CLINICAL TRIALS PROFILE FOR DIDANOSINE

505(b)(2) Clinical Trials for didanosine

This table shows clinical trials for potential 505(b)(2) applications. See the next table for all clinical trials

Trial Type	Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
New Combination	NCT00002234 ↗	Safety and Effectiveness of Giving an Anti-HIV Drug Combination of Adefovir Dipivoxil Plus Didanosine Plus Efavirenz Plus Lamivudine Once Daily to HIV-Infected Patients	Completed	Bristol-Myers Squibb	Phase 2	1969-12-31	The purpose of this study is to see if it is safe and effective to give HIV-infected patients a new combination of anti-HIV drugs taken once daily.
New Combination	NCT00002234 ↗	Safety and Effectiveness of Giving an Anti-HIV Drug Combination of Adefovir Dipivoxil Plus Didanosine Plus Efavirenz Plus Lamivudine Once Daily to HIV-Infected Patients	Completed	Dupont Applied Biosciences	Phase 2	1969-12-31	The purpose of this study is to see if it is safe and effective to give HIV-infected patients a new combination of anti-HIV drugs taken once daily.
New Combination	NCT00002234 ↗	Safety and Effectiveness of Giving an Anti-HIV Drug Combination of Adefovir Dipivoxil Plus Didanosine Plus Efavirenz Plus Lamivudine Once Daily to HIV-Infected Patients	Completed	Glaxo Wellcome	Phase 2	1969-12-31	The purpose of this study is to see if it is safe and effective to give HIV-infected patients a new combination of anti-HIV drugs taken once daily.
New Combination	NCT00002234 ↗	Safety and Effectiveness of Giving an Anti-HIV Drug Combination of Adefovir Dipivoxil Plus Didanosine Plus Efavirenz Plus Lamivudine Once Daily to HIV-Infected Patients	Completed	Gilead Sciences	Phase 2	1969-12-31	The purpose of this study is to see if it is safe and effective to give HIV-infected patients a new combination of anti-HIV drugs taken once daily.

All Clinical Trials for didanosine

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00000625 ↗	A Randomized, Double-Blind Phase II/III Trial of Monotherapy vs. Combination Therapy With Nucleoside Analogs in HIV-Infected Persons With CD4 Cells of 200-500/mm3	Completed	Bristol-Myers Squibb	Phase 2	1969-12-31	To determine the efficacy and safety of zidovudine ( AZT ) versus didanosine ( ddI ), AZT plus ddI, and AZT plus zalcitabine ( ddC ) in preventing disease progression in HIV-infected patients with CD4 counts of 200-500 cells/mm3.
NCT00000625 ↗	A Randomized, Double-Blind Phase II/III Trial of Monotherapy vs. Combination Therapy With Nucleoside Analogs in HIV-Infected Persons With CD4 Cells of 200-500/mm3	Completed	Glaxo Wellcome	Phase 2	1969-12-31	To determine the efficacy and safety of zidovudine ( AZT ) versus didanosine ( ddI ), AZT plus ddI, and AZT plus zalcitabine ( ddC ) in preventing disease progression in HIV-infected patients with CD4 counts of 200-500 cells/mm3.
NCT00000625 ↗	A Randomized, Double-Blind Phase II/III Trial of Monotherapy vs. Combination Therapy With Nucleoside Analogs in HIV-Infected Persons With CD4 Cells of 200-500/mm3	Completed	National Institute of Allergy and Infectious Diseases (NIAID)	Phase 2	1969-12-31	To determine the efficacy and safety of zidovudine ( AZT ) versus didanosine ( ddI ), AZT plus ddI, and AZT plus zalcitabine ( ddC ) in preventing disease progression in HIV-infected patients with CD4 counts of 200-500 cells/mm3.
NCT00000637 ↗	A Randomized Comparative Trial of Zidovudine (AZT) Versus 2',3'-Dideoxyinosine (ddI) Versus AZT Plus ddI in Symptomatic HIV-Infected Children	Completed	Bristol-Myers Squibb	Phase 3	1969-12-31	To compare the effectiveness of treatment with zidovudine (AZT) compared to didanosine (ddI) and compared to the combination of AZT and ddI as determined by survival and disease progression. To compare the relative safety and tolerance of AZT versus ddI versus AZT plus ddI in symptomatic HIV infected children; to compare the virological and immunological parameters in the three treatment groups. AZT has been shown to delay the progression of AIDS in HIV infected individuals. However, bone marrow toxicity is a frequent adverse effect. Also, HIV resistance to AZT sometimes occurs in patients who initially respond to treatment, but later have progression of the disease. Thus, new drug treatments are needed. Studies of ddI in adults and children indicate some effectiveness of the drug. A direct comparison of AZT and ddI treatment in children has not been made. Combination antiviral treatment (AZT plus ddI) may give added therapeutic benefit to children.
NCT00000637 ↗	A Randomized Comparative Trial of Zidovudine (AZT) Versus 2',3'-Dideoxyinosine (ddI) Versus AZT Plus ddI in Symptomatic HIV-Infected Children	Completed	Glaxo Wellcome	Phase 3	1969-12-31	To compare the effectiveness of treatment with zidovudine (AZT) compared to didanosine (ddI) and compared to the combination of AZT and ddI as determined by survival and disease progression. To compare the relative safety and tolerance of AZT versus ddI versus AZT plus ddI in symptomatic HIV infected children; to compare the virological and immunological parameters in the three treatment groups. AZT has been shown to delay the progression of AIDS in HIV infected individuals. However, bone marrow toxicity is a frequent adverse effect. Also, HIV resistance to AZT sometimes occurs in patients who initially respond to treatment, but later have progression of the disease. Thus, new drug treatments are needed. Studies of ddI in adults and children indicate some effectiveness of the drug. A direct comparison of AZT and ddI treatment in children has not been made. Combination antiviral treatment (AZT plus ddI) may give added therapeutic benefit to children.

Clinical Trial Conditions for didanosine

Condition Name

Condition Name for didanosine
Intervention	Trials
HIV Infections	144
HIV Infection	4
HIV	3
AIDS	3

Condition MeSH

Condition MeSH for didanosine
Intervention	Trials
HIV Infections	150
Acquired Immunodeficiency Syndrome	40
Infections	37
Infection	35

Clinical Trial Locations for didanosine

Trials by Country

Trials by Country for didanosine
Location	Trials
Puerto Rico	39
Thailand	28
Spain	23
Canada	14
South Africa	10

Trials by US State

Trials by US State for didanosine
Location	Trials
California	92
New York	75
Illinois	61
Florida	57
Massachusetts	54

Clinical Trial Progress for didanosine

Clinical Trial Phase

Clinical Trial Phase for didanosine
Clinical Trial Phase	Trials
Phase 4	13
Phase 3	19
Phase 2/Phase 3	1

Clinical Trial Status

Clinical Trial Status for didanosine
Clinical Trial Phase	Trials
Completed	136
Unknown status	8
Terminated	6

Clinical Trial Sponsors for didanosine

Sponsor Name

Sponsor Name for didanosine
Sponsor	Trials
National Institute of Allergy and Infectious Diseases (NIAID)	81
Bristol-Myers Squibb	45
Glaxo Wellcome	18

Sponsor Type

Sponsor Type for didanosine
Sponsor	Trials
Industry	112
NIH	98
Other	42

Didanosine clinical trials update, market analysis, and exclusivity outlook: trial status, competitive landscape, and commercialization projections

Last updated: May 20, 2026

Executive summary

• Didanosine (ddI) is an older HIV-1 nucleoside reverse transcriptase inhibitor (NRTI) with largely discontinued development activity and minimal late-stage trial pipeline expansion in recent years.
• Commercial impact is constrained by broad replacement with newer antiretroviral classes and fixed-dose, once-daily regimens; remaining use is mainly historical or for specific intolerance/salvage contexts.
• Patent and regulatory exclusivity are no longer the primary gating factor in most jurisdictions; generics and therapeutic substitutes dominate, and new patient uptake depends on guideline position, tolerability, and access rather than new clinical evidence.
• Net market value is expected to remain low and structurally declining, with any short-term variability driven by regional procurement cycles and continued availability of older formulations.

What clinical trials are ongoing for didanosine and what are the latest results?

Featured snippet answer: There is no credible signal of active global phase 3 development for didanosine as a new antiretroviral backbone. Recent visibility is typically limited to legacy pharmacovigilance, historical regimen comparisons, and observational cohorts rather than registrational trials.

Are there any recent phase 3 or phase 2 studies of didanosine?

• Current public trial registries show didanosine studies largely tied to:
  • historical regimen comparisons
  • pharmacokinetics (often in special populations or formulation assessments)
  • safety follow-up cohorts
• No sustained pattern of late-stage (phase 2/3) recruitment or pivotal endpoints consistent with label expansion or new indication submissions is evident from recent trial listing activity.

What are common endpoints used in didanosine studies?

• Viral load suppression (HIV-1 RNA)
• Immunologic response (CD4+ T-cell counts)
• Tolerability and safety endpoints (notably mitochondrial toxicity signals historically associated with ddI class exposure)
• Drug-drug interaction readouts in combination therapy settings (where ddI was used as part of older regimens)

What safety and labeling constraints shape trial conduct and modern uptake?

Didanosine is associated historically with class-limited and ddI-specific adverse events that have shaped its decline in modern practice:

• pancreatitis risk
• lactic acidosis and hepatic steatosis signals
• peripheral neuropathy
• hematologic toxicity These constraints reduce sponsor incentive to run new registrational trials unless used in narrow, guideline-relevant rescue settings.

How strong is the didanosine patent estate and which patents protect it?

Featured snippet answer: Didanosine is an old active ingredient. The relevant protection landscape is dominated by legacy compound patents and formulation or process patents rather than any broad, enforceable modern estate that would block generic entry in major markets.

What types of patents historically covered didanosine?

• Compound and process patents for ddI synthesis
• Tablet/capsule formulation patents (excipients, stability, dissolution profiles)
• Methods of use in HIV regimens (historical method-of-use claims)

Why does patent strength matter less for didanosine today?

• The active ingredient’s age means compound protection from the original filing era is largely expired in most jurisdictions.
• Even where formulation or process patents exist, they typically do not constrain routine manufacturing at the molecule level once licensing and design-around routes are available.

When does didanosine lose exclusivity and what are expected generic entry risks?

Featured snippet answer: Didanosine is past the period where exclusivity is the dominant commercial determinant; generic entry risk is historically low because generic availability is already entrenched.

What does “exclusivity” mean for an older NRTI like didanosine?

• Regulatory exclusivity (e.g., data exclusivity tied to new marketing authorization) is typically expired for an older API.
• Market exclusivity in practice is tied to:
  • patent-controlled formulation variants
  • label-specific combinations or dosing regimens
  • supply continuity and manufacturer capacity

How does Paragraph IV risk apply to didanosine?

• Paragraph IV incentives are driven by presence of unexpired Orange Book-listed patents for a reference-listed drug.
• For didanosine, the Orange Book gating concept is largely neutral because the drug’s core protection has aged out; any Paragraph IV activity would be uncommon outside of specific formulation strengths or packaging.

What is the Orange Book status of didanosine and which listings matter for investors?

Featured snippet answer: Orange Book relevance is limited for didanosine because active ingredient exclusivity is largely expired; any remaining listings are typically formulation-specific and do not represent broad barriers.

Which Orange Book patent listings would be material?

If present, material listings would be:

• formulation patents (controlled release, specific excipient systems)
• method-of-use patents (rare for an old molecule without newer label expansion)
• packaging or manufacturing patents

How do Orange Book listings affect generic procurement?

• Procurement risk is driven more by supply and quality system readiness than patent hurdles.
• Where patents exist, they mainly affect:
  • time-to-launch for a particular manufacturer
  • settlement leverage for branded-to-generic transition in a specific strength/dosage form

What formulations of didanosine are marketed and what delivery systems exist?

Featured snippet answer: Didanosine is primarily a conventional oral NRTI. The commercial reality is dominated by older oral dosage forms rather than modern delivery systems.

Oral dose forms and historical relevance

• Tablets/capsules in older treatment eras
• Combination regimens historically co-administered with other antiretrovirals
• Some formulations required strict administration rules relative to food or other drugs (historical label-level details that can influence adherence and clinical use)

Do formulation patents or bioavailability issues create market differentiation?

• In practice for an older NRTI, differentiation is more likely driven by:
  • supply reliability
  • stability and shelf-life
  • manufacturing consistency for bioavailability targets
• These factors affect brand survivability more than they protect market share legally.

How does didanosine compare with current HIV therapies on clinical positioning?

Featured snippet answer: Didanosine is largely displaced by newer NRTI backbones and other antiretroviral classes with better tolerability and dosing convenience.

Clinical substitution drivers

• Newer NRTIs and regimens reduce mitochondrial toxicity risk profiles seen historically with older NRTIs.
• Guidelines increasingly prioritize:
  • once-daily regimens
  • better safety monitoring practicality
  • fewer long-term toxicity signals

Where might didanosine still appear?

• Salvage contexts where options are limited by resistance or intolerance
• Regions where access constraints keep older agents in use longer than in high-income markets

What competitive landscape exists for didanosine (generics, authorized distributors, and supply)?

Featured snippet answer: Competitive pressure is primarily generic-to-generic and supplier-to-supplier on availability, pricing, and quality.

What determines commercial share for didanosine today?

• Government and payer formularies in specific countries
• Procurement contracts and tender cycles
• Number of qualified manufacturers and regulatory approvals
• Batch consistency and ability to meet demand surges

How much pricing power does a branded didanosine product have?

• Typically low. Older HIV molecules are exposed to fast generic repricing once patents and exclusivity stop constraining entry.

What market size and revenue projections are realistic for didanosine through 2030?

Featured snippet answer: Didanosine’s global market is expected to remain small relative to modern antiretroviral classes and trend downward, with volatility tied to supply and regional guideline persistence rather than growth drivers.

Market projection logic (structure, not speculation)

A credible projection for didanosine depends on:

• Continued guideline inclusion in any region (size of patient pool)
• Supply availability and discontinuations
• Generic price erosion dynamics
• Substitution to preferred backbones and fixed-dose combinations

Scenario framing for business planning

• Base case: stable-to-declining volumes as older regimens are phased out; revenue declines due to generics and volume shift.
• Downside: accelerated withdrawal by suppliers, reduced procurement, and strict pharmacovigilance-driven deprescribing.
• Upside: regional persistence of older treatment protocols or limited salvage use increases short-term demand, but price is likely constrained by low-cost generics.

Operational KPIs that best proxy didanosine demand

• procurement tender volume by country
• number of active marketing authorizations and distributors
• stockout frequency and import lead-time stability
• adverse event signal monitoring that triggers formulary removal

What litigation or regulatory actions affect didanosine commercialization?

Featured snippet answer: For older small-molecule antiretrovirals, litigation is typically infrequent at the current stage unless tied to a specific formulation strength, specific Orange Book patents, or supply disputes.

What litigation themes would matter if present?

• patent infringement tied to a specific dosage form or process
• generic label carve-out disputes
• FDA or authority quality and compliance actions affecting certain manufacturers

How would litigation impact price and access?

• Temporary supply constraints in specific geographies
• Short-term pricing stabilization for remaining suppliers
• Reallocation of procurement to alternate qualified manufacturers

Key Takeaways

• Didanosine has no meaningful current registrational development momentum; visible trial activity is mostly legacy, safety, pharmacokinetics, or observational follow-up rather than label-expanding late-stage work.
• The patent-exclusivity gating function that matters for newer drugs is largely neutral for didanosine due to age and widespread generic availability.
• Market economics are dominated by substitution into newer antiretroviral regimens, generic price erosion, and supplier availability rather than new IP or regulatory exclusivity.
• Revenue projections through 2030 are best modeled as small, structurally declining demand with limited upside and high dependence on regional protocol persistence and supply continuity.

FAQs

1. Is didanosine still used in HIV treatment guidelines today?
2. What adverse events most limit didanosine use compared with newer NRTIs?
3. Do any didanosine formulation patents still affect generic competition in major markets?
4. How does didanosine availability vary by country and tender cycles?
5. What patient populations are most likely to receive didanosine under salvage or intolerance scenarios?

References

1. FDA. Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations. U.S. Food and Drug Administration.
2. ClinicalTrials.gov. Search results for “didanosine” (ddI). U.S. National Library of Medicine.
3. WHO. WHO Model Lists of Essential Medicines (context for antiretroviral availability and historical inclusion). World Health Organization.