US Patent 9,861,595: Claim Scope, Auvelity Protection, Expiration, and Generic Entry Risk
US Patent 9,861,595 is a pharmacokinetic method patent covering the use of bupropion or specified bupropion metabolites to increase dextromethorphan exposure in extensive metabolizers. The claims are directed to sustained co-administration, defined plasma concentration thresholds, and exposure multiples measured after eight days. The patent is highly relevant to Auvelity, the dextromethorphan hydrobromide/bupropion hydrochloride product marketed by Axsome Therapeutics for major depressive disorder.
The broadest practical risk is concentrated in claims 1, 15, and 20. Claims 2 through 14, 16 through 19, and 21 through 29 add oral administration, dosage-form, dose, duration, patient-age, stereochemical, deuterated, and pharmacokinetic limitations.
Based on the patent’s earliest priority date, the nominal expiration date is August 23, 2026, subject to any applicable patent-term adjustment or other official term modification. The patent is distinct from later Auvelity patents directed to composition, formulation, and related treatment methods.
What does US Patent 9,861,595 protect?
The patent protects a method of administering dextromethorphan with bupropion or one of three named bupropion metabolites to an extensive metabolizer for at least eight consecutive days, provided that specified pharmacokinetic results are achieved.
The claimed inhibitor or enhancer may be:
- Bupropion;
- Hydroxybupropion;
- Threohydroxybupropion; or
- Erythrohydroxybupropion.
The claimed method requires treatment of a human who:
- Is an extensive metabolizer of dextromethorphan;
- Needs treatment with dextromethorphan;
- Receives the two active agents as the sole active agents administered;
- Receives the combination for at least eight consecutive days; and
- Achieves the recited Cmax, Cmin, Cavg, or exposure-multiple limitations.
This is a results-defined method patent. A competing product does not avoid the claims merely because it uses a different brand name or formulation. The relevant question is whether administration produces the claimed pharmacokinetic conditions and satisfies every limitation of an asserted claim.
How many independent inventions are claimed?
The patent contains three independent method claims.
| Independent claim |
Primary pharmacokinetic requirement |
Key additional limitations |
| Claim 1 |
Day-8 dextromethorphan Cmax of at least about 15 times the no-bupropion comparator and at least about 35 ng/mL |
Extensive metabolizer; at least eight days; sole active agents |
| Claim 15 |
Day-8 Cmin of at least about 20 ng/mL and Cmax of at least about 15 times the comparator |
Extensive metabolizer; at least eight days; sole active agents |
| Claim 20 |
Cavg of at least about 25 ng/mL and day-8 Cmax of at least about 20 times the comparator |
Cavg measured between consecutive dextromethorphan administrations |
Claims 1 and 15 overlap substantially. Claim 15 adds a minimum trough concentration, while claim 1 adds an absolute Cmax threshold. Claim 20 is narrower in its exposure-multiple requirement because it requires a 20-fold, rather than 15-fold, increase, but it adds an average-concentration requirement.
What are the key limitations in claim 1?
Claim 1 has six material limitations that define its enforcement scope.
1. Extensive metabolizer status
The patient must be an extensive metabolizer of dextromethorphan. This limitation is important because dextromethorphan is principally metabolized through CYP2D6. Patients with poor, intermediate, normal, and ultrarapid metabolizer phenotypes may produce materially different plasma profiles.
A generic or follow-on product could dispute infringement if its labeling does not identify extensive metabolizers or if clinical use does not establish that the treated patient falls within that category. That defense would be fact-dependent. The absence of a metabolizer test from a label would not necessarily eliminate induced-infringement risk if the product is promoted for use in the claimed population.
2. At least eight consecutive days
The method must be performed for at least eight consecutive days. Claims 14, 18, and 22 extend the period to 14 or 30 days.
A single dose, short-term co-administration, or treatment that stops before day eight would fall outside the independent claims as written. A product labeled for chronic administration, however, would likely create a stronger infringement case because the labeled regimen would encompass the required duration.
3. Sole active agents
The dextromethorphan and bupropion-related agent must be the sole active agents administered to the patient. This limitation narrows the claims compared with a general drug-interaction claim.
The phrase does not necessarily require that the patient take no inactive ingredients or no other non-drug substances. It targets active pharmaceutical agents. The limitation could become relevant for combination regimens that include antidepressants, antipsychotics, stimulants, or other CNS-active therapies.
4. Defined Cmax outcome
Claim 1 requires that the bupropion-related agent be administered in an amount resulting in a dextromethorphan Cmax of at least about 35 ng/mL. On day eight, the Cmax must also be at least about 15 times the Cmax produced by the same amount of dextromethorphan without the enhancer.
Claims 8 through 10 increase the absolute Cmax threshold to approximately 50, 60, or 70 ng/mL. Claim 11 increases the comparative exposure threshold to at least approximately 20 times.
5. Comparator administration
The 15-fold or 20-fold limitation is measured against administration of the same amount of dextromethorphan without bupropion or the specified metabolite. The comparator is therefore dose-matched.
This limitation creates potential disputes over:
- The comparator subject population;
- Extensive-metabolizer status;
- Food conditions;
- Sampling schedule;
- Dextromethorphan salt or formulation;
- Whether the comparison is intra-subject or inter-subject; and
- Statistical treatment of Cmax.
The comparator cannot ordinarily be selected from an unrelated population with materially different CYP2D6 characteristics without affecting the analysis.
What formulations are protected by US 9,861,595?
The patent does not principally claim a tablet composition. It claims administration methods.
Claim 2 requires oral administration. Claim 3 narrows the method to a single solid dosage form containing both active agents. That claim is particularly relevant to fixed-dose combination tablets such as Auvelity.
The patent therefore reaches at least three commercial configurations:
| Configuration |
Relevant claim exposure |
| Separate oral dextromethorphan and bupropion products |
Claim 2 and potentially claim 1 |
| Co-packaged products administered together |
Claims 1 and 2, depending on use |
| Single solid combination tablet |
Claim 3 and the broader parent method claims |
A separate-tablet strategy would not automatically avoid infringement because claim 2 covers oral co-administration and does not require a single dosage form.
The claims do not expressly require extended-release bupropion, immediate-release dextromethorphan, or a particular salt. Claim 24 of the patent family’s dependent structure, as supplied, requires an immediate-release dextromethorphan dosage form for the Cavg method. Claim 3 requires a single solid dosage form, but the independent claims do not limit all embodiments to a particular release profile.
How do the dose and ratio limitations affect infringement?
Several dependent claims target the commercial Auvelity dose range.
| Claim |
Dose or regimen limitation |
| Claim 16 |
Approximately 30 to 50 mg dextromethorphan twice daily |
| Claim 17 |
Approximately 105 to 110 mg bupropion twice daily |
| Claim 19 |
Administration at least twice daily |
| Claim 25 |
Dextromethorphan-to-bupropion weight ratio of approximately 0.4 to 0.45 |
| Claim 28 |
Approximately 44 to 46 mg dextromethorphan twice daily |
| Claim 29 |
Approximately 15 to 140 mg dextromethorphan daily |
The commercial Auvelity dosage is 45 mg dextromethorphan hydrobromide and 105 mg bupropion hydrochloride per tablet, generally administered once daily for the first three days and twice daily thereafter. The maintenance dose therefore falls within the numerical ranges in claims 16, 17, 19, 25, and 28, assuming the other pharmacokinetic limitations are met.[1]
The approximate 0.4 to 0.45 ratio in claim 25 corresponds closely to 45 mg dextromethorphan divided by 105 mg bupropion, or approximately 0.429.
What is the relevance of the stereochemical and deuterated claims?
Claims 4 and 5 cover bupropion or a listed metabolite containing an enantiomeric excess of either the S- or R-enantiomer. These claims expand the patent beyond racemic bupropion.
Claim 6 covers deuterium-modified versions of the enhancer or dextromethorphan. Claim 7 specifically addresses deuterium-modified dextromethorphan.
These claims could be relevant to later-life-cycle products using:
- Enantiomerically enriched bupropion;
- Enantiomerically enriched hydroxybupropion;
- Deuterated dextromethorphan;
- Deuterated bupropion; or
- Deuterated metabolites.
They do not remove the core requirements of the independent claims. A deuterated or stereochemically enriched product would still need to satisfy the patient, duration, sole-active-agent, and pharmacokinetic limitations.
When does US Patent 9,861,595 lose exclusivity?
The nominal patent expiration date is August 23, 2026. The date reflects the patent family’s earliest priority framework and should be distinguished from later patents that may protect Auvelity beyond that date.
| Patent protection category |
Effect on commercial exclusivity |
| US 9,861,595 |
Pharmacokinetic method claims; nominal expiry August 23, 2026 |
| Later composition patents |
May extend protection for fixed-dose dextromethorphan/bupropion products |
| Later formulation patents |
May protect release profile, dosage form, or tablet architecture |
| FDA regulatory exclusivity |
Separate from patent term and governed by approval and product status |
The first expiration of 9,861,595 does not necessarily create unrestricted generic entry. A generic applicant must address every unexpired Orange Book-listed patent and may face additional formulation or composition patents.
What is the Orange Book status of Auvelity?
Auvelity was approved by the FDA on August 18, 2022, under NDA 215256 for the treatment of major depressive disorder in adults.[1] The product contains dextromethorphan hydrobromide and bupropion hydrochloride.
US Patent 9,861,595 has been associated with the dextromethorphan/bupropion product patent estate and is relevant to Orange Book patent certification analysis. The precise Orange Book listing, use code, and current patent-term data should be read from the FDA’s current electronic Orange Book record because listings and regulatory entries can change.[2]
The FDA approval itself does not establish infringement. The commercial risk turns on the relationship between:
- The approved label;
- The Orange Book use code;
- The ANDA’s proposed label;
- The claimed pharmacokinetic outcomes; and
- Any later patents listed against the product.
What Paragraph IV challenges affect Auvelity?
A generic applicant seeking approval before expiration of a listed patent can file a Paragraph IV certification alleging that the patent is invalid, unenforceable, or not infringed. The patent holder may then file an infringement action under 35 U.S.C. § 271(e)(2), triggering the statutory 30-month stay in appropriate circumstances.[3]
For US 9,861,595, a Paragraph IV challenge would likely focus on four areas:
- Whether the claims are invalid for anticipation or obviousness based on earlier disclosure of bupropion as a CYP2D6 inhibitor;
- Whether the claimed plasma thresholds and eight-day accumulation are adequately supported and enabled;
- Whether the claims are indefinite because of terms such as “about,” “sole active agents,” or the comparator definition; and
- Whether the proposed generic label induces performance of all limitations.
A generic applicant may also argue that a label limited to noninfringing uses avoids induced infringement. That strategy becomes harder when the product’s principal or only approved use is the same dextromethorphan/bupropion combination covered by the patent.
How strong is the patent estate for this technology?
US 9,861,595 has meaningful commercial relevance but a narrower legal scope than a composition-of-matter patent.
Strengths
- It targets the core mechanism used to increase dextromethorphan exposure.
- The claims cover both bupropion and named metabolites.
- The claims capture chronic administration rather than a single pharmacokinetic experiment.
- The dose and ratio claims align closely with the marketed product.
- Claim 3 can reach a single-tablet combination.
Weaknesses
- The independent claims require extensive-metabolizer status.
- The claims depend on measured pharmacokinetic outcomes.
- The “same amount without” comparator may create evidentiary disputes.
- Several claims use approximate numerical thresholds.
- The nominal expiration date is relatively near-term compared with later Auvelity patents.
- Bupropion inhibition of CYP2D6 and dextromethorphan exposure relationships may provide prior-art arguments, depending on the asserted claim and record.
The patent is strongest against a product that uses the Auvelity-like regimen, is labeled for chronic treatment, and produces the claimed day-8 Cmax or Cmin values. It is weaker against a product designed around a materially different dose, release profile, patient population, or treatment indication, provided those differences produce a genuinely noninfringing method.
What patent litigation and settlement risks exist?
The main litigation risk is an ANDA case asserting the patent against a generic dextromethorphan/bupropion product. The likely issues would include claim construction of “extensive metabolizer,” the meaning of “sole active agents,” the day-eight measurement requirement, and the methodology for calculating the exposure multiple.
A settlement could permit a generic launch before the nominal patent expiration date while preserving later patent rights. Relevant settlement terms would include:
- Authorized-generic rights;
- A launch date;
- Restrictions tied to later patents;
- Payment or consideration;
- Covenants not to sue; and
- Treatment of formulation-specific products.
No settlement should be inferred solely from the existence of a Paragraph IV notice or patent litigation. The operative settlement agreement and court docket would control.
How does US 9,861,595 compare with later Auvelity patents?
US 9,861,595 is best viewed as a pharmacokinetic-use patent. Later patents may provide stronger protection for the commercial product itself because composition and formulation claims can apply without proving a particular plasma threshold in every patient.
| Protection type |
Typical infringement proof |
Commercial value |
| Pharmacokinetic method |
Patient use and measured exposure |
Strong where clinical data match the claims |
| Fixed-dose composition |
Product ingredients and amounts |
Stronger for the tablet itself |
| Formulation |
Release profile and dosage architecture |
Strong against substitutive formulations |
| Method of treatment |
Label, dosing, and indication |
Important for induced infringement |
| Manufacturing process |
Process evidence or discovery |
Often difficult to prove without plant information |
For Auvelity, freedom-to-operate analysis must therefore examine the full Axsome patent portfolio, FDA Orange Book entries, pending continuations, and any patent-term adjustment. Expiration of 9,861,595 alone does not resolve generic entry risk.
Key Takeaways
- US 9,861,595 covers chronic co-administration of dextromethorphan with bupropion or specified bupropion metabolites.
- The independent claims require an extensive metabolizer, at least eight consecutive days of treatment, and sole administration of the two active agents.
- Claims 1, 15, and 20 use different Cmax, Cmin, and Cavg thresholds.
- Claims 16, 17, 25, and 28 closely track the marketed 45 mg/105 mg Auvelity regimen.
- Claim 3 reaches a single solid oral dosage form.
- Claims 4 through 7 cover stereochemically enriched and deuterium-modified embodiments.
- The nominal expiration date is August 23, 2026.
- Later composition and formulation patents may create protection beyond that date.
- A Paragraph IV challenge would likely contest obviousness, enablement, definiteness, comparator methodology, and induced infringement.
- The patent is commercially important but narrower than a product-composition patent because infringement depends on patient characteristics and measured pharmacokinetic outcomes.
FAQs
Does US 9,861,595 cover bupropion administered separately from dextromethorphan?
Yes. The claims require co-administration but do not universally require a single tablet. A separate-tablet regimen can fall within the oral co-administration claims if all other limitations are satisfied.
Does the patent cover patients who are poor CYP2D6 metabolizers?
The claims expressly require an extensive metabolizer. A poor metabolizer would not satisfy that limitation, although other patents or claims could apply to a different patient population.
Can a generic avoid the patent by using a different bupropion dose?
Possibly, but dose variation alone is not sufficient. The generic must avoid every limitation of the asserted claim, including the day-eight exposure multiple and any absolute Cmax, Cmin, or Cavg threshold.
Does expiration of this patent permit immediate sale of a generic Auvelity tablet?
No. Generic entry also depends on FDA approval timing, applicable regulatory exclusivity, other unexpired Orange Book-listed patents, litigation outcomes, and any settlement restrictions.
Is a measured dextromethorphan plasma level required to prove infringement?
For the pharmacokinetic limitations, reliable evidence of the claimed exposure is likely necessary. Such evidence may come from clinical studies, product-label data, bioequivalence work, discovery testing, or other pharmacokinetic records.
References
- U.S. Food and Drug Administration. (2022). FDA approves new drug for treatment-resistant depression. https://www.fda.gov
- U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Electronic Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
- United States Congress. (2023). 35 U.S.C. § 271: Infringement of patent. https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title35-section271
- United States Patent and Trademark Office. (2018). U.S. Patent No. 9,861,595, Methods of increasing plasma levels of dextromethorphan. https://patents.google.com/patent/US9861595B2/en
