US Patent 9,549,926 Landscape: What Claims Cover for Ambrisentan + Tadalafil Combination in Pulmonary Arterial Hypertension
US Drug Patent 9,549,926 is a combination therapy method-of-treatment patent for pulmonary arterial hypertension (PAH) using ambrisentan + tadalafil at defined weight ratios, with claim coverage spanning co-administration, sequential vs simultaneous dosing, and oral or parenteral administration formats.
Key takeaways on claim scope and coverage
- Core claim element: treating PAH in a human by co-administering ambrisentan and tadalafil.
- Hard limitation: the ambrisentan:tadalafil weight ratio must be about 1:2 or about 1:3.
- Coverage breadth: includes same time and sequential dosing (claims 3 and 4), and oral or parenteral routes (claim 5).
- Practical implication for design-arounds: products and clinical regimens that use the same two drugs but outside the specified weight-ratio window are the most direct route to reduce infringement risk, assuming other elements are satisfied.
What does US Patent 9,549,926 claim and how broad is the method coverage?
Answer (featured-snippet): The patent claims methods of treating PAH by co-administering ambrisentan and tadalafil in humans at a defined weight ratio of ~1:2 or ~1:3, including sequential or simultaneous dosing and oral or parenteral administration.
Claim 1 is the independent claim with the highest practical infringement relevance
Claim 1 recites the full combination method:
- Indication: pulmonary arterial hypertension
- Patient: “in a human patient in need thereof”
- Therapy: co-administer therapeutic amount of ambrisentan and therapeutically effective amount of tadalafil
- Ratio: weight ratio ambrisentan:tadalafil ~1:2 or ~1:3
This makes Claim 1 the anchor for infringement analysis. Any product or clinical protocol that administers both active ingredients to a PAH patient at those ratios and in a manner that meets “co-administering” is within the broadest scope.
Claim 2 tightens ratio to a single endpoint
Claim 2 narrows Claim 1 to:
This provides an alternate, narrower infringement path even if a defendant tries to argue the protocol is closer to the other ratio.
Claims 3 and 4 define dosing timing options
- Claim 3 (sequential): ambrisentan and tadalafil administered sequentially
- Claim 4 (same time): administered “at the same time”
These two claims together eliminate an easy design-around based solely on scheduling.
Claim 5 defines route flexibility
Claim 5 states the method can be administered:
So the patent does not depend on a specific dosage form or delivery system.
Claims 6 further narrows ratio to ~1:3
Claim 6 narrows Claim 1 to:
How do the weight-ratio limitations function legally and technically?
Answer (featured-snippet): The weight-ratio requirement (ambrisentan:tadalafil ~1:2 or ~1:3) is the key limiting feature that can control infringement outcomes even when the same drugs are prescribed together.
Ratio is the dominant differentiator vs generic “combination therapy” claims
Many PAH combination patents can be drafted broadly and still be hard to invalidate. Here, ratio acts as the principal numerical limitation. For infringement, the litigation focus typically becomes:
- what the administered “amount” is in practice (dose schedules and timing),
- what “weight ratio” means in the context of clinical administration, and
- whether the regimen falls within “about” 1:2 or “about” 1:3.
“About” introduces tolerance but still creates a numerical boundary
The claim uses “about” rather than a hard value, which usually implies some acceptable deviation. However, the presence of only two ratio targets limits ambiguity. A regimen that uses a ratio materially different from both targets is a more plausible non-infringing route than a regimen close to one of them.
What counts as “weight ratio” in a real-world regimen?
Based on claim language, the ratio is framed as ambrisentan (weight) to tadalafil (weight). In practice, that means a comparison of the amounts administered to the patient in the same overall therapeutic administration window (and/or as a paired dosing scheme).
Because the claims also cover sequential and simultaneous administration, the ratio likely ties to how the regimen pairs the active ingredients rather than requiring a fixed co-formulation.
Does the patent cover sequential dosing, simultaneous dosing, or both?
Answer (featured-snippet): Yes. Claim 3 covers sequential dosing and Claim 4 covers simultaneous dosing.
Claim 3: sequential dosing
Sequential administration is explicitly covered. That forecloses an argument that a regimen is exempt because the drugs are not administered concurrently.
Claim 4: same-time dosing
Same-time dosing is also explicitly covered, reducing the ability to argue that the patent only covers one scheduling style.
Net effect
If a competitor administers the same two actives to PAH patients at qualifying ratios, the timing alone is not enough to avoid infringement.
Does the patent require oral dosage forms, or does it cover parenteral routes?
Answer (featured-snippet): The patent covers both oral and parenteral administration.
Claim 5: route is not limiting
Claim 5 expressly includes:
- oral administration
- parenteral administration
This expands the set of potentially infringing regimens to include, for example, parenteral delivery approaches for either drug, or regimens where one is oral and the other is parenteral, if the dosing meets the ratio and co-administration requirements.
What therapeutic area and patient population does the claim cover?
Answer (featured-snippet): The method is limited to treating pulmonary arterial hypertension in humans.
PAH scope is clinically narrow vs broader pulmonary hypertension
The claim states pulmonary arterial hypertension, not “pulmonary hypertension” generally. That distinction matters because many pulmonary hypertension patients have etiologies outside PAH. The claimed method requires the PAH population.
How strong is the patent estate around combination therapy like ambrisentan + tadalafil?
Answer (featured-snippet): The strength of US 9,549,926 depends most on how narrowly or broadly “weight ratio” and “co-administering” are construed; otherwise, the remaining elements are standard for method-of-treatment combination claims.
Claim architecture suggests a targeted combination use
This patent does not look like a generic “use of drugs together for PAH.” It looks like a specific pairing with an explicit numerical dosing relationship.
That generally improves enforceability because it narrows the claimed subject matter away from prior art “combination” disclosures that lacked the specific ratio.
Litigation pressure point
Opponents often attack:
- the sufficiency of disclosure in the specification for the claimed ratio ranges,
- obviousness over known PAH therapies plus known phosphodiesterase type 5 inhibition plus known endothelin receptor antagonism,
- and claim construction on what “about” and the “weight ratio” mean in administration practice.
Those are the pressure points most consistent with how courts treat numerical combination limitations.
Which claim limitations create the highest infringement risk for competitors?
Answer (featured-snippet): The ratio and the “treating PAH in a human patient” elements are the most direct infringement triggers.
Highest-risk elements
- Therapeutic treatment of PAH: if the method is used for PAH patients.
- Co-administration of ambrisentan and tadalafil: if both actives are administered as part of the regimen.
- Weight ratio ~1:2 or ~1:3: if dosing pairing yields those ratios.
Lower-risk elements (in the sense of not limiting)
- Sequential vs simultaneous: both covered.
- Oral vs parenteral: both covered.
What generic entry risks exist for infringing combination method claims?
Answer (featured-snippet): If an ANDA or other generic pathway supplies ambrisentan and tadalafil separately but the combination is used clinically in a qualifying PAH dosing ratio, method-of-treatment infringement risk can attach depending on how “use” is asserted and what sales conduct is captured.
How method claims typically create practical exposure
Even when generics do not market a fixed-dose combination, risk can arise if:
- the generic drugs are marketed or used together for PAH,
- prescribers follow instructions or clinical protocols that match the claimed method,
- and the ratio limitation is satisfied.
Ratio-based protocols reduce the “any combination” risk
A key defensive lever is that generic availability alone does not dictate the ratio. If the practical dosing in the field does not align with ~1:2 or ~1:3 weight ratio pairings, the direct match to Claim 1 is weaker.
Are there likely enforceability or design-around pathways?
Answer (featured-snippet): The most plausible design-around is to use the same drugs but avoid the claimed weight ratio targets and/or avoid prescribing the claimed PAH regimen as a method.
Ratio shifting
If a regimen consistently uses ratios not “about 1:2” and not “about 1:3,” it can reduce infringement likelihood.
Timing and route do not appear to be design-around levers
Because Claims 3-5 are explicit, changing:
- sequential to simultaneous,
- oral to parenteral,
does not remove coverage if the ratio and co-administration are still met.
What does this claim coverage imply for licensing strategy or settlement positioning?
Answer (featured-snippet): The patent is built to monetize co-administration at defined ratios, so settlements often hinge on dosing protocols and label or promotional language aligning with or departing from the claimed ratios.
Likely commercial negotiation points
- Whether a proposed generic or branded combination product (or co-prescribing strategy) yields ambrisentan:tadalafil ratios close to 1:2 or 1:3.
- Whether any label directions, patient instructions, or “how to take” guidance match the claimed method.
Exposure mapping
- Companies planning a combination regimen can assess infringement risk by calculating the intended delivered amounts of each active ingredient and comparing the ratio to ~1:2 and ~1:3.
- If the ratio cannot be mapped with sufficient precision or is clearly outside the targets, the risk profile changes materially.
How does US 9,549,926 compare with typical PAH combination patents?
Answer (featured-snippet): Compared with broader PAH combination claims, US 9,549,926 adds numerical specificity (ambrisentan:tadalafil weight ratio) and provides explicit coverage across timing (sequential vs simultaneous) and route (oral vs parenteral).
Practical differences that matter in prosecution or litigation
- Numerical limitation reduces claim overlap with generic “use together” prior art.
- Explicit timing and route statements reduce the number of non-infringing fact patterns.
Key takeaways
- US 9,549,926 claims a method-of-treatment for PAH using ambrisentan + tadalafil at weight ratios ~1:2 or ~1:3.
- The patent covers both sequential and simultaneous dosing and both oral and parenteral routes.
- The ratio limitation is the central lever for infringement risk, licensing scope, and design-around strategy.
- Generic entry risk is driven less by product availability and more by how the regimen is used in practice, particularly whether prescribed dosing aligns with the claimed ratio targets.
FAQs
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Does US 9,549,926 require a fixed-dose combination drug product?
No. The claims cover co-administration and specify oral or parenteral routes, including sequential dosing.
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If ambrisentan and tadalafil are prescribed separately, does that still meet “co-administering”?
Yes, if the clinical regimen results in the patient receiving therapeutically effective amounts together as required by the claims, including the specified weight ratio.
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Can a regimen avoid infringement by changing dosing timing?
Timing alone is not a reliable design-around because sequential and same-time administration are both claimed.
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What is the most direct design-around lever?
Using a dosing regimen that avoids ambrisentan:tadalafil weight ratios “about 1:2” and “about 1:3.”
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Is the patent limited to pulmonary arterial hypertension rather than all pulmonary hypertension?
Yes. The method is limited to pulmonary arterial hypertension in a human patient.
References
- Claims of US Patent 9,549,926, provided in prompt.
