Investigational Drug Information for Darinaparsin

What is the drug development status for Darinaparsin?

Darinaparsin is an investigational drug.

There have been 12 clinical trials for Darinaparsin. The most recent clinical trial was a Phase 2 trial, which was initiated on March 25^th 2016.

The most common disease conditions in clinical trials are Lymphoma, Neoplasms, and Lymphoma, T-Cell, Peripheral. The leading clinical trial sponsors are Ziopharm, Solasia Pharma K.K., and Synex Consulting Korea Ltd.

Summary for Darinaparsin

US Patents	0
International Patents	0
US Patent Applications	404
WIPO Patent Applications	351
Japanese Patent Applications	31
Clinical Trial Progress	Phase 2 (2016-03-25)
Vendors	27

Recent Clinical Trials for Darinaparsin

Title	Sponsor	Phase
A Phase 2 Study of SP-02L in Patients With Relapsed or Refractory Peripheral T-cell Lymphoma (PTCL)	Solasia Pharma K.K.	Phase 2
A Phase 1 Study of SP-02L in Relapsed or Refractory Patients With Peripheral T-cell Lymphoma (PTCL) in Korea	Synex Consulting Korea Ltd.	Phase 1
A Phase 1 Study of SP-02L in Relapsed or Refractory Patients With Peripheral T-cell Lymphoma (PTCL) in Korea	Solasia Pharma K.K.	Phase 1

See all Darinaparsin clinical trials

Clinical Trial Summary for Darinaparsin

Top disease conditions for Darinaparsin

Top clinical trial sponsors for Darinaparsin

See all Darinaparsin clinical trials

US Patents for Darinaparsin

Drugname	Patent Number	Patent Title	Patent Assignee	Estimated Expiration

Darinaparsin Development Update and Market Projection

Last updated: September 4, 2026

Darinaparsin is an investigational intravenous organic arsenic compound for relapsed or refractory peripheral T-cell lymphoma (PTCL) and other hematologic malignancies. Its development has not produced an FDA-approved product, a marketed brand, or an active Orange Book listing. Publicly visible clinical development has remained limited after Phase 2 studies, making regulatory timing and commercial launch uncertain. If a pivotal trial were restarted and succeeded, a focused PTCL launch could support peak U.S. sales in the approximate range of $100 million to $300 million, with upside from broader lymphoma indications.

What is darinaparsin and how does it work?

Darinaparsin is a glutathione-conjugated organic arsenical. The compound was designed to retain antitumor activity associated with arsenic agents while improving the pharmacologic profile relative to inorganic arsenic trioxide.

Preclinical studies indicate that darinaparsin:

• Enters malignant cells through glutathione-related transport pathways.
• Disrupts mitochondrial function.
• Increases oxidative stress.
• Promotes apoptosis.
• May inhibit signaling pathways associated with lymphoma-cell survival.

The product has been studied primarily as an intravenous therapy for patients with relapsed or refractory lymphoma. Its development rationale is strongest in PTCL, an aggressive group of mature T-cell lymphomas with limited treatment options after first-line therapy.

Darinaparsin is distinct from arsenic trioxide, which is approved in the United States for acute promyelocytic leukemia. Arsenic trioxide has a different regulatory history, dosing framework, and clinical positioning.

What is the current development status of darinaparsin?

Darinaparsin has reached Phase 2 clinical development but has not completed a publicly established pivotal registration program. The principal development focus has been relapsed or refractory PTCL.

Public clinical records and company disclosures indicate the following development profile:

Development item	Status
Active ingredient	Darinaparsin, an organic arsenic-glutathione conjugate
Primary target indication	Relapsed or refractory PTCL
Route of administration	Intravenous
Clinical stage reached	Phase 2
FDA approval	None identified
U.S. brand launch	None
Orange Book listing	None
Biosimilar pathway	Not applicable
Generic pathway	Not currently relevant because the product is not approved
Pivotal Phase 3 program	No publicly established active program
Current commercial revenue	None from an approved darinaparsin product

A Phase 2 study evaluated darinaparsin in patients with relapsed or refractory lymphoma, including PTCL. Published and company-reported results described antitumor activity in heavily pretreated patients, including objective responses in a minority of participants. The data supported further investigation but did not establish the efficacy package required for approval.

ClinicalTrials.gov records should be reviewed for the latest recruitment, termination, sponsor, and protocol status because trial activity and sponsor ownership can change after the last public corporate update. The available development record does not show a completed confirmatory program that has led to an FDA filing.[1]

What clinical evidence supports darinaparsin?

The clinical evidence is preliminary and concentrated in late-line disease. This limits direct comparison with approved PTCL therapies, which have more mature response, duration-of-response, safety, and survival datasets.

The main development questions are:

1. Whether darinaparsin produces durable responses rather than short-lived tumor reductions.
2. Whether its safety profile is meaningfully better than existing single-agent therapies.
3. Whether it can be combined with chemotherapy, epigenetic agents, antibody-drug conjugates, or immune therapies.
4. Whether a registrational study can recruit enough patients in a rare and biologically heterogeneous disease.

The most relevant clinical benchmark is the response rate achieved by approved or previously approved agents in relapsed PTCL. Brentuximab vedotin has a strong position in CD30-positive disease, while romidepsin, belinostat, and pralatrexate have established historical use in broader relapsed PTCL populations. Darinaparsin would need either superior durability, a differentiated safety profile, activity in treatment-resistant subgroups, or a combination strategy to support premium positioning.

Darinaparsin’s organic arsenic structure could create a commercial distinction from arsenic trioxide, but the distinction must translate into clinically meaningful benefits. A mechanistic difference alone is unlikely to support approval or reimbursement.

What is the FDA regulatory status of darinaparsin?

Darinaparsin is not FDA-approved. No New Drug Application approval, commercial label, or postmarketing safety database has been identified for the product.

The development program has been associated with FDA orphan-drug and expedited-development concepts for rare lymphoma indications. Orphan designation, fast-track interaction, or other FDA designations do not establish approval and do not eliminate the need for adequate and well-controlled clinical studies.

The likely regulatory path would require:

• A defined target population, most likely relapsed or refractory PTCL.
• A registrational trial with an endpoint acceptable to FDA.
• A validated manufacturing process for the arsenic-containing conjugate.
• Detailed characterization of arsenic exposure and tissue distribution.
• A risk-management plan addressing hematologic, hepatic, cardiac, neurologic, and systemic toxicity.
• Long-term safety follow-up.

An accelerated-approval strategy could be considered if the sponsor generated a substantial response signal in a serious disease with unmet need and used a response endpoint reasonably likely to predict clinical benefit. Such a strategy would require confirmatory evidence after approval.

What is the Orange Book status of darinaparsin?

Darinaparsin has no identified Orange Book listing because no FDA-approved product has been marketed in the United States.

The absence of an Orange Book entry means:

• There are no listed patents that an ANDA applicant must certify against.
• There is no statutory small-molecule exclusivity period running from an approved product.
• A Paragraph IV challenge cannot be filed against a listed darinaparsin product.
• Any future generic or 505(b)(2) dispute would depend on patents, regulatory exclusivity, and the eventual FDA reference product.

If darinaparsin were approved, the sponsor could seek five years of new chemical entity exclusivity if FDA classified the active ingredient as a new chemical entity. Orphan-drug exclusivity could provide seven years for the approved orphan indication under the Orphan Drug Act.[2]

What patents protect darinaparsin?

The public development history indicates that intellectual-property protection has focused on the compound, arsenic-glutathione chemistry, pharmaceutical compositions, and oncology uses. The practical value of those rights depends on claim scope, ownership transfers, terminal disclaimers, continuation practice, and remaining patent term.

No Orange Book patent estate currently protects a marketed darinaparsin product. Patent risk should therefore be separated into two categories:

Patent category	Commercial relevance
Compound patents	Could block manufacture of the specific darinaparsin molecule or closely related compounds
Composition patents	Could protect injectable formulations, concentrations, stabilizers, or dosing formats
Method-of-use patents	Could cover PTCL, lymphoma subtypes, combinations, or dosing schedules
Manufacturing patents	Could create barriers around synthesis, purification, arsenic control, or conjugation
Regulatory exclusivity	Could protect an approved indication even if patent coverage is weak
Trade secrets	Could protect process parameters not disclosed in patent claims

For a future license or acquisition, the decisive diligence issues would be the chain of title, expiration dates, maintenance-fee status, surviving claims after prosecution, and freedom to operate against arsenic-containing oncology compounds. Patent protection should not be inferred from the existence of clinical development alone.

Because the product is not approved, patent expiry does not currently determine generic launch timing. A future launch could be constrained more by clinical redevelopment, manufacturing validation, and regulatory exclusivity than by an Orange Book Paragraph IV dispute.

When could darinaparsin lose exclusivity?

Darinaparsin has no current U.S. market exclusivity because it has not received FDA approval.

If approved in the future, the likely exclusivity framework would include:

Protection	Potential duration
New chemical entity exclusivity	Five years
Orphan-drug exclusivity	Seven years for the approved orphan indication
Patent term	Depends on issued claims and patent expiration
Patent-term restoration	Potentially up to five years, subject to statutory limits
Pediatric exclusivity	Six additional months if applicable

Orphan exclusivity would apply to the same drug for the same indication, but it would not necessarily block all development of a different drug for the same disease. Patent protection could extend beyond regulatory exclusivity if valid claims remain in force.

How does darinaparsin compare with competing PTCL drugs?

Darinaparsin would enter a market with established single-agent and combination therapies.

Drug	Company or originator	Main PTCL relevance	Commercial position
Brentuximab vedotin	Seagen/Pfizer	CD30-positive PTCL and systemic anaplastic large-cell lymphoma	Strongest targeted position in CD30-positive disease
Romidepsin	Bristol Myers Squibb originator	Relapsed PTCL	Historical activity; U.S. PTCL indication later withdrawn
Belinostat	Spectrum Pharmaceuticals	Relapsed or refractory PTCL	Approved option with differentiated histone deacetylase inhibition
Pralatrexate	Acrotech	Relapsed or refractory PTCL	Established antifolate option
Mogamulizumab	Kyowa Kirin	Adult T-cell leukemia/lymphoma and cutaneous T-cell lymphoma	Important in selected T-cell malignancies
Duvelisib	Secura Bio originator	T-cell lymphoma development history	Regulatory and commercial use has been limited
Darinaparsin	Investigational	Relapsed or refractory PTCL	No approved-market position

Darinaparsin’s opportunity is greatest in patients who have failed brentuximab, chemotherapy, or epigenetic therapy, particularly when transplantation or cellular therapy is not feasible. Its disadvantage is the lack of a validated biomarker and the need to compete against drugs with existing clinical adoption.

What patent litigation and Paragraph IV risks affect darinaparsin?

No material public patent litigation involving an approved darinaparsin product or an ANDA Paragraph IV challenge has been identified. That outcome is expected because the product has no FDA-approved reference listing.

Future litigation risks would most likely involve:

• Ownership disputes over foundational compound patents.
• Challenges to method-of-use claims.
• Patent scope covering arsenic-glutathione conjugates.
• Manufacturing-process claims.
• A 505(b)(2) applicant attempting to rely on published clinical data.
• Competing sponsors seeking to invalidate or design around formulation claims.

The absence of current litigation is not evidence that the intellectual-property position is strong. It primarily reflects the absence of a commercial product and generic filing opportunity.

What manufacturing and intellectual-property barriers exist?

Arsenic-containing injectable products require tight control of identity, purity, arsenic species, residual impurities, and batch consistency. Manufacturing risks include:

• Reproducible formation of the arsenic-glutathione conjugate.
• Control of free arsenic and degradation products.
• Stability during storage and infusion.
• Container-closure compatibility.
• Scalable purification.
• Worker and environmental exposure controls.
• Analytical methods capable of distinguishing active conjugate from related arsenic species.

These issues could raise the cost and time required for commercial development. They may also create process patents or trade-secret barriers that are more important than composition patents after the core compound claims expire.

What is the market size and revenue potential for darinaparsin?

The initial commercial market would be narrow. PTCL is a rare disease, and only a subset of patients receive multiple lines of systemic treatment. The addressable U.S. population for an approved relapsed or refractory PTCL therapy could plausibly fall in the low thousands annually, depending on the label and treatment setting.

A scenario-based projection is more appropriate than a conventional consensus forecast because darinaparsin has no approved label, launch date, price, or active pivotal program.

Scenario	Annual treated patients	Net annual treatment value	Peak U.S. revenue
Limited niche adoption	500-800	$75,000-$100,000	$40 million-$80 million
Base case	1,000-1,500	$100,000-$150,000	$100 million-$225 million
Broad adoption or expanded label	1,500-2,500	$125,000-$175,000	$190 million-$440 million

These figures are scenario estimates, not company guidance. They assume an orphan oncology pricing framework, payer discounts, and treatment concentrated in relapsed or refractory disease.

The base case is the most commercially defensible only if darinaparsin demonstrates durable responses, receives an orphan indication, and gains access to patients after established targeted therapies. A combination indication or expansion into other lymphomas could materially increase the opportunity. A weak response duration, significant arsenic-related toxicity, or manufacturing delays would reduce uptake.

Which companies are challenging or developing darinaparsin?

No active generic challenger has a commercial incentive to file an ANDA before FDA approval. The development history has involved smaller biotechnology and specialty-pharmaceutical interests rather than a major pharmaceutical launch platform.

The competitive threat comes from alternative therapies, not generic substitution. Companies active in the broader PTCL market include Pfizer through the Seagen acquisition, Acrotech Biopharma, Kyowa Kirin, and developers of cellular therapies, bispecific antibodies, antibody-drug conjugates, and epigenetic combinations.

A future partnership with a specialty oncology company would likely be required for late-stage development, regulatory filing, manufacturing scale-up, and commercialization.

What is the likely development outlook?

The near-term outlook is constrained by the absence of a visible pivotal trial and the lack of an approved product. The asset retains potential because PTCL has limited treatment options, but the program requires a clear development restart.

The most credible value-creation path would be:

1. Select a biomarker-defined or clinically coherent PTCL population.
2. Reconfirm Phase 2 efficacy and safety using contemporary response criteria.
3. Establish a dose and schedule that minimizes arsenic-related toxicity.
4. Develop a registrational strategy with FDA.
5. Generate manufacturing comparability and long-term stability data.
6. Seek orphan designation and, if justified, an accelerated approval pathway.
7. Use a specialty oncology partner for launch execution.

Without a new sponsor, pivotal trial, or regulatory filing, darinaparsin should be treated as a dormant or pre-commercial asset rather than a near-term revenue product.

Key Takeaways

• Darinaparsin is an investigational organic arsenic-glutathione conjugate for relapsed or refractory PTCL.
• The product has reached Phase 2 but has no FDA approval, U.S. brand, Orange Book listing, or commercial revenue.
• Clinical evidence shows preliminary activity but does not establish a registration-ready efficacy package.
• There is no current Paragraph IV or generic-launch event tied to darinaparsin.
• Future value depends on a development restart, pivotal evidence, manufacturing control, and a credible safety profile.
• Estimated peak U.S. revenue is approximately $100 million to $300 million in a successful focused PTCL launch, with broader upside only through additional indications.
• The primary competitive risk comes from approved PTCL therapies and emerging targeted or cellular treatments, not from generic substitution.

FAQs About Darinaparsin

Is darinaparsin approved by the FDA?

No. Darinaparsin has not received FDA approval and has no marketed U.S. product.

Is darinaparsin the same as arsenic trioxide?

No. Darinaparsin is an organic arsenic-glutathione conjugate. Arsenic trioxide is an inorganic arsenic drug approved primarily for acute promyelocytic leukemia.

Can a generic company file a Paragraph IV challenge against darinaparsin?

Not currently. A Paragraph IV certification requires an approved reference product with listed patents. Darinaparsin has no identified Orange Book-listed reference product.

What cancer is darinaparsin being developed to treat?

The principal target is relapsed or refractory peripheral T-cell lymphoma. Other lymphoma applications have been studied or considered, but no expanded approved indication exists.

What would make darinaparsin commercially viable?

A registrationally meaningful response rate, durable disease control, manageable arsenic-related toxicity, reliable injectable manufacturing, orphan-drug protection, and a specialty oncology commercialization partner would be required.

References

1. ClinicalTrials.gov. (n.d.). Darinaparsin clinical studies. U.S. National Library of Medicine. https://clinicaltrials.gov/

2. U.S. Food and Drug Administration. (n.d.). Orphan drug designation and exclusivity. https://www.fda.gov/industry/developing-products-rare-diseases-conditions/designating-orphan-product-drugs-and-biological-products

3. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book

4. O'Connor, O. A., Pro, B., Pinter-Brown, L., Bartlett, N., Jacobsen, E., Shustov, A., Advani, R., Ruan, J., Goy, A., Buske, C., & others. (2011). A phase 2 study of darinaparsin in relapsed or refractory lymphoma. Clinical Cancer Research, 17(3), 776-783.

5. National Comprehensive Cancer Network. (2024). NCCN clinical practice guidelines in oncology: T-cell lymphomas. NCCN.