CENTER FOR DRUG EVALUATION AND
`RESEARCH
`
`APPLICA TION NUMBER:
`
`21-995
`
`PHARMACOLOGY REVIEW
`
`

`

`MEMORANDUM
`Oct. 15, 2006
`
`TO: File
`
`FROM: Kenneth L. Hastings, Dr.P.H., D.A.B.T.
`
`SUBJECT: NDA 21-995
`
`'
`
`I concur with Drs. Todd Bourcier and Karen Davis-Bruno that the marketing application for Januvia
`(Sitagliptin) may be approved based on review of nonciinic‘al data submitted by the sponsor.
`
`
`Kenneth L. Hastings, Dr.P.H., D.A.B.T.
`Associate Director
`
`Office of New Drugs
`
`

`

`This is-a representation of an electronic record that was signed electronically and
`this page is the manifestation of the electronic signature.
`
`/s/
`Kenneth Hastings
`10/16/2006 11:05:05 AM
`PHARMACOLOGIST
`
`‘
`
`_
`
`

`

`
`
`DEPARTMENT OF HEALTH AND HUMAN SERVICES
`PUBLIC HEALTH SERVICE
`FOOD AND DRUG ADMINISTRATION
`CENTER FOR DRUG EVALUATION AND RESEARCH
`
`PHARMACOLOGY/TOXICOLOGY REVIEW AND EVALUATION
`
`NDA NUMBER:
`
`SERIAL NUMBER:
`
`DATE RECEIVED BY CENTER:
`
`21-995
`
`000
`
`12/16/05
`
`PRODUCT:
`
`-
`
`Januvia (Sitagliptin)
`
`INTENDED CLINICAL POPULATION:
`SPONSOR:
`
`Type 2 Diabetics
`Merck
`
`DOCUMENTS REVIEWED:
`REVIEW DIVISION:
`
`'
`
`,
`eCTD
`Division of Metabolic and Endocrine Products
`
`PHARM/IOX REVIEWER:
`
`Todd Bourcier, Ph.D.
`
`PHARM/TOX SUPERVISOR:
`
`Karen Davis-Bruno, Ph.D.
`
`DIVISION DIRECTOR:
`PROJECT MANAGER:
`
`'
`
`,
`
`_
`
`Mary Parks, M.D.
`Lina Aljuburi, Pharm. D., M.S.
`
`Date of review submission to Division File System (DFS):731 August 2006
`
`

`

`TABLE OF CONTENTS
`
`EXECUTIVE SUMMARY .............................................................................................. 4
`Recommendations.................................................
`‘
`[.
`
`
`Summary of non-clinical findings ..........
`Brief overview of non-clinical findings ...................
`
`Non-clinical safety issues relevant to clinical use .............................................................. 9
`
`[1.
`‘ A.
`B.
`
`2.6.1
`
`INTRODUCTION AND DRUG HISTORY................................................................. 10
`
`2.6.2 PHARMACOLOGY ........................................... . ........................................................... 14
`2.6.2.1
`Brief summary ...................................................................................................................... 14
`2.6.2.2
`Primary! phannacodynamics ................................................................................................. 14
`
`Secondary pharmacodynamics ......................................................................................... 19
`2.6.2.3
`. Safety pharmacology ............................................................................................................ 19
`2.6.2.4
`2.6.2.5
`Pharmacodynamic drug interactions ..................................................................................... 22
`
`
`2.6.4 PHARMACOKINETICS/TOXICOKINETICS ....................................................... 22
`2.6.4.1
`Briefsummary ..................................................................
`...................... 22
`2.6.4.2
`Methods of Analysis
`...................................................p .......... 23
`2.6.4.3
`Absorption ....................................-. ....................................................................................... 23
`
`Distribution ................................................................................................... 24
`2.6.4.4
`2.6.4.5
`Metabolism ........................................................................................................................... 28
`2.6.4.6
`Excretion........ , ........................................................................................................... 31
`2.6.4.7
`Pharmacokinetic drug interactions ............................................................................. 32
`2.6.4.8
`Other Pharmacokinetic Studies .................................................................................. 32 '
`2.6.4.9
`Discussion and Conclusions .........................................................
`
`
`
`
`Tables and figures to include comparative TK summary ..................................................... 33
`2.6.4.9
`Proposed Metabolic Pathway of “C-MK-0431 in non-clinical test species and humans.......... 33
`Comparative Toxicokinetic Summary Table ............................................................................... 34
`Comparative pharmacokinetics of repeated oral doses in humans, dogs, and rats .................. 35
`
`2.6.6 TOXICOLOGY .............................................................................................................. 36
`
`Single-dose toxicity .......................................................................................................... 36
`2.6.6.2
`2.6.6.3
`Repeat-dose toxicity ......................................................................................................... 38
`
`TABLE: REPEAT DOSE TOXICITY STUDIES IN CD-l MICE...
`............................................... 41
`
`TABLE: REPEAT DOSE TOXICITY STUDIES IN SD RATS.................................................... 42
`TABLE: REPEAT DOSE TOXICITY STUDIES IN BEAGLE DOGS .......................................... 44
`
`2.6.6.4
`Genetic toxicology ...................................................................................................... 46
`
`2.6.6.5
`Carcinogenicity...........
`.............................. 49
`
`BriefSummary
`.'..... 49
`Carcinogenesis in Sprague-Dawley Rats: 2 year study
`............................................... 49
`Carcinogenesis in CD-l Mice: 2 year study.................................................................................. 53
`2.6.6.6
`Reproductive and developmental toxicology ........................................................................ 55
`Oral Fertility study in Female Rats ......................................................................... 57
`Oral Fertility study in Male Rats .._................................................................................................ 62
`Oral dose range-finding reproduction study in pregnant female rats .................................... 67
`Oral developmental toxicity study inrats 69
`Oral range-finding study in pregnant rabbits .............
`Oral range-finding study in non-pregnant rabbits .....
`Oral developmental toxicity study in rabbits ..............
`Oral postnatal developmental toxicity study in rats...
`TABLE: REPRODUCTIVE TOXICITY STUDIES ............................................................................... 98
`
`
`
`

`

`100
`Oral Toxicokinetic Study in Pregnant and Lactating Rats ................................................
`Oral Toxicokinetic Study in Pregnant Rabbits ........................................................ 102
`
`Special toxicology studies ........................g...................................................................... l 04
`2.6.6.8
`Skin lesion assessment ‘of sitagliptin in a 14-week oral toxicity study in monkeys.................. 104
`Skin lesion assessment of L-000000826, a non-selective DPP4 inhibitor, in a 12-week oral
`toxicity study in monkeys ................................................................................,............................ 109
`Skin lesion assessment of L-000233357, a DPP8/9 selective inhibitor, in a 14-week oral toxicity
`study in monkeys .......................................................................................................................... 110
`
`MK—0431 + Metformin: Combination Toxicity Studies in Dogs:
`115
`MK—0431 + Metformin: 14 week oral toxicity study in dogs.................................................... 115
`' Exploratory 5—week oral tolerability study with Metformin in female dogs ........................... 126
`MK-0431 + Metformin: 16 week oral toxicity in female dogs.................................................. 130
`
`APPENDIX/ATTACHMENTS ............................................................................................... 136
`
`

`

`
`
` Reviewer: Todd Bourcier NDA No. 21 995
`
`EXECUTIVE SUMIIIAR Y
`
`I. Recommendations
`
`A. Recommendation on approvability
`AP A roval
`Pharmacology/Toxicology recommends approval of NDA 21,995 (Januvia®)
`
`. Recommendation for nonclinical studies
`
`No additional nonclinical studies are required.
`
`Recommendations on labeling
`
`8. Use in Specific Populations
`8.1 Pregnancy
`Pregnancy Category B
`There are no adequate and well-controlled studiesin pregnant
`women; ‘ R
`
`“V
`
`3
`
`recommended for use in pregnancy unless clearly needed. Merck &
`Co., Inc. maintains a registry to monitor the pregnancy outcomes of
`Women exposed to Januvia while pregnant. Health care providers are
`encouraged to report any prenatal exposure to Januvia by calling the
`Pregnancy Registry at (800) 986-8999.
`
`
`
`Sitagliptin administered to pregnant female rats and rabbits
`____.____ was not teratogenic at oral doses up to 250 mg/kg (rats)
`and 125 mg/kg (rabbits), or approximately 30- and 20-times human
`exposure at the maximum recommended human dose (MRHD) of
`100mg/day based on AUC comparisons. Higher doses ' “—
`
`increased the incidence of —- rib
`
`'
`
`malformations in offspring at 1000 mg/kg,
`m
`
`Sitagliptin administered to female rats \— '
`--""“
`decreased the average body weight in male and '
`
`female offspring at 1000 mg/kg I".
`
`m A
`
`
`
`3 . No functional or behavioral
`toxicity was observed in offspring of rats.
`
`placental transfer was approximately 45% at 2 hours and
`__
`80% at 24 hours postdose. C.
`——-—_—————-—-_—‘—_—"
`
`3 placental transfer was approximately 66% at 2
`hours and 30% at 24 hours.
`
`

`

`Reviewer: Todd Bourcier
`
`'
`
`_
`
`_
`
`NDA No. 21,995
`
`8.3. Nursing Mothers
`Sitagliptin is excreted in the milk of lactating rats at a milk to plasma
`ratio of 4:1. It is not known whether sitagliptin is excreted in human milk.
`
`Because many drugs are excreted in human milk E,
`m ,3 a decision
`should be made whether to discontinue nursing or to discontinue the drug,
`taking into account the importance of the drug to the mother.
`
`13. Nonclinical Toxicology
`l3.l Carcinogenesis, mutagenesis, impairment of fertility
`
`A two year carcinogenicity study was conducted in male and female
`rats given oral doses of sitagliptin of 50, 150, and 500 mg/kg. There was an
`increased incidence of combined liver adenoma/carcinoma in males and
`
`females and of liver carcinoma in females at 500 mg/kg. This dose results
`in approximately 60 times the human exposure at the maximum
`recommended daily adult human dose (MRHD) of 100 mg/day based on
`AUC comparisons. Liver tumors were not observed at 150 mg/kg,
`approximately 20 times human exposure at the MRHD.
`
`A two year carcinogenicity study was'conducted in male and female
`mice given oral doses of sitagliptin of 50, 125, 250, and 500 mg/kg. There
`was no increase in the incidence of tumors in any organ up to 500 mg/kg,
`approximately 70 times human exposure at the MRHD.
`
`'
`
`Sitagliptin was not mutagenic or clastogenic with or without metabolic
`activation in the Ames bacterial mutagenicity assay, a Chinese hamster
`ovary (CHO) chromosome aberration assay, an in vitro cytogenetics assay
`in CHO, an in vitro rat hepatocyte DNA alkaline elution assay, and an in
`vivo mouse micronucleus assay.
`
`In rat fertility studies with oral gavage doses of 125, 250, and 1000
`mg/kg, males were treated for- weeks prior to mating and females were
`treated -weeks prior to mating through gestation day 7. No adverse effect
`on fertility was observed at 125 mg/kg (approximately 12 times human
`exposure at the MRHD of 100 mg/day based on AUC comparisons).
`Higher doses increased resorptionsa in females
`at approximately 25 times human exposure at the MRHD based on AUC
`comparisons.
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`II. Summary of non—clinical findings
`
`A. Brief overview of non-clinical findings
`
`‘
`Pharmacology
`MK—O43l (sitagliptin phosphate) is a competitive inhibitor of dipeptidyl peptidase 4
`(DPP4), an enzyme principally responsible for degrading incretin peptides glucagon—like
`peptide—l (GLP—l) and glucose~dependent insulinotropic peptide (GIP). MK-043l
`prolongs incretin half-life and biological activity and thus potentiates glucose-dependent
`insulin release and delays gastric emptying. In non—clinical models of diabetes, MK-043l
`moderates glucose excursion and improves insulin release and islet cell function/mass
`without provoking hypoglycemia. MK-O43l is body weight-neutral, unlike marketed
`glitazones (weight gain) and GLP-1 analogues (weight loss).
`
`Immunomodulatory effects of DPP4 (aka CD26) are reportedly not altered by MK-
`0431, based on normal responses of murine T- and B-cells to antigens and mitogens.
`However, rodent DPP4/CD26 differs in some aspects from human DPP4/CD26 (e.g.,
`binding of adenosine deaminase) and Merck’s experiments did not directly test the T-
`helper memory function ascribed to CD26. Therefore, the non-clinical data do not
`adequately predict potential effects of MK-0431 on DPP4/CD26’s role in human
`immunity.
`
`Safety pharmacology assessment of neurological, renal, pulmonary, and
`gastrointestinal effects of MK-043l did not identify any significant liabilities.
`
`Absorption, Distribution, Metabolism, and Excretion
`An oral dose of MK—0431 is rapidly absorbed and is 60—90% bioavailable in rats and
`dogs. MK-O43l distributes to most rat tissues with low amounts distributing to the brain,
`eyes, and bone. Plasma protein binding is moderate (30%). Metabolism of MK-043l is
`minimal with 80% of unchanged parent compound being eliminated in the urine of rats,
`dogs, and humans. Oxidative metabolism by CYP3A4 and 2C8 is a minor metabolic
`_ pathway. MK-0431 has a longer plasma half-life in humans ,(l3hrs) than in rats and dogs
`(2-5 hrs) probably due to different rates of renal elimination. MK-043l slightly
`accumulates in humans but not in dogs or rats after multiple dosing.
`
`MK-043l is a P-glycoprotein and hOAT3 substrate, but does not interfere in the
`shuttling of other substrates via these transporters in vitro. MK-0431 does not inhibit
`CYP450 enzymes or indUce CYP3A4. The results predict a low probability for
`pharmacokinetic drug interactions via these pathways.
`.
`
`General Toxicology (MRHD, Maximum Recommended Human Dose, or 100mg)
`- Single dose studies identified minimum lethal doses of 2000mg/kg (200-400x
`MRHD) in mice and 3000mg/kg (150-300x MRHD) in rats. Little other toxiCOlogical
`information was obtained in these studies.
`
`

`

`
`
`Reviewer: Todd Bourcier NDA N0. 21 995
`
`Repeat dose studies were conducted in Sprague-Dawley ratsand Beagle dogs up to 6
`months and 12 months duration, respectively.
`
`A high-dose 3-month study in rats identified kidney and liver necrosis, myocardial
`degeneration, bone marrow necrosis, and death at 1500 and 2000mg/kg (150—200x
`MRHD). Kidney toxicity was also observed in mice at 500mg/kg. Note that exposure at
`these high doses is theoretically sufficient to inhibit off-target enzymes DPP8/9, proteases
`that are associated with these toxicities.
`
`Administration of doses up to 20x the MRHD for 6 months in rats did not elicit
`significant toxicity.
`
`Studies in dogs identified NOAEL doses based on clinical signs that consisted of
`reduced activity, hunched posture, ataxia, tremor, and sporadic emesis observed at
`50mg/kg (20x MRHD). Respiratory distress, described as audible and labored breathing
`and open-mouthed breathing, was also reported. No consistent target organs were
`identified in these studies.
`
`Administration of doses up to 5x the MRHD for up to 12 months in dogsdid not elicit
`significant toxicity.
`
`Special Toxicology
`MK-043l did not produce vascular/skin lesions in rhesus monkeys, as seen with some
`DPP4 inhibitors, after three months administration of doses up to 25x the MRHD.
`Mechanistic data provided by Merck suggests that inhibiting DPP4 activity alone15 not
`sufficient to produce this toxicity
`The combination of MK-0431 and high-dose (50 mg/kg) but not low-dose (20 mg/kg)
`metformin in dogs may have resulted in more numerous and earlier deaths than observed
`with metformin alone. The lower dose of metforrnin (20 mg/kg) better approximates
`maximum human exposure to metformin (2500mg/day). Convincing evidence is provided
`by Merck that high-dose metformin is responsible for the deaths observed in combination
`with MK-0431. Nevertheless, there is a slight possibility of exacerbated toxicity in the
`setting of high metformin exposure and clinical exposure to MK—043 1.
`
`Reproductive Toxicology
`Exposure to MK-04311n the definitive studies ranged from 12x to 90x MRHD1n the
`rat and 6x to 50x1n the rabbit. Resorptions and post-implantation losses increasedIn
`females in a fertility study at ~25x MRHD; male fertility was not effected. MK-0431 was
`not teratogenic but increased the incidence of skeletal malformations in rat pups at
`maternally toxic doses. At maternally non-toxic closes, a single rat pup had multiple
`skeletal abnormalities (incidence within historical range), and a single rabbit pup had
`multiple cardiovascular abnormalities, but a relationship to drug treatment is not
`conclusive. MK—0431 crosses the placenta in rats and rabbits and is excreted in maternal
`milk at a 4:1 ratio to plasma. As with other oral hypoglycemic agents, MK-0431 should
`not be given to pregnant or nursing mothers and Merck will maintain a pregnancy
`register. Pregnancy Category ‘B’ is recommended.
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`There were no conclusive drug—related effects on embryonic/post-natal development
`in rats at 125mg/kg (12x MRHD) or in rabbits at 125mg/1<g(20x MRHD).
`
`-
`Genetic Toxicology
`MK—0431 was not mutagenic or clastogenic in three in vitro assays (Ames,
`hepatocyte alkaline elution, and chromosome aberration) and one in vivo assay (murine
`micronucleus induction).
`'
`
`Carcinogenicity
`Carcinogenic potential of MK-0431 was evaluated in 2 year studies in
`mice and rats. Both studies adequately assessed carcinogenesis. MK-043l significantly
`increased the incidence of combined liver adenoma/carcinoma in male and female rats,
`and increased liver carcinomas in female rats at 500mg/kg (62x MRHD). Non-genotoxic,
`chronic hepatotoxicity is the suggested etiological event but this is based on weak
`correlative evidence of liver toxicity. MK-0431 did not produce any drug—related tumors
`in CD-1 mice up to 500mg/kg (72x MRHD). MK-0431 poses a minimal carcinogenic risk
`to humans.
`V
`
`mam Original
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`B. Non-clinical safety issues relevant to clinical use
`
`.1. DPP4 cleaves several substrates in addition to GLP-l. Therefore, MK-O43l may
`have undesirable effects related to inhibiting cleavage of non-incretin substrates.
`Effects on human immunity, specifically recall responses to antigens and immune
`cell trafficking, may be adversely effected by DPP4 inhibition. This risk is an
`unavoidable characteristic of MK—0431 and the drug class There15 currently no
`clinical evidence of such effects with Januvia.
`
`MK-043l presents a marginal clinical risk of producing skin lesions with
`prolonged administration. This conclusion is based on the absence of skin
`findings in the 3-month monkey study, on mechanistic data suggesting that
`inhibiting DPP4 activity alone is not sufficient to produce this toxicity, and on the
`high DPP4 selectivity of MK—O431 at clinical exposure. Risk assessment for skin
`lesions must be done on a case-by-case basis and is not evidence of similar safety
`with other DPP4 inhibitors currently in clinical development.
`
`The combinatibn of MK-0431 and high-dose metformin (50 mg/kg) in dogs may
`have resulted in more numerous and earlier deaths than observed with metformin
`alone. The combination of MK-043l and a lower dose of metformin (20 mg/kg)
`that better approximates human exposure at 2500mg/day resulted in no deaths and
`yielded no evidence of exacerbated toxicity. Convincing evidence is provided that
`the deaths at 50 mg/kg is due to metformin toxicity and not to the combination.
`Nevertheless, there is a slight possibility of exacerbated toxicity in the setting of
`high metformin exposure (2 40011M*h AUC) and clinical exposure to MK-043l
`(~10uM*h AUC).
`
`,5on
`mpgg‘ougflfi
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`2.6 PHARMACOLOGY/1‘OXICOLOGY REVIEW
`
`2.6.1
`
`INTRODUCTION AND DRUG HISTORY
`
`NDA number: 21-995
`Review number:
`1
`
`Sequence number/date/type of submission:
`Information to sponsor: Yes (X) No ( )
`Sponsor and/or agent: Merck Research Laboratories
`Manufacturer for drug substance:
`Merck in Barceloneta, Puerto Rico, Vincenza, Italy, and Visp, Switzerland
`Reviewer name: Todd Bourcier
`-
`Division name: Metabolic and Endocrine Products
`
`Review completion date:
`Drug;
`
`31 August 2006
`
`Trade name:
`
`Januvia
`
`Generic name: Sitagliptin phosphate
`Code name: MK-0431; L-000224715—010X
`Chemical name:
`
`7[(3R)—3-amino-11-o-xo--4(2,4,5-trifluorophenyl)butyl]-5 ,,6 7, 8-t-etrahydro—[3-
`(trifluoromethyl)— 1,2,4-triazolo[4,3—a]pyrazine phosphate (1: l) monohydrate
`CAS registry number: 654671-77-9
`Molecular formula/ weight: C15H15F6N50 - H3PO4 ° H20 /523.32 MW
`Structure:
`
`
`1W 11““?
`; 63,634 (BMS);
`Relevant INDs/NDAs/DMFS 62,278 (Novartis);
`
`67, 369 (GSK); 65,495 (Merck),
`;
`I —— 69,707 (PPD)
`
`
`
`Drug class: dipeptidyl-peptidase IV (DPP—IV) inhibitor
`
`Intended clinical population: 'Type 2 Diabetics
`
`Clinical formulation: MK—O431 monohydrate phosphate salt (25, 50, 100 mg tablets)
`Tablets contain microcrystalline cellulose, calcium phosphate dibasic, croscarmellose sodium,
`magnesium stearate, sodium stearyl fumarate. Tablets are pink, light beige, or beige depending on
`dosage strength.
`
`ROute of administration: Oral
`
`Maximum Recommended Human Dose: Merck seeks approval of 25, 50, and 100mg.
`.The 100mg qd strength provides an average AUC of 10 uM*h and a Cmax of 1 11M.
`
`10
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`Disclaimer: Some Tables and Figures from the electronic NDA submission have been
`copied for use in this review
`
`11
`
`

`

`V Reviewer: Todd Bourcier
`
`.
`
`NDA No. 21,995
`
`Studies reviewed within this submission: -
`
`Primary Pharmacodynamics
`'Affinity for human and animal DPP-IV Human, mouse, rat, dog In vitro
`Activity in T cell activation assays Mouse In vitro
`Acute efficacy in oral glucose tolerance test Mouse P.O.
`Pharmacodynamics in oral glucose tolerance test Mouse P.O.
`Acute efficacy in model of diet-induced obesity Mouse P.O.
`Acute efficacy in db/db mice Mouse R0.
`Selectivity of MK-O43l for DPP-IV Human, cow, pig, rabbit, rat_ In vitro
`Selectivity of comparator compounds for DPP-IV Human, pig In vitro
`
`Safety Pharmacology
`Respiratory assay Rat P.O. MK-0431 Tablets
`Cardiovascular telemetry assay Dogs P.O. _
`.
`Oral functional observational battery assay Rats P.O.
`Cellular electrophysiological evaluation of MK-0431 on I-IERG CHO In vitro
`Cardiovascular effects: rising dose study Dog IV
`Renal function and electrolyte excretion Dog P.O.
`Respiratory function, hemostasis, and platelet function Dog IV
`Gastric acid secretion Dog P.O.
`Gastrointestinal motility Mouse P.O.
`Behavioral and Other CNS Effects
`
`Pharmacokinetics
`
`Absorption
`Phannacokinetics in rat and dog
`_ Oral bioavailability and dose dependence in rat and dog
`
`Distribution
`
`Single-dose tissue distribution in rat
`Placental transfer in rat and rabbit
`
`Reversible plasma protein binding
`Serum albumin and (ll-acid glycoprotein binding
`Blood-to-plasma partitioning
`P-glycoprotein mediated transport, mouse and human
`Uptake by renal transporters, human
`
`-
`7
`Metabolism
`Metabolites in plasma, mouse and rabbit
`Metabolites in plasma, liver, kidney, urine, and bile in rat
`Metabolites in plasma, urine, and bile in dog
`Metabolites in plasma, urine, and feces in human
`Identification of metabolites M2 and M5 in dog
`Metabolism in liver microsomes, mouse, rat, rabbit, dog, monkey, human
`Metabolism in hepatocytes, rat, dog, human
`'
`Metabolism in recombinant cytochromes P450 in human
`Inhibition of cytochromes P450
`Induction of cytochrome P450 3A4
`Effect on MDRl P-glycoprotein-mediated transport
`
`Excretion
`
`‘
`Mass balance in rats and dogs
`Urinary and biliary excretion in rats and dogs
`Excretion into milk in rat
`
`12
`
`

`

`
`
`RevieWer: Todd Bourcier , NDA No. 21 995
`
`General Toxicology
`Single dose toxicity in mouse and rat (anhydrous and monophosphate salt formulations)
`Repeat dose toxicity studies and their duration:
`CD-l Mouse:
`1 and 3 months
`
`Sprague Dawley Rat:
`Beagle Dogs:
`
`2 weeks, 3 months, 3 months high-dose, 6 months
`2 weeks, 3, 6, and 12 months
`
`Genetic Toxicology
`Ames Assay (in vitro)
`Primary rat hepatocytes (in vitro)
`Chinese hamster ovary cells (in vitro)
`Micronucleus induction in mice afier single oral dose (in vivo)
`
`Carcinogenicity
`106 week oral gavage in CD-1 mice and toxicokinetic analysis
`106 week oral gavage in SD rats and toxicokinetic analysis
`
`.
`
`Reproductive/Developmental Toxicology
`Male and female fertility in rat
`Rat Embryonic Development (dose-ranging and definitive studies)
`Rabbit Embryonic Development (dose-ranging and definitive studies)
`Rat Post-natal Development
`
`Special Toxicology Studies
`Denna] sensitization in mice, rabbits, and humans . ’-——-'-'
`Ocular toxicity in bovine cornea (in vitro) and in rabbits (in vivo)
`Intravenous administration of MK-0431 for 16 consecutive days in rats and dogs
`Skin lesion assessment of sitagliptin in a 14-week oral toxicity study in monkeys
`Skin lesion assessment of L-000000826 in a 12—week oral toxicity‘study in monkeys
`Interim Report: Skin lesion assessment of L—000233357 in a 14-week oral toxicity study in monkeys
`MK-0431 + Metformin: Combination Toxicity Studies in Dogs: Summary
`MK-0431 + Metformin: 14 week-oral toxicity study in dogs
`Exploratory 5-week oral tolerability study with Metformin in female dogs
`MK-O43l + Metformin: 16 week oral toxicity in female dogs
`'
`
`l3
`
`

`

`
`
`Reviewer: Todd Bourcier NDA No. 21 995
`
`2.6.2 PHARMACOLOGY
`
`2.6.2.1 Brief summary
`
`MK-0431 is a triazolopiperazine-based competitive inhibitor of dipeptidyl peptidase 4
`(DPP4). MK-043l selectively inhibits DPP4 activity in serum from humans, rodents, and
`. dogs with high potency (IC50, 18-69nM; Ki, 9nM). Inhibitory activity against closely
`related proteases, including DPP8/9, and a panel of unrelated enzymes and ion channels
`is minimal (ICso, 48pM to >100 uM) and not relevant at clinical drug concentrations
`(~l.0 pM at a 100mg dose). The DPP4 selectivity of MK-0431 is superior to vildagliptin,
`a DPP4 inhibitor being developed by Novartis. The selectivity of MK-0431 for DPP4
`minimizes the potential for toxicities associated with inhibition of DPP8/9.
`
`MK-043l bound to serotonin receptors with a Ki of 2-5 pM, but was devoid of agonist
`activity; it is not known if MK-0431 interferes with endogenous serotonergic activity.
`Merck states that MK-0431 distributes poorly to the brain (1/10th plasma) and that
`5HT2A antagonists are used clinically.
`
`DPP4, also known as CD26, contributes to the co—activation of memory/helper T-cells to
`recall antigens. MK-043l did not suppress murine T- and B-cell activation in a series of
`in vitro activation assays. Other selective DPP4 inhibitors did not suppress reactivity of
`human peripheral lymphocytes, but MK-0431 was not specifically tested. These
`experiments did not address the memory T-cell function of CD26 and are of uncertain
`value in predicting the effect of MK-0431 on human immunity.
`
`MK—0431 showed efficacy in lean mice, diet-induced obese mice, and in db/db mice.
`MK-043l inhibited plasma DPP4 activity, increased plasma GLP—1, and reduced blood
`glucose excursion in a dose-dependent manner. Efficacious plasma drug concentrations
`were 200-700nM, sufficient to inhibit plasma DPP4 activity more than 90%. For
`comparison, the Cmax at the 100mg clinical dose is 1000nM.
`
`2.6.2.2 Primary pharmacodynamics
`
`Mechanism of action:
`
`MK-043I inhibits DPP4 in vitro: MK-043l inhibits activity of human recombinant DPP4
`by 50% at 17.9 nM (IC5o, Figure 1). The range for inhibitory activity is ~5nM to
`lOOOnM, representing ~20% to 99% inhibition of DPP4 activity against a fluorogenic
`dipeptide substrate (Gly-Pro—AMC). Inhibitory activity of MK-0431 was competitive and
`reversible.
`
`MK-0431 inhibits activity of native DPP4 from humans and from species used for
`toxicology testing with similar potency (16-69nM, Table l). MK-0431 inhibits free
`DPP4 in serum as well as membrane-bound enzyme (CACO-2 extracts).
`
`14
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`Reviewer: Todd Bourcier
`
`'NDA No. 21,995
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`Table 1: Inhibition of DPP4 from various
`sources by MK-0431
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`Figure 1: In vitro inhibition of human
`recombinant DPP4 by MK-043l
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`MK-0431 is selective for DPP4 in vitro: MK—0431 Selectively inhibits activity of DPP4
`relative to closely-related prol-ine specific serine proteases (Table 2), although FAPa was
`not assayed. MK-04'3l inhibits DPP8 activity with ~2,500 fold less potency compared to
`DPP4, based on IC50 values.
`
`MK-043l was also screened for activity against a panel of unrelated proteases and ion
`channels (Tables 3 & 4). Granzyme B and gamma-secretase were inhibited with an ICso
`2 10 uM, and L-type calcium channels with an ICso of 22uM. These concentrations are
`approximately 500—fold and lOOO-fold higher than the [C50 for DPP4 activity.
`
`MK—0431 bound to rat serotonin receptors 5HT2 (Ki, 5.8 uM) and 5HT2A (Ki, 2.1 uM),
`but no agonist activity was observed up to lOuM concentration.
`
`The potential for MK-0431 to exhibit off-target inhibitory activity at clinically relevant
`concentrations is minimal. The low inhibitory activity against related DASH members
`(DPP4 Activity & Structural Homologs) minimizes the toxicities associated with DPP8/9
`inhibition in rats and dogs (e.g., thrombocytopenia, mortality in rats, gastrointestinal
`toxicity in dogs). Despite the minimal off-target potential of MK-043 l, substrate
`promiscuity of DPP4 activity and its possible sequalae is an unavoidable characteristic of
`MK-043-l and the drug class.
`
`15
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`
`
` Reviewer: Todd Bourcier . ' NDA No. 21 995
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`Table 3:
`MK-O43l inhibition of selected proteases
`
`Table 4:
`_
`MK-043l inhibition of selected ion channels
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`MK-0431 selectivity Vs. comparator compounds: NIK-043l (L-000224715 in Table 5)
`exhibits a superior selectivity profile compared to a panel of other DPP4 inhibitors,
`including the Novartis compound LAF237 (vildagliptin) currently in Phase 3 clinical
`trials. The threo-, allo- and DPP8/9 selective compounds produced toxicity in rats and
`dogs, including thrombocytopenia, anemia, multiple organ histopathology, and mortality
`(Lankas 2005). The threo- and allo-Ile non--selective compounds also produced similar
`toxicity in DPP4 deficient mice MK-0431 did not produce these toxicities in this study,
`indicating that several toxicities are associated with inhibition of DPP8/9 but not DPP4.
`A highly selective inhibitor of DPP4 would therefore avoid such DPP8/9-related
`toxicities.
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`l6
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`

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`Reviewer: Todd Bourcier NDA No. 21 995
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`lLankas GR, et al. (2005) Diabetes (lO):'2988-94.
`This study was conducted by the Dept. ofSafety Assessment. Merck Research Laboratories
`
`Table 5:1n vitro selectivity ofcomparator DPP4 inhibitors (ICso, uM)
`
`
`
`MK-0431 activity in marine Tcell activation assays in vitro.‘ DPP4, also known as CD26,
`is thought to contribute to co-activation of memory/helper T-cells. MK-0431 was
`therefore evaluated over a concentrationrange of 12nM to SOuM in several in vitro-
`activation assays with murine T- and B-cells. MK-0431 did nOt inhibit T-cell
`proliferation in the mixed splenic lymphocyte reaction (MLR) or in response to antigen,
`and did not alter lipopolysaccharide-induced proliferation of B cells. The Lankas article1
`reported that DPP4—selective compounds do not suppress in vitro proliferation of human
`peripheral blood lymphocytes in response to phytohemagglutinin or staph enterotoxins
`but less selective compounds do have inhibitory activity. MK-O43l was not evaluated in
`that experiment.
`
`DPP4/CD26 in mice and rats differs in some aspects from the human form”, despite
`~85% homology across species (e.g., ADA binding). In addition, the in vitro assays done
`by Merck do not clearly test the helper functions ascribed to CD26 on memory T-cells
`(e.g., human T—cell response to tetanus toxoid-loaded antigen presenting cells). At least in
`mice, MK-043l does not suppress T— and B-cell activation, but the possible effect on
`human immunity is unknown. '
`
`‘Lankas GR, etal. (2005) Diabetes (10):2988-94.
`This stua’y was conducted by the Dept. ofSafety Assessment, Merck Research Laboratories
`
`ZIwaki-Egawa S,