Ambrisentan, tablets, 5 mg and 10 mg, Volibris®
Public summary document for Ambrisentan, tablets, 5 mg and 10 mg, Volibris®
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Public Summary Document
Product: Ambrisentan, tablets, 5 mg and 10 mg,
Volibris®
Sponsor: GlaxoSmithKline Australia Pty Ltd
Date of PBAC Consideration: July 2009
1. Purpose of Application
The submission requested a Section 100 (Highly Specialised Drugs)
listing for treatment of primary pulmonary hypertension (PPH) or
pulmonary arterial hypertension secondary to connective tissue
disease (PAH-CTD) in patients with WHO functional class III or IV
severity.
Highly Specialised Drugs are medicines for the treatment of chronic
conditions, which, because of their clinical use or other special
features, are restricted to supply to public and private hospitals
having access to appropriate specialist facilities.
2. Background
This drug had not previously been considered by the PBAC.
3. Registration Status
Ambrisentan was TGA registered on 24 November 2008 for the
treatment of idiopathic pulmonary arterial hypertension and
pulmonary arterial hypertension associated with connective tissue
disease in patients with WHO functional class II, III or IV
symptoms.
4. Listing Requested and PBAC’s View
The requested restriction for ambrisentan was similar to the
restrictions for bosentan (class III and IV) and sitaxentan (class
III), which are the other endothelin receptor antagonists listed on
the PBS.
For PBAC’s views see Recommendation and
Reasons.
5. Clinical place for the proposed therapy
Ambrisentan would provide an alternative oral therapy for primary
pulmonary hypertension and pulmonary arterial hypertension
secondary to connective tissue disease, in patients with WHO
Function Class III or IV severity.
6. Comparator
The submission nominated bosentan as the comparator.
7. Clinical trials
The submission presented a placebo based indirect comparison of
ambrisentan with bosentan using two randomised ambrisentan placebo
controlled 12 week trials (AMB320 and AMB321) and two randomised
bosentan placebo controlled 16 week trials (AC351 and AC352).
The following table details the trials presented in the
submission:
Trials considered in the submission for the indirect
comparison.
| Trial ID/First Author | Protocol title/Publication title | Publication citation |
| Common reference placebo | ||
| Bosentan | ||
| AC-052-352 (AC-352) | Bosentan therapy for pulmonary arterial hypertension | Rubin et al (2002). New England Journal of Medicine . 346 (12): 896-903. |
| AC-052-351 (AC-351) | Effects of the dual endothelin-receptor antagonist bosentan in patients with pulmonary hypertension: A randomised placebo-controlled study. | Channick et al (2001). The Lancet. 358 (9288): 1119-23. |
| Ambrisentan | ||
| AMB 320 (ARIES-1) | ARIES-1: A placebo-controlled, efficacy and safety study of ambrisentan in patients with pulmonary arterial hypertension. Ambrisentan therapy for pulmonary arterial hypertension: A comparison by PAH aetiology. | Oudiz et al (2006). Chest ; 130(4):121S. Badesch DB (2007). Chest , 132 (4):488S |
| AMB 321 (ARIES-2) | AMB-321 (ARIES-2). Ambrisentan in PAH, a phase III, randomised, double-blind, placebo-controlled, multicentre, efficacy study of ambrisentan in subjects with pulmonary arterial hypertension. | |
| ARIES-C | Ambrisentan for the treatment of pulmonary arterial hypertension: Results of the ambrisentan in pulmonary arterial hypertension, randomized, double-blind, placebo-controlled, multicentre efficacy (ARIES) study 1 and 2 | Galie et al (2008). Circulation ,117:3010-19 |
PAH = pulmonary arterial hypertension; od = once daily; bd = twice
daily; WHO = World Health Organization; FC = functional class
The indirect comparison was based on 1) combined ambrisentan data
(termed ARIES C in the submission) rather than on the individual
ambrisentan trial data (5mg treatment arms were combined as were
the placebo arms from AMB321 and AMB320) and pooled bosentan data
(125 mg bd) from AC351 (Channick et al (2001) and AC352 (Rubin et
al (2002); and 2) sub group data (for WHO class III and IV patients
at baseline) given that the ambrisentan trials recruited patients
with other WHO functional classes (I-IV) at baseline (40% of
patients were WHO class I-II at baseline). The primary outcome was
mean change from baseline in 6 minute walk distance (6MWD), which
the submission claimed was a valid surrogate for survival.
The submission also presented survival data for ambrisentan from
ARIES E (an extension study to AMB321 and AMB320) and different
bosentan studies (without conducting a formal comparison).
8. Results of trials
The submission conducted a placebo based indirect comparison of
ambrisentan and bosentan.
Primary endpoint - the 6 Minute Walk Distance (6MWD)
The claim of non-inferiority in the submission was based on two
different estimates of the minimal clinically important difference
(MCID) in the 6MWD: -35m (based on the power of the ambrisentan
trials to detect this difference) and -50m (based on differences
observed in the bosentan trials).
The results indicated that treatment with either dose of
ambrisentan, or with bosentan 125 mg twice daily (bd), is
associated with a statistically significant improvement from
baseline in 6MWD compared with placebo. There was no statistically
significant difference between ambrisentan and bosentan in the
placebo based indirect comparison of 6MWD.
Secondary endpoints - Borg Dyspnea Index (BDI), change from
baseline for WHO functional class and clinical
worsening:
The placebo based indirect comparisons indicated that there was no
statistically significant difference in mean BDI change from
baseline between ambrisentan 5 mg daily and bosentan 125mg twice
daily, whereas there was a statistically significant difference in
mean BDI change from baseline between ambrisentan 10 mg daily and
bosentan 125 mg twice daily in favour of ambrisentan.
There was no statistically significant difference between
ambrisentan (5 mg or 10 mg daily doses) and bosentan 125 mg twice
daily dose with respect to improvement in WHO functional class from
baseline.
The indirect comparison results indicated that there was no
statistically significant difference in clinical worsening rates
between ambrisentan and bosentan.
Haemodynamic data from AMB321/AMB320 were not provided in the
submission.
With respect to adverse events, the incidence of serious adverse
effects (SAEs) was higher for patients treated in the placebo arms
compared to patients treated with either dose of ambrisentan. The
incidence of any reported serious adverse events was similar for
both doses of ambrisentan. With the exception of right ventricular
failure for the 5 mg ambrisentan group, no other individual serious
adverse event occurred at an incidence greater than 2 %
.
The most common adverse event in the long
term extension ambrisentan study (ARIES E) was peripheral oedema.
SAE data for bosentan were predominantly not reported.
Abnormal liver function is recognised to be a class effect of
endothelin receptor antagonists. The bosentan trials indicated that
treatment with the active drug increases the risk of elevated
transaminase levels compared to treatment with placebo.
Liver function test levels in patients treated with ambrisentan
appeared unremarkable throughout the 108 week study period.
From the Periodic Safety Update Report for ambrisentan, two new
safety issues were identified: fluid retention, requiring
intervention with a diuretic or hospitalisation for fluid
management within weeks of starting ambrisentan therapy, and
dyspnoea occurring shortly after initiating ambrisentan
therapy.
9. Clinical Claim
The submission described the 5 mg daily and 10 mg daily doses of
ambrisentan as non-inferior in terms of comparative effectiveness
and non-inferior in terms of comparative safety over bosentan 125
mg twice daily.
10. Economic Analysis
The submission presented a cost minimisation analysis. Ambrisentan
5 mg once daily or ambrisentan 10mg once daily and bosentan 125 mg
twice daily were claimed to be equi-effective from the
placebo-based indirect comparison of ambrisentan to bosentan using
two ambrisentan trials (AMB320 and AMB321) and two bosentan trials
(AC351 and AC352).
11. Estimated PBS Usage and Financial Implications
The submission estimated the likely number of patients/year to be
less than 1000 in Year 2014. The net financial implications to the
PBS were claimed to be nil through all the years of extrapolation
(up to 2014).
12. Recommendation and Reasons
The PBAC recommended the listing of ambrisentan as a Section 100
Highly Specialised Drugs (HSD) Program Public and Private Hospital
Authority required benefit for the treatment of primary pulmonary
hypertension (PPH) or pulmonary arterial hypertension secondary to
connective tissue disease (PAH-CTD) in patients with a World Health
Organisation (WHO) functional class III or IV severity on a cost
minimisation basis to bosentan. The equi-effective doses are
ambrisentan 5 mg daily and bosentan 125 mg twice daily.
The PBAC accepted that bosentan was the appropriate comparator,
considering the two drugs belong to the same therapeutic class. The
PBAC considered that ambrisentan was non-inferior to bosentan on
the basis of the indirect comparison of the mean change from
baseline in the six minute walk distance (6MWD) results. The PBAC
noted that it would have been informative for haemodynamic data
and/ or outcome data to be presented, considering that haemodynamic
parameters correlate with clinical state, functional class,
exercise capacity, and prognosis in patients with PAH.
The PBAC considered the toxicity of ambrisentan appeared
non-inferior to bosentan. It was noted that liver function tests in
patients treated with ambrisentan appeared to be within acceptable
range in the study period, however the PBAC considered that
additional time is required to determine whether ambrisentan is
associated with liver toxicity as such adverse effects may emerge
with longer term treatment.
The PBAC considered economic uncertainty remained in the cost
effectiveness of ambrisentan, however the uncertainty was similar
to that accepted for the other PBS listed endothelin receptor
antagonists for the treatment of PPH and PAH. The PBAC noted that
the patient population for which listing of ambrisentan was sought
are already eligible to receive subsidised treatment with the
currently PBS listed PAH therapies and hence that ambrisentan will
only provide an additional treatment option, with no unique patient
group.
The PBAC recommended the restriction eligibility and continuation
criteria should take account of the TGA approved indications and
dosage recommendations for ambrisentan, as should the clinical
interchangeability arrangements specified in the PBS restrictions
for the agents used in PPH and PAH. The PBAC noted that the Highly
Specialised Drugs Working Party support the inclusion of
ambrisentan on the HSD Program.
Recommendation
AMBRISENTAN, tablets, 5 mg and 10 mg
Restriction: Section 100 (Highly Specialised Drugs Program)
Public and private hospital authority required
Complex - to be finalised
Pack size: 30
13. Context for Decision
The PBAC helps decide whether and, if so, how medicines should be
subsidised in Australia. It considers submissions in this context.
A PBAC decision not to recommend listing or not to recommend
changing a listing does not represent a final PBAC view about the
merits of the medicine. A company can resubmit to the PBAC or seek
independent review of the PBAC decision.
