Details for Patent: 5,430,057
Summary for Patent: 5,430,057
| Title: | Parenteral busulfan for treatment of malignant disease | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Abstract: | Stable parenteral formulations of busulfan safe for parenteral administration are disclosed that exhibit improved bioavailability and optimize high dose busulfan therapy against malignant disease. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Inventor(s): | Borje S. Andersson, Harshal P. Bhagwatwar, Diana S. L. Chow | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assignee: | University of Texas System , University of Houston | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Application Number: | US08/129,995 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Patent Claim Types: see list of patent claims | Use; Composition; Formulation; | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Patent landscape, scope, and claims: | United States Drug Patent 5,430,057: Busulfan Formulation Claims, Expiration, and Patent LandscapeU.S. Patent No. 5,430,057 covers liquid, water-miscible busulfan formulations for intravascular administration and methods using those formulations to treat malignant disease, including leukemia, lymphoma, breast cancer, and patients undergoing bone-marrow transplantation. The patent issued July 4, 1995, and its 17-year pre-URAA patent term expired July 4, 2012, absent a qualifying extension. The patent therefore does not create a current U.S. barrier to generic intravenous busulfan. The commercial significance of the patent was its formulation solution. Busulfan has limited aqueous solubility, while the claimed solvent systems use N',N-dimethylacetamide, polyethylene glycol, propylene glycol, glycerin, cyclodextrins, or hydroxypropyl-beta-cyclodextrin to produce an injectable preparation. The claims are composition, formulation, and treatment-method claims rather than claims to busulfan itself. What does U.S. Patent 5,430,057 protect?The patent protects four related subject areas:
The core independent formulation claim requires:
The patent does not claim all busulfan products, all oral busulfan products, or busulfan as a chemical compound. Its scope depends on the injectable dosage form and the specified solvent environment. What is the patent’s claim architecture?
Claims 1, 22, 23, 24, and 26 are the principal independent claims in the supplied claim set. The narrowest commercial formulation claims are claims 22 and 23. How broad is the formulation coverage?Claim 1 is broad across solvent identity and concentration. A formulation may fall within the claim if it contains busulfan at 1-19 mg/mL and uses water plus at least one listed solvent at approximately 10-70%. The claim reaches solvent systems based on:
The claim does not require a particular pH, preservative, container, dosing schedule, infusion duration, or disease indication. Those omitted features would not remove a product from claim 1 if the listed compositional elements were present. The formulation claims are narrower where they specify PEG molecular weight or combined DMA and PEG systems. Claims 22 and 23 focus on PEG-400 and defined DMA ranges:
These claims are more vulnerable to design-around through changes in solvent composition, PEG grade, concentration, or busulfan strength. They may still be relevant where a product uses substantially equivalent concentrations or a formulation falls within the stated ranges. What method-of-use rights does Patent 5,430,057 contain?The patent contains broad and narrow method-of-use claims. Claim 2 covers treatment of a malignant disease responsive to busulfan by intravascular administration of a formulation covered by claim 1. Claim 3 narrows administration to intravenous delivery. Claims 4-21 add solvent, concentration, and PEG limitations. Claim 24 is broader in wording. It requires obtaining an intravascularly administrable busulfan preparation and administering it in an amount effective to treat a malignant condition. Unlike claim 2, the supplied language for claim 24 does not expressly incorporate every solvent limitation of claim 1. Claim 26 addresses transplant conditioning. It covers intravenous administration to a patient with leukemia or lymphoma in an amount that conditions the patient for bone-marrow transplantation. Claims 27-31 add dosing and disease limitations, including acute myelogenous leukemia and chronic myelogenous leukemia. The treatment claims were commercially important because intravenous busulfan became associated with conditioning regimens before hematopoietic stem-cell transplantation. They did not, however, create a perpetual monopoly over the medical use of busulfan. Once the patent expired, the claims ceased to block practice in the United States. When did U.S. Patent 5,430,057 expire?U.S. Patent No. 5,430,057 issued July 4, 1995. Because it was issued from a pre-June 8, 1995 application, the applicable term was generally 17 years from issuance under the transitional patent-term rules. The ordinary expiration date was therefore July 4, 2012, subject to any applicable patent-term adjustment or extension recorded in the official file. The patent is now expired.[1]
No current U.S. patent right under 5,430,057 can support an infringement action against a generic manufacturer. Historical infringement exposure remains relevant only for conduct occurring before expiration. What was the FDA and Orange Book status of Busulfex?Busulfex is the intravenous busulfan product associated with this formulation technology. The FDA approved Busulfex for use as conditioning treatment before hematopoietic progenitor-cell transplantation in patients with chronic myelogenous leukemia and other approved transplant settings described in the product labeling.[2] The regulatory framework included:
Orange Book patent listing and patent enforceability are separate issues. A listed patent can require a Paragraph IV certification during its effective listing period, but an expired patent cannot create current exclusionary rights. The Orange Book should be read historically for the patent’s listed status and expiration information, not as evidence that Patent 5,430,057 remains enforceable.[3] When did Busulfex lose regulatory exclusivity?Busulfex received orphan-drug exclusivity for its approved orphan indication. Orphan exclusivity generally runs for seven years from approval under Section 527 of the Federal Food, Drug, and Cosmetic Act.[4] The exclusivity period was separate from the patent term and did not extend Patent 5,430,057. The practical exclusivity sequence was:
An orphan designation does not prevent all competing products in every indication. It is tied to the approved orphan indication and statutory conditions. It also does not block a generic manufacturer after the orphan-exclusivity period has ended if the ANDA satisfies FDA requirements. Which claims matter most to generic intravenous busulfan?For a generic intravenous busulfan product, the main historical risk points were composition and method claims. Composition riskA product would have faced the greatest literal-claim risk if it used:
A PEG-400/DMA/water formulation at the concentrations in claims 22 or 23 would have presented a particularly direct historical overlap. Method riskA product label directing intravenous busulfan for malignant disease or transplant conditioning could have implicated claims 2, 3, 24, or 26. Claims 27-31 add dosing and disease-specific limitations, but a generic applicant would evaluate the broadest method claims first. Design-around optionsPotential design-around strategies historically included:
Because the patent has expired, these strategies are no longer needed to avoid current enforcement of Patent 5,430,057. They remain relevant for understanding the technical differentiation of later products and historical ANDA risk. Were Paragraph IV challenges and generic litigation relevant?An ANDA applicant must make a patent certification for each Orange Book-listed patent. A Paragraph IV certification asserts that the listed patent is invalid, unenforceable, or will not be infringed. Notice of a Paragraph IV certification can trigger Hatch-Waxman litigation and, in qualifying circumstances, a 30-month stay of FDA approval.[5] For Patent 5,430,057, the key commercial date was July 4, 2012. After expiration, an applicant no longer needed to defeat the patent to launch a product. Any earlier Paragraph IV activity would have been time-sensitive and dependent on the patent’s listing status, the ANDA filing date, and the sponsor’s litigation response. The supplied record does not establish a specific reported settlement agreement or active litigation involving Patent 5,430,057. The patent should therefore be treated as an expired historical Orange Book right rather than a current litigation asset. Does busulfan face biosimilar risk?No. Busulfan is a small-molecule active pharmaceutical ingredient, not a biologic subject to the Public Health Service Act biosimilar pathway. Competing injectable busulfan products proceed through the conventional drug framework, generally through ANDAs or other abbreviated or full applications under the Federal Food, Drug, and Cosmetic Act. The competitive issue is generic injectable busulfan, not biosimilar busulfan. The relevant barriers are formulation development, injectable manufacturing, analytical equivalence, stability, container closure, sterility assurance, and FDA approval. What manufacturing and intellectual-property barriers remain?Patent 5,430,057 no longer creates a manufacturing barrier. Practical barriers remain:
The patent’s technical disclosure may still be relevant as prior art and as a formulation-development reference. It does not, however, give its former patent owner control over the disclosed solvent systems today. How does the patent compare with competing busulfan estates?Patent 5,430,057 is an early injectable-formulation patent. Its principal differentiation is the use of water-miscible organic solvents and PEG-based systems to make busulfan suitable for intravascular delivery.
A freedom-to-operate analysis for a current intravenous busulfan product should not stop with Patent 5,430,057. It should examine later-filed patents covering stability, administration protocols, packaging, manufacturing, and specific clinical regimens. The supplied patent alone does not establish freedom to operate against those separate rights. What is the current commercial exposure?The commercial exposure associated specifically with Patent 5,430,057 is zero for future U.S. sales because the patent has expired. Historical revenue exposure was concentrated in the intravenous busulfan market before 2012, when Busulfex benefited from the combination of orphan exclusivity, product approval, and formulation patent protection. After expiration, the market shifted toward generic injectable busulfan competition. The principal business risks became pricing pressure, supply reliability, manufacturing cost, hospital contracting, and regulatory compliance rather than infringement of this patent. Key Takeaways
FAQsCan a generic manufacturer use the solvent systems disclosed in Patent 5,430,057?Yes, in the United States, the patent’s expiration removes its enforceability as a barrier. Other later patents or regulatory requirements must still be assessed. Does Patent 5,430,057 cover oral busulfan tablets?No. The claims supplied are directed to intravascular formulations and administration. Oral dosage forms are outside the express scope of these claims. Is PEG-400 busulfan still protected by this patent?No. PEG-400 formulations may have fallen within claims 22 or 23 during the patent term, but Patent 5,430,057 expired in 2012. Does orphan-drug exclusivity extend the patent expiration date?No. Orphan-drug exclusivity and patent term are separate legal protections. Orphan exclusivity does not extend an expired patent. Is an intravenous busulfan product a biosimilar?No. Busulfan is a small-molecule drug. Competing products use the generic-drug pathway rather than the biosimilar pathway. References
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Drugs Protected by US Patent 5,430,057
| Applicant | Tradename | Generic Name | Dosage | NDA | Approval Date | TE | Type | RLD | RS | Patent No. | Patent Expiration | Product | Substance | Delist Req. | Patented / Exclusive Use | Submissiondate |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| >Applicant | >Tradename | >Generic Name | >Dosage | >NDA | >Approval Date | >TE | >Type | >RLD | >RS | >Patent No. | >Patent Expiration | >Product | >Substance | >Delist Req. | >Patented / Exclusive Use | >Submissiondate |
International Family Members for US Patent 5,430,057
| Country | Patent Number | Estimated Expiration | Supplementary Protection Certificate | SPC Country | SPC Expiration |
|---|---|---|---|---|---|
| Austria | 197670 | ⤷ Start Trial | |||
| Australia | 694141 | ⤷ Start Trial | |||
| Australia | 7829094 | ⤷ Start Trial | |||
| Canada | 2171738 | ⤷ Start Trial | |||
| Germany | 69426334 | ⤷ Start Trial | |||
| Denmark | 0725637 | ⤷ Start Trial | |||
| European Patent Office | 0725637 | ⤷ Start Trial | |||
| >Country | >Patent Number | >Estimated Expiration | >Supplementary Protection Certificate | >SPC Country | >SPC Expiration |
