events that have taken place: Coldwater at paras 42-46.  
[49] PMS argues that much of Dr. Wenslow’s evidence consists of statements made about  
work performed by others or their state of mind and reasoning processes. It asserts that  
Dr. Wenslow had a limited supervisory role that is insufficient to allow him to testify broadly  
about the conduct, activities, and events in Merck’s sitagliptin development process. It contends  
that if Merck wanted this evidence admitted, it needed to call other inventors or Merck  
employees as witnesses.  
[50] Merck argues that much of the impugned evidence is not hearsay as it arises from  
Dr. Wenslow’s personal knowledge gained in his supervisory capacity. It asserts that the  
impugned evidence is admissible under the principled approach to hearsay.  
[51] As set out further in the Appendix, the majority of the objections made based on hearsay  
cannot succeed, as they are either not hearsay and/or are admissible under the principled  
approach to hearsay. I find that Dr. Wenslow’s role within the team was such that he functioned  
in a larger supervisory capacity that allows him to speak about many aspects of the team’s  
experimental work. Moreover, as to reliability, the impugned statements generally refer to  
information from documents that have already been accepted by PMS as being admissible for the  
Page: 18  
truth of their contents without further proof, or which raise facts that have otherwise already been  
admitted into evidence.  
[52] As to necessity, it is difficult to reconcile the inconsistent position taken by PMS to agree  
to accept Dr. Wenslow’s testimony as the only testimony of the invention story for the purpose  
of discovery, while asserting it is now insufficient for trial. In some instances if PMS’ objections  
were to prevail, they would result in PMS reading-in certain facts from discovery as its evidence,  
while requiring Merck to introduce those same facts through additional witnesses. The PMNOC  
Regulations seek to promote efficiencies and to avoid the impracticality of a large number of  
affidavits or witnesses where such testimony is not required. The overly technical position taken  
by PMS, splitting and parsing sentences, where the reliability of the impugned statements are  
supported by contemporaneous documents or other evidence runs contrary to the fundamental  
guidelines set out in section 6.09 of the PMNOC Regulations.  
(2)  
Opinion Evidence  
[53] The general rule is that a fact witnesses must limit their testimony to the facts of which  
they are aware and not to inferences or opinions drawn from those facts: White Burgess Langille  
Inman v Abbott and Haliburton Co, 2015 SCC 23 at para 14. This rule applies unless the witness  
is in a better position than the trier of fact to form the conclusions made, the conclusions are ones  
that a person of ordinary experience can make, the witness has the experiential capacity to make  
the conclusions, or where giving opinions is a convenient mode of stating facts too subtle or  
complicated to be narrated as facts: Toronto Real Estate Board v Commissioner of Competition,  
Page: 19  
2017 FCA 236 at para 79. The line between fact and opinion is not always clear: Graat v The  
Queen, [1982] 2 SCR 819 at 835.  
[54] PMS objects to all or part of 26 paragraphs of Dr. Wenslow’s affidavit and related oral  
testimony on the basis that he is providing impermissible opinion evidence. PMS asserts that  
Dr. Wenslow gives unhelpful, and potentially misleading opinion evidence that does not meet  
the limited and narrow exceptions for a fact witness. Merck asserts that many of the alleged  
objections relate to factual evidence regarding the observations and conclusions drawn by Merck  
employees at the time. Merck argues that if any opinion evidence is provided, it is admissible  
because Dr. Wenslow is well positioned to provide that evidence and has the experiential  
capacity to do so.  
[55] The majority of the statements alleged to be opinion set out the reasoning behind the  
choices made by the DPP-4 development team and are admissible for this purpose. While some  
of the statements are technical in nature, this does not automatically negate the statements,  
especially where such statements reflect the understanding of the development team at the time.  
In some cases, Dr. Wenslow adds “gloss” to his description of events. However, in most cases  
such comments are not of such a character that would mislead the Court or be prejudicial to PMS  
and do not warrant the exclusion of the evidence. Such comments can most effectively be dealt  
with by considering the weight to be given to the statement. With few exceptions, the objections  
made in this category are dismissed.  
Page: 20  
(3)  
Beyond the Pleadings  
[56] Relevance is a threshold requirement for the admission of evidence. Evidence is relevant  
if it tends to establish a fact in issue. To succeed on showing that evidence should be excluded  
for relevance, the moving party must show that the evidence is “obviously irrelevant”: Coldwater  
at para 14. PMS has failed to do so in this case.  
[57] The impugned evidence is relevant to the obvious to try analysis and the inventor’s  
course of conduct. While all of the details of Merck’s invention story were not specifically  
pleaded in Merck’s Reply, the evidence is clearly responsive to the issues in the proceeding and  
to PMS’ evidence. The objections in this category accordingly have been dismissed.  
(4)  
Rule 232 and 248 Objections  
[58] Rules 232 and 248 aim to avoid a party being prejudiced by the late disclosure of  
documents and to prohibit “trial by ambush”: Airbus Helicopters, S.A.S. v Bell Helicopter  
Textron Canada Limitée, 2017 FC 170 at para 81; Apotex Inc v Sanofi Aventis, 2010 FC 481 at  
para 6. Rule 248 only applies where a party fails to produce documents, or refuses to answer a  
proper question and later seeks to introduce such evidence at trial: Human Care Canada Inc v  
Evolution Technologies Inc, 2018 FC 1302 [Human Care] at paras 60-61; Pollard Banknote  
Limited v BABN Technologies Corp, 2016 FC 883 at para 215. The Court retains the discretion  
to admit evidence that is given in violation of rule 248.  
[59]  
In general, where a party seeks to introduce evidence that is perceived as being  
inconsistent with testimony given on discovery, the correct approach is to present the  
Page: 21  
inconsistency to the witness through cross-examination: §16.178, Sidney N Lederman, Alan W  
Bryant and Michelle K Fuerst, ed, Sopinka, Lederman and Bryant: The Law of Evidence in  
Canada, 5th ed (Toronto, LexisNexis Canada, 2018); JD Irving Limited v Siemens Canada  
Limited, 2016 FC 69 at para 43.  
[60] PMS raises 14 objections under rules 232 and 248. One of these objections is to an email  
that was not disclosed prior to Dr. Wenslow’s discovery or in response to undertakings. The  
email chain confirms the date certain experiments were conducted. This information is not  
controversial in light of the admission into evidence of other details relating to those experiments  
in documents that have been accepted as being admissible for the truth of their contents. As a  
result, I see no prejudice to admitting the document.  
[61] The remainder of the rule 248 objections fall into three groups. The first group relate to  
subject matter that was not refused during discovery, but rather relate to statements that PMS  
perceives as being inconsistent. These are not appropriate for a rule 248 objection. The second  
group are based on refusals to very specific points that have only a tenuous connection to the  
evidence being objected to. The third group relate to objections that lack foundation or were not  
sufficiently particularized in PMS’ submissions.  
[62] In addition to the formal objections raised to Dr. Wenslow’s evidence, PMS also seeks an  
adverse credibility finding against Dr. Wenslow. It asserts that this finding is separate and  
distinct from the issue of admissibility, yet sits “hand in glove” with these admissibility  
objections. It argues that Dr. Wenslow has not acknowledged that his evidence is grounded in  
Page: 22  
hearsay and that his affidavit is based on information and belief. Pursuant to Rule 81(2) of the  
Federal Courts Rules, PMS asserts that an adverse inference must be drawn as Merck has not  
provided evidence from persons having personal knowledge of material facts.  
[63] While evidence was not provided by those who conducted the experiments, as set out  
earlier in my decision, in most instances I consider Dr. Wenslow to have sufficient knowledge  
through his interaction within the DPP-IV development team to be able to provide the evidence  
given. Such evidence outlines the invention story supported by the contemporaneous documents,  
accepted as being admissible for the truth of their contents. I find such evidence to be credible  
and any elaborations given shall be addressed through weight.  
III.  
Issues  
[64] The following issues were identified in the parties’ Joint Statement of Issues as being  
those in dispute for this action:  
A.  
Obviousness: As of the claim date (June 24, 2003), would the subject matter  
defined by the Asserted Claims have been obvious and/or obvious to try to a  
PSA?  
B.  
Insufficiency: Does the 400 Patent satisfy the requirements of  
subsections 27(3)(a) and (b) of the Patent Act, R.S.C., 1985, c. P-4 (the Patent  
Act)?  
[65] In addition to these issues raised by the parties, and before determining the validity of the  
400 Patent, the Court must construe the Asserted Claims of the 400 Patent. In order to do so, the  
Court must put the 400 Patent in context by determining whether it is a selection patent and by  
defining the PSA of the 400 Patent.  
Page: 23  
IV.  
The 400 Patent  
[66] The 400 Patent is entitled Phosphoric Acid Salt of a Dipeptidyl Peptidase-IV Inhibitor”.  
It is the national phase entry of a PCT application filed on June 18, 2004 based on a US priority  
patent application, filed June 24, 2003. The 400 Patent will expire on June 18, 2024.  
[67] The Field of the Invention, at page 1 of the 400 Patent, states that the invention of the 400  
Patent relates to the DHP salt of the compound 4-oxo-4-[3-(trifuoromethyl)-5,6-  
dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine, now  
known as sitagliptin, which is a potent inhibitor of DPP-4. It explains that the DHP salt and its  
crystalline hydrates are useful for the treatment and prevention of diseases and conditions for  
which an inhibitor of DPP-4 is indicated, in particular type 2 diabetes, obesity and high blood  
pressure. It also states that the invention further concerns pharmaceutical compositions  
comprising the salt and crystalline hydrates and processes for preparing them.  
[68] The Background to the 400 Patent refers to several articles relating to DPP-4 inhibition  
for the treatment of type 2 diabetes. It also refers to Merck & Co’s prior patent application  
WO498 as disclosing a class of compounds that are potent inhibitors of DPP-4 and to the  
disclosure of 4-oxo-4-[3-(trifuoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-  
(2,4,5-trifluorophenyl)butan-2-amine within this class.  
[69] The summary of the invention characterizes the invention as the DHP salt of 4-oxo-4-[3-  
(trifuoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-  
trifluorophenyl)butan-2-amine and its crystalline hydrates; in particular, the crystalline  
Page: 24  
monohydrate. It explains that the DHP salt and crystalline hydrates have advantages in the  
preparation of pharmaceutical compositions, such as “ease of processing handling, and dosing”.  
They also exhibit “improved physical and chemical stability, such as stability to stress, high  
temperatures and humidity, as well as improved physicochemical properties, such as solubility  
and rate of solution”, which make them particularly suitable for pharmaceutical dosage forms.  
The section states that the invention further concerns “pharmaceutical compositions containing  
the novel salt and hydrates as well as methods for using them as DP-IV inhibitors, in particular  
for the prevention or treatment of Type 2 diabetes, obesity, and high blood pressure.”  
[70] The Detailed Description includes as structural formulas (I), (II) and (III) respectively,  
depictions of the monobasic DHP salt of 4-oxo-4-[3-(trifuoromethyl)-5,6-  
dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine in its  
racemic, R-enantiomer and S-enantiomer forms.  
[71] The 400 Patent teaches that the monobasic DHP salt of 4-oxo-4-[3-(trifuoromethyl)-5,6-  
dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine is a 1:1  
salt with one molar equivalent of mono-protonated compound to one molar equivalent of DHP  
anion. It also teaches that the salts of the compounds of each of formulas (I), (II) and (III) can be  
crystalline monohydrates. The crystalline monohydrate of the R-enantiomeric form (structural  
formula (II)) of sitagliptin DHP salt is the form of the medicine used in JANUVIA®.  
[72] The 400 Patent teaches that the DHP salt of structural formulas (I) (III) in its crystalline  
monohydrate form can act as an active pharmaceutical ingredient and exhibits pharmaceutic  
Page: 25  
advantages and enhanced chemical and physical stability over the free base and hydrochloride  
salt previously disclosed in WO498, in the preparation of a pharmaceutical drug product  
containing the pharmacologically active ingredient.  
[73] Page 6 of the 400 Patent teaches how pharmaceutical compositions of the invention may  
be administered to patients. The 400 Patent notes that the dosage regimen is to be selected  
considering the “type, species, age, weight, sex and medical condition of the patient; the severity  
of the condition to be treated; the route of administration; and the renal and hepatic function of  
the patient” (page 6, lines 3-5). It notes that the “skilled physician, veterinarian, or clinician can  
readily determine and prescribe the effective amount of the drug required to prevent, counter or  
arrest the progress of the condition” (page 6, lines 5-7). The 400 Patent goes on to provide  
general guidance as to the various dosage ranges for tablet and intravenous [IV] administration,  
noting that intranasal and transdermal administration is also possible (page 6, lines 8-22).  
[74] It describes dosage forms of the compositions and provides examples, at pages 18 and 19,  
of the DHP salt of sitagliptin monohydrate formulated as a tablet by direct compression and  
roller compaction and as an IV formulation. The 400 Patent notes that the DHP salt of sitagliptin  
monohydrate of structural formula (I) has high solubility in water (72 mg/mL) making it  
especially amendable to the preparation of formulations.  
[75] The 400 Patent teaches that the DHP salt exhibits potent DPP-4 inhibitory properties,  
useful for the prevention and treatment of type 2 diabetes, obesity and high blood pressure.  
Page: 26  
[76] The 400 Patent outlines general methods for crystallizing the monohydrate of the DHP  
salt of structural formula (I) and provides more detailed instructions for preparing the crystalline  
monohydrate of structural formula (II). It also includes structural characterization spectra  
(XRPD, NMR, TGA and DSC) for the crystalline monohydrate of structural formula (II).  
A.  
Is the 400 Patent a Selection Patent?  
[77] A selection patent is a patent devoted to the selection of a particular compound, or  
compounds, from a larger grouping of compounds previously disclosed in general terms and  
claimed in a pre-existing genus patent: Apotex Inc v Shire LLC, 2021 FCA 52 [Shire] at para 31.  
[78] As set out in Apotex v Sanofi, 2008 SCC 61 [Sanofi] at paragraph 10, three conditions  
must be satisfied for there to be a selection patent:  
1.  
There must be a substantial advantage to be secured or  
disadvantage to be avoided by the use of the selected members.  
2.  
The whole of the selected members (subject to “a few  
exceptions here and there”) possess the advantage in question.  
3.  
The selection must be in respect of a quality of a special  
character peculiar to the selected group. If further research  
revealed a small number of unselected compounds possessing the  
same advantage, that would not invalidate the selection patent.  
However, if research showed that a larger number of unselected  
compounds possessed the same advantage, the quality of the  
compound claimed in the selection patent would not be of a special  
character.  
[79] Where the patent is a selection patent, the asserted advantage or nature of the  
characteristic possessed by the selected group must be stated in the specification in clear terms:  
Eli Lilly Canada Inc v Novopharm Limited, 2010 FCA 197 [Eli Lilly] at para 78; Sanofi at  
Page: 27  
para 114. Such disclosure serves to define the characteristic features of the inventive compounds  
that purport to distinguish them over other compounds in the genus.  
[80] The classification of a patent as a selection patent serves to assist the Court in  
understanding “the nature of the beast” it is dealing with (Shire at para 33; Eli Lilly at para 28)  
for the purpose of the Court’s analysis of validity. The classification contextualizes the patent  
and makes it easier to compare the facts of the particular case before the court with other  
previous fact scenarios: Shire at para 33; Eli Lilly at paras 27-28. However, the validity analysis  
and the requirements for a valid patent stay the same, whether the patent is a selection patent or  
not: Shire at para 34; Eli Lilly at paras 33-34. The finding that the characteristics of a selection  
patent have or have not been met does not constitute an independent basis upon which to attack  
the validity of the patent: Shire at para 32; Eli Lilly at paras 27-28, 33, 48.  
[81] PMS raises a preliminary objection to the characterization of the 400 Patent as a selection  
patent. It asserts that Merck is prohibited from raising this characterization because it was not  
expressly in Merck’s pleadings. I do not find this argument persuasive.  
[82] PMS raised the issue of selection patents in its Statement of Defence, where it pleaded  
that if the Plaintiffs assert that the 400 Patent is a selection patent, such framework does not  
“save the 400 Patent.” Merck traversed this allegation in its Reply. It is clear that PMS has not  
been “caught by surprise” by any assertion that the 400 Patent is a selection patent. In any event,  
there has been no claim that the 400 Patent is savedby recourse to the law of selection patents.  
As acknowledged by Merck, the same rules of validity still apply. Both parties assert that the  
Page: 28  
obviousness analysis does not turn on whether the 400 Patent is characterized as a selection  
patent. Nonetheless, the Court must determine the “nature of the beast” in order to provide  
context for its validity analysis.  
[83] In this case, the 400 Patent refers to the compound 4-oxo-4-[3-(trifuoromethyl)-5,6-  
dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine, now  
know as sitagliptin, as being disclosed within the genus of compounds in WO498, and as to its  
pharmaceutically acceptable salts being generically encompassed within the scope of WO498,  
without specific disclosure of the DHP salt of sitagliptin (structural formula I). As stated in the  
Background to the Invention, at page 1:  
WO 03/004498 (published 16 January 2003), assigned to Merck &  
Co, describes a class of beta-amino tetrahydrotriazolo[4,3-  
a]pyrazines, which are potent inhibitors of DP-IV and therefore  
useful for the treatment of Type 2 diabetes. Specifically disclosed  
in WO 03/004498 is 4-oxo-4-[3-(trifuoromethyl)-5,6-  
dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-  
trifluorophenyl)butan-2-amine. Pharmaceutically acceptable salts  
of this compound are generically encompassed within the scope of  
WO 03/004498.  
However, there is no specific disclosure in the above reference of  
the newly discovered monobasic dihydrogenphosphate salt of 4-  
oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-  
a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)butan-2-amine of  
structural formula I below.  
[84] WO498 exemplifies the compound now known as sitagliptin as one of 33 examples  
specifically disclosed within the application. It discloses a process for making sitagliptin and its  
hydrochloride salt and claims the compound, together with the 33 compounds exemplified and  
their pharmaceutically acceptable salts, in a separate claim of the application.  
Page: 29  
[85] WO498 refers to phosphoric acid as being one of the eight particularly preferred  
pharmaceutically acceptable non-toxic acids that may be used to prepare a salt with the basic  
compounds of WO498, which would include sitagliptin (page 10, lines 14-25).  
[86] Similarly, WO498 refers to the salts prepared from the genus of compounds as being in  
the solid form and states that they may exist in more than one crystal structureand may be in  
the form of hydrates(page 9, lines 32-34).  
[87] It is clear that the DHP salt of sitagliptin and the monohydrate are generically  
encompassed within WO498, but not specifically exemplified or claimed. Indeed, the 400 Patent  
refers to the DHP salt and crystalline monohydrate as being “newly discovered” and novel.  
[88] The 400 Patent asserts that the crystalline DHP salt of sitagliptin has pharmaceutical  
advantages over the sitagliptin free base and hydrochloride salt in WO498; in particular,  
enhanced chemical and physical stability, which provide advantageous properties in preparing  
solid pharmaceutical dosage forms. At stated at page 4, lines 26-34 of the 400 Patent:  
The crystalline dihydrogenphosphate salt of the present invention  
exhibits pharmaceutic advantages over the free base and the  
previously disclosed hydrochloride salt (WO 03/004498) in the  
preparation of a pharmaceutical drug product containing the  
pharmacologically active ingredient. In particular, the enhanced  
chemical and physical stability of the crystalline  
dihydrogenphosphate salt monohydrate constitute advantageous  
properties in the preparation of solid pharmaceutical dosage forms  
containing the pharmacologically active ingredient.  
The dihydrogenphosphate salt of the present invention, which  
exhibits potent DP-IV inhibitory properties, is particularly useful  
for the prevention or treatment of Type 2 diabetes, obesity, and  
high blood pressure.  
Page: 30  
[89] As explained by Dr. Wuest, enhanced chemical stability would be understood by the PSA  
to mean that there is reduced chemical degradation/decomposition when sitagliptin is prepared  
and formulated into a medicine using the crystalline monohydrate DHP salt; thus, ensuring that  
its therapeutic effect is beneficially maintained. Enhanced physical stability means that the  
crystalline monohydrate DHP salt does not readily convert to other physical forms that might  
have unknown or undesirable properties. The physical stability is also shown in the TGA and  
DSC analyses at Figures 4 and 5, which demonstrate the high thermal stability of the crystalline  
monohydrate (Wuest Report, Ex 29, paras 22, 51-53).  
[90] The 400 Patent, at page 7, lines 10-11, also states that the crystalline monohydrate has  
“high solubility in water”, with a solubility of about 72 mg/mL. I accept Dr. Daviesexplanation  
that this reference refers to the solubility classification under the Biopharmaceutics Classification  
System [BCS] and would be understood to be indicating the solubility in light of intended dose.  
Under the BCS, a “highly soluble” drug is one where the highest dose is soluble in 250 mL of  
dissolution medium. The high solubility of the monohydrate indicates that the monohydrate is  
especially suitable for formulation without the need for dissolution enhancing techniques (Davies  
Report, Ex 42, paras 44-46, 48).  
[91] The only comparison made in the 400 Patent is between the DHP salt of sitagliptin  
crystalline monohydrate and the sitagliptin free base and hydrochloride salt.  
[92] The 400 Patent is not devoted, as described in Shire, to the selection of sitagliptin over  
the other compounds of WO498. Nonetheless, the PSA would understand that a selection of  
Page: 31  
sitagliptin has taken place. Dr. Wuest explained this further on cross-examination as follows (TT  
V6, P:497 L:12-P:498 L:21):  
Q.  
Okay. Let’s go to the section of the patent that’s  
entitled “Summary of the Invention,” which is on the next page.  
Under the heading “The Summary of the Invention”, it states:  
“The present invention is concerned with a novel  
dihydrogen phosphate salt of the DP-IV inhibitor  
sitagliptin and crystal hydrates thereof, in particular  
a crystalline monohydrate.”  
You’ll agree with me, Dr. Wuest, there’s nothing here  
telling the reader that the invention is about discovering sitagliptin  
or sitagliptin’s ability to inhibit DP-IV.  
A.  
It would be clear from reading this particular  
section by someone of with [sic] skill in this art that this particular  
compound and its salts and the crystalline forms thereof have been  
selected through a process. So there is a step that’s been taken  
from the prior art to the new art in the 400 patent; namely, that  
there is now been placed a focus on sitagliptin and its salts.  
Q.  
It doesn’t say that, though, does it? Does it say  
anything here about selecting sitagliptin from the prior art? It  
doesn’t say that here. It talks about a novel salt form and a novel  
hydrate form.  
A.  
I’m not sure I understand how you can maintain  
that. I’m looking at this from the perspective of the skilled person  
who has the 400 patent in front of them and knowledge of the prior  
art. That knowledge would include the knowledge that sitagliptin  
and its hydrochloride salt [are] in the 498 application.  
And so the issue that -- is how you would get from that to  
where of this summary -- this situation that is described in this  
summary. So there’s clearly a selection of that particular  
compound because this describes a new salt of that particular  
compound.  
Q.  
When you say “of that particular compound,” you  
meant sitagliptin?  
A.  
That’s right.  
Page: 32  
[93] The 400 Patent gives no reason for honing in on sitagliptin over the other compounds  
disclosed within WO498. However, it relies on this choice for the further development work  
disclosed in the patent. As acknowledged by Dr. Hollingsworth, the PSA knew from the 400  
Patent that Merck had selected sitagliptin as its lead compound for further development, and had  
successfully made the DHP salt and identified the crystalline monohydrate as being amenable to  
sitagliptin formulations (TT V3, P:281 L:4-28). The PSA knew that the solubility, and relative  
stability of the DHP salt of sitagliptin crystalline monohydrate had been determined and had  
been selected over sitagliptin free base and the hydrochloride salt (TT V3, P:281 L:10-15; P:282  
L:3-8).  
[94] This is no different than Sanofi where the genus patent exemplified the racemate of the  
compound, but did not specifically disclose the dextro-rotatory isomer of the racemate, or the  
advantages of using the bisulfate salt in combination with the dextro-rotatory isomer, which were  
the subject matter of the later selection patent.  
[95] There is no explanation as to why sitagliptin was chosen for further development.  
However, the fact that there has been a selection of a particular salt and crystalline form of a  
particular compound from the genus of compounds, salts and crystalline forms encompassed  
within WO498, and that the particular salt and crystalline form are said to have advantages over  
sitagliptin free base and its hydrochloride salt, which are disclosed in WO498, in my view  
favours the 400 Patent being considered a selection patent. Whether the proposed invention of  
the 400 Patent is inventive over WO498 and whether the disclosure of the 400 Patent is sufficient  
is a matter to be dealt with separately below.  
Page: 33  
B.  
Claims Construction  
[96] The principles of claim construction were summarized by the Federal Court of Appeal  
[FCA] in Tearlab Corporation v I-Med Pharma Inc., 2019 FCA 179 at paragraphs 30 to 34:  
[30] The general principles of claim construction are now well  
established and were set out by the Supreme Court in three cases  
(Whirlpool at paras. 49-55; Free World Trust v. Électro Santé Inc.,  
2000 SCC 66, [2000] 2 S.C.R. 1024 at paras. 31-67 [Free  
World Trust]; Consolboard Inc. v. MacMillan Bloedel (Sask.) Ltd.,  
1981 CanLII 15 (SCC), [1981] 1 S.C.R. 504 at p. 520  
[Consolboard]). These principles can be summarized as follows.  
[31] The Patent Act promotes adherence to the language of the  
claims, which in turn promotes fairness and predictability (Free  
World Trust at paras. 31(a), (b) and 41). The words of the claims  
must, however, be read in an informed and purposive way (at para.  
31(c)), with a mind willing to understand (at para. 44). On a  
purposive construction, it will be apparent that some elements of  
the claimed invention are essential while others are non-essential  
(at para. 31(e)). The interpretative task of the court, in claim  
construction, is to separate and distinguish between the essential  
and the non-essential elements, and to give the legal protection to  
which the holder of a valid patent is entitled only to the essential  
elements (at para. 15).  
[32] To identify these elements, the claim language must be read  
through the eyes of a POSITA, in light of the latter’s common  
general knowledge (Free World Trust at paras. 44-45; see  
also Frac Shack at para. 60; Whirlpool at para. 53). As noted  
in Free World Trust:  
[51] …The words chosen by the inventor will be  
read in the sense the inventor is presumed to have  
intended, and in a way that is sympathetic to  
accomplishment of the inventor’s purpose  
expressed or implicit in the text of the claims.  
However, if the inventor has misspoken or  
otherwise created an unnecessary or troublesome  
limitation in the claims, it is a self-inflicted wound.  
The public is entitled to rely on the words  
used provided the words used are interpreted fairly  
and knowledgeably. [Emphasis in the original.]  
Page: 34  
[33] Claim construction requires that the disclosure and the  
claims be looked at as a whole “to ascertain the nature of the  
invention and methods of its performance, … being neither  
benevolent nor harsh, but rather seeking a construction which is  
reasonable and fair to both patentee and public” (Consolboard at p.  
520; see also Teva Canada Ltd. v. Pfizer Canada Inc., 2012 SCC  
60, [2012] 3 S.C.R. 625 at para. 50). Consideration can thus be  
given to the patent specifications to understand what was meant by  
the words in the claims. One must be wary, however, not to use  
these so as “to enlarge or contract the scope of the claim as written  
and … understood” (Whirlpool at para. 52; see also Free World  
Trust at para. 32). The Supreme Court recently emphasized that the  
focus of the validity analysis will be on the claims; specifications  
will be relevant where there is ambiguity in the claims  
(AstraZeneca Canada Inc. v. Apotex Inc., 2017 SCC 36, [2017] 1  
S.C.R. 943 at para. 31; see also Ciba at paras. 74-75).  
[34] Finally, it is important to stress that claim construction  
must be the same for the purpose of validity and for the purpose of  
infringement (Whirlpool at para. 49(b)).  
[97] The 400 Patent is to be construed from the viewpoint of the PSA to which it pertains as of  
its publication date, January 13, 2005.  
(1)  
PSA of the 400 Patent  
[98] The PSA is the hypothetical person to whom the patent is addressed. This may be a single  
individual or a team of individuals representing different disciplines, depending on the nature of  
the invention. The PSA is deemed to be unimaginative and uninventive, but at the same time is  
understood to have an ordinary level of competence and knowledge incidental to the field to  
which the patent relates and to be reasonably diligent in keeping up with advances: Merck & Co  
v Pharmascience Inc, 2010 FC 510 [Merck] at para 35-36, 39; Teva Canada Limited v Janssen  
Inc, 2018 FC 754, at paras 65-66, aff’d 2019 FCA 273.  
Page: 35  
[99] While the experts agreed that the PSA is a team of individuals, PMS’ experts assert that  
the team is limited to those that would be involved in the steps of pharmaceutical development  
that bridge the gap between the active pharmaceutical ingredient [API] and finished dosage  
form; that is, an analytical chemist, process chemist and formulator. Merck’s experts do not  
disagree that the team comprising the PSA would include a chemist, or chemists, with  
knowledge of analytical techniques and processing, but also assert that the PSA would include a  
medicinal chemist and a medical doctor as the invention involves the selection of sitagliptin and  
its use as a DPP-4 inhibitor.  
[100] As set out above, I agree that the 400 Patent requires that a selection of sitagliptin has  
taken place. However, that does not mean that it must follow that the patent is directed to a  
medicinal chemist. The determination of the PSA involves consideration as to who would have  
an interest in the teachings of the patent.  
[101] The 400 Patent does not disclose the type of studies or data that would be  
characteristically of interest to the medicinal chemist, such as SAR studies or IC50 values. The  
400 Patent does not describe the process involved in selecting sitagliptin over the other  
compounds of WO498, including over the free base and hydrochloride salt exemplified within  
WO498. Rather, it is directed to the identification of the DHP salt of sitagliptin and its crystalline  
monohydrate with its purported advantageous properties. While I would agree that someone on  
the skilled team would need to have a general understanding as to how to get from WO498 to the  
teachings of the 400 Patent, in my view this does not require that the team of individuals that  
comprise the PSA include a separate medicinal chemist. Rather, it would be sufficient for one of  
Page: 36  
the members of the team to have some general background knowledge of medicinal chemistry  
and/or lead compound identification. Indeed, I note that even PMS considered it important to  
have an expert who could speak to lead compound identification as part of its case i.e.,  
Dr. Foley.  
[102] In my view, the team of individuals that comprises the PSA would also include a  
clinician or someone with knowledge of the treatment of type 2 diabetes. Both the Field of the  
Invention and the Summary of the Invention refer to the use of the DHP salt of sitagliptin  
crystalline monohydrate for the treatment and prevention of type 2 diabetes and other diseases  
and conditions for which an inhibitor of DPP-4 is indicated. It also refers to the use of the DHP  
salt of sitagliptin crystalline monohydrate in pharmaceutical compositions to treat patients with  
these conditions as being part of the invention. Indeed, Claims 22 and 26 are directed to such  
uses.  
[103] Page 6, lines 5-7 of the 400 Patent states that an ordinarily skilled physician,  
veterinarian, or clinician can readily determine and prescribe the effective amount of the drug  
required to prevent, counter or arrest the progress of the condition”. Drs. Elitzin and Foley state  
that this passage makes clear that a different skilled person was intended to deal with the dosing  
regimen for the drug than the skilled person to whom the patent is directed. However, I prefer the  
evidence of Merck’s experts on this passage.  
[104] As set out in Merck, a patent may be directed to different persons, each having a different  
interest (Merck at para 39).  
Page: 37  
[105] I accept the evidence of Dr. Lewanczuk that page 6 is indicating that this part of the  
patent’s teachings - i.e., dosing regimen and therapeutic use - is directed to the skilled clinician  
as opposed to other members of the team that comprise the PSA (Lewanczuk Report, Ex 55,  
paras 104-109).  
[106] Notably, despite his arguments that a skilled clinician would not be included as a member  
of the PSA, Dr. Foley testified to the importance of the clinician in evaluating aspects of the  
patent. As acknowledged by Dr. Foley, it is the clinician who would be keeping up with the  
literature and patent filings pertaining to DPP-4 inhibitors, and it is the clinician who would have  
appreciated whether there was any therapeutic advantage being described in the 400 Patent  
relating to the monohydrate or DHP salt of sitagliptin over what had been described in WO498  
(TT V1, P:53 L:20-P:54 L:8).  
[107] Indeed, each of Drs. Foley and Lewanczuk provided useful insight as to the skilled  
clinician’s understanding of those portions of the 400 Patent dealing with the use of the  
monohydrate. Dr. Foley was asked to speak to claims 22 and 26 of the 400 Patent and to the  
prior art landscape involving clinical studies using DPP-4 inhibitors. PMS relies heavily on  
Dr. Foley’s testimony relating to his understanding and interpretation of these claims.  
[108] When asked about this in oral argument, PMS asserted that Dr. Foley’s evidence was  
only intended to provide background on the invention story. However, this response runs  
contrary to the mandate set out in the Foley Report and to his opinions, which speak directly to  
the obviousness analysis.  
Page: 38  
[109] In my view, the PSA would include someone with clinical knowledge of the treatment of  
patients with type 2 diabetes, who could be a medical doctor and/or someone who has acquired  
this knowledge through experience on a clinical team.  
[110] Accordingly, I find that the PSA would include a chemist with experience in compound  
characterization and processing, and some general background knowledge of medicinal  
chemistry and/or lead compound identification. This could be one individual with this skill-set or  
separate analytical and process chemists. The team would also include a formulator, and a  
clinician or individual with clinical knowledge of the treatment of patients with type 2 diabetes.  
[111] While the experts were not entirely at idem as to the experience of the members of the  
team comprising the PSA, they appeared to consistently agree that the members of the team  
could have a Bachelor’s, Master’s or Ph.D., depending on the years of supplemental experience.  
The number of years needed would be greater for someone with a Master’s degree and greater  
still for someone with a Bachelor’s degree. All experts agreed that at least one year of experience  
would be required for a member of the team, even if holding a Ph.D.  
(2)  
Construction of the Asserted Claims of the 400 Patent  
[112] The 400 Patent includes 27 claims, nine of which are in issue for this action: claims 4-7,  
19, 20, 22, 24 and 26. The parties are in general agreement as to the construction to be given to  
these claims.  
Page: 39  
[113] Claims 4-7, 19, 20, 22, 24 and 26 of the 400 Patent read as follows:  
4.  
The salt of Claim 2 characterized in being a crystalline  
monohydrate.  
5.  
The salt of Claim 4 characterized by characteristic  
absorption bands obtained from the X-ray powder diffraction  
pattern at spectral d-spacings of 7.42, 5.48, 3.96 angstroms.  
6.  
The salt of Claim 5 further characterized by characteristic  
absorption bands obtained from the X-ray powder diffraction  
pattern at spectral d-spacings of 6.30, 4.75, and 4.48 angstroms.  
7.  
The salt of Claim 6 further characterized by characteristic  
absorption bands obtained from the X-ray powder diffraction  
pattern at spectral d-spacings of 5.85, 5.21 and 3.52 angstroms.  
19.  
A process for preparing the salt of Claim 1 comprising the  
step of contacting one equivalent of 4-oxo-4-[3-(trifluoromethyl)-  
5,6-didydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-  
trifluorophenyl)butan-2-amine in an organic solvent or aqueous  
organic solvent with about a one equivalent of phosphoric acid at a  
temperature in the range of about 25-100oC.  
20.  
The process of Claim 19 wherein said organic solvent is a  
C1-C5 linear or branched alkanol.  
22.  
Use of the salt of Claim 4 as active ingredient in the  
manufacture of a medicament for use in the treatment of type 2  
diabetes.  
24.  
The process for preparing the crystalline monohydrate of  
Claim 4 comprising the steps of:  
(a)  
crystallizing said dihydrogenphosphate salt of Claim 1 at  
25oC from a mixture of isopropanol and water, such that the water  
concentration is above 6.8 weight percent;  
(b)  
(c)  
26.  
recovering the resultant solid phase; and  
removing the solvent therefrom.  
A use of a therapeutically effective amount of the salt  
according to Claim 4 for the treatment of type 2 diabetes in a  
patient in need of such treatment.  
Page: 40  
[114] Claim 4 is a dependent claim, which stems from Claim 2 of the 400 Patent, which itself  
depends from Claim 1.  
[115] Claim 1 is directed to the DHP salt of sitagliptin and its hydrate, without any specific  
stereochemistry:  
1.  
A dihydrogenphosphate salt of 4-oxo-4-[3-  
(trifluoromethyl)-5,6-didydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-  
yl]-1-(2,4,5-trifluorophenyl)butan-2-amine of structural formula 1:  
or a pharmaceutically acceptable hydrate thereof.  
[116] Claim 2 is directed to the R-enantiomer of the DHP salt of sitagliptin and its hydrate:  
2.  
The salt of Claim 1 of structural formula II having the (R)-  
configuration at the chiral center marked with an *  
[117] It is understood from these dependencies that Claim 4 (and all claims that depend from  
claim 4) claim the R-enantiomer of the DHP salt of sitagliptin in its crystalline monohydrate  
form.  
Page: 41  
[118] Claims 5-7 include characterization data arising from the XRPD spectra for the  
crystalline monohydrate form. The PSA would know that the d-spacings arise from the formulaic  
conversion of the 2θ values of the crystalline form as obtained through calculation using Bragg’s  
law: nλ=2dsinθ (Hollingsworth Report, Ex 68, para 143).  
[119] Claims 19 and 20 set out general methods for preparing the non-stereospecific DHP salt  
of sitagliptin monohydrate. Through the process description, it is understood that about one  
molar equivalent of phosphoric acid should be reacted with about one molar equivalent of free  
base. Claim 20 specifies that the organic solvent is a C1-C5 linear or branched alkanol.  
[120] Claim 24 provides a process for making the R-enantiomer of the DHP salt of sitagliptin in  
its crystalline monohydrate form. The PSA would understand that this process does not specify  
its starting materials (TT V3, Conf, P:58 L:15-P:59: L:6), but only requires that crystallization  
occur from the DHP salt at a temperature of 25oC using a mixture of isopropanol and water, such  
that the water concentration is above 6.8 weight percent. The process also requires that the  
crystals be recovered and the solvent removed. The process does not specify the process for  
solvent removal (TT V3, P:309 L:8-17).  
[121] The PSA would understand from the teachings of the 400 Patent that the crystalline  
monohydrate is vulnerable to conversion to its dehydrated (anhydrous) form if heated to above  
40oC under very dry nitrogen flow and that it will convert back from the anhydrous form to the  
monohydrate under ambient conditions (page 18, lines 5-8 of the 400 Patent) (TT V2, P:223  
Page: 42  
L:17-21; TT V2, Conf, P:41 L:2-7; TT V3, P:311 L:16-24; TT V6, P:523 L:4-13). The skilled  
person would understand that ambient conditions would be room temperature.  
[122] Claims 22 and 26 are directed to the therapeutic use of the DHP salt of sitagliptin  
crystalline monohydrate. Claim 22 claims the use of the DHP salt of sitagliptin crystalline  
monohydrate as the active ingredient in the manufacture of a medicament to treat type 2 diabetes.  
Claim 26 claims the use of a therapeutically effective amount of the DHP salt of sitagliptin  
crystalline monohydrate for treating a patient with type 2 diabetes. No specific dose is claimed.  
As explained by Dr. Lewanczuk, the PSA would understand a “therapeutically effective amount”  
to mean an amount of the claimed compound that effectively contributes to improving the  
patient’s glycemic control by lowering blood glucose levels (Lewanczuk, Ex 55, para 111).  
V.  
A.  
Obviousness  
Legal Principles  
[123] Section 28.3 of the Patent Act provides that the subject matter of a claim in an application  
for a patent in Canada must be subject matter that would not have been obvious on the claim date  
(here, June 24, 2003) to the PSA, having regard to information that was made available to the  
public: (a) more than one year before the filing day by the applicant, or by a person who obtained  
knowledge directly or indirectly from the applicant; and, (b) before the claim date, by a person  
not mentioned in (a).  
[124] Obviousness is a difficult test to satisfy because it necessitates showing that the PSA  
would have come directly and without difficulty to the invention, without the benefit of  
Page: 43  
hindsight: Bridgeview Manufacturing Inc v 931409 Alberta Ltd (cob Central Alberta Hay  
Centre), 2010 FCA 188 at para 50.  
[125] The Supreme Court of Canada in Sanofi set out a four-step approach to the obviousness  
analysis at paragraph 67 of its decision, as follows:  
(1)  
(a)  
(b)  
Identify the notional “person skilled in the art”;  
Identify the relevant common general knowledge of  
that person;  
(2)  
(3)  
Identify the inventive concept of the claim in question or if  
that cannot readily be done, construe it;  
Identify what, if any, differences exist between the matter  
cited as forming part of the “state of the art” and the  
inventive concept of the claim or the claim as construed;  
(4)  
Viewed without any knowledge of the alleged invention as  
claimed, do those differences constitute steps which would  
have been obvious to the person skilled in the art or do they  
require any degree of invention?  
[126] In areas of endeavour where advances are often won by experimentation, an “obvious to  
try” analysis may be appropriate to take into consideration at the fourth step of the obviousness  
inquiry. The critical question is whether it “was more or less self-evident to try to obtain the  
inventionhaving regard to the following factors, while noting that [m]ere possibility that  
something might turn up is not enough(Sanofi at paras 66, 68-69):  
1.  
Is it more or less self-evident that what is being tried ought  
to work? Are there a finite number of identified predictable  
solutions known to persons skilled in the art?  
2.  
What is the extent, nature and amount of effort required to  
achieve the invention? Are routine trials carried out or is  
the experimentation prolonged and arduous, such that the  
trials would not be considered routine?  
Page: 44  
3.  
Is there a motive provided in the prior art to find the  
solution the patent addresses?  
[127] The Court must be cautious, however, when approaching the obvious to try analysis as it  
remains as only one factor amongst many that may assist in the obviousness inquiry: Bristol  
Myers Squibb Canada Co v Teva Canada Limited, 2017 FCA 76 [Atazanavir] at para 38; Sanofi  
at para 64. It is not intended to displace other tests. As the Supreme Court in Sanofi made clear,  
the Court favours “an expansive and flexible approach that would include ‘any secondary  
considerations that [will] prove instructive’”: Sanofi at para 63; Atazanavir at para 61.  
B.  
Common General Knowledge [CGK] and Prior Art  
[128] The reference for the test for obviousness is the PSA. After identifying the credentials  
and characteristics of the PSA (as done earlier in these reasons), the next step is to identify the  
CGK of the PSA. CGK means knowledge generally known by the PSA at the relevant time  
(Sanofi at para 37), in this case June 24, 2003.  
[129] CGK is to be distinguished from the prior art, which is a broad category encompassing all  
previously disclosed information in the field. CGK includes knowledge of patents, but does not  
include knowledge of all patents; nor does it include knowledge of all journal articles or other  
technical information. It is the subset of patents, journal articles and technical information of  
which the PSA has become generally aware and which has been accepted: Eurocopter v Bell  
Helicopter Textron Canada Ltée, 2013 FCA 219 [Eurocopter] at paras 64-65; Mylan  
Pharmaceuticals ULC v Eli Lilly Canada Inc., 2016 FCA 119 at para 24.  
Page: 45  
[130] The parties differ on their positions as to what constitutes the CGK of the PSA and  
whether this would include general information pertaining to DPP-4 inhibitors and the treatment  
of type 2 diabetes in addition to CGK relating to salt formation and crystal form identification.  
As I have already determined that the PSA would include someone with clinical knowledge, it is  
my view that CGK relating to DPP-4 inhibition and treatment of type 2 diabetes would be known  
to this PSA (TT V1, P:55 L:11-27). Indeed, the 400 Patent references this information as part of  
the relevant background to the invention.  
(1)  
DPP-4 Inhibition and Treatment of Type 2 Diabetes  
[131] By 1997, type 2 diabetes was recognized as a serious disease condition that required  
medical attention to avoid long-term health risks. GLP-1 and its role in stimulating secretion of  
insulin had been identified. It was known that DPP-4 acted to degrade GLP-1 and that inhibiting  
DPP-4 could have effects on modulating insulin and glucose levels in the blood.  
[132] The 400 Patent acknowledges certain information known to the PSA as of June 24, 2003  
regarding the inhibition of DPP-4 as an approach to treat type 2 diabetes. As stated at page 1 of  
the 400 Patent:  
Inhibition of dipeptidyl peptidase-IV (DP-IV), an enzyme that  
inactivates both glucose-dependent insulinotropic peptide (GIP)  
and glucagon-like peptide 1 (GLP-1), represents a novel approach  
to the treatment and prevention of Type 2 diabetes, also known as  
non-insulin dependent diabetes mellitus (NIDDM). The therapeutic  
potential of DP-IV inhibitors for the treatment of Type 2 diabetes  
has been reviewed: C.F. Deacon and J.J. Holst, “Didpeptidyl  
peptidase IV inhibition as an approach to the treatment and  
prevention of Type 2 diabetes: a historical perspective,” Biochem,  
Biophys. Res. Commun., 294: 1-4 (2000); K. Augustyns, et al.,  
“Didpeptidyl peptidase IV inhibitors as new therapeutic agents for  
the treatment of Type 2 diabetes,” Expert, Opin. Ther. Patents, 13:  
Page: 46  
499-510 (2003); and D.J. Drucker, “Therapeutic potential of  
dipeptidyl peptidase IV inhibitors for the treatment of Type 2  
diabetes,” Expert Opin. Investig. Drugs, 12: 87-100 (2003).  
[133] By admission of the patentee, through inclusion of these references in the background to  
the 400 Patent, the Deacon, Augustyns and Drucker papers form part of the relevant prior art:  
Shire Biochem Inc v Canada (Minister of Health) 2008 FC 538 at para 25; Eli Lilly Canada Inc v  
Novopharm Ltd, 2007 FC 596 at para 142; Pfizer Canada Inc v Novopharm Ltd, 2005 FC 1299  
at para 78. These papers summarize the developments known in the field regarding compounds  
that had already shown DPP-4 inhibitory activity, including Probiodrug’s compound P32/98 and  
the Novartis compounds, DPP-728 and LAF-237.  
[134] As noted by Drs. Foley and Lewanczuk, P32/98 (depicted at paragraph 206 below) had  
already been tested for potency in animal studies (Foley Report, Ex 1, Schedule E19) and was  
reported to enhance the insulin response and improve glucose tolerance in diabetic humans  
administered with a 60 mg single dose (Lewanczuk, Ex 55, para 102 and Appendix K).  
[135] It was also known that DPP-728 (depicted at paragraph 206 below) had shown activity in  
animal studies and some clinical efficacy in a 4-week Phase II study in humans (Foley Report,  
Ex 1, paras 30 and 54 and Schedule E19; TT V1, P:55 L:11-27). The results of a study reported  
by Ahrén in 2002, showed the safety and tolerability of DPP-728, with only minimal adverse  
events. The study reported lower glucose levels in human patients without hypoglycemia when  
administered in 100 mg and 150 mg doses and identified inhibition by DPP-728 as a feasible  
treatment for type 2 diabetes (Foley Report, Ex 1, para 54(f) and Schedule E11; Lewanczuk, Ex  
55, para 102).  
Page: 47  
[136] Kinetic studies showed that DPP-728 did not function as a simple competitive inhibitor,  
but as a substrate for the DPP-4 catalytic site. A derivative of DPP-728 (LAF-237, depicted at  
paragraph 206 below), eventually known as vildagliptin, was developed by Novartis to improve  
on the compound’s kinetics and dissociation rate (Foley Report, Ex 1, Schedule E19).  
[137] In 2003, Villhauer reported on the in vivo efficacy of vildagliptin in rat models (Foley  
Report, Ex 1, Schedule E17). Other in vivo work in monkeys also indicated that vildagliptin had  
a longer half-life in inhibiting DPP-4 than DPP-728, and might be suitable for a once-a-day  
treatment (Foley Report, Ex 1, para 54(g)).  
[138] As acknowledged by the 400 Patent, the PSA also would have known about WO498 and  
about the class of compounds disclosed in WO498 as being putative inhibitors of DPP-4, with  
the potential to be used in the treatment or prevention of diseases where DPP-4 is involved, such  
as type 2 diabetes (Lewanczuk, Ex 55, at paras 115, 117, 121, 122). Dr. Foley testified that this  
was the only document published by June 24, 2003 that included the compound now known as  
sitagliptin (TT V1, P:61 L:17-23). It did not include any specific activity or efficacy data for any  
of its compounds. As of June 2003 no results of any clinical evaluation from Merck had been  
published on any of the compounds from WO498 (TT V1, P:56 L:17-27).  
(2)  
Salt Formation and Selection  
[139] The PSA of the 400 Patent would also possess certain CGK relating to salt formation and  
selection.  
Page: 48  
[140] It was undisputed by the experts that by June 24, 2003 standard high throughput  
techniques for salt screening were known and used in the industry and allowed for numerous salt  
forms to be screened at one time. The experts agreed that salt formation was expected to improve  
the possibility of forming stable crystalline solids. However, they did not agree as to how salt  
screening would be approached.  
[141] Dr. Wuest’s view was that salt screening was an essential but iterative process. Citing  
Gould and Stahl 2002 (which were also attached to Dr. Elitzin’s report) and the 1996 chapter on  
“Salt Forms of Drugs and Absorption” in the Encyclopedia of Pharmaceutical Technology,  
authored by Bighley, Berke and Monkhouse, Dr. Wuest stated that the first course of action for  
drug development was to consider the free acid or free base form of the active compound. Only  
if the free acid or free base was unacceptable for development would salt formation be necessary.  
The first salt to be considered for a basic compound would typically be the hydrochloride salt  
and only if that salt proved unacceptable would other mineral salts, such as phosphate, be  
considered. Stahl highlighted that phosphate salts had a tendency to form hydrates, which  
generally had lower solubility and slower dissolution rates than their corresponding anhydrous  
forms.  
[142] According to Dr. Elitzin, salt screening was a matter of routine by 2003 and took place at  
the outset of every drug development program. He did not agree that consideration of the free  
base would influence whether a salt screen was conducted, but referred in his report to initial  
physicochemical characterization of the free acid or base API that would be used for comparison  
purposes. His view was that hydrochloride salts would not necessarily be the first choice as it  
Page: 49  
was known that the solubility of hydrochloride salts could be impacted by the common ion effect  
in gastric acid medium.  
[143] Overall, I favour Dr. Wuest’s comments as they are supported by publications (and  
authors) that Dr. Elitzin himself recognized as being authoritative and are also reflective of the  
approach taken at Merck. The statistics referenced in Stahl 2002 indicated that by June 2003,  
50% of all drugs on the market were in salt form, while the other 50% remained as the free  
base/free acid. Of those basic drugs that were salts, more than half were hydrochloride salts.  
Phosphate salts were pharmaceutically acceptable inorganic salts that ranked in the top five  
preferred salts for basic drugs, although the number commercially made and sold by 2003 were  
significantly less than hydrochloride salts.  
[144] Both Dr. Wuest and Dr. Elitzin agreed with the statement made in Stahl 2002  
(Hollingsworth Report, Ex 68, Schedule 26) that the selection of a salt form that exhibits the  
desired pharmacological, toxicological and therapeutic properties was a multidisciplinary task of  
varying complexity.  
[145] Various analytical techniques were available for salt selection and involved  
characterization of structural, physicochemical, and physical properties, as well as analysis of  
impurities and stability studies.  
Page: 50  
(3)  
Crystal Form Identification  
[146] The parties’ experts generally agreed about the CGK regarding crystal form  
identification, which can be summarized in the following paragraphs.  
[147] By 2003, it was well-known that most pharmaceutical compounds demonstrated  
polymorphism. Crystals incorporating water (i.e. hydrates) were common and it was known that  
phosphate salts had a propensity to form hydrates.  
[148] As summarized in the paper Byrn 1994 (Hollingsworth Report, Ex 68, Schedule E21 at  
1148), which was accepted as being reflective of the CGK:  
The mission of those working in the field of solid-state  
pharmaceutical chemistry is to provide each drug in a solid form  
that has optimum performance in a given application. Pursuit of  
this mission requires recognition of several general, interrelated  
points: (1) Drugs can exist in a number of solid forms, each having  
different properties of pharmaceutical importance, including  
stability and bioavailability; the number and properties of these  
forms are largely unpredictable and vary considerably from case to  
case. (2) The forms of a drug may interconvert under various  
conditions. (3) Once a solid form is chosen for a product, methods  
for analysis and control of the form must be devised.  
[149] It was understood that the most thermodynamically stable form of a drug substance was  
typically preferred for pharmaceutical development and it was a routine part of the  
pre-formulation process to try to identify the most stable polymorphic form. By 1990, regulatory  
guidelines existed for ensuring that companies filing regulatory submissions had investigated  
polymorphism and identified what they considered to be the most stable crystalline form of their  
API.  
Page: 51  
[150] By 2003, a variety of routine methods were available and known to the PSA to conduct  
polymorph screening and to characterize the crystal forms obtained i.e., XRPD, NMR, TGA,  
DSC. A common strategy for screening included crystallization using a variety of solvents and  
solvent mixtures. As stated in Bernstein 2002 (Hollingsworth Report, Ex 68, Schedule E7 at  
page 252), another reference accepted as being reflective of the CGK:  
Our understanding of the role and choice of solvent has improved  
considerably and this information, combined with a knowledge of  
zones of stability can aid in determining crystallization conditions  
for obtaining metastable forms. In addition, there has also been  
considerable progress in understanding and utilizing the interaction  
of solvent with the growing crystal. Combining the detailed  
structural information available from the single crystal structure  
determinations of polymorphs with crystal morphological data (i.e.  
crystal habit, and the orientation of molecules projecting from the  
particular faces exposed) and with known intermolecular  
interactions between solute molecules and solvent functional  
groups allows the rational choice of solvent to select a particular  
polymorphic form. [citations omitted]  
[151] In addition to solvent choice, other factors identified in Byrn 1994 (Hollingsworth  
Report, Ex 68, Schedule E21 at 1150), were known to influence crystallization, including  
concentration or degree of supersaturation; temperature, including cooling rate and the cooling  
profile; additives; seeds; pH; and agitation.  
[152] Modelling programs existed for identifying plausible crystals forms; however, there was  
no ability to predict which forms could be isolated. As explained in Bernstein 2002  
(Hollingsworth Report, Ex 68, Schedule E7 at page 9):  
The possibility of polymorphism may exist for any particular  
compound, but the conditions required to prepare as yet unknown  
polymorphs are by no means obvious....we are almost totally  
ignorant about the properties to be expected from any new  
polymorphs that might be obtained.  
Page: 52  
[153] Similarly, Byrn 1994 (Hollingsworth Report, Ex 68, Schedule E21 at page 1148) stated  
the challenge faced by those in the field as follows:  
... the chief challenge in managing the phenomenon of multiple  
solid forms of drugs is our inability to predict how many forms can  
be expected in a given case: too often costly delays are  
encountered when a less soluble solid form suddenly appears late  
in a development program.  
[154] Further, it was known that different polymorphs could have markedly different  
formulation properties, including rate of dissolution. The skilled formulator on the PSA team  
was aware that a number of factors can influence the amount and rate at which a medicinal  
ingredient gets absorbed into the body, including the inherent properties of the medicinal  
ingredient, such as its solubility (Davies Report, Ex 42, para 29). The solubility of a drug  
increases with temperature and can vary with pH. Most available drugs are poorly soluble,  
which can translate to low bioavailability (the amount of drug absorbed into the bloodstream)  
(Davies Report, Ex 42, para 38-39 and Schedule 1).  
[155] The PSA knew from accepted references like Aulton 2002 and Stahl 2002 that hydrates  
are typically (but not always) less soluble than anhydrous forms and have slower dissolution  
rates (Davies Report, Ex 42, Schedule 1; Elitzin Report, Ex 66, Schedule E1). However, it was  
not possible to predict the properties of any polymorph, or which would have the most  
favourable properties for pharmaceutical development, in advance of discovering, making and  
testing it in appropriate assays (Davies, Ex 42, para 56-57).  
Page: 53  
C.  
What is the Starting Point of the Obviousness Analysis – “State of the Art”  
[156] The obviousness analysis asks whether the distance between two points in the  
development of the art can be bridged by the PSA using only their CGK: Atazanavir at para 65.  
The first of the two points is the state of the prior artat the relevant date: Atazanavir at  
para 65; Sanofi at para 67.  
[157] PMS asserts that the state of the prior art is defined by the 400 Patent and should be  
limited to the disclosure of sitagliptin and the hydrochloride salt of sitagliptin as a potent  
inhibitor of DPP-4 and to its usefulness to treat type 2 diabetes. It relies on Ciba Specialty  
Chemicals v SNF, 2017 FCA 225 [Ciba] at paragraph 60 as support for its assertion:  
To conclude, a word about "the matter cited as forming part of the  
prior art", the phrase used in Pozzoli and Plavix. The matter cited  
as forming part of the prior art is simply the prior art relied upon  
by the person alleging obviousness. Obviousness is not determined  
by reference to the prior art at large. The person alleging  
obviousness must point to one or more elements of prior art which  
make the impugned invention obvious. The choice of those  
elements of prior art is entirely in the hands of the party alleging  
obviousness, limited only by section 28.3 of the Act which sets out  
the cut-off date for opposable prior art. In fact, the challenger may  
rely on a combination of pieces of prior art under the "mosaic"  
theory of obviousness: Wenzel Downhole Tools Ltd. v. National-  
Oilwell Canada Ltd., 2012 FCA 333 at paragraph 87, [2014] 2  
F.C.R. 459.  
[158] Merck asserts that the “state of the art” is the prior art at large, not just a single reference  
in isolation. It asserts that this includes all of the prior art cited by Dr. Foley relating to P32/98,  
DPP-728 and LAF-237 and by Dr. Roush from his prior art and literature search attached to his  
report. Even if a medicinal chemist is not accepted as the PSA and Dr. Roush’s report is given  
less weight, Merck asserts that the prior art would include at least WO498 in its entirety and the  
Page: 54  
Deacon, Augustyns and Drucker papers referenced in the 400 Patent, which summarized the  
developments relating to P32/98, DPP-728 and LAF-237 and what was known about their DPP-4  
inhibitory activity.  
[159] Merck refers to Apotex Inc v Janssen Inc, 2021 FCA 45, which states at paragraph 25:  
Apotex makes several arguments concerning legal principles  
applicable to obviousness analysis. First, Apotex argues that  
obviousness is to be assessed by asking whether the distance  
between two points (the state of the art and the subject matter of  
the claim in question) can be bridged by the POS. Apotex argues  
that the second point (the subject matter of the claim) is to be  
determined by reference to the language of the claim. This is  
consistent with section 28.3 of the Patent Act and with the  
jurisprudence. Apotex also argues that the first point (the state of  
the art) is to be determined by reference not to the prior art at large,  
but rather to the prior art chosen by the party alleging obviousness.  
However, I do not understand the authorities cited by Apotex in  
support of this argument to limit the scope of prior art that can be  
considered for obviousness.  
[160] In many cases, the closest prior art is identified by the challenger and frames the analysis.  
In other words, if the claims of the patent are not obvious in view of the prior art that is closest to  
the claims, they would not be obvious by considering broader prior art, which is less relevant to  
the purported invention. However, that does not mean that the broader prior art is not relevant to  
other factors, such as motivation, as discussed further below.  
[161] In this case, the 400 Patent guides the analysis by identifying WO498 and the Deacon,  
Augustyns and Drucker references as being prior art that is relevant. While sitagliptin and the  
hydrochloride salt of sitagliptin are disclosed within WO498, the disclosure of these compounds  
Page: 55  
must be read and understood in context that is, within WO498 as this is how they would be  
known to the PSA (as noted by the 400 Patent).  
[162] Indeed, even Dr. Hollingsworth points to WO498 as being the starting point for the  
analysis in his report, where he states:  
190. In my view, the difference between the state of the art and  
Claim 4 (and its dependent claims) is the choice of the  
monohydrate crystal form of sitagliptin phosphate from the  
crystalline forms (including hydrates) that the PSA would have  
understood to be part of the WO 498 and would have presumed  
arose from a standard polymorph screen.  
...  
192. The 400 Patent identifies the WO 498 as the starting point.  
It acknowledges that sitagliptin and sitagliptin hydrochloride were  
known and disclosed (which they plainly were).  
[163] Applying this to the obviousness analysis, the question to be answered is whether  
bridging the gap between WO498 (which discloses sitagliptin and its hydrochloride salt, amongst  
other compounds) and the inventive concept of the claims of the 400 Patent would have been  
obvious to the PSA having regarding to the CGK and prior art. This includes consideration of  
the Deacon, Augustyns and Drucker references and the prior art relating to DPP-4 inhibitors as  
discussed under the motivation section below.  
D.  
Inventive Concept of the Claims in Question  
[164] There is some debate in the jurisprudence as to whether the obviousness analysis requires  
identification of an inventive concept or whether the essential elements as construed by the  
claims is the more appropriate end-point: Atazanavir at paras 65-70, 74-78; Ciba at paras 64-68,  
72-77.  
Page: 56  
[165] As noted in Atazanavir, the intention of the obviousness test set out in Sanofi was not to  
change the law of obviousness; the term “inventive concept” is not materially different from the  
previously used term “solution taught by the patent”: Atazanavir at paras 65-68, 75.  
[166] PMS argues that recourse should not be made to the inventive concept. Rather, the  
second point in the obviousness analysis should be the essential elements of the claims. It argues  
that the focus of the obviousness analysis should be on claim 4 and the claimed DHP salt of  
sitagliptin crystalline monohydrate, as the other claims do not add any features that can be  
inventive. It similarly asserts that if the inventive concept is to be considered, it would be  
focussed on the identification of sitagliptin as a phosphate salt that is in crystalline monohydrate  
form.  
[167] Merck argues that the inventive concept must be determined as it is a mandatory part of  
the Sanofi test. It contends that PMS’ argument ignores the latest word on the inventive concept  
from the FCA in Shire. Its experts assert that the inventive concept of claim 4 is the identification  
of sitagliptin phosphate monohydrate as a compound with: potent DPP-4 inhibitory properties;  
pharmaceutic advantages over sitagliptin free base and the hydrochloride salt; and particular  
advantages for preparing medicines of the pharmacologically active ingredient because of its  
enhanced chemical and physical stability (as compared to sitagliptin free base and the  
hydrochloride salt), and its high solubility. It asserts that claims 5-7 have the same inventive  
concept, but that the inventive concept of claims 19, 20 and 24 would be the process claimed to  
prepare the monohydrate. Similarly, it asserts that the inventive concept of claim 22 is that the  
monohydrate is useful to prepare medicaments to treat type 2 diabetes on account of its disclosed  
Page: 57  
properties, and that the inventive concept of claim 26 is the use of the monohydrate for treating  
type 2 diabetes with a therapeutically effective amount.  
[168] As noted in Shire at paragraphs 75 and 76, while identification of the inventive concept  
follows from, and is informed by, claims construction, claims construction and determination of  
the inventive concept serve two different purposes. Claims construction occurs before any  
assessment of the validity of the claims; its purpose being to interpret and determine the scope of  
the claim by looking at its subject matter. Identification of the inventive concept occurs within  
the assessment of the validity of the claims. Its purpose is to determine the proposed inventive  
aspect of the claim, to facilitate the obviousness analysis.  
[169] This is particularly important if recourse to the specification is required, such as in the  
case where a bare chemical formula is claimed or in the case of a selection patent: Sanofi at  
77-78; Shire at para 76. In such case, not all the chemical’s properties will inform its inventive  
concept, rather only those that provide the solution taught by the patent: Shire at para 76;  
Atazanavir at paras 74-75.  
[170] As was acknowledged by PMS in oral argument, if the patent is a selection patent, the  
Court may have regard to the inventive concept and may look to the disclosure to nourish what it  
is about the species that is claimed that is selective over the genus. However, PMS asserts that  
the 400 Patent is not a selection patent and there is no advantage explicitly disclosed with respect  
to the crystalline monohydrate claimed in the 400 Patent.  
Page: 58  
[171] It argues in such a case where the inventive concept cannot be easily grasped, the  
comments of the FCA in Ciba at paragraphs 74-77 should apply and the inventive concept  
should be avoided:  
[74] The reminder in Unilever that it is inventive concept of the  
claim which is in issue, “not some generalised concept to be  
derived from the specification as a whole,” is very apt: Unilever at  
page 569. Part of the difficulty in the search for the inventive  
concept is the use made, or to be made of the disclosure portion of  
the specification of the patent. In Connor Medsystems Inc v  
Angiotech Pharmaceuticals Inc [2008] UKHL 49, [2008] R.P.C.  
28 (Connor), Lord Hoffman wrote at paragraph 19 that “[t]he  
patentee is entitled to have the question of obviousness determined  
by reference to his claim and to some vague paraphrase based upon  
the extent of his disclosure in the description.”  
[75] This emphasis on the claims is consistent with section 28.3  
of the Act which stipulates that it is “the subject-matter defined by  
a claim” which must not be obvious.  
[76] Lord Jacob was alive to the possibility that difficulties in  
the identification of the inventive concept could lead to  
“unnecessary satellite debate”. His counsel was that “if a  
disagreement about the inventive concept of a claim starts getting  
too involved, the sensible way to proceed is to forget it and simply  
to work on the features of the claim”: Pozzoli at paragraph 19.  
Lord Hoffman wrote, once again in Connor at paragraph 20, that  
the inventive concept “is a distraction almost as soon as there is an  
argument as to what it is.”  
[77] There may be cases in which the inventive concept can be  
grasped without difficulty but it appears to me that because  
“inventive concept” remains undefined, the search for it has  
brought considerable confusion into the law of obviousness. That  
uncertainty can be reduced by simply avoiding the inventive  
concept altogether and pursuing the alternate course of construing  
the claim. Until such time as the Supreme Court is able to develop  
a workable definition of the inventive concept, that appears to me  
to be a more useful use of the parties’ and the Federal Court’s time  
than arguing about a distraction or engaging in an unnecessary  
satellite debate.  
Page: 59  
[172] The primary differences between the experts’ views on the inventive concept is whether  
it should include the purported advantages of the DHP salt of sitagliptin crystalline monohydrate  
and whether the inventive concept should be considered on a claim-by-claim basis. As set out  
above, in my view, the 400 Patent can be viewed as a selection patent. All experts, including  
PMS’ experts, recognized that the DHP salt of sitagliptin crystalline monohydrate purports to  
have enhanced chemical and physical properties.  
[173] As stated by Dr. Elitzin (Elitzin Report, Ex 66, paras 67-68):  
...the problem of the 400 Patent may be stated as a search for  
enhanced chemical and physical stability over the earlier sitagliptin  
disclosures in WO 03/004498 (free base and hydrochloride salt).  
... The summary of the invention section states plainly what the  
authors of the patent believe the solution to these problems is,  
namely sitagliptin phosphate monohydrate.  
[174] In my view, the inventive concept of claim 4 is the identification of the compound  
sitagliptin dihydrogenphosphate monohydrate with its enhanced chemical and physical  
properties over sitagliptin free base and the hydrochloride salt.  
[175] This overall inventive concept of the 400 Patent underlies the inventive concept of the  
remaining dependent claims, where claim 24 is directed to a process for reliably making the  
compound of claim 4 and claims 19 and 20 claim processes that can make the non-stereospecific  
compound. Claim 22 is directed to the enhanced ability to formulate the crystalline monohydrate  
into a medicament, and claim 26 recognizes the therapeutic efficacy of the crystalline  
monohydrate to treat type 2 diabetes.  
Page: 60  
[176] I do not agree with PMS that it can be concluded upfront that the Court does not need to  
take a claim specific approach in its analysis. The approach will depend on the Court’s findings  
with respect to claim 4. If I find that the compound of claim 4 is not obvious, then I agree that a  
process for making that compound and the use of the compound in a medicament or as a  
treatment would not be obvious. However, this same logic does not necessarily apply if I find  
that the compound is obvious. In that circumstance, the additional elements of claims 5-7, 19, 20,  
22, 24 and 26 would need to be considered to determine if they impart their own inventiveness:  
Section 58, Patent Act, Shire at para 27.  
E.  
Differences between the State of the Art and the Inventive Concept of the Claims  
[177] Following from the analysis above, the differences between the state of the art and the  
inventive concept can be summarized as:  
For Claim 4:  
identifying sitagliptin from amongst the other compounds disclosed within  
WO498 and the landscape of promising DPP-4 inhibitors, as a lead  
compound for further development;  
the choice to proceed with further salt screening and with polymorph  
screening;  
the formation and selection of the DHP salt of sitagliptin;  
Page: 61  
the isolation of the crystalline monohydrate form of the DHP salt and the  
recognition of its enhanced chemical and physical properties for  
formulation over sitagliptin free base and the hydrochloride salt.  
For Claims 5-7:  
the x-ray crystallographic characterization of the DHP salt of sitagliptin  
crystalline monohydrate  
For Claim 19, 20 and 24:  
the identification of a reliable process for making the DHP salt of the  
crystalline monohydrate  
For Claims 22 and 26:  
the recognition of the ability to use the DHP salt of the crystalline  
monohydrate in a pharmaceutical composition (claim 22) and in a  
therapeutically effective amount to treat type 2 diabetes (claim 26)  
F.  
Do the Differences Constitute Obvious Steps / Was it Obvious to Try  
[178] For an invention to be “obvious to try”, the evidence must show, on a balance of  
probabilities, that it was more or less self-evident for the skilled person to try to obtain the  
invention. Mere possibility that something might turn up is not enough: Sanofi at para 66.  
Page: 62  
[179] The parties drew the Court’s attention to three cases, which they asserted were factually  
relevant to the obvious to try analysis: Pfizer Limited v Ratiopharm Inc, 2010 FCA 204  
[Amlodipine]; Atazanavir; and Teva Canada Limited v Pfizer Canada Inc, 2019 FCA 15 [ODV].  
In two of the cases, Amlodipine and Atazanavir, the claims at issue dealt with a new salt and did  
not include claims to a crystalline form. Each of these cases turned on the issue of motivation,  
with the claims held obvious and the inventive concepts obvious to try.  
[180] In Amlodipine, the patent at issue was a selection patent that claimed the besylate salt of  
amlodipine. The inventors started with the specific task of looking at amlodipine maleate to see  
if it could be made into a final formulation for regulatory approval. The evidence established that  
it was (and would be) quickly determined that there were problems with stability and stickiness  
and that routine salt testing would then be used. The Court agreed with the trial judge’s factual  
finding that the skilled person “would be motivated to test sulphonic acid salts in general and  
would have every reason to test the besylate salt as this had already been shown to offer  
advantages over other salts in terms of stability” (at para 28).  
[181] In Atazanavir, the claims of the second of two patents were to the bisulfate salt of  
atazanavir, and to a pharmaceutical dosage form comprising the bisulfate salt. In that case, the  
FCA identified the inventive concept of the second patent as “atazanavir bisulfate, a salt of  
atazanavir which is pharmaceutically acceptable because it has equal or better bioavailability  
than the atazanavir free base.” It found there was no difference between the earlier patent, which  
claimed atazanavir and its pharmaceutically acceptable salts and atazanavir bisulfate, a salt that  
was pharmaceutically acceptable because of its bioavailability. The Court found that the skilled  
Page: 63  
person would have expected that a salt screen would likely identify at least one salt with  
improved pharmaceutical properties, specifically bioavailability, compared to the free base, with  
only routine work to characterize the salt’s properties.  
[182] In the third case, ODV, claims to a particular crystalline form of a particular salt of ODV  
(succinate salt) were held to be unobvious. In that case, the CGK included ODV as the active  
metabolite of venlafaxine, and ODV as a free base and fumarate salt. The prior art also disclosed  
ODV succinate as a potential salt, although there was some reason to believe that it might not  
work. The Court concluded that none of the prior case law, including Amlodipine and  
Atazanavir, supported a view that all salt screens and all polymorph screens were obvious to try  
or routine. Rather, each case had to turn on its own facts. On the evidence it found that the  
amount of experimentation required and the unpredictability of the outcome was high and  
rendered the solution taught not obvious to try. There was no finite number of predictable  
outcomes or number of potential experiments. The facts did not support a view that the PSA  
could predict that Form I ODV succinate existed, what properties it would have, or how it could  
be prepared, if at all.  
[183] While these cases serve as useful illustrations of the application of the obvious to try  
analysis to cases involving new salt and polymorphic forms, I adopt the same approach as the  
Court in ODV that each proceeding must turn on its own facts, evidence and arguments. There is  
no overriding principle that all salt screens are obvious to try and matters of routine, or that  
polymorph identification will always be unobvious. None of these cases can be used to force a  
conclusion that is not supported by the facts and evidence, an analysis of which is set out below.  
Page: 64  
Was it More or Less Self-evident that What was Being Tried Ought to Work  
(1)  
[184] There is no requirement to show that it is more or less self-evident that what is being tried  
ought to work; however, this factor remains as one of the factors to be considered in the obvious  
to try analysis: Hospira Healthcare Corporation v The Kennedy Trust for Rheumatology  
Research, 2020 FCA 30 [Infliximab] at para 90.  
[185] As set out above, the PSA, as part of their CGK, would have been aware of accepted,  
automated methods for salt and polymorph screening that were expected to yield results. They  
would have known that salt form determines the physicochemical properties of the product,  
including its stability, solubility and dissolution rate, and would influence how the drug is  
absorbed, distributed, eliminated and excreted by the body (TT V1, P:74, L:10-22). While it  
would have been expected that salt forms could improve chemical and/or physical properties and  
the overall therapeutic and pharmaceutical effects of an API, it was also understood that the  
wrong salt form might affect the compound negatively (TT V2, P:124 L:18-P:125 L:22; TT V3,  
P:280 L:6-17). Each salt imparts unique properties to the parent compound (TT V2, P:167  
L:21-27).  
[186] It is undisputed that phosphoric acid is one of the preferred acids referenced in WO498  
for possible salt formation with the basic compounds of the application. As agreed by the  
experts, phosphoric acid would have been one of the preferred acids that a PSA would include in  
a salt screening experiment with sitagliptin free base because of their differences in pKa (i.e. the  
level of acidity of the acid).