European Journal of Clinical Investigation (2006) 36 (Suppl. 3), 32–38
`
`Blackwell Publishing LtdFirst experience with an oral combination therapy using
`bosentan and sildenafil for pulmonary arterial hypertension
`
`K. Lunze*, N. Gilbert*, S. Mebus*, O. Miera*, W. Fehske†, F. Uhlemann‡, E. G. Mühler §, P. Ewert*,
`P. E. Lange*, F. Berger* and I. Schulze-Neick*
`*Klinik für angeborene Herzfehler/Kinderkardiologie, Deutsches Herzzentrum Berlin, Berlin, †Abteilung Kardiologie/Innere
`Medizin, St. Vincent-Hospital, Köln, ‡Abteilung Kinderkardiologie, Olga-Hospital, Stuttgart, §Abteilung für Pädiatrische
`Kardiologie, Universitätsklinikum Aachen, Aachen, Germany
`
`Abstract
`
`Background New oral substances such as beraprost, bosentan and sildenafil have proven
`effective in different forms of pulmonary arterial hypertension (PAH), both alone and
`in combination with standard treatment such as intravenous and inhaled prostacyclins.
`However, there are few reports so far on the effect of a combination of exclusively oral
`substances. In this paper, we present our initial findings of treatment using a combination
`of these oral substances in a heterogeneous group of patients with different forms of PAH.
`
`Materials and methods Eleven patients with a median age of 12·9 years (5·5–54·7 years)
`with both idiopathic PAH and forms associated with congenital cardiac defects (PAH-CHD)
`with a mean pulmonary arterial pressure > 25 mmHg were enrolled in an observational,
`open-label, prospective, single-centre study. Either combination treatment with bosentan and
`sildenafil was started initially, or an existing bosentan treatment was complemented with
`sildenafil given as an add-on therapy. Mean doses given were 2·3 ± 0·6 mg kg−1 for bosentan
`and 2·1 ± 0·9 mg kg−1 for sildenafil. Clinical status, exercise capacity, and haemodynamics
`were assessed at baseline and at the end of the observation period after a mean follow-up
`time of 1·1 years (0·5–2·5 years).
`
`Results No major side effects regarding liver function and blood pressure regulation were
`noted. One patient died of sudden death elsewhere. Most patients were in New York Heart
`Association (NYHA) functional class III. Clinical improvement was about one NYHA class
`(mean 2·8 ± 0·4–1·6 ± 0·8, P = 0·001), which was associated with an increase of
`transcutaneous oxygen saturation (89·9 ± 9·9–92·3 ± 7·1%; P = 0·037), maximum oxygen
`uptake (18·1 ± 6·8–22·8 ± 10·4 mL kg−1 * min; P = 0·043), and 6-minute walking distance
`(351 ± 58–451 ± 119 m; P = 0·039). Mean pulmonary arterial pressure measured invasively
`decreased (62 ± 12–46 ± 18 mmHg; P = 0·041).
`Conclusions In our patient group, a combination of oral bosentan and sildenafil proved to
`be safe and effective. Clearly, randomized, double-blind, placebo-controlled studies are
`warranted to define the role and type of combination therapies in PAH.
`
`Keywords Bosentan, combination, endothelin receptor antagonists, phosphodiesterase
`inhibitors, pulmonary arterial hypertension, sildenafil, congenital heart disease, children,
`competence network.
`Eur J Clin Invest 2006; 36 (Suppl. 3): 32–38
`
`Klinik für angeborene Herzfehler/Kinderkardiologie, Deutsches Herzzentrum Berlin, Berlin (K. Lunze, N. Gilbert, S. Mebus, O. Miera,
`P. Ewert, P.E. Lange, F. Berger, I. Schulze-Neick); Abteilung Kardiologie/Innere Medizin, St. Vincent-Hospital, Köln (W. Fehske);
`Abteilung Kinderkardiologie, Olga-Hospital, Stuttgart (F. Uhlemann); Abteilung für Pädiatrische Kardiologie, Universitätsklinikum
`Aachen, Aachen (E. G. Mühler), Germany.
`
`Correspondence to: PD Dr Ingram Schulze-Neick, Klinik für Angeborene Herzfehler/Kinderkardiologie, Deutsches Herzzentrum Berlin,
`Augustenburger Platz 1, 13353 Berlin, Germany. Tel.: +49 (0)30 4593 2800; fax: +49 (0)30 4593 2900; e-mail: schulze-neick@dhzb.de
`
`Received 14 December 2005; accepted 31 May 2006
`
`© 2006 The Authors
`Journal compilation © 2006 Blackwell Publishing Ltd
`
`UNITED THERAPEUTICS CORP., EX1014, page 1
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
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`Introduction
`
`Idiopathic pulmonary arterial hypertension (iPAH) is a dev-
`astating disease with a poor prognosis. Without appropriate
`therapy, median life expectancy at the time of diagnosis
`is only about 2·8 years and 3-year survival only 48% [1].
`With maximal medical therapy of continuous intravenous
`administration of prostanoids, 3-year survival has been con-
`firmed in several independent studies as no more than 63%
`[2,3]. Indication for lung transplantation or heart-lung
`transplantation is given in patients who are refractive to
`medical treatment. Transplantation poses severe restrictions
`to patients’ quality of life. Three-year survival even after lung
`transplantation is only about 55% [4,5].
`Current medical treatment following international guide-
`lines [6,7] is based on oral anticoagulation, diuretics,
`calcium channel blockers, and supplemental oxygen, where
`applicable. Furthermore, it includes vasoactive agents from
`the prostaglandin, nitric oxide and endothelin pathways.
`Synthetic prostacyclins are a substitute for the relative
`endogenous prostacyclin deficiency in iPAH patients.
`They can be administered intravenously (epoprostenol),
`subcutaneously (treprostinil), inhaled (iloprost) or orally
`(beraprost). Continuous intravenous therapy with prosta-
`noids has beneficial effects on haemodynamics and exercise
`capacity and is the only treatment proven in controlled clin-
`ical trials to improve survival time in patients with iPAH
`[8,9]. However, it is expensive and may be complicated by
`line infections, tachyphylaxis, and systemic side effects due
`to lack of pulmonary selectivity. Patients suffering from
`complications due to intravenous application of prostanoids
`may be switched to continuous subcutaneous trepostinil;
`however, large trials have shown only a modest increase
`in exercise capacity and a high incidence of therapeutic
`limitations due to local pain at the site of infusion [10].
`Inhalation therapy showed improvement of clinical and
`haemodynamic parameters [11], but the need for regular
`short-term repetitive inhalations represents a major incon-
`venience for patients. In addition, long-term therapy with
`iloprost has shown disappointing results [12]. Oral therapy
`is most practical but seems to lack an improvement beyond
`a time of 6 months [13,14].
`Phosphodiesterase-5 (PDE5) inhibitors enhance endo-
`genous and exogenous effects of nitric oxide (NO) via
`inactivation of cyclic adenosine monophosphate and cyclic
`guanosine monophosphate, the NO second messengers.
`Evidence shows improvement in clinical and haemody-
`namic parameters for oral sildenafil [15,16]. It promotes
`pulmonary vasodilatation in children [17]. A recent con-
`trolled trial with sildenafil supported previous findings,
`showing improvement in the 6-minute walk test (6-MWT),
`NYHA functional class and decrease in pulmonary artery
`pressure [18]. Oral vardenafil and tadalafil have markedly
`different haemodynamic and oxygenation responses [19].
`Endothelin receptor antagonists (ERAs) block one or
`both endothelin receptors, thus preventing them from
`exerting their vasoconstrictor and pro-inflammatory effects.
`Controlled trials in iPAH patients with the dual oral ERA
`bosentan demonstrated improvement in exercise capacity,
`
`Oral combination therapy for PAH
`
`33
`
`functional class, and time to clinical worsening [20] as well
`as haemodynamic and echocardiographic parameters [21].
`The effects of bosentan are maintained in the long term
`[22], and patients’ quality of life is improved [22–24]. The
`selective orally active ERAs sitaxsentan [25] and ambrisentan
`[26] have been evaluated in pilot studies and have shown
`dose-dependent improvements in exercise capacity, haemo-
`dynamics and clinical events.
`It is clear that the combination of different drugs with
`different mechanisms of action and different ways of meta-
`bolism is an attractive therapeutic option with the hope of
`maximizing effectiveness and mode of drug delivery while
`minimizing side effects. Furthermore, the overall aim of any
`oral or inhaled therapy will strive to prevent patients from
`being submitted to a continuous intravenous administration
`of prostanoids or lung transplantation with its poor outcome
`and severe limitations for our patients’ quality of life. In this
`study, we used a combination of oral substances in order
`to take advantage of the mode of application and present
`our findings on the combination treatment of bosentan and
`sildenafil in terms of clinical efficacy and safety.
`
`Patients and methods
`
`Patients
`
`Pulmonary arterial hypertension was conventionally
`defined as a mean pulmonary arterial pressure greater than
`25 mmHg. At the time of enrolment, all patients were in
`clinically stable conditions, according to New York Heart
`Association (NYHA) functional class II or III, with no new
`medication started within the previous 3 months. The study
`was conducted to the provisions of the Declaration of
`Helsinki of 1975, as revised in 1983, and in adherence
`to local guidelines for Good Clinical Practice. Informed
`consent was obtained from all patients.
`
`Study design and treatment
`
`This was an observational, open-label, prospective single-
`centre study. Baseline data were obtained including clinical
`examination, echocardiography, cardiopulmonary exercise
`testing on the treadmill, the 6-MWT, and echocardio-
`−
`1
`graphy. Bosentan dosage was 0·75 mg kg
` twice daily for
`the first 4 weeks and then doubled, corresponding to the
`−
`×
`1
`standard adult dose of 2
` 125 mg d
`. Sildenafil dosage was
`−
`1
`0·5 mg kg
` three to four times per day. Both drug regimens
`were to be individually adjusted if necessary to limit side
`effects such as impairment of liver function (bosentan) or
`vision disturbances (sildenafil), respectively.
`
`Clinical assessment and laboratory values
`
`Patients had an extensive diagnostic work-up to define the
`type and severity of PAH, including clinical examination
`
`© 2006 The Authors
`Journal compilation © 2006 Blackwell Publishing Ltd,
`
`European Journal of Clinical Investigation
`
`,
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`36 (Suppl. 3), 32–38
`
`UNITED THERAPEUTICS CORP., EX1014, page 2
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
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`34
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`K. Lunze
`
`et al.
`
`with NYHA classification, measurement of transcutaneous
`oxygen saturation and heart rate. All patients had standard
`laboratory tests on haematology, chemistry and liver
`enzymes before the start of combination therapy and then
`at monthly intervals.
`
`Echocardiography
`
`Right and left ventricular function was assessed by measur-
`ing the echocardiographic end-systolic and end-diastolic
`areas in the apical four-chamber view with calculation of
`ejection fraction. The maximal tricuspid and pulmonary
`regurgitant jet velocity was measured by determining the
`peak regurgitant velocity in the continuous-wave Doppler
`flow profile obtained from the cardiac apex and expressed
`as gradients in mmHg without correction for (unknown)
`central venous pressure.
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`in Eisenmenger
`echocardiographic measurements, or
`patients with unrestricted transmission of systemic pressures
`to the pulmonary circulation.
`
`Statistical analysis
`
`Data compared consisted of those obtained before bosentan
`treatment (baseline), and those obtained after at least
`six months of treatment (end of observation). All values are
`±
`presented as mean
` standard deviation. The effect of the
`bosentan treatment was evaluated using only pairs of values
`in each patient (baseline value, end of observation value)
`t
`P
`for the two-tailed, paired
`-test. A
`-value < 0·05 was
`considered to be statistically significant.
`
`Results
`
`Exercise tolerance
`
`Patients and length of follow-up
`
`In the adult patients, exercise capacity was evaluated with
`the unencouraged 6-MWT. In those patients older than
`6 years, complementary cardiopulmonary exercise testing
`was performed and consisted of a bicycle or treadmill ramp
`protocol with a resting period, an exercise load which was
`−
`1
`increased by 15 Watt min
`, and was continued until exhaus-
`tion in both surgically corrected and Eisenmenger patients,
`tolerating marked transcutaneously measured desaturations
`in the latter group. For monitoring, cardiopulmonary meas-
`urements were continued during recovery and until return
`of all parameters to baseline. Maximum exercise para-
`meters were determined as the last 15-second average, and
`submaximum exercise parameters (slope of min ventilation
`−
`1
`Vco2
`(V
`; L min
`) versus carbon dioxide production (
`;
`E
`−
`1
`L min
`) were calculated by using the entire data set during
`exercise.
`
`Eleven consecutive patients were enrolled. Patient median
`age was 12·9 years (range 5·5–54·7 years). Origin of PAH
`n
`was: idiopathic (
` = 4), secondary to congenital heart
`
`
`disease (ventricular septal defect, n = 2; complete endocardial
`
`n = 1; aortopulmonary window,
`
`n = 1),
`cushion defect,
`
`
`chronic pulmonary thrombembolism (CTEPH; n = 1), and
`±
`
`n = 1). Mean doses given were 2·30
`radiotherapy (
` 0·6
`−
`−
`±
`1
`1
`mg kg
` for bosentan and 2·1
` 0·9 mg kg
` for sildenafil.
`Concomitant medication
`included phenprocoumon,
`amlodipine, acetyl salicylic acid, captopril, spironolactone,
`furosemide, digoxin, clopidogrel, hydrochlorothiazide/
`triamteren, and hydroxyurea. Mean follow-up time was
`1·1 years (range 0·5–2·5 years). No major side effects were
`noted. Specifically, liver function tests and blood pressure
`remained within normal limits. One patient died of sudden
`death elsewhere (Table 1, Pat. 3).
`
`Cardiac catheterization
`
`Haemodynamic assessment of pulmonary vascular pres-
`sures was performed either as an initial diagnostic procedure
`or in patients where the risk of cardiac catheterization
`deemed acceptable; it was done by right heart catheterization
`including pharmacological testing for pulmonary vascular
`responder status using inhaled oxygen together with
`inhaled NO and nebulized iloprost. In patients with
`corrected heart disease, cardiac output was measured using
`conventional thermodilution, and pulmonary vascular
`resistance was calculated using standard formulas. In
`patients with the Eisenmenger syndrome, pulmonary
`vascular resistance was either expressed as a relation to
`systemic vascular resistance (Rp : Rs), or it was calculated
`on the basis of the Fick principle using measured resting
`oxygen consumption. Invasive follow-up was not performed
`in patients with post-operative persisting PAH when a clear
`tricuspid regurgitation
`jet allowed
`for satisfactory
`
`Clinical status, exercise tolerance and haemodynamic
`parameters
`
`Most patients were in NYHA functional class III. Clinical
`±
`improvement was about one NYHA class (mean 2·8
`±
`
`P = 0·001), which was associated with an
`0·4–1·6
`0·8,
`±
`increase of transcutaneous oxygen saturation (89·9
`±
`
`P = 0·037), maximum oxygen uptake
`9·9–92·3
`7·1%;
`−
`±
`±
`1
`P
`(18·1
` 6·8–22·8
`10·4 mL kg
` = 0·043), and
` * min;
`±
`±
`
`P =
` 58–451
` 119 m;
`6-minute walking distance (351
`0·039). Mean pulmonary arterial pressure measured
`±
`±
`
`P = 0·041),
`invasively decreased (62
` 12–46
` 18 mmHg;
`and resting heart rate normalized from a mean of
`±
`±
`
`
`12 beats per min (P = 0·034). Right
`94·7
` 14·4–84·5
`ventricular systolic pressure tended to decline under treat-
`±
`ment both measured by echocardiography (from 86
` 31·4
`±
`P
`32·0 mmHg;
` = 0·054) and measured invasively
`to 71
`±
`±
` 17·2–80
` 19·9 mmHg;
`by cardiac catheterization (101
`
`P = 0·088).
`
`Journal compilation © 2006 Blackwell Publishing Ltd,
`
`European Journal of Clinical Investigation
`
`© 2006 The Authors
`
`36 (Suppl. 3), 32–38
`,
`
`UNITED THERAPEUTICS CORP., EX1014, page 3
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
`
`

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`Oral combination therapy for PAH
`
`35
`
`Table 1 Patient data and medication
`
`Patient
`
`Cause of PAH
`
`age/years
`
`kg
`
`treatment/years
`
`Sildenafil/kg
`
`Bosentan/kg
`
`CHD1
`CHD2
`idiopathic
`idiopathic
`CHD3
`CHD3
`post-radiogenic
`CHD4
`CTEPH
`idiopathic
`idiopathic
`
`1
`5·5
`18·4
`1·5
`1·6
`1·6
`2
`6·0
`18·0
`1·5
`4·2
`2·2
`3
`6·0
`20·7
`0·4
`1·8
`3
`4
`6·4
`27·0
`0·5
`2·8
`2·3
`5
`7·1
`22·4
`2·5
`1·8
`2·8
`6
`12·9
`30·0
`1·0
`2·5
`3·1
`7
`14·1
`27·1
`0·5
`2·8
`2·3
`8
`17·5
`47·5
`0·4
`0·9
`1·3
`9
`24·0
`110·7
`1·8
`2·5
`2·3
`10
`44·3
`78·0
`1·4
`1·6
`1·6
`11
`54·7
`80·0
`0·5
`0·9
`3·1
`Mean
`18·1
`43·6
`1·1
`2·1
`2·3
`Median
`12·9
`27·1
`1·0
`1·8
`2·3
`Diagnoses, body weight and doses given for 11 patients. Values are presented as means ± SD, medians and ranges. CHD1–4 = multiple
`VSD, atrioventricular septal defect, single VSD, and aortopulmonary window, respectively; CTEPH, chronic thrombembolic arterial
`hypertension; Concomitant medication included digoxine (Pat. 1), acetyl salicyle acide (Pat. 2,8), captopril, spironolactone, furosomide
`(Pat. 2), amlodipine (Pat. 4), phenprocoumon (Pat. 7,9), clopidogrel, hydrochlorothiazide/triamteren (Pat. 10) and hydroxyurea
`(Pat. 11). PAH, pulmonary arterial hypertension; BW, body weight.
`
`Figure 1 Improvement of clinical status (New York Heart
`Association class) in 11 patients in response to combination
`therapy. Values are given as per cent of total patient number, and
`the different grey shades refer to the different NYHA classes.
`
`Discussion
`
`In a cohort of 11 children and adults with pulmonary
`arterial hypertension of different origins, we observed an
`improvement in clinical status, exercise capacity, and
`haemodynamics in response to a combination treatment of
`oral bosentan and sildenafil. These findings suggest that this
`combination therapy is safe and may be effective in different
`forms of PAH.
`None of our patients was in a NYHA class IV or requiring
`intravenous prostanoids or a more intensive treatment.
`However, while in our adult patients, the combination of
`
`Figure 2 Improvement of six-minute walking distance at the
`beginning and at the end of the observation period with bosentan/
`sildenafil combination treatment in eight patients.
`
`agents had the aim to provide a most effective treatment
`for NYHA class III symptoms, in the children with milder
`symptoms, the intention was more focused on the preven-
`tion of further progression of the disease. So, at the time
`when our patients presented, bosentan was the only oral
`treatment approved for pulmonary arterial hypertension,
`which includes, by definition, idiopathic PAH together with
`PAH due to congenital heart disease. Recently, we have
`shown that bosentan is safe and is of clinical benefit in both
`children and adult patients with congenital heart disease.
`Sildenafil was chosen as the other oral drug because of
`its proven efficacy profile in different types of PAH – post-
`operative in children, chronic idiopathic and congenital
`heart disease related in children and adults – which has actu-
`ally led to its recent approval for the treatment of PAH as
`well. Furthermore, there are also the practical advantages
`of oral drugs: they avoid the danger of line infections and
`
`© 2006 The Authors
`Journal compilation © 2006 Blackwell Publishing Ltd,
`
`European Journal of Clinical Investigation
`
`,
`
`
`
`36 (Suppl. 3), 32–38
`
`UNITED THERAPEUTICS CORP., EX1014, page 4
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
`
`

`

`Clinical status
`SatO2 in percentage
`HR per min
`NYHA class
`Exercise capacity
`VO2 max in ml/kg * min 10 18·1 ± 6·8
`8 351 ± 58
`6-MWT in m
`Echo
`RVSP in mmHg
`Invasive testing
`RVSP in mmHg
`mPAP in mmHg
`
`9
`
` 86 ± 31
`
`9 101 ± 17
` 62 ± 12
`9
`
`22·8 ± 10·4 0·043
` 451 ± 119
`0·039
`
` 71 ± 32
`
`0·054
`
` 80 ± 20
` 46 ± 18
`
`0·088
`0·041
`
`36 K. Lunze et al.
`
`Table 2 Results of bosentan/sildenafil combination treatment
`
`Before
`treatment
`
`End of
`observation P-value
`
`n
`
`
`
`92·3 ± 7·1
`11 89·9 ± 9·9
`0·037
`11 94·7 ± 14·4 84·5 ± 12·0 0·034
`2·8 ± 0·4
`1·6 ± 0·8
`11
`0·001
`
`Figure 3 Improvement of mean arterial pulmonary pressure at
`the beginning and at the end of the observation period with
`bosentan/sildenafil combination treatment in nine patients.
`
`Figure 4 Improvement of maximal oxygen uptake at the beginning
`and at the end of the observation period with bosentan/sildenafil
`combination treatment in 10 patients.
`
`rebound PAH associated with the intravenous continuous
`administration of prostanoids as well as the aversion or
`depression with which some patients react to the more
`impractical repeated inhalations of iloprost. These consid-
`erations appear to be especially valid in paediatric patients.
`Finally, the economical aspects are not without impact and
`have been highlighted before [27]. Depending on the exact
`doses applied and its effect, oral combination treatment
`costs approximately 75% of a treatment with inhaled iloprost
`and 33–20% of a treatment with intravenous prostanoids,
`respectively.
`Our considerations for combination treatment were
`different from the recently reported concept of step-by-step,
`goal-oriented therapy described by Hoeper [28]. In that
`paper, a therapeutic goal (6-MWT > 380 m, VO2max
`> 10·4 mL kg−1 * min, and maximum systolic pressure
`during exercise > 120 mmHg) was set to be achieved by a
`stepwise crescendo of new therapeutic options (bosentan,
`sildenafil, inhaled and intravenous iloprost). This crescendo-
`like therapeutic approach is based on the same logic as the
`treatment of systemic arterial hypertension with a pre-
`defined systemic blood pressure level being the therapeutic
`goal. However, although an improved survival was demon-
`strated for patients compared with ‘historical’ patients
`treated without this approach and the new agents, this study
`
`Clinical status, exercise capacity, and haemodynamic values
`before the start of the treatment and at the end of the combination
`period, during which therapy with bosentan and sildenafil was given
`as indicated in Table 1. Values are presented as means ± SD. SatO2,
`transcutaneous oxygen saturation; HR, heart rate; NYHA-class,
`clinical state according to the classification of the New York Heart
`Association; VO2max, maximum oxygen uptake; 6-MWT, 6-
`minute walking test; RVSP, right ventricular systolic pressure;
`mPAP, mean pulmonary arterial pressure.
`
`does not provide an insight as to which of the new drugs
`is more effective and whether any combination is more
`effective than any one drug alone.
`However, there is multiple evidence that there is a justi-
`fied ‘rescue’ role for a combination therapy in PAH: patients
`with iPAH who were on bosentan treatment with insuffi-
`cient clinical results experienced a marked and sustained
`improvement when sildenafil was added to the treatment
`[27]. The same benefit from additional sildenafil was shown
`acutely and chronically in patients who were on chronic
`iloprost inhalation [29–31], and seems to be valid also
`for the combination with other prostanoids (intravenous
`epoprostenol [32–35], oral beraprost [36]).
`In our study, we combined these two oral agents, bosen-
`tan and sildenafil, aiming at a targeted treatment effect on
`PAH while minimizing the side effects by using different
`intracellular modes of action. Sildenafil inhibits CYP3A4
`activity and thus leads to an increased bosentan plasma
`concentration [37]. It is unknown whether this additionally
`increases the potential of bosentan to cause liver damage.
`We did not observe increased transaminases levels in our
`patients. This corresponds to the findings of an extensive
`bosentan post-marketing surveillance in about 5000 patients,
`in which the rate and pattern of potential safety signals, spe-
`cifically aminotransferase elevations in a combination therapy
`bosentan and sildenafil (n = 213) was not substantially
`different from patients on bosentan who were not taking
`sildenafil [38]. On the other hand, sildenafil peak plasma
`level and area under the curve after the administration of a
`single dose of 100 mg oral sildenafil is reduced to a third in
`the presence of chronic bosentan treatment and subsequent
`activation of the hepatic CYP3A4 [37], so that a three-fold
`
`© 2006 The Authors
`Journal compilation © 2006 Blackwell Publishing Ltd, European Journal of Clinical Investigation, 36 (Suppl. 3), 32–38
`
`UNITED THERAPEUTICS CORP., EX1014, page 5
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
`
`

`

`sildenafil dose might be justified in chronic bosentan patients.
`Conversely, in another study in healthy volunteers, sildenafil
`three times daily increased bosentan plasma levels by 50%
`[39]. Clearly, more data are needed in this area to provide
`safe evidence for future treatment strategies.
`
`Limitations
`
`Given the small sample size in our cohort, we were not able
`yet to determine any treatment advantage according to
`diagnosis. Also, the study was not designed to show the
`superiority of the combination treatment versus a mono-
`therapy. Clearly, larger studies are needed to show the
`incidence of possible unfavourable interactions of sildenafil
`and bosentan, as well as its effectiveness in terms of reverse
`remodelling of the pulmonary vascular bed, especially in
`children. Finally, part of the response to the combination
`might be an increased pulmonary arterial blood flow due
`to right ventricular recompensation which leads to almost
`unchanged pulmonary arterial pressure; however, flow was
`not assessed during cardiac catheterization in our patients.
`This issue remains an important consideration and will be
`the focus of further studies in this area.
`
`Conclusion
`
`Our initial experience with a combination of oral bosentan
`and sildenafil in a group of patients with different forms of
`PAH suggests that this treatment strategy is efficient and
`safe. Further trials with larger patient numbers are necessary
`to provide evidence for clinical and therapeutic decisions in
`the diverse forms of PAH.
`
`Acknowledgements
`
`This work was supported by the Competence Network for
`Congenital Heart Defects (Kompetenznetz Angeborene
`Herzfehler) funded by the German Federal Ministry of
`Education and Research (BMBF), FKZ 01G10210.
`
`References
`
`1 D’Alonzo GE, Barst RJ, Ayres SM, Bergofsky EH,
`Brundage BH, Detre KM et al. Survival in patients with
`primary pulmonary hypertension. Results from a national
`prospective registry. Ann Intern Med 1991;115 (5):343–9.
`2 Sitbon O, Humbert M, Nunes H, Parent F, Garcia G,
`Herve P et al. Long-term intravenous epoprostenol infusion
`in primary pulmonary hypertension: prognostic factors and
`survival. J Am Coll Cardiol, 2002;40 (4):780–8.
`3 McLaughlin VV, Shillington A, Rich S. Survival in primary
`pulmonary hypertension: the impact of epoprostenol therapy.
`Circulation 2002;106 (12):1477–82.
`
`Oral combination therapy for PAH 37
`
`4 Smits JM, Vanhaecke J, Haverich A, de Vries E, Smith M,
`Rutgrink E et al. Three-year survival rates for all consecutive
`heart-only and lung-only transplants performed in
`Eurotransplant, 1997–1999. Clin Transpl 2003;17 (2):89–100.
`5 Hertz MI, Taylor DO, Trulock EP, Boucek MM, Mohacsi PJ,
`Edwards LB et al. The registry of the international society for
`heart and lung transplantation: nineteenth official report-2002.
`J Heart Lung Transplant 2002;21 (9):950–70.
`6 Galie N, Seeger W, Naeije R, Simonneau G, Rubin LJ.
`Comparative analysis of clinical trials and evidence-based
`treatment algorithm in pulmonary arterial hypertension. J Am
`Coll Cardiol 2004;43 (Suppl. 12):S81–8.
`7 Humbert M, Sitbon O, Simonneau G. Treatment of pulmonary
`arterial hypertension. N Engl J Med 2004;351 (14):1425–36.
`8 Barst RJ, Rubin LJ, Long WA, McGoon MD, Rich S,
`Badesch DB et al. A comparison of continuous intravenous
`epoprostenol (prostacyclin) with conventional therapy for
`primary pulmonary hypertension: The Primary Pulmonary
`Hypertension Study Group. N Engl J Med 1996;334 (5):296–
`302.
`9 Rubin LJ, Mendoza J, Hood M, McGoon M, Barst R,
`Williams WB et al. Treatment of primary pulmonary
`hypertension with continuous intravenous prostacyclin
`(epoprostenol): results of a randomized trial. Ann Intern
`Med 1990;12 (7):485–91.
`10 Simonneau G, Barst RJ, Galie N, Naeije R, Rich S,
`Bourge RC et al. Continuous subcutaneous infusion of
`treprostinil, a prostacyclin analogue, in patients with pulmonary
`arterial hypertension: a double-blind, randomized,
`placebo-controlled trial. Am J Respir Crit Care Med 2002;165
`(6):800–4.
`11 Olschewski H, Simonneau G, Galie N, Higenbottam T,
`Naeije R, Rubin LJ et al. Inhaled iloprost for severe pulmonary
`hypertension. N Engl J Med 2002;347 (5):322–9.
`12 Opitz CF, Wensel R, Winkler J, Halank M, Bruch L,
`Kleber FX et al. Clinical efficacy and survival with first-line
`inhaled iloprost therapy in patients with idiopathic pulmonary
`arterial hypertension. Eur Heart J 2005;26 (18):1895–902.
`13 Galie N, Humbert M, Vachiery JL, Vizza CD, Kneussl M,
`Manes A et al. Effects of beraprost sodium, an oral prostacyclin
`analogue, in patients with pulmonary arterial hypertension:
`a randomized, double-blind, placebo-controlled trial. J Am Coll
`Cardiol 2002;39 (9):1496–502.
`14 Barst RJ, McGoon M, McLaughlin V, Tapson V, Rich S,
`Rubin L et al. Beraprost therapy for pulmonary arterial
`hypertension. J Am Coll Cardiol 2003;41 (12):2119–25.
`15 Mikhail GW, Prasad SK, Li W, Rogers P, Chester AH,
`Bayne S et al. Clinical and haemodynamic effects of sildenafil
`in pulmonary hypertension: acute and mid-term effects.
`Eur Heart J 2004;25 (5):431–6.
`16 Michelakis E, Tymchak W, Lien D, Webster L, Hashimoto K,
`Archer S. Oral sildenafil is an effective and specific pulmonary
`vasodilator in patients with pulmonary arterial hypertension:
`comparison with inhaled nitric oxide. Circulation 2002;105
`(20):2398–403.
`17 Abrams D, Schulze-Neick I, Magee AG. Sildenafil as a selective
`pulmonary vasodilator in childhood primary pulmonary
`hypertension. Heart 2000;84 (2):E4.
`18 Galie N, Ghofrani HA, Torbicki A, Barst RJ, Rubin LJ,
`Badesch D et al. Sildenafil citrate therapy for pulmonary arterial
`hypertension. N Engl J Med 2005;353 (20): 2148–57.
`19 Ghofrani HA, Voswinckel R, Reichenberger F, Olschewski H,
`Haredza P, Karadas B et al. Differences in hemodynamic and
`oxygenation responses to three different phosphodiesterase-5
`inhibitors in patients with pulmonary arterial hypertension:
`
`© 2006 The Authors
`Journal compilation © 2006 Blackwell Publishing Ltd, European Journal of Clinical Investigation, 36 (Suppl. 3), 32–38
`
`UNITED THERAPEUTICS CORP., EX1014, page 6
`UNITED THERAPEUTICS CORP. v. ACTELION PHARMACEUTICALS
`U.S. PATENT 8,268,847
`
`

`

`38 K. Lunze et al.
`
`a randomized prospective study. J Am Coll Cardiol 2004;44
`(7):1488–96.
`20 Rubin LJ, Badesch DB, Barst RJ, Galie N, Black CM,
`Keogh A et al. Bosentan therapy for pulmonary arterial
`hypertension. N Engl J Med 2002;346 (12):896–903.
`21 Galie N, Hinderliter AL, Torbicki A, Fourme T,
`Simonneau G, Pulido T et al. Effects of the oral
`endothelin-receptor antagonist bosentan on echocardiographic
`and doppler measures in patients with pulmonary arterial
`hypertension. J Am Coll Cardiol 2003;1 (8):1380–6.
`22 Sitbon O, McLaughlin VV, Badesch DB, Barst RJ, Black C,
`Galie N et al. Survival in patients with class III idiopathic
`pulmonary arterial hypertension treated with first line oral
`bosentan compared with an historical cohort of patients started
`on intravenous epoprostenol. Thorax 2005;60 (12):1025–30.
`23 McLaughlin VV, Sitbon O, Badesch DB, Barst RJ, Black C,
`Galie N et al. Survival with first-line bosentan in patients with
`primary pulmonary hypertension. Eur Respir J 2005;25
`(2):244–9.
`24 Rosenzweig EB, Ivy DD, Widlitz A, Doran A, Claussen LR,
`Yung D et al. Effects of long-term bosentan in children with
`pulmonary arterial hypertension. J Am Coll Cardiol 2005;46
`(4):697–704.
`25 Barst RJ, Rich S, Widlitz A, Horn EM, McLaughlin V,
`McFarlin J. Clinical efficacy of sitaxsentan, an endothelin-A
`receptor antagonist, in patients with pulmonary arterial
`hypertension: open-label pilot study. Chest 2002;121 (6):1860–8.
`26 Galie N, Badesch D, Oudiz R, Simonneau G, McGoon MD,
`Keogh AM et al. Ambrisentan therapy for pulmonary arterial
`hypertension. J Am Coll Cardiol 2005;46 (3):529–35.
`27 Hoeper MM, Faulenbach C, Golpon H, Winkler J, Welte T,
`Niedermeyer J. Combination therapy with bosentan and
`sildenafil in idiopathic pulmonary arterial hypertension. Eur
`Respir J 2004;24 (6):1007–10.
`28 Hoeper MM, Markevych I, Spiekerkoetter E, Welte T,
`Niedermeyer J. Goal-oriented treatment and combination
`therapy for pulmonary arterial hypertension. Eur Respir J
`2005;26 (5):858–63.
`29 Wilkens H, Guth A, Konig J, Forestier N, Cremers B, Hennen
`B et al. Effect of inhaled iloprost plus oral sildenafil in patients
`with primary pulmonary hypertension. Circulation 2001;104
`(11):1218–22.
`30 Ghofrani HA, Wiedemann R, Ros