Investigational Drug Information for Valopicitabine

What is the development status for investigational drug Valopicitabine?

Valopicitabine is an investigational drug.

There have been 4 clinical trials for Valopicitabine. The most recent clinical trial was a Phase 2 trial, which was initiated on August 1^st 2005.

The most common disease conditions in clinical trials are Hepatitis, Hepatitis, Chronic, and Hepatitis C, Chronic. The leading clinical trial sponsors are Merck Sharp & Dohme Corp., Novartis Pharmaceuticals, and [disabled in preview].

Summary for Valopicitabine

US Patents	0
International Patents	0
US Patent Applications	604
WIPO Patent Applications	292
Japanese Patent Applications	183
Clinical Trial Progress	Phase 2 (2005-08-01)
Vendors	16

Recent Clinical Trials for Valopicitabine

Title	Sponsor	Phase
Study to Evaluate Drug-drug Interaction Between Valopicitabine and Ribavirin	Novartis Pharmaceuticals	Phase 2
Study to Evaluate Drug-drug Interaction Between Valopicitabine and Ribavirin	Merck Sharp & Dohme Corp.	Phase 2
A Study to Evaluate the Combination of Pegylated Interferon Alfa Plus Valopicitabine in Patients With Hepatitis C	Merck Sharp & Dohme Corp.	Phase 2

See all Valopicitabine clinical trials

Clinical Trial Summary for Valopicitabine

Top disease conditions for Valopicitabine

Top clinical trial sponsors for Valopicitabine

See all Valopicitabine clinical trials

US Patents for Valopicitabine

Drugname	Patent Number	Patent Title	Patent Assignee	Estimated Expiration

Valopicitabine Development Update and Market Projection

Last updated: September 9, 2026

Valopicitabine, also known as NM283, is a discontinued oral investigational hepatitis C virus polymerase inhibitor developed by Idenix Pharmaceuticals. Its active metabolite was 2'-C-methylcytidine. Development stopped after Phase 2 studies because of gastrointestinal toxicity, including clinically significant nausea, vomiting, and diarrhea, combined with insufficient efficacy at tolerable doses. Valopicitabine has no FDA approval, no Orange Book listing, no commercial sales, and no credible pathway to market entry under the historical program.

The base-case market projection is therefore zero revenue from valopicitabine. Any future value would require a new development program, new clinical evidence, regulatory re-engagement, and likely a reformulation or redesigned dosing strategy.

What is the current development status of valopicitabine?

Valopicitabine is no longer an active clinical-stage drug candidate. Idenix discontinued its development for chronic hepatitis C after Phase 2b testing. The program was not advanced into a registrational Phase 3 trial, and no subsequent sponsor has restarted development.

Attribute	Valopicitabine status
Generic name	Valopicitabine
Development code	NM283
Parent company	Idenix Pharmaceuticals
Therapeutic area	Chronic hepatitis C
Drug class	Nucleoside analog HCV RNA polymerase inhibitor
Active metabolite	2'-C-methylcytidine
Route	Oral
Development stage reached	Phase 2b
FDA approval	None
Commercial launch	None
Orange Book listing	None
Current clinical development	Discontinued
Current revenue	None

Valopicitabine was designed as an oral nucleotide or nucleoside-based direct-acting antiviral. It targeted the HCV NS5B RNA-dependent RNA polymerase, an enzyme later exploited successfully by approved medicines such as sofosbuvir.

Why was valopicitabine development discontinued?

The primary development problems were tolerability and dose limitations. Clinical studies reported substantial gastrointestinal adverse events, particularly nausea, vomiting, and diarrhea. These events limited the ability to maintain exposure at doses that could deliver sufficient antiviral activity.

The candidate also produced incomplete viral suppression when used in interferon-based treatment regimens. Idenix ultimately stopped development after concluding that the benefit-risk profile did not support continued advancement. Public company disclosures described the decision in the context of adverse events and inadequate efficacy at tolerable doses (Idenix Pharmaceuticals, 2007).

The failure was commercially significant because the HCV market was moving toward all-oral combination therapy. A drug that required difficult dose management or caused frequent gastrointestinal toxicity had limited competitiveness against better-tolerated direct-acting antivirals.

What clinical trials evaluated valopicitabine?

Valopicitabine was studied mainly in treatment-experienced and treatment-naive patients with chronic HCV infection, including patients receiving pegylated interferon and ribavirin.

Development timeline

Period	Development event
Early 2000s	Idenix advances NM283 as an oral HCV polymerase inhibitor
2004-2005	Early clinical studies evaluate antiviral activity and tolerability
2006	Phase 2 studies assess valopicitabine with pegylated interferon and ribavirin
2006-2007	Gastrointestinal adverse events constrain dosing and treatment continuation
2007	Idenix discontinues valopicitabine development
2014	Merck acquires Idenix and its HCV-related assets, but valopicitabine does not return to clinical development
Current status	No active sponsor, no commercial product, and no clinical restart

The program’s clinical failure occurred before the modern HCV cure market was established. Sofosbuvir, ledipasvir, ombitasvir, paritaprevir, dasabuvir, grazoprevir, elbasvir, glecaprevir, and pibrentasvir later demonstrated that short-course, interferon-free regimens could achieve high sustained virologic response rates with substantially better tolerability.

What patents protect valopicitabine?

The historical patent estate covered valopicitabine, related 2'-methyl nucleoside compounds, pharmaceutical compositions, and methods for treating HCV infection. Those rights were associated with Idenix and its predecessor research programs.

The practical patent position has little commercial significance today:

• Valopicitabine was never approved, so it has no Orange Book-listed patents.
• The principal composition-of-matter and use patents were filed during the early development period.
• Any relevant U.S. patent terms would generally have been tied to filing dates in the late 1990s or early 2000s and are now expired or approaching the end of their statutory terms.
• No active commercial product creates a current patent-litigation or Paragraph IV market-entry event.
• Patent families may still contain jurisdiction-specific rights, terminal disclaimers, continuations, or abandoned applications, but those rights do not create a meaningful launch barrier for an unapproved discontinued molecule.

What formulations are protected by valopicitabine patents?

The historical formulation work focused on oral dosage forms capable of delivering valopicitabine or its nucleoside analog activity. There is no approved tablet, capsule, injectable, long-acting formulation, or combination product.

No formulation patent currently supports a marketed valopicitabine product. Any future developer would probably need to address exposure, gastrointestinal tolerability, and dose optimization through new formulation or prodrug work rather than rely on the historical clinical formulation.

What is the FDA regulatory status of valopicitabine?

Valopicitabine is not FDA-approved and is not listed in Drugs@FDA as an approved drug. It has no New Drug Application approval, no approved labeling, and no FDA-recognized exclusivity period (U.S. Food and Drug Administration, n.d.-a).

Regulatory status summary

FDA category	Status
Approved indication	None
NDA	No approval
Biologic license	Not applicable
Orphan-drug designation	No commercially relevant designation identified
New chemical entity exclusivity	None granted
Pediatric exclusivity	None
Qualified infectious-disease product exclusivity	None
Orange Book patent listing	None
Generic approval pathway	Not available because there is no reference listed drug

Because valopicitabine never received approval, it cannot be challenged through the normal Abbreviated New Drug Application and Paragraph IV process. A generic manufacturer would not have a reference product against which to file a conventional ANDA.

When does valopicitabine lose exclusivity?

Valopicitabine has no current regulatory exclusivity to lose. Its development program ended before approval, so it never received FDA market exclusivity.

Historical patent protection may have expired under ordinary U.S. patent-term rules. The relevant date depends on the specific patent family, priority claim, patent term adjustment, terminal disclaimer, and jurisdiction. That distinction has limited commercial importance because the molecule has no approved reference product and no active clinical sponsor.

Are generic or biosimilar challenges possible?

Traditional generic competition is not an immediate issue. Valopicitabine is a small molecule, so biosimilar regulation does not apply. A competitor seeking to develop the compound would need to pursue an independent clinical and regulatory program, not a routine biosimilar application.

Potential competitors would face the following barriers:

1. Re-establishing an acceptable safety profile.
2. Demonstrating clinically meaningful antiviral activity in modern HCV regimens.
3. Showing value against highly effective approved direct-acting antivirals.
4. Funding new toxicology, pharmacokinetic, dose-ranging, and combination studies.
5. Establishing commercial differentiation in a curative market.

These barriers are greater than the remaining patent barriers.

What is the market projection for valopicitabine?

The base-case commercial projection is zero.

Projection period	Expected valopicitabine revenue	Rationale
Current period	$0	No approval, no launch, no sponsor
Near term	$0	No active development or regulatory filing
Medium term	$0	Restart would require a new clinical program
Long term base case	$0	HCV market is mature and highly competitive
Speculative relaunch case	Unquantifiable	No public development plan or valuation basis

The broader HCV market remains commercially meaningful, but it is no longer a favorable market for a discontinued nucleoside candidate with known tolerability problems. Approved direct-acting antiviral regimens commonly achieve cure rates above 95% in appropriate patients and have established treatment algorithms. This leaves little room for a standalone product that offers no documented advantage in efficacy, resistance profile, duration, safety, price, or access.

What would be required for a commercial relaunch?

A relaunch would require:

• A new sponsor with rights to the relevant intellectual property or a redesigned molecule.
• Modern preclinical safety studies.
• A new Phase 1 program to characterize exposure and gastrointestinal tolerability.
• Combination studies with current HCV antivirals.
• A registrational strategy supported by sustained virologic response data.
• A clear target population, such as resistant or difficult-to-treat infection.
• Pricing and access evidence against low-cost generic HCV regimens.
• New manufacturing and quality-control validation.

The economic case is weak. A new candidate would need to displace established curative therapies rather than fill a large untreated therapeutic gap.

How does valopicitabine compare with approved HCV drugs?

Product or candidate	Mechanism	Development or market status	Commercial assessment
Valopicitabine	Nucleoside NS5B polymerase inhibitor	Discontinued in Phase 2	No revenue opportunity under current program
Sofosbuvir	Nucleotide NS5B inhibitor	Approved	Established high-efficacy therapy; generic competition in some markets
Ledipasvir/sofosbuvir	NS5A plus NS5B inhibition	Approved	Historically major commercial product
Glecaprevir/pibrentasvir	NS3/4A plus NS5A inhibition	Approved	Broad genotype coverage and short-course treatment
Elbasvir/grazoprevir	NS5A plus NS3/4A inhibition	Approved	Narrower commercial position
Pibrentasvir-containing regimens	NS5A inhibition	Approved in combinations	Strong resistance and genotype coverage

Valopicitabine’s mechanism was scientifically relevant, but mechanism alone did not produce a viable product. The compound lacked the clinical tolerability and development timing needed to compete with later combination regimens.

What patent litigation and licensing deals affect valopicitabine?

No active patent litigation, Paragraph IV case, or settlement agreement is associated with a current valopicitabine launch because there is no approved product or active commercialization program.

Idenix was acquired by Merck in 2014 for approximately $3.85 billion, primarily to obtain Idenix’s HCV portfolio and drug-discovery capabilities. The transaction did not reactivate valopicitabine. Merck’s later HCV commercial strategy centered on other assets, including grazoprevir and elbasvir, rather than NM283 (Merck & Co., 2014).

No current licensing arrangement provides a visible route for valopicitabine commercialization.

How strong is the valopicitabine patent estate?

The patent estate is historically relevant but commercially weak.

Its strengths were the early filing position around 2'-methyl nucleoside chemistry and the potential breadth of composition and therapeutic-use claims. Its weaknesses are more decisive:

• No approved product generates protected sales.
• Historical patent terms are largely exhausted or near exhaustion.
• Clinical liabilities cannot be solved through patent rights.
• The HCV market has moved beyond interferon-based treatment.
• Competitors have established combination regimens and treatment guidelines.
• A new sponsor would likely need new formulation, dosing, or combination inventions.

The principal barrier is development risk, not freedom to operate against a live branded product.

Key Takeaways

• Valopicitabine, or NM283, is a discontinued Idenix HCV drug candidate.
• Development ended after Phase 2 because of gastrointestinal toxicity and inadequate efficacy at tolerable doses.
• The candidate has no FDA approval, Orange Book listing, commercial sales, or regulatory exclusivity.
• Paragraph IV litigation and biosimilar competition are not applicable.
• Historical composition and use patents do not support a meaningful current commercial barrier.
• Merck acquired Idenix in 2014, but valopicitabine was not revived.
• The base-case market projection is zero revenue.
• Any future value would depend on a new molecule, formulation, or clinical strategy, not simple commercialization of the historical candidate.

FAQs

Is valopicitabine still being developed?

No. Public development ended after Phase 2, and no active sponsor or clinical restart has been established.

Was valopicitabine approved by the FDA?

No. Valopicitabine never received FDA approval and has no FDA-approved indication.

Is valopicitabine a direct-acting antiviral?

Yes. It was an oral nucleoside analog designed to inhibit the HCV NS5B RNA polymerase.

Can a generic company launch valopicitabine?

Not through a conventional ANDA pathway because no FDA-approved reference listed drug exists. A company would need to pursue an independent drug-development and approval program.

Does valopicitabine have residual licensing value?

The residual value is low under the base case. Historical intellectual property may have technical or research value, but there is no evident commercial pathway without new clinical development.

References

1. Idenix Pharmaceuticals, Inc. (2007). Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. U.S. Securities and Exchange Commission.

2. Merck & Co., Inc. (2014). Merck to acquire Idenix Pharmaceuticals. Merck investor relations.

3. U.S. Food and Drug Administration. (n.d.-a). Drugs@FDA: FDA-approved drugs database. https://www.accessdata.fda.gov/scripts/cder/daf/

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

5. ClinicalTrials.gov. (n.d.). Studies of valopicitabine and NM283 for chronic hepatitis C. U.S. National Library of Medicine. https://clinicaltrials.gov/