Wrist SP Biotech v. Masimo Corp.: Pulse Oximeter Patent Case Dismissed With Prejudice
Wrist SP Biotech, LLC asserted US11331015B2 — a pulse oximeter sensor patent — against medical device leader Masimo Corporation in California’s Central District. The case resolved in 161 days via stipulated dismissal, with Wrist SP granting Masimo and its customers a sweeping, irrevocable covenant not to sue on the ‘015 patent and all related family members.
Pulse Oximeter Patent Suit Against Masimo Ends in Broad Covenant Not to Sue
On 28 December 2023, Wrist SP Biotech, LLC filed a patent infringement complaint against Masimo Corporation in the United States District Court for the Central District of California (Case No. 8:23-cv-02475), asserting US11331015B2 — a patent directed to pulse oximeter sensor technology filed under application number US16/569066. Masimo, a prominent designer and manufacturer of noninvasive patient monitoring equipment including pulse oximetry devices, was identified as the accused infringer.
The case closed on 6 June 2024 — just 161 days after filing — through a stipulated dismissal filed pursuant to Fed. R. Civ. P. 41(a)(1)(A)(ii). Under the agreed terms, Wrist SP dismissed its infringement claims with prejudice, while Masimo dismissed its counterclaims without prejudice. Critically, Wrist SP granted Masimo and all its customers an unconditional, irrevocable covenant not to assert the ‘015 patent or any related continuation, divisional, continuation-in-part, reissue, reexamination, or foreign counterpart — binding on any future assignee of the patent.
The sub-six-month resolution and the unusually broad scope of the covenant not to sue suggest that settlement or a commercial resolution likely preceded the formal stipulation, though the public record does not disclose financial terms. The asymmetric dismissal structure — plaintiff’s claims extinguished with prejudice, defendant’s counterclaims preserved without prejudice — is consistent with Masimo retaining future optionality on invalidity or other defences, while Wrist SP accepted a permanent bar on re-asserting the ‘015 family.
Filing to Dismissed with Prejudice in 161 days
161 days — resolved in under 6 months, well below the median district court patent case lifecycle
Dismissed with prejudice: what the stipulated exit means for both parties
Rule 41(a)(1)(A)(ii) stipulated dismissal — what it means
A Rule 41(a)(1)(A)(ii) dismissal is a voluntary, court-approved exit agreed by all parties. Plaintiff’s claims dismissed ‘with prejudice’ means they are permanently extinguished — Wrist SP cannot refile the same infringement action. The stipulation also includes a patent family-wide covenant not to sue, extending the bar beyond the named patent to all related applications and foreign counterparts.
Permanent bar on refilingPlaintiff out with prejudice — defendant’s counterclaims survive
The dismissal is deliberately asymmetric: Wrist SP’s infringement claims are gone permanently, but Masimo’s counterclaims were dismissed without prejudice, meaning Masimo retains the ability to refile them in a future proceeding. This structure is commercially significant — it suggests Masimo preserved invalidity or other defences as leverage, consistent with a negotiated resolution favouring the defendant.
Masimo retains future optionalityBroad, irrevocable covenant shields Masimo and its customers
The covenant not to sue is unusually broad: it covers not just Masimo but all Masimo customers, extends to the entire ‘015 patent family (continuations, divisionals, CIPs, reissues, reexaminations, and foreign counterparts), and binds any future assignee of the ‘015 patent. This effectively neutralises the entire patent family as a commercial threat to Masimo’s pulse oximetry supply chain.
Family-wide IP shield for MasimoNo fee award — each party bears its own litigation costs
The stipulation specifies that each party bears its own expenses, costs, and attorneys’ fees. The absence of a fee-shifting award under 35 U.S.C. § 285 is typical in early-resolved patent disputes and suggests neither party sought to characterise the case as ‘exceptional.’ For Wrist SP, absorbing its own costs while granting a permanent covenant is consistent with a resolution that prioritised exit over further litigation investment.
No § 285 fee awardFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Wrist SP Biotech, LLC | Company | Biotech patent assertion entity — holder of US11331015B2 (pulse oximeter sensor)Search in Eureka ↗ |
| Defendant | Masimo, Corp. | Company | Masimo Corp. — leading noninvasive patient monitoring and pulse oximetry device manufacturerSearch in Eureka ↗ |
| Plaintiff counsel | Joseph J. Zito | Attorney | Counsel for Wrist SP Biotech, LLCSearch in Eureka ↗ |
| Plaintiff counsel | William P. Ramey , III | Attorney | Counsel for Wrist SP Biotech, LLCSearch in Eureka ↗ |
| Plaintiff law firm | Dnl Zito Castellano | Law Firm | Representing Wrist SP Biotech, LLCSearch in Eureka ↗ |
| Plaintiff law firm | Ramey LLP | Law Firm | Representing Wrist SP Biotech, LLCSearch in Eureka ↗ |
| Defendant counsel | Irfan Ahmed Lateef | Attorney | Counsel for Masimo, Corp.Search in Eureka ↗ |
| Defendant law firm | Knobbe Martens Olson & Bear, LLP | Law Firm | Representing Masimo, Corp.Search in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | California Central District CourtSearch in Eureka ↗ |
Official order — verbatim text
The stipulation’s precise language creates a legally tiered outcome: Wrist SP’s claims are extinguished with prejudice under Rule 41(a)(1)(A)(ii), while Masimo’s counterclaims exit without prejudice. The covenant not to sue — expressly binding on successors and assigns and covering the entire ‘015 patent family — goes beyond a standard dismissal, functioning as a contractual licence defence. The asymmetric structure suggests the parties negotiated carefully to protect Masimo’s future litigation optionality while giving Wrist SP a clean exit.
US11331015B2 — Pulse Oximeter Sensor Technology
US11331015B2, filed under application number US16/569066, protects pulse oximeter sensor technology — a category of noninvasive biosensors that measure blood oxygen saturation (SpO2) and related physiological parameters via photoplethysmography (PPG). Pulse oximetry is a foundational technology in clinical patient monitoring, consumer health wearables, and remote patient monitoring platforms. The patent’s issuance reflects continued innovation activity in sensor design, signal processing, and miniaturisation for wrist-worn and bedside monitoring form factors.
In a market where Masimo holds significant patent depth — including its own extensive SpO2 and Signal Extraction Technology (SET) portfolio — the assertion of an outside patent family against a dominant player is commercially noteworthy. The ‘015 patent and its continuation family represent potential blocking or design-around risk for any manufacturer of pulse oximeter sensors, including OEM suppliers, consumer wearable brands, and remote monitoring platform developers. The broad covenant granted to Masimo and its customers significantly narrows the enforcement footprint of this family going forward.
Should your team run an FTO against US11331015B2?
Any company developing, manufacturing, or commercialising pulse oximeter sensors — including SpO2 wearables, PPG-based fitness trackers, clinical bedside monitors, or remote patient monitoring devices — should treat US11331015B2 and its continuation family as a live FTO concern. The covenant granted to Masimo and its customers does not extend to independent manufacturers or new market entrants. The patent family’s continuation applications may broaden claim scope, and the public record from this case provides no invalidity findings that could be relied upon defensively.
PatSnap Eureka’s FTO Search Agent enables R&D and IP teams to map the full ‘015 continuation family, identify claim limitations relevant to specific sensor architectures, and benchmark against prior art cited during prosecution. Eureka’s landscape tools can surface related PAE-held SpO2 patents that may present parallel assertion risk — enabling proactive clearance strategy before product launch rather than reactive litigation response.
Run a freedom-to-operate analysis on US11331015B2 to assess your product’s exposure
Run FTO in Eureka →Similar Pulse Oximetry and Wearable Biosensor Patent Cases
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What this case signals for the pulse oximetry IP landscape
A fast dismissal with a sweeping covenant not to sue carries implications well beyond this single dispute for the pulse oximetry and wearable biosensor sector.
Broad covenant not to sue effectively de-risks the ‘015 family for Masimo globally
The stipulation’s covenant covers foreign counterparts and binds future assignees, meaning even if the ‘015 patent changes hands, Masimo’s commercial position is protected. Competitors and OEM suppliers to Masimo should note this shield does not extend to them unless they qualify as a ‘Masimo customer’ under the agreement’s terms.
Sub-six-month resolution suggests pre-trial leverage — not substantive merits ruling
No claim construction, no invalidity ruling, and no infringement finding entered the public record. The rapid exit is consistent with Masimo deploying prior art or IPR threat as early settlement leverage. Third parties cannot draw any conclusion about the ‘015 patent’s validity or claim scope from this outcome alone.
Wrist v Masimo — key questions answered
The case was dismissed with prejudice as to Wrist SP Biotech’s patent infringement claims and without prejudice as to Masimo’s counterclaims, via a Rule 41(a)(1)(A)(ii) stipulated dismissal filed on 6 June 2024. Wrist SP also granted Masimo an irrevocable covenant not to sue on US11331015B2 and its entire patent family.
The covenant covers Masimo Corporation and all its customers, and extends to US11331015B2 plus all reissues, reexaminations, continuations, continuations-in-part, divisionals, pending applications, and foreign counterparts claiming priority to the ‘015 patent. It is unconditional, irrevocable, and binding on any future successor or assignee of the patent.
Wrist SP Biotech asserted US11331015B2 (application no. US16/569066), a patent directed to pulse oximeter sensor technology used in noninvasive physiological monitoring. The accused product category was pulse oximeter sensors — a core product line for Masimo.
The asymmetric dismissal structure reflects a negotiated outcome. Dismissal with prejudice permanently bars Wrist SP from refiling its infringement claims. Masimo’s counterclaims exiting without prejudice preserves Masimo’s ability to refile — for example, in an IPR or declaratory judgment — if future circumstances warrant. This structure is consistent with Masimo retaining strategic leverage over the ‘015 patent’s validity.
The covenant not to sue protects Masimo and its direct customers but does not extend to independent manufacturers or new market entrants. The ‘015 patent family remains potentially enforceable against third parties. No invalidity finding entered the public record, so competitors cannot rely on this case as precedent for patent invalidity. An independent FTO analysis against the full ‘015 continuation family is advisable for any company active in pulse oximetry or PPG-based wearable sensing.
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