List of Excipients in Branded Drug TYBOST

Company	Tradename	Ingredient	NDC	Excipient	Potential Generic Entry
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	CELLULOSE, MICROCRYSTALLINE	2028-06-20
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	CROSCARMELLOSE SODIUM	2028-06-20
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	FD&C YELLOW NO. 6	2028-06-20
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	FERRIC OXIDE YELLOW	2028-06-20
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	MAGNESIUM STEARATE	2028-06-20
Gilead Sciences Inc	TYBOST	cobicistat	61958-1401	POLYETHYLENE GLYCOL 3350	2028-06-20

Tybost Excipient Strategy and Commercial Opportunities for Cobicistat

Last updated: August 9, 2026

Tybost is Gilead Sciences' 150 mg cobicistat tablet, used as a pharmacokinetic enhancer with atazanavir or darunavir in adults with HIV-1 infection. Its commercial value depends less on the standalone tablet than on cobicistat-containing fixed-dose combinations, including Genvoya, Stribild, and Symtuza. The excipient strategy is conventional for an immediate-release film-coated tablet, creating opportunities in generic supply, excipient substitution, fixed-dose combination development, and manufacturing-cost reduction.

What is Tybost and how does its formulation work?

Tybost contains cobicistat, a mechanism-based CYP3A inhibitor that increases systemic exposure to co-administered protease inhibitors. It has no independent antiretroviral activity and is administered at 150 mg once daily with food when used with atazanavir or darunavir.[1]

Product	Active pharmaceutical ingredient	Strength	Dosage form	Manufacturer	Primary role
Tybost	Cobicistat	150 mg	Film-coated tablet	Gilead Sciences	Pharmacokinetic enhancer
Evotaz	Atazanavir/cobicistat	300 mg/150 mg	Film-coated tablet	Bristol Myers Squibb/Gilead heritage	HIV treatment
Prezcobix	Darunavir/cobicistat	800 mg/150 mg	Film-coated tablet	Janssen/Gilead heritage	HIV treatment
Genvoya	Elvitegravir/cobicistat/emtricitabine/TAF	150/150/200/10 mg	Film-coated tablet	Gilead Sciences	Complete HIV regimen
Stribild	Elvitegravir/cobicistat/emtricitabine/TDF	150/150/200/300 mg	Film-coated tablet	Gilead Sciences	Complete HIV regimen
Symtuza	Darunavir/cobicistat/emtricitabine/TAF	800/150/200/10 mg	Film-coated tablet	Janssen/Gilead Sciences	Complete HIV regimen

The standalone Tybost product is an immediate-release oral tablet. Its formulation objective is high dose uniformity, rapid disintegration, adequate dissolution, coating robustness, and stable performance under routine storage conditions.

What excipients are used in Tybost tablets?

The U.S. prescribing information identifies a conventional excipient platform for Tybost. The inactive ingredients include lactose monohydrate, microcrystalline cellulose, croscarmellose sodium, magnesium stearate, colloidal silicon dioxide, polyvinyl alcohol, sodium lauryl sulfate, talc, titanium dioxide, and FD&C Blue No. 2 aluminum lake.[1]

Excipient	Likely formulation function	Commercial relevance
Lactose monohydrate	Diluent and compactibility aid	Widely available; cost-effective but relevant to lactose-intolerance labeling
Microcrystalline cellulose	Diluent, dry binder, compression aid	Important for tablet hardness and manufacturability
Croscarmellose sodium	Superdisintegrant	Supports rapid tablet breakup and dissolution
Magnesium stearate	Lubricant	Can affect ejection force, tensile strength, and dissolution if over-lubricated
Colloidal silicon dioxide	Glidant and moisture-control aid	Improves powder flow and blend uniformity
Polyvinyl alcohol	Film-coating polymer	Supports coating integrity and appearance
Sodium lauryl sulfate	Wetting agent and surfactant	Can improve wetting of a relatively lipophilic active
Talc	Coating aid and anti-tacking agent	Supports coating process efficiency
Titanium dioxide	Opacifier and colorant	Used for appearance and light protection
FD&C Blue No. 2 aluminum lake	Colorant	Product identification and brand appearance

The public label identifies composition but does not disclose quantitative excipient levels. Those levels, together with particle size, grade, water content, and manufacturing process parameters, are central to any generic formulation strategy.

How does cobicistat’s chemistry affect excipient selection?

Cobicistat is a relatively complex, lipophilic small molecule with low aqueous solubility. Its formulation must balance solubility enhancement against tablet manufacturability and stability. The presence of sodium lauryl sulfate is commercially relevant because it indicates a deliberate wetting strategy rather than reliance only on particle-size reduction.

A generic developer would likely evaluate four formulation risks:

1. Dissolution sensitivity to surfactant concentration.
2. Lubrication sensitivity from magnesium stearate.
3. Blend uniformity at a relatively low active load.
4. Solid-state and chemical stability under humidity and accelerated conditions.

Croscarmellose sodium and microcrystalline cellulose provide a standard direct-compression or dry-granulation platform. Lactose improves bulk and compaction economics. Colloidal silicon dioxide supports powder flow, which can be important if the active has poor flow or electrostatic behavior.

The formulation is commercially attractive because it does not depend on a specialized lipid system, osmotic delivery technology, enteric coating, or complex nanocarrier. The core excipient system is broadly available from multinational and regional suppliers.

What formulation patents protect Tybost and cobicistat products?

Cobicistat protection has historically included compound, formulation, combination, and use-related intellectual property. The relevant estate is broader than the Tybost tablet itself because cobicistat is incorporated into several fixed-dose antiretroviral products.

Protection category	Relevance to Tybost
Cobicistat compound patents	Protect the active molecule and may have provided the earliest exclusivity
Pharmaceutical composition patents	May cover cobicistat compositions with excipients or specific dosage forms
Pharmacokinetic-use patents	Cover administration of cobicistat to enhance exposure of CYP3A substrates
Combination patents	Relevant to cobicistat with darunavir, atazanavir, elvitegravir, emtricitabine, TDF, or TAF
Fixed-dose formulation patents	More important to Genvoya, Stribild, Prezcobix, and Symtuza than to standalone Tybost
Manufacturing patents	May cover crystalline forms, intermediates, purification, or process conditions

A commercial diligence review should distinguish the standalone Tybost tablet from combination products. A formulation patent covering a four-drug regimen does not necessarily block a generic cobicistat tablet, while a cobicistat composition or process patent may affect both standalone and combination products.

Public FDA labeling and Drugs@FDA records establish the approved formulation and regulatory history, but they do not provide a complete freedom-to-operate opinion. Patent expiration analysis should be performed against the current Orange Book, U.S. Patent and Trademark Office records, international registers, and any relevant litigation docket.[2,3]

When does Tybost lose exclusivity?

Tybost received FDA approval in 2014. The product’s five-year new chemical entity exclusivity period expired in 2019. That period prevented submission of an ANDA referencing cobicistat as the listed drug during the statutory exclusivity window, subject to the applicable filing rules.[4]

Patent exclusivity is separate from FDA regulatory exclusivity. For Tybost, the practical generic-entry date depends on:

• The expiration and enforceability of listed patents.
• Any patent-term extension or pediatric exclusivity.
• The scope of a generic applicant’s Paragraph IV certification.
• Whether FDA grants a 180-day first-filer exclusivity period.
• Whether the generic launches with a carve-out for protected methods of use.
• Whether Gilead or another patent owner brings Hatch-Waxman litigation.

Tybost’s commercial protection is also affected by the fact that its largest economic role is as a component of combination products. Even if a standalone cobicistat tablet becomes subject to generic competition, a generic manufacturer may still face separate patents and regulatory barriers for fixed-dose products containing darunavir, TAF, emtricitabine, or elvitegravir.

What is the Orange Book status of Tybost?

Tybost is an FDA-approved small-molecule product and is eligible for ANDA referencing under the Hatch-Waxman framework. The FDA Orange Book should be checked for current listed patents, use codes, and exclusivity entries because the listing status can change through patent delisting, expiration, correction, or regulatory updates.[2]

The main Orange Book questions for a generic applicant are:

Issue	Commercial effect
Listed composition patent	May require Paragraph IV challenge or delayed launch
Method-of-use patent	May permit a Section viii carve-out if the labeling can omit the protected use
No remaining listed patent	May support earlier ANDA approval, subject to other barriers
First Paragraph IV filer	May receive 180-day generic exclusivity
Combination-product patents	Can delay or limit fixed-dose combination entry
Product-specific labeling	May affect substitutability and physician adoption

A generic cobicistat applicant would generally evaluate a 505(j) ANDA rather than a 505(b)(2) application because the reference product is an approved small-molecule tablet with an established route and dosage form. A 505(b)(2) strategy could become relevant if the applicant pursues a materially different formulation, strength, dosage form, or clinical use.

Which companies could challenge Tybost?

Potential challengers include large generic manufacturers with HIV portfolios, specialist antiretroviral companies, and vertically integrated firms that already market products in emerging markets. Likely commercial participants include companies such as Teva Pharmaceutical Industries, Viatris, Sandoz, Sun Pharmaceutical Industries, Cipla, Aurobindo Pharma, Dr. Reddy’s Laboratories, and Lupin, although participation depends on patent status, market size, and procurement economics.

A challenger would usually select one of three approaches:

Paragraph IV challenge

The applicant asserts that listed patents are invalid, unenforceable, or not infringed. This route creates litigation risk but can deliver an early-entry position and possible 180-day exclusivity.

Section viii labeling carve-out

The applicant removes a patented method of use from its label. This strategy is more useful where the patent covers a narrow indication or dosing use and the remaining approved uses support commercial sales.

Post-patent ANDA entry

The applicant avoids litigation and launches after all relevant patents and exclusivities expire. This reduces legal cost but sacrifices first-mover advantage.

What generic entry risks exist for Tybost?

The principal entry risk is not the physical replication of the excipient system. It is the interaction between cobicistat’s role in several protected combination products and the regulatory requirement to show pharmaceutical equivalence and bioequivalence.

Key technical risks include:

• Dissolution failure caused by replacement of sodium lauryl sulfate.
• Tablet hardness or friability changes after altering lactose grade.
• Blend segregation from different particle-size distributions.
• Slower disintegration after changing lubricant concentration.
• Coating defects following replacement of the polyvinyl alcohol system.
• Stability changes caused by water activity or excipient peroxide content.
• Labeling constraints for use with atazanavir or darunavir.

The most defensible generic strategy is often a close qualitative and quantitative composition, supported by comparative dissolution and stability data. Excipient substitution can reduce cost, but it increases the risk of a formulation-development delay or additional regulatory questions.

What excipient commercial opportunities exist for Tybost?

Direct excipient supply

Tybost uses high-volume excipients with multiple qualified suppliers. Commercial opportunities exist for suppliers that can provide:

• Consistent pharmaceutical-grade lactose and microcrystalline cellulose.
• Low-peroxide or low-moisture grades for stability-sensitive formulations.
• High-purity croscarmellose sodium.
• Controlled-particle-size colloidal silicon dioxide.
• Film-coating premixes containing polyvinyl alcohol, talc, titanium dioxide, and colorant.
• Sodium lauryl sulfate with controlled impurity and particle-size profiles.

Supplier qualification is a meaningful barrier. A change in excipient source may require comparability work, process validation, stability data, and regulatory reporting.

Excipient substitution

Potential substitutions include mannitol or dibasic calcium phosphate for lactose, crospovidone or sodium starch glycolate for croscarmellose sodium, and alternate coating polymers for polyvinyl alcohol. These substitutions can support lactose-free positioning, supply continuity, or improved compression.

The commercial case is strongest when the substitution solves a defined problem:

Objective	Candidate strategy
Reduce lactose exposure	Replace lactose with mannitol or selected cellulose-based diluent
Improve flow	Optimize colloidal silicon dioxide grade or concentration
Accelerate dissolution	Screen alternate superdisintegrants and wetting agents
Reduce coating cost	Use a validated premix or alternate polymer system
Improve supply security	Dual-source critical excipients
Improve tablet robustness	Adjust cellulose-to-diluent ratio and coating weight

A substitution that materially changes dissolution may require a new bioequivalence package or additional comparative testing. The lowest-risk commercial route is usually a source change within the same excipient compendial category.

Fixed-dose combination opportunities

The larger opportunity may be cobicistat-containing combination products rather than standalone Tybost. Cobicistat is a platform enhancer in products combining it with:

• Darunavir.
• Atazanavir.
• Elvitegravir.
• Emtricitabine.
• Tenofovir alafenamide.

Combination products can reduce pill burden and support procurement contracts. They also create more complex formulation and patent issues. A manufacturer may seek to develop an alternative fixed-dose product after key active-ingredient patents expire, but the excipient system must accommodate different dose loads, pH sensitivities, dissolution profiles, and compression characteristics.

Regional and low-cost markets

Cobicistat-based products have commercial potential in markets where HIV treatment programs are shifting from older ritonavir-boosted regimens. The opportunity is strongest where procurement systems value once-daily tablets and where access to TAF-based combinations is expanding.

Regional manufacturers can compete through:

• WHO prequalification or stringent-regulatory-authority approval.
• Government tenders.
• Local manufacturing incentives.
• Dual sourcing of active ingredients and excipients.
• Simplified film-coating systems.
• Combination products targeted to national treatment guidelines.

Manufacturing scale matters. The active ingredient is only one part of total cost. Film coating, analytical testing, stability storage, packaging, and regulatory maintenance can represent a substantial share of the finished-product cost in lower-price markets.

How strong is the Tybost patent estate?

The estate is stronger at the portfolio level than at the standalone-excipient level. Conventional excipients are generally difficult to protect as composition innovations unless they are tied to a specific formulation parameter, performance profile, or manufacturing process.

Estate element	Relative strategic importance
Core cobicistat composition claims	High, where still enforceable
Fixed-dose combination claims	High for combination-product entry
Specific crystalline or solid-state claims	Potentially high if commercially relevant
Excipient-only formulation claims	Moderate and fact-specific
Manufacturing-process claims	Moderate to high if difficult to design around
Method-of-use claims	Relevant to label strategy and carve-outs
Trade secrets and know-how	Important for scale-up and process control

A generic developer should not assume that an apparently simple tablet has a simple freedom-to-operate profile. The commercial risk is distributed across active-ingredient patents, combination patents, process patents, regulatory exclusivity, and contracting arrangements.

What litigation and settlement issues affect Tybost?

Tybost-related litigation must be analyzed separately from litigation involving Genvoya, Stribild, Prezcobix, and Symtuza. A patent dispute concerning one combination may not determine the launch date for standalone cobicistat.

Relevant litigation questions include:

• Whether an ANDA applicant made a Paragraph IV certification.
• Whether the patent owner filed suit within 45 days.
• Whether a 30-month stay delayed approval.
• Whether the case ended through invalidity, noninfringement, settlement, or dismissal.
• Whether a settlement includes a licensed entry date.
• Whether the agreement was reviewed under the FTC's pharmaceutical patent-settlement program.

A settlement may permit an authorized generic or licensed generic launch before patent expiration. Its economic effect depends on the agreed date, supply terms, market allocation provisions, and whether the settlement covers standalone cobicistat, combination products, or both.

What is the FDA regulatory status of Tybost?

Tybost is FDA-approved as a pharmacokinetic enhancer for use with atazanavir or darunavir in adults with HIV-1 infection. It is not approved as a standalone antiretroviral treatment.[1]

The label carries clinically important interaction and renal-monitoring considerations because cobicistat inhibits CYP3A and can increase serum creatinine by inhibiting tubular secretion without necessarily reducing true glomerular filtration. These properties affect prescribing, drug-interaction management, and the labeling strategy for any generic product.[1]

A generic applicant must match the reference product’s strength, route, dosage form, and labeling requirements, subject to permitted labeling differences. Excipients that create clinically relevant warnings, allergen concerns, or incompatibilities could complicate approval.

How does Tybost compare with ritonavir as a pharmacokinetic enhancer?

Attribute	Cobicistat/Tybost	Ritonavir
Primary commercial role	Pharmacokinetic enhancer	Antiretroviral and pharmacokinetic enhancer
CYP3A inhibition	Strong	Strong
Independent HIV activity	No	Yes, but generally not used at booster doses for primary antiviral activity
Formulation use	Integrated into newer fixed-dose products	Used widely in boosted protease-inhibitor regimens
Excipient opportunity	Newer tablet and combination products	More mature generic supply base
Differentiation	Modern fixed-dose combinations and TAF products	Broad availability and lower-cost competition

Cobicistat’s commercial advantage is its integration into newer once-daily combination products. Ritonavir retains a cost and supply advantage in many markets. The choice affects formulation demand, procurement pricing, and the value of specialized combination-product intellectual property.

What revenue exposure does Tybost create for Gilead?

Standalone Tybost revenue is less important than revenue from cobicistat-containing combination products. A generic standalone booster could have limited impact if physicians and formularies primarily use complete combination regimens. The greater exposure would arise from generic or licensed competition to Genvoya, Prezcobix, Symtuza, or other cobicistat-containing products.

Commercial exposure should be modeled across three layers:

1. Standalone Tybost sales.
2. Cobicistat-containing combination sales.
3. Portfolio effects on HIV treatment guidelines and formulary positioning.

The highest-value products generally have stronger formulation and combination-product barriers than the standalone booster. A successful generic could therefore enter the standalone market without immediately replicating the full commercial value of Gilead's integrated regimen portfolio.

Key Takeaways

• Tybost is a 150 mg cobicistat immediate-release film-coated tablet.
• Its excipient system is conventional and includes lactose, microcrystalline cellulose, croscarmellose sodium, magnesium stearate, colloidal silicon dioxide, sodium lauryl sulfate, and a polyvinyl alcohol-based coating system.[1]
• The main formulation-development challenge is controlling dissolution, wetting, blend uniformity, lubrication, and stability.
• The strongest commercial opportunities are generic cobicistat supply, excipient dual sourcing, lactose-free reformulation, and cobicistat-containing fixed-dose combinations.
• Tybost’s five-year FDA new chemical entity exclusivity expired in 2019, but patent-based entry timing depends on the current Orange Book and related patent records.[2,4]
• Biosimilar risk does not apply because cobicistat is a small molecule. The relevant competition is ANDA-based generic entry.
• Combination-product patents may remain commercially more important than standalone Tybost formulation patents.
• Generic manufacturers should prioritize a close formulation match unless a clear commercial benefit justifies excipient substitution.

FAQs

Can a generic manufacturer replace lactose in Tybost?

Yes. A generic developer can evaluate mannitol, microcrystalline cellulose, dibasic calcium phosphate, or another suitable diluent. The replacement must preserve tablet performance, dissolution, stability, and bioequivalence.

Does sodium lauryl sulfate create a formulation barrier for cobicistat?

It can. Removing or materially reducing the surfactant may slow wetting and dissolution because cobicistat has limited aqueous solubility. The impact must be assessed through comparative dissolution and bioequivalence testing.

Is a cobicistat generic automatically substitutable for Tybost?

An approved ANDA may be therapeutically equivalent if FDA assigns the appropriate therapeutic-equivalence rating. Substitution also depends on state pharmacy law, product labeling, and whether the product is used in the same approved combination context.

Are Tybost excipients protected by patent?

Individual conventional excipients generally are not exclusive to Tybost. Patent risk may arise from a claimed combination, concentration range, dissolution profile, solid-state form, or manufacturing process rather than from the presence of lactose or magnesium stearate alone.

Does biosimilar competition affect Tybost?

No. Cobicistat is a chemically synthesized small molecule. Competition follows the generic-drug pathway, primarily through ANDAs, Paragraph IV challenges, Section viii labeling strategies, and post-patent entry.

References

1. U.S. Food and Drug Administration. (2023). Tybost (cobicistat) tablets: Prescribing information. Gilead Sciences, Inc.

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. Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/

4. U.S. Food and Drug Administration. (2024). Small business and industry assistance: Regulatory exclusivity. https://www.fda.gov/drugs/development-resources/regulatory-exclusivity-drug-products