List of Excipients in Branded Drug PIFELTRO

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	CARNAUBA WAX	2032-08-30
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	CELLULOSE, MICROCRYSTALLINE	2032-08-30
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	CROSCARMELLOSE SODIUM	2032-08-30
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	HYPROMELLOSE	2032-08-30
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	HYPROMELLOSE ACETATE SUCCINATE 06081224	2032-08-30
Merck Sharp & Dohme LLC	PIFELTRO	doravirine	0006-3069	LACTOSE MONOHYDRATE	2032-08-30

Pifeltro Excipient Strategy and Commercial Opportunities

Last updated: August 2, 2026

Pifeltro is a 100 mg oral tablet containing doravirine, a non-nucleoside reverse transcriptase inhibitor marketed by Merck for treatment of HIV-1 infection. Its commercial formulation uses conventional tableting excipients, creating opportunities for generic developers and excipient suppliers in direct-compression processing, film coating, lactose-free alternatives, supply-chain resilience, and formulation differentiation. The principal commercial barrier is likely regulatory and patent timing rather than difficult excipient technology.

What is Pifeltro and how is it formulated?

Pifeltro contains 100 mg of doravirine per tablet. The tablet is administered once daily, with or without food, and is approved for adults with HIV-1 infection without prior or current resistance to doravirine or related agents.[1]

The US prescribing information identifies the following inactive ingredients:

Formulation component	Pifeltro excipient
Filler and compression aid	Microcrystalline cellulose
Diluent	Lactose monohydrate
Disintegrant	Croscarmellose sodium
Lubricant	Magnesium stearate
Glidant	Colloidal silicon dioxide
Film-forming system	Hypromellose, polyvinyl alcohol, polyethylene glycol
Opacifier and pigment	Titanium dioxide
Anti-tacking or coating aid	Talc
Surface polish	Carnauba wax

The formulation is a conventional immediate-release, film-coated tablet. It does not depend on an extended-release matrix, enteric coating, lipid carrier, osmotic system, or specialized delivery device.[1]

What excipient functions are commercially important?

The formulation relies on a standard combination of:

• Microcrystalline cellulose for compactibility and tablet strength.
• Lactose monohydrate for bulk and manufacturability.
• Croscarmellose sodium for rapid tablet breakup.
• Magnesium stearate for lubrication.
• Colloidal silicon dioxide for powder flow.
• A polyvinyl alcohol or hypromellose-based coating for appearance, protection, and swallowability.

This composition gives generic manufacturers multiple options to develop qualitatively and quantitatively different formulations while maintaining the same dosage form and release profile.

Which excipients protect Pifeltro’s performance?

The core formulation risk is balancing tablet strength, disintegration, dissolution, and manufacturing robustness. Doravirine is present at a relatively low drug-load fraction compared with the total tablet mass, making powder uniformity and blend segregation relevant development issues.

Lactose and microcrystalline cellulose

The lactose-microcrystalline cellulose combination is commercially efficient because it supports both dilution and compression. A generic developer could replace lactose with:

• Mannitol
• Dibasic calcium phosphate
• Pregelatinized starch
• Spray-dried lactose
• Co-processed cellulose systems
• Lactose-free cellulose-silica platforms

A lactose-free formulation could target patients with lactose intolerance, procurement policies favoring non-animal or non-lactose materials, or markets where lactose supply is less reliable. The commercial value is greatest if the alternative improves powder flow or reduces tablet weight without compromising dissolution.

Croscarmellose sodium

Croscarmellose sodium provides rapid swelling and wicking. It is a conventional choice for immediate-release tablets, but it can be replaced or combined with:

• Crospovidone
• Sodium starch glycolate
• Low-substituted hydroxypropyl cellulose
• Co-processed superdisintegrants

The main opportunity is not simply substitution. It is optimization of disintegration at lower excipient loading, which can create room for higher drug content, a smaller tablet, or improved mechanical strength.

Magnesium stearate and silica

Magnesium stearate reduces ejection force but can impair wetting and dissolution when over-lubrication occurs. Colloidal silicon dioxide improves flow but can affect blend density and powder handling.

Generic manufacturers can differentiate process performance through:

• Shorter lubrication times
• Alternative magnesium stearate grades
• Sodium stearyl fumarate
• Optimized silica levels
• Continuous blending
• Roller compaction or dry granulation
• Controlled order of addition

These changes are likely to be process-development opportunities rather than standalone product claims. They may still support manufacturing know-how, process patents, or trade-secret protection.

What formulation patents protect Pifeltro?

Pifeltro’s commercial protection must be separated into three categories:

1. Active-ingredient patents covering doravirine or its chemical class
2. Method-of-use patents covering HIV treatment
3. Formulation or manufacturing patents covering tablet composition, process conditions, or solid-state characteristics

The US FDA label establishes the marketed formulation and dosage form, but it does not identify every patent that may affect generic entry. The FDA Orange Book is the controlling source for patents submitted for listing against an approved small-molecule product.[2]

Are Pifeltro’s excipients likely to be the main patent barrier?

Probably not. The listed excipients are widely used compendial materials. A patent claim limited to lactose, microcrystalline cellulose, croscarmellose sodium, magnesium stearate, and a conventional film-coat system would face a narrower commercial moat than a claim covering doravirine itself, a specific polymorph, or a defined manufacturing process.

Potentially stronger formulation claims would require technical limitations such as:

• A specified doravirine solid form
• Defined particle-size distribution
• A narrow excipient ratio
• A dissolution profile linked to a measurable stability benefit
• Improved chemical or physical stability
• A process that controls impurity formation
• A formulation that maintains bioavailability under specific storage conditions

The practical value of such claims depends on whether a generic applicant can design around them without sacrificing bioequivalence or manufacturing efficiency.

What is the FDA regulatory status of Pifeltro?

Pifeltro was approved by the FDA on August 2, 2018, as a new molecular entity for treatment of HIV-1 infection.[3] It is an oral small-molecule product regulated through the abbreviated new drug application pathway for future generics rather than the biosimilar pathway.

Regulatory item	Pifeltro status
Active ingredient	Doravirine
Dosage form	Film-coated tablet
Strength	100 mg
Route	Oral
FDA approval	August 2, 2018
Regulatory pathway	NDA
Generic pathway	ANDA
Biosimilar pathway	Not applicable
Reference product	Pifeltro tablets

Pifeltro is also used as a component of Delstrigo, a fixed-dose combination containing doravirine, lamivudine, and tenofovir disoproxil fumarate. Excipient and formulation opportunities for Delstrigo are separate from those for Pifeltro because combination-product manufacturing introduces additional compatibility, content-uniformity, and dissolution considerations.[4]

When does Pifeltro lose exclusivity?

Pifeltro’s regulatory exclusivity began with FDA approval in 2018. A new chemical entity generally receives five years of US data exclusivity, subject to statutory exceptions. That period would have expired in 2023, meaning an ANDA could generally be submitted after the applicable NCE filing restriction ended.[5]

Patent protection can extend beyond regulatory exclusivity. Publicly reported doravirine patent terms have been associated with protection into the early 2030s, but the commercial effect depends on the specific patent, patent-term adjustment, patent-term extension, Orange Book listing, and any litigation or settlement agreement.

Protection category	Timing assessment
FDA NCE exclusivity	Generally five years from August 2018 approval
ANDA filing restriction	Generally four years for an NCE
Drug substance patents	May extend beyond regulatory exclusivity
Formulation patents	Must be assessed patent by patent
Method-of-use patents	May affect labeling and launch strategy
Pediatric exclusivity	Could add six months if granted and applicable
Patent-term extension	Must be confirmed from the relevant patent record

A generic applicant can challenge listed patents through a Paragraph IV certification. The timing of a commercial launch then depends on patent litigation, settlement terms, injunctions, regulatory approval, and any 180-day first-filer exclusivity.

What generic entry risks exist for Pifeltro?

Pifeltro is a conventional tablet, which generally reduces formulation complexity relative to long-acting injectables, modified-release products, or biologics. The primary generic-entry risks are therefore likely to involve patent scope, bioequivalence, and market size.

Paragraph IV challenge risks

A Paragraph IV applicant could challenge:

• Doravirine composition-of-matter claims
• Solid-state or polymorph claims
• Formulation claims
• Manufacturing-process claims
• Method-of-use claims

The strongest challenge opportunity would arise if a generic formulation can avoid formulation claims through excipient substitution while preserving immediate-release behavior. Because the marketed excipients are conventional, a design-around strategy using a lactose-free filler or alternate superdisintegrant is technically plausible.

Bioequivalence risk

For an immediate-release oral tablet, an ANDA applicant normally must demonstrate pharmaceutical equivalence and bioequivalence. Important development variables include:

• Assay and content uniformity
• Dissolution across relevant pH conditions
• Tablet disintegration
• Food-effect behavior
• Impurity profile
• Stability under ICH conditions
• Particle-size and blend-uniformity controls

A formulation that produces materially faster or slower dissolution could create regulatory risk even if the excipients are individually acceptable.

What excipient strategies could create commercial opportunities?

1. Lactose-free Pifeltro-compatible formulations

Replacing lactose is the clearest product-development opportunity. Candidate platforms include mannitol, microcrystalline cellulose, dibasic calcium phosphate, and co-processed excipients.

Commercial advantages may include:

• Broader patient acceptability
• Alternative supplier base
• Reduced dependence on dairy-derived materials
• Potentially improved moisture handling
• Differentiation for private-label or regional products

The formulation must maintain equivalent dissolution and tablet performance.

2. Smaller tablets

A smaller tablet could improve adherence, particularly in HIV treatment where patients may take multiple medicines. Size reduction could come from:

• Higher-density fillers
• Co-processed direct-compression materials
• Improved drug loading
• Granulation to increase bulk density
• Lower coating weight
• Optimized disintegrant efficiency

Tablet-size claims may be commercially useful but are difficult to protect broadly unless linked to a defined composition or performance parameter.

3. Moisture-robust formulations

Doravirine tablets require stability control through excipient selection, coating, packaging, and manufacturing conditions. Opportunities include:

• Low-moisture excipient grades
• Moisture-barrier film coatings
• Desiccant-compatible packaging
• High-density polyethylene bottles with improved closure systems
• Blister packaging with enhanced barrier properties
• Reduced water exposure during granulation

A moisture-robust formulation may be more valuable in tropical or high-humidity markets than in the United States or Western Europe.

4. Co-processed excipient systems

Co-processed microcrystalline cellulose-silica, mannitol-cellulose, or cellulose-starch systems can improve flow, compressibility, and content uniformity. These materials may allow manufacturers to simplify the formulation and reduce the number of raw-material suppliers.

The commercial opportunity for excipient suppliers is strongest where the co-processed material provides a measurable advantage in:

• Direct compression
• Low-dose blend uniformity
• Tablet tensile strength
• Ejection force
• Disintegration
• Scale-up consistency

5. Film-coating optimization

Pifeltro uses a conventional film-coated tablet. Coating suppliers can compete through:

• Lower coating weight
• Faster drying
• Reduced solvent or water exposure
• Improved opacity
• Better pigment dispersion
• Lower defect rates
• More robust color matching
• Titanium-dioxide-free systems in markets with formulation restrictions

The most realistic value proposition is manufacturing efficiency and supply continuity rather than clinical differentiation.

How strong is the Pifeltro patent estate?

The estate is likely strongest around doravirine itself and related pharmaceutical development assets, not the individual excipients listed in the label. A patent-strength review should score each asset against five factors:

Factor	Commercial question
Claim scope	Does the claim cover the active ingredient, formulation, process, or use?
Design-around difficulty	Can a generic substitute an excipient or process step?
Remaining term	How long does enforceable protection remain?
Orange Book relevance	Is the patent listed against Pifeltro?
Litigation history	Has the claim survived challenge or been settled?

An excipient patent has higher strategic value when it captures a necessary performance feature rather than a conventional ingredient list. Examples include a defined dissolution profile, a stable solid form, a specific particle-size range, or a manufacturing step that reduces a critical impurity.

Which companies are positioned to challenge or supply Pifeltro?

Potential generic competitors would include large ANDA manufacturers with HIV portfolios, regional generic companies, and contract development and manufacturing organizations. The most relevant suppliers are likely to come from four groups:

1. Generic drug manufacturers seeking doravirine or combination-product ANDA opportunities.
2. Excipient manufacturers supplying microcrystalline cellulose, lactose, crospovidone, croscarmellose sodium, magnesium stearate, silica, and film-coating systems.
3. CDMOs offering direct compression, dry granulation, coating, and analytical development.
4. Packaging suppliers providing high-barrier bottles and blister systems for global distribution.

A competitor does not need to copy the Pifeltro excipient profile. It needs to meet the applicable pharmaceutical-equivalence, bioequivalence, quality, and stability requirements.

What licensing and partnering opportunities exist?

Licensing opportunities are more likely to involve doravirine rights, regional commercialization, or fixed-dose combinations than the basic excipient formulation. Relevant deal structures may include:

• Regional rights for doravirine tablets
• Licensing of doravirine API supply
• Manufacturing and packaging agreements
• Technology transfer for direct-compression or coating processes
• Co-development of lactose-free or small-tablet products
• Supply agreements for critical excipients
• Alternative-source qualification for excipient continuity

Excipient suppliers can create licensing value by protecting a co-processed material, coating system, or manufacturing process that improves Pifeltro-equivalent tablet production. The opportunity is stronger when the formulation can be transferred across multiple doravirine markets or adapted to Delstrigo.

How does Pifeltro compare with competing HIV products?

Product	Active ingredients	Dosage form	Excipient opportunity
Pifeltro	Doravirine	Immediate-release tablet	Lactose replacement, direct compression, coating, moisture control
Delstrigo	Doravirine, lamivudine, tenofovir disoproxil fumarate	Fixed-dose tablet	Compatibility, multi-API content uniformity, dissolution control
Other oral antiretrovirals	Varies	Tablets or capsules	Often greater competition and broader generic experience
Long-acting HIV products	Injectable combinations	Depot or suspension	Much higher formulation and manufacturing complexity

Pifeltro is technically simpler than long-acting injectable HIV products. Its commercial opportunity lies in efficient, reliable oral-tablet manufacture and patent design-around capability.

What manufacturing and geographic barriers affect commercialization?

Geographic execution can matter as much as formulation design. A global Pifeltro-equivalent product may require:

• Excipient qualification in multiple jurisdictions
• Pharmacopoeial compliance with USP, Ph. Eur., and other standards
• Nitrosamine and elemental-impurity assessments where applicable
• Stability data for hot and humid climatic zones
• Local packaging and serialization
• Separate regulatory strategies for single-agent and combination products
• Reliable doravirine API sourcing

The most defensible manufacturing know-how may involve blend uniformity, lubrication control, coating parameters, and moisture management. These advantages are often protected through process controls and trade secrets rather than broad composition patents.

Key Takeaways

• Pifeltro is a 100 mg immediate-release, film-coated doravirine tablet.
• Its listed excipients are conventional and generally provide substantial formulation design-around flexibility.
• Lactose replacement is the clearest excipient-led commercial opportunity.
• Smaller tablets, co-processed excipients, moisture protection, and coating efficiency offer secondary opportunities.
• FDA NCE exclusivity began in 2018 and generally expired in 2023, while patent protection may extend into the early 2030s.
• Generic entry would proceed through the ANDA pathway, with Paragraph IV challenges possible against listed patents.
• Excipient patents are likely weaker than active-ingredient, solid-state, or manufacturing-process patents unless tied to a defined technical performance.
• Delstrigo creates a related but more complex opportunity because its three active ingredients create additional compatibility and dissolution constraints.
• The most valuable commercial assets are likely to be robust manufacturing processes, alternative excipient platforms, and supply-chain solutions rather than simple excipient substitution.

FAQs

Can Pifeltro be reformulated without lactose?

Yes. A generic developer could evaluate mannitol, microcrystalline cellulose, dibasic calcium phosphate, starch-based materials, or co-processed excipients. The alternative must support equivalent tablet performance, dissolution, stability, and bioequivalence.

Does Pifeltro require a biosimilar application?

No. Doravirine is a chemically synthesized small molecule. A generic version would use the ANDA pathway rather than the biosimilar pathway.

Can a generic copy Pifeltro’s excipients?

It can use the same excipients if the formulation is legally and technically appropriate. It can also substitute excipients, provided the product meets FDA requirements for pharmaceutical equivalence, bioequivalence, quality, and stability.

Are film-coating materials a major barrier to Pifeltro generic entry?

Usually not. The coating system is conventional. Coating materials can affect stability, appearance, process yield, and supply continuity, but they are less likely to create the main entry barrier than active-ingredient or formulation patents.

Is Delstrigo a larger excipient opportunity than Pifeltro?

It may be a more technically demanding opportunity because Delstrigo combines doravirine, lamivudine, and tenofovir disoproxil fumarate. That creates greater requirements for content uniformity, API compatibility, dissolution, and stability, but also raises development and regulatory costs.

References

1. U.S. Food and Drug Administration. (2024). Pifeltro (doravirine) tablets: Prescribing information. Merck Sharp & Dohme LLC.

2. U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/

3. U.S. Food and Drug Administration. (2018, August 2). FDA approves new HIV-1 treatment, Pifeltro. https://www.fda.gov/

4. U.S. Food and Drug Administration. (2024). Delstrigo (doravirine, lamivudine, and tenofovir disoproxil fumarate) tablets: Prescribing information. Merck Sharp & Dohme LLC.

5. U.S. Food and Drug Administration. (2015). New chemical entity exclusivity. In Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/development-approval-process-drugs/drug-price-competition-and-patent-term-restoration-act-hatch-waxman-amendments/abbreviated-new-drug-application-anda