SAMARIUM SM-153 LEXIDRONAM PENTASODIUM - Generic Drug Details

What are the generic sources for samarium sm-153 lexidronam pentasodium and what is the scope of freedom to operate?

Samarium sm-153 lexidronam pentasodium is the generic ingredient in one branded drug marketed by Lantheus Medical and is included in one NDA. Additional information is available in the individual branded drug profile pages.

Summary for SAMARIUM SM-153 LEXIDRONAM PENTASODIUM

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	3
Clinical Trials:	6
Patent Applications:	485
DailyMed Link:	SAMARIUM SM-153 LEXIDRONAM PENTASODIUM at DailyMed

Recent Clinical Trials for SAMARIUM SM-153 LEXIDRONAM PENTASODIUM

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
NRG Oncology	Phase 3
National Cancer Institute (NCI)	Phase 3
Radiation Therapy Oncology Group	Phase 3

See all SAMARIUM SM-153 LEXIDRONAM PENTASODIUM clinical trials

US Patents and Regulatory Information for SAMARIUM SM-153 LEXIDRONAM PENTASODIUM

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Lantheus Medical	QUADRAMET	samarium sm-153 lexidronam pentasodium	INJECTABLE;INJECTION	020570-001	Mar 28, 1997		DISCN	Yes	No

Expired US Patents for SAMARIUM SM-153 LEXIDRONAM PENTASODIUM

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Lantheus Medical	QUADRAMET	samarium sm-153 lexidronam pentasodium	INJECTABLE;INJECTION	020570-001	Mar 28, 1997	4,898,724

Samarium-153 Lexidronam Pentasodium Market Dynamics, Financial Trajectory, and Patent Position

Last updated: September 7, 2026

Samarium-153 lexidronam pentasodium, marketed as Quadramet, is an FDA-approved radiopharmaceutical for reducing pain from osteoblastic bone metastases. Its commercial profile peaked before the expansion of targeted radioligand therapies and has since contracted. The product has limited remaining commercial relevance because of declining use, short radionuclide shelf life, specialized manufacturing requirements, and competition from radium-223 and lutetium-177 therapies.

Quadramet does not have a meaningful current U.S. branded-drug growth profile. Public filings historically reported product sales through Cytogen and later commercial partners, but recent standalone revenue disclosures are not available. The product’s legacy value is concentrated in palliative nuclear medicine, manufacturing know-how, and access to radiopharmacy infrastructure rather than in active patent exclusivity.

What is samarium-153 lexidronam pentasodium used for?

Samarium-153 lexidronam pentasodium is a bone-seeking radiopharmaceutical used for the relief of pain in patients with confirmed osteoblastic metastatic bone disease. The active radioactive isotope, samarium-153, is chemically linked to lexidronam, also known as EDTMP, a phosphonate ligand that localizes to areas of increased bone turnover.

The FDA-approved dose is 1.0 mCi/kg administered intravenously, subject to the product’s prescribing limitations. Samarium-153 has a physical half-life of approximately 46.3 hours, which limits inventory duration and requires coordinated production, quality release, shipment, and administration. The label warns of bone-marrow suppression, including thrombocytopenia and leukopenia, and requires hematologic monitoring.[1]

Quadramet is palliative. It does not treat the underlying cancer or establish a tumor-control benefit comparable to disease-modifying systemic oncology products.

FDA approval and clinical positioning

Event	Date	Commercial significance
FDA approval of Quadramet	1997	Established samarium-153 lexidronam as a U.S. bone-pain radiopharmaceutical
Initial commercial period	Late 1990s to mid-2000s	Supported by demand for radiotherapy-based palliation
Xofigo approval	2013	Introduced an alpha-particle therapy with a disease-specific prostate-cancer label
Growth of lutetium-177 radioligand therapy	2020s	Shifted nuclear oncology investment toward tumor-targeted products
Current market position	Mature or declining	Primarily a niche palliative product with limited differentiation

The product’s clinical use is strongest where patients have painful osteoblastic lesions, adequate marrow reserve, and a need for symptom control rather than tumor-directed treatment.

How large is the samarium-153 lexidronam market?

The current market is small relative to modern oncology radiopharmaceuticals. Quadramet’s commercial peak occurred when the market for radiopharmaceutical pain palliation had fewer targeted alternatives. Demand has since declined as oncology practice has shifted toward hormonal therapy, chemotherapy, external-beam radiation, bisphosphonates, denosumab, radium-223, and radioligand therapies directed at tumor antigens.

Public company filings from Cytogen Corporation identified Quadramet as a material product during the company’s commercial period, but the filings also showed that Cytogen’s overall business depended on a broader portfolio, including ProstaScint. Public filings do not provide a reliable current standalone revenue series for samarium-153 lexidronam after changes in ownership and commercialization arrangements.[2]

Historical financial trajectory

Period	Financial interpretation
Late 1990s	Product launch and adoption in nuclear medicine departments
Early to mid-2000s	Mature revenue contribution from bone-pain palliation
Late 2000s	Increasing pressure from competing pain-control methods and limited oncology differentiation
2010s	Product became a lower-growth or declining asset as newer radiopharmaceuticals entered the market
2020s	Limited public evidence of material branded revenue; value depends on supply and niche clinical demand

Quadramet’s economics were constrained by its operating model. Unlike an ordinary oral drug, the product required isotope production, radiolabeling, specialized release testing, radioactive shipping, and administration within a narrow time window. Each step reduced inventory flexibility and increased the cost of serving low-volume accounts.

The product also lacked a large repeat-treatment market. Hematologic toxicity can limit retreatment, and many patients with advanced cancer have rapidly changing clinical status. Those factors reduce predictable recurring volume.

Which companies commercialized samarium-153 lexidronam?

Cytogen Corporation was the principal historical U.S. commercial company associated with Quadramet. Commercial rights and supply arrangements also involved CIS Bio International and later nuclear-medicine or specialty-pharmaceutical organizations. The product’s supply chain has therefore been more complex than the ownership of a conventional small-molecule brand.

The relevant value chain includes:

1. Production of enriched or activated samarium-153.
2. Manufacture of the lexidronam chelate and radiolabeling process.
3. Sterile filling and quality release.
4. Distribution through radioactive-material logistics.
5. Administration through hospitals and outpatient nuclear-medicine centers.

A commercial holder must maintain both pharmaceutical compliance and radioactive-material infrastructure. That requirement limits the number of credible suppliers and raises barriers to entry even after ordinary pharmaceutical patent protection expires.

What patents protect samarium-153 lexidronam pentasodium?

The original patent estate was directed primarily to radiolabeled phosphonate compounds, bone-seeking compositions, and methods for using those compounds in skeletal imaging or therapy. The core patent protection for an older product approved in 1997 would normally have expired years ago, including any patent-term adjustment or extension available under U.S. law.

No current U.S. Orange Book patent barrier is known to provide meaningful exclusivity for Quadramet. FDA Orange Book records should be evaluated against the specific product listing and historical NDA status, but an active patent-listed exclusivity position is not the principal commercial issue for this product.[3]

What formulations are protected by samarium-153 patents?

Historical protection generally focused on:

• Samarium-153 complexes with phosphonate ligands.
• Bone-targeting radiopharmaceutical compositions.
• Injectable solutions for intravenous administration.
• Methods for reducing pain associated with osteoblastic bone metastases.
• Manufacturing and radiolabeling processes.

The commercial formulation is an injectable radioactive solution, not a conventional solid oral dosage form. Formulation patents therefore have less standalone value than manufacturing controls, isotope access, validated radiolabeling processes, and regulatory approvals.

How strong is the patent estate for Quadramet?

The patent estate is weak as a current exclusivity mechanism but remains relevant as historical technology. Its practical strength is limited by:

• Expiration of core patent terms.
• Lack of a meaningful current Orange Book barrier.
• Availability of related bone-seeking phosphonate chemistry.
• The ability of competitors to rely on alternative radionuclides or radioligands.
• The greater commercial importance of isotope supply and regulatory compliance.

The most defensible residual intellectual-property positions would relate to process know-how, analytical methods, specific manufacturing controls, or improvements not required to practice the expired core technology. Those positions are difficult to value without reviewing current ownership, prosecution history, and jurisdiction-specific family status.

When did samarium-153 lexidronam lose exclusivity?

Core exclusivity was lost long before the 2020s. Quadramet was approved in 1997, and the ordinary 20-year term for patents filed during its development would generally have ended by the late 2010s or earlier. Any U.S. patent-term extension would have been limited by statutory caps and could not create a modern long-duration monopoly for the product.

FDA regulatory exclusivity was also limited. Quadramet is an older small-molecule radiopharmaceutical, not a biologic. It does not have the 12-year reference-product exclusivity associated with biologics under the Public Health Service Act.

The commercial question is therefore not when a new generic obtained freedom to enter. It is whether a competing supplier can secure radioactive isotope supply, satisfy FDA requirements, establish a compliant radiopharmacy distribution network, and generate sufficient demand.

What is the Orange Book status of Quadramet?

Quadramet’s Orange Book position is not a material source of current market protection. The product’s principal exclusivity period has expired, and historical patent listings do not create a present-day barrier comparable to an active patent estate for a recently approved branded drug.

A potential applicant would still need to address:

• Product quality and sterility.
• Radionuclide identity, purity, and specific activity.
• Radiochemical purity.
• Stability during the product’s short usable life.
• Dosimetry and radiation-safety controls.
• Manufacturing-site registration and inspection.
• Labeling and clinical comparability.

For a radioactive injectable, a follow-on product may face technical and regulatory hurdles that are not captured by a conventional Orange Book patent review.

Are there Paragraph IV challenges to samarium-153 lexidronam?

No prominent recent Paragraph IV litigation has established a material challenge to Quadramet’s U.S. market position. The absence of major recent litigation is consistent with the product’s limited commercial scale and expired core patent position.

A Paragraph IV strategy would have limited economic appeal if:

• The reference product had low annual sales.
• No active blocking patents remained.
• Manufacturing required expensive isotope infrastructure.
• Hospitals had inconsistent demand.
• The product had to be distributed quickly after release.

Generic entry is therefore less likely to follow the standard high-value Hatch-Waxman pattern seen with blockbuster oral drugs.

What patent litigation affects Quadramet?

There is no widely reported current U.S. patent litigation involving Quadramet that materially changes its commercial outlook. Historical disputes, if any, would be less important than current manufacturing and supply arrangements.

The litigation risk profile is low compared with modern oncology products because the product has limited active exclusivity and a smaller revenue pool. Regulatory disputes, manufacturing deficiencies, supply interruptions, and contract issues are more commercially relevant than an active patent battle.

How does Quadramet compare with competing radiopharmaceuticals?

Product	Radionuclide	Primary positioning	Commercial distinction
Quadramet	Samarium-153	Palliation of pain from osteoblastic bone metastases	Older, non-tumor-targeted bone-seeking product
Metastron	Strontium-89	Bone-pain palliation	Older beta-emitting competitor with similar palliative positioning
Xofigo	Radium-223	Metastatic castration-resistant prostate cancer with symptomatic bone metastases	Tumor-disease-specific label and alpha-particle positioning
Pluvicto	Lutetium-177	PSMA-positive metastatic castration-resistant prostate cancer	Tumor-targeted radioligand therapy with systemic oncology positioning

Quadramet versus Xofigo

Xofigo changed the commercial benchmark by combining bone localization with a prostate-cancer-specific oncology indication. It is not simply a pain-control product. Its development program and label support a disease-directed treatment strategy, while Quadramet is primarily palliative.

Quadramet may retain clinical utility where rapid pain relief is the treatment objective, particularly when a patient is not an appropriate candidate for a newer targeted agent. Its lower level of clinical differentiation limits pricing power.

Quadramet versus Pluvicto

Pluvicto targets prostate-specific membrane antigen and is designed to deliver radiation to PSMA-expressing tumor cells. Quadramet localizes to areas of abnormal bone formation. The products therefore address different biological targets and have different regulatory, clinical, and commercial profiles.

Pluvicto’s market is supported by biomarker testing, oncology treatment sequencing, and high-value systemic therapy economics. Quadramet relies more heavily on radiopharmacy access and symptom-management demand.

What generic entry risks exist for samarium-153 lexidronam?

Generic or alternative-source entry risk is technically possible but commercially moderate rather than high. The key barriers are operational:

Manufacturing and supply barriers

Samarium-153 is a radioactive isotope with a short half-life. A supplier must coordinate isotope availability and product release close to the date of administration. A manufacturing failure can destroy inventory value quickly.

The supplier must also validate:

• Sterile injectable manufacturing.
• Radionuclide purity.
• Chelation and labeling consistency.
• Dose calibration.
• Container closure integrity.
• Shipping procedures for radioactive material.
• Product release within the usable time window.

Market barriers

A follow-on supplier would face a limited addressable market, entrenched hospital purchasing practices, and competition from non-radiopharmaceutical pain-management options. These factors reduce the expected return on a new manufacturing investment.

The likely launch model would be regional or contract-based rather than a broad national rollout. Radiopharmacy distribution density would determine commercial viability.

What is the FDA regulatory status of Quadramet?

Quadramet is an FDA-approved radiopharmaceutical product. Its regulatory profile is that of an older radioactive injectable approved for pain palliation in osteoblastic metastatic bone disease.

The key FDA requirements relate to product quality, dosing accuracy, radiation safety, hematologic monitoring, and control of radioactive impurities. A product can have expired patents and still face substantial FDA and manufacturing barriers.

The market should distinguish between:

• FDA approval of the reference product.
• Commercial availability at a given time.
• Active marketing by a current rights holder.
• Availability of a substitutable generic product.
• Availability of alternative radiopharmaceutical treatments.

Those categories are not interchangeable.

Are biosimilar risks relevant to samarium-153 lexidronam?

Biosimilar risk is not relevant because samarium-153 lexidronam is a small-molecule radiopharmaceutical, not a biologic. A competing product would be evaluated through a drug or radiopharmaceutical pathway, not the biosimilar pathway under section 351(k) of the Public Health Service Act.

The relevant competitive risks are generic, hybrid, or alternative radiopharmaceutical products. Radium-223 and lutetium-177 agents are not direct biosimilar substitutes and are not necessarily interchangeable with Quadramet.

What licensing deals affect the product?

The product’s commercial history involved licensing and commercialization relationships between the original developers, nuclear-medicine suppliers, and specialty pharmaceutical companies. Those arrangements were important because the product required specialized isotope production and distribution rather than ordinary wholesale pharmaceutical infrastructure.

The economic value of any remaining license would depend on:

• Geographic rights.
• Control of the NDA or marketing authorization.
• Isotope supply commitments.
• Manufacturing responsibilities.
• Minimum purchase obligations.
• Hospital and radiopharmacy contracts.
• Rights to process improvements and regulatory filings.

No current public licensing arrangement provides evidence of a large growth platform for Quadramet. The product is more likely to be managed as a portfolio or supply asset than as a primary growth driver.

What is the geographic coverage of samarium-153 lexidronam?

Quadramet historically had regulatory and commercial exposure in the United States and Europe. Geographic demand is constrained by the availability of nuclear-medicine centers, isotope supply, radioactive-material transport, local reimbursement, and national authorization status.

The addressable market is strongest in countries with:

• Established therapeutic nuclear-medicine departments.
• Reliable medical-isotope supply.
• Reimbursement for radiopharmaceutical palliation.
• Centralized oncology referral networks.
• Licensed radioactive-material transport.

It is weaker in markets where radiopharmacy capacity is limited or oncology care is concentrated in facilities without therapeutic radionuclide services.

What generic launch scenarios are plausible?

Three launch scenarios are commercially plausible:

Scenario	Probability profile	Market effect
No broad follow-on launch	Most consistent with limited market size	Existing supply remains fragmented or intermittent
Regional specialty launch	Plausible where isotope supply and radiopharmacy networks already exist	Moderate price pressure and improved availability
National generic launch	Less attractive economically	Requires reliable isotope access and sufficient recurring volume

A successful entrant would probably compete on supply reliability, hospital contracting, and price rather than on meaningful clinical differentiation.

Key Takeaways

• Samarium-153 lexidronam pentasodium, marketed as Quadramet, is an older FDA-approved palliative radiopharmaceutical.
• Its core patent and regulatory exclusivity periods have expired or no longer provide meaningful commercial protection.
• Current value is constrained by low market growth, short isotope half-life, marrow toxicity, and specialized manufacturing.
• Public filings historically showed material sales contributions during Cytogen’s commercial period, but recent standalone revenue data are not publicly established.
• Xofigo and Pluvicto have shifted nuclear-oncology investment toward disease-specific and tumor-targeted radiopharmaceuticals.
• Biosimilar risk does not apply. Generic and alternative-source risks depend mainly on manufacturing and supply economics.
• The strongest residual barriers are isotope access, validated radiolabeling, sterile manufacturing, radioactive logistics, and regulatory compliance.
• Quadramet is more likely to remain a niche supply asset than a significant branded-growth product.

FAQs

Is Quadramet still commercially available?

Availability depends on the current supplier, country, and radiopharmacy network. FDA approval and commercial availability are separate issues, and public records do not establish a broad current U.S. commercial footprint.

Is samarium-153 lexidronam a targeted cancer therapy?

It is bone-seeking rather than tumor-antigen-targeted. The compound localizes to areas of increased osteoblastic activity but is primarily used for pain palliation.

Can a generic company launch samarium-153 lexidronam?

A follow-on launch is technically possible, but the supplier would need validated sterile radiopharmaceutical manufacturing, isotope access, radioactive shipping capability, and sufficient recurring demand.

Does Quadramet compete directly with Pluvicto?

No. Quadramet targets osteoblastic bone activity for palliation, while Pluvicto targets PSMA-positive cancer cells. They may be used in overlapping prostate-cancer populations but have different treatment objectives.

What is the main investment risk for samarium-153 lexidronam?

The principal risk is market erosion rather than patent litigation. Demand is limited, supply is operationally complex, and newer radioligand therapies have stronger disease-directed value propositions.

References

1. U.S. Food and Drug Administration. (1997). Quadramet (samarium Sm-153 lexidronam injection) prescribing information.
2. Cytogen Corporation. (2007). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission.
3. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
4. National Cancer Institute. (n.d.). Samarium Sm 153 lexidronam. NCI Drug Dictionary.
5. U.S. Food and Drug Administration. (2013). Xofigo approval announcement and prescribing information.
6. U.S. Food and Drug Administration. (2022). Pluvicto approval announcement and prescribing information.