When do biologic drug patents expire and when will biosimilars launch?

United States Patent 7,550,434: What the Claims Cover, Where They Are Narrow, and How the Landscape Looks

US 7,550,434 is centered on a liquid (not lyophilized) parenteral formulation of human PTH(1-34) for use with sealed vials/cartridges and withdrawal directly for injection. The patent’s novelty positioning is built around avoiding a lyophilization step while maintaining stability using a polyol and buffer/preservative package at defined ranges.

What is claimed (and what is not)?

The independent claim structure spans four layers:

A preparation process for a sealed vial/cartridge containing sterile PTH(1-34) solution that is ready for parenteral administration without lyophilization (Claim 1).
The sealed vial/cartridge composition with the same functional constraints (Claims 12-23).
A method of treating osteoporosis via parenteral administration using that solution, with withdrawal from a sealed vial/cartridge without lyophilization (Claims 24-34).

Key negative limitation: the solution “does not undergo a step of lyophilization prior to use by the patient.” This limitation is the patent’s core boundary. It is not limited to a particular device type beyond “vial or cartridge,” and it does not require any specific injection technology (prefilled syringe is implied only if it is functionally a “sealed cartridge”).

Core claim elements (1-34) and their legal boundaries

Independent claim 1: process scope

Claim 1 requires each of the following:

API identity: “human PTH(1-34)”
Concentration: 100 to 500 µg/mL
Stabilizer: polyol stabilizing agent
Buffer: buffering system maintaining pH > 3 to 6
Preservative: “parenterally acceptable preservative”
Packaging/handling: solution is sealed in a vial or cartridge from which a therapeutically effective dose can be withdrawn for parenteral administration by a human patient
No lyophilization: “wherein the solution does not undergo a step of lyophilization prior to use by the patient”

Critical point for infringement and validity: Claim 1 is broad on stabilizer identity, buffer identity (generic), and preservative identity (generic). The “no lyophilization” limitation is the main constraining factor.

Independent claim 12: product-by-claims scope

Claim 12 requires:

PTH(1-34): 100 to 500 µg/mL
Buffer system: pH range > 3 to 6
Polyol stabilizing agent: present (but not identity or amount in Claim 12)
Preservative: present
Sterile and ready: sterile solution ready for parenteral administration
No lyophilization before patient use

This claim is a composition claim anchored to a functional workflow (ready for use without lyophilization), not to physical form beyond being a sealed sterile solution.

Independent claim 24: method scope

Claim 24 requires:

Treat osteoporosis using parenteral administration of a solution containing:
- PTH(1-34): 100-500 µg/mL
- buffer: pH > 3 to 6
- polyol stabilizing agent
- preservative
solution is sterile and ready
dose is withdrawn from a sealed vial or sealed cartridge without lyophilization

Dependent claims: how the patent narrows (and where competitors can route around)

Polyol stabilizer narrowing (Claims 2-3, 13-14, 25-26)

Polyol concentration: 3 to 10 wt-% (Claims 2, 13, 25)
Polyol identity: mannitol (Claims 3, 14, 26)

Landscape implication: If a competitor uses a different polyol (e.g., sorbitol, glycerol, xylitol) or uses mannitol outside 3-10 wt-%, the formulation may avoid these dependent claims while still potentially falling within Claim 1/12/24 if generic “polyol stabilizing agent” is argued broadly.

Buffer system narrowing (Claims 4-5, 15-16, 27-28)

Selected from citrate, tartrate or acetate (Claims 4, 8, 15, 19, 27, 31)
Acetate buffer (Claims 5, 9, 16, 20, 28, 32)

Landscape implication: A competitor using a different buffer system outside these (e.g., phosphate, HEPES) could avoid the dependent buffer claims, but could still face the independent claims depending on how “buffering system” and pH range are interpreted.

Preservative narrowing (Claims 6-7, 10-11, 17-18, 21-22, 29-30, 33-34)

Preservatives listed:

cresols (category)
benzyl alcohol
phenol
benzalkonium chloride
benzethonium chloride
chlorobutanol
phenylethyl alcohol
methyl paraben
propyl paraben
thimerosal
phenylmercuric nitrate
phenylmercuric acetate

Specific: m-cresol (Claims 7, 11, 18, 22, 30, 34)

Landscape implication: Because Claim 1/12/24 treat “parenterally acceptable preservative” as generic, moving preservatives could be risky for independent-claim infringement. But it is an effective route around for the dependent claims anchored to particular preservative choices.

The specific exemplified formulation (Claim 23)

Claim 23 locks a specific quantitative composition:

PTH(1-34) at 250 µg/mL
Glacial acetic acid: 0.41 mg/mL
Sodium acetate (anhydrous): 0.10 mg/mL to maintain pH > 3 to 6
Mannitol: 45.4 mg/mL
m-cresol: 3.0 mg/mL
sterile and ready for parenteral use without lyophilization

Why Claim 23 matters: It turns the patent from a general formulation cover into a “hard target” with exact concentrations. Even if broad claims are avoided, Claim 23 can still catch close formulations.

Critical evaluation: where the claims are strong vs. where they are vulnerable

Strengths

Workflow limitation (“no lyophilization prior to use by the patient”)
- This is a crisp process boundary. If a commercial product requires lyophilized reconstitution, it does not meet this limitation.
Sealed vial/cartridge framing
- The claims are tied to withdrawal from sealed containers, not to manufacturing steps that could be disputed.
Tight pH band
- pH is constrained to > 3 to 6, which reduces formulation design freedom.

Weaknesses / vulnerability points

Breadth at the independent level
- Claim 1/12/24 broadly cover “polyol stabilizing agent” and “parenterally acceptable preservative.” Broad functional categories can face:
  - prior-art anticipation or obviousness risk if multiple earlier references already disclosed liquid PTH(1-34) with polyol buffering-preservative combinations; and/or
  - claim-construction challenges if competitors argue their excipients are not “stabilizing” or their pH management differs.
Polyol definition is not limited to mannitol at the independent level
- Dependent claims lock in mannitol, but independent claims do not. That can cut both ways:
  - it broadens infringement coverage; and
  - it increases invalidity exposure if the prior art already used mannitol or other polyols in similar PTH solutions.
No explicit exclusion of other excipients
- The claims do not say “consisting of” only the listed components. That matters for infringement: a competitor formulation with the required core components plus additional excipients could still infringe if the required elements are present.
Device/form factor ambiguity
- The claims say “vial or cartridge.” If competitors use different formats (e.g., prefilled syringes treated as “containers,” or autoinjectors with different internal configurations), infringement can become a technical claim-matching exercise tied to whether those are “vials” or “cartridges.”

How to read the patent landscape around this claim set

Given the claim content, the relevant landscape cluster is formulation IP for PTH(1-34) liquid delivery:

stability engineering (polyols + buffering)
preservation under multidose or patient-use conditions
packaging and administration workflow (sealed container; no lyophilization at patient use)
therapeutic indication (osteoporosis treatment)

From a business perspective, the patent landscape breaks into three commercial risk lanes:

Lyophilized PTH(1-34) systems
- High likelihood of moving outside the “no lyophilization” limitation.
Liquid PTH(1-34) systems with polyols + pH 3-6 + preservative
- High likelihood of meeting independent claims if they use the required excipient classes and pH range.
Liquid systems that diverge on one axis
- If they avoid polyols, avoid pH 3-6, or avoid a preservative, they reduce independent claim risk.
- If they diverge on preservative identity or polyol type/amount, they can reduce dependent claim risk.

Infringement decision matrix (practical claim matching)

Below is a simplified mapping of required elements to claim tiers.

Element	Independent (Claims 1, 12, 24)	Key dependent constraints
PTH(1-34) identity	Required	None
PTH concentration	100-500 µg/mL	Claim 23: 250 µg/mL example
Lyophilization	Must not occur prior to patient use	Not expanded further
Container	Sealed vial/cartridge	Not limited beyond “vial or cartridge”
Polyol stabilizer	Required (identity not limited)	Claims 2/13/25: 3-10 wt-%; Claims 3/14/26: mannitol
Buffer system	Required; pH >3 to 6	Claims 4/8/15/19/27/31: citrate/tartrate/acetate; Claims 5/9/16/20/28/32: acetate
Preservative	Required (identity not limited)	Claims 6-7/10-11/17-18/21-22/29-30/33-34: enumerated list; specific m-cresol in multiple dependents
Indication	Only in Claim 24	Osteoporosis treatment in Claim 24

What would a competitor need to change to reduce risk (by claim tier)

To avoid independent claims (1/12/24)

At least one of the required independent elements must be missing or not met under claim construction:

Use lyophilization for patient use (disrupt “no lyophilization prior to use by the patient”)
Remove “polyol stabilizing agent” as a required stabilizer function
Use a buffering system that does not maintain pH >3 to 6
Use no parenterally acceptable preservative
Avoid the “sealed vial or sealed cartridge” structure, depending on how the product is classified

To avoid dependent claims while keeping independent coverage

Competitors can often reduce dependent claim exposure by:

Using a different polyol or mannitol outside 3-10 wt-%
Using a buffer other than citrate/tartrate/acetate or not using acetate if targeting those dependents
Using a preservative outside the enumerated list or not using m-cresol specifically

This is why, in practice, even a “designed-around” formulation frequently remains vulnerable to the independent claims if it still hits the core excipient classes and pH limits.

Key takeaways

US 7,550,434 claims liquid PTH(1-34) formulations that are sealed and ready for parenteral administration without lyophilization at patient use, with pH >3 to 6, a polyol stabilizer, and a parenterally acceptable preservative.
The independent claims are broad on polyol and preservative identity, increasing both infringement coverage and validity risk exposure depending on prior art that discloses similar liquid PTH formulations.
Dependent claims narrow to mannitol (3-10 wt-%), buffer systems limited to citrate/tartrate/acetate with acetate as a specific choice, and a preservative list with m-cresol as a specific choice.
Claim 23 provides a fully quantified acetate-acid/acetate salt + mannitol + m-cresol recipe at PTH(1-34) 250 µg/mL, which can be used as a “direct hit” target for close variants.
The landscape risk posture for new liquid PTH(1-34) entries is highest when products mirror the same no-lyophilization workflow and maintain pH 3-6 with polyol + preservative.

FAQs

1) Does US 7,550,434 cover lyophilized products?

No. The claims require that the solution does not undergo lyophilization prior to patient use.

2) What range of PTH(1-34) concentration is covered?

100 to 500 µg/mL in the independent claims; Claim 23 specifies 250 µg/mL.

3) Is mannitol required?

Not in the independent claims. Mannitol is required only in dependent claims (Claims 3, 14, 26).

4) Is acetate the only buffer covered?

No. The dependent claims include citrate, tartrate, or acetate, with additional dependents specifying acetate.

5) What preservative types are covered?

A specific enumerated list in dependent claims and a generic “parenterally acceptable preservative” in independent claims; m-cresol is explicitly required in multiple dependents.

References

[1] United States Patent 7,550,434.

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Takeda Pharmaceuticals U.s.a., Inc.	NATPARA	parathyroid hormone	For Injection	125511	January 23, 2015	7,550,434	2026-10-02
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Country	Patent Number	Estimated Expiration
South Africa	9811127	⤷ Start Trial
World Intellectual Property Organization (WIPO)	9929337	⤷ Start Trial
United States of America	7144861	⤷ Start Trial
United States of America	6770623	⤷ Start Trial
United States of America	2007021344	⤷ Start Trial
United States of America	2007021343	⤷ Start Trial
United States of America	2003225000	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration

Patent: 7,550,434

Summary for Patent: 7,550,434