CENTER FOR DRUG EVALUATION AND
`
`RESEARCH
`
`APPLICA TION NUMBER:
`
`21-2 72
`
`PHARMACOLOGY REVIEW
`
`

`

`NDA 21-272
`
`REVIEW AND EVALUATION OF PHARMACOLOGY
`AND TOXICOLOGY DATA
`
`Xavier Joseph, D.V.M.
`March 12, 2001
`
`ORIGINAL NDA DATED: August 11, 2000
`CENTER RECEIPT DATE: August 14, 2000
`REVIEWER RECEIPT DATE: August 15, 2000
`
`SPONSOR: United Therapeutics Corp.
`P.O.Box 14186, Research Triangle Park, NC 27709
`
`DRUG PRODUCT: Remodulin Injection
`
`DRUG: Generic name —- Treprostinol sodium
`Codenames - UT-15,15AU81andLRX-15
`OH
`
`
`
`- H
`cameo,
`
`N:
`
`M.W. 412.49
`
`FORMULATION: Remodulin Injection is a sterile sodium salt solution supplied in 20
`ml multi-use vials containing 1.0, 2.5, 5.0 or 10.0 mg/ml of treprostinol. Each ml of the
`formulation also contains 5.3 mg sodium chloride (except
`for the 10.0 mg/ml
`concentration which contains 4.0 mg sodium chloride), 3.0 mg metacresol, and 6.3 mg
`sodium citrate. Sodium hydroxide and hydro~chloric acid are added to adjust the pH
`between 6.0 and 7.2.
`
`PHARMACOLOGICAL CLASS: Prostacyclin (PGlz) analog
`
`PROPOSED INDICATION: Treatment ofpulmonary arterial hypertension (PAH)
`
`PROPOSED DOSAGE REGIMEN: Remodulin is administered by continuous
`subcutaneous infusion at an initial infusion rate 51.25 ng/kg/min, with upward and
`downward adjustments based on PAH symptoms and drug-related adverse effects. It is
`recommended that increments not exceed 1.25 ng/kg/min per week for the first four
`weeks and 2.5 ng/kg/min per week for the remaining duration of infusion.
`
`IND UNDER WHICH CLINICAL TRIALS WERE CONDUCTED: .
`
`.——---'""
`
`

`

`z‘un hJ—blh
`
`.
`SUMMARY OF PHARMACODYNAMIC STUDIES
`
`TABLE o'F CONTENTS
`
`4
`
`Page
`
`1. In Vitro Studies Related to Proposed Indication
`
`Platelet Antiaggregatory Activity
`
`Vascular Relaxation Efiect ---
`
`-—..—...—......................- 3
`------—----—---~
`4
`
`Antiproliferative Effect in Pulmonary Artery Smooth Muscle Cells
`2. In Vivo Studies Related to proposed Indication
`Platelet Antiaggregatory Activity ......._..._.._................-...,._._.........__ 5
`Vasodilator and Hemodynamic Activity
`Anesthetized AnimalsWMMW 6
`Conscious Animals ......_...-............_.............._................._.....__ l8
`
`4
`
`3. Safety Pharmacology Studies ----————~—--—----—--—-—---—---
`
`21
`
`SUMMARY OF PHARMACOKINETIC STUDIES
`
`1. Absorption -—~m--—-~Wmm-—-m--- 22
`2. Tissue Distribution m~~--m—----—--------m'-m 28
`
`3. Metabolism
`............_.”..._-...._-...-..--..--__..__..-..............._ 3 l
`
`4. Plasma Protein Binding ——----»«--.--—-----—---------—-mmmmmmmm 3 3
`5. Excretion -----—---»-»--—----~----—-------»---»-------------- 3 3
`
`SUMMARY OF GENERAL TOXICITY STUDIES
`
`
`-~ 36
`1. Acute and 14-Day Subcutaneous Toxicity Studies in Rats and Dogs --
`
`38
`2. Twenty-six Week Continuous sc Infusion Toxicity Study in Rats -—---—
`
`3. Twenty-six Week Continuous sc Infusion Toxicity Study in Dogs —------ 47
`
`SUMMARY OF REPRODUCTIVE TOXICITY STUDIES
`
`1. Fertility Study in Rats ..__..........__..-..............-..___......................... 54
`2. Developmental Toxicity Study in Rats -—-----‘-—-—-------»-—-—----—-—---—---4— 61
`3. Developmental Toxicity Study in Rabbits ....._...........--...._......................- 77
`
`4. Pre- and Postnatal Developmental Study in Rats
`--—-—-—--———»—---
`92
`
`SUMMARY OF GENOTOXICITY STUDIES --'-—-—--—-.-—----—~-----—-109
`
`OVERALL SUMMARY AND EVALUATIONMW 127
`
`RECOMMENDATIONwmmm—m 13 5
`
`

`

`NDA 21-272
`
`3
`
`SUMLIARY OF PHARMACODYNAMIC STUDIES
`
`(The pharmacological data submitted in this new drug application are compiled from
`studies conducted at theM
`
`W _
`
`UT-lS (fonnerly known as lSAUSl or LRX- 15), a chemically stable tricyclic benzindene
`analogue'of prostacyclin (PGIz, cpoprostenol),is currently being developed for the treat-
`ment of pulmonary arterial hypertension. In vitro andm ijoopharmacodynamic studies
`have shown that UT-l 5 possesses systemic and pulmonary vasodilatory and platelet anti-
`aggregatory properties. These studies are summarized below.
`
`In Vitro Studies Related to Proposed Indication
`
`1. Platelet Antiaggregatog Activity 1
`
`Rat platelet-rich plasma was incubated with UT-lS at concentrations ranging from 5.1 to
`102.4 nM (2-40 ng/ml) for 1 minute at 37°C prior to the addition of ADP (10 pM). UT-15
`produced a concentration-dependent inhibition of ADP-induced platelet aggregation
`(Table l) with an IC50 of 34.6 nM (13.5 ng/ml)
`
`Table I.
`
`INHIBITION OF PIATEIET AGGREGATION 11mg IN RAT
`PLATELET—RICH PLASMA BY UT-ls
`
`Concentration
`
`7. Inhibition
`
`(EM)
`
`5.1
`
`10.2
`
`25.6
`
`51.2
`
`8 a: 5
`
`12 :h 5
`
`27 :h 8
`
`81 a: 3
`
`
`
`102.4 1005: 0
`
`Results, expressed as % inhibition of control aggregation, are mean i S.E.M. of 3 experiments.
`
`

`

`NDA 21-272
`
`,
`
`.
`
`'
`
`4
`
`In vitro studies using human platelet—rich plasma showed that UT-IS [2.56 to 256 nM (l-
`100 ng/ml]
`also caused a concentration-dependent
`inhibition of ADP-induced
`aggregation of human platelets, with an leo of 28.2 nM (ll ng/ml). It is stated that UT-
`15 was found to be 20-fold less potent than prostacyclin in inhibiting the ADP-induced
`aggregation of human platelets.
`
`2. Vascular Relaxation Effect
`
`UT-lS (1-1000 nM) produced a concentrationodependent relaxation of isolated rabbit
`mesenteric artery segments precontracted with the thromboxane mimetic U-46619 (1
`uM; Figure‘l ), the order of potency (when compared to other prostaglandins) being UT-
`15 > carbacyclin (a stable prostacyclin analogue) > l6-dimethyl PGE; > PGEz. In this
`study, UT-IS was found to be about 8 and 45 times more potent in inducing vascular
`relaxation than carbacyclin and PGE2, respectively.
`
`Figure l.
`
`azuxmori
`amam»
`
`Rel-amt actions 0:905; (o. n = 6), ISAUSI (o, n = 6). lG—dimethyl P6174,
`DmPGEim‘ns4),mAmrbmycan(a,n=5).’mmbbhmcmericm
`precontracted with IO‘M 046619. athromboxane mimic Results,
`
`expressed» Iamfimumplantions, aresbownasMeantSEM
`
`3. Agtiproliferative Effect in Human Pumonag Artery Smooth Muscle Cells
`
`UT-lS (30 nM for 48 hours) markedly reduced the proliferation of cultured human
`pulmonary
`smooth muscle cells, as measured by blinded cell counting (92%
`reduction) and [
`] thymidine incorporation (61% reduction). Moreover, it was shown
`that UT-IS produced a large elevation (about 120 fold) in intracellular cAMP, which was
`still elevated (about 6 fold) 72 hours after drug treatment. The above results indicate that
`UT-lS exerts its antiproliferative effect via a cAMP-dependent pathway in pulmonary
`artery smooth muscle cells.
`
`

`

`In Viva Studies Related to Proposed Indication
`
`1. Platelet Antiaggregatory Activig
`
`.
`
`Pentobarbitone anesthetized rats were given subcutaneous or oral administration of UT-
`15. Blood was collected 20, 40 or 60 min after dosing, centrifuged, and the platelet-rich
`plasma was used for ADP (10 um)-induced platelet aggregation studies. UT-lS at 100
`ug/kg, sc, caused signifith inhibition of platelet aggregation at both 20 and 40-minutes,
`while 25 ug/kg, sc, did not produce any significant inhibition of platelet aggregation
`(Table 2). When administered orally, UT-lS produced significant inhibition of ADP-
`induced platelet aggregation only at 5000 ug/kg (Table 3), but not at lower doses (25, 100
`or 1000 ug/kg; Tables 2 and 3.)
`
`(In the above study, UT-lS, at 25 and 100 pig/kg sc, reduced mean arterial blood pressure
`by 29 and 60 mmHg, respectively. Following oral administration, the mean arterial blood
`pressure was reduced by 35 and 55 mmHg at 1000 and 5000 [lg/kg doses, respectively.)
`
`Table 2. Inhibition of Platelet Aggregation Ex Vivo Following Subcutaneous or Oral Administration
`of UT—lS in the Rat
`'
`
`Dose
`
`(pg/kg)
`
`Route
`
`25
`
`100
`
`25
`
`100
`
`sc
`
`so
`
`so
`
`sc
`
`po.
`
`po.
`
`po.
`
`Time
`
`(min)
`
`20
`
`40
`
`20
`
`40
`
`20
`
`40
`
`20
`
`40
`
`% Inhibition
`
`714
`
`18 a: 6
`
`71 t 9 *”
`
`20:: l ‘
`
`6* 6
`
`l *2
`
`2 :h 6
`
`7 *3
`
`Results, shown as the % inhibition ofsub maximal ADP (10 Windueed
`platelet aggregation in rat plateletvrieh plasma prepared 9; iv; 20 and 40
`min after administration ofUT-lS, are mean :t: S.E.M. of3-4 experiments for
`each group. Statistically significant difl‘erenee fiom the control aggregation is
`shown by ‘P < 0.05; “‘P < 0.001.
`
`

`

`NDA 21-171
`
`I
`
`5
`
`6
`
`Table 3. Inhibition of Platelet Aggregation Ex Vivo Following Oral Administration of High Doses of
`UT-IS in the Rat
`
`M
`
`(
`
`1
`
`5
`
`'I'ime
`
`(min)
`
`20
`
`20
`
`'/- Inhibition
`
`‘
`
`27a 17
`
`58 a 8 m
`
`60
`
`53 a 23
`
`W R
`
`esults, shown as the % inhibition ofsubmaximal ADP (10 pM) -induced
`
`platelet aggregation in rat platelet-rich plasma, prepared ex vivo 20 or 60 min
`
`after oral administration of(IT-15, aremt S.E.M. of3-4 experiments for
`each group. Statisfieally-sigrfificant difi‘erence from the control aggregation is
`shown by ’P < 0.05; ”‘P < 0.001.
`
`In pentobar'bitone anesthetized rabbits, 10—minute iv infusions of UT-lS (50-500 ng/kg/
`min) also caused dose-related inhibition of ADP-induced platelet. aggregation.
`In these
`studies, the leo (dose causing 50% inhibition of platelet aggregation) for UT-IS was
`found to be 140 ng/kg/min, as compared to 200 ng/kg/min for prostacyclin. These
`antiaggregatory doses of UT-lS and prostacyclin produced reductions in mean blood
`pressure of 10 and 16 mmHg, respectively, indicating only minimal differences between
`these agents as inhibitors of platelet aggregation or vasodilators in this model.
`
`In an anesthetized open-chest dog model with stcnosed circumflex coronary arteries, UT-
`15 (300-1125 ng/kg/min iv infusion) was found to be 4.3-fold less potent
`than
`prostacyclin in preventing platelet thrombus formation and 7-fold less potent in lowering
`the mean arterial blood pressure.
`
`‘ 2. Vasodilator and Hemodynarnic Activity
`
`a. Anesthetized Animals
`
`In 'pentobarbitone-anesthetized rats, UT-IS produced significant dose-related reductions
`in mean arterial pressure (MAP) when administered by subcutaneous (29-60 mmHg at
`25—100 pig/kg) and oral (35—55 mmHg at 1-5 mg/kg) routes. Intravenous infiision of UT at
`0.4 ug/kg/min caused a reduction in MAP by 31 mmHg (Table 4). UT-IS was found to
`be about 10-fold less potent than prostacyclin as a hypotensive agent in this animal
`model.
`
`

`

`RDA 41-1/1
`
`Tune 4.
`
`I
`
`,
`
`HYPOTENSNE EFFECTS OF [IT-15 IN
`
`ANESTHETIZED ANIMALS
`
`Species
`
`Dose
`
`Route
`
`31’ Change
`
`(mm BE!
`
`1: .
`
`Rat
`
`25 pug/kg
`
`50 gig/kg
`
`100 uglkg
`
`0.4 pits/min
`
`I nag/kg
`
`5 nag/kg
`
`Rabbit
`
`0.05 pg/kg/min
`
`Cat
`
`Dog
`
`0.1 ug/kg’min
`
`0.2 ug/kg/min
`
`0.4 uykg/min
`
`0.5 ug/kglmin
`
`3 pg/kg/min
`
`10 pg/kg/min
`
`30 pg/kg/min
`0.32 ug/kg
`“mg/kg
`
`3.2 ug/kg
`
`0.1 pg/kg/min
`
`0.3 ug/kg/tnin
`’Eflfl''2
`
`ac
`
`ac
`
`3c
`
`iv.
`
`po.
`
`po.
`
`iv.
`
`iv.
`
`iv.
`
`iv.
`
`iv.
`
`iv.
`
`iv.
`
`iv.
`iv.
`iv.
`
`iv.
`
`iv.
`
`iv.
`iv.
`
`29:4
`
`36 t 3
`
`60 a: 5
`
`31
`
`35 t 7
`
`55 t 9
`
`' s t 3
`
`18:6
`
`28 i 9
`
`48 t 8
`
`54 :h 11
`
`22 i 8 (D)
`
`36 + 16 (D)
`
`‘74 t 9 (D)
`8 t 2
`14:2
`
`36 t 2.
`
`8 + 4
`
`27 :k 12
`63:12
`
`4
`
`4
`
`-5
`
`-
`
`6
`
`3
`
`3
`
`3
`
`3
`
`3
`
`3
`
`4
`
`4
`
`4
`5
`5
`
`5
`
`3
`
`3
`3
`
`RMmshownasthenducfioninmeansystemicMefialbloodpmmor
`
`diastolicbloodprssmm), cxpmsedasmemé 8.6M. All bloodprssune
`(8P) changu shown an statistically significant (P < 0.05).
`
`APPEARS nus WAY
`0N ORIGINAL
`
`

`

`NDA 21-1/2
`
`8
`
`In pentobarbitone—anesthetized rabbits, 10-minute iv infusions of UT-l 5 at 0.05 to 0.5 ug/
`kg/min produced dose-related reductions in MAP (8-54 mmHg; Table 4). In rabbits, there
`was very little difference in potency between UT-lS and prostacyclin as hypotensive
`agents.
`
`In chloralose-anesthetized cats (closed chest), iv infusion of UT-15.(3-30 ug/kg/min for
`20 min) also caused dose-related reductions in diastolic blood pressure (22-74 mmHg;
`Table 4) accompanied by non~dose related tachycardia (27-30 bpm). The maximum
`hypotensive and cardiac responses to UT-lS were evident within 5 minutes of infusion,
`and the values returned to baseline levels within 40 minutes of completing the infusion.
`No direct comparison of the potency of UT-lS with prostacyclin was done in this study.
`
`In chloralose and urethane mixture-anesthetized open-chest cats, iv infusions of UT-15
`(0.1-3.0 ug/kg/min for 20 minutes each) produced dose-dependent decreases in mean
`systemic arterial (6-42%) and mean pulmonary arterial (2-26%) blood pressures (Table
`5). UT-IS did not significantly affect heart rate or cardiac index. UT-15, at these dose
`levels, produced dose-dependent reductions in hypoxia-induced increments in pulmonary
`artery pressure (Figure 2) and pulmonary vascular resistance (Figure 3).
`In this study,
`UT-IS was about 3 and 10 times less potent than prostacyclin as a vasodilator under
`hypoxic and normoxic conditions, respectively.
`
`In anesthetized newborn piglets, UT-lS at 6 ug/kg (iv bolus) abolished hypoxia-induced
`increases in pulmonary vascular resistance.
`
`In pentobarbitone—anesthetized dogs, iv bolus injections (0.32-32 [Lg/kg) or 10 min iv
`infusions (0.1—1.0 ug/kg/min) of UT-lS produced significant dose-related reductions in
`MAP (Table 4). In animals that received the iv bolus injeCtion, there was a reduction in
`MAP of 8 to 36 mmHg, the duration of the hypotensive response varied from 30 seconds
`at the low dose to several minutes at the high dose. Ten-minute iv infusions of UT-lS
`caused dose-related reductions in MAP (8-62 mmHg) with signifith dose-related
`reductions in total peripheral resistance (0.2-1.4 units), and significant reduction in
`LVdP/dt (648 mmHg/ sec) at 1.0 ug/kg/rnin (Table 6). There were no significant heart
`' rate, cardiac index or EKG findings.
`
`Four hour iv infusions of UT-lS (0.1, 0.3, 1.0 and 3.0 ug/kg/min) in anesthetized dogs
`produced dose-dependent decreases in MAP (10-68%) and total peripheral resistance
`(TPR, 20-73%). Although decreases in pulmonary artery pressure (variable) and
`pulmonary vascular resistance (PVR, 9-33%) were noted, these effects were not dose-
`related (Figures 4 & 5). The vascular effects were rapid in onset, achieving maximum
`effect within 5-10 min of infusion with rapid recovery on termination of infusion.
`Although the effect on PVR was not dose-related, plasma sample analysis showed a close
`relationship between plasma concentrations of UT-IS and changes in TPR and PVR.
`(Pharmacodynamic modeling predicted maximum decreases in total peripheral resistance
`of 66% and pulmonary vascular resistance of 22%.) The plasma concentrations of UT-lS
`producing 50% of the maximum effect on systemic and pulmonary vascular resistances
`were 8.6 ng/ml and 11.3 ng/ml, respectively.
`
`

`

`NUA 21-272
`
`9
`
`In the above dog model, UT—15 produced dose—dependent decreases in left ventricular
`inotropic (+dP/dt) activity at 1 and 3 ug/kg/min doses, and significant dose-dependent
`decreases in left ventricular lusitropic (-dP/dt) activity at doses of 0.3 ug/kg/min and
`above. At 3.0 ug/kg/min, both +dP/dt and - dP/dt exhibited an apparent rebound above
`control values on termination of infusion. Significant decreases in lefi ventricular end
`diastolic pressure were noted at all dose levels (not dose—related). Cardiac output was
`significantly increased at 0.3 ug/kg/min and above and heart rate was increased at 0.3 and
`3.0 ug/kg/min (3%8%). UT-lS produced dose—dependent decreases in PR and QRS
`intervals with no significant effect on QTc.
`
`UT-15 infusions produced dose-related increases in plasma angiotensin 11 concentrations
`(50-263 pg/ml; Table 7) which correlated inversely with reduction of mean arterial blood
`pressure.
`
`Prostacyclin (PGIz), when given to anesthetized dogs for 4 hours at 0.01 to 0.3 ug/kg/
`min, produced vascular and cardiac effects similar to those produced by UT-15 (Figures 4
`& 5); however, P612 was found to be 10 times more potent than UT-IS in these studies.
`P612 infusions also caused dose-dependent
`increases
`in plasma angiotensin 11
`concentrations (Table 8).
`
`A separate study in anesthetized dogs showed that pretreatment with an angiotensin
`converting enzyme inhibitor, enalapril (0.3 mg/kg, iv), prevented the UT-lS-induced
`increases in plasma angiotensin 11 concentrations. Digoxin (100 mg/kg) pretreatment
`attenuated the ability of UT—15 to elevate plasma angiotensin II levels while pretreatment ‘
`with a loop diuretic (fiirosemide, 1.0 mg/kg) potentiated the increase in plasma
`angiotensin 11 concentrations induced by UT-15. Moreover, the results of this study
`suggest that pretreatment with enalapril, digoxin or furosemide may enhance the cardio-
`vascular efi‘ects of UT-15.
`
`APPEARS THIS WAY
`0N ORIGlNAL
`
`._ ~—>—-v——-,—»~.'_——.——.— m ,» -__u ‘—._-A .<...- V...
`
`----- ,.
`
`.,.
`
`_.,_
`
`7.“. e--,.. _, _ Weevmri... .
`
`.,.- ,
`
`. .-,. .. -
`
`

`

`”I”—7-URI7
`
`m
`
`Table 5. RESTING REMODYNAMIC VARIABLES BEFORE HYPOXIA IN
`
`DIFFERENT GROUPS OF ANESTHETIZED CATS
`
`SMAP
`
`HR
`
`C1
`
`SVR
`
`PAP M
`
`M -
`
`Inn-Hg
`
`um
`
`meln/kg mun min/kg
`
`nnHG
`
`mm]!
`
`mmHgIUMln/kg
`
`LIT-15. N - 5
`
`Dmauykwhh
`
` 15.3 t I
`
` 1298 :1: 146
`
`Contml
`
`
`
`1162 :1: 78
`0.3
`
`
`
`1072 :1: 68
`1.0
`880* 97
`
`
`11.3 t 1‘
`3.0
`
`0.1
`
`1271!: 147
`
`14.9 a: 1.3
`
`13.7:k 0.6
`
`122* 0.9'
`
`
`
`Glycine buffer. N - 5
`
`Infusion (0.1 mllmin) #
`
`
`Control
`1720!: 113
`
`1769* 158
`
`
`
`1971 #213
`
`1 2
`
`
`
`

`

`Table 5. RESTING HEMODYNAMIC VARIABLES BEFORE KYPOXLA IN DIFFERENT
`
`GROUPS or ANESTHETIZED cars (CONTINUED)
`
`“l- P"
`
`mllmlnnrg mmfluumlnlkg
`
`nm'
`
`..
`
`m
`
`mull
`
`lnllrg
`
`In!!!
`
` Time Control. N - 5
`
`
`
`Time Period ll
`
`66t7
` Control
`
` 1599*148
`133* 1.1
`
`
`74:1:7
`154* 1.4
`
`1415* 141
`
`
`61i6
`142:1.- 1.2
`1617*186
`
`
`64-k8
`163* 1.3
`1688* 147
`57*9"
`1627* 221
`15.7:t 1.7
`
`
`Asterisks indicate significant differences from corresponding control value. '1' < 0.01 . “P < 0.05. SMAP - Systemic
`
`Mean Arterial Pressure, HR - Heart Rate, Cl - Cardiac Index, SVR '- Systemle Vascular Resistance. PAP - Mean
`
`Pulmonary Arterial Pressure. PVP - Mean Pulmonary Venous Pressure, PVR - Pulmonary Vascular Resistance. Data
`
`represent resting values prior to the hypoxic challenges during control period and during each infusion. In time control
`
`experiments, data represent values prior to the hypoxic challenges before and at various times alter a bolus injection of
`saline.
`
`ZLZ‘IZVGN
`
`[1
`
`

`

`NDA 21-272
`
`12
`
`Figure 2.
`
`,
`
`
`
`
`
`no
`
`2 1203
`5 ’0
`i H
`
`' fl
`
`0
`
`I
`
`.
`
`J
`2
`nae-«H ”I
`
`6
`
`m of 15mm onthc gym hypofia-induoedm in pulmonary
`mnbloodpmnneGAP)(pandA).Alsosiwwnmtheefiectsofglydnc
`mmmmwhmmlmmlqmm
`(meaniSfiJueemmsedaspmof control hypoxic mponse.
`
`' P< 01135 V8. Control
`
`

`

`NDA 21-2 [2
`
`13
`
`0-1
`
`w
`0.3
`Don d 1931. Wu»
`
`3.:
`
`
`
`
`I
`
`3
`2
`Ila-mum.
`
`6
`
`310
`
`.—
`
`E i
`
`n»
`S
`
`a888
`
`EEectsoflSAUSl (pmlA),andglychebufier(panolB) onthesystanic
`hypozdnoinduoed hex-mot inpnlmonaryvnsuflarresisunce (PVR).
`Responsesinmoonnolexperhnms mshowninpanelQAnresuhs
`(mean: 8.5.) It: cxpressed as patent of control PVR (espouse.
`
`‘P < 0.02 vs control.
`
`

`

`NDA 21-272
`
`14
`
`Table 6.
`
`HEMODYNAMIC AND ELECTROCARDIOGRAM EFFECI'S OF
`
`INTRAVENOUS INFUSIONS 0F UT-IS IN THE ANESTHETIZED DOG (N 8 3)
`
`
`
` mmm
`
`Ton! Peripheral Resistance
`(pa'bhafl mime units)
`
`133 Vuu'icult End
`Diastolic Pressure (mm Hg)
`
`3.2 t 0.5
`
`-0.2 t 0.4 ‘
`
`-
`
`-o.7 1 0.6‘
`
`-l.4 * 0.5.
`
`4.2 at 1.0
`
`0.7 :k 0.8
`
`-0.9 t 1.3
`
`(ml/mini“)
`
`V
`
`LVdP/dl
`(unfit/sec)
`
`2339 i 404
`
`0.2 t 2.3
`
`448 t 39’
`
`
`
`
`
`
`
`
`
`
`
`
`
`----
`
`ST-Segmm Elation
`(mV)
`
`PR-m
`
`(1156:)
`
`QT.-imerval
`(Inset)
`
`-0.06 :t 0.07
`
`<0.02 * 0.02
`
`0.0 t 0.04
`
`104 i 2.3
`
`-3.3 i 2.9
`
`-
`
`-2.3 t 5.0
`
`321 i 7.7
`
`12.7 i 5.2
`
`10* 2.5
`
`-6.0:I= 2.1
`
`Data, shown asthcdmngefi'ompre-infixsion valuu foreachpmeteure
`fireman: 8.5M. Eachdosewasinfilsed for lOminutu. Wherethercis
`
`signifimt change fiom Inc-infusion value this is shown as *P < 0.05.
`
`

`

`.<u¢;. A -1-
`
`13
`
`FIGURE 4
`
`ISAUBI
`
`.
`: :3 ”fir/m
`p. glam
`A MAO/MIME»
`
`A
`
`n run-u. can"
`
`C
`
`I “'01 pv/iolm
`9 am “lug/m
`A van/“1......
`
`PSI;
`
`u an
`
`sun .
`N '
`
`-_...._......_........-
`«ooaonuouumawmm
`in“)
`
` 4n
`
`
`«ooautuuoannououo
`an...) .
`
`it. (ab)
`
`‘5'- ('5’
`
`

`

`lVUA 41" ll.
`
`5
`
`16
`
`FIGURE 5
`
`35mm
`
`P92,
`
`A
`
`I OJ nits/"-
`0 OJ gig/m ‘
`A la Anglia/Inn
`a A ”MAO/"‘50
`
`n um. sum- C
`
`I Ml who/M
`0 0.0) "Again
`A 0.! pong/min
`u ‘ 0'3 MIN/"'5“
`(end no.)
`
`0 or”... w...
`
`k: ‘5
`
`a!“ o
`
`a.
`
`so
`
`
`
`3
`a;
`3!
`fig
`ES -..
`2* «0
`
`I.
`
`#- -
`rm» 37%.
`‘¢~.-.I:’
`
`8
`
`U '
`
`°
`:3
`§.
`a;
`.
`fig
`I
`2 "°
`g; 4°
`
`a
`
`42.0 O 0 N In t” I” "0 no no
`Imhh)
`
`-9“ O
`
`‘0 fl "0' ‘" no I” unfi-
`luv-(uh)
`
`The percent change from control ofmean total pedpheral res'mance and
`
`mean pulmonary vascular_ resistance during and 60 minutes following
`infusions of 15mm. Panels A and B,respective1y, and POI; Panels c and
`13. may. in pentobarbital anesthetized dogs. Citrate 1nd glycine buffer
`
`an included as vehicle controls for 15AU81 and PGIz, respectively. Four
`
`animals per treatment With treatment per animal
`
`APPEARS THIS WAY
`V ,0” ORIGINAL
`
`M- .__.,-.,
`
`“WV" ....__, , mwgew ...
`
`

`

`1‘11“ Al'b IL
`
`Table 7.
`
`EFFECT or 0745 ON VENOUS PLASMA ANGIOTENSIN n
`conczmAnon mfimmcz BETWEEN maximum AND
`220 MINUTES or mslofi]
`
`I/
`
`v
`
`I
`
`
`
`
`
`
`
`
`
`
`
`
`0.3 11-4
`
`.
`
`68.05:!713
`
`3.0 (11-4)
`
`’263.45é79.!5
`
`37.45 a: 8.21
`
`Mm1smw<u05wdmtehmfiu
`
`Table 8.
`
`' ‘
`-
`EFFECT OF PGh 0N VENOUS PLASMA ANGIOTENSIN [I
`CONCENTRATION (remnamrmnmcz BETWEEN rmmmsmn AND
`220 mums or mslofl
`
`’
`
`
`
`
`
`
`
`w—
`n“
`
`Mean 1 SBM
`
`APPEARS THIS WAY
`ON ORIGINAL
`
`

`

`12-W ,
`
`In rats, oral administration of UT-lS at 1.5 and 5 mg/kg produced significant reductions
`in diastolic blood pressure of 13 and 28 mmHg, respectively (Table 9), with little effect
`on systolic blood pressure. These responses were seen within 10 min of dosing, and a full
`recovery was seen within 30-60 minutes. Heart rate was significantly increased (53-183
`bpm) at the above dosage levels. The heart rate effect was observed within 10 minutes of
`drug administration and lasted much longer than the blood pressure effect, up to 4 hours
`at the high dose.
`
`In spontaneously hypertensive rats, oral administration of UT-lS (0.1, 0.3, 1.0 and 3.0
`nag/kg) caused decreases in arterial blood pressure (14-18%) and increases in heart rates
`(20.25%) at 0.3 mg/kg and above. The hypotcnsive and tachycardiac effects lasted up to
`5 hours. There were no significant changes in the above parameters at 0.1 mg/kg.
`
`In dogs, the hypotensive effect of a 0.5 mg/kg po dose of UT-15 lasted up to 120 minutes
`post-dose, PR-interval was reduced at 30 min post-dose and QTc-interval increased at 120
`min post-dose (Table 10).
`
`Ten-minute iv infusions of UT-lS (0.3, 1.0 and 3.0 ug/kg/rnin) in dogs produced dose-
`related reductions of both systolic (18-40 mmHg) and diastolic (13-45 mmHg) blood
`pressures (Table 9) with increases in heart rates (13-30 bpm;
`information on dose
`relationship not provided). These effects were rapid in onset and a full recovery was
`evident within 5-10 minutes of termination of infusion.
`
`APPEARS; THIS WAY
`05-} {liflfiliéltl
`
`APPEARS THIS WAY
`0H ORIGINAL
`
`. _.-
`
`..- , _
`
`, -..- ”wan-.. _,.,, .-
`
`

`

`¢uu‘-4 A ‘1-
`
`Table 9.
`
`. HYPOTENSIVE EFFECTS OF UT-IS IN THE CONSCIOUS
`RAT OR DOG
`
`Species
`
`Dose
`
`Route
`
`BI’ Change I
`
`‘ Rat
`
`LS nag/kg
`
`‘ Sins/ks
`
`l Ins/kg
`
`5 Ins/kg
`
`Dog
`
`0.3 uglkg/min
`
`1 pg/kg/min
`
`3 pg/kg/min
`
`0.5 nag/kg
`
`1.5 mg/kg
`
`13.0
`
`po-
`
`po.
`
`po.
`
`iv.
`
`iv.
`
`iv.
`
`po.
`
`3'
`
`(am
`
`_
`
`13 t 2 (D)
`
`28:7 (D)
`
`10* 3
`
`19 1 3
`
`13 :k 3 (D)
`
`35 s: 6 (D)
`
`45 t 4 (D)
`
`31 (D)
`
`53 :I: ll
`
`n
`
`6
`
`6
`
`4
`
`4
`
`6
`
`6
`
`6
`
`6
`
`3
`
`Resultsmshdwnastbereducfioninmmsystanicmuidbloodpmmc
`
`«diastolicbloodpmsmemx cxprwedasmantSiMAllblood
`
`Manchmgsdwwnmmfisfimflysigfifimt0<0£$
`
`APPEARS THIS WAY
`0N ORIGINAL
`
`

`

`vcv’v-v
`
`n7
`
`7
`
`Table 10. HEMODYNAMIC AND ELECTROCARDIOGRAM EFFECTS OI" ORAL ADMINISTRATION
`OF [IT-IS (0.5 MGIKG) IN THE CONSCIOUS DOG (N - 6)
`‘
`7
`Q:%!"l Val-gag
`
`
`5 Min ‘ 30 Mill 60 MIII 90 Mm 120 MinI’m-Dose Values 140 Min
`
`
`
`
`
`
`
`
`
`
`
`149* 9
`
`m * 7.
`
`”out
`
`122 :k 1' mu“
`
`124* 5'
`
`147* s
`
`67H
`
`«*7.
`
`sum
`
`53*?
`
`57M.
`
`ssu
`
`7mg
`
`.
`
`78i8
`
`102*15
`
`10l£6
`
`100*”
`
`“*6
`
`79*5
`
`7H4
`
`Iona
`
`52*5
`
`..
`
`_
`
`90*?
`
`95*:
`
`sus
`
`55*6
`
`99‘s
`
`sus
`
`nous
`
`nos“,
`
`53:1
`
`sue
`
`mama;
`
`57"“‘23m5m’m
`Diastolic Blood Pressure
`(mmHs)
`
`Heartlhte
`(59m)
`
`W P
`
`R-Intewal
`(Mm)
`
`”Sm-4:23"!
`
`Dun. shown I! theme-and post-infinion valuuofuchpamnaet. refinements.EM. Manhunt: ulgnlficant
`difl'etmfiompre—dosewluoltismwnu‘l’<0.05.
`
`r...._..‘.<_=.*:0-.-.--....-.
`
`
`
`4_._—.—__..__....—.__._._.____..‘._.._________A-“.A_
`
`
`
`

`

`Safety Pharmacology Studies
`
`_
`
`.
`
`r
`
`l. Autonomic Nervous System (ANS): In anesthetized cats, iv infusion of UT-lS, at 3-30
`ug/kg/min for 20 minutes, had no effect on nictitating membrane contractions induced by I
`cervical sympathetic nerve stimulation, or on bradyeardia induced by vagal nerve
`stimulation, indicating that UT~15 had no effect on either the sympathetic or the parasym-
`pathetic systems of the ANS.
`
`2. Respiratory System: UT-lS (10-100 nM) produced weak contractile responses in
`guinea pig isolated tracheal segments. In precontracted guinea pig tracheal preparations,
`UT-lS (10”3-10'3 M) caused dose-related relaxation, with an EDso of 270 nM. In this
`study, UT-lS was found to be equipotent with P613; (ED50=220 nM) and about 400 times
`more potent than the stable prostacyclin analogue, carbacyclin (ED50=100 pM).
`
`In anesthetized cats, iv infusion of UT-lS (3-30 ug/kg/min for 20 minutes) had minimal
`effects on both respiratory rate and tidal volume except at the high dose, at' which
`increased respiratory rate (10-15 breaths/min) was seen.
`
`3. Gastrointestinal System: UT-15 exhibited weak contractile effects on isolated
`segments of guinea pig ileum, rat stomach or rat colon. When given orally, UT-IS
`inhibited GI motility and fluid secretion in the rat small intestine. In rats, the test drug
`inhibited the ulcer formation induced by indomethacin or ethanol. It is suggested that the
`anti-ulcer activity of UT-lS may be due to a cytoprotective rather than an antisecretary
`effect. In rats, pretreatment with a single dose of UT-lS (0.5 and 5 mg/kg, po) reduced
`the severity of carbon tetrachloride-induced hepatotoxicity. UT-lS (0.03-10 mg/kg, po)
`had no effect on pentabarbitone metabolism in rats, as measured by sleep duration,
`indicating a lack of its efi‘ect on liver enzyme function.
`
`4. Reproductive Sfitem: UT-15 had no significant effect on primate uterine motility g;
`
`5. Other Effects: In the mouse, UT-lS afforded little or no protection against the lethal
`effects of platelet activating factor.
`'
`
`APPEARS THIS WAY
`ON ORIGINAL
`
`

`

`SUMNIARY OF PHARMACOKINETIC STUDIES
`
`the
`Early pharmacokinetic and metabolism studies in dogs and rats (conducted at
`) were performed using [3H] UT-IS, in which the fate of total
`tritium was followed. Since this technique was found to be non-specific, a .' -—--.
`
`~
`capable of detecting UT-15 levels as low as t "1"" was later
`developed. The United Therapeutic Corporation, after licensing UT—lS from the
`GlaxoWellcome Co., developed a “highly specific and sensitive’ b——-—_—;——-
`
`assay method that was claimed to be capable of detecting
`of UT-lS/ml of plasma. This was the method employed for the
`levels as low as .......
`evaluation of the toxicokinetic study blood samples.
`
`Absomtion Studies
`
`Male and female Sprague-Dawley rats (6/sex) were administered a single oral or iv dose
`of 200 ug [3H] UT-lS/kg. After oral dosing, maximum plasma levels of total
`radioactivity were reached within 0.5-1.5 hr in males and 2-6 hr in females. The mean
`apparent oral bioavailability was determined to be about 46% (both sexes). Although the
`plasma clearance values were consistent between oral and iv dosings, there was an
`apparent gender difference. The plasma clearance of total [3H] was more rapid in males
`(441 ml/hr/kg) than in females (274 ml/hr/kg). The distribution half-life after iv dosing
`was 0.8 hr (both sexes) and the elimination half-lives were 10—14 hr after iv and 4-7 hr
`after oral administration. The elimination half-life was shorter in males (4-10 hr) than in
`females (7-14 hr).
`
`Following a single oral dose of 5 mg [3H] UT-lS/kg in Sprague-Dawley rats (3/sex),
`maximum plasma levels of total radioactivity were reached at 0.75 and 2 hr post-dose in
`males and females, respectively. The mean apparent bioavailability was determined to be
`31%, indicating that the oral bioavailability might decrease with increasing dose. The
`mean plasma clearance values were 440 ml/hr/kg for males and 276 ml/hr/kg for females.
`The distribution half-lives of radioactivity were 3.5 and 2.1 hr for males and females,
`respectively. The elimination half-lives could not be estimated because of .possible
`enterohepatic recirculation.
`
`In anesthetized normotensive beagle dogs (2/sex/group) given 4 hr iv infusions of UT-15
`at 0, 0.1, 0.3, 1.0 or 3.0 ug/kg/min, plasma concentrations of UT~15 (determined lay—#7
`increased rapidly and reached steady-state levels within 10-15 min fi'om the onset of
`infusion at all infusion rates. Pharmacokinetic analysis of the data indicated a biphasic
`decay of UT-15 in plasma 'with an initial half-life of about 2 min and a terminal half-life
`of about 20 min. Concen-tration-effect vs time plot indicated a close relationship between
`plasma drug concen-tration and the onset of hemodynamic effects [decreases in total
`peripheral resistance (TPR) and pulmonary vascular resistance (PVR)]. In general,
`decreases in TPR were maintained during all but the 0.3 ug/kg/min infusions (Figure 6),
`while decreases in PVR were maintained only at the two highest dose levels (1.0 and 3.0
`ug/kg/min; Figure 7). Because plasma concentrations of UT-15 did not decrease during
`
`

`

`A‘un 1-1 LIA:
`
`1..)
`
`any infusions, it is suggested that some tachyphylaxis may have occurred for TPR at the
`0.3 ug/kg/min infusion, and for PVR at the 0.1 and 0.3 ug/kg/min infusions.
`
`Upon termination of the infusion, although plasma drug concentrations dropped close to
`zero levels, the effects on TPR still persisted for about 60 minutes at 1 and 3 ug/kg/min
`infusion levels (Figure 6). This hysteresis was more readily observed when the mean
`effect was plotted against the mean concentration of drug at each infusion rate, and points
`were linked in temporal sequence (Figure 8). The hysteresis is attributed to a delay in the
`clearance of drug from the active site compared to its clearance from the plasma, and/or
`due to the presence of active metabolite at the active site. There was no clear hysteresisin
`the efiect of UT—l 5 on PVR.
`
`When the concentration-effect data were fitted to the Erm pharmacodynamic model, it
`was predicted that the maximum decreasein TPR achievable with UT-15in anesthetized
`dogs was 66%, and the concentration of UT-15 producing 50% of the maximum effect
`(BCso) was 8.6 ng/ml. Similarly, the predicted maximum reductionin PVR was 22% and
`the BCso was estimated to be 11.3 ng/ml. While the magnitude of the effect of UT~15 on
`TPR and PVR may be difi'erent, the above model suggested that there might be little or
`no selectivity of UT-lS for the pulmonary or peripheral circulation in the normotensive,
`anesthetized dog.
`
`In a separate, nonrandomized crossover study, three anesthetized beagle dogs were given
`bolus doses of UT-15 orally (200 [Lg/kg), intravenously (20 ug/kg), or intratracheally (20
`tig/kg) with or without 13be (a synthetic surfactant used clinically for the treatment of
`neonatal and adult respiratory distress syndrome), treatments separated by at least one
`week. Intratracheal administration with or without Exosurf produced mean peak plasma
`concentrations of 11.9 ng/ml and 12.5 ng/ml at 7 min post~dose, with mean bio-
`availability values of 46 and 88%, respectively. When administered orally, the mean peak
`plasma concentration of 96.6 ng/ml was obtained 45 min after dosing, and the mean
`bioavailability was 62%. Afier iv administration, the highest concentration (85.7 ng/ml)
`was seen in the first sample (taken 2 min post-dose). The half-life of UT-15 afier iv
`dosing was determined to be 2.8 minutes.
`
`[The results Of the above study indicate that intratracheal or oral dosing can provide an
`alternate means of systemic delivery of UT-15. However, bioavailability data showed
`high variability]
`
`In a two-week continuous iv infusion study in dogs (3/sex/group; infusion rates at 0, 0.05,
`0.1 or 0.2 ug/kg/min), infusion-phase plasma drug concentrations were below the limit of
`quantitation at \
`......—-———-'—MW“
`H There was no quantifiable amount present in postoinfusion samples. The
`results indicated that the plasma concentrations were linearly related to the dose.
`
`Pharmacokinetic data obtained fiom all the above studies are summarized in Table l 1.
`
`

`

`
`
`_._..,L..._L_,—~.—M.«.'.
`
`¢-.-¢-.......
`
`"’8 VS 15M”! PLASKM CONCEN‘I’MTION
`WANDAIA
`'
`-M'W|
`
`0.1%
`
`‘m‘
`
`2 z:
`82
`2=- 5 ~
`0
`V o g
`. o
`
`0 9101$M2503N
`wank!)
`
`
`
`
`OWIW'MMMW
`
`»
`
`osotnouozoomzm
`
`the (rub)
`m (uh)
`Figure 6. Graphs at mean puma communion; o! tSAUOI and mean (bulges In (on! peduncle! «mum "PM vs. lime. when ISAUM
`was inland at o. i. 0.3, to. and 3.0 10km Io annualized dogs.
`-
`
`
`
`IrI9_Y-vlynxv
`
`{,7
`
`

`

`.Li....
`.-..q
`
`
`
`..1...;.___.‘._.--.
`
`__..--.-..-;-._._
`
`PW! VS 05M!” PLRSMA CONCENTRATION
`MEAN DAIA
`om 'MWI
`oxam‘mwn
`
`
`
`
`
`
`40 h-Ouw‘
`8 mum
`
`0
`
`on
`
`too 050 too 250 no
`mum)
`03W!“
`
`u.......-Q.—...-—‘_.
`50 UN ‘50 m 35.
`
`0
`
`son
`
`m (min)
`
`Figure 7,
`
`. Guphs oil me