United States Drug Patent 6,176,242: Claim Scope, Expiration, Enforceability, and Patent Landscape

U.S. Patent No. 6,176,242 covers therapeutic treatment of depression and manic depression using implanted brain stimulation, implanted drug infusion, or both. Its independent claims are method claims directed to a specific combination of surgical implantation, neural targeting, and operation of an implantable device. The patent is no longer an enforceable U.S. patent. Its 20-year patent term expired in 2018, subject to any applicable patent-term adjustment. It has no Orange Book listing, no Paragraph IV pathway, and no direct small-molecule or biologic exclusivity effect.

What does U.S. Patent 6,176,242 cover?

The patent covers three principal treatment architectures:

Claim group	Technology	Independent claim
Combined therapy	Electrical brain stimulation plus local drug infusion	Claim 1
Drug infusion	Implantable pump and catheter delivering drug into brain tissue	Claim 5
Electrical stimulation	Implantable electrode and signal generator stimulating brain tissue	Claim 8

The patent is therefore broader than a claim limited to deep-brain stimulation alone. Claims 5 and 8 separately protect drug infusion and electrical stimulation methods. Claim 1 covers concurrent use of both systems.

The claimed disease indications are “depression and manic depression.” The latter term corresponds broadly to bipolar disorder terminology used in older medical and patent literature.

When did U.S. Patent 6,176,242 expire?

The relevant U.S. patent timeline is:

Event	Date
Earliest priority date	June 19, 1997
U.S. nonprovisional filing	June 18, 1998
Patent issued	January 23, 2001
Nominal 20-year term from U.S. filing	June 18, 2018
Current enforceability	Expired

The patent’s term is governed principally by the 20-year term applicable to applications filed after June 8, 1995. Patent-term adjustment could have moved the expiration date, but it would not alter the commercial conclusion: the patent is expired and cannot presently block commercial practice in the United States based on the patent claims alone.[1]

The patent issued as U.S. Patent No. 6,176,242 B1. The B1 designation indicates that the patent issued without a pre-grant publication under the applicable filing and examination procedure.

How are the independent claims structured?

Claim 1: Combined electrical stimulation and drug infusion

Claim 1 requires all of the following:

One or more drugs used to treat depression or manic depression.
An implantable pump.
A catheter coupled to the pump.
A discharge portion positioned near a selected brain infusion site.
An electric signal generator.
An implantable electrode positioned near a selected brain stimulation site.
Surgical implantation of the electrode and catheter.
Operation of the signal generator.
Operation of the pump while electrical stimulation is occurring.
Infusion of a predetermined dosage into the brain tissue.

The claim is a combination claim. A method generally must satisfy both the electrical-stimulation and drug-infusion limitations to fall within its literal scope. A therapy using only an electrode would not satisfy claim 1. A therapy using only a pump and catheter would not satisfy claim 1, although it may implicate claim 5 if the remaining limitations are met.

The phrase “while the signal generator is stimulating the stimulation site” imposes a temporal relationship. Concurrent or overlapping operation is more important to claim 1 than merely using both systems at different times.

Claim 5: Drug infusion without electrical stimulation

Claim 5 is an independent drug-delivery method. It requires:

an implantable pump;
a catheter;
a discharge portion positioned adjacent to a selected infusion site in brain tissue;
surgical implantation; and
operation of the pump to deliver a predetermined drug dosage.

Claim 5 does not require an electrode or electrical signal generator. It is potentially the broadest practical claim for local intracranial drug delivery among the independent claims, although it remains limited by the claimed therapeutic purpose and the required implanted-pump configuration.

Claim 8: Electrical stimulation without drug infusion

Claim 8 is an independent electrical-stimulation method. It requires:

a signal generator;
an implantable electrode;
surgical placement of the electrode adjacent to a brain stimulation site;
coupling the electrode to the signal generator; and
operation of the signal generator to treat depression or manic depression.

Claim 8 does not require a pump, catheter, or drug. It is the principal claim directed to therapeutic brain stimulation alone.

What locations are covered by the dependent claims?

Claims 2, 3, 6, and 9 identify anatomical targets. The lists include:

anterior limb of the internal capsule;
nucleus accumbens;
head of the caudate nucleus;
cingulum fibers;
cingulate gyrus;
dorsomedial nucleus of the thalamus;
locus coeruleus;
dorsal raphe nucleus;
frontal cortex; and
thalamus.

The claim language contains drafting irregularities. “Frontal Cortex” appears more than once in claims 2, 3, 6, and 9. “Dopamie Agonist” appears to be a typographical error for “dopamine agonist.” “Locus Coeruleous” appears to be a misspelling of “locus coeruleus.”

These errors do not automatically invalidate the claims. Courts generally interpret claims in light of the specification and prosecution history. A typographical defect may be corrected if the intended meaning is not reasonably subject to dispute. The duplicate frontal-cortex entry adds no substantive limitation.

What drugs are protected by claims 4 and 7?

Claims 4 and 7 use functional pharmacological categories rather than named active ingredients. The listed categories are:

Claimed category	Examples of pharmacological class
Anesthetic	Local or regional anesthetic agents
GABA agonist	Agents increasing GABAergic activity
GABA antagonist	Agents reducing GABAergic activity
Dopamine agonist	Dopaminergic receptor agonists
Dopamine antagonist	Dopaminergic receptor antagonists
Serotonin agonist	Serotonergic receptor agonists
Serotonin antagonist	Serotonergic receptor antagonists
Glutamate agonist	Glutamatergic receptor agonists
Glutamate antagonist	Glutamatergic receptor antagonists
Adrenergic agonist	Adrenergic receptor agonists
Adrenergic antagonist	Adrenergic receptor antagonists

The claims do not identify a particular active pharmaceutical ingredient, dosage strength, formulation, release profile, or brand. Their scope turns on whether a drug falls within one of the listed pharmacological classes and is delivered using the claimed implanted system.

The claims also use “one or more drugs,” which may cover single-agent and combination therapy. A commercial formulation patent covering a specific drug, excipient, concentration, or release system would be legally distinct from the expired method claims.

What is the scope of the device limitations?

The patent does not claim a generic implantable pump or generic electrode in isolation. Its independent claims are method claims requiring use of the equipment for a specified therapeutic purpose.

Pump and catheter limitations

The drug-infusion claims require:

an implantable pump;
a catheter coupled to the pump;
a discharge portion;
placement adjacent to a selected brain infusion site; and
delivery of a predetermined dosage.

The claim language does not expressly require a particular pump architecture, reservoir size, flow rate, refill system, catheter material, or control algorithm. Those omissions create broad functional coverage, but the method remains limited to the described therapeutic use and anatomical placement.

Electrode and signal-generator limitations

The stimulation claims require:

an implantable electrode;
a proximal end connected to a signal generator;
a stimulation portion positioned near brain tissue; and
operation of the generator to stimulate the selected site.

The claims do not specify electrode polarity, waveform, pulse width, frequency, amplitude, closed-loop sensing, rechargeable power, or programming parameters. Later patents directed to waveform control, patient-specific targeting, sensing, lead design, or adaptive stimulation would generally occupy separate technical territory.

How strong is the patent estate for U.S. Patent 6,176,242?

The historical claim estate was broad in concept but vulnerable in several respects.

Strength	Assessment
Therapeutic concept	Broad combination of neural stimulation and localized drug delivery
Independent claims	Three independent method claims cover combined, infusion-only, and stimulation-only treatment
Drug coverage	Broad class-based language, but limited by delivery method and treatment purpose
Anatomical coverage	Multiple named sites, with some drafting duplication
Device coverage	Functional rather than component-specific
Validity risk	Potential prior-art and enablement issues for broad treatment concepts
Current enforceability	None in the United States because the patent term expired

Potential validity issues

A historical validity analysis would likely focus on:

prior reports of deep-brain stimulation for psychiatric disease;
prior implantable pump and catheter systems;
earlier local delivery of neuroactive agents;
written-description support for the full list of brain targets and pharmacological classes;
enablement of treating both depression and manic depression across multiple neural sites and drug classes.

The breadth of claims 5 and 8 could have created prior-art exposure because each covers a general therapeutic modality rather than a narrow device configuration or specific treatment protocol.

The patent’s current expiration eliminates the practical importance of those validity questions for ordinary U.S. commercial freedom to operate. They remain relevant to historical licensing, portfolio valuation, and interpretation of related continuation or foreign-family rights.

What is the Orange Book status of U.S. Patent 6,176,242?

U.S. Patent 6,176,242 is not an Orange Book patent.

The Orange Book lists patents submitted by applicants for approved drug products, including patents covering active ingredients, formulations, compositions, and methods of use. The subject patent is directed to a treatment method using implanted neural devices and drug delivery. It does not claim a particular FDA-approved drug product in the manner required for an Orange Book listing.[2]

Consequences include:

no Orange Book patent expiration date tied to a drug product;
no statutory Paragraph IV certification directed to this patent;
no 30-month stay based on this patent;
no Hatch-Waxman generic-entry barrier;
no direct impact on ANDA approval for a conventional oral, injectable, or other drug product.

Are there Paragraph IV challenges or generic-entry risks?

There is no conventional Paragraph IV risk associated with this patent. Paragraph IV litigation applies to patents listed in the Orange Book against an approved reference drug. U.S. Patent 6,176,242 is a device-assisted treatment patent, not an Orange Book-listed drug patent.

A generic drug manufacturer could theoretically practice a drug-infusion method only if it also used the claimed implanted pump, catheter, anatomical placement, and therapeutic purpose. The patent’s expiration removes that concern in the United States.

Generic-entry risk instead arises from other patent categories:

patents covering the active pharmaceutical ingredient;
formulation and stability patents;
controlled-release or depot-delivery patents;
catheter and implant patents;
software and programming patents;
device patents covering pump mechanics or neural electrodes;
later method-of-use patents for specific psychiatric indications.

What formulation patents are relevant to the claimed technology?

U.S. Patent 6,176,242 does not claim a specific formulation. Its drug limitations are pharmacological categories. A later formulation patent could cover:

a defined active ingredient;
a concentration range;
a sustained-release composition;
a nanoparticle or liposomal formulation;
a hydrogel or depot;
a preservative system;
a pH or osmolality range;
compatibility with an implanted catheter; or
a controlled infusion schedule.

Such patents would be separate from the expired patent and could remain enforceable even if the underlying treatment concept is no longer protected.

How does this patent compare with modern depression-treatment patents?

Technology	Typical protected subject matter	Relationship to 6,176,242
Deep-brain stimulation	Lead placement, stimulation parameters, targeting, sensing, control software	Later and narrower technical improvements may remain active
Vagus nerve stimulation	Generator, lead, dosing schedules, psychiatric indications	Separate anatomical and device estate
Transcranial magnetic stimulation	Coil structure, pulse protocols, treatment schedules	Non-implantable and outside the claimed system
Intrathecal drug delivery	Pump, catheter, refill, flow control, drug-specific use	May overlap conceptually but differs from brain-tissue infusion
Implantable infusion systems	Reservoir, valve, sensor, refill, safety controls	Device claims can remain distinct
Psychiatric drug products	Active ingredient, formulation, method of use	No direct Orange Book effect from 6,176,242

The patent is best viewed as an early platform patent for combining neuromodulation and local neuropharmacology. Modern portfolios tend to divide protection among hardware, targeting, dosing, software, biomarkers, and drug-specific treatment protocols.

What licensing deals and litigation affect the patent?

No material current licensing deal, settlement, Paragraph IV action, or active U.S. infringement litigation is identified for U.S. Patent 6,176,242 in the patent-level record cited here. The patent’s expiration makes a current enforcement campaign unlikely.

Historical ownership and assignment records should be checked in the USPTO Patent Center assignment and maintenance databases before relying on the patent for chain-of-title analysis.[3] A patent may have changed ownership even when the issuing assignee is identified in commercial databases.

What geographic coverage does the patent have?

The patent provides U.S. rights only. Any foreign counterparts would have required separate national or regional prosecution and would have separate:

claim scope;
priority treatment;
expiration dates;
maintenance requirements;
opposition or invalidity proceedings; and
enforceability status.

The U.S. expiration does not establish that corresponding European, Canadian, Japanese, or other national patents expired on the same date. Foreign-family analysis must be conducted by publication and grant number.

What generic launch scenarios remain?

The patent does not create a current U.S. generic-launch barrier. The relevant commercial scenarios are:

Scenario	Effect of U.S. 6,176,242
Conventional generic antidepressant	No meaningful effect
Generic drug used with an implantable pump	No patent barrier from this expired patent
New intracranial drug-delivery product	Review later formulation, device, and method patents
Depression DBS system	Review later electrode, targeting, software, and method patents
Combined DBS and drug infusion platform	Review active follow-on patents; 6,176,242 itself is expired
FDA device-drug combination product	Regulatory review remains separate from this patent

Key takeaways

U.S. Patent 6,176,242 covers implanted electrical stimulation, implanted brain drug infusion, and their combined use for depression and manic depression.
Claims 1, 5, and 8 are the principal independent claims.
Claim 1 requires concurrent operation of the pump and electrical stimulation.
Claim 5 covers drug infusion without an electrode.
Claim 8 covers electrical stimulation without drug infusion.
Claims 4 and 7 identify broad pharmacological classes rather than specific drugs.
The patent does not claim a specific formulation, active ingredient, pump design, electrode design, or dosing parameter.
The patent’s nominal U.S. term ended in 2018.
It is not an Orange Book patent and does not support a Paragraph IV challenge.
Current risk is concentrated in later patents covering devices, formulations, neural targeting, software, dosing, and drug-specific methods.
Foreign counterpart rights must be analyzed separately.

FAQs

Does U.S. Patent 6,176,242 cover deep-brain stimulation for depression?

Yes. Claim 8 covers electrical stimulation of selected brain tissue for treating depression or manic depression. The patent is expired in the United States.

Does the patent cover ketamine delivered directly into the brain?

The claims do not name ketamine. A ketamine-use analysis would depend on whether the drug falls within a claimed pharmacological category and whether the claimed implanted pump, catheter, anatomical site, and treatment steps were used. The U.S. patent itself is expired.

Does the patent cover an external infusion pump?

No. Claims 1 and 5 require an implantable pump. An external pump would not literally satisfy that express limitation, although other patents could apply.

Does the patent cover transcranial magnetic stimulation?

No. The claims require an implantable electrode and signal generator. Non-implantable transcranial magnetic stimulation uses a different treatment architecture.

Can a company rely only on this patent to clear a combined brain-stimulation and drug-delivery product?

No. This patent is expired, but active later patents may cover the specific pump, catheter, electrode, software, formulation, dosing regimen, targeting method, or approved therapeutic use.

References

United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term expiration provisions. https://www.uspto.gov/patents/laws/patent-term-adjustment
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
United States Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/
U.S. Patent No. 6,176,242. (2001). Method and apparatus for treating depression. United States Patent and Trademark Office.

Details for Patent: 6,176,242

Summary for Patent: 6,176,242